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Applied Surface Science (v.257, #23)

Aluminium-induced crystallization of amorphous silicon films deposited by DC magnetron sputtering on glasses by F. Kezzoula; A. Hammouda; M. Kechouane; P. Simon; S.E.H. Abaidia; A. Keffous; R. Cherfi; H. Menari; A. Manseri (pp. 9689-9693).

► The annealing of the films was carried out under seal vacuum. ► a-Si:H films deposited on Al/glass present better crystallization than a-Si layers above 450°C. ► Hydrogen induces an improvement of structural properties of poly-Si prepared by AIC. ► Shift in the Raman peak could be related to the presence of the stress. ► Thicknesses of a-Si and Al layers and their ratio play an important role in AIC process.Amorphous silicon (a-Si) and hydrogenated amorphous silicon (a-Si:H) films were deposited by DC magnetron sputtering technique with argon and hydrogen plasma mixture on Al deposited by thermal evaporation on glass substrates. The a-Si/Al and a-Si:H/Al thin films were annealed at different temperatures ranging from 250 to 550°C during 4h in vacuum-sealed bulb. The effects of annealing temperature on optical, structural and morphological properties of as-grown as well as the vacuum-annealed a-Si/Al and a-Si:H/Al thin films are presented in this contribution. The averaged transmittance of a-Si:H/Al film increases upon increasing the annealing temperature. XRD measurements clearly evidence that crystallization is initiated at 450°C. The number and intensity of diffraction peaks appearing in the diffraction patterns are more important in a-Si:H/Al than that in a-Si/Al layers. Results show that a-Si:H films deposited on Al/glass crystallize above 450°C and present better crystallization than the a-Si layers. The presence of hydrogen induces an improvement of structural properties of poly-Si prepared by aluminium-induced crystallization (AIC).

Keywords: Crystallization; Thin films; Hydrogenated amorphous silicon; AIC; Raman; XRD

Effects of platinum nano electrodeposits on corrosion of carbon substrate by Won-Jin Beom; R.S. Kalubarme; Kwi-Sub Yun; Chan-Jin Park (pp. 9694-9702).

► The density of pulsed electrodeposited Pt nano particles reached a maximum and then decreased slightly, whereas the diameter of the deposits increased with time. ► The carbon corrosion was severed in the electrodes with Pt nano electrodeposits compared with that in the bare electrode, indicating the accelerated carbon corrosion due to the catalytic activity of the electrodeposited Pt. ► The model for the corrosion of the carbon substrate by Pt nano electrodeposits was proposed.The electrodes for the experiments were prepared by electrodepositing Pt on a carbon substrate. In the cyclic voltammograms of the carbon electrodes with and without Pt nano electrodeposits, the total anodic current including the currents from the oxygen evolution reaction and carbon corrosion increased abruptly above a critical potential. The oxidation overpotential of the carbon electrodes with Pt nano electrodeposits was lower than that of the bare carbon electrode. This phenomenon was more prominent at 75°C than at 25°C. In the potentiostatic experiments, the current transients and corresponding power spectral density (PSD) increased with increasing applied potential to the electrodes. Furthermore, the current transients for the carbon electrodes with Pt nano electrodeposits were much higher than those for the bare carbon electrode. This suggests that the corrosion of the carbon substrate can be accelerated by the Pt nano electrodeposits.

Keywords: Pt nano electrodeposits; Carbon corrosion; Oxidation overpotential; Current transient

Corrosion behaviors in physiological solution of cerium conversion coatings on AZ31 magnesium alloy by Xiufang Cui; Yuyun Yang; Erbao Liu; Guo Jin; Jinggao Zhong; Qingfen Li (pp. 9703-9709).

► We obtained the compact cerium conversion coating with tiny and thick cracks on biomaterial AZ31 magnesium alloys. ► The coating is made of CeO₂, CeO, Ce₂O₃, MgO, Mg(OH)₂ and Al₂O₃. ► The conversion coating can slow down the degradation of magnesium alloys immersed in Hank's solution for 24h. ► The degradation elements were the essential element and a platform for forming a natural bone. ► Cerium conversion coating had better corrosion resistance than bare sample via electrochemical tests in Hank's solution.In this paper, a non-toxic Ce-based conversion coating was obtained on the surface of bio-medical AZ31 magnesium alloys. The micro-morphology of the coating prepared with optimal technical parameters and immersed in physiological solution (Hank's solution) in different time was observed by scanning electron microscopy (SEM), composition of the cerium conversion coating and corrosion products in Hank's solution were characterized by X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS), respectively. In addition, the corrosion property in Hank's solution was studied by electrochemical experiment and immersion test. The results show that the dense Ce-based conversion coating is obtained on the surface of AZ31 magnesium alloys in optimal technical parameters and the conversion coating consists of a mass of trivalent and tetravalent cerium oxides. The cerium conversion coating can provide obvious protection of magnesium alloys and can effectively reduce the degradation speed in Hank's solution. Also the degradation products have little influence on human body.

Keywords: Hank's solution; Corrosion; AZ31 magnesium alloy; Cerium conversion coating

Short time synthesis of high quality carbon nanotubes with high rates by CVD of methane on continuously emerged iron nanoparticles by Behnam Bahrami; Abasali Khodadadi; Yadollah Mortazavi; Mohamad Esmaieli (pp. 9710-9716).

► Quality and quantity of carbon nanotubes depend upon synthesis time. ► The best quality and growth rate may be obtained at very short synthesis time. ► Iron supported MgO catalyst provides continuous seeds of iron for growth of the CNTs. ► Elongation of CNts stop after a few minutes of synthesis.We report the variation of yield and quality of carbon nanotubes (CNTs) grown by chemical vapor deposition (CVD) of methane on iron oxide–MgO at 900–1000°C for 1–60min. The catalyst was prepared by impregnation of MgO powder with iron nitrate, dried, and calcined at 300°C. As calcined and unreduced catalyst in quartz reactor was brought to the synthesis temperature in helium flow in a few minutes, and then the flow was switched to methane. The iron oxide was reduced to iron nanoparticles in methane, while the CNTs were growing.TEM micrographs, in accordance with Raman RBM peaks, indicate the formation of mostly single wall carbon nanotubes of about 1.0nm size. High quality CNTs with I_G/ I_D Raman peak ratio of 14.5 are formed in the first minute of CNTs synthesis with the highest rate. Both the rate and quality of CNTs degrades with increasing CNTs synthesis time. Also CNTs quality sharply declines with temperature in the range of 900–1000°C, while the CNTs yield passes through a maximum at 950°C. About the same CNTs lengths are formed for the whole range of the synthesis times. A model of continuous emergence of iron nanoparticle seeds for CNTs synthesis may explain the data. The data can also provide information for continuous production of CNTs in a fluidized bed reactor.

Keywords: Carbon nanotubes; Chemical vapor deposition; Methane; Iron; Nanoparticles; Model

Silicon rich silicon oxide films deposited by radio frequency plasma enhanced chemical vapor deposition method: Optical and structural properties by Sumita Mukhopadhyay; Swati Ray (pp. 9717-9723).

► Nc-Si silicon rich silicon oxide films have been realised through RF PECVD technique. ► Nanocrystals formation have been observed in the as deposited condition. ► Hydrogen dilution of silane strongly affects the microstructure of the films. ► SRSO films reveal the presence of room temperature visible PL spectra. ► SRSO films can be successfully used in the absorber layer of solar cell.Silicon rich silicon oxide films have been deposited by plasma enhanced chemical vapour deposition using a gas mixture of silane, carbon-di-oxide and hydrogen. Silicon nanocrystals formations in the as deposited silicon rich silicon oxide films have been detected by high resolution transmission electron microscopy, scanning electron microscopy, Raman scattering and X-ray diffraction studies. Structural changes under different deposition condition have been studied by Fourier transform infrared spectroscopy. The oxygen and hydrogen bonding configurations have been obtained from Fourier transform infrared spectroscopy. Room temperature photoluminescence spectra have been observed for the as deposited films. The structural properties together with photoluminescence spectra allowed us to gain insight about the Si nanocrystal formation.

Keywords: Silicon rich silicon oxide; IR; Photoluminescence; Raman; HRTEM

Preparation and characterization of bifunctional, Fe₃O₄/ZnO nanocomposites and their use as photocatalysts by Juan Xia; Anqi Wang; Xiang Liu; Zhongxing Su (pp. 9724-9732).

► The photocatalytic activity of Fe₃O₄/ZnO was explored. ► The catalyst was prepared by a facile two-step strategy. ► It was found to be an ideal photocatalyst for the Methyl Orange degradation. ► It also has high photocatalytic activity and excellent reusage.Bifunctional magnetic-optical Fe₃O₄/ZnO nanocomposites with different molar ratio were successfully synthesized by a facile two-step strategy. Compared with the other methods, it was found to be mild, inexpensive, green, convenient and efficient. Fe₃O₄ nanocrystal was used as seed for the deposit and growth of ZnO nanoparticle. A series of the characterizations manifested that the combination of Fe₃O₄ with ZnO nanoparticles was successful. Photocatalytic activity studies confirmed that as-prepared nanocomposites had excellent photodegradating behavior to Methyl Orange (MO) compared to the pure ZnO nanoparticles. The results showed that the degradation percentage of MO was about 93.6% for 1h when the amount of catalyst was 0.51gL⁻¹ and initial concentration of MO was 6×10⁻⁵molL⁻¹ in the pH 7 solution. Moreover, the kinetics of photocatalytic degradation reaction could be expressed by the first-order reaction kinetic model. Furthermore, the Fe₃O₄/ZnO nanocomposites could be also served as convenient recyclable photocatalysts because of their magnetic properties.

Keywords: Fe; ₃; O; ₄; /ZnO nanocomposites; Photoluminescence properties; Magnetic properties; Recycle photocatalysts

Crystallization behavior and microstructure of Fe₇₅Co₆Zr₉B₁₀ alloy by W.Q. Yu; Y.M. Sun; Z. Hua (pp. 9733-9736).

► We study the crystallization behavior and microstructure of Fe₇₅Co₆Zr₉B₁₀ alloy. ► The α-Fe and α-Mn type phases are observed at 873K. ► The lattice parameter for α-Mn type phase determined by TEM is 0.8830nm. ► AFM images show the development of surface morphology of alloys after annealing.Fe₇₅Co₆Zr₉B₁₀ amorphous alloy prepared by melt-spinning was annealed at various temperatures. The crystallization behavior and microstructure were investigated by differential thermal analysis (DTA), X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The three exothermal peaks in the DTA curve of Fe₇₅Co₆Zr₉B₁₀ amorphous alloy correspond to the formations of α-Fe and α-Mn type phases, the growth of BCC-Fe volume fraction at the expense of α-Mn and residual amorphous phase and the precipitations of Fe₃Zr, etc. intermetallic compounds, respectively. The second exothermic peak is not influenced by heating rate, but it shifts to a higher temperature region with increasing preannealing temperature of Fe₇₅Co₆Zr₉B₁₀ alloy. The α-Mn type phase is metastable and its lattice parameter determined by TEM is 0.8830nm. AFM images show the development of surface morphology of alloy after annealing. The particle size increases with increasing annealing temperature.

Keywords: Crystallization behavior; Microstructure

Nanocoral architecture of TiO₂ by hydrothermal process: Synthesis and characterization by Sawanta S. Mali; Pravin S. Shinde; C.A. Betty; Popatrao N. Bhosale; Won J. Lee; Pramod S. Patil (pp. 9737-9746).

Display Omitted► We synthesized novel TiO₂ nanocorals by hydrothermal route at 120°C. ► The diameter of the circular corals is about 400–500nm, on top of which nanopolyps are nucleated and their average size is about 20nm. ► Such peculiar morphological feature is beneficial as it provides larger active surface area. ► Approximately 1.8μm thick nanocoral TiO₂ films were achieved using MSH process exhibiting substantial increment in short circuit current density ( J_sc=154μA).TiO₂ thin films with novel nanocoral-like morphology were successfully grown directly onto the glass and conducting fluorine doped tin oxide coated glass substrates via multi-step hydrothermal (MSH) process. Titanium chloroalkoxide [TiCl₂ (OEt)₂ (HOEt)₂)] precursor was used in an aqueous saturated NaCl in presence of 1mM HCl catalyst and HNO₃ peptizer at 120°C. Reaction time varied from 3 to 12h. The morphological features and physical properties of TiO₂ films were investigated by field emission scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, Fourier transform IR spectroscopy, Fourier transform Raman spectroscopy, room temperature photoluminescence spectroscopy and X-ray photoelectron spectroscopy. The surface morphology revealed the formation of TiO₂ corals having nanosized (30–40nm) polyps. The photoelectrochemical properties of the TiO₂ nanocoral electrodes were investigated in 0.1M NaOH electrolyte under UV illumination. The results presented in this study highlight two major findings: (i) ability to tune the photoelectrochemical response and photoconversion efficiency via controlled thickness of TiO₂ nanocorals and (ii) the substantial increase in short circuit photocurrent ( J_sc) due to the improved charge transport through TiO₂ nanocorals prepared via MSH process. This approach would be quite useful for the fabrication of nanocoral architecture that finds key applications in photocatalysis, dye-sensitized solar cells and hybrid solar cells.

Keywords: Hydrothermal route; Nanocoral architecture of TiO; ₂; Photoelectrochemical performance

Interactions between CdSe/CdS quantum dots and DNA through spectroscopic and electrochemical methods by Qisui Wang; Lu Yang; Tingting Fang; Shuang Wu; Peng Liu; Xinmin Min; Xi Li (pp. 9747-9751).

► The interaction of QDs with DNA has been studied. ► The apparent association constant has been deduced between QDs and DNA. ► The binding force of QDs with dsDNA is stronger than ssDNA. ► The results illuminate that hs-DNA has the high affinity for QDs.The interaction of CdSe/CdS quantum dots (QDs) with Herring sperm-DNA (hs-DNA) has been studied by UV–vis spectroscopy and electrochemical method. Cu(phen)₂^2+/1+ (phen=1, 10-phenanthroline) was used as an indicator for electroactive dsDNA or ssDNA. The apparent association constant has been deduced (4.94×10³M⁻¹ and 2.39×10²M⁻¹) from the absorption spectral changes of the dsDNA–QDs and ssDNA–QDs. The results of dissociation method suggest that Cu(phen)₂^2+/1+ is more easily dissociated from dsDNA or ssDNA modified gold electrode (dsDNA/Au or dsDNA/Au) in presence of QDs. The dissociation rate constant ( k) of Cu(phen)₂^2+/1+ on dsDNA/Au is 4.48 times higher than that in absence of QDs, while k is 2.34 times higher than that in absence of QDs on ssDNA/Au in Tris buffer with low ionic strength (pH 7.0, 0.5mM NaCl). The results illuminate that hs-DNA has high affinity for QDs due to electrostatic force, hydrogen bonds, and van der Waals interactions, and the binding force of QDs with dsDNA is stronger than ssDNA.

Keywords: DNA; Quantum dots; Interaction; UV–vis spectroscopy; Electrochemistry

Sol–gel preparation and characterization of nanoporous ZnO/SiO₂ coatings with broadband antireflection properties by Dezeng Li; Fuqiang Huang; Shangjun Ding (pp. 9752-9756).

► Nanoporous ZnO/SiO₂ bilayer coatings were prepared via sol-gel dip-coating process. ► The broadband antireflection performance was determined over the solar spectrum. ► The solar transmittance in 300-2500 nm was increased by 6.4%. ► Such antireflection coatings provide a promising route for solar energy applications.Nanoporous ZnO/SiO₂ bilayer coatings were prepared on the surface of glass substrates via sol–gel dip-coating process. The structural, morphological and optical properties of the coatings were characterized. The refractive indices of ZnO layer and SiO₂ layer are 1.34 and 1.21 at 550nm, respectively. The transmittance and reflectance spectra of the coatings were investigated and the broadband antireflection performance of the bilayer structure was determined over the solar spectrum. The solar transmittances in the range of 300–1200nm and 1200–2500nm are increased by 6.5% and 6.2%, respectively. The improvement of transmittance is attributed to the destructive interference of light reflected from interfaces between the different refractive-index layers with an optimized thickness. Such antireflection coatings of ZnO/SiO₂ provide a promising route for solar energy applications.

Keywords: Antireflection coatings; Broadband; ZnO/SiO; ₂; bilayer coatings; Sol–gel process; Nanoporous structure

Alendronate decorated nano hydroxyapatite in mesoporous silica: Cytotoxicity and osteogenic properties by Wei Huang; Weiqiang Liu; Zhending She; Hongkai Wu; Xuetao Shi (pp. 9757-9761).

► Hydroxyapatite-modified mesoporous silica materials (MSH) have been developed. ► MSH showed lower cytotoxicity than pure mesoporous silica. ► The osteogenesis of MSCs treated by alendronate (AL) decrodated MSH was evaluated. ► The osteogenesis of MSCs induced by MSH-AL is comparable to that induced by the osteogenic medium.Mesoporous silica is a promising drug delivery vehicle due to its large surface area and order porous structure. Hydroxyapatite-modified mesoporous silica materials (MSH) have been developed, and the cytotoxicity of MSH and unmodified mesoporous silica (HMS) has also been studied in this work. The results indicated that MSH exhibited lower cytotoxicity than HMS. The drug release property of MSH was also investigated in this paper. Alendronate (AL) was laden into MSH and HMS, respectively. MSH exhibited long release period lasting over 30 days with a weak burst release in the first 5 days; however, the AL release period of HMS was just 5 days with a remarkable burst release. In addition, the osteogenic commitment induced in human marrow mesenchymal stem cells (MSCs) by MSH-alendronate (MSH-AL) was also investigated, and the osteogenesis of MSCs was evaluated by alkaline phosphatase (ALP) assay. The osteogenesis of MSCs induced by MSH-AL is comparable to that induced by the osteogenic medium. Taken together, MSH can be severed as potential bone repair materials with lower cytotoxicity.

Keywords: Mesoporous silica; Hydroxyapatite; Cytotoxicity; Alendronate; Osteogenesis

Investigations on the growing, cracking and spalling of oxides scales of powder metallurgy Rene95 nickel-based superalloy by Lei Zheng; Maicang Zhang; Reda Chellali; Jianxin Dong (pp. 9762-9767).

► Decohesion, rumpling, cracking and finally spalling of oxides scale were observed. ► Oxides scale is mainly composed by Cr₂O₃ at 800°C and NiCr₂O₄ is the main spinel at 1100°C. ► Cracking and spalling are caused by growth stress and promoted by thermal stress. ► The proper way to increase oxidation resistance is enhancing the cohesive strength of the scale/alloy interface.The surface and cross-sectional morphologies of powder metallurgy (PM) Rene95 nickel-based superalloy after 100h oxidation in the temperature range of 700–1100°C were investigated. It is shown that oxides nucleate first on the surface of the alloy and form an oxides scale. Afterwards, oxides scale endures decohesion, rumpling, cracking and finally spalling owing to the weak cohesive strength of the scale/alloy interface. The XRD and EDS analyses confirmed that the oxides scale of PM Rene95 superalloy is mainly composed by Cr₂O₃ at 800°C and NiCr₂O₄ is the main spinel at 1100°C. The subsequent analysis of internal stress verified that cracking and spalling are caused by growth stress and promoted by thermal stress. On these bases, improvement of the cohesive strength of the scale/alloy interface is considered to be the main way to increase the oxidation resistance of PM Rene95 superalloy.

Keywords: Nickel based superalloys; Powder metallurgy; Oxidation; Rene95

Molecular-mediated crystal growth of PbTiO₃ nanostructure on silicon substrate by Chunying Chao; Zhaohui Ren; Zhenya Liu; Zhen Xiao; Gang Xu; Xiang Li; Xiao Wei; Ge Shen; Gaorong Han (pp. 9768-9772).

