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Applied Surface Science (v.270, #)

Editorial Board (pp. ii).

Food contact surfaces coated with nitrogen-doped titanium dioxide: effect on Listeria monocytogenes survival under different light sources by D. Rodrigues; P. Teixeira; C.J. Tavares; J. Azeredo (pp. 1-5).

► No significant reduction of the bacterial load was achieved on any of the coated surfaces after exposure to each light source used. ► UV irradiation was the most effective on reducing the number of viable cells on coated surfaces. ► Both visible light sources had promoted some level of Listeria monocytogenes killing on both coated materials. ► N-TiO₂ coating needs improvement to be truly effective against foodborne pathogens.Improvement of food safety is a very important issue, and is on the basis of production and application of new/modified food contact surfaces. Titanium dioxide (TiO₂) and, more recently, nitrogen-doped titanium dioxide (N-TiO₂) coatings are among the possible forms to enhance food contact surfaces performance in terms of higher hygiene and easier sanitation. In this context, the present work aimed at evaluating the bactericidal activity of an N-TiO₂ coating on glass and stainless steel under two different sources of visible light – fluorescent and incandescent – and ultraviolet (UV) irradiation. Listeria monocytogenes was chosen as representative of major foodborne pathogens and its survival was tested on N-TiO₂ coated coupons. In terms of survival percentage, good results were obtained after exposure of coated surfaces to all light types since, apart from the value obtained after exposing glass to fluorescent light (56.3%), survival rates were always below 50%. However, no effective disinfection was obtained, given that for a disinfectant or sanitizing agent to be claimed as effective it needs to be able to promote at least a 3-log reduction of the microbial load, which was not observed for any of the experimental conditions assessed. Even so, UV irradiation was the most successful on eliminating cells on coated surfaces, since the amount of bacteria was reduced to 1.49×10⁶CFU/ml on glass and 2.37×10⁷ on stainless steel. In contrast, both visible light sources had only slightly decreased the amount of viable cells, which remained in the range of 8logCFU/ml. Hence, although some bactericidal effect was accomplished under visible light, UV was the most effective light source on promoting photocatalytic reactions on N-TiO₂ coated coupons and none of the experimental conditions have reached a satisfactory disinfection level. Thus, this surface coating needs further research and improvement in order to become truly effective against foodborne pathogens and, ultimately, become a useful tool towards food safety in general.

Keywords: Food-contact surfaces; N-TiO; ₂; coating; Photocatalytic disinfection; Listeria monocytogenes

Controllable fabrication of 2D colloidal-crystal films with polystyrene nanospheres of various diameters by spin-coating by Jian Chen; Peitao Dong; Di Di; Chaoguang Wang; Haoxu Wang; Junfeng Wang; Xuezhong Wu (pp. 6-15).

► Self-assembly, spin-coating, polystyrene nanosphere, colloidal-crystal films, physical mask.Monolayer and bilayer colloidal-crystal films are used as physical mask in nanosphere lithography (NSL). So far, spin-coating experiments have mainly been designed to form nanosphere monolayer with one given size or obtain small areas of polystyrene (PS) nanosphere monolayer which limited the application of these films used as physical masks. The development of NSL required more study focused on the preparation of colloidal-crystal films with large-scale, high ordering degree and nanospheres of different diameters. In this study, PS nanospheres were self-assembled to form monolayer and bilayer colloidal-crystal films by employing spin-coating technology. Based on our experiments, we have built an experiment system of PS nanospheres of certain size ranging from 200nm to 1300nm. To give an instance, we have chosen PS nanospheres of four diameters (223nm, 347nm, 509nm, 1300nm) to fabricate colloidal-crystal films by adjusting the spin speed and acceleration, and we have investigated the relationship between the monolayer coverage areas and spin parameters by designing different spin speed and acceleration for 509nm nanosphere. Results revealed that monolayer and bilayer films of PS nanospheres with four different diameters were prepared successfully and the single structure where PS nanospheres were in hexagonal close-packed (HCP) order dominated the surface morphologies of both monolayer and bilayer colloidal-crystal films. For 509nm PS nanosphere, as the spin speed and acceleration increasing, the monolayer coverage areas increase firstly then decrease and at spin speed 1750rpm and acceleration 600rpm/s, the areas reaches the biggest.

Keywords: Self-assembly; Spin-coating; Polystyrene nanosphere; Colloidal-crystal films; Physical mask

Chemical evolution of InP/InGaAs/InGaAsP microstructures irradiated in air and deionized water with ArF and KrF lasers by Neng Liu; Jan J. Dubowski (pp. 16-24).

► Greater concentrations of oxides observed in InP/InGaAs/InGaAsP QW microstructures irradiated in air than in those irradiated in DI water ► Rapid thermal annealing decomposes surface oxides and induces oxygen atoms diffusion toward the active region of the QW microstructures ► Excessive amount of oxygen in the laser irradiated and RTA samples is consistent with the enhanced intermixing and bandgap blue shifting ► Following the RTA step, the chemical composition of the excimer laser irradiated InP cap becomes indistinguishable from that of as-grown InP.Irradiation of quantum semiconductor microstructures with ultraviolet pulsed lasers could induce surface defects and modify chemical composition of the microstructure capping material that during high-temperature annealing leads to selected area bandgap engineering through the process known as quantum well intermixing (QWI). In this work, we investigate the role of both ArF and KrF excimer lasers in the QWI process of InP/InGaAs/InGaAsP microstructures irradiated in air and deionized (DI) water. X-ray photoelectron spectroscopy and secondary ion mass spectroscopy analysis was employed to study the chemical composition of the irradiated surface and investigate the chemical evolution of ArF and KrF laser irradiated microstructures. The results indicate that InP_xO_y oxides are the dominating surface products of the ArF and KrF lasers interaction with InP. Consistent with this observation is a relatively greater bandgap blue shift of ∼130nm found in the microstructures irradiated in air, in comparison to a maximum of 60nm blue shift observed in the microstructures irradiated in a DI water environment.

Keywords: Quantum well intermixing; InP/InGaAs/InGaAsP microstructures; ArF and KrF excimer laser irradiation; X-ray photoelectron spectroscopy; Secondary ion mass spectroscopy; Indium and InP oxides

A first-principles study of the adsorption behavior of CO on Al- and Ga-doped single-walled BN nanotubes by Ali Ahmadi Peyghan; Alireza Soltani; Amin Allah Pahlevani; Yaser Kanani; Soheila Khajeh (pp. 25-32).

► The adsorption energy of CO molecule on surfaces of Al- and Ga-doped (6, 0), (8, 0), and (5, 5) BNNTs are studied. ► Binding energy of CO on outer walls of Al- and Ga-doped (6, 0) and (8, 0) BNNT are energetically more notable in comparison with Al- and Ga-doped (5, 5) BNNT.► Our computations indicate that the Al- and Ga-doped BNNT can be used as potential sensor for CO molecule. ► The energy gap of BNNT is decreased in all of the cases for CO adsorption.First-principles computations have been applied to scrutinize the adsorption behavior of CO molecule on the external surface of H-capped aluminum- and gallium-doped (6, 0), (8, 0) zigzag and (5, 5) armchair single-walled BN nanotubes (SWBNNTs). Binding energy corresponding to the most stable configuration of CO on the gallium-doped (6, 0) BNNT is found to be −0.83eV, which is high typical sensitivity to CO molecule. Our results indicate that both Al- and Ga-doping can notably enhance the adsorption energy of CO/BNNTs complexes. Our electronic results reveal that there is a notable orbital hybridization among two species in adsorption process being an evidence of strong interaction. For the CO/BNNTs complexes, the energy gaps, NBO, dipole moments, natural atomic orbital occupancies and global indices are computed. Finally, we reported a novel type of toxic gas sensor that can be used for detecting the presence of CO molecule.

