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Applied Surface Science (v.264, #)

Editorial Board (pp. ii).

Hybrid structure for efficiency enhancement of photodetectors by M. Malekmohammad; M. Soltanolkotabi; R. Asadi; M.H. Naderi; A. Erfanian; M. Zahedinejad; S. Bagheri; M. Khaje (pp. 1-6).

► We combined photonic crystal (PC) and nonporous structure in silicon (Si). ► Reflection is reduced drastically in broad spectral range by this structure. ► The obtained reflectance was about 3% across a spectral range of 400–2000nm. ► The absorption was increased up to 96% across a spectral range of 400–2000nm.A nanoporous tapered silicon (Si) photonic crystal (PC) is realized. The PCs with this structure, which may be called hybrid PC-porous can significantly reduce the surface reflection over the broad wavelength range of 400–2000nm. Moreover, the absorption enhances in this structure significantly. The PCs are fabricated by interference lithography and then nanoporous structure is applied on it using metal assisted chemical etching. The measured reflectance and absorption across a spectral range of 400–2000nm are, approximately 3% and 96%, respectively. The improvement on the reflectance and absorption are about 90% and 70% compared to bare Si respectively; which is promising in the utilization of this structure for various applications.

Keywords: Photonic crystal; Porous Si; Solar cells; Interference lithography; Photodetectors

Influence of annealing atmosphere on room temperature ferromagnetism of Mn-doped ZnO nanoparticles by Q.Q. Gao; Q.X. Yu; K. Yuan; X.N. Fu; B. Chen; C.X. Zhu; H. Zhu (pp. 7-10).

► Zn_0.92Mn_0.08O nanoparticles were synthesized by co-precipitation technique, and annealed in H₂, CO, Ar and O₂, respectively. ► Room temperature ferromagnetism was found in sample annealed in H₂ and CO, respectively. ► The higher the carrier concentration, the larger the shift to the high energy direction in the optical absorption spectra. ► Singly ionized oxygen vacancies play an important role in the origin of ferromagnetism. ► We decomposed visible emission peaks into the green emission band and yellow emission band by Gaussian fitting.Zn_0.92Mn_0.08O nanoparticles were synthesized by co-precipitation technique, and annealed in H₂, CO, Ar and O₂, respectively. Room temperature ferromagnetism was found in samples annealed in H₂ and CO, respectively. The absorption spectra and Raman spectra of the samples reveal that a high concentration of oxygen vacancies appears in CO-annealed and H₂-annealed Zn_0.92Mn_0.08O nanoparticles. By Gaussian fitting PL spectra of the samples, a broader green–yellow emission band decomposed into the green emission band and yellow emission band, providing the evidence that singly ionized oxygen vacancies may play an important role in the origin of room temperature ferromagnetism. The exchange interaction between the donor electron trapped by the singly ionized oxygen vacancy and surrounding Mn ions is responsible for ferromagnetism of diluted magnetic semiconductors at room temperature.

Keywords: Nanoparticles; Ferromagnetism; Carrier concentration; Oxygen vacancy

Polycrystalline silicon thin films by aluminum induced crystallization of amorphous silicon by T. Wang; H. Yan; M. Zhang; X. Song; Q. Pan; T. He; Z. Hu; H. Jia; Y. Mai (pp. 11-16).

► A new way to calculate crystalline fraction is proposed to evaluate crystallization process. ► Grain size of AIC polycrystalline film can be varied with temperature. ► AIC process is derived from region crystallization and a model was introduced, which identified previous reports.Polycrystalline silicon (Poly-Si) thin films were successfully fabricated on soda-lime glass substrate by aluminum induced crystallization (AIC) process. In order to analyze non-uniform film by AIC, a new method to evaluate the poly-Si thin film average crystalline volume fraction is proposed, based on the optical microscope and Raman spectroscopy results. This method can obtain more accurate crystallization fraction than the common way. X-ray diffraction results showed that the films are strongly (111) orientated. A new region crystallization pattern in AIC was also proposed.

Keywords: Polycrystalline silicon thin film; Aluminum induced crystallization; Growth model

Low temperature method for synthesis of ZnS quantum dots and its luminescence characterization studies by K. Senthilkumar; T. Kalaivani; S. Kanagesan; V. Balasubramanian (pp. 17-20).

► We prepared zinc sulfide (ZnS) quantum dots of sizes 2.68–4.8nm. ► It is embedded on polyvinyl alcohol (PVA) matrix, have been synthesized at 70°C by wet chemical method. ► Optical absorption spectra showed strong blue shift, which is an indication of strong quantum confinement. ► ZnS quantum dots exhibit strong quantum confinement effect as the optical band gap increases significantly, from 3.96eV to 4.06eV, compared to bulk value 3.68eV.Zinc Sulfide (ZnS) quantum dots of sizes 2.68–4.8nm, embedded on polyvinyl alcohol (PVA) matrix, have been synthesized at 70°C by wet chemical method. X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), UV–vis spectroscopy and photoluminescence (PL) Spectroscopy has been adopted for sample characterization. Optical absorption spectra showed strong blue shift, which is an indication of strong quantum confinement. Photoluminescence spectra of the sample have been recorded at room temperature and observed two peaks centred around 415nm and 440nm. We have assigned the first peak due to band gap transitions while the later due to sulfur vacancy in the sample.

Keywords: ZnS quantum dots; Blue shift; Semiconductors; HRTEM

Low temperature SiN_x:H films deposited by inductively coupled plasma for solar cell applications by H.P. Zhou; D.Y. Wei; L.X. Xu; Y.N. Guo; S.Q. Xiao; S.Y. Huang; S. Xu (pp. 21-26).

► Low-frequency inductively coupled SiH₄+N₂+H₂ plasma is innovatively employed to deposit silicon nitride thin film. ► The deposition temperature is very low (100°C) and the deposition rate is competitive with that of PECVD. ► The surface recombination velocity in n-type Si (2–3Ωcm) is reduced to 36cm/s without post-deposition annealing. ► The chemical compositions and refractive index of SiN can be modulated by altering the gas flow rate ratio of N₂/SiH₄.Amorphous hydrogenated silicon nitride thin films with different chemical compositions (SiN_x:H) have been synthesized by using low frequency inductively coupled plasma of Si+N₂+H₂ at a low temperature of 100°C. The bonding configurations, bond density, hydrogen content, and chemical composition, as well as the refractive index are intensively investigated by a variety of characterization tools. Silicon nitride based antireflection layer on alkaline-textured silicon surface reduces the reflectivity to about 4%. As-deposited silicon nitride films exhibit an excellent passivation effect on p- and n-type Si. The surface recombination velocity is reduced to 36cm/s on n-type silicon with resistivity of 2–3Ωcm. The passivation effect originates from the H-related chemical passivation and fixed charge related field passivation. The growth mechanism of SiN_x:H from the precursor gas of H₂ diluted mixture of silane and nitrogen is also discussed.

Keywords: ICP; Silicon nitride; Passivation; Antireflection

Comparison of in situ and ex situ bioconjugation of Au nanoparticles generated by laser ablation by S. Mutisya; L. Franzel; B.O. Barnstein; T.W. Faber; J.J. Ryan; M.F. Bertino (pp. 27-30).

► Au nanoparticle generation by laser ablation of Au in PBS buffer and subsequent conjugation to immunoglobulin E. ► Comparable conjugation efficiency for in situ and ex situ fabrication. ► Laser ablation is suitable for conjugating complex biomolecules to nanoparticles.Au nanoparticles were generated by laser ablation in PBS buffer and conjugated to immunoglobulin E (IgE) during ablation ( in situ) and after ablation ( ex situ). Exposure for 5min to 532nm pulses with a duration of 150ps, an energy of 8mJ and a repetition rate of 10Hz yielded nanoparticles with a mean diameter of about 4nm for in situ conjugation and of about 5nm for ex situ conjugation. ELISA analysis showed that the conjugation efficiency was comparable for in situ and ex situ fabrication. ELISA for cytokine (IL-6) production by IgE-activated mast cells showed that the Au–IgE conjugates induced a response which coincided within error for conjugates prepared in situ and ex situ.

Keywords: Laser ablation; Bioconjugation; Au nanoparticles; IgE

Surface-enhanced Raman spectroscopy (SERS) using Ag nanoparticle films produced by pulsed laser deposition by C.A. Smyth; I. Mirza; J.G. Lunney; E.M. McCabe (pp. 31-35).

► Pulsed laser deposition (PLD) produces silver nanoparticle films. ► These films can be used for surface-enhanced Raman spectroscopy (SERS). ► Commercial film shows good SERS reproducibility but poor signal intensity. ► PLD shows a good SERS response coupled with good reproducibility.Thin silver nanoparticle films, of thickness 7nm, were deposited onto glass microslides using pulsed laser deposition (PLD). The films were then characterised using UV–vis spectroscopy and scanning transmission electron microscopy before Rhodamine 6G was deposited onto them for investigation using surface-enhanced Raman spectroscopy (SERS). The sensitivity obtained using SERS was compared to that obtained using a colloidal silver suspension and also to a commercial SERS substrate. The reproducibility of the films is also examined using statistical analysis.

Keywords: Pulsed laser deposition; Surface-enhanced Raman spectroscopy

Reverse atom transfer radical polymerization (RATRP) for anti-clotting PU-LaCl₃-g-P(MPC) films by Chunyan Lu; Ninglin Zhou; Yinghong Xiao; Yida Tang; Suxing Jin; Yue Wu; Jian Shen (pp. 36-44).

► A facile and efficient approach for surface modification of PU was introduced. ► MPC was grafted onto the surface of PU film by RATRP. ► Some free La³⁺ ions reacted with CPTM and the product served as mixed ligand complex. ► The obtained PUs had good blood compatibility and a possible usage in biomedicine.Low grafting density is a disadvantage both in reverse atom transfer radical polymerization (RATRP) and ATRP. In this work, the surfaces of polyurethane (PU) were treated by LaCl₃·6H₂O to obtain modified surfaces with hydrated layers. The reaction of surface-initiated RATRP was carried out easily, which may be attributed to the enriched hydroxyl groups on the hydrated layers. An innovation found in this work is that some free lanthanum ions (La³⁺) reacted with the silane coupling agent (CPTM) and the product served as mixed ligand complex. The mixed ligand complex instead of conventional 2,2′-bipyridine was adopted to serve as a ligand in the process of RATRP. As a result, PU surfaces grafted with well-defined polymer brushes (MPC) were obtained. PU substrates before and after modification were characterized by FTIR, XPS, AFM, SEM, SCA, respectively. The results showed that zwitterionic brushes were successfully fabricated on the PU surfaces (P(MPC)), and the content of the grafted layer increased gradually with polymerization time with the grafting density as high as 97.9%. The blood compatibility of the PU substrates was evaluated by plasma recalcification profiles test and platelet adhesion tests in vitro. It was found that all PU functionalized with zwitterionic brush showed improved resistance to nonspecific protein adsorption and platelet adhesion.

Keywords: Reverse atom transfer radical polymerization (RATRP); Biocompatibility; Layer growth; Modification; Rare earth ion (La; ³⁺; )

Tribological behavior of electron beam D6ac weldment by Shyh-Chi Wu; Kuang-Hung Tseng; Hua-Chiang Wen; Ming-Jhang Wu; Chang-Pin Chou (pp. 45-51).

Display Omitted► Flow formed D6ac steel tubing was joined using electron beam welding. ► Scratch test was used to evaluate the wear resistance of tempered weldment. ► D6ac weldment tempered at temperature of 450°C exhibits good fracture toughness. ► Tribological behavior of tempered weldment depended on tempered microstructures.A flow formed D6ac steel tubing was joined using electron beam (EB) welding. Thereafter, the EB weldments were treated by tempering at temperatures of 450°C and 550°C. After tempering, the microstructural features, mechanical properties, and tribological characteristics of the EB D6ac weldment were studied. This study used a scratch test to evaluate the sliding wear resistance of the tempered weldment. Results indicate that the tempering softens the microstructure by reducing the dislocation density of the flow formed D6ac steel. For the 450°C/2h/air cooling tempering treated D6ac steel, the fracture toughness of the EB weldment can be significantly improved. The tribological behavior of the tempered D6ac weldment depended on the tempered microstructures.

Keywords: D6ac steel; Flow forming; Electron beam welding; Tempering; Tribological behavior

Refining femtosecond laser induced periodical surface structures with liquid assist by L.S. Jiao; E.Y.K. Ng; H.Y. Zheng (pp. 52-55).

Display Omitted► LIPSS on silicon wafer was made in air and in ethanol environment. ► Ethanol environment produce cleaner surface ripples. ► Ethanol environment decrease spatial wavelength of the LIPSS by 30%. ► More number of pulses produce smaller spatial wavelength in air. ► Number of pulses do not influence spatial wavelength in ethanol environment.Laser induced periodic surface structures were generated on silicon wafer using femtosecond laser. The medium used in this study is both air and ethanol. The laser process parameters such as wavelength, number of pulse, laser fluence were kept constant for both the mediums. The focus of the study is to analyze spatial wavelength. When generating surface structures with air as a medium and same process parameter of the laser, spatial wavelength results showed a 30% increase compared to ethanol. The cleanliness of the surface generated using ethanol showed considerably less debris than in air. The results observed from the above investigation showed that the medium plays a predominant role in the generation of surface structures.

Keywords: fs laser; Si; Bubble generation process; Assist liquid; Drilling

Control of the graphene growth rate on capped SiC surface under strong Si confinement by C. Çelebi; C. Yanık; A.G. Demirkol; İsmet İ. Kaya (pp. 56-60).

► Graphene is grown on capped SiC surface with well defined cavity size. ► Graphene growth rate linearly increases with the cavity height. ► Graphene uniformity is reduced with thickness.The effect of the degree of Si confinement on the thickness and morphology of UHV grown epitaxial graphene on (000−1) SiC is investigated by using atomic force microscopy and Raman spectroscopy measurements. Prior to the graphene growth process, the C-face surface of a SiC substrate is capped by another SiC comprising three cavities on its Si-rich surface with depths varying from 0.5 to 2 microns. The Si atoms, thermally decomposed from the sample surface during high temperature annealing of the SiC_cap/SiC_sample stack, are separately trapped inside these individual cavities at the sample/cap interface. Our analyses show that the growth rate linearly increases with the cavity height. It was also found that stronger Si confinement yields more uniform graphene layers.

Keywords: Epitaxial graphene; SiC; Raman spectroscopy

UV-assisted surface modification of PET fiber for adhesion improvement by Xiang-Dong Liu; De-Kun Sheng; Xiu-Mei Gao; Tong-Bing Li; Yu-Ming Yang (pp. 61-69).

.Display Omitted► A facile and highly efficient approach for surface modification of PET fiber was introduced. ► FTIR spectrum analysis proves that MDI is fixed on the PET surface. ► The chemical bonding at the interface between the fiber and matrix based on the reaction ofNCO+HO-R→NH-COO-R. ► The PET fiber modified withNCO groups have a potential usage for composite fabrication.A facile and highly efficient method for adhesion improvement of PET/TPU laminates was introduced. A considerable improvement in adhesion was achieved by treating PET fabric with isocyanate (MDI) in toluene solution. Compared with unmodified ones, the maximal peel strength reaches to 2.27kN/m (up to three times). The fabrics were also treated with NaOH and CDT (corona discharge treatment) and the results were compared respectively. It is considered that the improvement mainly depends on the strengthening of chemical bonding and mechanical interlocking between the fiber and the adhesive matrix. As the difference directly affects the effective transference of the stress (tension force) from matrix to fiber. The failure surface of PET fiber was severely destroyed which could be examined by scanning electron microscopy (SEM).

Keywords: PET fiber; Surface modification; Adhesion improvement; Laminate

Effect of microstructure on the zinc phosphate conversion coatings on magnesium alloy AZ91 by Nguyen Van Phuong; Sungmo Moon; Doyon Chang; Kyu Hwan Lee (pp. 70-78).

► The decrease of β-phase causes decreasing of both coatings weight and etching weight. ► Microstructure plays important roles for formation and characteristics of the coating crystals. ► The β-phase becomes hydrogen evolution center during phosphating process. ► The coatings form two layers: inner layer and outer layer. ► The initial corrosion resistance of AZ91 is increased by phosphate coatings.The effect of the microstructure, particularly of β-Mg₁₇Al₁₂ phase, on the formation and growth of zinc phosphate conversion coatings on magnesium alloy AZ91 (AZ91) was studied. The zinc phosphate coatings were formed on AZ91 with different microstructures produced by heat treatment. The effect of the microstructure on the zinc phosphate coatings were examined using optical microscope (OM), X-ray diffraction (XRD), coatings weight and etching weight balances, scanning electron microscopy (SEM) and salt immersion test. Results showed that as-cast AZ91 contained a high volume fraction of the β-Mg₁₇Al₁₂ phase and it was dissolved into α-Mg phase during heat treatment at 400°C. The β-phase became center for hydrogen evolution during phosphating reaction (cathodic sites). The decreased volume fraction of the β-phase caused decreasing both coatings weight and etching weight of the phosphating process. However, it increased the crystal size of the coatings and improved corrosion resistance of AZ91 by immersing in 0.5M NaCl solution. Results also showed that the structure of the zinc phosphate conversion on AZ91 consisted of two layers: an outer crystal Zn₃(PO₄)₂·4H₂O (hopeite) and an inner which was mainly composed of MgZn₂(PO₄)₂ and Mg₃(PO₄)₂. A mechanism for the formation of two layers of the coatings was also proposed in this study.

Keywords: Magnesium; Conversion coating; Heat treatment; Zinc phosphate; Hopeite

Determination of irradiation parameters for laser-induced periodic surface structures by J. Eichstädt; G.R.B.E. Römer; A.J. Huis in ‘t Veld (pp. 79-87).

► We present an approach for the determination of irradiation parameters for laser-induced periodic surface structures. ► The approach is based on accumulated fluence and consists of two steps. ► (1) Determination of fluence domain boundaries and (2) approximation of irradiation parameters. ► The approach is required to apply LIPSS for surface functionalization. ► We provide experimental evidence that the accumulated fluence has a decisive role in the spatial emergence of LIPSS.The spatial emergence of laser-induced periodic surface structures (LIPSS) on single-crystalline silicon, upon irradiation with linearly polarized picosecond laser pulses (wavelength λ=1030nm, pulse duration τ=6.7ps, pulse repetition frequency f_p=1kHz) was studied theoretically and experimentally, under lateral displacement conditions. An experimental approach is presented for the determination of irradiation parameters of extended surface areas homogenously covered with LIPSS. The approach is based on accumulated fluence and consists of two steps, first the empirical determination of accumulated fluence domain boundaries and second the approximation of irradiation parameters. Such an approach is required for the application of LIPSS in the field of surface functionalization. The approach was successfully applied for structuring extended surface areas, which were homogenously covered with LIPSS. The areas, obtained by different irradiation parameter combinations, satisfying accumulated fluence boundary conditions, show the same type of LIPSS. This observation provides evidence, that the accumulated fluence has a decisive role in the spatial emergence of LIPSS. In the future, further experiments are required to verify the validity and boundaries of the approximations applied.

Keywords: Laser surface structuring; Laser-induced periodic surface structures (LIPSS); Extended areas; Accumulated fluence; Silicon

Effect of LaB₆ on the thermal shock property of MoSi₂-SiC coating for carbon/carbon composites by Ting Li; Hejun Li; Xiaohong Shi (pp. 88-93).

► LaB₆-MoSi₂-SiC and MoSi₂-SiC multi-composition coatings were coated on C/C composites by pack cementation. ► The microstructure and thermal shock resistance of both coatings were investigated. ► The addition of LaB₆ can increase the compactness, flexural strength and fracture toughness of the MoSi₂-SiC coating simultaneously. ► Both coatings bond well with the substrates before and after thermal cycling oxidation between 1773K and room temperature. ► The LaB₆-MoSi₂-SiC coated C/C shows better thermal shock resistance than the MoSi₂-SiC coated C/C.LaB₆-MoSi₂-SiC and MoSi₂-SiC coatings were prepared on the surface of carbon/carbon composites by pack cementation method. The crystal structures of the coatings were measured by X-ray diffraction. The morphologies and element distributions were also analyzed by scanning electron microscopy and energy dispersive spectroscopy, respectively. The effect of LaB₆ on the microstructure and thermal shock resistance of MoSi₂-SiC coating was investigated. The results indicated that the LaB₆-MoSi₂-SiC coating possessed a denser structure and superior thermal shock resistance. After 25 times of thermal cycling oxidation between 1773K and room temperature, the weight losses of the LaB₆-MoSi₂-SiC and MoSi₂-SiC coated samples were 0.627% and 2.019%, respectively.

Keywords: Carbon/carbon composites; LaB; ₆; -MoSi; ₂; -SiC coating; Thermal cycling oxidation

Preparation and characterization of boron-doped titania nano-materials with antibacterial activity by Xiangxin Xue; Yuzheng Wang; He Yang (pp. 94-99).

► B/TiO₂ nano-materials are prepared and doping improves particles agglomeration. ► Absorption spectrum move to visible light after doped. ► B/TiO₂ nano-materials firstly applied to the fields of antibacterial materials. ► Calcined at high temperature of 900°C, B/TiO₂ has still strong antibacterial.Boron-doped TiO₂ (B/TiO₂) nano-materials were synthesized by a sol–gel method and characterized by X-ray diffraction pattern (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrum (FT-IR) and UV–vis diffuse reflectance spectra (DRS). With the test of bacterial inhibition zone, the antibacterial properties of B/TiO₂ nano-materials on Escherichia coli were investigated. The results show that the structure of TiO₂ could be transformed from amorphous to anatase and then to rutile by increasing calcination temperature; part of the boron atoms probably have been weaved into the interstitial TiO₂ structure or incorporated into the TiO₂ lattice through occupying O sites, whereas others exist as B₂O₃. The results of antibacterial experiment under visible light irradiation show that the B/TiO₂ nano-materials exhibit enhanced antibacterial efficiency compared with non-doped TiO₂. Ultimately, the action mechanism of B/TiO₂ doping is discussed.

Keywords: Boron doping; Titania nanoparticle; Antimicrobial activity; Visible light

Microstructure properties of tempered D6ac steel by Derming Lian (pp. 100-104).

► We evaluated microstructure properties of tempered D6ac steel. ► The forming process has a high microhardness of martensite phase at surface layer. ► XRD spectra observed that the residual austenite and/or mixed structures of ferrite with the precipitation of carbides. ► Ferrite decreased and that of carbon and chromium elements increased upon increasing the tempering temperature.The aim of this study was to determine the microstructure and surface mechanical properties of tempered D6ac. The obtained microstructures exhibited a number of misfit dislocations from work hardening, with the degree of disorder dislocation decreasing gradually upon increasing the temperature at 650°C. XRD spectra observed that the residual austenite and/or mixed structures of ferrite with the precipitation of carbides at 650°C will result in a softer state than that of the room temperature specimen. In addition, the forming process has a high microhardness of martensite phase at surface layer, subjected to heat treatment until a stable state is achieved. The content of ferrite atoms decreased and that of carbon and chromium elements increased upon increasing the tempering temperature.

Keywords: Steel; Tempering; Microstructures; Toughness; XRD

Effect of surfactant concentration on characteristics of mesoporous bioactive glass prepared by evaporation induced self-assembly process by Chi-Chung Shih; Chi-Sheng Chien; Jung-Chang Kung; Jian-Chih Chen; Shy-Shin Chang; Pei-Shan Lu; Chi-Jen Shih (pp. 105-110).

► All the unwanted organic contents were removed completely at temperatures above 600°C. ► Specific surface area and pore volume of Mesoporous bioactive glasses reached maximum at the critical surfactant concentration. ► SAED pattern suggests that some glassy structures in the Bioactive Glasses became crystalline due to the heat treatment. ► The MBGs can induce the formation of an apatite-like layer on their surface in SBF, even after short soaking periods.Mesoporous bioactive glasses were prepared by the evaporation-induced self-assembly method. The main objective of the present study is to determine the effect of surfactant concentration on the synthesis of SiO₂–CaO–P₂O₅ mesoporous bioactive glasses; the characterization techniques used include X-ray diffraction, scanning electron microscopy and nitrogen adsorption and desorption isotherms. The results show that the specific surface area initially increased with increasing surfactant concentrations in the range of 2.1–9.1wt% and significantly decreased from 328.7 to 204.0m²/g in the concentration range of 9.1–12.5wt%. For texture evaluation, the selected area electron diffraction patterns of the mesoporous bioactive glass precursor gels (9.1wt% F127) calcined at different temperatures were analyzed; these patterns support the notion that some glassy structures in bioactive glasses become crystalline following heat treatment. The scanning electron microscopy images and X-ray diffraction patterns obtained agree with the inductively coupled plasma with atomic emission spectroscopy results as the mesoporous bioactive glasses can induce the formation of an apatite-like layer on their surface in SBF, even after short soaking periods.

Keywords: Mesoporous bioactive glasses; Surfactant; Texture; Evaporation induced self-assembly

Photocatalytic activity and reusability study of nanocrystalline TiO₂ films prepared by sputtering technique by B. Barrocas; O.C. Monteiro; M.E. Melo Jorge; S. Sério (pp. 111-116).

► TiO₂ films showed a promising photocatalytic performance after consecutive usages. ► Crystallinity and preferred orientation key parameters on films catalytic activity. ► Presence of vestigial rutile phase favors dye decolorization and TiO₂ films reuse. ► Photochemical stability of the TiO₂ films after successive photodegradations assays.The photocatalytic activity of nanocrystalline titanium dioxide (TiO₂) films deposited on unheated glass substrates by DC reactive magnetron sputtering at different oxygen partial pressures was tested on the decolorization of Rhodamine 6G (Rh6G) aqueous solutions. The dye photodecolorization process was studied considering the influence of the crystallinity and preferred orientation of growth of the prepared films. It was found that the higher photocatalytic activity was achieved by the film with preferred orientation of growth along the (101) crystal direction and showing a vestigial rutile phase in a mainly anatase phase. The recycling catalytic ability of the TiO₂ films was also evaluated and a promising photocatalytic performance has been revealed with a very low variation of the decay rate after five consecutive usages. Structural and morphological characterization revealed high photochemical stability of the films after successive photodegradations assays.

Keywords: TiO; ₂; films; Rhodamine 6G; Decolorization; Photocatalysis; TiO; ₂; reuse

Structural analysis of heat-treated birch ( Betule papyrifera) surface during artificial weathering by Xianai Huang; Duygu Kocaefe; Yasar Kocaefe; Yaman Boluk; Cornélia Krause (pp. 117-127).