► The amorphous powder modified by acetylacetone (acac) was used as precursor. ► The precursor was prepared by the sol–gel with the subsequent freeze-drying process. ► The PbTiO₃ nanostructure on Si (100) substrate with tetragonal shapes and uniform sizes were successfully achieved. ► It was found that the molar ratio of acac/Pb plays an important role in the PT nanostructure growth on the Si (100) substrates.A simple approach based on an organically modified sol–gel process has been developed to fabricate PbTiO₃ (PT) nanocrystals on Si (100) substrate, where the amorphous powder modified by acetylacetone (acac) was used as precursor. After dropping the amorphous powder precursor prepared by freeze-drying process, PT nanocrystals on Si (100) substrate were obtained after heat treatment at 720°C for 30min in air. PT nanocrystals have been detected by XRD to be tetragonal perovskite structure. With the increase of acac/Pb molar ratio, the relative (100)/(001) diffraction peak intensity gradually increases, which probably suggested an oriented growth of PT nanocrystal along [100] on Si (100) substrates. In addition, Atomic force microscopy (AFM) results indicated that the height and the average lateral size of PT nanocrystal increased and then decreased as the acac/Pb molar ratio increased. Piezoelectric force microscopy (PFM) results demonstrated that all the samples show obvious piezoelectric activity. These results implied that the acetylacetone molecular mediated the growth of PT nanocrystals on Si (100) substrates possibly by the acac/Pb molar ratio. This simple method has been suggested to be attractive for tailoring an oriented growth of the nanostructures of perovskite oxide systems on Si substrates.

Keywords: Morphology; Si (1; 0; 0) substrate; Acetylacetone; Freeze-drying; Lead titanate nanocrystal

Inhomogeneous optoelectronic and microstructure property distribution across the substrate of ZnO:Al films deposited by room temperature magnetron sputtering by Tao Wang; Xungang Diao; Xuan Wang (pp. 9773-9779).

► Property distributions for low temperature sputtered ZAO films were studied. ► Films from different substrate regions have distinctive properties. ► The uneven distributions are heavily dependent on the substrate–target distance. ► Electrical properties of ZAO have strong relations with (002) and (110) textures.Aluminum doped zinc oxide (ZAO) films were deposited by direct current (DC) reactive magnetron sputtering from a ZnO:Al₂O₃ (3wt.% Al₂O₃) ceramic target at room temperature. In order to explore the inhomogeneous property distribution across the substrate, the films were deposited with varied substrate–target distances ( D_s) ranging from 2cm to 9cm. The experimental results obtained from four-point probe, spectrophotometer, scanning electron microscope, X-ray diffractometer and Auger electronic spectrometer were analyzed to explore the nonuniform property distribution of the obtained ZAO films. The results confirmed that the films’ optoelectronic properties, crystallinity and surface morphology, etc., which were obtained from different substrate areas facing the target were remarkably different. It was revealed that the inhomogeneous property distribution was noticeably dependent on the D_s. It was also suggested that the great difference of electrical conductivity among films from different substrate areas could not be ascribed to the difference of chemical composition, but might be explained by the distinctive crystallinity correspondingly. Films from different substrate regions with distinctive electrical characteristics were either (002) or (110) textured.

Keywords: ZAO film; Magnetron sputtering; Inhomogeneous distribution

Characterization of high temperature conductive graphite surfaces irradiated with femtosecond laser pulses by M. Sivakumar; B. Tan; K. Venkatakrishnan (pp. 9780-9784).

► Weblike nanoparticles aggregate was generated on graphite surfaces due to irradiation of MHz repetition rate femtosecond laser pulses. ► Nanoparticles were formed by nucleation and condensation of vapor in the plasma plume. ► Microraman study shows that the graphite nanoparticles in the fibrous structure were amorphous. ► X-ray photoelectron spectroscopy analysis shows no significant chemical changes in nanoparticles aggregate as compared to bulk.In this study high temperature conductive graphite surfaces irradiated with megahertz pulse repetition rate femtosecond laser pulses under ambient condition were characterized using electron microscopy and spectroscopy techniques. Scanning electron microscopy analysis of the treated surface shows formation of self assembled weblike nanofibrous structure in and around the laser irradiated spots. Further transmission electron microscopy investigation revealed that this structure was formed due to aggregation of graphite nanoparticles. In addition the broadening of microraman peaks at 1340 and 1580cm⁻¹ of the laser irradiated sample was due to confinement of optical phonons in graphite nanoparticles. X-ray photoelectron spectroscopy analysis shows a marginal increase of sp² and sp³ species with laser treated samples as compared to that of untreated samples. The results show that femtosecond laser treatment is rather a simple technique for the direct synthesis graphite nanostructures without significant changes in their chemistry as compared to the bulk.

Keywords: Nanoparticles aggregate; Femtosecond laser; Laser ablation

Surface refinement and electronic properties of graphene layers grown on copper substrate: An XPS, UPS and EELS study by A. Siokou; F. Ravani; S. Karakalos; O. Frank; M. Kalbac; C. Galiotis (pp. 9785-9790).

• Assessment of two treatments of graphene layers in UHV, grown ex situ by CVD on poly Cu foils. • Achievement of atomically clean graphene surfaces. • Morphology and two dimensional character of the films remain intact. • XPS and EELS provide solid spectroscopic evidence on the purity and structural integrity of the graphene layers. • Even mild Ar⁺ sputtering sessions disrupt the sp2 network of graphene. • Annealing at ∼450°C under UHV is lenient way to achieve atomically clean graphene surfaces.The present work focuses on the assessment of two surface treatment procedures employed under ultra high vacuum conditions in order to obtain atomically clean graphene layers without disrupting the morphology and the two dimensional character of the films. Graphene layers grown by chemical vapor deposition on polycrystalline Cu were stepwise annealed up to 750°C or treated by mild Ar⁺ sputtering. The effectiveness of both methods and the changes that they induce on the surface morphology and electronic structure of the films were systematically studied by X-ray photoelectron spectroscopy, and electron energy loss spectroscopy. Ultraviolet photoelectron spectroscopy was employed for the study of the electronic properties of the as received sample and in combination with the work function measurements, indicated the hybridization of the C–π network with Cu d-orbitals. Mild Ar⁺ sputtering sessions were found to disrupt the sp2 network and cause amorphisation of the graphitic carbon. Annealing between 300°C and 450°C under ultra high vacuum proved to be an effective and lenient way for achieving an atomically clean graphene surface. At higher temperatures the rigid structure of graphene does not follow the expansion of the copper substrate leading to the graphene/Cu interface breakdown and possibly to further rippling of the graphene layers leaving bare areas of cooper substrate.

Keywords: Graphene; XPS; EELS; UPS; Copper substrate; Cleaning treatment; UHV

Effect of structure on the photocatalytic activity of Pt-doped TiO₂ nanotubes by Yaling Su; Yirong Deng (pp. 9791-9795).

Display Omitted• TiO₂ nanotubes anodized in 1/12M C₂H₂O₄·2H₂O containing 0.5wt.% NH₄F (electrolyte A) displayed an obvious tubular structure with the average length of 700nm. • TiO₂ nanotubes anodized in anhydrous dimethyl sulfoxide containing 1% HF (electrolyte B) showed the inhomogeneous cracked surface with the average length of 3μm. • Pt-doped TiO₂ anodized in electrolyte B (400°C) showed the highest photocatalytic activity.Highly ordered TiO₂ nanotubes with different tube length were fabricated by anodization using C₂H₂O₄·2H₂O containing 0.5wt.% NH₄F (electrolyte A) and anhydrous dimethyl sulfoxide containing 1% HF (electrolyte B), respectively. Then cathodic reduction method was used to dope Pt in TiO₂ nanotubes in chloroplatinic acid. The results indicated that cathodic reduction could efficiently platinize TiO₂ nanotubes. Pt-doped TiO₂ nanotubes with the longer length had the higher photocatalytic activity for degrading methyl orange under UV and visible irradiation. The longer tube length has a positive effect on the photocatalytic activity of Pt-doped TiO₂ nanotubes. Besides, as the content of anatase further decreases, the photocatalytic activity drops gradually due to the reduction reaction in the surface area.

Keywords: TiO; ₂; nanotubes; Structure; Pt-doping; Catalytic properties

Synthesis of CdS nanocrystals by a microwave activated method and investigation of the photoluminescence and electroluminescence properties by M. Molaei; E. Saievar Iranizad; M. Marandi; N. Taghavinia; R. Amrollahi (pp. 9796-9801).

► The method is microwave activated method. ► The method results in luminescent CdS NCs with sizes around 3nm and surface trap state white luminescence. ► The method is very fast and synthesis process is done less than 5min. ► PL QY of NCs is 10%. This amount is near to the obtained amount for chemically synthesized NCs. ► Synthesized NCs were used as emissive layer in a light emitting device with ITO/PEDOT-PSS/PVK/CdS/AL structure ► Fabricated device showed a white emission with (0.34, 0.43) CIE coordinates.We have synthesized CdS nanocrystals (NCs) by a microwave activated method. CdSO₄ and Na₂S₂O₃ were used as the precursors and thioglycolic acid (TGA) was used as capping agent molecule. The aqueous synthesis was based on the heat sensitivity of Na₂S₂O₃. In this method, microwave irradiation creates the activation energy for dissociation of Na₂S₂O₃ and leads to the CdS NCs formation. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses demonstrated hexagonal phase CdS NCs with an average size around 3nm for sample prepared at 5min irradiation time. A band gap range of 3.38–2.89eV was possible only by increasing the microwave irradiation time, corresponding to a 2.7–3.7nm size. Photoluminescence (PL) spectra showed a white emission between 400 and 750nm. The best attained PL quantum yield (QY) of the NCs was about 10%. Synthesized NCs were used as emissive layer in a light emitting device (LED) with ITO/PEDOT:PSS/PVK/CdS-NCs/AL structure. Turn on voltage of fabricated device was about 7V. The CIE color coordinate of the LED at (0.34, 0.43) demonstrated a near white light LED with an emission on green-yellow boundary of white.

Keywords: Synthesis; CdS nanostructures; Microwave irradiation; Light emitting device

Synthesis and characterization of ionic liquid-functionalized alumino-silicate MCM-41 hybrid mesoporous materials by Chao Cai; Hua Wang; Jinyu Han (pp. 9802-9808).

Display Omitted► Bifunctional MCM-41 was synthesized by two-step approach including in situ skeleton doping and post surface grafting. ► Aluminium was introduced into the framework of MCM-41 generating Lewis and Brönsted acid sites. ► Ionic liquid groups were grafted onto the surface of MCM-41 covalently. ► The synergistic effect of aluminium and ionic liquid groups on the catalytic activity for the coupling reaction of CO₂ and PO.Ionic liquid-functionalized alumino-silicate MCM-41 hybrid mesoporous materials have been synthesized with two-step approach, by means of in situ skeleton doping with aluminium and post surface grafting with N-methylimidazole ionic liquid groups. The samples were characterized by X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), N₂ adsorption–desorption, Fourier transform infrared (FTIR) spectra,²⁷Al and¹³C MAS NMR spectra and temperature-programmed desorption (TPD) of NH₃. The results indicated that the bifunctionalized MCM-41 possessed ordered mesostructure. Aluminium was efficiently introduced into the framework of the mesostructure, generating Lewis and Brönsted acid sites. N-methylimidazole ionic liquid groups were covalently grafted onto the surface of mesoporous materials. The as-synthesized bifunctional MCM-41 showed good catalytic performance in the coupling reaction of CO₂ and propylene oxide.

Keywords: Mesoporous materials; Functionalized MCM-41; Surface grafting; Skeleton doping

Application of bifunctional Saccharomyces cerevisiae to remove lead(II) and cadmium(II) in aqueous solution by Yunsong Zhang; Weiguo Liu; Li Zhang; Meng wang; Maojun Zhao (pp. 9809-9816).

► The EDTAD-functionalized Saccharomyces cerevisiae (EMS) was prepared. ► EMS was used to dispose the waste water of lead(II) and cadmium(II). ► The adsorption/desorption mechanism of EMS for lead(II) and cadmium(II) was studied.A magnetic adsorbent, EDTAD-functionalized Saccharomyces cerevisiae, has been synthesized to behave as an adsorbent for heavy metal ions by adjusting the pH value of the aqueous solution to make carboxyl and amino groups protonic or non-protonic. The bifunctional Saccharomyces cerevisiae (EMS) were used to remove lead(II) and cadmium(II) in solution in a batch system. The results showed that the adsorption capacity of the EMS for the heavy metal ions increased with increasing solution pH, and the maximum adsorption capacity (88.16mg/g for Pb²⁺, 40.72mg/g for Cd²⁺) at 10°C was found to occur at pH 5.5 and 6.0, respectively. The adsorption process followed the Langmuir isotherm model. The regeneration experiments revealed that the EMS could be successfully reused.

Keywords: Saccharomyces cerevisiae; Nano-Fe; ₃; O; ₄; EDTAD; Adsorption; Functionalization

Conducting polymer film-based immunosensors using carbon nanotube/antibodies doped polypyrrole by Phuong Dinh Tam; Nguyen Van Hieu (pp. 9817-9824).

► Goat-IgGs immobilized on sensor surface using electrochemical techniques. ► The effect parameters of electropolymerization process on immunosensor response are also studied. ► It found that the immunosensor well active in 1.5mgml⁻¹ CNT concentration, 2.5mM pyrrole, 10μgml⁻¹ goat IgGs. ► Detection limit as low as 0.05μgml⁻¹ and a response time of 1min.Carbon nanotube/polypyrrole/antibodies polymer films were synthesized successfully on microelectrodes by electrochemical deposition. Electropolymerization was performed at optimal range between −0.8 and +0.8V at a scan rate of 50mVs⁻¹ in an electrochemical mini-cell containing monomer pyrroles, carbon nanotubes, and goat IgGs. The conducting polymer films were characterized by Fourier transform infrared spectrometry, Raman spectra, and Field emission scanning electron microscopy. And then, it was prepared for immunosensor application to determine anti-goat IgGs. The results show that a linear range between 0.05 and 0.7μgml⁻¹ for anti-goat IgGs detection was observed for immunosensor, a detection limit as low as 0.05 μgml⁻¹ and a response time of 1min. The effect parameters of electropolymerization process on immunosensor response are also studied. It found that the immunosensor well active in 1.5mgml⁻¹ CNT concentration, 2.5mM pyrrole, 10μgml⁻¹ goat IgGs.

Keywords: Immunosensor; Polypyrrole; Antigen; Antibody; Electrochemical

Study on the preparation and electrical properties of NTC thick film thermistor deposited by supersonic atmospheric plasma spraying by Sen Liang; Xiao Zhang; Yu Bai; ZhiHai Han; Jianfeng Yang (pp. 9825-9829).

► The Ni_0.6Mg_0.3Mn1.5−_xAl0.6+_xO4 (0≤ x≤0.6) films were first deposited by SAPS method. ► The as-sprayed films were composed of nanostructured grains. ► All the as-sprayed films showed NTC thermistor characteristic.In the present work, a series of thick Ni_0.6Mg_0.3Mn1.5−_xAl0.6+_xO₄( x=0, 0.1, 0.2, 0.4, 0.6) films (50±10μm) with negative temperature coefficient (NTC) were firstly deposited by newly developed high efficiency supersonic atmospheric plasma spray (SAPS) method. The phase, microstructure and electrical properties of films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and two-probe technique. The results showed that all the films were composed of cubic spinel structure, and the MgAl₂O₄ phase increased with increasing the Al₂O₃ content in the original powders. In addition, the films showed a dense and smooth surface with some pores in the grain boundaries. All the as-sprayed films showed a linear relationship between ln resistivity and reciprocal of absolute temperature (1/ T) in the temperature range from 25°C to 220°C, which indicated a NTC characteristic.

Keywords: NTC; Film; SAPS; Electrical properties; Thermistor

Thermal relaxation behavior of residual stress in laser hardened 17-4PH steel after shot peening treatment by Zhou Wang; Yanhua Chen; Chuanhai Jiang (pp. 9830-9835).

► Thermal relaxation investigation was carried out on tempered and laser hardened 17-4PH. ► The relaxation process of residual stress during isothermal annealing could be described by Zener–Wert–Avrami function. ► Because of the pinning effects of ɛ-Cu precipitates on the dislocations movements, the thermal stability of residual stresses in tempered 17-4PH was higher than that in laser hardened 17-4PH and that in α-iron.In order to investigate the residual stress relaxations of shot peened layer, isothermal annealing treatments were carried out on tempered and laser hardened 17-4PH steel after shot peening with different temperatures from 300°C to 600°C. The results showed that the residual stresses were relaxed in the whole deformation layer especially under higher temperature. The maximum rates of stress relaxation took place at the initial stage of annealing process in all conditions. The relaxation process during isothermal annealing could be described by Zener–Wert–Avrami function. The thermal stability of residual stress in tempered 17-4PH was higher than that in laser hardened 17-4PH as well as that in α-iron, which was due to the pinning effects of ɛ-Cu precipitates on the dislocation movement. As massive ɛ-Cu precipitates formed in the temperature about 480°C, the activation enthalpies for stress relaxation in laser hardened 17-4PH were the same as that in tempered 17-4PH in the conditions of isothermal annealing temperatures of 500°C and 600°C.

Keywords: Tempered and laser hardened 17-4PH steel; Shot peening; Thermal relaxation; ɛ-Cu precipitate

Surface chemistry of atmospheric plasma modified polycarbonate substrates by Houman Yaghoubi; Nima Taghavinia (pp. 9836-9839).

.Display Omitted► We studied the surface chemistry of atmospheric plasma treated PC substrates. ► Compressed air was used as a cheap and available gas source. ► Effect of different plasma parameters on obtained water contact angle was studied. ► Plasma created more divergent O₂ containing groups compared to chemical treatment. ► Surface roughness increased after treatment causing slight decrease in transmission.Surface of polycarbonate substrates were activated by atmospheric plasma torch using different gas pressure, distance from the substrates, velocity of the torch and number of treatments. The modifications were analyzed by contact angle measurements, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and UV–vis spectrophotometry. Plasma treatment caused the surface characteristics to become more hydrophilic as measured by the water contact angle, which decreased from 88° to 18°. The decrease in contact angle was mainly due to oxidation of the surface groups, leading to formation of polar groups with hydrophilic property. XPS results showed an increase in the intensity of –(C–O)– groups and also introduction of new functional groups i.e. –(O–CO)– after the treatment process. AFM topographic images demonstrated an increase in the rms roughness of the surface from 2.0nm to 4.0nm caused by the treatment. Increase in rms roughness of the surface caused relevant decrease in transmission up to ∼2–5%.

Keywords: Atmospheric pressure plasma; Surface modification; Hydrophilic; Hydrophobic; Polar groups

Effects of high hydrogen dilution ratio on optical properties of hydrogenated nanocrystalline silicon thin films by Liqiang Guo; Jianning Ding; Jichang Yang; Guanggui Cheng; Zhiyong Ling; Ningyi Yuan (pp. 9840-9845).