Keywords: Adsorption; BNNT; CO; Metal doping; Chemisorptions

Evaluation of shape and size effects on optical properties of ZnO pigment by Narges Kiomarsipour; Reza Shoja Razavi; Kamal Ghani; Marjan Kioumarsipour (pp. 33-38).

Display Omitted► The optical properties of ZnO pigments were strongly affected by their size and morphology. ► ZnO particles with diameters greater and smaller than approximately 0.25 and 1.5μm, respectively, do not scatter light efficiently at any wavelength. ► ZnO particles with diameters in the range of 0.25–1.5μm, indicated the suitable spectral reflectance. ► The nanoparticle-decorated ZnO pigment revealed the highest spectral reflectance due to their higher surface roughness.The pigment with optimized morphology would attain maximum diffuse solar reflectance at a lower film thickness and reduce the pigment volume concentration required. This factor would contribute to a reduction in overall weight and possibly extend the durability of the system to longer time scales, specially in space assets. In the present work, five different morphologies of ZnO pigment were synthesized by hydrothermal method. The ZnO pigments were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and N₂ adsorption (BET). The optical property of the ZnO pigments was investigated by UV/VIS/NIR spectrophotometer. The results indicated that the optical properties of ZnO powders were strongly affected by the particle size and morphology. The nanorods and microrods ZnO structures showed the minimum spectral reflectance in visible and near infrared regions, whereas the novel nanoparticle-decorated ZnO pigment revealed the maximum spectral reflectance in the same regions. The reflectance spectra of scale-like and submicrorods ZnO were in the middle of the others. The higher surface roughness led to higher light scattering in nanoparticle-decorated ZnO pigment and multiple-scattering in them. These results proved that a significant improvement in the scattering efficiency of ZnO pigment can be realized by utilizing an optimized nanoparticle-decorated pigment.

Keywords: Zinc oxide pigment; Light scattering efficiency; Optical property; Hydrothermal method

Effect of double source Titanium deposited in nitriding steels on their mechanical properties by I. Rosales; H. Martinez; R.Guardian; B.A. Sosa-Coeto (pp. 39-43).

► We report the strengthening of the nitriding layer in tree steels by means of use a double Ti source and a complementary diffusion method. ► Nitrided layers titanium reinforced shown several micrometers thick reducing the nitriding time, and increasing the mechanical properties. ► Fracture toughness evaluation present a significant increment in the treated samples.We report the improved mechanical properties of three kinds of nitriding steels modified by titanium diffusion either by depositing titanium by PVD and hot-pressing the steel with titanium sheets hot pressed at 950°C. The steels used were AISI series: 1045, O-1 and H-13. A mixed layer of Ti and N compounds was generated by a post treatment. Hardness measurements showed an increase of approximately two times in hardness with respect to the annealed condition. The results of fracture toughness tests indicated excellent strengthening of the steels. The role of composition and microstructure on strengthening are discussed.

Keywords: Diffusion; Hardness; Mechanical properties; Surface modification; Modeling

Penetration depth profiling of proton-irradiated 4H-SiC at 6MeV and 8MeV by micro-Raman spectroscopy by Hong-Yeol Kim; Jihyun Kim; Jaime A. Freitas Jr (pp. 44-48).

► Proton-irradiated 4H-SiC was probed by micro-Raman scattering spectroscopy. ► The changes of the line-shape and peak position in LOPC mode were analyzed. ► The estimated penetration depths from 6 to 8MeV energy protons were 180 and 300μm, respectively.4H-SiC samples irradiated with high energy protons were probed by low temperature photoluminescence (PL) and room temperature micro-Raman scattering spectroscopies. The quench of the near band-edge emission and the presence of a number of new sharp lines in the luminescence spectra of the proton-irradiated samples confirm the formation of various new defects. The changes of the line-shape and peak position of the longitudinal optical phonon-plasmon coupled (LOPC) mode in 4H-SiC are consistent with the decrease in the free carrier concentrations due to the introduction of carrier traps induced by the high energy proton irradiation. The estimated penetration depths for 6 and 8MeV energy proton were 180μm and 300μm, respectively, which are in good agreement with the Monte Carlo numerical simulation results. At the 180μm and 300μm depths, the carrier concentrations were reduced by approximately 34% and 21%, respectively.

Keywords: 4H-SiC; Proton irradiation; Raman spectroscopy

Effect of dry and wet ambient environment on the pulsed laser ablation of titanium by Nisar Ali; Shazia Bashir; Umm-i-Kalsoom; Mahreen Akram; Khaliq Mahmood (pp. 49-57).

► Effect of dry and liquid confined environment on Excimer laser ablation performance of titanium has been investigated. ► The surface morphology and crystallinity are investigated for various number of laser pulses. ► Various features like grains, cavities, pores and cracks are observed by SEM analysis. ► From XRD analysis it is revealed that new phases are formed under various ambient conditions.Surface and structural properties of the laser irradiated titanium targets have been investigated under dry and wet ambient environments. For this purpose KrF Excimer laser of wavelength 248nm, pulse duration of 20ns and repetition rate of 20Hz has been employed. The targets were exposed for various number of laser pulses ranging from 500 to 2000 in the ambient environment of air, de-ionized water and propanol at a fluence of 3.6J/cm². The surface morphology, chemical composition and crystallographical analysis were performed by using Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD), respectively. For both central and peripheral ablated areas, significant difference in surface morphology has been observed in case of dry and wet ambient conditions. Large sized and diffused grains are observed in case of dry ablation. Whereas, in case of wet ablation, small sized, and well defined grains with distinct grain boundaries and significantly enhanced density are revealed. This difference is ascribed to the confinement effects of the liquid. The peripheral ablated area shows redeposition in case of dry ablation whereas small sized grain like structures are formed in case of wet ablation. EDS analysis exhibits variation in chemical composition under both ambient conditions. When the targets are treated in air environment, enhancement of the oxygen as well as nitrogen content is observed while in case of de-ionized water and propanol only increase in content of oxygen is observed. X-ray diffraction analysis exhibits formation of oxides and nitrides in case of air, whereas, in case of de-ionized water and propanol only oxides along with hydrides are formed. For various number of laser pulses the variation in the peak intensity, crystallinity and d-spacing is observed under both ambient conditions.

Keywords: Titanium; Laser ablation; Ambient environment; Surface morphology

The effect of multi-scale laser textured surface on lubrication regime by Dawit Zenebe Segu; Si Geun Choi; Jae hyouk Choi; Seock Sam Kim (pp. 58-63).

► The effect of multi-scale laser textured surface on lubrication regime was studied. ► A novel multi-scale dimples were fabricated by LST by combining circles and ellipses. ► The beneficial effect of multi-scale dimples becomes higher with increasing dimple depth and sliding speed. ► The multi-scale texture dimples have important hydrodynamic lubrication effect.Laser surface texturing (LST) is a surface engineering process used to improve tribological characteristics of materials by creating patterned microstructures on the mechanical contact surface. In LST technology, a pulsated laser beam is used to create arranged dimples on surface by a material ablation process, which can improve load capacity, wear resistances, lubrication lifetime, and reduce friction coefficients. In the present study, the effect of multi-scale LST on lubricant regime was investigated. A pulsed Nd:YAG laser was applied on steel (AISI 52100) to create arranged dimples. To optimize the surface texturing effect on friction, multi-scale texture dimples with some specific formula arrays were fabricated by laser ablation process by combining circles and ellipses. The tribological testing of multi-scale textured surface was performed by a flat-on-flat unidirectional tribometer under lubrication, and the results compared with that of untextured surface. Through an increase in sliding speed and dimple depth the beneficial effect of multi-scale LST performance was achieved. The multi-scale textured surface had lower friction coefficient performance than the untextured surface due to hydrodynamic lubrication effect.