► Investigate detailed structural changes of heat-treated wood due to weathering. ► Identify connection between physical structural changes and chemical degradation. ► Study effect of heat treatment conditions on weathering degradation process.Effect of artificial weathering on the surface structural changes of birch ( Betule papyrifera) wood, heat-treated to different temperatures, was studied using the fluorescence microscopy and the scanning electron microscopy (SEM). Changes in the chemical structure of wood components were analyzed by FTIR in order to understand the mechanism of degradation taking place due to heat treatment and artificial weathering. The results are compared with those of the untreated (kiln-dried) birch. The SEM analysis results show that the effect of weathering on the cell wall of the untreated birch surface is more than that of heat-treated samples. The FTIR spectroscopy results indicate that lignin is the most sensitive component of heat-treated birch to the weathering degradation process. Elimination of the amorphous and highly crystallised cellulose is observed for both heat-treated and untreated wood during weathering. It is also observed that heat treatment increases the lignin and crystallised cellulose contents, which to some extent protects heat-treated birch against degradation due to weathering.

Keywords: Heat-treated wood; Artificial weathering; FTIR; Wood chemical component; SEM; Structural change

Nano-SiC/SiC anti-oxidant coating on the surface of graphite by H. Jafari; N. Ehsani; S.A. Khalifeh-Soltani; M. Jalaly (pp. 128-132).

► Formation of a dual-layer coating on the graphite. ► Developing graded SiC and nano SiC layers using pack cementation and electrophoretic deposition methods, respectively. ► Improvement of high temperature oxidation behavior of substrate. ► Weight loss of 29% and 2.4% for single layer coating of SiC and dual layer coating of SiC_n/SiC, respectively.In this research, a dual-layer coating has been used to improve high temperature oxidation resistance of graphite substrate. For first layer, silicon carbide was applied by pack cementation method. Powder pack consisted of Si, SiC and Al₂O₃ and heat-treated at 1650°C in an argon atmosphere. SEM and XRD characterizations confirmed formation of SiC diffusion coating with about 500μm including compositionally gradient of C and Si elements. Electrophoretic deposition (EPD) was used to deposit nano SiC (SiC_n) particles as second layer. Thickness of second layer of SiC_n in corresponded optimal situation was 50μm. Samples with single and dual layers were investigated in oxidation test at 1600°C. Results showed that an extreme increase was occurred in oxidation resistance after application of second layer of nano SiC. Weight loss value for single layer coating of SiC and dual layer coating of SiC_n/SiC after oxidation test for 28h at 1600°C were 29wt.% and 2.4wt.%, respectively.

Keywords: High temperature oxidation; Nano SiC; Pack cementation; Electrophoretic deposition

Effect of post-sulfurization on the composition, structure and optical properties of Cu₂ZnSnS₄ thin films deposited by sputtering from a single quaternary target by Jun He; Lin Sun; Kezhi Zhang; Weijun Wang; Jinchun Jiang; Ye Chen; Pingxiong Yang; Junhao Chu (pp. 133-138).

► CZTS films were deposited directly from a CZTS target by sputtering process. ► The internal compressive stress relaxes in post-annealed CZTS films. ► The band gaps of post-annealed CZTS films are smaller than those of as-deposited.Quaternary Cu₂ZnSnS₄ (CZTS) thin films were deposited on heated glass substrates directly from a non-stoichiometric quaternary CZTS target by radio-frequency (RF) magnetron sputtering process, followed by post-sulfurization in atmosphere of Ar+H₂S(5%). The results of X-ray diffraction (XRD), Raman spectra, and scanning electron microscope (SEM) show that post-annealed process can improve the crystallinity of CZTS thin films. Both XRD and Raman spectra analysis indicate the internal compressive stress relaxes in post-annealed CZTS thin films. Further transmission spectra demonstrate that the band gaps of post-annealed CZTS thin films are smaller than those of as-deposited due to the relaxation of internal compressive stress and the increase of Cu content in the post-annealed CZTS films.

Keywords: Cu; ₂; ZnSnS; ₄; thin films; Sputtering; Post-sulfurization; Composition; Structure; Optical properties

The study of visible light active bismuth modified nitrogen doped titanium dioxide photocatlysts: Role of bismuth by Segomotso Bagwasi; Yuxiao Niu; Muhammad Nasir; Baozhu Tian; Jinlong Zhang (pp. 139-147).

► Bi/N–TiO₂ nanoparticles were prepared by hydrothermal and impregnation method. ► Bi₂₀TiO₃₂/N–TiO₂ composites were formed from 7mol% Bi loading in relation to Ti. ► Bi⁴⁺ was doped in the sub-surface while Bi₂₀TiO₃₂ was dispersed on the surface. ► Bi/N–TiO₂ degraded 2,4-DCP under visible light effectively. ► Bi species enhanced visible light harvesting, e⁻/h⁺ separation and mobility.Bismuth modified nitrogen doped TiO₂ nanoparticles have been successfully prepared by two steps synthesis route which includes hydrothermal and impregnation hydrolysis method. Samples were characterized using X-ray diffraction (XRD), N₂ physical adsorption, Transmission electron microscopy (TEM), UV–vis diffuse reflectance spectroscopy (UV–vis DRS), Fourier Transmission Infrared (FTIR), Raman, X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PLS) technologies. The preparatory method afforded the production of well crystallized spherical Bi modified N-doped TiO₂ nanoparticles with varied amounts of Bi content. XRD analysis results reveal that Bi exists as rare metastable Bi₂₀TiO₃₂ which started to surface at Bi loading content of 7mol% in relation to Ti ions. All Bi modified N–TiO₂ samples exhibited higher photocatalytic activity toward degradation of 2,4-DCP over N–TiO₂ under visible light irradiation. The sample with 10% composition of the Bi₂₀TiO₃₂ exhibited the highest activity. The superior photocatalytic performance of 10%Bi/N–TiO₂ is attributed to high visible light absorption as well as effective charge carrier separation. Therefore, the role of Bi species in the N–TiO₂ is improvement of visible light harvesting and facilitation of charge carrier separation hence alleviating electron–hole recombination.

Keywords: Bismuth modification; Photocatalyst; Visible light, Degradation; 2,4-Dichlorophenol

Material removal mechanism during porous silica cluster impact on crystal silicon substrate studied by molecular dynamics simulation by Ruling Chen; Ranran Jiang; Hong Lei; Min Liang (pp. 148-156).

Display Omitted► The impact of the porous silica clusters on a silicon substrate was studied by MD. ► The porous cluster shows high MRR and low surface damage at an optimal pore size. ► The high MRR is due to the combined effects of plough, adhesion and permeation. ► The low surface damage is due to the decreasing of the penetration depth. ► Enlarged contact area is more effective than increased penetration to enhance MRR.Molecular dynamics (MD) simulation is applied in analyzing the material removal mechanism of silicon substrate under the impact of large porous silica cluster with different pore diameters. With the increasing of the pore diameter of the porous cluster, the number of the atoms removed from the impact silicon surface will firstly increase and then decrease until the cluster is adhered to the substrate, which is due to the combinational effects of plough of the cluster, adhesion between the cluster and the substrate, and permeation of the substrate atoms through the pore of the cluster. And adhesion is the most significant one among these three effects. Meanwhile, the damage of the impact substrate will become weaker due to the decreasing of the penetration depth with the increasing of the pore diameter. In addition, it is found that the effect of an enlarged real contact area between the cluster and the substrate is more significant than that of deeper penetration of the cluster in order to enhance the material removal rate (MRR) during the impact process. These findings are instructive in optimizing the process parameters to obtain lower surface roughness and higher material removal rate during the chemical mechanical polishing process.

Keywords: Material removal mechanism; Porous silica cluster; Impact; Molecular dynamics simulation; Chemical mechanical polishing

Synthesis and enhanced photoelectrocatalytic activity of p–n junction Co₃O₄/TiO₂ nanotube arrays by Gaopeng Dai; Suqin Liu; Ying Liang; Tianxiong Luo (pp. 157-161).

► Co₃O₄/TiO₂ nanotube arrays (NTs) were prepared by an impregnating–deposition–decompostion method treatment. ► Co₃O₄/TiO₂ NTs exhibit high photoelectrocatalytic (PEC) activity. ► The high PEC activity was attribute to the formation of p–n junction between Co₃O₄ and TiO₂.Co₃O₄/TiO₂ nanotube arrays (NTs) were prepared by depositing Co₃O₄ nanoparticles (NPs) on the tube wall of the self-organized TiO₂ NTs using an impregnating–deposition–decompostion method. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–vis absorption spectroscopy. The photoelectrocatalytic (PEC) activity is evaluated by degradation of methyl orange (MO) aqueous solution. The prepared Co₃O₄/TiO₂ NTs exhibit much higher PEC activity than TiO₂ NTs due to the p–n junction formed between Co₃O₄ and TiO₂.

Keywords: Co; ₃; O; ₄; /TiO; ₂; nanotube arrays; Photoelectrocatalytic activity; p–n junction

Growth of flower-like ZnO on ZnO nanorod arrays created on zinc substrate through low-temperature hydrothermal synthesis by Ruixia Shi; Ping Yang; Xiaobin Dong; Qian Ma; Aiyu Zhang (pp. 162-170).

Display Omitted► Flower-like ZnO on ZnO nanorod arrays were fabricated on zinc substrate. ► Dense ZnO nanorod arrays and flower-like ZnO were created when the time is 30min. ► In situ nucleation and growth caused the generation of dense ZnO nanorod arrays. ► Growth mechanism of flower-like ZnO on ZnO nanorod arrays was proposed.Flower-like ZnO with various morphologies on ZnO nanorod arrays have been hydrothermally fabricated using zinc substrates at low temperature (70°C). The time-dependent experiments indicated that both dense ZnO nanorod arrays and flower-like ZnO were created when the reaction time is 30min. A growth mechanism was proposed to account for the growth of the flower-like ZnO on ZnO nanorod arrays. In situ growth caused the generation of dense ZnO nanorod arrays that were almost perpendicular to the surface of a zinc substrate. Due to the different rate of nucleation and crystal growth the morphology of flower-like ZnO on the top of ZnO nanorod arrays varied with the concentration of OH⁻. The ionic radius of alkali metal hydroxide used to generate Zn(OH)₄²⁻ ions greatly affected the morphology of ZnO. Owing to the small quantity of ZnO nuclei and Zn(OH)₄²⁻ the flower-like ZnO on ZnO nanorod arrays became fewer when lowering the concentration of Zn²⁺ and OH⁻ while keeping the ratio between them.

Keywords: Growth mechanism; Flower-like ZnO; ZnO nanorod arrays; Zinc substrate; Hydrothermal synthesis

Durable antimicrobial finishing of cellulose with QSA silicone by supercritical adsorption by Yong Chen; Mengqi Niu; Shu Yuan; Hongni Teng (pp. 171-175).

► CO₂-philic QAS silicone was synthesized through hydrosilylation and quaternization. ► QAS silicone was coated on cotton by adsorption from scCO₂. ► The coating procedure did not need covalently bonding tethering groups. ► The coating provided potent biocidal activities against Staphylococcus aureus and Escherichia coli. ► Antibacterial coating was very stable toward washing and UV irradiation.This study demonstrated a generic and simple approach to generate durable antibacterial ability on cellulose without using covalently bonding tethering groups that limit the structure design. CO₂-philic silicone with quaternary ammonium salt (QAS) pendants was synthesized through hydrosilylation reaction of poly(methylhydrosiloxane) (PMHS) and 2-(dimethylamino)ethyl acrylate in the presence of platinum-based catalyst and subsequent quaternization with 1-bromohexane. The resultant QAS silicone was deposited onto cellulose by adsorption from supercritical CO₂ (scCO₂) to provide potent biocidal activities against Staphylococcus aureus and Escherichia coli. Presented data also showed that the antibacterial layer was very stable toward washing and UV irradiation owning to the low surface tension and relatively high bond energy of the backbone of silicone. This procedure is applicable to substrates of other shape and chemistry.

Keywords: QAS silicone; Antibacterial coating; Supercritical adsorption

Study on feasibility of producing an amorphous surface layer of Fe₄₉Cr₁₈Mo₇B₁₆C₄Nb₃ by pulsed Nd:YAG laser surface melting by Reza Mojaver; Faezeh Mojtahedi; Hamid Reza Shahverdi; Mohammad Javad Torkamany (pp. 176-183).

► As-cast Fe₄₉Cr₁₈Mo₇B₁₆C₄Nb₃ alloy is submitted to pulsed laser surface melting. ► PLM in various scan speeds was unable to retain complete glassy microstructure. ► The effects of laser power and scan speed on amorphization have been discussed. ► A high overlapping factor in PLM can greatly restrict amorphization. ► Optimization of parameters of PLM to gain a glassy layer of the alloy is not easy.This work aims to investigate whether an amorphous surface layer can be obtained when as-cast Fe₄₉Cr₁₈Mo₇B₁₆C₄Nb₃ alloy is submitted to pulsed Nd:YAG laser surface melting. The experiments were conducted in the various laser scanning speeds. The microstructures of laser treated zones were investigated by X-ray diffraction XRD and Field Emission Scanning Electron Microscope (FESEM) and their microhardness were measured, too. The chemical composition of different points of each sample was analyzed by energy-dispersive X-ray spectroscopy EDS. Although the estimated cooling rates in surface layers were higher than the required cooling rate to achieve full amorphization, but the present experiments were unable to retain complete glassy microstructure on surface and a mixture of amorphous (low volume fraction) and ultrafine grained phases were produced in surface of samples. Based on the findings, it was understood that the overlapping of successive pulses and element redistributions occurred in pulsed laser melting could severely restrict amorphization. The influence of laser scan speed and laser power on heat input, melting ratio, compositional changes and cracking in laser treated zone were discussed separately. It is suggested that the limited range of laser variables in pulsed Nd:YAG laser melting may help to produce a sound amorphous phase of as-cast Fe₄₉Cr₁₈Mo₇B₁₆C₄Nb₃ alloy.

Keywords: Amorphous; Laser surface melting; Pulsed Nd:YAG laser; Fe-based glass former

Effect of post annealing on structural, optical and dielectric properties of MgTiO₃ thin films deposited by RF magnetron sputtering by T. Santhosh Kumar; R.K. Bhuyan; D. Pamu (pp. 184-190).

► MgTiO₃ thin films were grown on quartz and Pt–Si substrates by RF sputtering and MIM capacitors were fabricated at different O₂%. ► The sputtering target was prepared by mechanical alloying for the first time. ► The effect of annealing and O₂% on structural, microstructural, optical and dielectric properties was studied systematically. ► The increase in the refractive index and bandgap on annealing can be attributed to the improvement in packing density and crystallinity. ► The improvement in the dielectric properties is attributed to the increase in crystallinity and reduction in oxygen vacancies.MgTiO₃ (MTO) thin films have been deposited on to quartz and platinized silicon (Pt/TiO₂/SiO₂/Si) substrates by RF magnetron sputtering. The metal-MTO-metal (Ag-MTO-Pt/TiO₂/SiO₂/Si) thin film capacitors have been fabricated at different oxygen mixing percentage (OMP). The effects of OMP and post annealing on the structural, microstructural, optical and dielectric properties of MTO films were studied. The MTO target has been synthesized by mechanochemical synthesis method. The phase purity of the sputtering target was confirmed from X-ray diffraction pattern and refined toR3¯ space group with lattice parameters a= b=5.0557(12)Å, c=13.9003(9)Å. The chemical composition of the deposited films was confirmed from EDS spectra and all the films exhibited the composition of the sputtering target. The XRD patterns of the as-deposited films are amorphous and annealing at 700°C for 1h induced nanocrystallinity with the improved optical and dielectric properties. The annealed films exhibit refractive index in the range of 2.12–2.19 at 600nm with an optical bandgap value in between 4.11 and 4.19eV. The increase in the refractive index and bandgap upon annealing can be attributed to the improvement in packing density, crystallinity, and decrease in porosity ratio. Both the dielectric constant and tan δ decrease with the increase in frequency and were in the range of 13.7–31.11 and 0.006–0.124, respectively. The improvement in dielectric properties with the increase in OMP has been correlated to the reduction in oxygen vacancies, increase in crystallinity and grain size of the films.

Keywords: MTO thin films; RF magnetron sputtering; Optical properties; Dielectric properties

A new way to synthesize carbon nanofiber film on bulk titanium via hybrid surface mechanical attrition treatment by X.F. Yang; J. Lu (pp. 191-196).

Display Omitted► Carbon nanofibers have been synthesized in situ on bulk pure Ti by hybrid SMAT. ► Hybrid SMAT is an easy-control and lost cost way to synthesize CNFs on metal. ► CNFs synthesized on Ti by this way is extremely thin and uniform.Carbon nanofiber film was formed on bulk pure titanium via hybrid surface mechanical attrition treatment (SMAT). The microstructure of the sample was investigated by SEM, TEM, and RAMAN characterization. The CNFs are extremely long and uniform, exhibiting a high degree of uniformity of size of about 20nm. The possible growth mechanism was discussed. SMAT Ti played the role of catalyst and substrate during synthesizing process.

Keywords: Hybrid surface mechanical attrition treatment; Titanium; Carbon nanofibers

Significant effect of substrate temperature on the phase structure, optical and electrical properties of RF sputtered CIGS films by Zhou Yu; Yong Yan; Shasha Li; Yanxia Zhang; Chuanpeng Yan; Lian Liu; Yong Zhang; Yong Zhao (pp. 197-201).

► Secondary phase exist in the RF sputtered CIGS films as it deposited at 150°C and 500°C. ► CIGS films deposited beyond 350°C show (112) prefer orientation. ► E_g of the CIGS films increased with the increase of substrate temperature. ► Conductivity of the films is affected by “variable range hopping” mechanism.This work studied the effect of substrate temperature on the phase structure, optical and electrical properties of the one-step radio frequency sputtered Cu(In,Ga)Se₂ (CIGS) thin films. X-ray diffraction (XRD) analysis revealed that all the deposited CIGS films are chalcopyrite phase with polycrystalline structure. The films deposited beyond the substrate temperature of 350°C show (112) prefer orientation. Raman spectra reveal that the 150°C deposited CIGS film coexists with Cu2−_xSe phase and the 500°C deposited film contains ordered defect compound (ODC) phase. With the increase of substrate temperature, energy band gap of the CIGS film increase from 0.99 to 1.27eV. Films deposited at higher temperature exhibit larger electrical conductivity. Conductivity of the CIGS films is dominated by “variable range hopping” mechanism. The disorder in our CIGS the films is associated with the formation of intrinsic defects such as V_Se and In_Cu for their low formation energy.

Keywords: CIGS; Substrate temperature; Composition; Conductivity; Bang gap

Electronic structure of chromium-containing amorphous hydrogenated carbon thin films studied by X-ray absorption spectroscopy by Hsin-Yen Cheng; Jau-Wern Chiou; Jyh-Ming Ting; Jin-Ming Chen; Jyh-Fu Lee; Yonhua Tzeng (pp. 202-206).

► We obtained electronic structure of a-C:H/Cr thin films from C K-, Cr L_3.2-, and K-edge XANES. ► Thin a-C:H/Cr thin films were prepared using dc magnetron sputter deposition. ► It was found that the C 2 pCr 3 d hybridization gradually increases as the Cr nanoparticle size decreases. ► The amount of C-H bonding and the change in crystalline structure are the main factors affecting the optical absorptance.C K-, Cr L_3.2-, and K-edge X-ray absorption near-edge structure (XANES) analysis, high-resolution transmission electron microscopy examination, and optical absorptance have been examined to obtain a correlation between the optical absorptance and electronic structure of chromium-containing amorphous hydrogenated carbon thin films (a-C:H/Cr) deposited using a dc magnetron sputter deposition technique. It was found that the C 2 pCr 3 d hybridization gradually increases as the Cr nanoparticle (NP) size decreases, accompanied by a C 2 p interband transition. The amount of CH bonding and the change in crystalline structure are the main factors affecting the optical absorptance of the thin films. The size of the Cr NP affects the absorption wavelength range of the films. The optical absorptance and C K-edge XANES spectra indicate that a decrease in the size of Cr NP raises the conduction-band-minimum and may also increase the bandgap.

Keywords: Chromium-containing amorphous hydrogenated carbon thin films (a-C:H/Cr); X-ray absorption near-edge structure (XANES); Electronic structure; Solar absorbers; Solar absorptance; Thermal emittance

The microstructure and mechanical properties of multilayer diamond-like carbon films with different modulation ratios by Zhaoying Xu; Y.J. Zheng; F. Jiang; Y.X. Leng; Hong Sun; Nan Huang (pp. 207-212).

► The multilayer DLC films with different modulation ratios have been fabricated by FCVA. ► The multilayer DLC films can effectively decrease the residual stress of the DLC films. ► The multilayer DLC film with modulation ratio of 1:1 shows the best wear resistance.The multilayer DLC films consisting of sp²-rich DLC layers (soft DLC) and sp³-rich DLC layers (hard DLC) with different modulation ratios (thickness ratio of the hard DLC to soft DLC) ranging from 2:1, 1:1 to 1:2 had been deposited on Si (100) wafer and Ti–6Al–4V alloy substrates by filtered cathodic vacuum arc (FCVA) deposition. The effect of modulation ratio on the microstructure and properties of the multilayer DLC films including sp³ content, residual stress, mechanical properties, adhesion strength and wear resistance were studied by Raman spectroscopy, profilometry technique, nanoindenter, Vickers indentation test, scanning electron microscopy (SEM) and ball-on-disc reciprocating friction test. The results showed that the sp³ content and the hardness of the multilayer DLC films decreased with modulation ratios decreasing. The stress of the multilayer DLC films could be effectively reduced and the stress decreased with the modulation ratio decreasing. The multilayer DLC film with modulation ratio of 1:1 had the best wear resistance due to a balance between hardness and residual stress.

Keywords: Modulation ratio; Ti–6Al–4V alloy; Microstructure; Residual stress; Mechanical properties; Multilayer diamond-like carbon films

Effect of deposition variables on properties of CBD ZnS thin films prepared in chemical bath of ZnSO₄/SC(NH₂)₂/Na₃C₃H₅O₇/NH₄OH by Wei-Long Liu; Chang-Siao Yang; Shu-Huei Hsieh; Wen-Jauh Chen; Chi-Lon Fern (pp. 213-218).

► The CBD ZnS thin films were prepared on soda lime glass in a bath of ZnSO₄/SC(NH₂)₂/Na₃C₃H₅O₇/NH₄OH. ► The transmittance for ultraviolet–visible rays (300–800nm) through those films is in a range of 70.8–87.8%. ► The ZnS thin films have an energy gap from 3.885 to 3.980eV which increases with the decrease of ZnSO₄ concentration. ► The CBD ZnS thin film with a Zn/S of 1:1 could be prepared at 80°C in chemical bath.The CBD ZnS thin films were prepared on substrates of soda lime glass in chemical bath. The effect of deposition variables including zinc sulfate, thiourea, tri-sodium citrate, ammoina water, bath temperature, and deposition time on the properties of CBD ZnS thin films were comprehensively studied. The CBD ZnS thin films were characterized by a field emission scanning electron microscope (FESEM) for the surface and cross section morphologies and thicknesses, an energy dispersive spectrometer equipped in FESEM for the atomic% of Zn and S, an ultraviolet–visible spectrometer (300–800nm) for the transmittance and energy gap, and an atomic force microscope for the surface roughness. The results showed that the CBD ZnS thin films have a transmittance for ultraviolet–visible rays (300–800nm) from 70.8 to 87.8%. The CBD ZnS thin films prepared in bath 5 have an energy gap from 3.881 to 3.980eV. The CBD ZnS thin films prepared in bath 6 have a growth rate from 1.8 to 3.2nm/min and activation energy of 59.8kJ/mol for their growth.

Keywords: Chemical synthesis; Thin films; Visible and ultraviolet spectrometers

Dependence of core-level XPS spectra on iron silicide phase by Naofumi Ohtsu; Masaoki Oku; Kozue Satoh; Kazuaki Wagatsuma (pp. 219-224).

► The clean iron silicide surfaces were prepared by fracturing the bulk sample. ► XPS spectra for Fe₃Si, FeSi, and FeSi₂ were collected from the clean surface. ► The silicides exhibited chemical shifts from elemental Fe in the Fe 2p spectra. ► The degree of asymmetry in the Fe 2p spectra was linked to Si content.Core-level and valence-band XPS spectra for Fe₃Si, FeSi, and FeSi₂ were collected from the surfaces of polycrystalline silicides. The clean surfaces were prepared by mechanically fracturing the bulk polycrystalline silicides in a spectrometer under ultra-high vacuum, and then the chemical shifts and spectral shapes characteristic of each iron silicide phase were investigated in detail. The Fe 2p spectra for these samples exhibited positive chemical shifts as compared to those of elemental Fe, and the shifts observed for FeSi₂ were slightly larger than the others. The spectral shapes of the Fe 2p_3/2 spectra had asymmetric shapes, decreasing in magnitude with increasing Si content. The Fe 3s spectra for Fe₃Si exhibited multiple splitting due to the exchange interaction between the 3s core and the 3d unfilled shell; such splitting was not found in the other silicide phases. In comparing the valence band spectra of these silicides, the spectral intensity at the Fermi edge was found to be notably higher for Fe₃Si. Similar results were obtained from theoretical consideration of the partial density of state (PDOS) using a first-principle calculation method. These features affect the asymmetric spectral shape of the Fe 2p spectra for Fe₃Si.

Keywords: Iron silicides; Core-level XPS spectra; Spectral shape; Band structure; In situ; fracturing

Structural and electrical characterization of La_0.72Ca_0.28MnO₃ ceramic and thin films by Ji Ma; Mya Theingi; Hui Zhang; Xuan Ding; Qingming Chen (pp. 225-228).

► La_0.72Ca_0.28MnO₃ films were prepared on flat and 15° vicinal cut LaAlO₃ substrate by pulsed laser deposition method. ► The target used was fabricated with powders synthesized through sol-gel process. ► Rocking curve and atomic force microscope images demonstrate the high crystalline quality. ► The film deposited on tilted substrate shows a more uniform grain size. ► The film deposited on tilted substrate shows a larger temperature coefficient of resistance value (11.3%).La1−_xCa_xMnO₃ bulk ceramic with Ca content of 0.28 was sintered from nano-powders synthesized by sol–gel method. Epitaxial thin films of La_0.72Ca_0.28MnO₃ have been prepared on both untilted and 15° vicinal cut LaAlO₃ (001) substrates by pulsed laser deposition technique. The structure and surface morphology of LCMO samples (powders, target and films) were investigated by X-ray diffraction, scanning electron microscope and atom force microscope. The temperature dependence of the resistance was also studied. Large temperature coefficient of resistance value of 11.3% at 234.1K was obtained for the film grown on titled substrate.