► In this paper, on the basis of two peaks gaussian fitting, three peaks fitting calculation method for the hydrogen content is proposed. ► We comparison both of them and we find the latter calculation results is more accurately than the former. ► We study the influence of the high hydrogen dilution ratio RH to the nanocrystalline silicon thin films, surface characteristics, the thin films optical properties and the hydrogen content of nanocrystalline silicon thin films, and we analysis the influence mechanism of the high hydrogen dilution ratio RH to hydrogen content.Hydrogenated nanocrystalline silicon thin films were prepared by plasma enhanced vapor deposition technique. In our experiment, hydrogen dilution ratio R_H was changed mainly, while the other parameters, such as the radio frequency power, the direct current bias value, the chamber pressure, the total gas flow and the substrate temperature were kept constant. The film's surface topography was gained by AFM. The chemical bond was confirmed by Fourier transform infrared spectra. The optical properties were characterized by transmission spectra. To consider absorption peak of stretching vibration mode of SiH₃ at 2140cm⁻¹ and to reduce the calculation error, a hydrogen content calculation method was proposed. Effects of hydrogen dilution ratio on the deposition rate v and hydrogen content C_H were investigated. The bonding mode and the force constants k of chemical bond, the structural factor f in films were changed by high hydrogen dilution ratio, which gave rise to the shift of absorption peak of infrared stretching mode and the decrease of optical band gap E_g.

Keywords: Hydrogen content; Optical properties; Hydrogenated nanocrystalline silicon films; Structure factor; Surface topography

Surfactant assisted surface studies of zinc sulfide nanoparticles by Ashutosh K. Shahi; B.K. Pandey; R.K. Swarnkar; R. Gopal (pp. 9846-9851).

• Polydisperse ZnS nanoparticles are successfully synthesized by chemical route using CTAB as a surfactant. • CTAB does not influence the crystal structure of ZnS nanoparticles but the lattice contraction occurs between the Zn–S. • PL emissions are observed around 387, 410, 489, and 528nm. All these transitions correspond to surface vacancies and defect states. • Raman peaks at 320, 615, and 700cm⁻¹ are found. These are observed due to surface phonon mode.We report a simple soft chemical method for the synthesis of ZnS nanoparticles using varying concentration of cationic surfactant CTAB and examine its surface properties. Powder X-ray diffraction, UV–vis spectroscopy, photoluminescence spectroscopy, selective area electron diffraction, and transmission electron microscopy are used to characterize the as prepared ZnS nanoparticles. XRD and TEM measurements show the size of polydispersed ZnS nanoparticles is in the range of 2–5nm with cubic phase structure. The photoluminescence spectrum of ZnS nanoparticles exhibits four fluorescence emission peaks centered at 387nm, 412nm, 489nm and 528nm showing the application potential for the optical devices. In Raman spectra of ZnS nanoparticles, the modes around 320, 615 and 700cm⁻¹ are observed.

Keywords: II–VI Semiconductors; Nanomaterials; Electronic band structures; Optical properties; Raman spectroscopy

Effect of surface oxidation on the surface condition and deuterium permeability of a palladium membrane by Wei Feng; Ying Liu; Lixian Lian; Lixia Peng; Jun Li (pp. 9852-9857).

► Pd membranes will be oxidized at 240°C, and completed oxidized when the temperature rose to 390°C. ► When the temperature further rose to 500°C, the granular PdO will form on Pd membrane surface. ► All the PdO formed on Pd membrane surface will be deoxidized completely in H₂ at room temperature. ► After deoxidation, the surface is become shrinkage, and the rough surface structure still remain. ► The rough membrane has higher hydrogen permeability than the original Pd membrane.Oxidation and deoxidation of a Pd membrane was conducted in a quartz tube oven in a temperature range of 23–500°C. The micromorphology and chemical composition of the Pd membrane surface was characterized using scanning electronic microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Micropores and PdO began to form on the Pd membrane surface after oxidation at 240°C for 1h and their quantity increased gradually with increasing temperature. A rough Pd membrane surface was obtained when the temperature rose to 500°C. The PdO on the Pd membrane surface was completely deoxidized once more using H₂ at room temperature, but the rough surface morphology caused by oxidation remained. The deuterium permeability of the Pd membrane was tested using special equipment in the China National Key Laboratory and the results indicated that the rough Pd membrane surface had higher deuterium permeability than the original membrane. The improved deuterium permeability could be attributed to the higher Pd membrane surface area, which provided deuterium atoms with more adsorption sites and dissociation sites.

Keywords: Deuterium permeability; Pd membrane; Surface; Oxidation

Texture evolution of cholesteric liquid crystal driven by a thermal process by H.K. Lin; Y.F. Huang; A.C. Chen; P.W. Liu (pp. 9858-9862).

.Display Omitted► A Ch-LCD can be driven by a thermal process. ► The texture of the cholesteric liquid crystal will be transfrred from planar to focal conic. ► The reflectance of a Ch-LCD is influenced by texture after the thermal process. ► After thermal treatment at 90°C, a chain tilting angle of ∼29°.Cholesteric liquid crystal displays (Ch-LCDs) have potential as screens in portable readers. In the present study, it is demonstrated that a Ch-LCD can be driven by a thermal process at a temperature of 90°C. At a suitable temperature, the texture of the cholesteric liquid crystal will be transfrred from planar to focal conic. The experimental results show that the reflectance of a Ch-LCD is influenced by texture after the thermal process. After thermal treatment at 90°C, the periodicity was reduced from 63nm to 55nm. A chain tilting angle of ∼29° was estimated.

Keywords: Cholesteric liquid crystal display (Ch-LCD); X-ray; Ag layer

Plasma surface modification of nanofiltration (NF) thin-film composite (TFC) membranes to improve anti organic fouling by Eun-Sik Kim; Qingsong Yu; Baolin Deng (pp. 9863-9871).

• Low-pressure NH₃ plasma treatment of commercial thin-film composite membranes. • Surface hydrophilicity and charge are dominant factors for membrane organic fouling. • Less fouled protein and humic acid are caused by the enhanced surface properties. • Higher salt rejection was achieved by the plasma-induced surface cross-linking.Commercial nanofiltration (NF) thin-film composite (TFC) membranes were treated by low-pressure NH₃ plasma, and the effects of the plasma treatment were investigated in terms of the membrane hydrophilicity, pure water flux, salt rejection, protein adsorption, and humic acid fouling. Experimental results indicated that the membrane surface hydrophilicity was increased by the plasma treatment, and changes in the hydrophilicity as well as membrane performance including permeate flux and fouling varied with the original membrane characteristics (e.g., roughness and hydrophilicity). Water flux of plasma treated membranes was the highest with 10min and 90W of plasma treatment, and salt rejection was mainly affected by the intensity of the plasma power. Results of bovine serum albumin (BSA) adsorption demonstrated that the protein adsorption decreased with increasing plasma treatment time. The plasma treatment that resulted in more negatively charged surfaces could also better prevent Aldrich humic acid (AHA) attachment on the membrane surface.

Keywords: Thin-film composite; NH; ₃; plasma treatment; Hydrophilicity; Bovine serum albumin adsorption; Humic acid fouling

Direct imprinting of ordered and dense TiO₂ nanopore arrays by using a soft template for photovoltaic applications by Peng Zhong; Wenxiu Que; X. Hu (pp. 9872-9878).

• Ordered TiO₂ nanopore arrays can be imprinted by using a PMMA/PDMS template. • Vacuum-assisted infiltration ensures complete filling of PMMA into AAO pores. • Freeze-drying assists in obtaining PMMA nanorods with higher aspect ratio. • The diameter of the imprinted TiO₂ nanopores can be adjusted from 30nm to 300nm. • The imprinted TiO₂ nanopore arrays can enhance solar cell performance.Highly ordered and dense TiO₂ nanopore arrays are directly nanoimprinted on a transparent conductive glass substrate by using a polymethylmethacrylate/polydimethylsiloxane (PMMA/PDMS) composite soft template, which is replicated from an anodic aluminum oxide (AAO) replica mold. Results indicate that heat infiltration under vacuum conditions can ensure complete filling of PMMA into the AAO pores, and that free-standing PMMA nanorods with an aspect ratio more than 5 can be obtained by adjusting the AAO pore depth based on a freeze-drying technique. TiO₂ nanopore arrays with different diameters from 30 to 300nm and inter-pore distances between 70 and 450nm can be easily fabricated by using the corresponding templates with different sizes. Preliminary solar cells are also assembled with a heterojunction of conjugated polymer/TiO₂ nanopore arrays. Results indicate that the construction of poly-(3-hexylthiophene) (P3HT)/TiO₂ nanopore arrays can be more helpful in quenching the PL emission of P3HT than that of P3HT/flat TiO₂ film, and a maximum efficiency of about 0.32% can be obtained for a photovoltaic device with a TiO₂/[6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM)/P3HT structure.

Keywords: Nanoimprint; TiO; ₂; nanopore array; Soft template; Anodic aluminum oxide; Solar cell

Synthesis of [Ru₃( μ₃-NPh)(Br)(CO)₉]⁻ on self-assembled monolayers of di(3-aminopropyl)viologen/ITO surfaces and its application to photoelectrochemical cells by Deok Yeon Lee; Mi-Sun Lee; Iseul Lim; Soon Hyung Kang; Yoon-Chae Nah; Wonjoo Lee; Sung-Hwan Han (pp. 9879-9884).

• Triruthenium carbonyl clusters were synthesized on DAPV/ITO using surface reaction. • Ru₃(CO)₁₂ then easily reacted with the Br- of DAPV, and a mixture of Ru-1 and Ru-2 was formed on DAPV/ITO. • Furthermore, Ru-3 was successfully anchored on DAPV/ITO by adding nitrosobenzene in order to react with Ru-2 on DAPV/ITO. • The photocurrents of (Ru-1 and Ru-2)/DAPV/ITO and Ru-3/DAPV/ITO were 6.3nA/cm² and 8.6nA/cm², respectively.Triruthenium carbonyl clusters {[Ru₃(Br)(CO)₁₁]⁻ (denoted as Ru-1), [Ru₃( μ₂-Br)(CO)₁₀]⁻ (denoted as Ru-2), and [Ru₃( μ₃-NPh)(Br)(CO)₉]⁻ (denoted as Ru-3)} were synthesized on di(3-aminopropyl)viologen (DAPV)/indium tin oxide (ITO) using a surface reaction in a ruthenium (III) carbonyl [Ru₃(CO)₁₂] solution, and were applied to photoelectrochemical cells (PECs) at the molecular level. The formation of DAPV on ITO was realized in the form of self-assembled monolayers. Ru₃(CO)₁₂ then easily reacted with the Br⁻ of DAPV, and a mixture of Ru-1 and Ru-2 was formed on DAPV/ITO. Furthermore, Ru-3 was successfully anchored on DAPV/ITO by adding nitrosobenzene in order to react with Ru-2 on DAPV/ITO. The photocurrents of (Ru-1 and Ru-2)/DAPV/ITO and Ru-3/DAPV/ITO in PECs at the molecular level were 6.3nAcm⁻² and 8.6nAcm⁻², respectively. The quantum yield of Ru-3/DAPV/ITO was ∼0.8%. Time-resolved photoluminescence spectroscopy and emission spectroscopy were recorded to bring out the photoinduced charge transfer process from ruthenium clusters to DAPV.

Keywords: Surface modification; Metal cluster; Photoelectrochemical cell; Photoinduced charge transfer; Self-assembled monolayer

Nanoscale resistive random access memory consisting of a NiO nanodot and Au nanowires formed by dip-pen nanolithography by Jong Yeog Son; Yun-Sok Shin; Young-Han Shin (pp. 9885-9887).

► A Au/NiO/Au nanowire resistive switch is formed on terrace edges by dip-pen nanolithography. ► The dip-pen nanolithography provides a resistive switch with a precision of a few nm. ► The Au/NiO/Au nanowire resistive switch exhibits unipolar switching characteristics.We demonstrate the nanoscale resistive random access memory (RRAM) element consisting of an approximately 30nm diameter NiO nanodot and two bridging Au nanowires, formed by a dip-pen nanolithography technique using nickel carbonate (Ni₂(CO₃)(OH)₂) and [AuCl₄]⁻ complex solutions, respectively. The Au/NiO/Au nanowire resistive switch exhibits typical unipolar switching characteristics with high performance at low Set and Reset voltages.

Keywords: NiO nanowire; NiO RRAM; NiO resistive switch; Dip-pen nanolithography

Hydroxyapatite/polyamide66 porous scaffold with an ethylene vinyl acetate surface layer used for simultaneous substitute and repair of articular cartilage and underlying bone by Xiaobing Luo; Li Zhang; Yos Morsi; Qin Zou; Yanying Wang; Shibo Gao; Yubao Li (pp. 9888-9894).

The repaired process of HA/ polyamide66 porous scaffold with an ethylene vinyl acetate surface layer composite material [(a) TEM photograph of nHA crystals, (b) camera photo of EVA/HA-PA66 composite, (c) schematic diagram of the fabrication process, (d, f) SEM micrographs of HA-PA66 scaffold].Display Omitted• EVA is used for substitute and repair of articular cartilage. • Wettability, friction and wear properties of the surface of EVA were studied. • Bilayered structure of EVA layer and nHA-PA66 porous scaffold was designed. • Articular cartilage and underlying bone were repaired simultaneously.In this paper, tissue scaffold made from polyamide66 (PA66) and hydroxyapatite (HA) was prepared by co-precipitation and thermal-induced phase inversion method, in which biomimetic HA crystals were uniformly distributed in PA66 matrix. The porosity of the scaffold is about 81% and the macropore size is from 50 to 500μm. The ethylene vinyl acetate (EVA) layer was thermally molded on one surface of HA-PA66 scaffold to develop EVA/HA-PA66 composite for articular cartilage/bone substitute, i.e., upper EVA layer for cartilage substitute and underlying HA-PA66 scaffold for bone bonding and fixation. The physicochemical and mechanical properties of EVA were also investigated. The results indicate that the tensile and compressive strength of EVA is about 4.65MPa and 9.44MPa respectively, while its mean friction coefficient is very small, only about 0.23. The cell culture of EVA and HA-PA66 scaffold shows that these materials possess good cytocompatibility. The proposed preparation method is novel and effective, and the EVA/HA-PA66 composite has good potential for simultaneous substitute of articular cartilage and underlying bone.

Keywords: Tissue scaffold; Hydroxyapatite; Polyamide66; Ethylene vinyl acetate; Cartilage and bone

Study on the adsorption behavior of γ-GPS on low carbon steel surfaces using RA-IR, EIS and AFM by Lixia Yang; Mingxing Liu; Xiaoli Lei; Yuxin Zhang (pp. 9895-9903).

• Adsorption of γ-GPS exhibited oscillatory phenomenon. • Growth behavior of γ-GPS film was closely related to adsorption capacity of silanols. • Strong interaction among silanols generated highly ordered and excellent γ-GPS film. • Proposed adsorption models were used to simulate the observed experimental phenomena.The adsorption behavior of γ-GPS on low carbon steel surfaces was systematically investigated by reflection absorption infrared spectroscopy (RA-IR), electrochemical impedance spectroscopy (EIS) and atomic force microscopic (AFM), focusing on the changes in γ-GPS chains alignment during the adsorption process and the influence of assembly time on the chemical structures, three-dimension morphology and corrosion resisting property of γ-GPS films. The results indicated that the adsorption of γ-GPS exhibited an oscillatory phenomenon, which experienced rapid adsorption firstly, then reached maximum adsorption capacity, subsequently suffered extensive desorption, finally went through irreversible slow adsorption. The growth behavior and protective performance of γ-GPS films was closely related to the adsorption capacity and the alignment of silanol monomers. As more silanol monomers were adsorbed, the stronger the intermolecular van der Waals interactions between the γ-GPS chains would be, resulting in highly ordered γ-GPS films with excellent performance. The proposed adsorption models were used to simulate the experimental phenomena and determine the adsorption mechanisms taking place on the low carbon steel surfaces.

Keywords: Adsorption; γ-GPS; Oscillatory; Protective performance

Structure and tribological performance by nitrogen and oxygen plasma based ion implantation on Ti6Al4V alloy by Xingguo Feng; Mingren Sun; Xinxin Ma; Guangze Tang (pp. 9904-9908).

• Between the outmost layer and metallic substrate are TiO₂, TiO, Ti₂O₃, TiN and Al₂O₃. • Hardness and wear resistance of the implanted layer increases with implanted voltage. • Wear rate of sample implanted N₂–O₂ at −50kV decreases eight times than untreated one. • Wear resistance of implanted N₂–O₂ is better than the same condition implanted O₂. • Wear mechanism changes to ploughing wear when implanted voltage.Ti6Al4V alloy was implanted with nitrogen–oxygen mixture by using plasma based ion implantation (PBII) at pulsed voltage −10, −30 and −50kV. The implantation was up to 6×10¹⁷ions/cm² fluence. The changes in chemical composition, structure and hardness of the modified surfaces were studied by XPS and nanoindentation measurements. According to XPS, it was found that the modified layer was predominantly TiO₂, but contained small amounts of TiO, Ti₂O₃, TiN and Al₂O₃ between the outmost layer and metallic substrate. Surface hardness and wear resistance of the samples increased significantly after PBII treatment, the wear rate of the sample implanted N₂–O₂ mixture at −50kV decreased eight times than the untreated one. The sample implanted N₂–O₂ mixture showed better wear resistance than that of the sample only implanted oxygen at−50kV. The wear mechanism of untreated sample was abrasive-dominated and adhesive, and the wear scar of the sample implanted at −50kV was characterized by abrasive wear-type ploughing.

Keywords: PBII; Ti6Al4V alloy; Structure; Tribological performance

Study of microstructure and nanomechanical properties of Zr films prepared by pulsed magnetron sputtering by Akash Singh; P. Kuppusami; R. Thirumurugesan; R. Ramaseshan; M. Kamruddin; S. Dash; V. Ganesan; E. Mohandas (pp. 9909-9914).

• Development of Zr metallic films by pulsed DC magnetron sputtering is reported. • Zr films revealed predominantly [001] texture. • Hexagonal shaped crystallites seem to grow along the surface normal of the substrate for the films deposited at 773K. • Hardness of the films is in the range 6–10GPa. • The scratch test indicated the films deposited at higher substrate temperatures had excellent bonding with the substrate.The present work studies the effect of substrate temperature on the growth characteristics of zirconium films prepared by pulsed magnetron sputtering. Formation of α-phase of zirconium was observed in the temperature range 300–873K. X-ray diffraction of Zr films revealed predominantly [001] texture. It is noticed that crystallite size increases with increasing substrate temperature. Hexagonal shaped crystallites seem to grow along the surface normal of the substrate for the films deposited at 773K. Nanoindentation measurements showed that the hardness of the films is in the range 6–10GPa. The scratch test indicated that the films deposited at higher substrate temperatures had excellent bonding with the substrate and no significant critical failure was noticed up to an applied load of 20N.

Keywords: Sputtering; Zirconium; X-ray diffraction; Nanohardness; Scratch test

Synthesis surface effects on the stress and deformation of film/substrate system by Shan-Shan Shao; Fu-Zhen Xuan; Zhengdong Wang; Shan-Tung Tu (pp. 9915-9920).

• At nanoscale, the roughened surface effects on stress and deformation become considerable with increasing the surface-to-bulk ratio. • A general theoretical model is developed for the bending curvature and residual stress of film/substrate structure with the roughened surface effects. • With decreasing the thickness of film, the synthesis surface effect may switch the direction of stress and deformation.The closed-form solutions of bending curvature and stress distribution in film/substrate system with the synthesis surface effect are proposed by minimizing the total potential energy. Effects of the roughness and the residual surface stress on stress in film are addressed. Results reveal that, at a given thickness of the substrate, effects of roughness and residual surface stress on the bending curvature become significant with decreasing the film thickness. The roughing surface will enlarge the magnitudes of bending curvature and film stress. The direction change of residual surface stresses can lead to a reversed bending of film/substrate system.