Keywords: Laser surface texture; AISI 52100 steel multi-scale texturing; Friction; Lubrication regime

A simple method for fabrication of filler-free stretchable polydimethylsiloxane surfaces by Jalal Bacharouche; Philippe Kunemann; Philippe Fioux; Marie-France Vallat; Jacques Lalevée; Joseph Hemmerlé; Vincent Roucoules (pp. 64-76).

Display Omitted► Changes in surface composition of polydimethylsiloxane surfaces were studied after argon plasma exposition. ► Aging processes were studied in different atmospheric conditions. ► Free radicals are created and the nature of these radicals has been highlight. ► Silyl radicals react with allyl groups of antagonist filler-free polydimethylsiloxane resin during the crosslinking step. ► A high interfacial resistance has been observed under elongation/retraction cycles.We propose a simple method to elaborate a filler-free stretchable PDMS surface strong enough to resist to successive elongation/retraction cycles even at high degree of stretching. It consists in creating free radicals on a filler-containing PDMS surface by argon plasma exposure and reacting them with a filler-free PDMS resin during the crosslinking step. Changes of physical and chemical properties upon plasma modification are monitored by FTIR and XPS spectroscopies, contact angle measurements and atomic force microscopy. Electron spin resonance (ESR) is used to identify the nature of radicals involved in interfacial bonding. Although a brittle silica-like layer is created on the filler-containing PDMS surface after plasma treatment, an increase in the PDMS/PDMS interfacial strength is observed and a high interfacial resistance has been found under elongation/retraction (stretching/relaxation) cycles.

Keywords: Polydimethysiloxane; Argon plasma; Surface modification; Free radicals; Interfacial strength

Ag₂SO₄ decorated with fluorescent Ag_n nanoclusters by Cheng Fang; Joseph George Shapter; Nicolas Hans Voelcker; Amanda Vera Ellis (pp. 77-81).

Microstructured fluorescent Ag₂SO₄ is synthesized via anodization of Ag foil in a HF-H₂SO₄ electrolyte. The residual Ag₂O is embedded in the Ag₂SO₄ deposit and photo-decomposed to fluorescent nanoclusters (Ag_n).Display Omitted► Ag foil was anodized in a HF-H₂SO₄ electrolyte to produce an Ag₂SO₄/Ag₂O mixed-grain powder. ► The photo-decomposed powder exhibited strong fluorescence. ► We proposed fluorescence arises from silver nanoclusters embedded with the Ag₂SO₄.Here we report on the production of an Ag₂SO₄/Ag₂O mixed-grain powder during the anodization of Ag foil in a HF-H₂SO₄ electrolyte. We propose that there are three competing reactions during the anodization process: (i) the production of Ag₂O at the Ag foil anode surface from the presence of water in the electrolyte, (ii) the dissolution of the Ag₂O in the presence of HF releasing Ag⁺ ions, (iii) the precipitation of Ag⁺ and SO₄²⁻ ions, as Ag₂SO₄ on the Ag foil anode surface. This co-precipitation/dissolution process ultimately results in a mixed-grain powder. We then show that the Ag₂O embedded within the mixed-grain is photo-decomposed to produce highly fluorescent silver nanoclusters (Ag_n) which decorate the Ag₂SO₄ crystals. The Ag₂SO₄ salt offers a stable matrix for the photo-decomposed Ag_n nanoclusters to emit their strong fluorescence.

Keywords: Electrochemistry; Silver sulphate/silver oxide mixed-grain powder; Silver nanoclusters; Fluorescence

Investigation of the effects of atomic oxygen exposure on the electrical and field emission properties of ZnO nanowires by C.X. Zhao; K. Huang; S.Z. Deng; N.S. Xu; Jun Chen (pp. 82-89).

► Effects of ozone exposure on the properties of ZnO nanowire were investigated. ► Changes in work function and resistivity of ZnO nanowires were examined. ► Electrical and field emission properties show close dependence on exposure dose. ► A better understanding concerning the effects of oxygen treatment was achieved.The effects of atomic oxygen exposure on electrical and field emission properties of ZnO nanowires were investigated. It was found that the turn-on field of ZnO nanowires increased after exposure to atomic oxygen. Measurement of electrical conductivity of single nanowire showed that the ozone exposure decreased the conductivity of the ZnO nanowire. Ultra-violet photoelectron spectroscopy results indicated that the ozone exposure increased the work function. Photoluminescence and X-ray photoelectron spectroscopy results suggested that ozone exposure reduced the oxygen vacancy concentration, which leads to the change in the work function and conductivity. We propose that the change of field emission properties is mainly caused by the changes in the surface work function.

Keywords: ZnO; Thermal oxidation; Field emission; ConductivityPACS; 61.72.uj; 64.75.Lm; 79.70.+q; 72.80.Ey

A XPS study of the Mo effect on passivation behaviors for highly controlled stainless steels in neutral and alkaline conditions by Thiago J. Mesquita; Eric Chauveau; Marc Mantel; Ricardo P. Nogueira (pp. 90-97).

► Laboratory stainless steels SS were tested. ► The presence of Mo oxides on the passive layer of all studied SS was confirmed by X-ray photoelectron spectroscopy (XPS). ► Mo improved the passivity breakdown potential for the duplex and ferritic SS but seemed to have no effect for austenitic SS in alkaline medium (pH 10).The objective of this work is to study the effect of Mo additions on film passive properties of three different stainless steels (SS) types (austenitic, ferritic and duplex alloys). A comparison between Mo containing (3wt% Mo) and free Mo (0wt% Mo) grades of highly controlled laboratory heats was done considering their passive film formed in different aggressive conditions, from neutral to alkaline pH. The presence of oxidized Mo on the passive layer was confirmed by X-ray photoelectron Spectroscopy (XPS). The presence of Mo within the passive film improved the passivity breakdown potential for the duplex and ferritic SS, but seemed to have no effect for austenitic SS.

Keywords: Stainless Steels; Molybdenum; Passive Layer; Corrosion

Robust technique allowing manufacturing superoleophobic surfaces by Edward Bormashenko; Roman Grynyov; Gilad Chaniel; Haim Taitelbaum; Yelena Bormashenko (pp. 98-103).

Display Omitted► Oleophobic surfaces prepared with low density polyethylene are reported. ► Tetrafluoromethane plasma treatment gives rise to hierarchical reliefs. ► Superoleophobicity is strengthened by the hydrophobic recovery. ► The stability of the Cassie wetting was studied.We report the robust technique allowing manufacturing of superhydrophobic and oleophobic (omniphobic) surfaces with industrial grade low density polyethylene. The reported process includes two stages: (1) hot embossing of polyethylene with micro-scaled steel gauzes; (2) treatment of embossed surfaces with cold radiofrequency plasma of tetrafluoromethane. The reported surfaces demonstrate not only pronounced superhydrophobicity but also superoleophobicity. Superoleophobicity results from the hierarchical nano-scaled topography of fluorinated polyethylene surface. The observed superoleophobicity is strengthened by the hydrophobic recovery. The stability of the Cassie wetting regime was studied.

Keywords: Superhydrophobicity; Superoleophobicity; Cold plasma treatment; Cassie wetting; Hydrophobic recovery

Crystalline nanostructured Cu doped ZnO thin films grown at room temperature by pulsed laser deposition technique and their characterization by Qasem A. Drmosh; Saleem G. Rao; Zain H. Yamani; Mohammed A. Gondal (pp. 104-108).