Keywords: La; _0.72; Ca; _0.28; MnO; ₃; Powders; Ceramic; Thin films; Temperature coefficient of resistance

Laser-induced colour marking—Sensitivity scaling for a stainless steel by Arkadiusz J. Antończak; Dariusz Kocoń; Maciej Nowak; Paweł Kozioł; Krzysztof M. Abramski (pp. 229-236).

► Effect of parameters of laser colour marking on the colour obtained were analyzed. ► The investigations were performed for AISI 304 stainless steel using a fibre laser. ► For all those parameters which affect the colour, stability of 10⁻² (1%) is required. ► Modifications to achieve greater repeatability of colour marking were proposed. ► Two types of ageing tests, UV radiation and a salt spray test, were performed.This paper presents the results of measurements and analysis of the influence of laser marking process parameters on the colour obtained. The study was conducted for AISI 304 multipurpose stainless steel using a commercially available industrial fibre laser. It was determined how various process parameters, such as laser power, pulse repetition rate, scan speed of the material, spacing between successive lines, thickness and temperature of the material, location of the sample relative to the focal plane, size of marked fields and position in the workpiece, affect the repeatability of the colours obtained. For objective assessment of colour changes, an optical spectrometer and the CIE colour difference parameter Δ E_ab* were used. Additionally, in order to determine the susceptibility of laser colour marking to the ageing process, two types of tests – UV radiation and a salt spray test – were performed. Based on this analysis, necessary modifications to the laser systems commonly used for monochrome marking are proposed in order to achieve greater repeatability in colour marking.

Keywords: Laser colour marking; Stainless steel; Surface oxidation; Colorimetric; CIE; L; *; a; *; b; *; Colour; Fibre laserPACS; 81.65.−b (81.65.Mq); 42.62.Cf; 42.55.Wd; 07.60.Dq

X-ray absorption spectroscopy and photoluminescence study of rare earth ions doped strontium sulphide phosphors by Ankush Vij; Sanjeev Gautam; Vinay Kumar; R. Brajpuriya; Ravi Kumar; Nafa Singh; Keun Hwa Chae (pp. 237-241).

► NEXAFS absorption edges were simulated using atomic multiplet calculations. ► Simulated and experimental results were correlated to ascertain electronic structure of dopant. ► Ce and Sm were found to be in their trivalent electronic states in SrS. ► The PL emission and excitation spectra of SrS:Sm have been discussed. ► SrS:Ce,Sm shows different PL emission at different excitation energies.We present here the electronic structure and photoluminescence properties of Sm (0.1–1.0mol%) doped SrS phosphors. The doping in SrS was probed by near-edge X-ray absorption fine structure (NEXAFS) at M_5,4-edges of Sm in total electron yield mode. The simulated absorption edges using atomic multiplet calculations were correlated with experimental results, which clearly reveal the presence of trivalent state of Sm in SrS matrix. However, for Sm (1mol%), very minor traces of Sm²⁺ were also observed, which have been explained by comparing the NEXAFS spectra in total electron and florescence yield mode. The PL emission of SrS:Sm comprises of three sharp bands at 567, 602 and 650nm owing to the well-known intra 4 f transitions from⁴ G_5/2 to⁶ H_J ( J=5/2, 7/2, 9/2) levels of Sm³⁺ ions in SrS host. The effect of Ce co-doping on SrS:Sm phosphors was also investigated, which exhibits characteristic PL emission of independent ions at their respective excitation wavelengths. However, at an excitation wavelength of 393nm, SrS:Ce,Sm exhibits the simultaneous characteristic PL emission of both ions spanning into blue–green–red region. The CIE chromaticity coordinates also clearly show the influence of excitation wavelengths on the emission colour of SrS:Ce,Sm.

Keywords: NEXAFS; SrS:Sm; PL emission and excitation

Synthesis of a sugar-organometallic compound 1,1′-difurfurylferrocene and its microwave preparation of carbon/iron oxide nanocomposite by Shanyu Zhao; Daniel C. Cooper; Haixun Xu; Pinghua Zhu; J. William Suggs (pp. 242-246).

In order to synthesize a carbon–metal or metal oxide combination sphere, carbonaceous resource furfural was introduced, which was nucleophilic treated with 1,1′-dilithioferrocene to form a sugar-organometallic compound: ferrocenyl monosaccharide derivative 1,1′-difurfurylferrocene, which can be hydrothermally treated in a microwave reactor to give 300–500nm microspheres with the α-Fe₂O₃ or Fe₃O₄ formed on the surface, which may be favorable for new magnetic materials preparation or instead of iron with other metal ions, versatile carbon/metal composites will be possibly synthesized for catalysis, drug delivery and magnetic uses.Display Omitted► We synthesized 1,1′-difurfurylferrocene by nucleophilic treating furfural with 1,1′-dilithioferrocene. ► 1,1′-Difurfurylferrocene can be hydrothermally treated by microwave to give microspheres with iron oxides on the surface. ► 1,1′-Difurfurylferrocene has 2 reactive furanose units, which form carbonspheres and ferrocenyl can give iron oxides. ► REDOX atmosphere influences the coating structures.In order to synthesize a carbon–metal or metal oxide combination sphere, carbonaceous resource furfural1 was introduced, which was nucleophilic treated with 1,1′-dilithioferrocene2 to form a sugar-organometallic compound: ferrocenyl monosaccharide derivative 1,1′-difurfurylferrocene3. 1,1′-Difurfurylferrocene3 can be hydrothermally treated in a microwave reactor to give 300–500nm microspheres with the α-Fe₂O₃ or Fe₃O₄ nanocrystals formed on the surface, which may be favorable for new magnetic materials preparation or instead of iron with other metal ions, versatile carbon/metal composites will be possibly synthesized for catalysis, drug delivery and magnetic uses.

Keywords: Ferrocenyl monosaccharide derivative; Hydrothermal; Microwave; Nanocomposite

Dissociation and reconstruction of O₂ on Al (111) studied by First-principles by J.X. Guo; L.J. Wei; D.Y. Ge; L. Guan; Y.L. Wang; B.T. Liu (pp. 247-254).

► All the possible adsorption sites of oxygen molecule were considered by First-principles. ► The information was obtained about the dissociation of oxygen molecule. ► The information was obtained about Al (111) surface reconstruction. ► We discussed the correlation of surface reconstruction, adsorption site, adsorption energy and oxygen coverage in detail.The dissociative adsorption and reconstruction of oxygen molecule on Al (111) surface have been investigated by Density Functional Theory (DFT) with the generalized gradient approximation using structure optimization and a supercell approach. Four vertical and eight parallel sites of O₂ adsorption on Al (111) surface were calculated corresponding to oxygen coverages of 0.22, 0.5 and 1 ML (monolayer). It is found that different surface geometries are formed after oxygen molecule dissociation on different sites of Al (111) surface, which is determined by oxygen original adsorption sites as well as oxygen coverage. The oxygen atoms coming from oxygen molecule dissociation tend to occupy the most stable adsorption sites of the Al (111) surface. When oxygen coverage is 1 ML, the dissociation of oxygen molecule is related to both its original adsorption site and the interaction between oxygen molecules. The correlation of surface reconstruction of Al (111) surface, adsorption site, adsorption energy and oxygen coverage is discussed in detail. The steering effect plays an important role in the oxygen molecule dissociative process.

Keywords: PACS; 71.15.Mb; 73.20.AtDissociation; Density Functional Theory; Oxygen molecule; Al (1; 1; 1); Reconstruction

Fabrication of one-dimensional mesoporous α-Fe₂O₃ nanostructure via self-sacrificial template and its enhanced Cr(VI) adsorption capacity by Zhigang Jia; Qiuze Wang; Daping Ren; Rongsun Zhu (pp. 255-260).

► The growth mechanism of α-FeC₂O₄ micro/nanorods was investigated in detail. ► The mesoporous α-Fe₂O₃ micro/nanorods were prepared through α-FeC₂O₄ template. ► Mesoporous α-Fe₂O₃ micro/nanorods displayed excellent adsorption property for Cr(VI). ► The adsorption data for Cr(VI) fit well with the Langmuir adsorption isotherms. ► The adsorption process can be explained by the pseudo-second order kinetic model.In the present study, the mesoporous α-Fe₂O₃ nanorods have been prepared through self-sacrificial template route, which α-FeC₂O₄ rodlike precursor is employed as template. The growth mechanism of α-FeC₂O₄ rodlike precursor is investigated on the basis of a series of scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) characterization of the products obtained at different durations. Transmission electron micrograph (TEM) observations together with nitrogen adsorption–desorption measurement for the mesoporous α-Fe₂O₃ nanorods show the formation of mesoporous nanostructure with an average pore size of 4.6nm and a surface area of 124.6m²/g. One-dimensional mesoporous α-Fe₂O₃ nanostructures are employed as adsorbent to remove Cr(VI) from aqueous solution. The kinetic study and adsorption isotherm are examined in batch experiments. The kinetic process is described by a pseudo-second-order rate model very well. The adsorption data fits well to the Langmuir model. The maximum adsorption capacity of Cr(VI) uptake on the adsorbent is 22.72mg/g at 25°C.

Keywords: Nanostructures; Oxides; Chemical synthesis; Microstructure; Adsorption

Effects of acid treatment on structure, properties and biocompatibility of carbon nanotubes by Chenbo Dong; Alan S. Campell; Reem Eldawud; Gabriela Perhinschi; Yon Rojanasakul; Cerasela Zoica Dinu (pp. 261-268).

Display Omitted► Incubation of carbon nanotubes in an acid mixture changes their chemical and physical properties as shown using spectroscopy and microscopy assays. ► Acid incubation of single-walled carbon nanotubes reduces their intrinsic cytotoxicity in relation to human epithelial cells. ► Multi-walled carbon nanotubes with user-controlled physical and chemical properties serve as platforms for the next generation of biosensors.Carbon nanotubes (CNTs) are promising to be the next generation of viable tools for bioapplications. Further advances in such bioapplications may depend on improved understanding of CNTs physical and chemical properties as well as control over their biocompatibility. Herein we performed a systematic study to show how acid oxidation treatment changes CNTs physical and chemical properties and leads to improved CNTs biocompatibility. Specifically, by incubating CNTs in a strong acid mixture we created a user-defined library of CNTs samples with different characteristics as recorded using Raman energy dispersive X-ray spectroscopy, atomic force microscopy, or solubility tests. Systematically characterized CNTs were subsequently tested for their biocompatibility in relation to human epithelial cells or enzymes. Such selected examples are building pertinent relationships between CNTs biocompatibility and their intrinsic properties by showing that acid oxidation treatment lowers CNTs toxicity providing feasible platforms to be used for biomedical applications or the next generation of biosensors.

Keywords: Nanotubes; Acid treatment; Structure modification; Cytotoxicity; Biocompatibility

Crystallization characteristics of Mg-doped Ge₂Sb₂Te₅ films for phase change memory applications by Jing Fu; Xiang Shen; Qiuhua Nie; Guoxiang Wang; Liangcai Wu; Shixun Dai; Tiefeng Xu; R.P. Wang (pp. 269-272).

► Mg-doped Ge₂Sb₂Te₅ (GST) phase change films with higher resistance and better thermal stability have been proposed. ► The increase of Mg content result in an enhancement in crystallization temperature, activation energy and electrical resistance. ► The proper Mg addition in GST can lead to a one-step crystallization process from amorphous to faced-centered cubic (fcc) phase. ► The formation of covalent MgSb and MgTe bonds contribute to the enhancement thermal stability in Mg-doped GST films.Mg-doped Ge₂Sb₂Te₅ (GST) films with different Mg doping concentrations have been prepared, and their crystallization behavior, structure and electrical properties have been systematically investigated for phase-change memory applications. The results show that the addition of Mg into GST films could result in an enhancement in crystallization temperature, activation energy and electrical resistance compared with the conventional GST films, indicating that a good amorphous thermal stability. On the other hand, the proper Mg concentration ranging from 13.6 to 31.1at.% can lead to a one-step crystallization process from amorphous to faced-centered cubic (fcc) phase and suppress the formation of the hexagonal close-packed (hcp) crystalline phase. X-ray photoelectron spectra (XPS) further confirm that the formation of covalent MgSb and MgTe bonds contribute to the enhanced thermal stability in Mg-doped GST films.

Keywords: Thin films; Phase transformation; XRD; Electrical properties

Laser-induced surface alloying in nanosized Ni/Ti multilayer structures by Suzana Petrović; B. Radak; D. Peruško; P. Pelicon; J. Kovač; M. Mitrić; B. Gaković; M. Trtica (pp. 273-279).

► Different multilayer (Ni/Ti) structures were modified by picoseconds Nd:YAG laser. ► Laser-induced alloying was achieved within the heat affected zone (HAZ) of the sample. ► Surface segregation of titanium was followed by formation of thin TiO₂ film. ► Ripple structures on the surfaces of the 5- and 10-bilayered samples were recorded.Laser-induced alloying effects on the composition and structure of different Ni/Ti multilayer structures were studied. Thin films composed of one, five, and ten (Ni/Ti) bilayers were deposited by DC ion sputtering on (100) Si wafers. Laser irradiations were performed by 150ps pulses of a Nd:YAG laser operating at 1064nm. The samples were characterized by Rutherford backscattering spectrometry (RBS), Auger electron spectroscopy (AES), X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). At a laser fluence of 0.9Jcm⁻², interaction between Ni and Ti layers was initiated, and NiTi alloy formed in 5- and 10-bilayered samples. Progressed alloying was achieved at a laser fluence of 1.2Jcm⁻². The alloy was formed mostly within the heat affected zone (HAZ) of the sample. Surface segregation of titanium was followed by formation of a 25nm thin TiO₂ film on the surface of the multilayered structures. In addition, parallel periodic surface structures on the surfaces of the 5- and 10-bilayered samples were clearly recorded. Their period in the case of the 5-bilayered system (0.77μm) agrees very well with the predictions of the common theory, whereas, in the case of the 10-bilayered system, two periods of such structures are observed (1.43μm and 0.4μm), and none of them coincides with the prediction.

Keywords: Ni/Ti multilayer; Laser alloying; Diffusion; Surface segregation; Ripple structure

Fabrication of nanoscale alumina on NiAl(100) with a scanning tunneling microscope by C.W. Lin; C.T. Wang; M.F. Luo (pp. 280-285).

► Nanoscale alumina was fabricated on NiAl(100) surface with a STM tip. ► Varied powers (bias×current) give two distinct modes of oxidation. ► In the high-power mode alumina forms on the surface near the tip. ► In the low-power mode alumina grows along direction [001] or [010] of NiAl(100). ► The grown alumina strips have minimal width about 3nm.Nanoscale alumina was fabricated on NiAl (100) surface using a scanning tunneling microscope in an ultrathin vacuum condition. With the tunneling current greater than 0.4nA and the power (bias voltage×tunneling current) greater than 0.24nW, Al and pre-adsorbed O atoms were activated to form alumina (with thickness 0.25–1.0nm) on the surface directly vicinal to the tip; the width and thickness of the grown alumina strips are controllable by the current and bias. With an evidently smaller power and a smaller bias (≦1.0V), crystalline alumina were grown along direction [001] or [010] of NiAl(100) in the tip-scanned area of either O-chemisorbed or oxidized surfaces, independent of the direction of tip movement. The alumina strips grown through the latter mode have minimal width near 3nm.

Keywords: Alumina; NiAl; Scanning tunneling microscope; Oxidation; Localized heating; Ultrahigh vacuum

Different plasma-based strategies to improve the interaction of anionic dyes with polyester fabrics surface by Tarek Salem; Dieter Pleul; Mirko Nitschke; Martin Müller; Frank Simon (pp. 286-296).

► Different plasma-based synthetic concepts were employed to endow PET fabrics with accessible amine functionalities. ► Streaming potential measurements were used to characterize surface charges. ► Substrate-independent coloration enriched by plasma-based modification.Low-pressure plasma treatments with subsequent immobilization of functional macromolecules from aqueous solution have gained an increasing popularity for its applications in new industrial processes. In this work, two different strategies to endow polyester fabrics (PET) with accessible primary amino groups are compared.(a) NH₂ groups were produced directly using low-pressure ammonia plasma. (b) Negatively charged groups were introduced by low-pressure oxygen plasma to hydrophilize the fabric surfaces and used as anchor groups for the immobilization of water-borne polyelectrolyte copolymers poly(vinyl amine- co-vinyl amide) (PVAm).To study the effects of these surface modifications, a combination of various surface-sensitive characterization techniques such as X-ray photoelectron spectroscopy (XPS), streaming potential measurements and time-dependent contact angle measurements were used. Furthermore, the influence of the pre-treatments on the interaction of PET fabrics with water-soluble dyes was evaluated. For that purpose, color strength and fastness tests were carried out to prove the effectiveness of pre-treatments.

Keywords: Plasma treatment; Poly(ethylene terephthalate) (PET); Polyelectrolytes; Poly(vinyl amine-; co; -vinyl amide) (PVAm); XPS; Electrokinetics; Anionic dyes

High-resolution photoelectron spectroscopy analysis of sulfidation of brass at the rubber/brass interface by Kenichi Ozawa; Takashi Kakubo; Katsunori Shimizu; Naoya Amino; Kazuhiko Mase; Takayuki Komatsu (pp. 297-304).

Display Omitted► Chemical composition at the rubber/brass interface is investigated. ► The 2-min vulcanization reaction is enough to convert the interface composition. ► Five S-containing species are identified at the interface. ► Strong rubber–brass adhesion is related to the Cu₂S/CuS ratio. ► Degradation of adhesion proceeds along with desulfidation of the interface.High resolution photoelectron spectroscopy is utilized to investigate the chemical composition at the rubber/brass interface to elucidate the origin of strong adhesion as well as the degradation between rubber and brass. Special attention has been given to copper sulfides formed at the interface during the vulcanization reaction at 170°C. At least five sulfur-containing species are identified in the adhesive interlayer including crystalline CuS and amorphous Cu_xS ( x≃2). These copper sulfide species are not uniformly distributed within the layer, but there exits the concentration gradation; the concentration of Cu_xS is high in the region on the rubber side and is diminished in the deeper region, while vice versa for that of CuS. Degradation of the interface adhesive strength by prolonged vulcanization arises from the decrease in the Cu_xS/CuS ratio accompanying desulfurization of the adhesive layer.

Keywords: Photoelectron spectroscopy; Rubber; Brass; Adhesion; Copper sulfide

Platinum-nickel catalyst: The effect of promoters in cis-oleic acid adsorption by S. Simonetti; M. Martirena; S. Ulacco; G. Brizuela (pp. 305-311).

► CO adsorption is more favored than CC adsorption on the PtNi(111) surface. ► The adsorption of the olefinic bond is strengthened by K, Mg, Co, B or Pd promoters. ► The energy of the system and the CC/surface distances decrease using promoters. ► The molecule–surface interaction is favored by electron density exchange. ► Co promoter shows better adsorption properties than K, Mg, B or Pd.The study of the cis-oleic acid adsorption, on clean and promoted (K, Mg, Co, B or Pd) PtNi(111) surface was performed by quatum chemical calculations. The oleic acid adsorption on PtNi(111) surface shows a weak molecule–surface interaction. No preferential site for CC adsorption is computed and only the CO adsorption is favored on the clean PtNi(111) surface. The adsorption properties of the PtNi(111) are improved by promoters. The stability of the system is increased and the CC/surface distances are reduced when promoters are present. Among the considered promoters, Co has the best performance in terms of system stability. The lowest C p orbital substantially interacts with Pt and Co s, p and d orbitals. The change electron density of metal centers, enhance the CC adsorption being the Pt–C interaction the more favored. After adsorption, the strength of the CC, PtPt and PtCo bonds decrease while a molecule–surface bond is formed.

Keywords: Oleic acid; Adsorption; Platinum; Nickel; Promoter

High temperature oxidation behavior of AISI 304L stainless steel—Effect of surface working operations by Swati Ghosh; M. Kiran Kumar; Vivekanand Kain (pp. 312-319).

► Surface working resulted in thinner oxide on the surface. ► Oxides on machined/ground surfaces richer in Cr, higher in specific resistivity. ► Additional ionic transport process at the metal-oxide for ground sample established. ► Presence of fragmented grains and martensite influenced oxide nature/morphology.The oxidation behavior of grade 304L stainless steel (SS) subjected to different surface finishing (machining and grinding) operations was followed in situ by contact electric resistance (CER) and electrochemical impedance spectroscopy (EIS) measurements using controlled distance electrochemistry (CDE) technique in high purity water (conductivity<0.1μScm⁻¹) at 300°C and 10MPa in an autoclave connected to a recirculation loop system. The results highlight the distinct differences in the oxidation behavior of surface worked material as compared to solution annealed material in terms of specific resistivity and low frequency Warburg impedance. The resultant oxide layer was characterized for (a) elemental analyses by glow discharge optical emission spectroscopy (GDOES) and (b) morphology by scanning electron microscopy (SEM). Oxide layers with higher specific resistivity and chromium content were formed in case of machined and ground conditions. Presence of an additional ionic transport process has also been identified for the ground condition at the metal/oxide interface. These differences in electrochemical properties and distinct morphological features of the oxide layer as a result of surface working were attributed to the prevalence of heavily fragmented grain structure and presence of martensite.

Keywords: Stainless steel; Surface working; High temperature oxidation; Electrochemical impedance spectroscopy

Density functional theory study of the effects of alloying additions on sulfur adsorption on nickel surfaces by Oleksandr I. Malyi; Zhong Chen; Vadym V. Kulish; Kewu Bai; Ping Wu (pp. 320-328).

► We study sulfur adsorption on metal doped and undoped Ni surfaces. ► Hybridization of Ni-3d and S-3p states plays the most important role in the formation of NiS bonds. ► Au, Ag, Al, Bi, Cd, Sb, Sn, Zn additions can significantly increase sulfur tolerance of Ni. ► Sn, Sb, and Bi alloying additions have the strongest effects on sulfur adsorption.Reactions of hydrogen sulfide (H₂S) with Nickel/Ytrria-doped zirconia (Ni/YDZ) anode materials might cause degradation of the performance of solid oxide fuel cells when S containing fuels are used. In this paper, we employ density functional theory to investigate S adsorption on metal (M)-doped and undoped Ni(001) and Ni(111) surfaces. Based on the performed calculations, we analyze the effects of 12 alloying additions (Ag, Au, Al, Bi, Cd, Co, Cu, Fe, Sn, Sb, V, and Zn) on the temperature of transition between clean (S atoms do not adsorb on the surfaces) and contaminated (S atoms can adsorb on the surfaces spontaneously) M-doped Ni surfaces for different concentrations of H₂S in the fuel. Predicted results are consistent with many experimental studies relevant to S poisoning of both Ni/YDZ and M-doped Ni/YDZ anode materials. This study is important to understand S poisoning phenomena and to develop new S tolerant anode materials.

Keywords: Adsorption; S poisoning; Solid oxide fuel cells; Ni surfaces; Density functional theory; Alloying additions

Graphene sheets synthesized by ionic-liquid-assisted electrolysis for application in water purification by Chia-Feng Chang; Quang Duc Truong; Jiann-Ruey Chen (pp. 329-334).

► Graphene sheets have been successfully synthesized by ionic-liquid-assisted electrolysis. ► Graphene sheets are superior adsorbents for heavy metal removal. ► Graphene sheets are highly efficient for water purification for the developing economies.A facile and green synthesis of graphene sheets by ionic-liquid-assisted electrolysis was investigated in this work. The synthesized graphene sheets have been studied using transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray powder diffraction (XRD), Raman spectroscopy (Raman) and Fourier transform infrared (FTIR) analysis. The obtained graphene was used for the adsorption of Fe²⁺ whose presence in the drinking water in wide areas of South Asia has been widely known. The result shows that the graphene could absorb Fe²⁺ with a capacity of 299.3mg/g which is 6 times higher than that of graphite oxide. The adsorption properties of metal ions on graphene and the effects of various factors on the adsorption capacity were also investigated in detail. The research results suggest a novel material for developing highly efficient water purification materials for the developing economies.

Keywords: Graphene; Water purification; Heavy metal; Ionic liquids-assisted electrolysis

Influence of activated carbon characteristics on toluene and hexane adsorption: Application of surface response methodology by Mª Teresa Izquierdo; Alicia Martínez de Yuso; Raquel Valenciano; Begoña Rubio; Mª Rosa Pino (pp. 335-343).

► Adsorption capacity is maximized by optimization of surface characteristics of activated carbons. ► A compromise between physical and chemical characteristics is needed to maximize adsorption. ► High adsorption capacities for toluene and n-hexane are reached.The objective of this study was to evaluate the adsorption capacity of toluene and hexane over activated carbons prepared according an experimental design, considering as variables the activation temperature, the impregnation ratio and the activation time. The response surface methodology was applied to optimize the adsorption capacity of the carbons regarding the preparation conditions that determine the physicochemical characteristics of the activated carbons.The methodology of preparation produced activated carbons with surface areas and micropore volumes as high as 1128m²/g and 0.52cm³/g, respectively. Moreover, the activated carbons exhibit mesoporosity, ranging from 64.6% to 89.1% the percentage of microporosity. The surface chemistry was characterized by TPD, FTIR and acid–base titration obtaining different values of surface groups from the different techniques because the limitation of each technique, but obtaining similar trends for the activated carbons studied. The exhaustive characterization of the activated carbons allows to state that the measured surface area does not explain the adsorption capacity for either toluene or n-hexane. On the other hand, the surface chemistry does not explain the adsorption results either. A compromise between physical and chemical characteristics can be obtained from the appropriate activation conditions, and the response surface methodology gives the optimal activated carbon to maximize adsorption capacity. Low activation temperature, intermediate impregnation ratio lead to high toluene and n-hexane adsorption capacities depending on the activation time, which a determining factor to maximize toluene adsorption.

Keywords: Toluene adsorption; Hexane adsorption; Activated carbon; Surface response

Hydrophobic/hydrophilic switching on zinc oxide micro-textured surface by Myo Tay Zar Myint; Nithin Senthur Kumar; Gabor Louis Hornyak; Joydeep Dutta (pp. 344-348).