Keywords: Surface roughness; Stress; Film/substrate system

Improvement of the corrosion behavior of low carbon steel by laser surface alloying by B. Abdolahi; H.R. Shahverdi; M.J. Torkamany; M. Emami (pp. 9921-9924).

• Laser processing of hot dipped steel formed Fe₃Al and FeAl intermetallics. • Corrosion resistance of dipped steel increased 2 times after laser processing. • Corrosion resistance of base steel increased 5 times after laser processing.In the present study, an integrated layer of iron aluminides of FeAl and Fe₃Al was formed on the surface of a low carbon steel sheet by a two-step process. The first step was hot dipping of the steel in a molten aluminum pool and secondly laser surface processing using a pulsed Nd:YAG laser. The corrosion resistance of the coated specimens was evaluated by activation polarization and Tafel methods. The results show that laser processing of the aluminized steel leads to a considerable increase in its corrosion resistance compared to both uncoated and merely aluminized materials.

Keywords: Corrosion resistance; Aluminized steel; Laser surface alloying; Low carbon steel

A different approach in sample preparation method for metallic contamination study by ToF-SIMS and TXRF by E.P. Ferlito; S. Alnabulsi; D. Mello (pp. 9925-9930).

• We propose a method to realize reliable reference samples for ToF-SIMS quantitative analysis of metallic contaminants. • We compare ToF-SIMS and TXRF results. • We study the effects of sample aging. • The contaminant migration towards the interface between oxide and silicon significantly impacts the quantification correctness.We propose a methodology to realize reliable reference samples for ToF-SIMS quantitative analysis of metallic contaminants. The procedure consists of spinning a Co contaminated solution, for which the contaminant concentration has been previously determined by ICP-MS, on a clean Si-wafer with a thin surface oxide obtained by SC1 treatment. We have compared the ToF-SIMS results with TXRF and we have demonstrated the validity of the procedure. We have also evidenced the effects of sample aging on the measurements showing that contaminant migration towards the interface between oxide and silicon can significantly impact on the quantification correctness.

Keywords: ToF-SIMS; TXRF; Cobalt contamination

Synthesis and characterization of GaN nanowires by a catalyst assisted chemical vapor deposition by Xiaofeng Wei; Feng Shi (pp. 9931-9934).

► Single-crystalline GaN nanowires are successfully synthesized by CVD on Si(111) substrates coated with NiCl₂ thin films. ► Five first-order Raman active phonon bands move to low shift and A₁(TO), E₁(TO), and E₂ (high) bands are overlapped and broaden. ► Five non-first-order active Raman phonons appear, which is caused by the small dimension and high surface disorder degree.GaN nanowires have been fabricated on Si(111) substrates by chemical vapor deposition (CVD) method with NiCl₂ as catalyst and their compositions, microstructures, morphologies and light emitting properties were characterized by X-ray diffraction (XRD), FT-IR spectrophotometer (FTIR), scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), Raman spectroscopy and photoluminescence (PL). The results demonstrate that the nanowires are single-crystal GaN with hexagonal wurtzite structure and high crystalline quality, having the size of 20–50nm in diameter and several tens of microns in length with some nano-droplets on their tips, which reveals that the growth mechanism of GaN nanowires agrees with vapor–liquid–solid (VLS) process. Five first-order Raman active phonon bands move to low shift and A₁(TO), E₁(TO), and E₂ (high) bands are overlapped and broaden, which is caused by uncertainty in the phonon wave vector. Five non-first-order active Raman phonons also appear, which is caused by the small dimension and high surface disorder degree. A blue-shift of the band-gap emission occurs due to quantum confinement effect.

Keywords: GaN nanowires; Chemical vapor deposition; Crystal growth; Crystal structure; Light emitting properties

Laser cleaning of 19th century Congo rattan mats by N. Carmona; M. Oujja; H. Roemich; M. Castillejo (pp. 9935-9940).

• In this study we present a laser cleaning approach for the restoration of 19th century rattan mats. • We found an efficient removal of the dark carbonaceous soiling while maintaining the original substrate with the second harmonic of a Q-switched Nd:YAG laser. Safe fluence range was defined between 0.4 and 0.6Jcm⁻². • Additional SEM and UV–vis spectroscopy helped to the observation of irradiated surfaces. • Preliminary laboratory tests and optimization of all parameters involved are essential for the best laser cleaning of cultural heritage objects.There is a growing interest by art conservators for laser cleaning of organic materials, such as wooden artworks, paper and textiles, since traditional cleaning with solvents can be a source of further decay and mechanical cleaning may be too abrasive for sensitive fibers. In this work we present a successful laser cleaning approach for 19th century rattan mats from the Brooklyn Museum collection of African Art, now part of the study collection at the Conservation Center in New York. Tests were carried out using the fundamental (1064nm) and second harmonic (532nm) wavelength of a Q-switched Nd:YAG laser to measure threshold values both for surface damage and color changes for different types of rattan samples. The irradiated substrates were investigated by optical microscopy, scanning electron microscopy and by UV–vis spectroscopy in order to determine the efficiency of laser cleaning and to assess possible deterioration effects that may have occurred as a result of laser irradiation. The study showed that by using the laser emission at 532nm, a wavelength for which photon energy is below the bond dissociation level of the main cellulosic compounds and the water absorption is negligible, it is possible to select a range of laser fluences to remove the black dust layer without damaging the rattan material.

Keywords: Laser cleaning; Rattan; Scanning electron microscopy; UV–vis spectroscopy; Museum objects

Dry air effects on the copper oxides sensitive layers formation for ethanol vapor detection by A. Labidi; A. Bejaoui; H. Ouali; F. Chaffar Akkari; A. Hajjaji; M. Gaidi; M. Kanzari; B. Bessaïs; M. Maaref (pp. 9941-9945).

► Conductivity measurements permit to identify exactly when copper oxide formation begins. ► Conductivity and XRD showed that Cu became oxides for temperatures greater or equal to 250°C. ► Crystallite sizes of annealed Cu layers increase when the annealing temperature increases. ► The annealing under dry air gives the best sensitive layers for ethanol gas sensor.The copper oxide films have been deposited by thermal evaporation and annealed under ambient air and dry air respectively, at different temperatures. The structural characteristics of the films were investigated by X-ray diffraction. They showed the presences of two hydroxy-carbonate minerals of copper for annealing temperatures below 250°C. Above this temperature the conductivity measurements during the annealing process, show a transition phase from metallic copper to copper oxides. The copper oxides sensitivity toward ethanol were performed using conductivity measurements at the working temperature of 200°C. A decrease of conductivity was observed under ethanol vapor, showing the p-type semi-conducting characters of obtained copper oxide films. It was found that the sensing properties of copper oxide toward ethanol depend mainly on the annealing conditions. The best responses were obtained with copper layers annealed under dry air.

Keywords: Dry air; Copper oxides; XRD investigations; DC conductivity; Ethanol sensor

The influence of residual gas on boron carbide thin films prepared by magnetron sputtering by Hui Jiang; Jingtao Zhu; Qiushi Huang; Jing Xu; Xiaoqiang Wang; Zhanshan Wang; Slawka Pfauntsch; Alan Michette (pp. 9946-9952).

• Several B₄C single layers and W/B₄C multilayers were deposited in 3 different base vacuums and 2 improved technologies. • Better base pressure leads to lower oxygen impurity. • Impurities do not change the B/C ratios in the films and include 2% Ar and less than 1% Ni. • According to the overlapping binding energy curves, the oxygen atoms are mainly in the form of boron oxides. • Ti sputtering improves the film purity and the optical performance.Boron carbide (B₄C) thin films were prepared by magnetron sputtering and residual gas impurities in the films were analyzed by X-ray photoelectron spectroscopy. The impurities, mainly oxygen, decrease with improving vacuum. By using argon ion beam etching of the films, the atomic concentration was measured as a function of etching depth. The binding energy spectra were analyzed using wavelet transform and curve fitting, showing that most of the oxygen impurity is in the form of boron oxides, and that the impurities are physically trapped among columnar structures in the film. In order to improve the base vacuum before coating the film, a range of methods were used, including argon gas filling on the target surface and titanium pre-sputtering. The experimental results show that the latter is an efficient and feasible method. Based on the titanium pre-sputtering technology, the optical performance of W/B₄C multilayer was improved so much.

Keywords: Boron carbide; Magnetron sputtering; Residual gas; XPS; Wavelet transform

Nanoindentation measurements on modified diamond-like carbon thin films by Neeraj Dwivedi; Sushil Kumar; Hitendra K. Malik (pp. 9953-9959).

• Stress reduction in DLC due to introduction of nitrogen, copper and titanium. • Improvement in hardness, elastic modulus and various other mechanical parameters due introduction of metallic (Cu and Ti) interfacial layers. • Increase in indentation load leads to degradation in mechanical properties.In the present study, we explored the effect of metallic interlayers (Cu and Ti) and indentation loads (5–20mN) on the mechanical properties of plasma produced diamond-like carbon (DLC) thin films. Also a comparison has been made for mechanical properties of these films with pure DLC and nitrogen incorporated DLC films. Introduction of N in DLC led to a drastic decrease in residual stress ( S) from 1.8 to 0.7GPa, but with expenses of hardness ( H) and other mechanical properties. In contrast, addition of Cu and Ti interlayers between substrate Si and DLC, results in significant decrease in S with little enhancement of hardness and other mechanical properties. Among various DLC films, maximum hardness 30.8GPa is observed in Ti-DLC film. Besides hardness and elastic modulus, various other mechanical parameters have also been estimated using load versus displacement curves.

Keywords: Diamond-like carbon (DLC); PECVD; Stress; Indentation

A two-step nanosecond laser surface texturing process with smooth surface finish by Yibo Gao; Benxin Wu; Yun Zhou; Sha Tao (pp. 9960-9967).

• Current nanosecond laser surface texturing produces dimples with rough bottoms. • A two-step nanosecond laser texturing process is proposed and studied. • The process can produce dimples with smooth bottom. • Dimple bottom roughness depends on laser pulse duration and scan speed. • 200ns pulses produce the lowest roughness.Surface texturing (for example, producing micro dimples on the surface) of mechanical parts has a great potential to improve the surface tribological properties. Surface texturing through nanosecond laser ablation has many associated advantages and hence has drawn lots of attentions. However, the produced micro dimple bottom (if through laser spot scanning) is often very rough, which may harm the surface tribological properties. In this paper, a two-step laser surface texturing process is proposed and studied, where a relatively high-fluence laser ablation step (which is to create dimples) is followed by a low-fluence laser-induced melting, melted material flow and re-solidification step (which is to smooth the ablated dimple bottom surface). The study shows that the two-step laser surface texturing process can produce dimples with very smooth bottom surfaces. The effects of laser pulse duration and scan speed in Step 2 on the dimple bottom surface morphology and roughness have also been investigated, and some very interesting physical phenomena have been found, which have been rarely reported before in literature. Some hypothesized explanations are given for the observed effects, which require future work to completely understand their underlying mechanisms.

Keywords: Keyword; Laser surface texturing

Laser microstructuring and annealing processes for lithium manganese oxide cathodes by J. Pröll; R. Kohler; M. Torge; S. Ulrich; C. Ziebert; M. Bruns; H.J. Seifert; W. Pfleging (pp. 9968-9976).

• Formation of microstructures in Li–Mn–O thin films with high aspect ratio. • Laser-annealing for setting up a spinel-like battery phase. • Micro-structures significantly improve battery performance. • Evidence for solid electrolyte interphase on cycled cathodes.It is expected that cathodes for lithium-ion batteries (LIB) composed out of nano-composite materials lead to an increase in power density of the LIB due to large electrochemically active surface areas but cathodes made of lithium manganese oxides (Li–Mn–O) suffer from structural instabilities due to their sensitivity to the average manganese oxidation state. Therefore, thin films in the Li–Mn–O system were synthesized by non-reactive radiofrequency magnetron sputtering of a spinel lithium manganese oxide target. For the enhancement of the power density and cycle stability, large area direct laser patterning using UV-laser radiation with a wavelength of 248nm was performed. Subsequent laser annealing processes were investigated in a second step in order to set up a spinel-like phase using 940nm laser radiation at a temperature of 680°C. The interaction processes between UV-laser radiation and the material was investigated using laser ablation inductively coupled plasma mass spectroscopy. The changes in phase, structure and grain shape of the thin films due to the annealing process were recorded using Raman spectroscopy, X-ray diffraction and scanning electron microscopy. The structured cathodes were cycled using standard electrolyte and a metallic lithium anode. Different surface structures were investigated and a significant increase in cycling stability was found. Surface chemistry of an as-deposited as well as an electrochemically cycled thin film was investigated via X-ray photoelectron spectroscopy.

Keywords: Laser structuring; Laser annealing; Surface modification; Lithium-ion battery; Lithium manganese oxide; Solid electrolyte interphase

Damage performance of TiO₂/SiO₂ thin film components induced by a long-pulsed laser by Bin Wang; Gang Dai; Hongchao Zhang; Xiaowu Ni; Zhonghua Shen; Jian Lu (pp. 9977-9981).

• Damage performances of TiO₂/SiO₂ films by a long-pulse laser are investigated. • Long-pulse lasers not only damage film coatings but also destroy the substrates. • Damage threshold decreases with laser spot size and finally keeps constant. • Damage size increases with laser fluence and finally keeps constant. • Damage efficiency increases with laser fluence at first and finally decreases.In order to study the long-pulsed laser induced damage performance of optical thin films, damage experiments of TiO₂/SiO₂ films irradiated by a laser with 1ms pulse duration and 1064nm wavelength are performed. In the experiments, the damage threshold of the thin films is measured. The damages are observed to occur in isolated spots, which enlighten the inducement of the defects and impurities originated in the films. The threshold goes down when the laser spot size decreases. But there exists a minimum threshold, which cannot be further reduced by decreasing the laser spot size. Optical microscopy reveals a cone-shaped cavity in the film substrate. Changes of the damaged sizes in film components with laser fluence are also investigated. The results show that the damage efficiency increases with the laser fluence before the shielding effects start to act.

Keywords: Long-pulsed laser; Laser-induced damage; Optical thin film

Tribological properties of heat-treated electroless Ni–P coatings on AZ91 alloy by M. Novák; D. Vojtěch; P. Novák; T. Vítů (pp. 9982-9985).

► Electroless Ni–P coating on AZ91 alloy shows good adhesion. ► No observable influence of heat treatment regime on coating wear rate. ► Good sliding properties due to the oxide glazes formation.Influence of heat treatment regime on adhesion and wear resistance of Ni–P electroless coating on AZ91 magnesium alloy is investigated in this work. The pretreated substrate was plated using a bath containing nickel sulphate, sodium hypophosphite and sodium acetate as main constituents. The coated samples were heat treated at 400–450°C for 1–8h. Adhesion of coating was estimated from the scratch test with an initial load of 8.80N. Wear resistance was studied using the pin-on-disc method. It was found that there is no significant dependence of the coating wear resistance on heat treatment regime, as the formation of Al–Ni intermetallic sub-layers that reduce coating adhesion is limited to regions where Al₁₇Mg₁₂ phase is present in the substrate. Moreover, the coating shows good sliding properties due to the formation of oxide glazes in the wear track.

Keywords: AZ91 alloy; Electroless coating; Scratch testing; Wear resistance

Plasma-aided hydrogenation and Al-doping: Increasing the conductivity and optical transparency of ZnO transparent conducting oxide by T. Ong; L. Xu; T.A. van der Laan; S. Xu; K. Ostrikov (pp. 9986-9990).

▶ The application of a plasma allows growth at a low substrate temperature (400°C). ▶ The addition of hydrogen to the plasma strongly influences the properties of the ZnO films. ▶ The electronic, optical and structural properties of the film can be tuned by modifying the flow rate of hydrogen. ▶ The flow rate can be optimized and to achieve the best values of optical transmittance and resistivity. ▶ The adsorption edge is shifted to a shorter wavelength as the H₂ flow rate increases.Plasma-assisted magnetron sputtering with varying ambient conditions has been utilised to deposit Al-doped ZnO (AZO) transparent conductive thin films directly onto a glass substrate at a low substrate temperature of 400°C. The effects of hydrogen addition on electrical, optical and structural properties of the deposited AZO films have been investigated using X-ray diffractometry (XRD), scanning electron microscopy (SEM), Hall effect measurements and UV–vis optical transmission spectroscopy. The results indicate that hydrogen addition has a remarkable effect on the film transparency and conductivity with the greatest effects observed with a hydrogen flux of approximately 3sccm. It has been demonstrated that the conductivity and the average transmittance in the visible range can increase simultaneously contrary to the effects observed by other authors. In addition, hydrogen incorporation further leads to the absorption edge shifting to a shorter wavelength due to the Burstein–Moss effect. These results are of particular relevance to the development of the next generation of optoelectronic and photovoltaic devices based on highly transparent conducting oxides with controllable electronic and optical properties.

Keywords: Plasma nanoscience; Oxide materials; Magnetron

Growth dynamics and thermal stability of Ni nanocrystalline nanowires by Z.F. Zhou; Y. Pan; Y.C. Zhou; L. Yang (pp. 9991-9995).

► The thermal instability of the Ni nanocrystalline nanowire (NNW) is dominated by the microstructure movement and the grain boundary rotation mechanism at temperature ranging from 400 to 600°C. ► The Ni-NNW experiences the Rayleigh instability at temperature approaching the melting point. ► The observed fragment separation in the Rayleigh phase-transition is much greater than that expected theoretically.The growth dynamics and the thermal stability of a Ni nanocrystalline nanowire (NNW) model system fabricated using electrochemical deposition has been investigated using X-ray diffraction, scanning and transition electron microcopy, and differential scanning calorimetry (DSC). It has been found that the thermal stability of the Ni-NNW is dominated by the microstructure movement and the grain boundary rotation mechanism at temperature ranging from 400 to 600°C. The Ni-NNW experiences the Rayleigh instability at temperature approaching the melting point. The observed fragment separation in the Rayleigh phase-transition is much greater than that expected theoretically.

Keywords: Nanocrystalline materials; Grain boundaries; Thermal properties; Rayleigh instability

Influence of annealing temperature on morphological and magnetic properties of La_0.9Sr_0.1MnO₃ by K.P. Shinde; S.S. Pawar; S.H. Pawar (pp. 9996-9999).

► Successful synthesis of phase pure nanocrystalline La_0.9Sr_0.1MnO₃. ► Effect of annealing temperature ranging from 600°C to 1200°C with annealing time of 5h on magnetic and morphological properties are studied. ► It is observed that magnetic properties are strongly dependent on annealing parameters. ► The sample annealed at 1200°C shows maximum saturation magnetization and lower coercivity with 52.5emu/g and 10.7Oe respectively.The nanocrystalline samples of La_0.9Sr_0.1MnO₃ (LSMO) have been prepared by the combustion method. The thermo gravimetric analysis of precursor was carried out. The X-ray diffraction study confirms the rhombohedral crystal structure without any other impurity phases. The morphology and magnetic properties change with annealing temperature. The saturation magnetization increases linearly and coercivity of the nanoparticles varies significantly as annealing temperature increases. The maximum saturation magnetization and lower coercivity found for the sample heat treated at 1200°C are 52.5emu/g and 10.7Oe respectively.

Keywords: LSMO; Solution combustion; Morphological property; Magnetic property

Super-hydrophilic properties of TiO₂–DLC nanocomposite films fabricated by the simple electrochemical process by Shanhong Wan; Liping Wang; Qunji Xue (pp. 10000-10004).