► Structural and optical properties of pure and Cu doped ZnO thin films. ► Crystalline thin films growth by PLD at room temperature without post annealing. ► Cu doping affect crystal structure, morphology, and optical properties of ZnO films. ► PL spectra revealed decrease in the band gap with the increase in Cu concentration.We report structural and optical properties of Cu doped ZnO (ZnO:Cu) thin films deposited on glass substrate at room temperature by pulsed laser deposition (PLD) method without pre and post annealing contrary to all previous reports. For preparation of (ZnO:Cu) composites pure Zn and Cu targets in special geometrical arrangements were exposed to 248nm radiations generated by KrF exciter laser. The laser energy was 200mJ with 10Hz frequency and 20ns pulse width. The effect of Cu concentration on crystal structure, morphology, and optical properties were investigated by XRD, FESEM and photoluminescence spectrometer respectively. A systematic shift in ZnO (002) peak with Cu concentration observed in XRD spectra demonstrated that Cu ion has been incorporated in ZnO lattice. Uniform film with narrow size range grains were observed in FESEM images. The photoluminescence (PL) spectra measured at room temperature revealed a systematic red shift in ZnO emission peak and decrease in the band gap with the increase in Cu concentration. These results entail that PLD technique can be realized to deposit high quality crystalline ZnO and ZnO:Cu thin films without pre and post heat treatment which is normally practiced worldwide for such structures.

Keywords: ZnO–Cu; Thin films; Pulsed laser deposition; Optical properties; Nanomaterials

Preparation of grass-like TiO₂ nanostructure thin films: Effect of growth temperature by A.A. Umar; M.Y.A. Rahman; S.K.M. Saad; M.M. Salleh; M. Oyama (pp. 109-114).

► Grass-like TiO₂ nanostructure films were prepared using liquid phase deposition method. ► The growth temperature used in synthesizing the TiO₂ nanoparticles samples were 25 (room temperature), 50, 60 and 90°C. ► The samples were in anatase form eventhough the morphology has changed. ► The optical absorption sensitivity and energy gap increase with the growth temperature.TiO₂ nanoparticles with various morphologies have been synthesized under various temperature conditions, namely 25, 50, 60 and 90°C via a liquid phase deposition technique. The liquid phase deposition technique is an electroless deposition of TiO₂ onto the substrate surface via a unique hydrolysis of titanium complexes in the presence of H₃BO₃. FESEM characterization on the samples showed that, under the temperature treatment, the nanostructures morphology transformed from grass-like to agglomerated spherical-like shape with the increased of the temperature. The XRD analysis performed on these samples show that all of the samples were anatase and unmodified with the change in the morphology. The optical absorption window of the TiO₂ nanostructures films was also found to enlarge with the increasing of the growth temperature, resulting from the structure modification. Owing to its simplicity, the present technique may produce TiO₂ nanoparticles with a variety of morphologies for use in photocatalyst and solar cell applications.

Keywords: Shape-controlled growth; Temperature effect; Liquid phase deposition (LPD); TiO; ₂

Investigation of H₂S separation from H₂S/CH₄ mixtures using functionalized and non-functionalized vertically aligned carbon nanotube membranes by Neda Gilani; Jafar Towfighi; Alimorad Rashidi; Toraj Mohammadi; Mohammad Reza Omidkhah; Ahmad Sadeghian (pp. 115-123).

Display Omitted► Vertically aligned carbon nanotubes synthesized in five AAO templates and characterized. It was found that the structures of CNTs grown in AAO substrates are different and depend on the geometry of AAO channels. ► Functionalized and non-functionalized CNT/AAO membranes were fabricated and characterized. ► Performance of functionalized and non-functionalized CNT/AAO membranes for separation of H₂S from binary mixtures of H₂S/CH₄ was investigated and compared. ► Selectivity of the CNT/AAO membrane was increased about 1.5–2.0 times after functionalization with dodecyleamine.Separation of H₂S from binary mixtures of H₂S/CH₄ using vertically aligned carbon nanotube membranes fabricated in anodic aluminum oxide (AAO) template was studied experimentally. Carbon nanotubes (CNTs) were grown in five AAO templates with different pore diameters using chemical vapor deposition, and CNT/AAO membranes with tubular carbon nanotube structure and open caps were selected for separation of H₂S. For this, two tubular CNT/AAO membranes were fabricated with the CNT inner diameters of 23 and 8nm. It was found that permeability and selectivity of the membrane with inner diameter of 23nm for CNT were independent of upstream feed pressure and H₂S feed concentration unlike that of CNT having an inner diameter of 8nm. Selectivity of these membranes for separation of H₂S was obtained in the ranges of 1.36–1.58 and 2.11–2.86, for CNTs with internal diameters of 23 and 8nm, respectively. In order to enhance the separation of H₂S from H₂S/CH₄ mixtures, dodecylamine was used to functionalize the CNT/AAO membrane with higher selectivity. The results showed that for amido-functionalized membrane, both upstream feed pressure and H₂S partial pressure in the feed significantly increased H₂S permeability, and selectivity for H₂S being in the range of 3.0–5.57 respectively.

Keywords: Carbon nanotube; Anodic aluminum oxide; Gas separation; H; ₂; S/CH; ₄; mixture; Amido-functionalization

Field emission from zinc oxide nanorod bundles grown on silicon nanoporous pillar array by Ling Li Wang; Shang Dong Gong; Li Hong Wu; Xin Jian Li (pp. 124-127).

Display Omitted► A ZnO nanorod bundle array was grown on silicon nanoporous pillar array (Si-NPA). ► The field-emission properties of ZnO/Si-NPA was studied. ► The turn-on field of ZnO/Si-NPA was 4.6V/μm, with a field enhancement factor of ∼1700. ► ZnO/Si-NPA might be a promising electron-emitting source.A large-area zinc oxide (ZnO) nanorod bundle array was grown on a silicon nanoporous pillar array (Si-NPA) substrate by a chemical vapor deposition method, and its field-emission properties was studied. The structural characterization disclosed that the bundles were composed of hexagonal ZnO nanorods growing along c-axis and taking roots into the silicon pillars of Si-NPA. The average diameter and length of the ZnO nanorods were ∼145nm and ∼10μm, respectively. The field-emission measurements showed that the turn-on field of ZnO/Si-NPA was 4.6V/μm with an emission current density (ECD) of 1μA/cm², and an ECD of 420μA/cm² was achieved at an applied field of 8.89V/μm. The field enhancement factor was calculated to be ∼1700 based on the Fowler–Nordheim theory. According to the obtained charge coupled device (CCD) image, the density and brightness of the emission dots increased with the applied field, and the high emission dot density was attributed to the formation of a large number of ZnO nanorod emitting tips. Our results indicated that ZnO/Si-NPA might be a promising electron emission source.

Keywords: Zinc oxide nanorod bundle; Silicon nanoporous pillar array; Field emission

Filling carbon nanotubes with Ni–Fe alloys via methylbenzene-oriented constant current electrodeposition for hydrazine electrocatalysis by Jia Wang; Zhengping Dong; Jingwei Huang; Jing Li; Xiaodong Jin; Jianrui Niu; Jian Sun; Jun Jin; Jiantai Ma (pp. 128-132).

The process for the preparation of the Ni–Fe alloys filled MWCNTs.Display Omitted► A novel method is presented to fill multiwalled carbon nanotubes with Ni–Fe alloys. ► The method is methylbenzene-oriented constant current electrodeposition. ► The method is based on the different conductivity of MWCNTs inside and outside. ► The process is simple, environment friendly and proceeds at low temperature. ► The Ni₈₅Fe₁₅-filled MWCNTs showed high electrocatalytic activity for hydrazine.A simple and novel method to fill carbon nanotubes (CNTs) with Ni–Fe alloys by methylbenzene-oriented constant current electrodeposition is demonstrated. The method is based on the difference in the surface conductivity of CNTs inside and outside in electrodeposition process owing to the covering of methylbenzene. The Ni–Fe alloys filled multiwalled carbon nanotubes (MWCNTs) were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and atomic absorption spectroscopy (AAS), respectively. Then the Ni–Fe alloys filled MWCNTs were used as hydrazine oxidation electrocatalysts in direct hydrazine (N₂H₄)-air fuel cells. Cyclic voltammograms (CVs) indicated that Ni₈₅Fe₁₅-filled MWCNTs had superior electrocatalytic activity for hydrazine electrocatalysis than catalysts with other compositions.