Display Omitted► Surface coverage less than 40% leads to hydrophobicity: theoretical and experimental approaches. ► Reversible wettability of zinc oxide microrods coated surface with ultraviolet and infrared irradiation. ► Potential application in designing surfaces with controlled wettability.Switchable wettability of zinc oxide (ZnO) microrod coated surfaces was controlled in two different ways: (1) by physical geometry (surface coverage area S_A: the area covered by solid) and (2) by irradiation with ultraviolet (UV) light followed by infrared (IR) or furnace heating. In the first approach, the threshold coverage area for achieving hydrophobic surfaces was found to be <40%, which is in good agreement with predicted values in the literature leading to a metastable Cassie–Baxter regime. The transformation of hydrophobic to hydrophilic surfaces was studied by alternating cycles of 3h exposure to ultraviolet ( λ_peak∼253nm) light followed by 1h of annealing or IR irradiation alone. Three different annealing temperatures (120°C, 200°C and 250°C) were utilized. Results of this work can be applied for designing surfaces with controlled wettability.

Keywords: Hydrophobic; Hydrophilic; Ultraviolet; Annealing; Zinc oxide; Microrod

Study of spatial homogeneity and nitridation of an Al nanopattern template with spectroscopic photoemission and low energy electron microscopy by B. Qi; S. Ólafsson; A.A. Zakharov; M. Göthelid; B. Agnarsson; H.P. Gislason (pp. 349-357).

► Spatial homogeneity and nitridation of a nanopattern template were studied by SPELEEM. ► The template exhibited a global inhomogeneity concerning the individual nanopatterns. ► The nanopatterns were diminished, more corrugated and faceted after nitridation. ► The nitridated Al nanodots were structurally ordered but differently orientated. ► The nitridation removed the fluorocarbon sidewalls of the nanopatterns.We report a study on the spatial homogeneity and nitridation of a nanopattern template using a spectroscopic photoemission and low energy electron microscopy. The template was composed of Al nanodots which were patterned into a SiO₂/Si(111) surface using e-beam lithography and reactive ion etching. The template exhibited a global inhomogeneity in terms of the local topography, Al composition and structure of the individual nanopatterns. After nitridation, the individual nanopatterns were diminished, more corrugated and faceted. The nitridated nanopatterns were structurally ordered but differently orientated. The nitridation effectively removed the fluorine contaminants by decomposition of the fluorocarbon sidewalls, resulting in the AlN nanopatterns and partially nitridated Si substrate surface outside the nanopattern domains.

Keywords: AlN; Nanopattern; Spectroscopic photoemission and low-energy electron microscopy; Nitridation

Copper phthalocyanine growth on hydrogen-terminated Si(100) surfaces: Contrasted molecular arrangements revealed by X-ray photoelectron studies by B. Ben Hamada; A. Akremi; I. Arbi; S. Menzli; J.-M. Themlin; L. Porte; C. Chefi (pp. 358-363).

► Copper phthalocyanine growth on hydrogen-terminated Si(100) surfaces. ► Molecular packing of CuPc onto hydrogen H–Si(100)-1×1 and H–Si(100)-2×1 surfaces. ► Structure of CuPc monolayer determined by X-ray photoelectron diffraction.Copper phthalocyanine (CuPc) molecules have been deposited under ultra-high vacuum on two kinds of hydrogen-terminated silicon surfaces, namely the H–Si(100)-2×1 and H–Si(100)-1×1 surfaces. The chemical and structural properties of these interfaces were investigated in situ by X-ray photoelectron spectroscopy and X-ray photoelectron diffraction (XPD), and low-energy electron diffraction. Results from X-ray photoelectron diffraction shed light on the growth mechanism of CuPc on these two substrates. At one monolayer coverage the growth mode was characterized by the formation of crystalline 3D nano-islands. The molecular packing deduced from these studies appears very close to the one of the bulk CuPc phase. Interestingly, the growth mode appears significantly different for the two surfaces. Indeed, 3D islands are formed by molecules aligned in a standing manner in the case of H–Si(100)-2×1, and in a flat-lying manner in the case of H–Si(100)-1×1.

Keywords: Copper phthalocyanine; Hydrogen passivated silicon surface; Molecule adsorption; XPD; XPS; LEED

Spontaneous and dense assemblies of nanoparticles within micro-channels by the bubble deposition method by Claire Costa-Coquelard; Joël Azevedo; Florence Ardiaca; Jean-Jacques Benattar (pp. 364-367).

Display Omitted► Specific nano-object deposition with the bubble deposition method. ► Influence of the patterned areas. ► Substrate and nano-object independent approach ordering of carbon nanotube films.We explore the potential of the bubble deposition method (BDM) for the specific monolayer organization of spherical and anisotropic NPs onto microstructured surfaces. These structurations cannot be only explained by the classical interactions between nano-objects and substrates but mainly by a combination of the drying front peculiar to the BDM with lithographically patterned substrates. Extended up to the integration of SWNT, this approach represents a simple, efficient, nano-object independent and potentially useful route for nanometric device realization.

Keywords: Bubble deposition method; Line tension; Patterned substrate; Nanoparticle organization; Carbon nanotubes

Incorporation of dithiooxamide as a complexing agent into cellulose for the removal and pre-concentration of Cu(II) and Cd(II) ions from natural water samples by A.O. Jorgetto; R.I.V. Silva; M.M. Longo; M.J. Saeki; P.M. Padilha; M.A.U. Martines; B.P. Rocha; G.R. Castro (pp. 368-374).

Display Omitted► A complexing agent was incorporated into the structure of commercial cellulose. ► The modified cellulose was used in the removal of metal species from river water. ► An enrichment factor of 50 enable the determination of Cu(II) and Cd(II) ions. ► A metal:ligand complex with a ratio of 1:2 allowed for the development of a possible binding structure. ► Method validation was performed through an analysis of certified water standards.The present study describes the incorporation of a complexing agent, dithiooxamide, into microcrystalline cellulose for use in the pre-concentration of Cu(II) and Cd(II) ions from aqueous samples. The FTIR spectrum of the adsorbent exhibited an absorption band in the region of 800cm⁻¹, which confirmed the binding of the silylating agent to the matrix. Elemental analysis indicated the amount of 0.150mmolg⁻¹ of the complexing agent. The adsorption data were fit to the modified Langmuir equation, and the maximum amount of metal species extracted from the solution, N_s, was determined to be 0.058 and 0.072mmolg⁻¹ for Cu(II) and Cd(II), respectively. The covering fraction ϕ, which was 0.39 and 0.48 for Cu(II) and Cd(II), respectively, was used to estimate a 1:2 (metal:ligand) ratio in the formed complex, and a binding model was proposed based on this information. The adsorbent was applied in the pre-concentration of natural water samples and exhibited an enrichment factor of approximately 50-fold for the species studied, which enabled its use in the analysis of trace metals in aqueous samples. The system was validated by the analysis of certified standard (1643e), and the adsorbent was stable for more than 20 cycles, thus enabling its safe reutilization.

Keywords: Modified cellulose; Pre-concentration; Natural water; Purification; Metal ions

Hydrothermal in situ preparation of TiO₂ particles onto poly(lactic acid) electrospun nanofibres by Kamal K. Gupta; Pradeep K. Mishra; Pradeep Srivastava; Mayank Gangwar; Gopal Nath; Pralay Maiti (pp. 375-382).

Display Omitted► Hydrolysed titanium precursor has been electrosprayed simultaneously on the continuous electrospun PLA nanofibres surface. ► Hydrothermal technique was used for in situ generation of TiO₂ particles on the surface of nanofibres. ► Investigated nanofibres hybrid is a potential material for UV protection and antimicrobial activity.The novel poly(lactic acid) (PLA)/TiO₂ hybrid nanofibres are produced via electrospinning technique. Hydrolysed titanium precursor has been electrosprayed simultaneously on the continuous electrospun PLA nanofibres surface. The adhered amorphous titania has been transformed into TiO₂ particle through hydrothermal treatment for different times. The phase structure has been worked out using XRD, FTIR, XPS and Raman spectroscopy. The predominant phase is anatase with a small extent of brookite phase after the hydrothermal treatment. The size and location of TiO₂ particle have been determined using SEM micrographs. The orderness of the PLA crystallites has been checked using XRD patterns before and after hydrothermal treatment. UV absorption capability of the titania coated nanofibres has been enhanced to a significant level. The antimicrobial activity of the hybrids has been verified using two different microorganisms (gram negative Escherichia coli and gram positive Staphylococcus aureus bacteria) and 70% reduction of antimicrobial activity has been reported.

Keywords: Poly(lactic acid) (PLA); Nanofibres; Titaniun dioxide (TiO; ₂; ); Electrospinning; Coating; Antimicrobial activity

Facile synthesis of large-scale Ag nanosheet-assembled films with sub-10nm gaps as highly active and homogeneous SERS substrates by Zhongbo Li; Guowen Meng; Ting Liang; Zhuo Zhang; Xiaoguang Zhu (pp. 383-390).

Display Omitted► Homogeneous Ag nanosheet-assembled films were prepared via galvanic cell reactions. ► The morphology of the films can be controlled in conjunction with photolithography. ► The Ag nanosheet-assembled films exhibit highly active and homogeneous SERS effect. ► The films can be used as reliable SERS substrates for rapid detection of PCBs.We report a facile low-cost synthetic approach to large-scale Ag nanosheet-assembled films with a high density of uniformly distributed sub-10nm gaps between the adjacent nanosheets on Si substrates via galvanic cell reactions. The distribution density of Ag nanosheets on substrates could be tailored by tuning the duration of the HF-etching and the concentration of citric acid in the solution. Furthermore, in conjunction with a conventional photolithography, highly uniform patterned Ag nanosheet-assembled structures with different morphologies can be achieved on Si substrates via galvanic-cell-induced growth. By using rhodamine 6G as a standard test molecule, the large-scale Ag nanosheet-assembled films exhibit highly active and homogenous surface-enhanced Raman scattering (SERS) effect and also show promising potentials as reliable SERS substrates for rapid detection of trace polychlorinated biphenyls (PCBs).

Keywords: Silver; Films; Galvanic cell; Surface-enhanced Raman scattering; Photolithography

Electrochemically deposited cobalt/platinum (Co/Pt) film into porous silicon: Structural investigation and magnetic properties by F.A. Harraz; A.M. Salem; B.A. Mohamed; A. Kandil; I.A. Ibrahim (pp. 391-398).

► Porous silicon (PSi) with pore sizes between 5 and 100nm was fabricated. ► Co/Pt magnetic film was electrochemically deposited into PSi template. ► Thermal annealing led to the crystallization of the films in the L1₀ ordered phase. ► The coercivity and magnetization were significantly enhanced. ► The current approach is beneficial for current and future PSi-based technologies.A nanostructured CoPt magnetic film was deposited from a single electrolyte into porous silicon layer by an electrochemical technique, followed by annealing at 600°C in Ar atmosphere during which the CoPt alloy was converted to L1₀ ordered phase. Porous silicon with pore diameter between 5 and 100nm was firstly fabricated by galvanostatic anodization of n-type silicon wafer in the presence of CrO₃ as oxidizing agent and ethanol or sodium lauryl sulfate as surfactants. The role of the surfactant on the produced pore size and morphology was investigated by means of UV–vis spectra. As-formed porous silicon was consequently used as a template for the electrodeposition of magnetic CoPt film. The phase formation, microstructure and the magnetic properties were fully analyzed by XRD, FE-SEM, EDS and VSM measurements. It was found that, upon annealing the coercivity was significantly increased due to the transformation to the L1₀ ordered structure. The saturation magnetization and remanence ratio were also found to increase, indicating no loss of Co content or oxidation reaction after the annealing. Results of synthesis and characterization of CoPt/porous silicon nanocomposite are addressed and thoroughly discussed.

Keywords: Porous silicon; Electrochemical deposition; Co/Pt film; Magnetic properties

Transmission electron microscopy and Raman characterization of copper (I) oxide microspheres composed of nanoparticles by Wenzhong Wang; Ya Tu; Lijuan Wang; Yujie Liang; Honglong Shi (pp. 399-403).

.Display Omitted► Raman spectroscopy of copper (I) oxide microspheres were investigated. ► Infrared active mode is greatly activated in Raman scattering spectrum. ► Infrared active mode shows up in Raman spectrum of copper (I) oxide microspheres. ► The defects existed in spheres could be responsible for the observed Raman property.The high-resolution transmission electron microscope and Raman spectroscopy were used to investigate the microstructures and Raman scattering property of copper (I) oxide microspheres composed of nanoparticles. High-resolution transmission electron microscope images indicate that the copper (I) oxide microspheres are composed of nanoparticles with random growth direction, indicating that there are many defects in microspheres. The Raman spectrum shows that infrared active mode, which must be odd parity and is Raman forbidden for bulk crystal due to its inversion symmetry, is activated and shows up in Raman scattering spectrum. On the basis of investigations of the microstructure features of copper (I) oxide microspheres, we attribute the appearance of IR active mode in Raman scattering spectrum to the breakdown of the symmetry of the lattice due to the presence of defects in the prepared copper (I) oxide microspheres as observed in HRTEM images.

Keywords: Nanostructures; Semiconductors; Crystal structure; Raman scattering

UV laser direct texturing for high efficiency multicrystalline silicon solar cell by Kwang-Ryul Kim; Tae-Hoon Kim; Hyun-Ae Park; Sun-Yong Kim; Sung-Hak Cho; Junsin Yi; Byoung-Deog Choi (pp. 404-409).

► “As-cut”, p-type, multicrystalline silicon wafers of 200μm thickness and 4.5cm×4.5cm. ► UV laser direct texturing and etching mask layer of SiN_x with 300nm. ► 1064 fiber laser texturing and etching mask layer of SiN_x with 300nm. ► Etching was essential to remove slag and damages from the laser. ► Densely-packed V-shaped textures were more effective for capturing photons than the U-shaped.Surface texturing is a technique used to increase light-trapping by forming certain structures on surface of a photovoltaic cell. We performed direct surface texturing using a 355nm UV laser to create V-shaped grooves on p-type, boron-doped multicrystalline silicon wafer of 200μm thickness. In addition, a 1064nm fiber laser was used to fabricate U-shaped grooves; this was done to determine the effect of light-trapping according to the shape of the structure. The samples were processed by 25% NaOH and acid solutions to remove slag after the direct texturing and isotropic etching. The reflectance and minority carrier lifetimes were measured to analyze the effects of the V-shaped groove and U-shaped groove. The V-shaped groove sample without the etching process showed 8.6% reflectance, while the sample etched for 4min with NaOH and 4.5min with isotropic acid after the laser texturing showed 13.2% reflectance. The minority carrier lifetime of the UV laser, V-shaped groove sample increased from 2.6μs to 20.6μs while that of the fiber laser, U-shaped groove sample increased from 2.3μs to 5.9μs. Etching was essential to remove slag and damages from the laser processes since these defects can induce inefficient electrical performance, as in long carrier lifetime. However, excessive etching flattens the surface and results in reduced effectiveness of light trapping. Consequently, the densely-packed V-shaped textures were more effective for capturing photons than the U-shaped texture.

Keywords: UV laser texturing; High efficiency solar cell; Multicrystalline silicon

Electrochemical behavior of anodized AA6063-T6 alloys affected by matrix structures by Yung-Sen Huang; Teng-Shih Shih; Chen-En Wu (pp. 410-418).

► Deformation after solution treatment introduced Al matrix to have deformation bands and few Si particles. ► Dislocations remained in the matrix lift up field potential and produce AlOOH oxide in the AAO film. ► The silicon-containing particles were found to trap in the AAO film. ► The silicon particles and the Al(OOH) oxide is significantly to influence the electrochemical behavior of AAO films.AA 6063 alloys were cold-rolled (CR) either before or after solution treatment (S) and then different samples were artificially aged (T6) to obtain different samples (CRST6 and SCRT6). The highest dislocation density was observed in the SCRT6 sample which also showed the lowest particle count among the three samples; ST6, CRST6 and SCRT6. Subsequently, all samples were anodized in a 15wt% sulfuric acid solution for different time spans to obtain anodic aluminum oxide (AAO) films. The anodized samples were further analyzed with X-ray Photoelectron Spectroscopy (XPS) analysis. We determined that the constituent phases in the AAO film were composed of hydrated amorphous alumina, hydrated oxide (Al(OH)₃) and oxyhydroxide (AlOOH) phases together with some silicon-containing particles trapped in the films on all samples. In the electrochemical test, the silicon-containing particles and hydrated Al(OH)₃ oxide that existed at the electrolyte/film (e/f) interface were found to inversely influence the corrosion resistance of the anodized samples.

Keywords: Cold rolled; XPS; Anodic aluminum oxide film; Al(OH); ₃; AlOOH; EIS

Temperature dependent capacity contribution of thermally treated anode current collectors in lithium ion batteries by Tae Kwon Kim; Xifei Li; Chunlei Wang (pp. 419-423).

► We studied the influence of the thermal treatment of current collectors on the energy capacity. ► Different current collectors show different thermal treatment effect on performance. ► The non-negligible capacity contribution is closely related to the treatment temperatures. ► Our results could be beneficial to designing battery architectures.Metal current collectors, offering a good connection between the active materials and the external circuit, is an important component in a rechargeable lithium ion battery. Some necessary thermal treatment in the battery fabrication and assembly procedure results in current collectors with some non-negligible reversible energy capacities; however, these energy capacities were negligible in the previous references. In this research, for the first time, we investigated the influence of the thermal treatment of current collectors (such as copper foil and stainless steel disk) on energy capacities. Our results indicate that different current collector materials have different thermal treatment effects on their electrochemical performance. The non-negligible capacity contribution is closely related to the treatment temperature.

Keywords: Current collectors; Lithium ion battery; Thermal treatment; Energy capacity; Electrochemical performance

First-principles investigation of H₂O on HfO₂ (110) surface by Lu Li; Xin Huang; Yong-Fan Zhang; Xin Guo; Wen-Kai Chen (pp. 424-432).

Display Omitted► Adsorption energies of H₂O on HfO₂ at different coverages are investigated. ► Dissociation adsorption is more favorable than molecular one at low coverage. ► Three distinct adsorption modes present for H₂O adsorbed on HfO₂ (110) surface. ► HfO₂ (110) surface is a good candidate for water splitting.As the water to be an important precursor mater in atomic layer deposition (ALD) of preparation of HfO₂ thin film, water-gas shift (WGS) reaction and heterogeneous catalysis, surface hydroxyl groups played a vital role as the reactive species that remain on the surface. First-principle calculation based on density functional (DFT) approach and generalized gradient approximation (GGA) have been utilized to investigate the molecular and dissociative adsorption of water molecule on the stoichiometric cubic HfO₂ (110) surface with different sites at different coverages. The calculation employed slab geometry and periodic boundary condition with partial relaxation of atom position. Adsorption geometries, Mulliken population charges and density of states for HfO₂H₂O, HfO₂OH, HfO₂O and HfO₂H at the coverage of 0.5ML were also calculated. It was found that the adsorption energies varied a little as coverages increased, and the most favorable configuration of H₂O on HfO₂ surface was corresponding to the coordination of H₂O via its oxygen with the surface (surface Hf atom). It was also confirmed that the coordination interaction and hydrogen bonding were the main contributions in dissociative adsorption process. For both molecular and dissociative adsorption, it has been elucidated that the surface hafnium played a key role as the active site. For dissociation reaction H₂O (ads)→H (ads)+OH (ads), the barrier energy calculated to be 17.3kJ/mol, whereas, the second step dehydrogenation reaction OH (ads)+H (ads)→O (ads)+2H (ads), hardly occurred on this surface because of the high barrier energy 208.3kJ/mol.

Keywords: Hafnia; Water; Adsorption; Density functional theory; Dissociation

Effect of the surface oxygen groups on methane adsorption on coals by Shixiong Hao; Jie Wen; Xiaopeng Yu; Wei Chu (pp. 433-442).

► We modified one coal with H₂O₂, (NH₄)₂S₂O₈ and HNO₃ respectively, to prepare coal samples with different surface properties. ► The oxygen groups on coal surface were characterized by XPS. ► The textures of the coal samples were investigated by N₂ adsorption at 77K. ► The adsorption behaviors were measured by volumetric method. ► There was a negative correlation between methane saturated adsorption capacity and the O_total/ C_total.To investigate the influence of surface oxygen groups on methane adsorption on coals, one bituminous coal was modified with H₂O₂, (NH₄)₂S₂O₈ and HNO₃ respectively, to prepare coal samples with different surface properties. The oxygen groups on coal surface were characterized by X-ray photoelectron spectroscopy (XPS). The textures of the coal samples were investigated by N₂ adsorption at 77K. Their surface morphologies were analyzed by scanning electron microscopy (SEM). The methane adsorption behaviors of these coal samples were measured at 303K in pressure range of 0–5.3MPa by volumetric method. The adsorption data of methane were fitted to the Langmuir model and Dubinin–Astakhov (D–A) model. The fitting results showed that the D–A model fitted the isotherm data better than the Langmuir model. It was observed that there was, in general, a positive correlation between the methane saturated adsorption capacity and the micropore volume of coals while a negative correlation between methane saturated adsorption capacity and the O_total/ C_total. The methane adsorption capacity was determined by the coal surface chemistry when the microporosity parameters of two samples were similar. Coal with a higher amount of oxygen surface groups, and consequently with a less hydrophobic character, had lower methane adsorption capacity.

Keywords: Coal; Surface oxygen groups; Methane; Adsorption

Preparation and characterization of fully separated gold nanowire arrays by Jakub Siegel; Johannes Heitz; Alena Řezníčková; Václav Švorčík (pp. 443-447).

Display Omitted► Synthesis of laterally ordered separated Au nanowire arrays on PET is presented. ► The process is based on evaporation of Au on PET template in glancing angle geometry. ► Resulting nanowires are organized in parallel arrays of approximately 2500 wires.We reported on the development of an unconventional approach for the physical synthesis of laterally ordered self-organized arrays of well-separated metallic nanowires supported on nanostructured dielectric templates. The method, combining nanoscale patterning of the polyethylene terephthalate substrate by polarized light of excimer laser with glancing angle deposition of the gold, provides an interesting alternative to lithography-based nanopatterning approaches. Separation of individual nanowires is manifested by anisotropy of their electrical properties. Focused ion beam equipped scanning electron microscopy analysis revealed that the resulting nanowires were organized in parallel arrays of approximately 2500 wires with an average length of about 1000μm and uniform width of about 150nm.

Keywords: Template deposition; Gold nanowires; Electrical properties; Chemical composition

Transparent and conductive electrodes combining AZO and ATO thin films for enhanced light scattering and electrical performance by C. Guillén; J. Montero; J. Herrero (pp. 448-452).

► Transparent Al:ZnO (AZO) and Sb:SnO₂ (ATO) films were sputtered on glass substrates. ► Optical scattering or haze is related to the surface roughness determined by AFM. ► ATO/AZO bilayers combine high optical scattering and electrical conductivity values.Al:ZnO (AZO) and Sb:SnO₂ (ATO) thin films have been deposited by DC sputtering on soda lime glass (SLG) substrates. The preparation conditions were adjusted to obtain transparent films with high conductivity for AZO and high texture for ATO. Then, the combination of AZO and ATO thin films has been tested to enhance the optical scattering and the electrical performance. The structure, morphology, optical, and electrical properties have been analyzed for SLG/AZO, SLG/ATO and SLG/ATO/AZO samples. The surface texture has been characterized optically by the haze parameters for transmittance and reflectance ( H_T and H_R), which have been related to the root mean square roughness for each sample. Some increase of the electrical resistance is obtained for the AZO films deposited on rough ATO underlayers as compared with analogous AZO grown directly on the smooth SLG substrate. Nevertheless, ATO/AZO bilayers have allowed to achieve better electrical conductivity than ATO and greater optical scattering than isolated ATO or AZO films. In this way, average haze values of H_T=30% and H_R=72%, together with sheet resistance of 20Ω/sq. have been obtained by combining 150nm-thick ATO and 800nm-thick AZO films.

Keywords: Transparent conducting oxides; Multilayer electrode; Optical scattering; Surface roughness

Improved mechanical properties of solution-cast silicone film reinforced with electrospun polyurethane nanofiber containing carbon nanotubes by Leonard D. Tijing; Chan-Hee Park; Seung-Ji Kang; Altangerel Amarjargal; Tae-Hyung Kim; Hem Raj Pant; Han Joo Kim; Dong Hwan Lee; Cheol Sang Kim (pp. 453-458).

Display Omitted► We have prepared a composite film by electrospinning and solution-casting. ► Electrospun CNT/PU nanofibers were used as nanofillers for silicone film. ► There was an increase in tensile strength of 226% when CNT/PU mat was incorporated. ► Simultaneous increase in rigidity and ductility was achieved for CNT/PU–silicone film.In this study, we describe the enhancing ability of electrospun polyurethane (PU) nanofibers containing carbon nanotubes (CNTs) as nanofillers for silicone film in improving the physico-mechanical properties of the composite material. We prepared the samples combining two simple techniques: solution casting and electrospinning. Neat PU nanofibers alone are good reinforcing materials but the presence of CNTs inside the PU nanofibers has drastically improved the mechanical properties of the silicone composite film. The silicone film increased its tensile strength by 226% and its tensile modulus by more than 14-fold when CNT/PU nanofibers were incorporated.

Keywords: Electrospinning; Solution casting; Silicone; Polyurethane; Carbon nanotube; Nanofiber

Effect of rapid thermal annealing on the compositional ratio and interface of Cu(In,Ga)Se₂ solar cells by XPS by D.S. Chen; J. Yang; F. Xu; P.H. Zhou; H.W. Du; J.W. Shi; Z.S. Yu; Y.H. Zhang; Brian Bartholomeusz; Z.Q. Ma (pp. 459-463).

► RTA treatment makes the compositional ratio of Al and Zn increase. ► RTA treatment improves the content of Se in CIGS thin film. ► The ratio and shape character of Cu/(In+Ga) and Ga/(In+Ga) are further optimized. ► Compared with un-annealed sample, the absolute efficiency improvement is about 1.2%.The effect of rapid thermal annealing (RTA) on the compositional ratio of atoms and interfacial zone of Cu(In,Ga)Se₂ (CIGS) solar cells was systematically studied using X-ray photoelectron spectroscopy. The RTA treatment induced the diffusion of Al, Zn, and Se atoms, which increased the compositional ratio of these atoms in the corresponding layer. The ratio and characteristics of Cu/(In+Ga) and Ga/(In+Ga) were further modulated to attain higher efficiency in the devices. Furthermore, the width of the interfacial zone decreased at the Mo/CIGS interface because the diffusion depth of the Se atoms contracted from 1300nm to 1200nm. After RTA treatment, the absolute efficiency of the CIGS solar cells was enhanced by 1.2%. Our results suggest that RTA treatment reduces series resistance, optimizes the position of the minimum bandgap in the CIGS thin film, and improves the crystallinity of the CIGS thin film, which is responsible for the improvement in conversion efficiency.