► Anatase TiO₂ nanoparticles incorporated DLC films were prepared. ► TiO₂ incorporation effectively increased sp³-hybridized carbon concentration. ► Such film demonstrated the nanocrystalline/amorphous composite microstructure. ► TiO₂-DLC composite film exhibited excellent superhydrophilicity.Anatase TiO₂ nanoparticles incorporated DLC films were successfully deposited on single crystalline silicon substrates by the electrolysis of TiO₂–methanol solution under ambient atmospheric pressure and low temperature. Anatase TiO₂ nanoparticles were embedded into amorphous carbon matrix, forming the typical nanocrystalline/amorphous nanocomposite films, confirmed by transmission electron microscopy (TEM). TiO₂ incorporation effectively increased the sp³-hybridized carbon concentration in the composite film, and further regulated the microstructure and surface morphology. Furthermore, the static contact testing completely displayed, TiO₂ incorporation got the composite films super-hydrophilic, which fundamentally improved the wetting ability of DLC film.

Keywords: Diamond-like carbon; Anatase TiO; ₂; Hydrophilicity

Evolution of steel surface composition with heating in vacuum and in air by Colin S. Doyle; Christopher K. Seal; Bryony J. James (pp. 10005-10017).

• Surface composition of mild, 304, 316 steels heated to 600°C in air and vacuum. • Heating in vacuum led to altered surface composition and chemical state. • Heating in low partial pressure air showed less change in chemical state. • Heating to 600°C in vacuum produced reduced iron and chromium species.X-ray photoelectron spectroscopy (XPS) has been used to investigate the changes in surface composition of three steels as they have undergone heating. The steels were mild steel, and two austenitic stainless steels, commonly designated 304 and 316 stainless steels. XPS measurements were made on the untreated samples, and then following heating for 30min in vacuo and in a 1×10⁻⁶Torr partial pressure of air, at temperatures between 100°C and 600°C.Mild steel behaves differently to the two stainless steels under the heating conditions. In mild steel the iron content of the surface increased, with oxygen and carbon decreasing, as a function of increasing temperature. The chemical state of the iron also changed from oxide at low temperatures, to metallic at temperatures above 450°C.In both stainless steels the amount of iron present in the surface decreased with increasing temperature. The decrease in iron at the surface was accompanied by an increase in the amount of chromium at the steel surface. At temperatures above 450°C the iron in both 304 and 316 stainless steels showed significant contributions from metallic iron, whilst the chromium present was in an oxide state. In 316 stainless steel heated to 600°C there was some metallic chromium present in the surface layer.The surfaces heated in air showed the least variation in composition, with the major change being the loss of carbon from the surfaces following heating above 300°C. There was also a minor increase in the concentration of chromium present on both the stainless steels heated under these conditions. There was also little change in the oxidation state of the iron and chromium present on the surface of these steels. There was some evidence of the thickening of the surface oxides as seen by the loss of the lower binding energy signal in the iron or chromium core level scans.The surfaces heated in vacuum showed a similar trend in the concentration of carbon on the surfaces, however the overall concentration of oxygen decreased throughout the heating of these steels. There were also significant changes in the oxidation state of the iron and chromium on these surfaces with significant amounts or iron and chromium present in the metallic form following heating up to 600°C.It appears that the carbon contamination on the surfaces plays an important role in the fate of the surface oxide layer for all of the steels heated in a vacuum environment.

Keywords: Steel; Surface segregation; ESCA; XPS; Vacuum heating

Effects of Cr doping on physical properties of amorphous In–Ga–Zn–O films by Shiu-Jen Liu; Shih-Hao Su; Hau-Wei Fang; Jang-Hsing Hsieh; Jenh-Yih Juang (pp. 10018-10021).

▶ Cr-doped In–Ga–Zn–O films were fabricated on sapphire substrates by using pulsed laser deposition technique. ▶ The valence of Cr doped in In–Ga–Zn–O films is determined to be 3+ by XPS measurements. ▶ The electrical and magnetic properties of the films are found to be strongly affected by Cr doping. ▶ The optical properties are almost not affected by Cr doping. ▶ The Cr-doped In–Ga–Zn–O films exhibit room-temperature ferromagnetic characteristics.Amorphous thin films of InGaZnO₄ (a-IGZO) doped with Cr have been fabricated by using pulsed-laser deposition (PLD). The electrical, optical and magnetic properties of Cr-doped a-IGZO films grown at 25°C and 150°C were investigated. The conductivity, optical transmission and band gap of films are remarkably enhanced by increasing the growth temperature. Conductivity, carrier concentration and mobility decrease with increasing the Cr content. However, the optical transmission and band gap are not significantly affected by Cr doping. Moreover, all Cr-doped films exhibit room-temperature ferromagnetism.

Keywords: Amorphous transparent conducting oxide; Diluted magnetic semiconductor; Indium gallium zinc oxide films; Cr doping

Investigation of the influence factors of polyethylene molecule encapsulated into carbon nanotubes by molecular dynamics simulation by Qun Li; Guofang He; Rengao Zhao; Yanfei Li (pp. 10022-10030).

► Influence factors of polyethylene molecule encapsulated into carbon nanotubes. ► Interaction energy decreases with the increase of temperature or the SWNT radius. ► Chemical modification will influence the interaction energy greatly. ► Group electronegativity and van der Waals force decide the interaction energy.In this work, the influence factors, namely chirality, temperature, radius and surface chemical modification, of the interaction energy for polyethylene (PE) molecule encapsulated into single-walled carbon nanotubes (SWNTs) had been investigated by molecular mechanics (MM) and molecular dynamics (MD) simulation. The results showed that all these factors would influence the interaction energy between PE and SWNTs. The interaction energy between PE molecule and the armchair SWNTs is largest among eight kinds of chiral SWNTs. The interaction energy decreases with the increase of temperature or the SWNT radius. The methyl, phenyl, hydroxyl, carboxyl, –F, and amino groups, have been introduced onto the surface of the SWNTs by the simulation software and the influence of SWNT chemical modification has also been investigated. The interaction energy between PE and chemically modified SWNTs is larger than that between PE and pristine SWNTs, and increases with increasing the concentration of the modified groups monotonously. In addition, the group electronegativity and van der Waals force will affect the interaction energy between PE and chemically modified SWNTs greatly, which can be attributed to the electronic structures of the chemically modified groups. This study can provide some useful suggestions for the composite material design and drug transport.

Keywords: PACS; 81.05.TpCarbon nanotubes; Polyethylene; Molecular dynamics; Interaction energy

ALD of ZnO using diethylzinc as metal-precursor and oxygen as oxidizing agent by E. Janocha; C. Pettenkofer (pp. 10031-10035).

► The manuscript contains results showing the possibility to grow ZnO with O₂ precursor without necessity of plasma reactions. ► XPS and synchrotron data show the preparation of ALD films of ZnO from H₂O or O₂ and diethylzinc. ► Evidence of O₂⁻ interstitials (dumbbell)for O₂ preparation.We report on ZnO atomic layer deposition (ALD) with a precursor combination of diethylzinc as metal-precursor and pure oxygen (O₂) as oxidant as an alternative to H₂O as oxygen precursor. The temperature region of self-limiting ALD growth (ALD window) is determined and shows an increase in growth rate of about 60% compared to water as oxygen-precursor. Finally, in situ X-ray photoelectron spectroscopy (XPS) and synchrotron-radiation photoelectron spectroscopy (SR-PES) have been used to analyze the initial growth and film properties of ALD-ZnO deposited in monolayer steps using both precursor combinations.

Keywords: Atomic layer deposition; Zinc oxide; Oxygen; Diethylzinc; Photoelectron spectroscopy

Microstructures and optical properties of Cu-doped ZnO films prepared by radio frequency reactive magnetron sputtering by Ligang Ma; Shuyi Ma; Haixia Chen; Xiaoqian Ai; Xinli Huang (pp. 10036-10041).

• The effect of Cu doping, substrate temperatures and annealing temperatures on the crystallization behavior and optical properties of the films were studied. • ZnO films show a stronger preferred orientation toward the c-axis and uniform grain size after Cu doping. • The (002) orientation of ZnO:Cu film was improved by appropriate substrate temperature. • Intense blue–green luminescence is obtained from the sample deposited at higher substrate temperature. • The crystal quality ZnO:Cu film and the intensity of emission were markedly improved after annealing.Pure and Cu-doped ZnO (ZnO:Cu) thin films were deposited on glass substrates using radio frequency (RF) reactive magnetron sputtering. The effect of substrate temperature on the crystallization behavior and optical properties of the ZnO:Cu films have been studied. The crystal structures, surface morphology and optical properties of the films were systematically investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and a fluorescence spectrophotometer, respectively. The results indicated that ZnO films showed a stronger preferred orientation toward the c-axis and a more uniform grain size after Cu-doping. As for ZnO:Cu films, the full width at half maxima (FWHM) of (002) diffraction peaks decreased first and then increased, reaching a minimum of about 0.42° at 350°C and the compressive stress of ZnO:Cu decreased gradually with the increase of substrate temperature. The photoluminescence (PL) spectra measured at room temperature revealed two blue and two green emissions. Intense blue–green luminescence was obtained from the sample deposited at higher substrate temperature. Finally, we discussed the influence of annealing temperature on the structural and optical properties of ZnO:Cu films. The quality of ZnO:Cu film was markedly improved and the intensity of blue peak (∼485nm) and green peak (∼527nm) increased noticeably after annealing. The origin of these emissions was discussed.

Keywords: PACS; 78.20.−e; 78.55.Et; 78.66.Hf; 68.55.JkCu-doped ZnO thin films; RF magnetron sputtering; Microstructure; X-ray diffraction; Optical properties

Indium tin oxide sol–gel precursor conversion process using the third harmonics of Nd:YAG laser by Jian Z. Chen; Chang-Pin Huang; Wei-Hsuan Tseng; I-Chun Cheng; Chih-I Wu (pp. 10042-10044).

•Third harmonics of Nd:YAG laser ( λ=355nm) is used for precursor conversion. • XPS reveals extremely high tin concentration in the laser-cured ITO thin films. • These excess tin-ions contribute no free carriers but act as scattering centers. • The excess tin-ions cause inferior electrical properties.We use the third harmonics of Nd:YAG laser ( λ=355nm) for simultaneous precursor conversion and dopant activation on sol–gel ITO thin films at a laser fluence range of 700–1000mJ/cm². A minimum resistivity of 5.37×10⁻²Ω-cm with a corresponding carrier concentration of 6×10¹⁹cm⁻³ is achieved at laser irradiation fluence of 900mJ/cm². X-ray photoelectron analysis reveals that extremely high tin concentration of 19.4at.% and above is presented in the laser-cured ITO thin films compared with 8.7at.% in the 500°C thermally cured counterpart. These excess tin-ions form complex defects, which contribute no free carriers but act as scattering centers, causing inferior electrical properties of the laser-cured films in comparison with the thermally cured ones.

Keywords: Sol–gel; Laser curing; Indium tin oxide

Structural characterization of supported nanocrystalline ZnO thin films prepared by dip-coating by J.R. Casanova; E.A. Heredia; C.D. Bojorge; H.R. Cánepa; G. Kellermann; A.F. Craievich (pp. 10045-10051).

► Different thermal treatments were studied onto ZnO thin films obtained by sol–gel. ► A most efficient compaction occurs at the highest annealing temperature. ► Roughness and thickness of thin films were compared by different techniques. ► Internal nanoporous structure of ZnO thin films was characterized by GISAXS. ► General results kept consistency for each sample as well as for total set. ►Nanocrystalline ZnO thin films prepared by the sol–gel dip-coating technique were characterized by grazing incidence X-ray diffraction (GIXD), atomic force microscopy (AFM), X-ray reflectivity (XR) and grazing incidence small-angle X-ray scattering (GISAXS). The structures of several thin films subjected to (i) isochronous annealing at 350, 450 and 550°C, and (ii) isothermal annealing at 450°C during different time periods, were characterized. The studied thin films are composed of ZnO nanocrystals as revealed by analysing several GIXD patterns, from which their average sizes were determined. Thin film thickness and roughness were determined from quantitative analyses of AFM images and XR patterns. The analysis of XR patterns also yielded the average density of the studied films. Our GISAXS study indicates that the studied ZnO thin films contain nanopores with an ellipsoidal shape, and flattened along the direction normal to the substrate surface. The thin film annealed at the highest temperature, T=550°C, exhibits higher density and lower thickness and nanoporosity volume fraction, than those annealed at 350 and 450°C. These results indicate that thermal annealing at the highest temperature (550°C) induces a noticeable compaction effect on the structure of the studied thin films.

Keywords: ZnO; Nanostructured thin films; XR; GISAXS

The influence of Ga source and substrate position on the growth of low dimensional GaN wires by chemical vapour deposition by L.L. Low; F.K. Yam; K.P. Beh; Z. Hassan (pp. 10052-10055).

► Synthesis of GaN low dimensional materials (micro- and nanowires) via Ni catalyzed chemical vapour deposition under different conditions. ► To investigate the influence of Ga source and substrate position on the physical properties of GaN. ► Based on the morphological characteristics of the samples obtained from the FE-SEM images, growth mechanisms are proposed.This paper presents the investigation of low dimensional GaN structures synthesized from Ni-catalyzed chemical vapour deposition (CVD) method under two different conditions, i.e. Ga source and substrate position. Comparative studies based on the morphological, structural and optical characteristics of synthesized GaN wires were carried out in this work. The variations of morphological and dimensional aspects of the GaN wires were attributed to the position of Ga precursor and substrates. These factors were found to be able to influence the degree of supersaturation of gaseous reactants, which is essential in the growth of GaN wires by vapour–liquid–solid (VLS) mechanism. The synthesized GaN wires typically were found to have diameters ranging 35–80nm (nanowires) and 0.4–1.3μm (microwires), respectively, with length up to several ten of microns. X-ray diffraction (XRD) results indicated that the grown GaN wires were hexagonal wurzite phase. Ultraviolet (UV) and blue emissions were observed from photoluminescence (PL) measurements. Raman spectra displayed asymmetrical and broadened bands which could be ascribed to the size effect, surface disorder and internal strain of the synthesized GaN wires.

Keywords: GaN; Nanowires; Chemical vapour deposition; Vapour–liquid–solid mechanism

Chemical, electrical and electrochemical characterization of hybrid organic/inorganic polypyrrole/PW₁₂O₄₀³⁻ coating deposited on polyester fabrics by J. Molina; J. Fernández; A.I. del Río; J. Bonastre; F. Cases (pp. 10056-10064).

► Fabrics of polyester have been coated with conducting polypyrrole (PPy)/PW₁₂O₄₀³⁻ hybrid material. ► Conductive fabrics of PES-PPy/PW₁₂O₄₀³⁻ are stable in acid media and neutral media. ► In basic media, PW₁₂O₄₀³⁻ decomposes and there is a decrease of the conducting properties. ► SECM measurements showed that the coatings of PPy/PW₁₂O₄₀³⁻ were electroactive.A study of the stability of conducting fabrics of polyester (PES) coated with polypyrrole/PW₁₂O₄₀³⁻ (organic/inorganic hybrid material) in different pH solutions (1, 7, 13) has been done. Washing tests were also done in views of its possible application in electronic textiles such as antistatic clothing. X-ray photoelectron spectroscopy (XPS) studies have been done to quantify the amount of counter ion that remains in the polymer matrix and determine the doping ratio (N⁺/N) after the different tests. Scanning electron microscopy (SEM) was also used to observe morphological differences after the different tests. Surface resistivity changes were measured by means of electrochemical impedance spectroscopy (EIS). Scanning electrochemical microscopy (SECM) was employed to measure changes in electroactivity after the different tests. Higher pHs caused a decrease of the doping ratio (N⁺/N), the loss of part of the counter ions and the decrease of its conducting and electrocatalytic properties. The stability in acid media and neutral media and after the washing test was good. Only at pH 13 the loss of the counter ion was widespread and there was a decrease of its conducting and catalytic properties; although the fabrics continued acting mainly as a conducting material.

Keywords: Polypyrrole; Conducting fabric; Phosphotungstate; X-ray photoelectron spectroscopy; Scanning electrochemical microscopy

Silicon oxynitride thin films synthesised by the reactive gas pulsing process using rectangular pulses by E. Aubry; S. Weber; A. Billard; N. Martin (pp. 10065-10071).

► SiON films were synthesised by RGPP using oxygen rectangular pulses. ► O₂ introduction results in Si target potential decay due to its favoured adsorption. ► O/N ratio depends on frequency of sputtering mode alternation. ► Over a certain frequency, oxidised steady-state prevails resulting in SiO₂ formation.Silicon oxynitride thin films were synthesised by the reactive gas pulsing process using an argon, oxygen and nitrogen gas mixture from a semiconductor Si target. Argon and nitrogen were introduced at a constant mass flow rate, whereas oxygen gas was periodically supplied using a rectangular pulsed flow rate. The O₂ injection time T_ON (or duty cycle α) was the only varied parameter. The influences of this parameter on the discharge behaviour, on the Si target voltage, and on the resulting chemical composition of the films were investigated. The temporal evolution of the total pressure exhibits exponential shape differing from the rectangular oxygen pulse shape, due to the response time of the gas flowmeter and to the progressive oxidation of the target and the chamber walls. During the T_ON time, the preferential adsorption of the introduced O₂ induces a decay in Si target voltage. Reversion to the nitrided mode is still possible as soon as the O₂ injection is stopped. The elemental analyses assessed by secondary neutral mass spectrometry (SNMS) showed that the O/N ratio within silicon oxynitride films linearly depends on the T_ON time. Increasing the duty cycle α over a certain value results in an oxidised steady state formation during the T_ON time. This formation was observed by real time measurements of the emission lines ratio I(O^*)/ I(Ar^*) indicative of the O₂ partial pressure and confirmed by the time derivative of the target voltage. During the T_OFF time, the alternation with the nitrided mode becomes impossible, leading to the specific synthesis of stoichiometric SiO₂ films.

Keywords: SiO; _x; N; _y; Reactive sputtering; Optical emission spectroscopy; Reactive gas pulsing process

Investigations on structural, vibrational, morphological and optical properties of CdS and CdS/Co films by ultrasonic spray pyrolysis by S. Aksay; M. Polat; T. Özer; S. Köse; G. Gürbüz (pp. 10072-10077).

The CdS film has an average transmittance of 77%, whereas the CdS/Co films show an average transmittance above 64%. As the Co content increases beyond this, the average transmittance decreases. Four characteristic optical absorption bands in the visible range labelled as 1, 2, 3 and 4 can also be observed. These four absorption edges correspond to 680nm (1.82eV), 690 (1.79eV), 720nm (1.72eV) and 740nm (1.67eV), respectively.Display Omitted► We have studied the structural (XRD), optical (UV–vis), morphological (AFM), elemental (EDS) and vibrational (FT-IR and Raman) properties of CdS and CdS/Co films deposited by ultrasonic spray pyrolysis method. ► X-ray diffraction analysis showed that the preferential orientation of the films shifts from H(002) to H(110) with Co content. ► Raman and FT-IR spectra show the change in the peak intensity with increasing Co concentration.CdS and CdS/Co films have been deposited on glass substrates by an ultrasonic spray pyrolysis method. The effects of Co incorporation on the structural, optical, morphological, elemental and vibrational properties of these films were investigated. XRD analysis confirmed the hexagonal wurtzite structure of all films and had no impurity phase. While CdS film has (002) as the preferred orientation, CdS/Co films have (110) as the preferred orientation. The direct optical band gap was found to decrease from 2.42 to 2.39eV by Co incorporation. The decrease of the direct energy gaps by increasing Co contents is mainly due to the sp–d exchange interaction between the localized d-electrons of Co²⁺ ions and band electrons of CdS. After the optical investigations, it was seen that the transmittance of CdS films decreased by Co content. The Raman measurements revealed two peaks corresponding to the 1LO and 2LO modes of hexagonal CdS. The vibrational modes of Cd–S were obtained in the wavenumber range (590–715cm⁻¹) using Fourier transform infrared spectroscopy (FTIR). The elemental analysis of the film was done by energy dispersive X-ray spectrometry.