Keywords: Multiwalled carbon nanotubes; Ni–Fe alloys; Constant current electrodeposition; Methylbenzene; Hydrazine electrocatalysis

Cation exchange synthesis of ZnS–Ag₂S microspheric composites with enhanced photocatalytic activity by Hailin Zhang; Bo Wei; Lin Zhu; Jiahui Yu; Wenjun Sun; Lingling Xu (pp. 133-138).

► ZnS–Ag₂S composite microspheres were synthesized via a two-step hydrothermal method for the first time. ► Ag₂S deposition was resulted from cation exchange due to the large difference in solubility. ► AgNO₃ concentration had obvious effects on structure, microstucture and photocatalytic activity. ► Ag₂S modified ZnS composite showed greatly enhanced photocatalytic performance.In this study, we report controllable synthesis of ZnS–Ag₂S composite microspheres by the two-step hydrothermal method, which demonstrate excellent photocatalytic properties. Structure and morphology evolutions are investigated by adjusting the weight ratios of ZnS precursor and AgNO₃. Photocatalytic properties of the obtained samples are investigated by the photodegradation analysis of methylene orange (MO) dye. Surface modification of ZnS spheres by Ag₂S leads to highly enhanced photocatalytic activity, in comparison to pure ZnS. Furthermore, this method could be extended to prepare other sulfide based composite catalysts.

Keywords: ZnS; Ag; ₂; S; Cation exchange; Composite; Photocatalytic activity

Microstructural characterization of CIGS formation using different selenization processes by Kuang-Hsiang Liao; Cherng-Yuh Su; Yu-Ting Ding; Horng-Show Koo (pp. 139-144).

► CIGS thin films is strongly affected by the choice of the selenization process. ► Isothermal selenization resulted in the over-concentration of Se in the CIGS thin films. ► Two-zone selenization showed the poor crystallinity of CIGS with low Se concentration. ► Ga accumulation in large amounts in the films depends on the selenization temperature. ► The surface morphology of CIGS films is determined by the selenized extent of precursors.Cu(In1−_x,Ga_x)Se₂ (CIGS) thin films were prepared by the sputtering of CuInGa precursors followed by chalcogenization via an isothermal (one-zone) selenization and a two-zone selenization. The effects of two selenization processes on the microstructural characteristics of CIGS films were also studied. In addition, we varied the selenization temperature for the two processes between 450°C and 580°C to investigate this effect on the microstructural characteristics and compositions of the CIGS films. The results indicated that the CIGS thin films formed using isothermal selenization had dense grain structure whose grains increased in size after an increase in the selenized temperature. However, the Se/(Cu+In+Ga) ratios of the films indicated that Se was distributed non-uniformly in the films, with Se-saturated CIGS present on the front side of the films and incompletely formed CIGS on the back side. In addition, it was noticed that Ga accumulated in large amounts in the films, depending on the chemical affinity between In and Se. Comparatively, the films prepared using two-zone selenization showed Ga accumulation that was only slightly greater than that in the films fabricated by the isothermal selenization. It is likely that the slow selenization of the CIG precursors reduced the extent of Ga accumulation because of the presence of Se in insufficient amounts. However, the presence of Se in insufficient amounts may also format the CIGS thin films with a porous microstructure.

Keywords: CIGS thin films; Isothermal selenization; Two-zone selenization; Compositional variation

Cr atom diffusion in tribolayer T10 steel induced by dry sliding against 20CrMnTi steel by Xin Wang; Dandan Mao; Xicheng Wei; Wurong Wang (pp. 145-149).

Display OmittedThe ultrafine ferrite ranged from 5nm to 200nm of T10 steel pin was observed. ► The temperatures on contact surface are estimated by FEM from 395K to 499K. ► The Cr atoms originated from the disks diffused into the pins about 5–25μm. ► The diffusion activations of Cr atoms is 97.54kJ/mol. ► The atom diffusion is benefited from temperature rise and grain refinement.Compositions and microstructures of sliding friction induced deformation layer (SFIDL) of T10 steel pins against 20CrMnTi steel disks were studied by SIMS and TEM. It is found that Cr element in 20CrMnTi steel disk diffused into the SFIDL of T10 steel pin. Frictional contact temperature was analyzed by finite element method (FEM), which was in the range of 395–499K. The diffusion activation energy of Cr in the SFIDL of T10 steel is 97.54kJ/mol, which is much smaller than that in the coarse-grained Fe (241kJ/mol). The atomic diffusion phenomenon is thought to be the simultaneous and recursive actions of (i) grain refinement in the SFIDLs, (ii) temperature rise on the contact surfaces.

Keywords: Dry sliding friction; Tribolayer; Diffusion; Plastic deformation

Corrosion resistance of CrN thin films produced by dc magnetron sputtering by A. Ruden; E. Restrepo-Parra; A.U. Paladines; F. Sequeda (pp. 150-156).

► CrN structure depends on conditions as gases ratio, pressure of work and substrate. ► Low pressure would favor coatings corrosion resistance decreasing the porosity. ► CrN corrosion resistance is enhanced in substrates that contain high Cr percentage.In this study, the electrochemical behavior of chromium nitride (CrN) coatings deposited on two steel substrates, AISI 304 and AISI 1440, was investigated. The CrN coatings were prepared using a reactive d.c. magnetron sputtering deposition technique at two different pressures (P1=0.4Pa and P2=4Pa) with a mixture of N₂–Ar (1.5-10). The microstructure and crystallinity of the CrN coatings were investigated using X-ray diffraction. The aqueous corrosion behavior of the coatings was evaluated using two methods. The polarization resistance (Tafel curves) and electrochemical impedance spectra (EIS) in a saline (3.5% NaCl solution) environment were measured in terms of the open-circuit potentials and polarization resistance ( R_p). The results indicated that the CrN coatings present better corrosion resistance and R_p values than do the uncoated steel substrates, especially for the coatings produced on the AISI 304 substrates, which exhibited a strong enhancement in the corrosion resistance. Furthermore, better behavior was observed for the coatings produced at lower pressures (0.4Pa) than those grown at 4Pa.

Keywords: Corrosion; EIS; Pressure; Tafel curves; XRD

Cu induced morphology changes at Pb/Si (111) interface: Separation of “5×5”-Cu structure into individual domains by Pavel Shukrynau; Pingo Mutombo; Michael Hietschold; Vladimír Cháb (pp. 157-162).

► Deposition of copper onto Pb/Si (111) interface changes the original Pb–Si structures. ► New objects of hexagonal form appear on √3×√3R30°-Pb phase upon temperature treatment. ► Formation of the copper silicides below the inert Pb layer is assumed. ► The hexagonal objects are single domains of “5×5”-Cu phase separated by the border made of Pb atoms.The adsorption of small amount of Cu onto 1×1-Pb/Si (111) and √3×√3R30°-Pb/Si (111) coexisting phases was studied with variable temperature scanning tunnelling microscopy and spectroscopy. The most significant features connected with the deposition of copper at room temperature appeared as tiny clusters randomly scattered over smooth 1×1-Pb islands. Behaviour of the clusters at room at low temperature assumed that Cu penetrates through inert 1×1-Pb layer and mixes up with silicon. Moderate thermal treatment of (Cu, Pb)/Si (111) system induced the formation of shallow depressions of variable shape and size that are embedded into 1×1-Pb phase. Tunnelling spectra taken over a particular depression showed the peaks typical for the copper silicides. Moreover, the temperature rise causes the formation of large objects of distinctive hexagonal shape on neighbouring √3×√3R30°-Pb/Si (111) structure. Filled and empty state STM images of the hexagons differ strongly suggesting covalent bonding between constituent atoms. Detailed analysis of the hexagonal objects (and their agglomerates) reveals the specific features of quasi-commensurate 5×5-Cu structure.