Keywords: Cu(In,Ga)Se; ₂; Solar cell; Compositional ratio; Rapid thermal annealing; Interface

Study of the aluminum doping of zinc oxide films prepared by atomic layer deposition at low temperature by Pascal Genevée; Frederique Donsanti; Gilles Renou; Daniel Lincot (pp. 464-469).

► This paper shows a possibility to improve the aluminum doping of atomic layer deposited zinc oxide at low temperature. ► The influence of purge lengths on the properties of the material is evidenced. ► Changes in the optical properties of the material induced by the aluminum doping are studied.This study presents the effect of purge pulses conditions on the electrical and optical properties of zinc oxide films doped with aluminum and grown by ALD at low temperature (160°C). Undoped ZnO films showed a clear improvement of the carrier concentration when purges were lengthened, which suggests that this purge lengthening causes a higher defect related doping. It was also showed that this purge lengthening leads to a further increase of the carrier concentration in the case of ZnO:Al films attributed to a better spatial repartition of the Al dopants in the film. The evolution of optical properties was also studied and compared to the electrical properties highlighting free carrier absorption and a Burstein–Moss shift. An abnormal modification of the optical properties was observed when the aluminum content in the film was increased.

Keywords: Atomic layer deposition; Zinc oxide; Low temperature; Aluminum-doped zinc oxide

Water effect on the surface morphology of TiO₂ thin film modified by polyethylene glycol by Sheng-Hung Wang; Kuo-Hua Wang; Yong-Ming Dai; Jih-Mirn Jehng (pp. 470-475).

► TiO₂ porous thin film is fabricated using polyethylene glycol 6000 (PEG-6000) as a template. ► The water molecules provide locations for the aggregation of PEG-6000, and it is demonstrated by the phase diagrams of AFM. ► The water content has an influence on the surface structure and the thin film thickness. ► The TiO₂ thin film has the best photocatalytic activity when the ratio of water to Ti precursor is 2.Water effect on the surface morphology of TiO₂ thin film was investigated by using PEG-6000 as a template to form the porous structure. The porous TiO₂ thin films were characterized by thermo-gravimetric analysis (TGA), X-ray diffraction (XRD), n&k Analyzer, UV–vis spectrophotometer, field-emission scanning electron microscopy (FE-SEM), and atomic forced microscopy (AFM) as a function of water content in the preparation of TiO₂ thin film. The various water contents result in the TiO₂ thin films possessing different surface structures, grain sizes, and thicknesses. The grain sizes were varied with changing the water content, and the thickness increased with increasing water content due to the enhancement of the cross-linking speed. In addition, the cratered surface structure transformed into cracked surface structure upon the water content beyond stoichiometric quantity because the excess water causes the aggregation of polyethylene glycol (PEG-6000). The photocatalysis has been performed by the degradation of methyl blue with corresponding structural characteristics of the TiO₂ thin film. The best photocatalytic activity has been obtained when the ratio of water to titanium precursor is equal to 2 referred as TiO₂-W2.

Keywords: TiO; ₂; thin film; Sol–gel; PEG-6000; Photocatalytic activity

Enhanced photoelectrochemical and photocatalytic performance of single-crystalline anatase TiO₂ (101) nanobelts arrays originating from nanotubes arrays by Qinghua Chen; Huiling Liu; Yanjun Xin; Xiuwen Cheng; Junjing Li (pp. 476-484).

Single-crystalline anatase TiO₂ (101) nanobelts arrays originating from nanotubes arrays were successfully prepared via simple anodization. This structure gives rise to faster electron mobility and less electron-trapping sites in the bulk, thereby effectively improving the separation efficiency of photogenerated charge carriers and photocatalytic activity. Thus, it can be utilized for solar energy conversion and environmental remediation.Display Omitted► Anatase TiO₂ nanobelts arrays originating from nanotubes arrays were prepared. ► TiO₂ nanobelts arrays exhibit higher PEC and PC properties. ► The performance enhanced mechanism was discussed in detail. ► It can be utilized for solar energy conversion and environmental remediation.TiO₂ photocatalysts with high photocatalytic activity are potentially applied to degrade pollutants, split water and transform solar energy. Herein, TiO₂ nanobelts (TiO₂ NB) arrays originating from nanotubes arrays were successfully prepared via simple anodization. The surface morphology, structure, elemental composition, photoluminescence spectra (PL), photoelectrochemical (PEC) properties and photocatalytic activity of the resulting samples were investigated. The results show that as-prepared TiO₂ NB arrays exhibited significant enhancement in separation efficiency of photogenerated electrons (e⁻) and holes (h⁺) pairs and then in photocatalytic activity under simulative solar irradiation compared with TiO₂ nanotubes (TiO₂ NT) arrays, which could be attributed to the following aspects: (i) specific belt-like morphology leads to higher accessibility of TiO₂ NB arrays for reactants and more active sites on the surface of TiO₂ NB; (ii) single-crystalline anatase phase structure gives rise to faster electron mobility and less electron-trapping sites in the bulk; and (iii) exposed crystal face (101) yields an enhanced reactivity with molecular O₂, facilitating the trapping of photogenerated electrons and generation of superoxide radical. Otherwise, this TiO₂ NB arrays overcome the deficiency of filtering separation from water and exhibit excellent photocatalytic stability, thus it is promising to be applied in pollutants elimination and photocatalytic decomposition of water.

Keywords: Photoelectrochemical and photocatalytic performance; TiO; ₂; nanobelts arrays; Accessibility; Single-crystalline anatase; Exposed crystal face

Structural and mechanical properties of the coral and nacre and the potentiality of their use as bone substitutes by Samir Hamza; Noureddine Slimane; Zitouni Azari; Guy Pluvinage (pp. 485-491).

► The structural and mechanical properties of coral and nacre used as bone substitute. ► The chemical composition of the nacre and coral are qualitatively similar to a bone. ► The percentage of porosity influences significantly the mechanical properties. ► A stress-life curve revealed an endurance limit to coral and nacre.The main objective of this work is to develop resistant compact material samples with different porosities from coral and nacre adapted to the filling of bone cavities. The characterization of materials was conducted using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and laser granulometry. The micro-hardness and the influence of porosity on the mechanical behavior of these biomaterials under compression as well as three-points bending tests were also assessed. Both materials showed similar particles size ranging from 50 to 100μm in diameter, distributed according to the Gauss curve. The modal particle size, the median D₅₀ and D₉₀– D₁₀ are the most important parameters which allow for the distinction between coral and nacre samples. The two biomaterials showed a micro hardness (138–167HV for coral and 261–340HV for nacre) higher than that of bovine bones (55–70HV). The maximum compression stresses were 32.82MPa for coral and 37.06MPa for nacre at 50% of porosity. S–N curve with ASME format is constructed to predict the fatigue life extended from 10¹ to 10⁶ cycles, which reveals an endurance limit at a compression stress ratio of about 10.

Keywords: Coral; Nacre; Calcium carbonate; Mechanical properties; Fatigue

Surface properties of pillared acid-activated bentonite as catalyst for selective production of linear alkylbenzene by Hossein Faghihian; Mohammad Hadi Mohammadi (pp. 492-499).

► New catalysts were prepared by acid treatment and pillaring of bentonite. ► Treatments generated materials with different surface characteristics. ► Specific surface area, pore volume and acidity of acid-activated pillared clay were enhanced compared to the parent clay. ► More than 98% of conversion was achieved in the alkylation of benzene by 1-decene by acid-activated Al-pillared bentonite. ► Catalysts exhibited desirable selectivity toward linear alkylbenzene (LAB).Acid-activated and pillared montmorillonite were prepared as novel catalysts for alkylation of benzene with 1-decene for production of linear alkylbenzene. The catalysts were characterized by X-ray diffraction, FT-IR spectroscopy, N₂ adsorption isotherms, temperature programmed desorption of NH₃, scanning electron microscopy and elemental and thermal analysis techniques. It was found that acid-activation of clays prior to pillaring increased the porosity, total specific surface area, total pore volume and surface acidity of the catalysts. Optimization of the reaction conditions was performed by varying catalyst concentration (0.25–1.75wt%), reactants ratio (benzene to 1-decene of 8.75, 12 and 15) and temperature (115–145°C) in a batch slurry reactor. Under optimized conditions more than 98% conversion of 1-decene, and complete selectivity for monoalkylbenzenes were achieved.

Keywords: Al-pillared acid-activated clay; Surface properties; BET; Heterogeneous catalysis; Linear alkylbenzene

Structure and conformation of poly(ethylene glycol) in confined space of montmorillonite by Shipeng Zhu; Jinyao Chen; Huilin Li; Ya Cao (pp. 500-506).

A possible structure of intercalated PEG in confined space of MMT.Display Omitted► Structure and conformation of PEG chains in confined space of MMT were studied. ► PEG chains form monolayer and double layers in MMT. ► Saturation ratios of PEG to Na-MMT and OMMT are deduced. ► A possible model of PEG intercalated MMT is proposed.The structure and conformation of poly(ethylene glycol) (PEG) chains in the confined space of montmorillonite (MMT) were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). A series of PEG/MMT hybrids were synthesized utilizing solution intercalation. Intercalated hybrids with monolayer and double layers of PEG chains were obtained both in Na-MMT and OMMT (DK1). However, the hydrophobic PEG chains cannot intercalate into the interlayer space of OMMT (DK4) due to the strong hydrophilic properties of DK4. There is a saturation ratio when PEG intercalated into the interlayer space of MMT. The deduced saturation ratios of PEG to Na-MMT and DK1 are 0.26 and 0.24, respectively. The structure and conformation of intercalated PEG chains exhibit different characteristics from those of the neat polymer, even more disorder in melting state. According to the results of XRD and FTIR, the structure and conformation of PEG chains in OMMT (DK1) are very similar to Na-MMT. Moreover, a possible model of PEG intercalated MMT is proposed. All PEG chains are intercalated into the interlayer spaces of MMT and form a disorder phase when PEG content is not saturated. In the cases of PEG: MMT=1:10 or 3:10 in weight, the polymer chains form one or two polymer layers. A wider monolayer form when the weight ratio of PEG/MMT is 0.2.

Keywords: Poly(ethylene glycol); Montmorillonite; Structure; Conformation; Confined space

Adsorption behavior of glycidoxypropyl-trimethoxy-silane on titanium alloy Ti–6.5Al–1Mo–1V–2Zr by Jian-hua Liu; Zhong-wei Zhan; Mei Yu; Song-mei Li (pp. 507-515).

► The adsorption isotherm of glycidoxypropyl-trimethoxy-silane (GTMS) on a titanium alloy was found fitting Temkin isotherm by XPS. ► From an electrochemical point of view, the in situ adsorption process of GTMS molecules agreed with XPS results. ► At 30°C, the adsorption of GTMS molecules is spontaneous, and follows a chemisorption-based mechanism.The adsorption behavior of glycidoxypropyl-trimethoxy-silane (GTMS) on titanium alloy Ti–6.5Al–1Mo–1V–2Zr was investigated by using X-ray photoelectron spectroscopy (XPS), Tafel polarization test, and electrochemical impedance spectroscopy (EIS). From the XPS results, it was found that the silane coverage on the titanium surface generally increased with GTMS concentration, with a slight decrease at concentration of 0.1%. Based on the relationship between isoelectronic point (IEP) of titanium surface and the pH values of silane solutions, adsorption mechanisms at different concentrations were proposed. The surface coverage data of GTMS on titanium surface was also derived from electrochemical measurements. By linear fitting the coverage data, it revealed that the adsorption of GTMS on the titanium alloy surface at 30°C was of a physisorption-based mechanism, and obeyed Langmuir adsorption isotherm. The adsorption equilibrium constant ( K_ads) and free energy of adsorption process (Δ G_ads) were calculated to elaborate the mechanism of GTMS adsorption.

Keywords: Glycidoxypropyl-trimethoxy-silane (GTMS); Titanium alloy; Adsorption isotherm; XPS; Tafel; EIS

Tribological characteristics of electroless Ni–P–MoS₂ composite coatings at elevated temperatures by Zhen Li; Jingbo Wang; Jinjun Lu; Junhu Meng (pp. 516-521).

► Uniform Ni–P–MoS₂ composite coatings are deposited by electroless plating. ► Friction coefficient of composite coating decreases with the increase of temperature. ► Formation of lubricious oxide film leads to excellent tribological property.Ni–P–MoS₂ composite coatings were deposited on AISI-1045 steel plate by electroless plating followed by a heat treatment at 300°C for 2h. The high-temperature tribological characteristics of the composite coatings were evaluated under dry sliding conditions in a tribometer with ball-on-disk configuration. The effect of the co-deposition of MoS₂ on the friction and wear behaviors of composite coatings at elevated temperature was investigated. Scanning electron microscopy was used to determine the morphology of the worn surface of composite coating. The chemical states of some typical elements on the worn surfaces were determined by X-ray photoelectron spectroscope. The results indicate that friction coefficient of the composite coatings decreases with the increase of test temperature up to 500°C, and the best tribological properties of Ni–P–MoS₂ composite coatings are achieved at 400°C. The worn surface of Ni–P–MoS₂ composite coatings are characterized by mild scuffing and deformation. The improvement of tribological properties of the composite coatings was attributed to the formation of the lubricious oxide film composed of oxides of Ni and Mo at high temperatures. With the test temperature increasing to 600°C, the tribological properties of the composite coating begin to deteriorate due to softening of the coating.

Keywords: Electroless; Ni–P–MoS; ₂; composite coating; Tribological characteristic; Lubricious oxide film; High-temperature

Effects of CdZnTe buffer layer thickness on properties of HgCdTe thin film grown by pulsed laser deposition by M. Liu; D. Bi; B.Y. Man; D.M. Kong; X.Y. Xu (pp. 522-526).

► We prepared HgCdTe thin film on CdZnTe/Si(111) substrates by pulsed laser deposition (PLD). ► The effects of CdZnTe buffer layer thickness which varied with the deposition time on the crystalline, morphology and other properties of HgCdTe thin films were analysed. ► The reasons about the variety of the crystalline quality and the composition of the HgCdTe epitaxial layer with the increase of the deposition time of the buffer layer were analysed.HgCdTe thin films have been deposited on CdZnTe/Si(111) substrates by pulsed laser deposition (PLD). A Nd:YAG pulsed laser with a wavelength of 1064nm was used as laser source. The effects of CdZnTe buffer layer thickness which varied with the deposition time in the range from 3 to 15min on the crystalline, morphology and other properties of HgCdTe thin films were analysed. The results show that the crystalline quality and the composition of the HgCdTe epitaxial layer change with the increase of the deposition time of the buffer layer. The CdZnTe buffer layer with a proper deposition time can improve the quality of HgCdTe films, and the HgCdTe films deposited on the CdZnTe buffer layer with the deposition time of 5min exhibit the best crystalline quality and smooth surface in our experiment.

Keywords: PLD; HgCdTe thin films; CdZnTe buffer layer; Deposition time of buffer layer

Fabrication of biomimetic hydrophobic films with corrosion resistance on magnesium alloy by immersion process by Yan Liu; Guolong Lu; Jindan Liu; Zhiwu Han; Zhenning Liu (pp. 527-532).

► We have developed a facile and simple method of creating a hydrophobic surface on a magnesium alloy by an immersion process at room temperature. ► The distribution of the micro-structure and the roughness of the surface play critical roles in transforming from hydrophilic to hydrophobic. ► The hydrophobic coatings possess better corrosion resistance than magnesium alloy matrix.Biomimetic hydrophobic films of crystalline CeO₂ were prepared on magnesium alloy by an immersion process with cerium nitrate solution and then modified with DTS (CH₃(CH₂)₁₁Si(OCH₃)₃). The CeO₂ films fabricated with 20-min immersion yield a water contact angle of 137.5±2°, while 20-min DTS treatment on top of CeO₂ can further enhance the water contact angle to 146.7±2°. Then corrosion-resistant property of these prepared films against NaCl solution was investigated and elucidated using electrochemical measurements.

Keywords: Hydrophobic; Immersion process; Magnesium alloy; Biomimetic film

Influence of the sputtering reactive gas on the oxide and oxynitride LaTiON deposition by RF magnetron sputtering by Y. Lu; C. Le Paven-Thivet; R. Benzerga; L. Le Gendre; A. Sharaiha; F. Tessier; F. Cheviré (pp. 533-537).

► We report on the deposition of perovskite La₂Ti₂O₇ and LaTiO₂N films. ► The films were grown by reactive sputtering from an oxynitride target. ► The presence of residual water allowed the deposition of oxide films. ► Abrupt changes in deposition rate and nitrogen contents of films were observed.Perovskite LaTiON thin films have been grown by radio frequency magnetron sputtering from a LaTiO₂N target. With a very low base pressure in the deposition chamber, two types of films can be obtained: colored oxynitride LaTiO₂N films when nitrogen gas is introduced during sputtering or black N-doped LaTiO₃ films when deposition is performed in pure argon. On SrTiO₃ (001) substrate heated at 750°C, LaTiO₂N films are epitaxially grown, while N:LaTiO₃ films are poorly crystallized. With a higher base pressure in the deposition chamber, transparent La₂Ti₂O₇ films are produced. They are (012) textured on (001) SrTiO₃ substrate. As observed during the reactive sputtering of metallic targets, the evolution of the deposition rate and the nitrogen content in films according to the N₂ percentage in the plasma is abrupt.

Keywords: Oxynitride; Thin films; RF sputtering; Epitaxy; Reactive gas

Infrared transmissive and rain-erosion resistant performances of GeC/GaP double-layer thin films on ZnS substrates by Li Yang-Ping; Wang Ning; Che Xing-Sen; Chen Hai-Bo; Liu Zheng-Tang (pp. 538-544).

► GeC/GaP films were deposited on ZnS substrates and the average transmittance of GeC/GaP/ZnS over 8–11.5μm rises compared with that of ZnS. ► Rain erosion test was performed and the damage to GeC/GaP and ZnS were discussed. ► Results show that GeC/GaP films can well protect ZnS from rain erosion.GeC/GaP double layer films were deposited on ZnS substrates with radio frequency magnetron sputtering for infrared antireflective and protective purposes. Infrared transmissive and rain erosion resistant performances of the films were studied. Results show that the refractive index of the GaP films is similar to that of bulk GaP and a low refractive index of about 1.78 was obtained for GeC films. The average transmittance of GeC/GaP/ZnS over 8–11.5μm rises by more than 4% in comparison with that of the uncoated ZnS. After rain erosion, some parts of the GeC layer were sputtered off, with discrete pits formed and the sub-layer GaP film exposed on the bottom of the pits. When the thickness of the GaP film was small, cracks were created by rain erosion on the surface of the exposed GaP films; yet the cracks disappeared with increasing the thickness of the sub-layer GaP. The damages to the uncoated ZnS surface caused by rain erosion are cracks. The lateral border of the cracks was peeled with increasing the rain erosion time. Infrared transmittance of both coated and uncoated ZnS fell after rain erosion, but the fall in infrared transmittance of uncoated ZnS was larger than that of coated ZnS, indicating the GeC/GaP films can protect the ZnS substrate from rain erosion.

Keywords: Thin film; Germanium carbon; Gallium phosphide; Infrared antireflection; Rain erosion

Effect of critical plasma spray parameter on complex permittivity and microstructure by plasma spraying Cr/Al₂O₃ coatings by Dong Zhao; Fa Luo; Wancheng Zhou; Dongmei Zhu (pp. 545-551).

► Deposit the Cr/Al₂O₃ coatings for microwave absorbing application. ► We study the effects of CPSP on the complex permittivity. ► Increasing CPSP content enhance the complex permittivity. ► The reflection loss varies with changes of coatings thickness and Fe amount.In this paper, Cr/Al₂O₃ coatings formed via a plasma spray approach with different critical plasma spray parameters using Al₂O₃ and Cr powder feeds were prepared. The effects of CPSP on the phase composition, microstructure, complex permittivity, porosity and adhesive strength of the coatings were investigated. The microstructure and phase composition of coatings were examined using scanning electron microscope (SEM) and X-ray diffraction (XRD). XRD analysis reveal that Cr, γ-Al₂O₃ and α-Al₂O₃ are found in all the coatings, and percentage of γ-Al₂O₃ is increased due to complete melting of the particles and their consequent rapid solidification. The experimental results have shown that the CPSP condition has significant influence on the microstructure and complex permittivity of the coatings. Both the real part (ɛ′) and imaginary part (ɛ″) of relative complex permittivity are increased with improving the CPSP condition.

Keywords: Plasma spray; Complex permittivity; Critical plasma spray parameters; Cr/Al; ₂; O; ₃; coatings

Onset of shadowing-dominated growth of Ag films in glancing angle deposition: Kinetic Monte Carlo simulation by Shuhan Chen; Jingshu Liang; Yunjie Mo; Difan Luo; Shaoji Jiang (pp. 552-556).

► The nanorods grow aslant due to shadowing anisotropy but vertically due to shadowing isotropy. ► The growth exponents in normal deposition and GLAD are found similar in the early stages. ► We demonstrate that shadowing overpower smoothing effects at certain thickness. ► Transition from two dimensional to 3D islanded growth under GLAD is demonstrated. ► The critical rotate of the nanorods just vertical to the substrate has been revealed.A three-dimensional (3D) kinetic Monte Carlo simulation was performed for the growth evolution of Ag films during glancing angle deposition (GLAD). Under the GLAD conditions, we demonstrate that without substrate rotation the nanorods are grown aslant due to shadowing anisotropy, while with the rapid substrate rotation the nanorods are grown vertically aligned due to shadowing isotropy. Good agreement of growth trends between simulations and experiments has been achieved. In the case of substrate rotation, the critical rotate rate of nanorods just vertical to the substrate has been found. The growth exponent evolutions of Ag films in normal and glancing angle depositions are found similar in the very early stages of growth. The diverging of growth exponents with film height increasing indicates that shadowing instabilities overpower the smoothing effects associated with surface diffusion. Furthermore, we demonstrate the transition from two-dimensional to 3D islanded growth under the condition of high glancing angle deposition.

Keywords: Shadowing-dominnated growth; Glancing angle deposition; Kinetic Monte Carlo simulation

Research on manganese oxide catalysts surface pretreated with non-thermal plasma for NO catalytic oxidation capacity enhancement by Kai Li; Xiaolong Tang; Honghong Yi; Ping Ning; Ying Xiang; Jiangen Wang; Chi Wang; Xiao Peng (pp. 557-562).

The NO catalytic oxidation activity of MnO x/2.9 is much stronger than those of catalysts with other pre-treatment methods. The NO conversion of MnO x/2.9 was over 79% at 125(C, even at 50°C and 100°C it achieved 44% and 69%, respectively.Display Omitted► Non-thermal plasma surface treatment made MnO x catalysts exhibit high NO catalytic activity. ► MnO x/2.9 catalyst yielded 79% NO conversion at 125°C. ► Treatment SIE has significant influence on NO catalytic activity of catalysts. ► Change of functional groups during NTPST improved the catalytic activity.Catalytic oxidation of NO at low temperature is a potentially competitive method, and the catalyst's preparation and modification are crucial for NO catalytic oxidation. Non-thermal plasma surface treatment (NTPST) has been applied to manganese oxide (MnO x) catalysts for catalytic oxidation of nitrogen oxide (NO) in the presence of O₂. The plasma-treated MnO x catalyst presents excellent low-temperature catalytic activity in the process of NO oxidation. And the NO conversion was 79% at 125°C with a space velocity of 30,600h⁻¹. To clarify the plasma effect, the catalysts were characterized by XRD, SEM and EDS. The enhanced performance of MnO x catalysts as pretreated by plasma was ascribed to two effects: (1) the etching and sputtering on catalyst's surface with the treatment of plasma can improve the dispersion of catalysts; (2) EDS results revealed that the NTPST could increase the K and O content on the catalyst's surface which contributed to a higher activity for NO catalytic oxidation. It demonstrates that the NTPST is an effective way to pretreat catalyst for NO removal.

Keywords: Non-thermal plasma; Surface treatment; Catalytic oxidation; Nitrogen oxide; Manganese oxide

Atomistic simulation for the γ′-phase volume fraction dependence of the interfacial behavior of Ni-base superalloy by Xiyuan Yang; Wangyu Hu; Xingming Zhang (pp. 563-569).

► The stability of the Ni-base superalloy with (60–70)% γ′-VF is the most excellent. ► The interface energy is independent of the γ′-VF. ► The critical thickness of the ITR is about 1.7nm at 300K. ► The strengthening effect of the γ′-VFphase is the most obvious for NBSA with (60–70)% γ′-VFVF.By means of molecular dynamics (MD) and the modified analytic embedded-atom method (MAEAM), we investigate the effect of the γ′-phase volume fraction (γ′-VF) on the apparent interface energy, the critical thickness of the interface transition region (ITR) and the binding mechanism of the γ/γ′ interface. The results indicate that the apparent interface energy increases linearly with the ITR width increasing. Then, by extrapolating the ITR widthΔl to zero, we can obtain the interface energy which is equal to the limiting value of the apparent interface energy. The volume fraction of the γ′-phase has no influence on the interface energy and the critical thickness of the ITR. The interface energy is in reasonable agreement with the previous results and the critical value of the ITR width is about 1.7nm which also agrees well with the experimental and theoretical ones. Finally, the γ′-VF dependence of the apparent interface energy and the interface separation of the ITR with about 1.7nm thickness are analyzed in more detail. The results reveal that the crystalline configuration of Ni-base superalloy (NBSA) with (60–70%) γ′-VF is the stablest, which is similar to the previous investigations.

Keywords: Interface; γ′-phase volume fraction; Ni-base superalloy; Molecular dynamics

Structural stability and electronic properties of LaO- and NiO₂-terminated LaNiO₃ (001) surface by Li Guan; Jingai Zuo; Guoqi Jia; Qingbo Liu; Wei Wei; Jianxin Guo; Xiuhong Dai; Baoting Liu; Yinglong Wang; Guangsheng Fu (pp. 570-573).