Keywords: Cds/co films; X-ray diffraction; Optical materials; AFM; FTIR; Raman

The effect of heat treatment on the electrochemical corrosion behavior of reactive plasma-sprayed TiN coatings by Xuebo Zhao; Dianran Yan; Sha Li; Chenguang Lu (pp. 10078-10083).

► The thickness of reactive plasma-sprayed TiN coatings can be up to 300μm. ► Heat treatment enables the increase of corrosion resistance of TiN coatings. ► The corrosion process of the heat treated TiN coating was studied with aid of electrochemical impedance spectroscopy (EIS). ► TiO₂ and Ti₃O from the oxidizing reaction of TiN and O₂ reduces the porosity.The effect of heat treatment on the corrosion behavior of reactive plasma sprayed TiN coatings in simulated seawater was investigated by electrochemical methods such as the corrosion potential–time curve ( E_corr− t), potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and SEM, etc. The results showed that the corrosion potential of TiN coatings increased after heat treatment; the corrosion current of the TiN coatings after heat treatment (be hereafter referred to as HT-TiN) was 13.3% of the untreated coatings (be hereafter referred to as UT-TiN), and the polarization resistance of HT-TiN was 20 times of UT-TiN, which indicated that the heat treatment had significantly increased the corrosion resistance of the coatings. The corrosion behavior of the coatings was mainly local corrosion, and the local corrosion behavior mainly took place at the microdefects (crack and pores) of the coatings. The porosity of the coatings was reduced after heat treatment. The reason was that TiN reacted with O₂ to form TiO₂ and Ti₃O during the heat treating, and volume expansion took place, which led to denser microstructure. The corrosion resistance of the coatings was therefore increased.

Keywords: Electrochemical corrosion; Reactive plasma spraying; TiN coating; Heat treatment

Facile synthesis of Nb₂O₅ nanorod array films and their electrochemical properties by Hao Wen; Zhifu Liu; Jiao Wang; Qunbao Yang; Yongxiang Li; Jerry Yu (pp. 10084-10088).

► Uniform Nb₂O₅ nanorod array films were synthesized by a facile hydrothermal process using the non-corrosive NH₄F as the reactant. ► These Nb₂O₅ nanorods grew along 〈001〉 direction and have good thermal stability both in morphology and in crystal structure. ► The Nb₂O₅ nanorod film showed a specific charge capacity of up to 380mAhg⁻¹ even after 50 charge/discharge process, indicating the potential energy storage application of this kind of nanostructure.Nb₂O₅ nanorod array films were synthesized by a facile hydrothermal process using niobium metal foil and NH₄F as precursors. The Nb₂O₅ nanorods stand on the niobium metal foil substrate and are less than 100nm in diameter and about 1μm in length. X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) characterizations indicate that these nanorods have orthorhombic structure and grew longitudinally along 〈001〉 direction. The nanorod growth mechanism was discussed. Thermal annealing at a temperature below 500°C did not change the microstructure of nanorods but improve the crystallinity. The Nb₂O₅ nanorod array films have been tested as cathode material for lithium battery, which showed a good specific capacity up to 380mAhg⁻¹ even after 50 charge/discharge cycles.

Keywords: Nb; ₂; O; ₅; Nanorod; Hydrothermal synthesis; Electrochemical property

Surface characterization of copper, zinc and brass in contact with tap water inhibited with phosphate ions by L. Yohai; W.H. Schreiner; M. Vázquez; M.B. Valcarce (pp. 10089-10095).

► The surface on Cu, Zn and brass in contact with artificial tap water is investigated. ► Changes in composition after adding phosphate to tap water were analyzed. ► Cyclic voltammograms, reflectance spectra, XRD, Raman spectra and XPS were recorded. ► PO₄³⁻ leads to a passive film rich in CuO on Cu, and rich in Zn₃(PO₄)₂ on brass. ► A mechanism is proposed to explain the effect of the inhibitor.The composition of the surface layers has been investigated on copper, zinc and brass in contact with moderately hard, highly carbonated and chloride rich artificial tap water (ATW). Cyclic voltammetry, reflectance spectroscopy, X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy have been used to identify the changes in composition that result from the incorporation of sodium orthophosphate to ATW. The results showed that when PO₄³⁻ is added, the film changes its composition and it also becomes thinner, denser and more compact. On copper, the presence of CuO in the passive film can be correlated to the improvement in the corrosion behavior in the presence of phosphate ions. In the case of brass, the development of a thinner, compact and less porous Zn₃(PO₄)₂ layer hinders Cu(I) dissolution. A mechanism explaining the effect of this inhibitor is proposed, which accounts for the experimental results.

Keywords: Passive film; Copper; Zinc; Brass; Tap water

Light-induced antifungal activity of TiO₂ nanoparticles/ZnO nanowires by N. Haghighi; Y. Abdi; F. Haghighi (pp. 10096-10100).

► ZnO/TiO₂ nanostructure can be used as antifungal material. ► TiO₂ nanoparticles significantly improve the antifungal activity of the ZnO nanowires. ► The viability of the fungi is suppressed considerably around the ZnO/TiO₂ nanostructure.Antifungal activity of TiO₂/ZnO nanostructures under visible light irradiation was investigated. A simple chemical method was used to synthesize ZnO nanowires. Zinc acetate dihydrate, Polyvinyl Pyrrolidone and deionized water were used as precursor, capping and solvent, respectively. TiO₂ nanoparticles were deposited on ZnO nanowires using an atmospheric pressure chemical vapor deposition system. X-ray diffraction pattern of TiO₂/ZnO nano-composite has represented the diffraction peaks relating to the crystal planes of the TiO₂ (anatase and rutile) and ZnO. TiO₂/ZnO nanostructure antifungal effect on Candida albicans biofilms was studied and compared with the activity of TiO₂ nanoparticles and ZnO nanowires. The high efficiency photocatalytic activity of TiO₂ nanoparticles leads to increased antifungal activity of ZnO nanowires. Scanning electron microscope was utilized to study the morphology of the as prepared nanostructures and the degradation of the yeast.

Keywords: TiO; ₂; nanoparticles; ZnO nanowires; Composite; Antifungal

Influence of zirconium doping on the activities of zirconium and iodine co-doped titanium dioxide in the decolorization of methyl orange under visible light irradiation by Shuang Song; Fangyue Hong; Zhiqiao He; Hongyu Wang; Xianghong Xu; Jianmeng Chen (pp. 10101-10108).

► Zr doping can effectively improve the phtocatalytic activity of I-doped TiO₂. ► Catalysts for visible light photocatalysis. ► Zr–I–TiO₂ (molar ratio 5:20:100) calcined at 400°C is the optimal catalyst. ► High specific surface area is beneficial to the photocatalytic reaction. ► Zr doping suppresses insignificantly the recombination of photogenerated charges.Zirconium and iodine co-doped titanium dioxide (Zr–I–TiO₂) was prepared by the hydrolysis of tetrabutyl titanate, premixed with zirconium nitrate in an iodic acid aqueous solution, followed by calcination in air. The structure and properties of the resultant catalyst powders were characterized by X-ray diffraction, the Brunauer–Emmett–Teller method, X-ray photoelectron spectroscopy, transmission electron microscopy, and UV–vis absorption spectroscopy. The catalytic activity of the catalyst was evaluated by monitoring the photocatalytic decolorization of methyl orange under visible light irradiation. The results showed that the activities of Zr–I–TiO₂ catalysts were higher than that of TiO₂ doped with iodine alone (I–TiO₂), and the optimal doping concentration in the Zr–I–TiO₂ calcined at 400°C was determined to be about 0.05 (molar ratio of Zr:Ti). In addition, the photocatalytic activity of Zr–I–TiO₂ calcined at 400°C was found to be significantly higher than that calcined at 500 or 600°C. Based on the physico-chemical characterization, we concluded that the role of zirconium on the I–TiO₂ surface is to increase the number of reactive sites by generating a small crystal size and large surface area. The inhibition of electron–hole pair recombination, by trapping photo-generated electrons with Zr⁴⁺, did not contribute markedly to the improved photocatalytic activity of Zr–I–TiO₂.

Keywords: Zirconium; Iodine; Titanium dioxide; Methyl orange; Visible light induced photocatalysis

Biomineralization of electrospun poly(l-lactic acid)/gelatin composite fibrous scaffold by using a supersaturated simulated body fluid with continuous CO₂ bubbling by Qing Cai; Qingqing Xu; Qiaofang Feng; Xiaoyan Cao; Xiaoping Yang; Xuliang Deng (pp. 10109-10118).

In classical five times simulated body fluid (5×SBF), homogeneous nucleation of Ca–P mineralites and deposition unavoidably took place owing to the HCO₃⁻ decomposition and the pH value increment, which made the prediction of bone bioactivity of substrates controversial. In this study, the classically prepared 5×SBF was continuously bubbled with CO₂ to keep the pH value stable at 6.4. The biomineralization results of a kind of coelectrospun poly(l-lactic acid)/gelatin composite fibers in the modified 5×SBF demonstrated that heterogenenous nucleation occurred dominantly. Thermodynamical unstable brushites (dicalcium phosphate dihydrate, DCPD) were detected shortly on the composite fibers. The sheet-like DCPD mineralites transformed into flaky carbonated calcium-deficient hydroxyapatite (CDHA) within 24h on the PLLA/gelatin composite fibers due to the accelerating effect of gelatin component. And the formed apatite coating contained much less Mg²⁺ ions than that deposited in the classical 5×SBF. These findings suggested that supersaturated SBFs buffered with CO₂ could be expected as a good choice for the prediction of the bone bonding bioactivity of substrates.Display Omitted► Electrospun poly(l-lactide)/gelatin composite fibers as substrates for biomineralization. ► Five times simulated body fluid bubbled with gassy CO₂ is used for biomineralization. ► Gelatin component in composite fibers enhances apatite formation and transformation.To promote the biomineralization, supersaturated simulated body fluids (SBFs), e.g. five times SBF (5×SBF), were usually applied. In these SBFs, however, homogeneous nucleation of Ca–P mineralites and deposition unavoidably took place owing to the HCO₃⁻ decomposition and the pH value increment, which made the prediction of bone bioactivity of substrates controversial. In this study, the classically prepared 5×SBF was continuously bubbled with CO₂ to keep the pH value stable at 6.4 and the solution transparent, and a kind of electrospun poly(l-lactic acid)/gelatin composite fibers was used for the biomineralization study. In such a modified 5×SBF, heterogenenous nucleation occurred dominantly and thermodynamical unstable brushites (dicalcium phosphate dihydrate, DCPD) were detected shortly on both electrospun PLLA fibers and PLLA/gelatin (1:1 in weight) composite fibers. In comparison with electrospun PLLA fibers, the sheet-like DCPD mineralites transformed into flaky carbonated calcium-deficient hydroxyapatite (CDHA) within 24h on the PLLA/gelatin composite fibers due to the accelerating effect of gelatin component. The formed apatite coating contained much less Mg²⁺ ions than that deposited in the classical 5×SBF. The results of this study showed that supersaturated SBFs buffered with gassy CO₂ were expected good choices for the accelerated biomineralization, and for the prediction of the bone bonding bioactivity of substrates.

Keywords: Simulated body fluid; CO; ₂; bubbling; Gelatin; Poly (; l; -lactic acid); Electrospinning

Defects in the in situ synthesized TiB₂/Fe composite coatings during PTA process by Daoliang Wu; Xibao Wang; Panpan Zhang; Lijuan Cai; Hongling Sun (pp. 10119-10125).

► The macro and micro defects are sensitive to the surfacing process conditions. ► The coatings’ surface forming depends on both energy density and total energy input. ► Slag inclusions and cracks often appear together. ► The tendency of slag inclusions and cracks decreases as the dilution rate increases.The in situ synthesized TiB₂/Fe composite coatings were deposited by the plasma transferred-arc (PTA) powder surfacing process. The macro and micro defects in the TiB₂/Fe composite coatings were investigated in this paper. It is found that heat input plays an important role in macro defects in the coatings. Only when the energy density and total heat input are appropriate will nice forming with few macro defects be obtained. As micro defects in the coatings, slag inclusions (C, Al₂O₃) and cracks often appear together. And it is found that slag inclusions and cracks tend to appear with a low dilution rate of the coatings, and their tendency decreases as the dilution rate increases.

Keywords: Plasma transferred-arc; TiB; ₂; Defects; Surface forming; Slag inclusions; Cracks

Template-directed hydrothermal synthesis of hydroxyapatite as a drug delivery system for the poorly water-soluble drug carvedilol by Qinfu Zhao; Tianyi Wang; Jing Wang; Li Zheng; Tongying Jiang; Gang Cheng; Siling Wang (pp. 10126-10133).

Display Omitted► Mesoporous hydroxyapatite was synthesized using F127 and CTAB as templates. ► Carvedilol was selected as a model drug. ► Carvedilol in an amorphous state was incorporated in mesoporous hydroxyapatite. ► Hydroxyapatite had a high drug load efficiency and provided fast release of carvedilol. ► Hydroxyapatite is a good carrier for the oral delivery of poorly water-soluble drugs.In order to improve the dissolution rate and increase the bioavailability of a poorly water-soluble drug, intended to be administered orally, the biocompatible and bioactive mesoporous hydroxyapatite (HA) was successfully synthesized. In the present study, mesoporous HA nanoparticles were produced using Pluronic block co-polymer F127 and cetyltrimethylammonium bromide (CTAB) as templates by the hydrothermal method. The obtained mesoporous HA was employed as a drug delivery carrier to investigate the drug storage/release properties using carvedilol (CAR) as a model drug. Characterizations of the raw CAR powder, mesoporous HA and CAR-loaded HA were carried out by the scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) spectroscopy, N₂ adsorption/desorption, thermogravimetric analysis (TGA), and UV–VIS spectrophotometry. The results demonstrated that CAR was successfully incorporated into the mesoporous HA host. In vitro drug release studies showed that mesoporous HA had a high drug load efficiency and provided immediate release of CAR compared with micronized raw drug in simulated gastric fluid (pH 1.2) and intestinal fluid (pH 6.8). Consequently, mesoporous HA is a good candidate as a drug carrier for the oral delivery of poorly water-soluble drugs.

Keywords: Mesoporous hydroxyapatite; Drug delivery system; Carvedilol; Poorly water-soluble drugs; In vitro dissolution

Controllable hydrothermal synthesis of ZnO nanowires arrays on Al-doped ZnO seed layer and patterning of ZnO nanowires arrays via surface modification of substrate by Jin Zhang; Wenxiu Que; Qiaoying Jia; Xiangdong Ye; Yucheng Ding (pp. 10134-10140).

Display Omitted► ZnO nanowire (NW) arrays are controlled assembled on the Al-doped ZnO (AZO) seed layer by a hydrothermal process. ► A surface fluorination technique is applied to patterning AZO seed layer. ► The patterned ZnO NW arrays with few crystal defects are successfully fabricated on the silicon substrate.ZnO nanowire (NW) arrays are assembled on the Al-doped ZnO (AZO) seed layer by a hydrothermal process. Effects of the temperature and growth time of the hydrothermal process on morphological and photoluminescence properties of the as-assembled ZnO NW arrays are characterized and studied. Results indicate that the length and diameter of the ZnO NWs increase with a lengthening of the growth time at 80°C and the hydrothermal temperature has a significant effect on the growth rate and the photoluminescence properties of the ZnO NW arrays. The patterned AZO seed layer is fabricated on a silicon substrate by combining a sol–gel process with an electron-beam lithography process, as well as a surface fluorination technique, and then the ZnO NW arrays are selectively grown on those patterned regions of the AZO seed layer by the hydrothermal process. Room-temperature photoluminescence spectra of the patterned ZnO NW arrays shows that only a strong UV emission at about 380nm is observed, which implies that few crystal defects exist inside the as-grown ZnO NW arrays.

Keywords: Zinc oxide; Nanowires; Seed layer; Fluorination; Photoluminescence

Hydrogen and oxygen plasma enhancement in the Cu electrodeposition and consolidation processes on BDD electrode applied to nitrate reduction by A.B. Couto; L.C.D. Santos; J.T. Matsushima; M.R. Baldan; N.G. Ferreira (pp. 10141-10146).

► Deposition and consolidation of Cu on BDD is affected by H or O-terminations. ► Hydrogen plasma treatment promoted a high Cu density and homogeneity on BDD. ► Oxygen plasma treatment is important factor for consolidation of Cu on BDD. ► The nitrate reduction is strongly influenced on the electrolyte pH.Copper nanoparticle electrodeposition and consolidation processes were studied on boron doped diamond (BDD) electrode submitted to hydrogen and oxygen plasma treatments. The modified BDD films were applied as electrodes for nitrate electroreduction. The results showed that both treatments have a strong influence on the copper deposition and dissolution processes. For BDD treated with hydrogen plasma the copper electrodeposit was homogeneous with high particle density. This behavior was attributed to the BDD surface hydrogenation that improved its conductivity. On the other hand, the treatment with oxygen plasma was important for the copper nanoparticle consolidation on BDD surface, confirmed by the result's reproducibility for nitrate reduction. This performance may be associated with the formation of oxygen groups that can act as anchor points for Cu-clusters, enhancing the interfacial adhesion between diamond and the metal coating. The best electrochemical nitrate reduction response was obtained in acid media, where occurred the separation of the nitrate reduction process and the water reduction reaction.

Keywords: BDD; Copper electrodeposition; Hydrogen and oxygen plasma treatment; Nitrate detection

Low voltage electron induced cathodoluminescence degradation and surface characterization of Sr₃(PO₄)₂:Tb phosphor by I.M. Nagpure; Shreyas S. Pitale; E. Coetsee; O.M. Ntwaeaborwa; J.J. Terblans; H.C. Swart (pp. 10147-10155).

Display Omitted► A simple and cost effective gel-combustion reaction was adopted to prepare terbium doped Sr₃(PO₄)₂ phosphor. ► Stable bluish-green cathodoluminescence was observed from Sr₃(PO₄)₂:Tb³⁺ phosphor. ► The long term columbic aging and luminescence output was monitored under a continuous 2keV accelerated electron flux. The in situ surface concentration changes were probed using Auger electron spectroscopy, reveals surface concentration modification of Sr, P and O atoms. ► Ex situ surface chemical analysis using X-ray photoelectron spectroscopy reveals the formation of a sub-stoichiometric SrO and P₂O₅ layer due to electron stimulated surface chemical reactions (ESSCRs) on the surface of the Sr₃(PO₄)₂:Tb phosphor. ► The relative contribution of the individual degraded and undegraded species is differerent for the two pressures and the presence of a small amount of metallic P on the surface might played an important role in the surface conductivity, this layer is possibly contributing to the surface chemical stability and prevents further degradation.Tb³⁺-doped Sr₃(PO₄)₂ phosphor was prepared by a sol–gel combustion method. A trigonal structure having Sr and O atoms occupying two different lattice sites were obtained. Scanning Auger nanoprobe was used to analyze the morphology of the particles. Photoluminescence (PL) and cathodoluminescence (CL) properties of Sr₃(PO₄)₂:Tb powder phosphors were evaluated and compared. In addition, the CL intensity degradation of Sr₃(PO₄)₂:Tb was evaluated when the powders were irradiated with a beam of electrons in a vacuum chamber maintained at an O₂ pressure of 1×10⁻⁶Torr or a background pressure of 1×10⁻⁸Torr O₂. The surface chemical composition of the degraded powders, analyzed by X-ray photoelectron spectroscopy (XPS), suggests that new compounds (metal oxides) of strontium and phosphorous were formed on the surface. It is most likely that these compounds contributed to the CL intensity degradation of the Sr₃(PO₄)₂:Tb phosphors. The CL properties and possible mechanism by which the new metal oxides were formed on the surface due to a prolonged electron beam irradiation are discussed.