Keywords: Scanning tunnelling microscopy; Copper; Lead; Silicon; Surface chemical reaction

Effect of annealing temperature on PL spectrum and surface morphology of zinc oxide thin films by A. Zendehnam; M. Mirzaee; S. Miri (pp. 163-168).

► ZnO thin films produced by thermal oxidation of Zn layers. ► Zn deposited on Si substrate by magnetron sputtering. ► Surface roughness and particle size increased with annealing temperature. ► Samples which were annealed at different temperatures seem suitable for tribological applications.Zinc oxide (ZnO) thin films were produced by thermal oxidation of Zn layers (200nm thickness) which were coated on Si (100) substrate by DC magnetron sputtering. In order to study the effect of annealing temperature on photoluminescence (PL) properties and the surface morphology of the ZnO samples, the annealing temperature range of 500–700°C was employed. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) for investigation of surface morphology of the ZnO samples were carried out. The surface statistical characteristics of these ZnO thin films are then evaluated against data which outcome from AFM. SEM and AFM results indicated that the annealing temperature produces larger grains and rough surfaces at higher temperatures. The results of PL spectra represent an increase in interstitial zinc with increasing annealing temperature.

Keywords: ZnO; Fractal analysis; Morphology; Annealing temperature; PL; AFM

Au/TiO₂ supported on ferritic stainless steel monoliths as CO oxidation catalysts by V.G. Milt; S. Ivanova; O. Sanz; M.I. Domínguez; A. Corrales; J.A. Odriozola; M.A. Centeno (pp. 169-177).

Display Omitted► Au nanoparticles supported on TiO₂ were coated over Aluchrom YHf monoliths. ► To favor the anchoring of the catalyst, metallic monoliths were previously calcined. ► The scale well adhered to the support was mainly composed of Al, Ti, Au, Ni and Mn. ► Ni and Mn enhanced the activity of Au/TiO₂ for the oxidation of CO.Metallic supported structured catalysts were obtained by washcoating AluchromYHf monoliths with an Au/TiO₂ catalyst. The powder catalyst was synthesized by DAE (direct anionic exchange) method. Using this catalyst, a stable slurry was prepared and used to washcoat the monoliths. TEM and SEM studies revealed that gold nanoparticles in the Au/TiO₂ powder catalyst had an average diameter of 3–4nm, but during the preparation of the structured catalyst, aggregate Au particles of the slurry reached diameters of 9nm. Before coating, Aluchrom YHf monoliths were thermally treated to generate a homogeneous and well-adhered oxide rough surface layer, mainly composed of α-Al₂O₃ whiskers, which favored the anchoring of the catalyst. The catalytic layer deposited was well attached and contained not only the Au/TiO₂ catalyst but also metallic oxides formed from stainless steel components that diffused through the oxide scale. The structural characterization was performed by XRD, XRF, TEM, SEM, GD-OES and S_BET.The catalytic activity of the powder and structured catalysts was tested in the oxidation of the CO reaction. Catalysts demonstrated to be active at room temperature. After a first activation run, and in spite of their larger gold particle size, the catalytic activities of the structured catalysts overcame those of the powder catalyst. This improvement is probably due to the segregation of the transition metal oxides toward the surface oxide scale.

Keywords: Structured catalysts; Au/TiO; ₂; CO oxidation; Metallic monoliths; Aluchrom YHf

Low-temperature synthesis of hexagonal transition metal ion doped ZnS nanoparticles by a simple colloidal method by Liping Wang; Shungang Huang; Yujie Sun (pp. 178-183).

► Hexagonal ZnS synthesized for the first time at low temperature. ► The synthesis temperature can be as low as 95°C. ► Sulfide source, surfactant, pH regulator, are crucial factors for the understanding of crystal structure. ► Possible reaction mechanism is discussed.A general route to synthesize transition metal ions doped ZnS nanoparticles with hexagonal phase by means of a conventional reverse micelle at a low temperature is developed. The synthesis involves N, N-dimethylformamide, Zn(AC)₂ solution, thiourea, ammonia, mercaptoacetic acid, as oil phase, water phase, sulfide source, pH regulator, and surfactant, respectively. Thiourea, ammonia and mercaptoacetic acid are demonstrated crucial factors, whose effects have been studied in detail. In addition, the FT-IR spectra suggest that mercaptoacetic acid may form complex chelates with Zn²⁺ in the preparation. In the case of Cu²⁺ as a doped ion, hexagonal ZnS:Cu²⁺ nanoparticles were synthesized at 95°C for the first time. The X-ray diffraction (XRD) and transmission electron microscope (TEM) measurements show that the ZnS:Cu²⁺ nanoparticles are polycrystalline and possess uniform particle size. The possible formation mechanism of the hexagonal doped ZnS is discussed.

Keywords: Doped ZnS; Nanoparticles; Semiconductor; Preparation

Study of behaviors of aluminum overlayers deposited on uranium via AES, EELS, and XPS by Kezhao Liu; Lizhu Luo; Wei Zhou; Jiangrong Yang; Hong Xiao; Zhanglian Hong; Hui Yang (pp. 184-189).

► Al overlayers on U were prepared by sputtering at room temperature. ► The behavior of Al/U interfaces was studied in situ by AES, EELS, and XPS. ► An island growth mode was proposed.Aluminum overlayers on uranium were prepared by sputtering at room temperature in an ultra-high vacuum chamber. The growth mode of aluminum overlayers and behaviors of the Al/U interface reaction were studied in situ by auger electron spectroscopy, electron energy loss spectroscopy, and X-ray photoelectron spectroscopy. The results suggested that the interdiffusion took place at the Al/U interface during the initial stage of deposition. The U4f spectra of the Al/U interface showed strong correlation satellites at binding energies of 380.4 and 392.7eV and plasma loss features at 404.2eV, respectively. The interactions between aluminum and uranium yielded the intermetallic compound of UAl_x, inducing the shift to a low binding energy for Al2p peaks. The results indicated that aluminum overlayers were formed on the uranium by sputtering in an island growth mode.

Keywords: Uranium; Aluminum overlayer; Auger electron spectroscopy; Electron energy loss spectroscopy; X-ray photoelectron spectroscopy; Growth mode

Various sized nanotubes on TiZr for antibacterial surfaces by Sabina Grigorescu; Camelia Ungureanu; Robin Kirchgeorg; Patrik Schmuki; Ioana Demetrescu (pp. 190-196).

► Nanotubes on TiZr alloy with various sized nanotubes produced by two step anodization. ► The TiO₂ nanotubes on TiZr have diameters between 20 and 70nm. ► Inhibition of the growth of E. coli bacteria was evaluated. ► Highest antibacterial behavior is observed for nanotubes with diameters of 20–30nm. ► The highest bacteria growth inhibition is for nanotubes with largest active surface.A two-step anodization of a Ti50Zr alloy results in a various sized nanotube oxide structures, which show an improved antibacterial activity. The nanotubes were formed in glycol with 15vol.% H₂O and 0.2M NH₄F by two-step anodization. The oxide layer grown during 2h was removed by sonication in deionized water and anodized again for 1h at the same conditions as in the first step. The removed layer acts as a nano-prepatterned surface, where higher ordered and open nanotubes can be achieved. The surface morphologies were analyzed by SEM and AFM, the surface wettability by contact angle measurements. The diameter and the length of the grown nanotubes are potential dependent between 20 and 100nm in diameter and 2.3 and 5.7μm in length, respectively. The antibacterial properties were evaluated in vitro on the formed nanotubes on the TiZr alloy against gram negative Escherichia coli bacteria. The E. coli (ATCC 8738) were cultured in a tube containing Luria Bertani medium at 37°C. The optical density was determined after 18h of incubation. In comparison, the smallest nanotubes exhibited the most efficient antibacterial behavior against E. coli bacterium. This suggests the use of small diameter nanotubes on TiZr for antimicrobial surface applications, which are susceptible for biofilms and microbial cultures.