Display Omitted► Atomic relaxation and surface energies of different LNO terminations are studied. ► LaO-terminated surface shows the most stable structure. ► Ni atoms exhibit an abnormal relaxation. ► The missing-row LaO- and NiO₂-terminated LNO (001) surfaces are constructed. ► Electronic structure of non-polar surfaces remarkably differs from polar surfaces.LaO- and NiO₂-terminated LaNiO₃ (001) surfaces were investigated by first principle calculations. For NiO₂-terminated surface, Ni atoms exhibit an abnormal relaxation. Larger surface rumpling emerges in the topmost layer of LaO termination, which is almost twice as large as that of NiO₂ termination. LaO-terminated surface has the lowest surface energy and stable structure. Non-polar surfaces exhibit remarkably different electronic structures and more Ni atoms exposed to the surface will contribute to higher density of states at Fermi level, which provides a guide to grow novel ultra-thin heterostructures with controlled electronic state of metal ions.

Keywords: Nickelate; First principle; Surface; LaO- and NiO; ₂; -terminated; Electronic structure

Bulk and surface structure characterization of nanoscopic silver doped lanthanum chromites by P.A. Desai; P.N. Joshi; K.R. Patil; Anjali A. Athawale (pp. 574-580).

Display Omitted► Single step synthesis approach with site preference of silver as a dopant. ► Silver as a crystal dopant with precursors of chromium (nitrate and acetate). ► Valence states of La, Cr, O and silver as a dopant in a perovskite lattice. ► Atomic ratio of constituent elements in bulk as well as surface regime of samples.Crystalline state of lanthanum chromites with silver as a dopant has been studied by X-ray diffraction and transmission electron microscopy reveals microscopic properties of grain boundaries. X-ray photoelectron spectroscopy has been used to analyze surface states with atomic ratio of La, Cr, O and Ag as a dopant. LaCrO₃ shows mixed valence states of chromium while the silver doped samples exhibit differences in chromium concentration with the oxidation of Cr³⁺ to Cr⁶⁺ in presence of chromium nitrate as a precursor salt. Trivalent stable state of chromium is observed for samples synthesized by chromic acetate as a precursor salt.

Keywords: Microwave combustion synthesis; Perovskite nanostructures; X-ray diffraction; Transmission electron microscopy; X-ray photoelectron spectroscopy; Energy dispersive analysis of X-rays

High photocatalytic performance of BiOI/Bi₂WO₆ toward toluene and Reactive Brilliant Red by Huiquan Li; Yumin Cui; Wenshan Hong (pp. 581-588).

When BiOI/Bi₂WO₆ catalyst was exposed to UV or visible light, the electrons in the valence band of Bi₂WO₆ would be excited into the conduction band and then injected into the more positive conduction band of BiOI. Therefore, the photoelectrons were generated from Bi₂WO₆ and transferred across the interface between BiOI and Bi₂WO₆ to the surface of BiOI, leaving the photogenerated holes in the valence band of Bi₂WO₆. In this way, the photoinduced electron–hole pairs were effectively separated.Display Omitted► BiOI sensitized Bi₂WO₆ catalysts were successfully prepared by a facile method. ► The 13.2% BiOI/Bi₂WO₆ catalyst exhibits higher photoactivities than P25. ► A possible transfer process of photogenerated carriers was proposed.BiOI sensitized nano-Bi₂WO₆ photocatalysts with different BiOI contents were successfully synthesized by a facile deposition method at room temperature, and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) high-resolution transmission electron microscopy (HR-TEM), photoluminescence (PL) spectra, UV–vis diffuse reflection spectroscopy (UV–vis DRS) and Brunauer–Emmett–Teller (BET) surface area measurements. The photocatalytic activity of BiOI/Bi₂WO₆ was evaluated by the photo-degradation of Reactive Brilliant Red (X-3B) in suspended solution and toluene in gas phase. It has been shown that the BiOI/Bi₂WO₆ catalysts exhibit a coexistence of both tetragonal BiOI and orthorhombic Bi₂WO₆ phases. With increasing BiOI content, the absorption intensity of BiOI/Bi₂WO₆ catalysts increases in the 380–600nm region and the absorption edge shifts significantly to longer wavelengths as compared to pure Bi₂WO₆. The 13.2% BiOI/Bi₂WO₆ catalyst exhibits obviously higher UV and visible light photocatalytic activities than commercial P25, pure Bi₂WO₆ and BiOI, for the photodegradation of toluene and X-3B. The remarkably enhanced photocatalytic activities can be attributed to the fact that the proper BiOI sensitized nano-Bi₂WO₆ increase its BET surface area, decrease band-gap energy, enhance absorption in the 380–600nm region and inhibit the recombination of photo-induced carriers.

Keywords: Bi; ₂; WO; ₆; BiOI; Toluene; Reactive Brilliant Red; Photocatalysis

A simple approach for surface hardening of polystyrene by Hirofumi Tsuruta; Yukari Ikinaga; Yoshihisa Fujii; Keiji Tanaka (pp. 589-592).

Display Omitted► A simple method to improve surface properties is applied to glassy polymers. ► Hydrolyzed TEOS was preferentially segregated at the surface of polystyrene. ► A few nm-thick polymer–inorganic hybrid layer was constructed at the film surface. ► The PS/TEOS films exhibited excellent wear resistance and anti-oxidant properties.One strategy in prolonging the lifetime of polymer materials is to improve their surface mechanical properties. A simple and easy method to modify the polymer surface based on the preferential segregation of inorganic materials is applied to a glassy polymer. We clearly show that the polystyrene film with a few nm-thick hybrid surface layer with hydrolyzed tetraethoxysilane exhibits excellent wear resistance and anti-oxidant properties.

Keywords: Surface hardening; Surface segregation; Sol–gel process; Wear resistance; Anti-oxidant properties; Polymers

Effect of MWNT electroless Ag plating on field emission properties of MWNT/Ag nanocomposite cathodes by Yun Ye; Tailiang Guo (pp. 593-597).

► Ag nanoparticles and coating were electroless plated onto the surface of CNTs. ► A low turn on field of CNT/Ag cathode was achieved. ► A new way for high stability of CNT/Ag cathode was suggested.Field emission properties of multiwall carbon nanotube (MWNT) electroless Ag plating nanocomposite cathodes fabricated using screen printing were studied. The MWNT was purified and electroless plated with Ag. The results of field emission scanning electron microscopy (FESEM) showed that the morphology of Ag electroless plating on the surface of MWNT depended on the temperature of electroless plating. Experiments showed that the stability of MWNT/Ag nanocomposite cathodes had no more than 10% degradation, achieving a field emission current density of 4.0mA/cm² at an applied electric field of 0.5V/μm for 50h. The proposed MWNT/Ag nanocomposite cathodes possess good field emission properties and have potential for application in field emission displays.

Keywords: Multiwall carbon nanotube; MWNT/Ag; Electroless plating; Field emission

Polyvinyl alcohol functionalized cobalt ferrite nanoparticles for biomedical applications by A.B. Salunkhe; V.M. Khot; N.D. Thorat; M.R. Phadatare; C.I. Sathish; D.S. Dhawale; S.H. Pawar (pp. 598-604).

► Polyvinyl alcohol coating does not affect on structural properties of magnetic nanoparticles. ► Monodisperse characteristics and biocompatibility can be achieved with biocompatible polymer coating on the surface of magnetic nanoparticles. ► Surface properties of magnetic nanoparticles can be manipulate with polymer coatings.In the present work, cobalt ferrite nanoparticles (CoFe₂O₄ NPs) have been synthesized by combustion method. The surface of the CoFe₂O₄ NPs was modified with biocompatible polyvinyl alcohol (PVA). To investigate effect and nature of coating on the surface of CoFe₂O₄ NPs, the NPs were characterized X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The transmission electron microscopy (TEM) and dynamic light scattering (DLS) results demonstrate the monodispersed characteristics of CoFe₂O₄ NPs after surface modification with PVA. The decrease in contact angle from 162° to 50° with PVA coating on NPs indicates the transition from hydrophobic nature to hydrophilic. The Magnetic properties measurement system (MPMS) results show that the NPs have ferromagnetic behavior with high magnetization of 75.04 and 71.02emu/g of uncoated and coated CoFe₂O₄ NPs respectively. These PVA coated NPs exhibit less toxicity over uncoated CoFe₂O₄ NPs up to 1.8mgmL⁻¹ when tested with mouse fibroblast L929 cell line.

Keywords: CoFe; ₂; O; ₄; nanoparticles; Polyvinyl alcohol coatings; Cytotoxicity; Magnetic diameter

Nanoporous alumina formed by self-organized two-step anodization of Ni₃Al intermetallic alloy in citric acid by Wojciech J. Stępniowski; Grzegorz Cieślak; Małgorzata Norek; Krzysztof Karczewski; Marta Michalska-Domańska; Dariusz Zasada; Wojciech Polkowski; Paweł Jóźwik; Zbigniew Bojar (pp. 605-610).

► Anodic porous alumina was formed by Ni₃Al intermetallic alloy anodization. ► The anodizations were conducted in 0.3M citric acid. ► Nanopores geometry depends on anodizing voltage. ► No barrier layer was formed during anodization.Formation of the nanoporous alumina on the surface of Ni₃Al intermetallic alloy has been studied in details and compared with anodization of aluminum. Successful self-organized anodization of this alloy was performed in 0.3M citric acid at voltages ranging from 2.0 to 12.0V using a typical two-electrode cell. Current density records revealed different mechanism of the porous oxide growth when compared to the mechanism pertinent for the anodization of aluminum. Electrochemical impedance spectroscopy experiments confirmed the differences in anodic oxide growth. Surface and cross-sections of the Ni₃Al intermetallic alloy with anodic oxide were observed with field-emission scanning electron microscope and characterized with appropriate software. Nanoporous oxide growth rate was estimated from cross-sectional FE-SEM images. The lowest growth rate of 0.14μm/h was found for the anodization at 0°C and 2.0V. The highest one – 2.29μm/h – was noticed for 10.0V and 30°C. Pore diameter was ranging from 18.9nm (2.0V, 0°C) to 32.0nm (12.0V, 0°C). Interpore distance of the nanoporous alumina was ranging from 56.6nm (2.0V, 0°C) to 177.9nm (12.0V, 30°C). Pore density (number of pore occupying given area) was decreasing with anodizing voltage increase from 394.5 pores/μm² (2.0V, 0°C) to 94.9 pores/μm² (12.0V, 0°C). All the geometrical features of the anodic alumina formed by two-step self-organized anodization of Ni₃Al intermetallic alloy are depending on the operating conditions.

Keywords: Nanopores; Anodization; Self-organization; Anodic oxide; Electrochemical impedance spectroscopy

Femtosecond-laser-induced nanostructure formed on nitrided stainless steel by Naoki Yasumaru; Eisuke Sentoku; Kenzo Miyazaki; Junsuke Kiuchi (pp. 611-615).

► Femtosecond-laser-induced periodic surface nanostructures formed on nitrided stainless steel were investigated. ► The mean spacing D in the nanostructure showed the minimum size of 250nm, corresponding to the size of ∼ λ/3. ► The phenomenon where an irradiated area on the nitrided surface swells arose. ► D observed for the nitrided surface was 10–20% smaller than that for the untreated surface.Periodic surface nanostructures formed on nitrided stainless steel with femtosecond (fs) laser pulses were investigated and compared with those of an untreated surface. The nanostructures are formed in the direction perpendicular to the laser polarization, and the variation of the mean spacing D in the nanostructures was examined as a function of the laser fluence F and the shot number N of fs laser pulses. The minimum value of D observed at F around the ablation threshold was 250nm, which corresponds to approximately 1/3 of the laser wavelength λ, and D increased with increasing F. The characteristic phenomenon where an irradiated area on the nitrided surface swells was observed. The size of D formed over a broad area for the nitrided surface was 10–20% smaller than that for the untreated surface.

Keywords: Femtosecond-laser ablation; Nanostructure; Stainless steel; Nitriding

Study of defect creation in self assembled ZnO nanostructures with electrically charged nanoparticles by Charu Dwivedi; V. Dutta (pp. 616-620).

► A new way of synthesizing nanoparticles and nanorods all together. ► The role of self assembly and effect of growth ambient and annealing atmosphere on the photoluminescence spectra has been investigated. ► Application of the as synthesized defect states in different devices like DSSCs, Photocatalysis and LEDs.ZnO nanostructures (mainly nanorods) are created by self assembly of uncharged and electrically charged nanoparticles using continuous spray pyrolysis (CoSP) technique. The properties of both nanoparticles and nanostructures are studied in order to understand the role of self assembly. The photoluminescence (PL) spectra show dependence on the growth conditions and annealing atmosphere. The nanostructured films created under voltage have a PL band in green (2.2–2.8eV) which is absent for nanoparticles created under identical conditions. Thus, even though the nanoparticles involved have different defect states, the self assembly of unpolarized and electrically polarized nanoparticles affects defect creation in ZnO nanostructures.

Keywords: Zinc oxide; Nanostructures; Spray pyrolysis; Electric field; Self-assembly

Formation of nanostructured emitter for silicon solar cells using catalytic silver nanoparticles by Dan Li; Lei Wang; Dongsheng Li; Ning Zhou; Zhiqiang Feng; Xiaoping Zhong; Deren Yang (pp. 621-624).

Display Omitted► Nanoporous silicon was made on the emitter by size-controlled Ag nanoparticles catalyzed etching. ► The reflectivity of the nanoporous surface and electrical properties of the solar cells were characterized. ► The efficiency improvement was mainly due to the significantly increasing of short-circuit current. ► We report a nanoporous silicon solar cell with a 15.7%-efficiency without any passivation coating.A simple process for nanotexturing on the emitter of silicon solar cells using catalyzed wet chemical etching by size-controlled silver nanoparticles was reported. A fine textured black surface was achieved to realize the low light reflectivity less than 5%. After screen printing and firing by the industrial standard fabrication protocol, we obtained the nanotextured Si solar cells with 15.7%-efficiency without any additional antireflection (AR) coating. This result suggests that the inexpensive metal-assisted wet chemical nanotexture method is prospective to be used in photovoltaic industry.

Keywords: Silicon solar cell; Nanoporous silicon; Antireflection; Ag nanoparticles; Chemical etching

Effects of pulse bias on structure and properties of silicon/nitrogen-incorporated diamond-like carbon films prepared by plasma-enhanced chemical vapor deposition by Hideki Nakazawa; Soushi Miura; Ryosuke Kamata; Saori Okuno; Maki Suemitsu; Toshimi Abe (pp. 625-632).

► The use of pulse bias was effective in suppressing the formation of particles. ► The adhesion of pulse-biased films was improved compared with that of dc-biased films. ► The friction coefficients of Si–N-DLC films were as low as those of Si-DLC films. ► The tribological properties were improved by the use of pulse bias.We have deposited silicon/nitrogen-incorporated diamond-like carbon (Si–N-DLC) films by radio-frequency plasma-enhanced chemical vapor deposition using methane (CH₄), argon (Ar), and hexamethyldisilazane {[(CH₃)₃Si]₂NH} as the Si and N source, and investigated the structure and mechanical and tribological properties of the films. We compared the Si–N-DLC films deposited using pulse bias applied to a silicon substrate with those prepared using dc bias. As the Si and N fractions in the films increased, the internal stress of the films decreases and the adhesion strength to the substrate increased. It was found that the use of the pulse bias was effective in suppressing the formation of particles and further increasing the adhesion strength. The Si–N-DLC films had as low a friction coefficient as Si-incorporated DLC films in ambient air, and the friction coefficients of the films prepared with the pulse bias were lower than the dc-biased films. In addition, the pulse-biased films had a higher wear resistance than the dc-biased films.

Keywords: Diamond-like carbon; Chemical vapor deposition; Silicon; Nitrogen

Influence of pulsed electron beam treatment on microstructure and properties of TA15 titanium alloy by Yu-kui Gao (pp. 633-635).

► The hardness changes were determined by nanoindention method. ► The surface modification by pulsed electron beam treatment was investigated. ► The mechanism was analyzed based on XRD and TEM investigations. ► The modification effects were focused at the surface layer hardness.The surface of TA15 titanium alloy was modified by pulsed electron beam and the hardness distribution along the treated surface layer was investigated by nanoindent technology. The grade characteristics were therefore analyzed by studying the distribution of hardness along surface layer of specimens. Moreover, the microstructure was investigated by OM, XRD and TEM techniques. Furthermore, the correlation of hardness to microstructure was analyzed. The results show that the grade fine grain microstructure is formed in the upper surface layer and the temperature grade or heat effect caused by pulsed electron beam treatment is the main reason to form grade fine grain microstructure in the surface layer.

Keywords: Pulsed electron beam treatment; Grade characteristics; Nanoindent

Synthesis and characterization of asymmetric polymer/inorganic nanocomposites with pH/temperature sensitivity by Xinjie Zhang; Chunmei Gao; Mingzhu Liu; Yinjuan Huang; Xiyong Yu; Enyong Ding (pp. 636-643).

Display Omitted► Pickering emulsion is used which is an easy, comprehensive and inexpensive method to fabricate asymmetric polymer/inorganic nanocomposites. ► TEM images indicate that achieved nanocomposites have asymmetric morphology. ► SiO₂ fabricated with PDMAEMA and PNIPAAM has both pH and temperature sensitivity. ► pH- and thermo-stimuli have been investigated, it shows that nanocomposite particles behave differently according to outside-stimuli.An easy, comprehensive and inexpensive method is demonstrated to produce asymmetric polymer/inorganic nanocomposites in a large quantity. With the aid of Pickering emulsion, unmodified particles aggregate on the surface of emulsion droplets and are fixed in place when the wax solidifies. The exposed surfaces of immobilized SiO₂ particles are modified chemically by 2-(dimethylamino) ethylmethacrylate (DMAEMA). With the removal of wax, the exposed side of particles can be further modified chemically by N-isopropylacrylamide (NIPAAm). Based on these procedures, dual responsive asymmetric nanocomposite particles are achieved with both pH and temperature sensitivities. Due to their dual-stimuli and asymmetric structure, these particles have potential applications in molecule targeting, drug delivery and as building blocks for the assembly of complex nanostructure.

Keywords: Polymer/inorganic nanocomposites; Asymmetry; Pickering emulsion; pH sensitivity; Thermo-sensitivity

Surface imprinting on nano-TiO₂ as sacrificial material for the preparation of hollow chlorogenic acid imprinted polymer and its recognition behavior by Hui Li; Gui Li; Zhiping Li; Cuimei Lu; Yanan Li; Xianzhou Tan (pp. 644-652).

► Used surface imprinting technique with nano-TiO₂ as sacrificial support material. ► Improved adsorption capability of the H-MIP1 compared with the previous work. ► Excellent mass transfer dynamics for the H-MIP1. ► Investigated adsorption thermodynamic of the H-MIP1.Surface imprinting chlorogenic acid (CGA) on nano-TiO₂ particles as sacrificial support material was successfully performed by using 4-vinylpyridine (4-VP) as functional monomer to obtain a hollow CGA-imprinted polymer (H-MIP1). Fourier transmission infrared spectrometry (FTIR) and scanning electron microscopy (SEM) were utilized for structurally characterizing the polymers obtained and adsorption dynamics and thermodynamic behavior investigated according to different models. Binding selectivity, adsorption capacity and the reusability for this H-MIP1 were also evaluated. This hollow CGA imprinted polymer shows rapid binding dynamics and higher binding capability toward the template molecules. The pseudo first-order kinetic model was shown best to describe the binding process of CGA on the H-MIP1 and Langmuir isotherm model best to fit the experimental adsorption isotherm data. Through adsorption isotherms at different temperatures, thermodynamic parameter values were obtained. Selectivity coefficients for the H-MIP1 toward the template were 2.209, 3.213, 1.746 and 2.353 relative to CA, VA, PCA and GA, respectively. This H-MIP1 was also indicated with a good imprint effect and a high capability to capture CGA from methanol extract of Eucommia ulmoides ( E. ulmoides) leaves. Additionally, a good reusability for this imprinted polymer was exhibited during repeated adsorption–desorption use.

Keywords: Surface imprinting; Nano-TiO; ₂; Chlorogenic acid; Adsorption

Fabrication of micro-pin array with high aspect ratio on stainless steel using nanosecond laser beam machining by Se Won Lee; Hong Shik Shin; Chong Nam Chu (pp. 653-663).

► A high aspect ratio micro-pin array was fabricated by laser beam machining using the piling of a recast layer. ► The recast layer could be piled due to the chromium oxide with high surface tension and viscosity of chromium oxide. ► The machining characteristics for a high aspect ratio micro-pin array were investigated according to laser beam parameters. ► Experiments for attaching force relative to the surface roughness of the subject plane were carried out. ► The developed micro-pin array was successfully attached to vertical wall.In this paper, a micro-pin array with a high aspect ratio was fabricated on AISI 304 using laser beam ablation for attachment to a vertical wall. In recent times, there has been research in various fields, including robotics and bio-MEMS, regarding attachment to vertical walls, and micro-pin arrays may offer the best solution. For vertical wall attachment, the micro-pin should have a high aspect ratio, long length, and sharp tip. The recast layer could be piled due to the chromium oxide with high surface tension and viscosity of chromium oxide, and it composed the micro-pins with high aspect ratio. X-ray photoelectron spectroscopy (XPS) was used to identify the characteristics of the piled recast layer. The machining characteristics for a high aspect ratio micro-pin array were investigated according to laser beam machining parameters. In addition, experiments for attaching force relative to the surface roughness of the subject plane were carried out.

Keywords: Micro-pin array; High aspect ratio; Laser beam machining; Recast layer; Attaching force; Surface roughness

Elucidation of the reaction mechanism during the removal of copper oxide by halogen surfactant at the surface of copper plate by Shun Yokoyama; Hideyuki Takahashi; Takashi Itoh; Kenichi Motomiya; Kazuyuki Tohji (pp. 664-669).

Display Omitted► The oxide on Cu plate is removed by using halogen surfactant in two stages. ► At first the oxide on Cu plate is converted to Cu bromide by substitution reaction. ► In the second step, the formed Cu bromide dissolves in the solvent. ► This removal process is affect by reaction temperature and the type of solvent.Although copper nanoparticles have various attractive properties, electrical applications of these was not achieved because of its surface oxide layer which prohibited electrical conduction. Thus, it can be considered that a new elimination method of the oxide on Cu surface, which simultaneously provide the resistance to re-oxidized, should be developed. In this study, the reaction between the metal oxide on Cu plate surface and halogen surfactant was introduced into development as a new elimination method of surface oxide layer.Since electrochemical and surface analysis are effective for analyzing the reaction mechanism which expected to be the reduction reaction of the oxide on metal surface, Cu electrode, which represented material of Cu nanoparticles surface, was used for the reaction mechanism analysis. The oxide is removed by controlling the temperature and selecting the optimal combination of solvents and the halogen surfactant (TIC). Results of electrochemical measurements strongly suggest that the chemical reaction between the oxides on the surface with the halogen surfactant is a substitution reaction which converts Cu oxide to Cu bromide, and continuously formed Cu bromide was dissolved into solvent. Totally, the oxide on the Cu surface was successfully eliminated.

Keywords: Copper surface; Oxide; Bromide; Substitution reaction; Removal method

Surface modification of TiO₂ nanoparticles via photocataliticaly induced reaction: Influence of functionality of silane coupling agent by Radmila Tomovska; Vesna Daniloska; Jose M. Asua (pp. 670-673).

► TiO₂ nanoparticles were modified by photocatalytic induced surface reaction. ► TiO₂ nanoparticles were subjects of modification and catalysts for the reaction. ► No cleavage of SiC bond in silane coupling agent 3-triethoxysilyl propyl isocianate. ► High influence of functional group in silane on the SiC cleavage was determined. ► Different electronegativity of the functionalities in the silane determines reaction way.In the present work the surface modification of TiO₂ nanoparticles by photocatalyticaly induced reaction with silane coupling agent 3-triethoxysilyl propyl isocianate (PIC) has been presented. It was demonstrated establishing of covalent TiOSi bond between the nanoparticles and the PIC molecule. In comparison with previous results, it was demonstrated the high influence of the functional group from the silane coupling agent on the reaction course during surface functionalziation of TiO₂ nanoparticles. Depending on the amount and type (electronegativity of the end-functionalities) of the silane compound, high control of the surface characteristics of TiO₂ nanoparticles could be achieved.

Keywords: Functionalized TiO; ₂; nanoparticles; Photocatalytic surface reaction; 3-triethoxysilyl propyl isocianate; Surface modification; UV light initiation

Plasma focus assisted damage studies on tungsten by M. Bhuyan; S.R. Mohanty; C.V.S. Rao; P.A. Rayjada; P.M. Raole (pp. 674-680).

► Used an ingenious ion source namely plasma focus to study the effect of proton irradiation on tungsten. ► Surface analyses confirm the formation of micro-crack, bubbles, blisters, holes, etc. ► X-ray diffraction patterns confirm the development of compressive stress due to thermal load and formation of other phases or some expanded phases. ► Reduction in the hardness values is observed in case of the exposed sample than the reference sample.Tungsten is being considered as a front runner choice for the plasma facing component material of next generation fusion reactor because of its superior thermophysical and mechanical properties. Therefore, it is essential to study the ion material interaction of this material for its response to severe conditions of fusion reactor. In this work, we have used an ingenious ion source a namely plasma focus to study the effect of proton irradiation on tungsten under various experimental conditions. Exposed and reference tungsten samples were analyzed using optical microscope, scanning electron microscope, atomic force microscope, grazing incidence X-ray diffraction and Vickers hardness tester. Surface analyses confirm the formation of microcracks, bubbles, blisters, holes, etc.X-ray diffraction pattern confirms the development of compressive stress on the sample due to thermal load and formation of other phases or some expanded phases. A slight reduction in hardness values is observed in case of the exposed sample than the reference sample.

Keywords: PACS; 52.58.Lq; 07.77.KaKeyword; Plasma focus; Proton; Tungsten; Scanning electron microscope; Grazing incidence X-ray diffraction

An XPS study of bromine in methanol etching and hydrogen peroxide passivation treatments for cadmium zinc telluride radiation detectors by S. Babar; P.J. Sellin; J.F. Watts; M.A. Baker (pp. 681-686).