Keywords: AES; NanoSAM; Photoluminescence; Cathodoluminescence; XPS; ESSCR; Electron degradation; Sr; ₃; (PO; ₄; ); ₂

Influence of annealing process on conductive properties of Nb-doped TiO₂ polycrystalline films prepared by sol–gel method by Jinming Liu; Xiaoru Zhao; Libing Duan; Mengmeng Cao; Huinan Sun; Jifeng Shao; Shuai Chen; Haiyan Xie; Xiao Chang; Changle Chen (pp. 10156-10160).

► We investigated conductive properties of anatase TNO films prepared sol–gel method. ► We reported the effect of post-annealing on conductivity of TNO films. ► The multi-round annealing was effective to improve conductivity of TNO film.Nb-doped TiO₂ (TNO) thin films were prepared by sol–gel dip-coating method with Nb content in a wide range of 0–20at.%. The prepared films were preheated at 400°C and then undertaken by two different post-annealing processes: (a) three times vacuum annealing and (b) multi-round annealing. The designed multi-round annealing was shown to be an effective way to improve the conductive properties of the films, compared to the traditional vacuum annealing process. The minimum resistivity reached approximately 0.5Ωcm with Nb doping concentration around 12at.%, and the carrier density increased with Nb-doping concentration until the critical point of 12at.%, which might be the optimal doping content for our TNO films prepared by sol–gel method.

Keywords: Sol–gel; Transparent conductive film; Nb-doped TiO; ₂; Annealing

Ceria nanospindles: Template-free solvothermal synthesis and shape-dependent catalytic activity by Dengsong Zhang; Fuhuan Niu; Tingting Yan; Liyi Shi; Xianjun Du; Jianhui Fang (pp. 10161-10167).

► The ceria nanospindles have been successfully synthesized via a simple template-free solvothermal treatment. ► The reaction solvents, reaction temperature and time are the crucial factors determining the formation of ceria nanospindles. ► The other ceria micro/nanostructures such as columns, spheres, and rods were obtained by adjusting the experimental parameters. ► The platinum coated ceria nanospindles show the excellent low-temperature catalytic activity in the CO oxidation. ►The ceria nanospindles have been successfully synthesized via a simple template-free solvothermal treatment by employing a mixture of glycerin and water as the reaction solvent. The properties of the ceria nanospindles were characterized. A series of control experiments confirms that the reaction solvents, reaction temperature and time are the crucial factors determining the formation of ceria nanospindles, and by adjusting the experimental parameters the other ceria micro/nanostructures such as columns, spheres, and rods were obtained. The platinum coated ceria nanospindles show the excellent low-temperature catalytic activity in the oxidation of carbon monoxide as compared with other micro/nanostructures, which is mainly due to their special shape and uniformly-distributed active sites.

Keywords: Ceria; Nanostructures; CO oxidation; Catalysts

Growth of β-FeSi₂ thin film on textured silicon substrate for solar cell application by Jiaxiong Xu; Ruohe Yao; Yurong Liu (pp. 10168-10171).

► The inverted pyramid array textured Si substrate was used as an antireflection technology for β-FeSi₂ solar cell application. β-FeSi₂ thin film was deposited on the textured Si substrate by magnetron sputtering. ► The β-FeSi₂ thin film remained as the inverted pyramid array and the average reflectance reduced to 4.33% in the wavelength range from 200nm to 1500nm. ► The prototype β-FeSi₂/textured-Si heterojunction showed a rectifying ratio of 2.89×10⁵ and a built-in voltage of 0.58V.(202)/(220)-oriented epitaxial β-FeSi₂ thin films were deposited on textured Si (100) substrate by magnetron sputtering. The influences of thickness and annealing temperature on the β-FeSi₂ crystallization were studied to find the optimal condition. The results of surface morphology and optical property measurements showed that the inverted pyramid array in the surface of β-FeSi₂ thin films could reduce the surface reflection of β-FeSi₂. In dark condition, the β-FeSi₂/textured-Si heterojunction showed diode property with rectifying ratio of 2.89×10⁵ and built-in potential of 0.58V. These results indicated the potential application of textured Si substrate in β-FeSi₂ solar cells.

Keywords: β-FeSi; ₂; Textured silicon; Magnetron sputtering; Heterojunction

Cleaning of SiC surfaces by low temperature ECR microwave hydrogen plasma by Lingqin Huang; Qiaozhi Zhu; Mingchao Gao; Fuwen Qin; Dejun Wang (pp. 10172-10176).

► SiC wafers were exposed to low temperature ECR microwave hydrogen plasma. ► The RHEED patterns show that well cleaned, atomically ordered, unreconstructed 4H–SiC surfaces are achieved. ► The Si2p and O1s spectra indicate that the surface oxygen is greatly reduced and the surfaces exhibit stability against oxidation in air. ► The removal of carbon contamination from the SiC surfaces is confirmed by C1s spectrum. ► The hydrogenated SiC surfaces are chemically and electrically well passivated with the density of surfaces states as low as 8.09×10¹⁰cm⁻²eV⁻¹.N-type 4H–SiC (0001) surfaces were cleaned by low temperature hydrogen plasma in electronic cyclotron resonance (ECR) microware plasma system. The effects of the hydrogen plasma treatment (HPT) on the structure, chemical and electronic properties of surfaces were characterized by in situ reflection high energy electron diffraction (RHEED) and X-ray photoelectron spectroscopy (XPS). The RHEED results indicate that the structures of the films are strongly dependent on the treatment temperature and time. Significant improvements in quality of 4H–SiC films can be obtained with the temperature ranging from 200°C to 700°C for an appropriate treatment period. The XPS results show that the surface oxygen is greatly reduced and the carbon contamination is completely removed from the 4H–SiC surfaces. The hydrogenated SiC surfaces exhibit an unprecedented stability against oxidation in the air. The surface Fermi level moves toward the conduction band in 4H–SiC after the treatment indicating an unpinning Fermi level with the density of surfaces states as low as 8.09×10¹⁰cm⁻²eV⁻¹.

Keywords: 4H–SiC; Surface cleaning; Electronic cyclotron resonance hydrogen plasma; Reflection high energy electron diffraction; X-ray photoelectron spectroscopy

Characterization of plasma fluorinated zirconia for dental applications by X-ray photoelectron spectroscopy by S.D. Wolter; J.R. Piascik; B.R. Stoner (pp. 10177-10182).

► Using XPS we detailed chemical alteration stoichiometries at surface (and sub surface ∼40nm). ► Stoichiometries were noted to be a function of treatment time. ► Earlier studies confirm surface reactivity and increased adhesion with an underlying structure.This paper discusses fluorination of biomedical-grade yttria-stabilized zirconia (YSZ) by sulfur hexafluoride plasma treatment and characterization of near-surface chemistry products by X-ray photoelectron spectroscopy (XPS). Deconvolution of the Zr 3d and Y 3d XPS core level spectra revealed formation of both ZrF₄ and YF₃. In addition, seven-coordinate ZrO₂F₅ and/or ZrO₃F₄ phases were deconvolved, retaining similar atomic coordination as the parent oxide and believed to have formed by substitutional displacement of oxygen by fluorine. No additional components attributed to yttria oxyfluoride were deconvolved. Argon ion sputter depth profiling determined the overlayer to be ∼4.0nm in thickness, and angle resolved XPS showed no angle dependence on component percentages likely due to fluorination extending into the grain boundaries of the polycrystalline substrates. Importantly, the conversion layer did not induce any apparent change in zirconia crystallinity by inspection of Zr-O 3d_5/2,3/2 peak positions and full-width-at-half-maximum values, important for retaining its desirable mechanical properties.

Keywords: Surface modification; Zirconia; YSZ; Adhesion; XPS

A green synthetic approach to graphene nanosheets for hydrogen adsorption by Wenhui Yuan; Baoqing Li; Li Li (pp. 10183-10187).

This study propounds a green strategy of preparing graphene by reducing graphene oxide with glucose. The hydrogen adsorption experiment demonstrated that as-prepared graphene is supposed to be promising material with outstanding property for hydrogen storage. This opens a new approach for the synthesis of graphene with excellent properties.Display Omitted► Graphene sheets were prepared by a green and facile strategy based on glucose. ► The oxidized products of glucose can stabilize the as-prepared GS. ► Graphene sheets possessed single layer of graphene and 1205.8m²g⁻¹ BET surface area. ► The hydrogen adsorption capacity of 2.7wt.% at 298K and 25bar was obtained.A green and facile strategy of preparing graphene by reducing exfoliated graphite oxide (GO) with glucose was developed in this study. The as-prepared samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Atomic force microscopy (AFM). The characterization results indicated that the graphene sheets (GS) were of high quality with smooth surface, rich pore structure and few layer graphene. The samples have a BET specific surface area of 1205.8m²g⁻¹ measured by N₂ adsorption at 77K. The hydrogen storage capacity of 2.7wt.% at 298K and 25bar demonstrated that the as-prepared graphene employing glucose as reductant is supposed to be a promising material with outstanding property for hydrogen storage.

Keywords: Graphene; Hydrogen adsorption; Porous; Single layer; Green and facile

Sphere-like CuGaS₂ nanoparticles synthesized by a simple biomolecule-assisted solvothermal route by Jiasong Zhong; Yinsheng Zhao; Hailong Yang; Jing Wang; Xiaojuan Liang; Weidong Xiang (pp. 10188-10194).

• We report for the first time a simple biomolecule-assisted solvothermal route usingl-cystine as sulfur source and complexing agent to synthesis CuGaS₂ crystals. • The possible mechanisms leading to sphere-like CuGaS₂ nanoparticles were proposed. • Morphology, structure, phase composition and optical property of the as-prepared CuGaS₂ products were investigated in detail.Sphere-like CuGaS₂ nanoparticles were successfully synthesized by a simple biomolecule-assisted solvothermal route using a mixed solution compose of ethylenediamine and distilled water (1:1, v/v), in whichl-cystine was used as the sulfide source and complexing molecule. Phase analysis was carried out by X-ray diffraction (XRD) and the results confirmed the as-prepared CuGaS₂ as a single-phase tetragonal structure. Field-emission scanning electron microscope (FESEM) and transmission electron microscope (TEM) showed that the morphologies of CuGaS₂ were sphere-like nanoparticles in shape, and the average diameters was about 600nm. X-ray photoelectron spectrum (XPS) was used to analyze the composition of CuGaS₂ and the ratio of Cu/Ga/S is 1:0.97:1.98. Raman spectrum of the obtained CuGaS₂ exhibit a high-intensity peak of the A1 mode at 305cm⁻¹. The influence of reaction temperature, time and solvent was initially investigated. The possible formation mechanism was also discussed.

Keywords: CuGaS; ₂; Solvothermal; l; -Cystine; Raman spectrum

Wear behavior of sintered hexagonal boron nitride under atmosphere and water vapor ambiences by Yuxia Cao; Lingzhong Du; Chuanbing Huang; Wei Liu; Weigang Zhang (pp. 10195-10200).

► CaB₂O₄ can effectively promote the crystallization of hBN at 2000°C for 5h under N₂ ambience. ► The water vapor is benefit to the decrease of friction coefficients of the hBN. ► Lower friction coefficients of the hBN under water vapor ambience due to a lamella-slip and H₃BO₃.Hexagonal boron nitride was pressed and sintered at 2000°C with CaB₂O₄ as an additive to promote its crystallization, which was used as an abradable sealing coating for aircraft turbo engines. Microstructures, phase compositions and tribological properties of the sintered hBN were tested, and the results show that CaB₂O₄ can effectively promote crystal growth of hBN at 2000°C for 5h in N₂ ambience. The friction coefficients of the sintered hBN under atmosphere ambience increase as the temperature increasing from room temperature to 400°C, and then decrease with further increasing of temperature up to 800°C. Under water vapor ambience, friction coefficients of the sintered hBN are much lower than those under atmosphere ambience, which are attributed to a lamella-slip of hBN and the solid lubrication effect of H₃BO₃.

Keywords: Hexagonal boron nitride (hBN); Water vapor ambience; Sintering additive; Tribological property

Facile synthesis and capacitive performance of the Co(OH)₂ nanostructure via a ball-milling method by Liangyu Gong; Linghao Su (pp. 10201-10205).

► β-Co(OH)₂ nanoparticles were synthesized via a simple ball-milling technique. ► The capacitance of 599Fg⁻¹ is higher than the reported values of β-Co(OH)₂. ► Long cycle-life of the obtained β-Co(OH)₂ electrodes was also demonstrated.Co(OH)₂ nanoparticles were synthesized using only CoSO₄·7H₂O and NaOH as reactants without other auxiliary reagents via a simple, low-cost and practical ball-milling technique and investigated as the active electrode materials for supercapacitors. The structure and morphology of the resulting Co(OH)₂ samples were examined by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM). The observations revealed the formation of brucite-like phase of β-Co(OH)₂, which had an irregular sphere-like shape with an average size of 50–100nm. When investigated as electrode materials for supercapacitors, the β-Co(OH)₂ exhibited good energy-storage performances in terms of high specific capacitance of 599Fg⁻¹ and excellent capacity retention, suggesting its potential application in the electrode material for supercapacitors.

Keywords: Ball-milling method; Co(OH); ₂; nanoparticle; Electrochemical property

Ferromagnetism induced by intrinsic defects and nitrogen substitution in SnO₂ nanotube by Yongjia Zhang; Hua Liu; Hongwei Qin; Jifan Hu (pp. 10206-10210).

Display Omitted► The possible ferromagnetism (FM) in SnO₂ nanotube is investigated. ► Cation vacancy could induce the FM in SnO₂ nanotube. ► N substitution could induce the FM in SnO₂ nanotube.The possibilities of magnetism induced by intrinsic defects and nitrogen substitution in (5,5) single-wall SnO₂ nanotube are investigated by ab initio calculations. The calculated results indicate that a stoichiometric SnO₂ nanotube is nonmagnetic. The tin (Sn) vacancy can induce the magnetic moments rather than oxygen vacancy, which is originated from the polarization of O 2 p electrons. A couple of tin vacancies can lead to the ferromagnetic coupling. A nitrogen substitution for oxygen also produces magnetic moments. When substituting two nitrogen atoms, the characteristics of exchange coupling depend upon the distance of two nitrogen atoms. The longer distance of two nitrogen atoms prefers the ferromagnetic coupling, whereas the short distance leads to the antiferromagnetic coupling.

Keywords: SnO; ₂; nanotube; Magnetism; Ab initio; calculations; Vacancy

Fabrication of Ni–P/palygorskite core–shell linear powder via electroless deposition by Sumin Zhou; Li Wang; Shiming Shen (pp. 10211-10217).

► A linear core–shell Ni–P/micro-fiber palygorskite was fabricated. ► The powder was then characterized by SEM, EDS, and XRD. ► The powder exhibited good conductivity based on its linear structure. ► The powder forming mechanism was investigated.Palygorskite is a kind of hydrated magnesium aluminium silicate clay mineral. A novel linear core–shell structured Ni–P coated micro-fiber palygorskite (MFP) was fabricated via an electroless (EL) plating process in an alkaline bath. The composition, morphology and structure of the as-prepared products were characterized by the techniques such as powder X-ray diffraction (XRD), energy-dispersive X-ray spectrum (EDS), scanning electron microscopy (SEM) and transmission electron microscope (TEM). It was observed that the size and morphology of Ni–P coated MFPs were altered by depositing temperature and time. The as-prepared Ni–P coated MFPs showed good conductivity. To the best of our knowledge, the Ni–P coated MFPs have not been reported before. And this fabrication process might also apply in preparing other metal coated MFPs such as silver, copper and palladium.

Keywords: Electroless deposition; Ni–P; Palygorskite micro-fibers

Synthesis of magnetic and lightweight hollow microspheres/polyaniline/Fe₃O₄ composite in one-step method by Li Sun; Qin Li; Wei Wang; Jianfeng Pang; Jianping Zhai (pp. 10218-10223).

► Hollow microspheres/polyaniline/Fe₃O₄ composite was prepared in one-step method. ► The composites possess low density, controllable morphology, and good magnetic properties. ► This method is environmental friendly and cost saving to prepare magnetic composites.After hollow microspheres (HM) were surface modified, a layer of electromagnetic polyaniline/Fe₃O₄ composite (PAN/Fe₃O₄) was successfully grafted onto the surface of the self-assembled monolayer coated HM, resulting in HM/PAN/Fe₃O₄ composites. In this approach, γ-aminopropyltriethoxy silane was adopted to form a well-coating monolayer with amino groups for the graft polymerization of aniline, which played an important role in fabricating the core–shell structure. FeCl₃ was used as the oxidant not only for aniline to form PAN, but also for FeCl₂ to prepare the magnets. The structure, morphologies, and magnetic properties of the as-prepared samples were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and vibrating sample magnetometer. The results indicated that the HM/PAN/Fe₃O₄ composites possess low density ( ρ<1.0g/cm³), controllable morphology, and good magnetic properties at room temperature (saturation magnetization Ms=8.32emug⁻¹ and coercive force Hc≈0).

Keywords: Hollow microspheres; Polyaniline; Composite; Magnetic; Self-assemble; Core–shell structure

Cycle oxidation behavior of nanostructured Ni60–TiB₂ composite coating sprayed by HVOF technique by Y.S. Wu; W.Q. Qiu; H.Y. Yu; X.C. Zhong; Z.W. Liu; D.C. Zeng; S.Z. Li (pp. 10224-10232).

► Nanostructured coating has been successfully prepared by HVOF. ► We evaluate its cycle oxidation resistance at 800°C in static air. ► The coating forms a complete-protective external oxide film during cycle oxidation. ► Nanostructured coating has excellent cycle oxidation resistance.Cycle oxidation resistance at 800°C in static air was investigated for a nanostructured Ni60–TiB₂ composite coating sprayed by high velocity oxy-fuel (HVOF). For comparison, a Ni60–TiB₂ conventional composite coating was also studied. The results indicate that, the oxidation processes of both composite coatings are controlled by diffusion mechanism, and the nanostructured composite coating has better cycle oxidation resistance than that of the conventional composite coating. The reasons for this improvement can be attributed to the formation of the intact SiO₂ and Cr₂O₃ protective layer, and the enhanced adhesion between oxide film and nanostructure coating.

Keywords: Cycle oxidation; Nanostructured composite coating; HVOF; Ni60–TiB; ₂

Deposition of ZnO multilayer on LiNbO₃ single crystals by DC-magnetron sputtering by M. Shirazi; M.T. Hosseinnejad; A. Zendehnam; Z. Ghorannevis; M. Ghoranneviss (pp. 10233-10238).