Keywords: TiO; ₂; nanotubes; TiZr alloy; Antimicrobial

Effect of stationary femtosecond laser irradiation on substructures’ formation on a mold stainless steel surface by P. Bizi-bandoki; S. Valette; E. Audouard; S. Benayoun (pp. 197-204).

Nano-scale and micro-scale laser-induced periodic surface structures (ripples), pores and splash-like structures with different formation thresholds fluence have been observed after stationary multiple linearly polarized femtosecond laser irradiations on a molding stainless steel. Nano-scale structures exhibit a formation threshold fluence lower than that of micro-scale ripples. When increasing both power density and number of pulses, nano-scale ripples are only sensitive to the latter, showing a 15% decrease of their spatial period in the range of used values. Micro-scale ripples respond to these two laser parameters by an increase followed by a decrease of their spatial period. The two types of ripples exhibit behavior differences that show that micro- and nano-scale ripples are the results of two distinct mechanisms.

Keywords: Surface morphology; Ripples; Ripples formation threshold fluence; Pores; Splashes; Fluence regimes; Incubation; Femtosecond; Mold steel

A critical analysis of cation adsorption from single and binary solutions on low surface area β-MnO₂ by K. Rout; M. Mohapatra; S. Anand (pp. 205-218).

Display Omitted► A critical analysis of cation adsorption on low surface area β-MnO₂ is reported. ► Detailed characterization of cation loaded β-MnO₂ by XRD, FTIR, SEM and Raman spectroscopy. ► Red/blue shifts in Raman spectra of cation loaded β-MnO₂ at 636cm⁻¹ for Pb(II), Cu(II), Zn(II). ► Pb(II) showed an increase of ten fold loading capacity in Pb(II)–Cd(II) binary system. ► The complex behaviour of cation adsorption in binary system explained by Raman spectra.Generally it is advocated that high surface area materials are better adsorbents due to availability of more surface active sites. In the present study, potential of a low surface area (0.81m²/g) β-MnO₂ has been examined for removal of Pb(II), Cd(II), Cu(II) and Zn(II) ions from aqueous solutions. To understand the adsorption mechanism of cations the various techniques used include SEM, FTIR, XRD and Raman spectroscopy_. Inner or outer sphere complex formation was envisaged due to +ve/−ve shifts in FTIR bands. Raman spectra showed shifting of band (red/blue shift) at 636cm⁻¹ (A_1g symmetric mode) for all the cations except Cd(II). Another important observation made was the decrease in scattering intensity of A_1g symmetric mode after cation adsorption except for Pb(II) loaded β-MnO₂. This was attributed to the breakdown of long-range translational crystal symmetry caused by the incorporated defects. Results for adsorption on β-MnO₂ from binary solutions namely Pb(II)–Cd(II), Pb(II)–Cu(II), Pb(II)–Zn(II), Cd(II)–Cu(II), Cd(II)–Zn(II) and Cu(II)–Zn(II) are discussed. Pb(II) having a low adsorption capacity of only 26mg/g showed tenfold increase in presence of Cd(II). The concentration dependent selectivity of certain cations in binary system has been explained on the basis of observed changes in the Raman spectra of loaded β-MnO₂.

Keywords: β-MnO; ₂; Raman spectra; Adsorption; Cations; Binary solutions

Liquid polycarbosilane derived SiC coating on silicon (111) wafer for enhanced mechanical properties by Jonaki Mukherjee; Ashok Ranjan; A.K. Saxena; Probal Kumar Das; Rajat Banerjee (pp. 219-224).

► Deposition of SiC film from polycarbosilane precursor by modified CVD method. ► Polymer to ceramics conversion at moderate temperature of 800, 900 and 1000°C. ► Formation of β-SiC and α-SiC films on silicon (111) wafer at moderate temperatures. ► Enhanced hardness(18GPa), toughness of coated samples than that of uncoated sample. ► Promising material for MEMS application.Silicon carbide coating on silicon (111) wafer was deposited by modified chemical vapor deposition (CVD) method using liquid polycarbosilane (LPCS) as precursor at three different moderately high temperatures in presence of Argon gas. Glancing angle X-ray diffractometer and Fourier Transform Infrared Spectroscopy reveals smooth β-SiC coating and its subsequent transformation into α-SiC on silicon substrate. In all the temperature the film was found to be uniform with a thickness ranging from 0.6–1.2μm. The average particle size as can be seen from FESEM ranges from 7 to 385nm approximately, the lowest range being (7–20nm) which hitherto has not yet been reported using LPCS as precursor for SiC. Moreover the coated samples show substantial increment of hardness (∼18.8GPa) and toughness (∼1.51MPam^1/2), both of which increases with increase in deposition temperature. The smooth and thin SiC coating on silicon formed in three different moderate temperatures compared to very high temperature for other CVD assisted coating along with enhanced hardness and toughness makes this a promising material in critically harsh environment required for microelectromechanical systems (MEMS) application.

Keywords: Precursors-organic; Hardness; SiC; Liquid PCS; Mechanical properties

Enhancement of piezoelectric response of diluted Ta doped AlN by Hongyan Liu; Fei Zeng; Guangsheng Tang; Feng Pan (pp. 225-230).

► Highly c-axis oriented Ta:AlN films were deposited on Si(100) substrate using DC magnetron reactive sputtering at 400°C. ► A large enhancement of piezoelectric response with piezoelectric coefficient of 8.2pC/N was obtained. ► The mechanism of the large enhancement in piezoelectric response is supposed to be enhancement of internal nitrogen displacement under electric field.The authors have investigated the variation of microstructure and piezoelectric response of Ta_xAl1−_xN films with Ta concentrations. The results indicate that moderate Ta doping facilitates the c-axis orientation, crystallinity and enlargement of lattice constants. When the doping content is about 5.1at.%, the c-axis orientation is optimized in the best with c constant of about 0.5086nm. The Raman spectra of Ta_xAl1−_xN films further determine the wurtzite structure of AlN after Ta doping. The high resolution transmission electric microscopy demonstrates that the column single crystal was obtained with presence of nano distortion domains. The Ta 4 f_7/2 binding energy of Ta_xAl1−_xN shows a shift toward lower binding energy side, indicating that the coordination configuration of Ta with N changed as Ta contents increased. A significant enhancement in piezoelectric response was obtained from 4.2pC/N to 8.2pC/N, which is enhanced by ca. 100%, when the Ta content arrived to 5.1at.%. The expansion of unit cell volume and the competition between Ta and Al atoms about the coordination of nitrogen atoms, which will enhance the internal nitrogen displacement under electric field, are proposed to be the main microscopic origin of the enhancement of piezoelectric response.

Keywords: Piezoelectric response; Ta; AlN

Low-temperature oxidation of alkali overlayers: Ionic species and reaction kinetics by David Krix; Hermann Nienhaus (pp. 231-237).

► Comprehensive XPS study of low-temperature oxidation of all five, equally prepared alkali metal films. ► Unambiguous identification of atomic and molecular oxide species by O 1 s core-level spectroscopy. ► Determination of the kinetics and the degree of dissociation of the oxidation. ► Demonstrating a clear chemical trend in the core-level shifts. ► Proof that XPS allows the identification of the oxide species.Clean and oxidized alkali metal films have been studied using X-ray photoelectron spectroscopy (XPS). Thin films, typically 10nm thick, of lithium, sodium, potassium, rubidium and cesium have been deposited on silicon substrates and oxidized at 120K. Plasmon losses were found to dress the primary photo emission structures of the metals’ core lines which confirms the metallic, bulk like nature of the films. The emission from the O 1 s core levels was used to determine the chemical composition and the reaction kinetics during the exposure to molecular oxygen at low pressures. Molecular oxide ionsO2− andO22− as well as atomic oxygen ions O²⁻ were detected in varying amounts depending on the alkali metal used. Diffusive transport of material in the film is shown to greatly determine the composition of the oxides. Especially, the growth of potassium superoxide is explained by the diffusion of potassium atoms to the surface and growth at the surface in a Deal–Grove like model.