► CdZnTe single crystal etched in bromine-in-methanol and passivated in H₂O₂. ► XPS depth used to accurately determine enriched Te layer and TeO₂ thickness. ► For 0.2 and 2.0 (v/v) % bromine-in-methanol treatments, enriched Te layer thickness determined to be 1.3 and 1.8nm, respectively. ► After passivation in 30wt.% H₂O₂, the oxide thickness varies between 1.0 and 1.25nm depending on the calculation method.The performance of single crystal CdZnTe radiation detectors is dependent on both the bulk and the surface properties of the material. After single crystal fabrication and mechanical polishing, modification of the surface to remove damage and reduce the surface leakage current is generally achieved through chemical etching followed by a passivation treatment. In this work, CdZnTe single crystals have been chemically etched using a bromine in methanol (BM) treatment. The BM concentrations employed were 0.2 and 2.0 (v/v) % and exposure times varied between 5 and 120s. Angle resolved XPS and sputter depth profiling has been employed to characterize the surfaces for the different exposure conditions. A Te rich surface layer was formed for all exposures and the layer thickness was found to be independent of exposure time. The enriched Te layer thickness was accurately determined by calibrating the sputter rate against a CdTe layer of known thickness. For BM concentrations of 0.2 (v/v) % and 2 (v/v) %, the Te layer thickness was determined to be 1.3±0.2 and 1.8±0.2nm, respectively. The BM etched surfaces have subsequently been passivated in a 30wt.% H₂O₂ solution employing exposure time of 15s. The oxide layer thickness has been calculated using two standard XPS methodologies, based on the Beer–Lambert expression. The TeO₂ thickness calculated from ARXPS data are slightly higher than the thickness obtained by the simplified Beer–Lambert expression. For BM exposures of 30–120s followed by a passivation treatment of 30wt. % H₂O₂ solution employing an exposure time 15s, the ARXPS method gave an average TeO₂ thickness value of 1.20nm and the simplified Beer–Lambert expression gave an average thickness value of 0.99nm.

Keywords: Cadmium zinc telluride; CZT; XPS; Passivation; Oxide thickness

Self-assembly growth of ZnO-based axial and radial junctions via a two-step method by Yongqin Chang; Yingdong Lu; Mingwen Wang; Yi Long; Rongchang Ye (pp. 687-691).

► Axial and radial ZnO-based junctions were synthesized by a two-step method. ► The sample prepared by the first step plays an important role for the junctions. ► PL spectra reveal the deference among the samples prepared by each step.Self-assembly growth of ZnO-based axial and radial junctions via a kind of two-step method was reported. It was first prepared by a chemical vapor deposition (CVD) method, and then followed by an aqueous solution method to obtain ZnO-based junctions. The formation of the axial or radial junction depends on the sample prepared by the first step. If the microrods grown by the CVD method are pure ZnO, axial junction forms when the sample is put into the solution for further growth, otherwise, radial junction forms if the microrods grown by the first step are doped ZnO. It is attributed to the fastest growth direction in the formation of axial junction and radial junction is quite different. The photoluminescence spectra of the samples reveal that the junctions are quite different from the microrod films prepared by the first step. This work provides a useful way to fabricate ZnO-based junctions, which is important for designing nanodevices.

Keywords: ZnO based junction; Chemical vapor deposition; Aqueous solution method; Photoluminescence; Growth mechanism

Examining the ground layer of St. Anthony from Padua 19th century oil painting by Raman spectroscopy, scanning electron microscopy and X-ray diffraction by Ľubomír Vančo; Magdaléna Kadlečíková; Juraj Breza; Ľubomír Čaplovič; Miloš Gregor (pp. 692-698).

► Raman spectroscopic examination of uncovered and covered paint layers of a real painting. ► Deconvolution of Raman peaks of lead white. ► Comparison of results with energy-dispersive analysis and X-ray diffraction.In this paper we studied the material composition of the ground layer of a neoclassical painting. We used Raman spectroscopy (RS) as a prime method. Thereafter scanning electron microscopy combined with energy dispersive spectroscopy (SEM–EDS) and X-ray powder diffraction (XRD) were employed as complementary techniques. The painting inspected was of the side altar in King St. Stephen's Church in Galanta (Slovakia), signed and dated by Jos. Chr. Mayer 1870. Analysis was carried out on both covered and uncovered ground layers. Four principal compounds (barite, lead white, calcite, dolomite) and two minor compounds (sphalerite, quartz) were identified. This ground composition is consistent with the 19th century painting technique used in Central Europe consisting of white pigments and white fillers. Transformation of lead white occurred under laser irradiation. Subdominant Raman peaks of the components were measured. The observed results elucidate useful partnership of RS and SEM–EDS measurements supported by X-ray powder diffraction as well as possibilities and limitations of non-destructive analysis of covered lower layers by RS.

Keywords: Raman spectroscopy; EDS mapping; X-ray diffraction; Oil painting; Covered ground layer

Carbon nitride nanotube as a sensor for alkali and alkaline earth cations by Javad Beheshtian; Mohammad T. Baei; Zargham Bagheri; Ali Ahmadi Peyghan (pp. 699-706).

► Adsorption of alkali and alkaline earth cations on a CN nanotube studied by DFT. ► The alkaline cation adsorption may raise potential barrier of the electron emission. ► The tube may act as a sensor in the presence of alkali and alkaline cations.Adsorption of several alkali (Li⁺, Na⁺, and K⁺) and alkaline earth (Be²⁺, Mg²⁺, and Ca²⁺) cations on the surface of a zigzag (9, 0) carbon nitride nanotube has been investigated using density functional theory. It has been found that almost all of the cations prefer to be strongly chemisorbed at the center of porous site of the tube surface. The adsorption of alkaline cations much more influences the electronic properties of the tube, in comparison with the alkali ones, so that it is transformed from an intrinsic semiconductor with HOMO/LUMO energy gap of 4.02eV to extrinsic p-type one with the gap of 0.54–1.94eV. The alkaline cation adsorption may significantly raise potential barrier of the electron emission from the tube surface, hence impeding the field emission. It has been also concluded that the electrical sensitivity of the tube toward the cations may be in the order: Be²⁺≫Mg²⁺≫Ca²⁺≫Li⁺∼Na⁺∼K⁺.

Keywords: Nanostructures; DFT; Band gap; Adsorption

Effect of nanosilica on characteristics of carbonizates of phenol-formaldehyde resin – Fe(acac)₃ by V.M. Gun’ko; V.M. Bogatyrov; O.I. Oranska; M.V. Galaburda; E.V. Polshin; I.V. Urubkov; R. Leboda; J. Skubiszewska-Zięba; B. Charmas (pp. 707-712).

Display Omitted► Effects of nanosilica on characteristics of carbon–iron composites. ► Confined space effects reduce size of C–Fe nanoparticles deposited onto nanosilica. ► Carbon and iron carbide protect metallic iron nanoparticles against oxygen from air.A series of carbon–iron–silica (CIS) composites (carbonizates) were prepared by carbonization of phenol-formaldehyde resin – Fe(III) acetylacetonate mixtures with addition of different amount of nanosilica A380 and compared with a composite prepared without silica (CFe composite). The characteristics of the composites differ because two type iron silicates were formed at a surface of silica nanoparticles and affected structure of carbon–iron phases. The textural characteristics of the CIS composites show a decrease in meso- and macroporosity and an increase in nanoporosity because new nanoparticles are formed in voids between silica nanoparticles. The CFe particles, including graphite-like structures, metallic iron nanoparticles and Fe₃C, are larger than the CIS particles, which also include iron silicates, amorphous and crystalline silica. The presence of metallic α-Fe nanoparticles can provide the magnetic properties of the composites.

Keywords: PACS; 61.05.C; 61.05.Qr; 61.43.Gt; 68.37.Hk; 68.43.−hCarbon–iron–silica composites; Carbon–iron composites; Adsorption; Textural characteristics; XRD; Mössbauer absorption spectra; Thermogravimetry

Nanowelding configuration between carbon nanotubes in axial direction by Jianlei Cui; Lijun Yang; Yang Wang (pp. 713-717).

► Nanowelding process could be accomplished at a lower temperature than the melting point of the bulk solder. ► CNTs are connected with solder joints of nodule shape. ► Some silver atoms are captured and dragged into carbon nanotube to form the core filling structures of nanowires. ► Some silver atoms diffuse along the outer walls of SWNTs with the dominant mechanism of capillary wetting.Interconnect technology of carbon nanotubes (CNTs) is essential for functional devices. However, difficulty in the fabrication of the interface between carbon nanotube (CNT) and CNT in axial direction, hindered the quality of connection and practical applications of electrical devices. Also, investigation of dynamic evolution of connection configuration about nanowelding is still lacking. In order to analyze the nanowelding configuration between CNTs in axial direction, the different connection cases are investigated using molecular dynamics simulation. Simulation results show that the nanowelding process could be accomplished at a lower temperature than the melting point of the bulk solder and the CNTs are connected with solder joints of nodule shape. It is also found that metal atoms are captured and dragged into nanotube to form the core filling structures of nanowires during nanowelding. Also, the connection configuration shows that Ag atoms diffuse along the outer walls of SWNTs with the dominant mechanism of capillary wetting, which would increase the contact length to improve the mechanical strength.

Keywords: Carbon nanotube; Connection configuration; Nanowelding; Molecular dynamics

Utilization of tin and titanium incorporated rice husk silica nanocomposite as photocatalyst and adsorbent for the removal of methylene blue in aqueous medium by Farook Adam; Jimmy Nelson Appaturi; Zakia Khanam; Radhika Thankappan; Mohd. Asri Mohd Nawi (pp. 718-726).

Display Omitted► A series of tin and titanium incorporated rice husk silica have been synthesized. ► The removal MB by adsorption was found to be directly dependant on the pH. ► RHA-10Sn10Ti showed high photocatalytic activity in the degradation of MB. ► The photocatalytic activity could be related to the changes in the band gap energy.A series of tin and titanium incorporated rice husk silica have been synthesized via sol–gel method using cetyltrimethylammonium bromide as the structure directing agent. The samples were labeled as RHA-Silica, RHA-10Sn, RHA-10Ti, and RHA-10Sn10Ti. The BET specific surface areas of these catalysts were found to be 315, 607, 439 and 255 (m²g⁻¹) with type IV isotherms, respectively. The catalysts were found to be X-ray amorphous and the particle size was found to be in the nano range. Calcination of RHA-10Sn at 500°C gave silica–tin nanotubes. RHA-10Sn10Ti showed the highest activity in the photocatalytic degradation of methylene blue (MB). The adsorption of MB on these catalysts was found to fit the pseudo-second order kinetic model. The adsorption rate was found to be strongly dependent on the pH of the solution.

Keywords: Rice husk silica; Tin–silica composite; Titanium–silica composite; Nanocomposite; Methylene blue

Effects of surface impurities on epitaxial graphene growth by Valeria del Campo; Ricardo Henríquez; Patricio Häberle (pp. 727-731).

► We studied large scale graphene growth on Ru(0001). ► We found preferential carbon nucleation around impurity particles. ► Carbon nanodiscs were obtained by Low Pressure CVD. ► The diameters of the carbon discs varied between tens to hundreds of nanometers. ► Thickness of carbon discs varied between 3 and 10Å.The focus of this report is to explore the large scale growth of graphene on Ru(0001) and verify the possible effects of crystallographic defects and impurities in the quality of the synthesized material. After a Low Pressure Chemical Vapor Deposition (LP-CVD) process we obtained a graphene film accompanied by other types of graphitic structures. Impurities on the ruthenium surface behaved as nucleation sites in the formation of carbon islands several micrometers wide. The morphological structure of these islands is constituted by carbon discs with diameters in the range of few to several hundred nanometers and thicknesses always below 1nm.

Keywords: Graphene; Ru(0; 0; 0; 1); Carbon nanodiscs; CVD; SEM; STM

Characterization and kinetic investigation of electroless deposition of pure cobalt thin films on silicon substrates by S.L. Cheng; T.L. Hsu; T. Lee; S.W. Lee; J.C. Hu; L.T. Chen (pp. 732-736).

► The growth behaviors of pure Co films deposited by electroless plating have been investigated. ► The electroless Co films produced were polycrystalline with a hexagonal crystal structure. ► The thicknesses of pure Co films increase linearly with plating time in the temperature range of 30–45°C. ► The activation energy derived from an Arrhenius plot is about 32.6kJ/mol. ► Dendritic Co deposits were observed to form at the plating temperature of 50°C.We present here the results of studies of the synthesis and growth behaviors of electroless pure Co thin films on Pd-activated Si substrates using hydrazine as the reductant. Using the hydrazine-modified electroless Co plating processes, dense and continuous pure Co films were deposited on (001)Si for samples plated at 30–45°C. This electroless plating process could be explained by the electrochemical mechanism. After a series of transmission electron microscopic examinations, the deposited Co films were determined to be polycrystalline with a hexagonal crystal structure and the average Co film thickness at each temperature studied was found to follow a linear relationship with the plating time. The deposition rates of pure Co films increase with the plating temperatures from 7.3nm/min to 12.6nm/min. By measuring the Co deposition rates at different plating temperatures, the activation energy for linear growth of the electroless Co thin films on Si substrates derived from an Arrhenius plot is about 32.6kJ/mol. As the plating temperature was increased to 50°C or higher, the plating solution became turbid and the formation of dendritic cobalt deposits was observed.

Keywords: Electroless deposition; Growth kinetic; Co thin film; Hydrazine; Transmission electron microscopy

Synthesis, phase to phase deposition and characterization of rutile nanocrystalline titanium dioxide (TiO₂) thin films by Sanjeev K. Gupta; Jitendra Singh; K. Anbalagan; Prateek Kothari; Ravi Raj Bhatia; Pratima K. Mishra; V. Manjuladevi; Raj K. Gupta; J. Akhtar (pp. 737-742).

► Nanocrystalline rutile TiO₂ thin film has been deposited by e-beam physical vapor deposition (EBPVD) method. ► A vacuum compatible target material (TiO₂) was indigenously prepared for such deposition. ► A phase to phase (rutile to rutile) transformation was observed employing various characterization tools (XRD, RAMAN, UV–vis, FTIR and AFM). ► A process induced self annealing phenomenon shows a strong effect on the structural, morphological and optical properties of deposited thin films. ► The deposited film has sufficient possibility to realize a novel thin film material in the fabrication of active devices.In this work the preparation, deposition and structural properties of titanium oxide (TiO₂) thin films were investigated. The films were deposited by means of the e-beam physical vapor deposition (EBPVD) method in high vacuum (10⁻⁷Torr). A controlled deposition rate in the range of 0.1–0.3Å/s was monitored in situ employing quartz crystal. The films were deposited on the oxidized Si (100) wafer, glass micro slides. These films were analyzed using Grazing Angle X-ray diffraction (GA-XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy (RAMAN), Atomic Force Microscopy (AFM) and UV–visible Spectroscopy (UV–vis). Structural characterization results showed mainly presence of the crystalline rutile phase, however an interfacial SiO₂ layer between TiO₂ and the substrate and the minor anatase crystalline phase of TiO₂ was also identified in FTIR analysis. Grain size was found to be in the range of 100–125nm while grain boundary was estimated to be 20nm. Direct and indirect optical band gap was estimated to be 3.64 and 3.04eV, respectively. A process induced self annealing of deposited film shows a strong effect on the structural, morphological and optical properties. Furthermore, low deposition rate and high vacuum allows rutile to rutile phase transformation from indigenously prepared TiO₂ target to thin film.

Keywords: TiO; ₂; e-Beam evaporation; Thin film; Nanocrystalline; Rutile phase

Production of ceramic layers on aluminum alloys by plasma electrolytic oxidation in alkaline silicate electrolytes by Alex Lugovskoy; Michael Zinigrad; Aleksey Kossenko; Barbara Kazanski (pp. 743-747).

► Al alloy 5052 was treated by PEO in alkaline electrolytes with sodium silicate having silicate index n=1 and n=3. ► For “ n=1 electrolytes” the oxide layer is mainly formed by alumina, for “ n=3 electrolytes” it consists of mullite. ► Microhardness is not influenced by the type of silicate ( n=1 or n=3) and by its concentration in the electrolyte. ► Electrolytes with silicate index n=3 ensure better corrosion protection that those with n=1.Plasma electrolytic oxidation (PEO) of aluminum alloy 5052 in alkaline-silicate electrolytes having different SiO₂/Na₂O ratios (silicate indexes) was studied. For all the electrolytes 20–90μm thick technological layer was obtained; composition, structure and properties of the oxidized layer were studied. For each sample, the oxidized layer consists of a denser internal and looser external sublayer. While for “ n=1 electrolytes” the oxidized layer is mainly formed by several kinds of alumina, the principal constituent of the oxidized layer for “ n=3 electrolytes” is mullite.Measurements of microhardness evidenced that it is apparently not influenced by the kind of silicate ( n=1 or n=3) and by its concentration in the electrolyte. Electrolytes with silicate index n=3 ensure better corrosion protection than those with n=1. Corrosion protection parameters are significantly better for all PEO oxidized samples than for the untreated Al5052 alloy.

Keywords: Plasma electrolytic oxidation; Microarc oxidation; Corrosion protection; Oxide layer; Aluminum alloys

Self-assembling of strain-induced Y₂O₃ nanostructures grown on LaAlO₃ by photo-assisted MOCVD by Wei Li; Shanwen Li; Guoxing Li; Baolin Zhang; Penchu Chou (pp. 748-755).

► Photo-assisted MOCVD was employed to fabricate Y₂O₃ nanodots for the first time. ► Terraces of vicinal substrate were used as template to grow self-assembled Y₂O₃ dots. ► Density and size of nanodots can be tuned by varying T_s and oxygen partial pressure. ► Kinetics processes of Y₂O₃ dots growth were analyzed under various growth parameters. ► Solid cone shaped Y₂O₃ dots with relatively uniform size and density were prepared.Y₂O₃ nanodots were fabricated on vicinal substrate (100)-oriented LaAlO₃ (LAO) by photo-assisted metalorganic chemical vapor deposition (PhA-MOCVD). Nucleation and growth processes of Y₂O₃ nanodots self-assembled as rows along the terraces of LAO were investigated with various growth parameters. It is found that density and size of Y₂O₃ nanodots can be tuned and well controlled by varying substrate temperature ( T_s), oxygen partial pressure and growth time. At lower T_s, the morphologies of Y₂O₃ nanodots are characterized by small and dense solid cones. With elevating T_s, the dots gradually grow larger and sparser. This phenomenon could be illustrated by two competitive kinetic processes, i.e. surface diffusion of adatoms and yttrium desorption. Morphologies of these nanodots were also influenced by variation of oxygen partial pressure. To further discuss the growth kinetics, a more clearly quasi-linear distribution was obtained and the coarsening effect is modified by varying growth time.

Keywords: Y; ₂; O; ₃; Photo-assisted MOCVD; Self-assembled nanodots; Growth parameters

Investigation into conductivity of silver-coated cenosphere composites prepared by a modified electroless process by Xiao Guo Cao; Hai Yan Zhang (pp. 756-760).

► In this paper we described a modified eletroless Ag-coating process on cenospheres. ► The modified method makes the plating process more cost-saving and with less steps. ► The relatively uniform and continuous silver coating is obtained. ► The effects of silver coating on cenospheres on conductivity were investigated.Silver-coated cenosphere composites are successfully fabricated by a modified electroless plating process that is modified by replacing the conventional pretreatment and sensitization steps by only using surface hydroxylation step to simplify the steps and reduce the overall cost of the coating process. Furthermore, the activation and electroless plating steps are merged into one step. The cenosphere particles are characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction analysis (XRD) before and after the coating process. The relatively continuous and compact coating is obtained under the given coating conditions. The results indicated that the conductivity of Ag-coated cenospheres was improved with increasing the AgNO₃ solution dosage and reaction time. It was also found that the optimum AgNO₃ solution concentration was 0.05mol/L, and the optimum range of reaction temperature was from 50°C to 65°C.

Keywords: Electroless plating; Silver coating; Cenospheres; Surface hydroxylation; Conductivity

Differences in etching characteristics of TMAH and KOH on preparing inverted pyramids for silicon solar cells by Yujie Fan; Peide Han; Peng Liang; Yupeng Xing; Zhou Ye; Shaoxu Hu (pp. 761-766).

► TMAH and KOH anisotropic etching characteristics are systematically compared. ► Etch rate of SiO₂ mask is an order of magnitude lower in TMAH than in KOH. ► TMAH etching can obtain much higher quality inverted pyramids than KOH etching. ► Optimized TMAH etching obtains better antireflection properties than KOH etching. ► TMAH is more attractive for the preparation of inverted pyramids than KOH.In this paper, a series of comparative etching experiments on preparing inverted pyramids of silicon solar cells have been carried out using tetramethyl ammonium hydroxide (TMAH) and potassium hydroxide (KOH) at different etchant concentrations and temperatures on a patterned (100) Si. These experiment results show that TMAH solution has higher undercut rate and lower (100) plane etch rate than KOH solution, and the (111)/(100) etch rate ratio of TMAH is two to three times that of KOH solution. Additionally, etch rate of SiO₂ mask is an order of magnitude lower in TMAH than in KOH. Besides, surface morphology analysis indicates that TMAH etching can obtain much higher quality inverted pyramids of sharp vertex, smooth (111) sidewall and uncontaminated surface than KOH etching, which makes TMAH etching samples show better antireflection properties. Finally, the minimum reflectivity of TMAH etching sample low as 1.8% is obtained for inverted pyramids covered with SiO₂ reflectivity coating. So the study reveals that TMAH is more attractive for the preparation of inverted pyramids than KOH.

Keywords: Silicon solar cell; Anisotropic etching; Inverted pyramid; TMAH; KOH; Reflectivity

Effect of surface modification on the porous silicon infiltrated with biomolecules by B. Lawrence; N. Alagumanikumaran; N. Prithivikumaran; N. Jeyakumaran; V. Ramadas; B. Natarajan (pp. 767-771).

Porous silicon is a very host material for sensing application as it has a large internal surface cover and its optical properties can be changed by infiltrating the pores by biomolecules. The oxidized porous silicon layer was treated with chicken blood plasma and serum and the modification in the optical properties of surface layer was studied.Display Omitted► Nanocrystalline porous silicon was fabricated by an electrochemical etching method. ► The oxidized porous silicon was prepared by thermal treatment. ► Biomolecules (chicken blood plasma and serum) were infilterated into nanocrystalline porous silicon and their structural and optical properties were characterized. ► The infilterated biomolecules modified the optical properties of the porous silicon surface. ► Changes in the Photoluminescence emission intensity can be applied in optical biosensor.Nanostructured porous silicon was prepared by electrochemical etching method. The porous silicon has advantages over planar platforms in biosensor development due to its increased surface area. The high surface area in the porous silicon biosensors will allow for higher biosensor sensitivity while using as a smaller device. The porous silicon optical sensing device works on the basis of changes in its physical properties especially photoluminescence or reflectance, on exposure to the surrounding environment. In the present investigation, porous silicon was bio-functionalized through the deposition of functional groups on its surface by adsorption of chicken blood plasma and serum. SEM, FTIR and photoluminescence studies were carried out for bio-functionalized porous silicon surfaces to study the possibility for utilizing porous silicon as a biomaterial for biosensor applications instead of utilizing porous silicon as a biosensor and biomaterial.

Keywords: Nanostructured porous silicon; Chicken blood plasma; Chicken blood serum; Biofunctionalized porous silicon surface; Biosensor

Study on lotus-type porous copper electroplated with a Ni coating on inner surface of pores by Hao Du; Guihong Song; Hideo Nakajima; Yanhui Zhao; Jinquan Xiao; Tianying Xiong (pp. 772-778).

► A Ni coating was deposited on inner surface of pores for lotus-type porous copper with pore size of 0.6mm and pore length of 6mm. ► The Ni coating thickness distributes uniformly along the pore depth and is about 4–5μm on the inner surface of the pores. ► The 0.2% yield stress increases from 22.96 to 30.15MPa, after depositing the nickel coating inside pores of the lotus-type porous copper. ► The absorbed energy per volume increases from 60.83 to 96.01MJ/m³ when compressed to strain of 80%, after depositing the nickel coating inside pores of the lotus-type porous copper.Deposition of Ni coating on inner surface of pores was attempted by electroplating for lotus-type porous copper with pore size of 0.6mm and pore length of 6mm. The surface morphology, thickness, thickness distribution along the pore length, and phase composition of the coating were characterized. It is proven that the Ni coating with a polycrystalline structure can be deposited on the inner surface of the pores with length/diameter of 10 for lotus-type porous copper by agitating the electroplating solution properly during the process. It is indicated that the coating thickness distributes uniformly along the pore depth and is about 4–5μm. Furthermore, the mechanical properties including vicker hardness, compressive yield strength and absorbed energy ability of the electroplated porous copper were evaluated. It is found that the mechanical properties are improved significantly after depositing the nickel coating inside pores of the lotus-type porous copper. Among them, 0.2% yield stress increases from 22.96 to 30.15MPa, while absorbed energy per volume from 60.83 to 96.01MJ/m³ when compressed to strain of 80%, which is attributed mainly to the Ni coating as an obstacle to dislocation slip during deformation and its strengthening effect for the higher strength, and the good adhesion to the pore wall of the porous copper.

Keywords: Lotus-type porous copper; Coating; Inner surface of pore; Mechanical properties

Tuning the optical properties of gold nanostructures fabricated on flexible substrates by Ru. Nikov; N. Nedyalkov; P.A. Atanasov; M. Terakawa; H. Shimizu; M. Obara (pp. 779-782).

► Pulsed laser nanostructuring of gold films on flexible and inexpensive substrates. ► SEM analysis shows that laser treatment of Au films lead to discrete nanostructure. ► The increase of laser fluence of processing results in red shifting of SPR peak. ► The bending of the substrate can tune SPR position in a range of about 30nm. ► Raman analysis indicates that Au nanostructures can be successfully used in SERS.In this paper we present a laser-based method for metal nanostructures formation on flexible substrates. The analysis of the obtained structures is focused on their optical properties. The nanostructures are fabricated by laser processing of gold thin films. The films are deposited on PMMA and PVC substrates by classical PLD technology. The produced films are then annealed by nanosecond pulses delivered by Nd:YAG laser system operated at λ=355nm. At certain conditions the laser treatment leads to formation of discrete nanostructure on the substrate surface. The optical properties of samples fabricated at different conditions are examined by optical spectroscopy. Bending of the substrates at different angles is used to modify the characteristics of the produced structure which leads to change of its optical properties. In this way the plasmon band of the obtained nanostructures can be efficiently tuned in a range of about 30nm. The experiments of using produced structures in Surface Enhanced Raman Spectroscopy show that they can be an efficient alternative of the already developed.

Keywords: Au nanostructures; Flexible substrates; Pulsed laser nanostructuring; SERS; Tunable optical properties

Improved interfacial and electrical properties of atomic layer deposition HfO₂ films on Ge with La₂O₃ passivation by Xue-Fei Li; Xiao-Jie Liu; Yan-Qiang Cao; Ai-Dong Li; Hui Li; Di Wu (pp. 783-786).