► Deposition of ZnO multilayer on LiNbO₃ substrate is followed by thermal oxidation of Zn thin films. ► Optical and structural properties of ZnO thin films are analyzed by PL, XRD, SEM, and AFM. ► Multilayer of ZnO showed high transmittance and low structural defect due to a lower PL intensity and Urbach energy. ► Average grain size in XRD, SEM and AFM images for multilayer of ZnO was lower than monolayer of ZnO thin films. ► Applying multilayer coating method leads to decrease of surface roughness and optical loss on LiNbO₃ waveguides.Zinc oxide (ZnO) thin films were deposited on LiNbO₃ (LN) single crystals with 200nm thicknesses by three different ways, where coating of zinc (Zn) film was followed by thermal oxidation for four, two, and one steps with 50, 100, and 200nm thicknesses repeatedly. Sample, which was produced at 4-step of deposition and oxidation of Zn layer, showed high transmittance and low structural defect due to a lower photoluminescence intensity and Urbach energy. Average grain size in X-ray diffraction (XRD), scanning electron microscopy (SEM) micrograph, and atomic force microscopy (AFM) images for multilayer of ZnO was lower than monolayer of ZnO thin films. Applying multilayer coating technique leads to decrease of surface roughness and scattering on light on surface and fabrication of LiNbO₃ waveguides with lower optical loss.

Keywords: LiNbO; ₃; ZnO multilayer; Thermal oxidation; PL; SEM; AFM

Effects of argon plasma treatment on the interfacial adhesion of PBO fiber/bismaleimide composite and aging behaviors by Dong Liu; Ping Chen; Mingxin Chen; Qi Yu; Chun Lu (pp. 10239-10245).

► The ILSS increased rapidly with the processing time, followed by a gradual decrease. ► The fiber surface elements had a small variation. The C–O bonds broke down and the amide groups generated. ► The surface roughness increased, contributing to the wettability. Proper roughness was needed for the enhanced adhesion. ► The adhesion degraded with the aging time in air. ► The composite had a good resistance to humidity.This paper is concerned with the influence of argon plasma on the interfacial adhesion of PBO fiber/bismaleimide composites and aging behaviors. The interlaminar shear strength (ILSS) was greatly increased to 62.3MPa with an increase of 39.7% after treatment for 7min at 80Pa, 200W. A small amount of O and N atoms was incorporated onto the fiber surface, but the plasma caused C–O bonds to break and generated OC–N groups. The fiber surface roughness increased, contributing much to the wettability. However, long-time treatment excessively destroyed the inherent and newly created structures. The SEM images suggested that the fracture shifted from the interface to the matrix. The modification effects degraded with storage time in the air and the ILSS decreased to approximately 54.0MPa after 10–30 days. The composite had low water absorption of 2.0wt% and a high retention of 90% in the ILSS at moisture conditions.

Keywords: PBO fiber; Argon plasma; Interfacial adhesion; Aging behavior; Humid resistance

Improving the tribological performances of graphite-like carbon films on Si₃N₄ and SiC by using Si interlayers by Yongxin Wang; Liping Wang; Qunji Xue (pp. 10246-10253).

Friction and wear models for the GLC films on Si-based substrate with Si interlayers in: (a) ambient air; (b) water.Display Omitted► GLC-coated Si₃N₄ and SiC exhibit low friction and wear in both ambient air and water. ► Dense Si interlayer bonds well with both Si-based substrate and GLC layer. ► Mild wear of GLC on Si₃N₄ and SiC in water is closely related to the Si interlayers.Si interlayers were used to obtain the excellent tribological performances of graphite-like carbon (GLC) film on silicon nitride (Si₃N₄) and silicon carbide (SiC). The microstructure and mechanical characteristics of the as-prepared GLC films with Si interlayers were investigated by scanning electron microscopy, Raman spectroscopy, nanoindention and scratch test. The tribological behaviors of GLC-coated and uncoated Si₃N₄ and SiC were comparatively studied by a ball-on-disc tribo-meter in both dry and water environments. Results showed that the Si interlayers were dense and bonded well with both the substrates and GLC layers. The as-prepared GLC films exhibited excellent tribological performances in both dry and water environments. More importantly, the stably mild wear without any delamination was obtained in water by using Si interlayer. The mechanisms of friction reduction and anti-wear performances of GLC films on the two ceramics with Si interlayers under different environmental conditions were discussed, as well as the corresponding models were deduced.

Keywords: Si; ₃; N; ₄; SiC; Graphite-like carbon film; Si interlayer; Tribological performance; Water

Annealing improves tribological property of poly(octadecene- alt-maleic anhydride) self-assembled film by Shiyong Song; Lei Liu; Junyan Zhang (pp. 10254-10260).

► A structurally special poly(octadecene- alt-maleic anhydride) (POMA) is chosen to be covalently grafted to silicon surface by stepwise method. ► The effect of annealing treatment on tribology was found. ► Multiple surface analysis techniques were applied to detect the structural details. ► A relationship between structure and tribological property of the film was revealed.A poly(octadecene- alt-maleic anhydride) (POMA) film was covalently immobilized on N-[3-(trimethoxylsilyl)propyl]ethylenediamine self-assembled monolayer modified silicon surface. Attenuated total reflectance Fourier transform infrared spectra were used to confirm the chemical bonding. Water contact angles and ellipsometric thicknesses were measured before and after annealing treatment. Atomic force microscopy was applied for top morphology, surface adhesion force and friction force. Anti-wear properties of the films were also evaluated on a ball-on-plate tribometer. It was found that annealing treatment which would evoke a conformation transform thermodynamically, was a critical step in the preparation of anti-wear films, especially for polymer ones. The correlation between structure and tribological property was revealed, which has profound meaning in designing excellent anti-wear nano-coatings used in microelectronic mechanical systems (MEMS).

Keywords: POMA; Self-assembled film; Friction; Anti-wear, AFM

One-pot, efficient functionalization of multi-walled carbon nanotubes with diamines by microwave method by A. Amiri; M. Maghrebi; M. Baniadam; S. Zeinali Heris (pp. 10261-10266).

► In this study, three diamines (EDA, HMDA and DAB) were successfully added on the surface of MWCNTs in a microwave-assisted method. ► The procedure was fast, one-pot, simple and resulted in a high degree of functionalization as well as solubility in ethanol. ► For the case of EDA- and HMDA-treated MWCNTs, diamine functionality seems to cross-link the adjacent MWCNTs. ► NaNO₂ catalyst was appeared to be fundamental for the functionalization reaction to take place.Diamines are known to act as a medium to bind miscellaneous compounds to carbon nanotubes (CNT). However, they are commonly applied in a tedious manner. Here, multi-walled carbon nanotubes (MWCNTs) were functionalized by a series of diamine molecules (ethylenediamine, 1,6-hexamethylenediamine and 1,4-diaminobenzen) in a one-pot, rapid microwave-assisted method. Surface functionality groups and morphology of MWCNTs were analyzed by infrared spectroscopy, thermogravimetric analysis, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. The results consistently confirmed the formation of diamines functionalities on MWCNTs, while the structure of MWCNT has remained relatively intact. This simple and efficient process may play an important role for realizing miscellaneous functionalization of CNTs.

Keywords: Carbon nanotubes; Functionalization; Microwave; Diamines

Microstructure and tribological behaviors of Ti6Al4V alloy treated by plasma Ni alloying by Zhenxia Wang; Zhiyong He; Yingqin Wang; Xiaoping Liu; Bin Tang (pp. 10267-10272).

► The Ni modified layer is prepared by plasma surface alloying technique. ► The Ni modified layer is composed of TiNi, Ti₂Ni and Ti phases. ► The hardness of the Ni modified layer is improved. ► Better tribological performance is attributed to synergy of Ti₂Ni and TiNi. ► The Ni modified layer shows micro-abrasion wearing.Ni modified layer was prepared on surface of the Ti6Al4V substrate by plasma surface alloying technique. Surface morphology, micro-structure, composition distribution, phase structure, and microhardness of the Ni modified layer were analyzed. Tribological performance of the Ni modified layer and Ti6Al4V substrate was investigated by using pin-on-disc tribometer. The results indicate that roughness of the Ni modified layer was increased due to formation of the micro-convex on the modified surface. The concentration of Ni gradually decreased from the surface to interior. The maximum content of Ni atoms was nearly 90%. The modified layer was composed of TiNi, Ti2Ni and Ti phases. The maximum microhardness of the Ni modified layer was about 677HV_0.025 which was increased about two-fold of microhardness of the control Ti6Al4V substrate. Wear resistance of the Ni modified layer was improved obviously, and showed micro-abrasion wearing. The strengthened mechanism of the as-treated Ti6Al4V alloy is discussed.

Keywords: Ti6Al4V; Ni modified layer; Wear and friction; Plasma alloying

Preparation and high-temperature properties of Au nano-particles doped α-Al₂O₃ composite coating on TiAl-based alloy by Xiaoxu Ma; Yedong He; Deren Wang (pp. 10273-10281).

► The Au nano-particles doped Al₂O₃ coatings were prepared by electrodepositon. ► The prepared coatings exhibit excellent oxidation and spallation resistance. ► Coating with more Au (wt.%) provides better oxidation and spallation resistance. ► The Au doped Al₂O₃ composite structure enhances the strength of the oxide scale. ► The oxidation rate of substrate alloy and the cost of Au are both extremely low.Au nano-particles doped α-Al₂O₃ composite coatings were successfully prepared on TiAl-based alloy by electrodeposition, using the Al₂O₃ sols with minor addition of HAuCl₄ solution. The even distribution of Au nano-particles (<2.0wt.%) in the α-Al₂O₃ matrix has been observed. Isothermal oxidation tests of the samples coated with the as-prepared novel coatings at 900°C in static air for 200h shown that the oxygen inward diffusion can be effectively suppressed to a low level. The results of high-temperature cyclic oxidation test at 900°C in air revealed that the oxidation and spallation resistance of TiAl-based alloy were improved significantly under thermal cycling. In the as-prepared coatings, cracks were shielded by means of crack bridging and the fracture resistance of the formed scales can be improved by toughening effects of the composite structure. Surface scratching tests after the cyclic oxidation exhibited that the adhesion of the formed composite scale on TiAl-based alloy was remarkably improved by the Au nano-particles doped α-Al₂O₃ composite coating.

Keywords: Nanocomposites; Mechanical properties; Thermal shock resistance; Al; ₂; O; ₃; High-temperature oxidation

Atmospheric reactive plasma sprayed Fe–Al₂O₃–FeAl₂O₄ composite coating and its property evaluation by Lin Zhu; Jining He; Dianran Yan; Yanchun Dong; Jianxin Zhang; Xiangzhi Li; Hanlin Liao (pp. 10282-10288).

► Fe–Al₂O₃–FeAl₂O₄ composite coatings were synthesized by atmospheric reactive plasma sprayed Al/Fe₂O₃ agglomerated powder. ► In situ synthesized metal phase can effectively toughen ceramic coating matrix. ► The formation and toughening mechanisms of the composite coating were clarified.In the present study, Fe–Al₂O₃–FeAl₂O₄ composite coatings were successfully deposited by reactive plasma sprayed Al/Fe₂O₃ agglomerated powder. Phase composition and microstructure of the coatings were determined by XRD and SEM. The results indicated that the composite coatings were principally composed of three different phases, i.e. FeAl₂O₄ phase as main framework, dispersed ball-like Fe-rich phase, and small splats of Al₂O₃ phase, and it was thought that the in situ synthesized metal phase was helpful to toughen the coating matrix. According to the results of the indentation and frictional wear tests, the composite coating exhibited excellent toughness and anti-friction properties in comparison with conventional Al₂O₃ monophase coating, though its microhardness value was a little lower than that of Al₂O₃ coating. The formation mechanism and the toughening mechanism of the composite coating were clarified in detail.

Keywords: Reactive plasma spray; Alumina; Microhardness; Wear; Toughening

Synthesis, characterization, growth mechanism, photoluminescence and field emission properties of novel dandelion-like gallium nitride by Ghulam Nabi; Chuanbao Cao; Waheed S. Khan; Sajad Hussain; Zahid Usman; Muhammad Safdar; Sajjad Hussain Shah; Noor Abass Din Khattak (pp. 10289-10293).

► Dandelion-like GaN with size of 30–60μm have been synthesized by CVD method. ► VLS growth mechanism has been discussed for novel dandelion-like GaN structures. ► FE properties showed turn-on field of 9.65Vμm⁻¹ and threshold field of 11.35Vμm⁻¹_. ► This turn-on field value is enough for potential use in the electron emission devices. ► Strong PL emission peak at 370.2nm showed its vast applications in LEDs and devices.Dandelion-like gallium nitride (GaN) microstructures were successfully synthesized via Ni catalyst assisted chemical vapor deposition method at 1200°C under NH₃ atmosphere by pre-treating precursors with aqueous ammonia. The as-synthesized product was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). X-ray diffraction analysis revealed that as-synthesized dandelion-like GaN was pure and has hexagonal wurtzite structure. SEM results showed that the size of the dandelion-like GaN structure was in the range of 30–60μm. Dandelion-like GaN microstructures exhibited reasonable field emission properties with the turn-on field of 9.65Vμm⁻¹ (0.01mAcm⁻²) and threshold field of 11.35Vμm⁻¹ (1mAcm⁻²) which is sufficient for applications of electron emission devices, field emission displays and vacuum micro electronic devices. Optical properties were studied at room temperature by using fluorescence spectrophotometer. Photoluminescence (PL) measurements of dandelion-like GaN showed a strong near-band-edge emission at 370.2nm (3.35eV) with blue band emission at 450.4nm (2.75eV) and 465.2nm (2.66eV) but with out yellow band emission. The room-temperature photoluminescence properties showed that it has also potential application in light-emitting devices. The tentative growth mechanism for the growth of dandelion-like GaN was also described.

Keywords: Dandelion-like GaN; Semiconductor; CVD method; Field emission properties

Study of deposition patterns of plating layers in SiC/Cu composites by electro-brush plating by Xiangliang Li; Xibao Wang; Rui Gao; Li Sun (pp. 10294-10299).

► We found three different patterns of SiC deposition in copper plating layers during electro-brush plating. ► Deposition patterns depend on comparison of size of copper grains and hard particles. ► Hardness of SiC/Cu coatings reaches a maximum at the current density of 3A/dm².SiC reinforced copper composite coatings were prepared by electro-brush plating with micron-size silicon carbide (SiC) ranging from 1 to 5μm on pure copper sheet in this paper. The micro-structural characterizations of SiC/Cu composite coatings were performed by optical microscope and Scanning Electron Microscope (SEM) coupled with spectrometer, to study co-deposition mechanism of SiC/Cu. It was found that there were three different patterns of SiC deposition in plating layers during electro-brush plating process, i.e. the particles could deposit inside copper grains, in grain boundaries, or in holes of the surface. To investigate deposition mechanism of each pattern, size of SiC and copper grains was compared. By comparison of size of copper grains and hard particles, SiC were either wrapped in copper grains or deposited in grain boundaries. Moreover, electro-brush plating layers at different brush velocities and current densities were obtained respectively, to analyze the microstructure evolution of the composite coatings. The hardness of plating layers was measured. The results indicated at the current density of 3A/dm², the SiC/Cu coating was compact with SiC content at a high level and the hardness reached a maximum.

Keywords: Electro-brush plating; SiC; Plating layers; Growth mode; Deposition patterns

Intricate photocatalytic decomposition behavior of gaseous methanol with nanocrystalline tungsten trioxide films in high vacuum by Shivaji B. Sadale; Kei Noda; Kei Kobayashi; Kazumi Matsushige (pp. 10300-10305).

► WO₃ thin films with different morphologies were prepared by varying the concentration of organic additive in the precursor solution. ► Direct hole transfer reaction for decomposition of methanol has been observed. ► The decomposition of methanol proceeds through intermediates viz. CH₂O, CO, and finally to CO₂. ► The decrease in photocatalytic activity was observed because of photo-induced desorption of methanol and formation of tungsten bronze. ► Tungsten bronze was formed as result of intercalation of protons generated from the decomposition of methanol.Gas phase photocatalytic decomposition of methanol with nanocrystalline tungsten trioxide (WO₃) thin films in high vacuum was investigated. WO₃ thin films were prepared from a novel precursor prepared using peroxo-tungstic acid and polyethylene glycol (PEG300) in water. Uniform thin films of WO₃ with different morphologies such as micro-sheets, platelets, nanorods and nanoparticles were fabricated by varying the concentration of PEG300 in the precursor solution and by optimizing other preparative parameters. Nanocrystalline thin films were obtained with 20% of PEG300 in the precursor solution and at a calcination temperature of 350°C, followed by post annealing in air at 500°C. Photocatalytic decomposition of gaseous methanol in high vacuum was examined with nanocrystalline WO₃ thin films using a quadrupole mass spectrometer at a real-time scale under visible (400–700nm) and UVA (300–400nm) illumination. Methanol was first decomposed to formaldehyde via direct hole transfer mechanism. Subsequently formaldehyde was decomposed to CO and finally to CO₂. As a result, the partial pressures of CH₂O, CO and CO₂ showed a switching phenomenon according to the ON/OFF of light illumination. A rapid decrease in the photocatalytic activity was observed due to photo-induced desorption of methanol during the initial light pulse and gradual decrease at longer times was observed because of formation of tungsten bronze. Thus, the overall process of methanol decomposition over WO₃ films is complex convolution of elementary steps that involve several intermediates.

Keywords: Tungsten trioxide; Drop casting; Photocatalysis; Gas phase; Methanol decomposition; Photo-induced desorption

A comparative study of thermionic emission from vertically grown carbon nanotubes and tungsten cathodes by S.K. Kolekar; S.P. Patole; P.S. Alegaonkar; J.B. Yoo; C.V. Dharmadhikari (pp. 10306-10310).

Thermionic emission from vertically grown carbon nanotubes (CNTs) by water-assisted chemical vapor deposition (WA-CVD) is investigated. I– V characteristics of WA-CNT samples exhibit strong Schottky effect leading to field proportionality factor β∼10⁴cm⁻¹in contrast to β∼200cm⁻¹ for the bare tungsten substrate. Non-contact atomic force microscopy imaging of CNT samples show propensity of nanoasperities over a scale of micron size over which the tungsten surface is seen to be atomically smooth. The values of root mean-square roughness for CNTs and W were found to be 24.2nm and 0.44nm respectively. The Richardson–Dushman plots yield work function values of Φ_CNT≃4.5 and Φ_W≃4.3eV. Current versus time data shows that CNT cathodes are fifteen times noisier than tungsten cathode presumably due to increased importance of individual atomic events on the sharp CNT tips of bristle like structures. Power spectral density of current exhibited 1/ f^ξ behavior with ξ≃1.5, and 2 for W and CNTs. The former suggests surface diffusion whereas the latter indicates adsorption/desorption of atomic/molecular species as a dominant mechanism of noise generation.

Keywords: Thermionic emission; Carbon nanotubes; Cathode materials

Zirconium-assisted reaction in low temperature atomic layer deposition using Bis(ethyl-methyl-amino)silane and water by Seok-Jun Won; Joon Rae Kim; Sungin Suh; Yu Jin Choi; Hyeong Joon Kim (pp. 10311-10313).

The reaction of Bis(ethyl-methyl-amino)silane (BEMAS) and water in atomic layer deposition (ALD) became possible when Zr-containing species were adsorbed on the vacant sites of the surface after a pulse and purge of BEMAS. The growth rates of the Si(Zr)O_x films were 0.8–0.9nm/cycle in the temperature range of 185–325°C. This phenomenon probably originates from the highly reactive hydroxyl species generated by Zr atoms. From this point of view, transition metals make reactant gas molecules to be highly activated in the ALD processes of transition metal oxides and nitrides, which might be an important factor that determines the ALD characteristics.

Keywords: Atomic layer deposition; Silicate; Hydroxyl; Transition metal

Erratum to “Growth of Mg_xZn1−_xO films using remote plasma MOCVD” [Appl. Surf. Sci. 244 (2005) 385–388] by Atsushi Nakamura; Junji Ishihara; Satoshi Shigemori; Toru Aoki; Jiro Temmyo (pp. 10314-10316).

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Applied Surface Science (v.257, #23)

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Applied Surface Science (v.257, #23)