► La₂O₃ IPLs were deposited on Ge substrates at 250°C by ALD using La[N(SiMe₃)₂]₃ and H₂O as the precursors. ► CET of 1.35nm and leakage current of 8.3×10⁻⁴A/cm² at V_g=1V are observed for the HfO₂/La₂O₃ gate stack on Ge substrate. ► The improvement in the interfacial and electrical properties is related to the formation of a stable LaGeO_x interfacial layer.We report the characteristics of HfO₂ films deposited on Ge substrates with and without La₂O₃ passivation at 250°C by atomic layer deposition (ALD) using La[N(SiMe₃)₂]₃ and Hf[N(CH₃)(C₂H₅)]₄ as the precursors. The HfO₂ is observed to form defective HfGeO_x at its interface during 500°C postdeposition annealing. The insertion of an ultrathin La₂O₃ interfacial passivation layer effectively prevents the Ge outdiffusion and improves interfacial and electrical properties. Capacitance equivalent thickness (CET) of 1.35nm with leakage current density J_A of 8.3×10⁻⁴A/cm² at V_g=1V is achieved for the HfO₂/La₂O₃ gate stacks on Ge substrates.

Keywords: Ge; HfO; ₂; Interfacial passivation layer; La; ₂; O; ₃; MOS capacitor

Preparation of stable aqueous dispersion of graphene nanosheets and their electrochemical capacitive properties by Yuhong Jin; Mengqiu Jia; Mei Zhang; Qianqian Wen (pp. 787-793).

► A stable aqueous graphene nanosheets was prepared by the reduction of graphene oxide in the potassium hydroxide solution. ► The bulk of the oxygen-containing functional groups were removed from graphene oxide. ► The as-prepared graphene exhibits better electrochemical performance than graphite and graphene oxide. ► This opens a significant strategy for the preparation of graphene based materials.Using potassium hydroxide as the reduction agent, a stable aqueous dispersion of graphene nanosheets was successfully prepared and characterized for its structural and electrochemical properties for supercapacitor application. The structure and morphology of the as-prepared material were investigated by Fourier transform infrared spectra, X-ray diffraction pattern and high resolution transmission electron microscopy, respectively. The electrochemical supercapacitive properties of as-prepared material were evaluated using cyclic voltammetry, galvanostatic charge–discharge methods and electrochemical impedance spectroscopy. The as-prepared material showed maximum specific capacitance of (200Fg⁻¹) in 6.0M aqueous KOH electrolyte at scan rate 5mVs⁻¹. For comparison, we add the data of traditional chemical reduction agent-hydrazine.

Keywords: Graphite; Graphene; Graphene oxide; Supercapacitor

Effect of surface area of substrates aiming the optimization of carbon nanotube production from ferrocene by A.G. Osorio; C.P. Bergmann (pp. 794-800).

► An optimized synthesis of CNTs by ferrocene is proposed.► The surface area of substrates influences the nucleation of CNTs. ► The higher the surface area of substrates the lower the temperature of synthesis. ► Chemical composition of substrates has no influence on the growth of CNTs.Ferrocene is widely used for the synthesis of carbon nanotubes due to its ability to act as catalyst and precursor of the synthesis. This paper proposes an optimization of the synthesis of carbon nanotubes from ferrocene, using a substrate with high surface area for their nucleation. Four different surface areas of silica powder were tested: 0.5, 50, 200 and 300m²/g. Raman spectroscopy and microscopy were used to characterize the product obtained and X-ray diffraction and thermal analysis were also performed to evaluate the phases of the material. It was observed that the silica powder with the highest surface area allowed the synthesis of carbon nanotubes to occur at a lower temperature (600°C), whereas substrates with a surface area lower than 50m²/g will only form carbon nanotubes at temperatures higher than 750°C. In order to evaluate the influence of chemical composition of the substrate, three different ceramic powders were analyzed: alumina, silica and zirconia. carbon black and previously synthesized carbon nanotubes were also used as substrate for the synthesis and the results showed that the chemical composition of the substrate does not play a relevant role in the synthesis of carbon nanotubes, only the surface area showed an influence.

Keywords: Synthesis; Carbon nanotubes; Ferrocene; Surface area

Preparation and properties of homogeneous-reinforced polyvinylidene fluoride hollow fiber membrane by Xuliang Zhang; Changfa Xiao; Xiaoyu Hu; Qianqian Bai (pp. 801-810).

► The homogeneous-reinforced method has been adopted firstly in preparing of PVDF membranes. ► The HR membranes have a favorable interfacial bonding between the coating layer and the matrix membrane. ► The better performance of the HR membranes in protein solution can indirectly improve the service life of membranes.Homogeneous-reinforced (HR) polyvinylidene fluoride (PVDF) hollow fiber membranes include PVDF polymer solutions (coating layer) and the matrix membrane prepared through the dry-wet spinning process. The performance of HR membranes varies with the polymer concentration in the polymer solutions and is characterized in terms of pure water flux, rejection of protein, porosity, infiltration property, a mechanical strength test, and morphology observations by a field emission scanning electron microscope (FESEM). The results of this study indicate that the tensile strength of the HR PVDF membranes decreases slights compared with that of the matrix membrane, but the elongation at break increases much more and the hollow fiber membranes are endowed with better flexibility performance. The HR PVDF hollow fiber membranes have a favorable interfacial bonding between the coating layer and the matrix membrane, as shown by FESEM. The infiltration property is characterized by the contact angle experiments. Pure water flux decreases while the rejection ratio with an increase in polymer concentration increasing. The protein solution flux of the HR PVDF membranes is higher than that of the matrix membrane after 100min of infiltration.

Keywords: PVDF; Homogeneous-reinforced; Hollow fiber membrane; Interface; Tensile strength

Surface electronic properties of polycrystalline bulk and thin film In₂O₃(ZnO)_k compounds by E. Mitchell Hopper; Qimin Zhu; Jürgen Gassmann; Andreas Klein; Thomas O. Mason (pp. 811-815).

► Indium zinc oxide compounds for TCO applications. ► Surface energy levels studied by XPS, UPS, and Kelvin probe. ► Ionization potential was constant for all compounds measured. ► Ionization potential, work function, and Fermi levels similar to In₂O₃ and ZnO.The surface electronic potentials of In₂O₃(ZnO)_k compounds were measured by X-ray and ultraviolet photoelectron spectroscopy. Both thin film ( k=2) and bulk specimens ( k=3, 5, 7, 9) were studied. All bulk specimens exhibited In enrichment at the surface. All samples showed an increase of In core level binding energies compared to pure and Sn-doped In₂O₃. The work functions and Fermi levels spanned a range similar to those of the basis oxides In₂O₃ and ZnO, and the ionization potential was similar to that of both In₂O₃ and ZnO processed under similar conditions (7.7eV). This ionization potential was independent of both composition and post-deposition oxidation and reduction treatments. Kelvin probe measurements of cleaned and UV-ozone treated specimens under ambient conditions were in agreement with the photoelectron spectroscopy measurements.

Keywords: Indium zinc oxide; Photoelectron spectroscopy; Kelvin probe; Ionization potential; Work function

Preparation and characterization of HA microflowers coating on AZ31 magnesium alloy by micro-arc oxidation and a solution treatment by Hui Tang; Dezhen Yu; Yan Luo; Fuping Wang (pp. 816-822).

► Hydroxyapatite microflowers coating is fabricated by micro-arc oxidation and a solution treatment on AZ31 magnesium alloy. ► The corrosion resistance of the magnesium alloy has been enhanced by micro-arc oxidation and solution treatment. ► The coating fabricated by micro-arc oxidation and solution treatment exhibits a high ability to form apatite.Magnesium and its alloys are potential biodegradable implant materials due to their attractive biological properties. But the use of magnesium is still hampered by its poor corrosion resistance in physiological fluids. In this work, hydroxyapatite microflowers coating is fabricated by micro-arc oxidation and a solution treatment on AZ31 magnesium alloy. The microstructure and composition are analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The potentiodynamic polarization and electrochemical impedance spectroscopy are studied in simulated body fluid (SBF) solution, and the apatite-forming ability is studied also. The results show that the corrosion resistance of the magnesium alloy has been enhanced by MAO coating. And the solution treatment can improve the corrosion resistance of the MAO sample, by forming a barrier layer on the surface of the MAO coating, and by penetrating into the outer layer of the MAO film, sealing the micropores and micro-cracks existed in the MAO coating. In addition, the MAO-ST coating also exhibits a high ability to form apatite.

Keywords: Magnesium alloy; HA microflowers coating; Micro-arc oxidation; Solution treatment; Corrosion resistance; Bioactivity

Hard and relaxed a-SiN_xH_y films prepared by PECVD: Structure analysis and formation mechanism by Xiangdong Xu; Qiong He; Taijun Fan; Yadong Jiang; Long Huang; Tianhong Ao; Chunqian Ma (pp. 823-831).

► Silicon nitride films were prepared by PECVD. ► Their mechanical properties were systematically evaluated. ► Their chemical structures and relations with mechanical properties were disclosed. ► The related chemical reactions were proposed and theoretically calculated. ► Hard and relaxed silicon nitride films desirable for device applications were yielded.Amorphous hydrogenated silicon nitride ( a-SiN_xH_y) films were prepared by plasma-enhanced chemical vapor deposition (PECVD). Their chemical structures and mechanical properties were investigated. Results reveal that there are four kinds of SiN groups, involving Si₃N₄, HSiN₃, H₂SiN₂, and Si₃SiN, in the a-SiN_xH_y films. Deposition at 300°C and flow ratio of SiH₄/NH₃=30/30sccm leads to the yield of special a-SiN_xH_y films, in which per two high-N-coordinated SiN groups (Si₃N₄ or HSiN₃) are distributed with one inter-buffer group (Si₃SiN). Such a-SiN_xH_y films exhibit ultralow residual stress (−0.17MPa), high elastic modulus (206.9GPa) and high uniformity, holding great potential for device fabrications. The chemical reactions for the formation of a-SiN_xH_y films were proposed, and the thermodynamic calculations indicate that the utilization ratio of NH₃ reagent in the chemical reactions increases significantly with the increase of SiH₄ flow, but the utilization ratio of SiN bonds in the a-SiN_xH_y formation decreases inversely. This work discloses valuable information on the chemical reactions and structures for a-SiN_xH_y films, and suggests a route to the preparation of a-SiN_xH_y films with high hardness and low stress by conventional PECVD.

Keywords: Silicon nitride films; PECVD; Chemical structures; Mechanical properties

Properties of competitively adsorbed BSA and fibrinogen from their mixture on mixed and hybrid surfaces by Lalit M. Pandey; Sudip K. Pattanayek (pp. 832-837).

► Adsorbed amount is more in case of proteins adsorbing from solutions single proteins than their mixture. ► Adsorbed layer is more elastic when adsorbing from mixture of protein than single proteins. ► Appearance of kink in Δ F_n/ n vs time plot indicates displacement of BSA with Fb. ► Adsorption mechanism on surface controls the time taken for displacement of BSA with Fb.We have studied the adsorption of BSA and fibrinogen from their mixture onto surfaces with mixed self-assembled monolayer (SAM) of amine and octyl (ratio 1:1) and hybrid SAM. The properties of adsorbed proteins obtained from individual protein solution differ considerably from the properties of the adsorbed proteins obtained from mixture of proteins at same total concentration. The adsorbed amount of proteins is lesser and the adsorbed protein is more elastic if it is adsorbing from mixture of proteins. It is found that with increasing total protein concentration, adsorbed amount increases and elasticity of the adsorbed proteins decreases. The apparent displacements of BSA with Fb are observed on the graphs of change in frequency with time, which are obtained from quartz crystal microbalance.

Keywords: Competitive adsorption; Adsorption of proteins; Chemical potential; Vroman effect; QCM; Hybrid SAM

Preparation of a boron nitride single layer on a polycrystalline Rh surface by János Kiss; Károly Révész; Gábor Klivényi; Frigyes Solymosi (pp. 838-844).

► The segregation of boron in a Rh foil started from 700K. ► Its presence altered the surface behavior of Rh; the uptake of NO increased by about 30–37%. ► The boron greatly stabilized the adsorbed oxygen and nitrogen formed during NO dissociation. ► A clean, single BN layer formed on the surface, presumable in nanomash structure.The segregation of boron and its reactivity toward nitric oxide have been investigated by means of high-resolution Auger spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and thermal desorption spectroscopy (TDS). The segregation of boron from a Rh foil started from 700K. Its presence altered the surface behaviors of Rh; the uptake of NO increased by about 30–37%. Whereas the dissociation of NO was about 3–10% on a clean, boron-free surface, the extent of dissociation (at saturation) at highest boron level was almost 98%. This feature strongly suggest a direct interaction between NO and boron on the surface. The presence of boron greatly stabilized the adsorbed nitrogen and oxygen formed in NO dissociation. Boron oxide (BO, B₂O₂) sublimated from the surface below 1000K. Clean, single BN layer formed on the surface close to a monolayer regime, presumable in nanomash structure.

Keywords: Segregation of boron; NO dissociation on Rh; Formation of B; N bond; Boron nitride; Auger fine structures

Origin of the visible-light photoactivity of NH₃-treated TiO₂: Effect of nitrogen doping and oxygen vacancies by Yilin Chen; Xiaoxin Cao; Bizhou Lin; Bifen Gao (pp. 845-852).

► Postcalcination had a positive effect on the visible-light activity of NH₃-treated TiO₂. ► Photocatalytic conversion rate and mineralization rate of benzene on NH₃-treated TiO₂ were 35.8% and 56.0%, respectively. ► Comparative study of H₂-treated TiO₂ catalysts was implemented. ► Origin of the visible-light activity of NH₃-treated TiO₂ was demonstrated by a synergistic effect of substitutional N species and oxygen vacancies in TiO₂.N-doped and oxygen-deficient TiO₂ photocatalysts were obtained by heating commercial TiO₂ in NH₃ atmosphere, followed by a postcalcination process. Catalysts were characterized by X-ray diffraction (XRD), N₂-sorption BET surface area, X-ray photoelectron spectroscopy (XPS), Elemental analysis (EA), UV/vis diffuse reflectance spectroscopy (DRS), Electron spin resonance (ESR) and Photoluminescence (PL). It shows that the NH₃-heat-treatment of TiO₂ resulted in not only nitrogen doping but also creation of oxygen vacancies with optical absorption in visible-light region. The postcalcination achieved several beneficial effects including dramatic removal of surface amino species, a rapid decrease in surface Ti³⁺ species, and a low recombination rate of photogenerated carriers on the co-doped TiO₂. The photocatalytic measurement was carried out by the degradation of gas-phase benzene under visible light irradiation. At steady state, the photocatalytic conversion rate of benzene over the postannealed catalyst was 35.8%, accompanied by the yield of 115ppmv CO₂, which was much higher than that on the NH₃-treated TiO₂ before postcalcination or the H₂-treated TiO₂ catalysts. Results show that the visible-light activity of the NH₃-treated TiO₂ is attributed to a synergistic effect of substitutional nitrogen species and oxygen vacancies in TiO₂.

Keywords: N-doping; Oxygen vacancy; TiO; ₂; Photodegradation; Visible light

Oxidative pit formation in pristine, hydrogenated and dehydrogenated graphene by J.D. Jones; C.F. Morris; G.F. Verbeck; J.M. Perez (pp. 853-863).

► We study oxidative pit formation in pristine and hydrogenated few layer graphene. ► Heating graphene at 590°C increases pit onset temperature to that of graphite. ► We propose this is due to greater adhesion with the substrate. ► Hydrogenation of mono and bilayer graphene lowers pit onset temperature. ► We propose this is due to H-related defects in their sp³ bonded structure.We study oxidative pit formation in pristine, hydrogenated, and dehydrogenated monolayer graphene (MLG), bilayer graphene (BLG) and trilayer graphene (TLG). Graphene samples are produced by mechanical exfoliation of highly oriented pyrolytic graphite (HOPG) onto SiO₂ substrates. Etching is carried out by exposing samples to O₂ gas at 450–700°C. Using atomic force microscopy, we observe that pre-heating pristine MLG in vacuum at 590°C increases the onset temperature for pit formation to values comparable to those in HOPG. We attribute this decrease in reactivity to an increase in adhesion between the MLG and substrate. In hydrogenated MLG and BLG, we observe a significant decrease in the onset temperature for pit formation. Dehydrogenation of these materials results in a decrease in the density of pits. We attribute the decrease in onset temperature to H-related defects in their sp³-bonded structure. In contrast, hydrogenated TLG and thicker-layer samples show no significant change in pit formation. We propose that this is because they are not transformed into an sp³-bonded structure by hydrogenation.

Keywords: Graphene; Multi-layer graphene; Graphane; Hydrogenation; Oxidation; Pit formation

Grafting process of ethyltrimethoxysilane and polyphosphoric acid on calcium carbonate surface by J. Kiehl; C. Ben-Azzouz; D. Dentel; M. Derivaz; J.L. Bischoff; C. Delaite; S. Bistac (pp. 864-871).

XPS survey spectra of (a) CaCO₃ untreated, treated with (b) ethyltrimethoxysilane or (c) polyphosphoric acid. (b) Zoom on the silane area.Display Omitted► Calcium carbonate has been treated with ethyltrimethoxysilane and polyphosphoric acid. ► Treated calcium carbonate has been analyzed by X-ray photoelectron spectroscopy. ► Silanol groups are adsorbed onto calcium carbonate through hydrogen interactions. ► Phosphoric acid is adsorbed on calcium carbonate through a POC bonds formation.In order to facilitate its incorporation into a polymer matrix (mostly hydrophobic), calcium carbonate (CaCO₃), which is strongly hydrophilic, has to be chemically treated to avoid the formation of aggregates and to improve the compatibility with the polymer. The objective of this study is to analyze, by using contact angle measurements and X-ray photoelectron spectroscopy (XPS), the CaCO₃ surface after a chemical surface treatment with ethyltrimethoxysilane (ETMO) and polyphosphoric acid (PPA) in an organic solvent, in order to verify if these molecules are able to interact with the CaCO₃ surface, and to propose some hypothesis about the surface grafting mechanism. After several solvent washings were performed to remove all species in excess, contact angle results have pointed out the presence of an organic layer after the chemical treatment of CaCO₃ with ETMO and PPA. Based on XPS results, we propose a grafting mechanism of silane and phosphoric acid molecules. Ethyltrimethoxysilane induce an hydrolysis process of the CaCO₃ surface which leads to a condensation phenomenon. This SiOH network is adsorbed through hydrogen interactions with some hydroxyl groups. In the case of phosphoric acid, the molecules are adsorbed on carbon atoms through POC bonds formation. This original grafting points out the major role of the solvent nature with CaCO₃ surface reactivity.

Keywords: Calcium carbonate; X-ray photoelectron spectroscopy; Surface grafting

Fabrication of the superhydrophobic surface on aluminum alloy by anodizing and polymeric coating by Wenyong Liu; Yuting Luo; Linyu Sun; Ruomei Wu; Haiyun Jiang; Yuejun Liu (pp. 872-878).

The hydrophobic surface on aluminum alloy fabricated by anodizing and polymeric coating.Display Omitted► Anodizing and polymeric coating were used to prepare a superhydrophobic surface on aluminum alloy. ► Superhydrophobic surfaces with a high water contact angle of 162° and a low rolling angle of 2° were obtained. ► The method is facile, and the materials are inexpensive, and is expected to be used widely.We reported the preparation of the superhydrophobic surface on aluminum alloy via anodizing and polymeric coating. Both the different anodizing processes and different polymeric coatings of aluminum alloy were investigated. The effects of different anodizing conditions, such as electrolyte concentration, anodization time and current on the superhydrophobic surface were discussed. The results showed that a good superhydrophobic surface was facilely fabricated by polypropylene (PP) coating after anodizing. The optimum conditions for anodizing were determined by orthogonal experiments. When the concentration of oxalic acid was 10g/L, the concentration of NaCl was 1.25g/L, anodization time was 40min, and anodization current was 0.4A, the best superhydrophobic surface on aluminum alloy with the contact angle (CA) of 162° and the sliding angle of 2° was obtained. On the other hand, the different polymeric coatings, such as polystyrene (PS), polypropylene (PP) and polypropylene grafting maleic anhydride (PP-g-MAH) were used to coat the aluminum alloy surface after anodizing. The results showed that the superhydrophobicity was most excellent by coating PP, while the duration of the hydrophobic surface was poor. By modifying the surface with the silane coupling agent before PP coating, the duration of the superhydrophobic surface was improved. The morphologies of the superhydrophobic surface were further confirmed by optical microscope (OM) and scanning electron microscope (SEM). Combined with the material of PP with the low surface free energy, the micro/nano-structures of the surface resulted in the superhydrophobicity of the aluminum alloy surface.

Keywords: Superhydrophobic surface; Anodizing; Polymeric coating; Aluminum alloy

Synthesis and characterization of in situ TiC–TiB₂ composite coatings by reactive plasma spraying on a magnesium alloy by Binglin Zou; Shunyan Tao; Wenzhi Huang; Zuhair S. Khan; Xizhi Fan; Lijian Gu; Ying Wang; Jiaying Xu; Xiaolong Cai; Hongmei Ma; Xueqiang Cao (pp. 879-885).

► TiC–TiB₂ composites coatings were produced on Mg alloy by reactive plasma spraying. ► Phase composition, microstructure and wear resistance of the coatings were studied. ► The resultant product in the coatings was composed of TiC and TiB₂. ► The produced coatings displayed porous and dense microstructures. ► The synthesized coatings exhibited good wear resistance for Mg alloy substrate.TiC–TiB₂ composite coatings were successfully synthesized using the technique of reactive plasma spraying (RPS) on a magnesium alloy. Phase composition, microstructure and wear resistance of the coatings were characterized by using X-ray diffraction, scanning electron microscopy and pin-on-disk wear test, respectively. The results showed that the resultant product in the RPS coatings was composed of TiC and TiB₂. Depending on the ignition of self-propagating high-temperature synthesis reaction in the agglomerate particles, the RPS coatings displayed porous and dense microstructures. The porosity of the RPS coatings, to some extent, decreased when the feed powders were plasma sprayed with Ni powders. The RPS coatings provided good wear resistance for the substrate under various loads. For high loads (e.g., ≥15N), the wear resistance could be significantly improved by the proper addition of Ni into the RPS coatings.

Keywords: Reactive plasma spraying (RPS); Self-propagating high-temperature synthesis (SHS); TiC–TiB; ₂; Coating; Microstructure; Magnesium alloy

Surface modification of calcium–copper hydroxyapatites using polyaspartic acid by Masseoud Othmani; Abdallah Aissa; Hassen Bachoua; Mongi Debbabi (pp. 886-891).

► The reaction of polyaspartic acid with calcium hydroxyapatite and mixed calcium–copper hydroxyapatite is tested. ► Chemical analysis shows that the presence of copper in the apatitic structure increases the reactivity of the apatite surface. ► X-ray powder analysis shows the conservation of unique crystalline phase of hydroxyapatite after copper incorporation and/or PASP acid reacting. ► IR spectra show the formation of the formation of organometallic bond MOC (MCa or Cu) on the apatitic surface. ► Transmission electron microscopy (TEM) micrographs and atomic force microscopy (AFM) indicated that the texture surface was changed by the grafting.Mixed calcium–copper hydroxyapatite (Ca–CuHAp), with general formula Ca(10− x₎Cu_x(PO₄)₆(OH)₂, where 0≤ x≤0.75 was prepared in aqueous medium in the presence of different concentrations of poly-l-aspartic acid (PASP). XRD, IR, TG-DTA, TEM-EDX, AFM and chemical analyses were used to characterize the structure, morphology and composition of the products. All techniques show the formation of new hybrid compounds Ca–CuHAp–PASP. The presence of the grafting moiety on the apatitic material is more significant with increasing of copper amount and/or organic concentration in the starting solution. These increases lead to the affectation of apatite crystallinity. The IR spectroscopy shows the conservation of (POH) band of (HPO₄)²⁻ groups, suggesting that PASP acid was interacted only with metallic cations of hydroxyapatite.

Keywords: Hydroxyapatite; Grafting; Polyaspartic acid

Effect of laser operating mode in paint removal with a fiber laser by Yuvraj K. Madhukar; Suvradip Mullick; Dinesh K. Shukla; Shailesh Kumar; Ashish K. Nath (pp. 892-901).

► Paint removal characteristics with CW and modulated power fiber laser are presented. ► Higher line energy yielded relatively poor paint removal efficiency. ► Poor efficiency attributed to absorption loss in laser produced plume. ► Shorter pulse-on time and sufficient time between two pulses to allow plume to die down yielded better process efficiency.The laser paint removal behavior with the continuous wave (CW) beam and repetitive pulses has been investigated using an Yb:fiber laser. The specific energy, which is defined as the amount of laser energy needed to remove unit volume of paint prior to the onset of substrate damage and is a measure of the process efficiency, was found to be dependent on the laser processing parameters. In CW mode the specific energy reduced with the increase of laser scan speed and corresponding increase of laser power. In case of repetitive pulsed mode the specific energy was found to depend on the pulse on-time as well as on the time interval between two successive pulses. At 1kHz repetition rate, the specific energy reduced with the increase of duty cycle and corresponding increase in scanning speed, but at relatively low frequencies of 50–150Hz and 50% overlap between two pulses specific energy was found to increase with increasing duty cycle. Irrespective of the mode of operation specific energy increased with the increase of average line energy. During the laser paint irradiation a plume of burning fume was formed over the surface and the variation in specific energy with laser processing parameters has been attributed to the absorption of laser radiation in the plume. Since the dimension of plume and fume particle density in it will depend on the laser energy absorbed in paint, the absorption loss in plume will depend on the laser parameters. This was confirmed by measuring the plume temperature for different laser processing conditions. Based on this and considering that the actual specific energy absorbed by paint should be constant, the absorption characteristic of plume was modeled applying Beer Lambert's law.

Keywords: Paint removal; Fiber laser; CW; Modulated power; Laser plume; Temperature profile

Corrigendum to ‘Effect of surface modification on carbon fiber and its reinforced phenolic matrix composite’ [Appl. Surf. Sci. 259 (2012) 288–293] by Hua Yuan; Chengguo Wang; Shan Zhang; Xue Lin (pp. 902-902).

Erratum to “Study of methanol oxidation of hydrothermally synthesized PtRuMo on multi wall carbon nanotubes” [Appl. Surf. Sci. 257 (2011) 8433–8437] by Nitul Kakati; Jatindranath Maiti; Jun Young Oh; Young Soo Yoon (pp. 903-904).

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Applied Surface Science (v.264, #)