Keywords: Sodium; Potassium; Rubidium; Cesium; Silicon; Oxygen; Oxidation

Hydrothermal synthesis of single-walled carbon nanotube–TiO₂ hybrid and its photocatalytic activity by Ke Dai; Xiaohu Zhang; Ke Fan; Tianyou Peng; Bingqing Wei (pp. 238-244).

► SWCNT–TiO₂ was hydrothermally prepared via direct growth of TiO₂ on SWCNTs. ► Well-dispersed SWCNTs inhibit growth of TiO₂ and improve its thermal stability. ► The photoactivity of TiO₂ was enhanced significantly with SWCNT introduction.A single-walled carbon nanotube (SWCNT)–TiO₂ hybrid was prepared hydrothermally by direct growth of TiO₂ nanoparticles on the surface of functionalized SWCNTs to develop highly efficient photocatalysts. The SWCNT–TiO₂ hybrid was characterized by X-ray diffraction, electron microscopy, N₂-adsorption analysis, FT-IR, Raman, and UV–vis spectroscopy. The photocatalytic activity of the SWCNT–TiO₂ hybrid was examined by the photocatalytic degradation of pirimicarb. Although the SWCNT–TiO₂ hybrid exhibits no visible-light-induced activity, the photocatalytic degradation efficiency of pirimicarb over TiO₂ can be increased significantly with the introduction of SWCNTs (2–3 times) because SWCNTs can act as electron conductors that hinder the recombination of photo-generated electrons and holes. Compared with a multi-walled carbon nanotube–TiO₂ hybrid, it can be found that the electronic configurations of carbon nanotubes significantly affect the photocatalytic activity of carbon nanotube–TiO₂ hybrid. Metal-typed SWCNTs act more as an electrical conductor than a photosensitizer, which efficiently suppress charge recombination, improve interfacial charge transfer, and improve the photoactivity.

Keywords: Single-walled carbon nanotubes; TiO; ₂; Hybrid; Photocatalytic activity; Pirimicarb

Preparation and photocatalytic activity of cuprous oxide/carbon nanofibres composite films by Yuanqian Wang; Lin Liu; Yurong Cai; Jianjun Chen; Juming Yao (pp. 245-251).

Display Omitted► A series of Cu₂O nanocrystal loaded on the carbon nanofibers (CNFs) from nanoparticle to cubic, flower-like particle assembled by Cu₂O nanocubes with the change of the reaction conditions and all of these Cu₂O/CNFs composite films showed the satisfied photocatalytic activity due to the protectable function of CNFs to the Cu₂O nanocrystals.Cuprous oxide (Cu₂O) nanocrystals have been successfully synthesized using copper acetate as precursors via a polyol process. The as-synthesized products were easily deposited on the surface of carbon nanofibres (CNFs) and then were characterized through XRD, FESEM, TEM and FTIR, etc. The photocatalytic performance of these composite films was evaluated using methyl orange as a model organic compound under visible light irradiation. Results showed that the shape of Cu₂O nanparticles could be changed from irregular nanoparticle to cubic, flower-like particle assembled by Cu₂O nanocubes with the change of the reaction conditions. All of these Cu₂O/CNFs composite films showed the satisfied photocatalytic activity to methyl orange even after 3 cycles of degradation experiment due to the protectable function of carbon fibre films to the Cu₂O nanocrystals. The Cu₂O/CNFs composite films may offer a feasible method for the potential application of Cu₂O nanocrystals in the treatment of organic contamination.

Keywords: Cuprous oxide; Carbon nanofibres; Composite films; Photocatalytic

Electrodeposition of PdCu alloy and its application in methanol electro-oxidation by Ming-Wei Hsieh; Thou-Jen Whang (pp. 252-259).

Display Omitted► We added triethanolamine (TEA) into the Pd²⁺ and Cu²⁺ mixed-ion electroplating bath to obtain a Pd-rich PdCu alloy. ► XRD analysis verified that PdCu alloys have smaller particle sizes compared with those deposited in TEA-free solutions. ► The cyclic voltammetry showed that alloys deposited with TEA have higher hydrogen desorption areas. ► Surface-modified PdCu alloys via redox replacement displayed the beneficial of Cu underpotential deposition. ► PdCu alloys fabricated with TEA and redox replacement showed better catalytic performance in the methanol electro-oxidation.This study demonstrates a simple electrodeposition method to fabricate the palladium–copper alloy on an ITO coated glass (PdCu/ITO) and its application in methanol electro-oxidation. Our approaches involve the co-reduction of Pd and Cu using triethanolamine (TEA) as a complexing agent in the electroplating bath and a Pd redox replacement of Cu on the surface of the as-prepared PdCu alloy. The phase structures, alloy compositions and morphologies of catalysts are determined by X-ray diffraction, energy dispersive spectrometer and scanning electron microscopy, respectively. X-ray diffraction shows that the particle size of PdCu deposits shrink when the alloy is deposited in a TEA-contained solution. The electrocatalytic properties of PdCu alloys and Pd redox replacement modified PdCu alloys for methanol oxidation have been investigated by cyclic voltammetry. The PdCu alloy with atomic ratio of 20.5% Cu exhibits higher catalytic activity toward methanol oxidation compared with a pure Pd catalyst. PdCu alloys with smaller particle sizes associated with TEA agent and the surface confined Pd replacement are found to have enhanced catalytic performance in the electro-oxidation of methanol.

Keywords: Electrodeposition; PdCu alloy; Redox replacement; Methanol oxidation

Ultrahydrophobicity of ZnO modified CVD diamond films by YiZhou Yang; ChuanXi Wang; HongDong Li; Quan Lin (pp. 260-266).

► We report the deposition of ZnO layer on diamond film by RF magnetron sputtering method. ► The water contact angle of ZnO-modified diamond surface can be reached as high as ∼141°. ► The influence of roughness of hydrophobic proposed by different processing are analyzed. ► A theoretical model is given to explain the phenomenon observed.Chemical vapor deposited (CVD) polycrystalline diamond films with an ultrahydrophobic surface were fabricated by constructing a hierarchical structure through sputtering a ZnO layer on diamond grains, with a growth step feature. Under optimized conditions, the combined original diamond with a step structure of the ZnO can achieve a water contact angle (WCA) of as high as 141°±1°. It is proved that WCA decreases as the roughness of ZnO/PDF reduced. It can be concluded that the step structure of diamond grains and ZnO nuclei size have a great influence on the variation of WCA.

Keywords: Ultrahydrophobicity; Freestanding polycrystalline CVD diamond; ZnO thin films

Enhanced photoelectrochemical performance of WO₃/Ti photoanode due to in situ formation of a thin interfacial composite layer by Won Jae Lee; Pravin S. Shinde; Geun Ho Go; Chil Hoon Doh (pp. 267-271).

► Nanocrystalline monoclinic WO₃ films are grown on treated Ti substrates using doctor-blade method. ► Photoelectrochemical response of WO₃ on polished Ti is enhanced relative to that on unpolished Ti substrate. ► Photocurrent enhancement is attributed to in situ formation of an interfacial WO_x–TiO_y layer between WO₃ and polished Ti. ► WO_x–TiO_y layer promotes the charge separation and improves the interfacial charge-transfer processes.Nanostructured WO₃ thin films were prepared on titanium sheet substrates using a doctor blade technique. X-ray diffraction, Raman and field emission scanning electron microscopy studies revealed that the synthesized WO₃ films are having monoclinic crystal structure, porous, polycrystalline with average grain size of ∼50nm. The photoelectrochemical responses of WO₃ films prepared on treated Ti sheets were recorded in 0.5M H₂SO₄ electrolyte under simulated 100mW/cm² illumination. WO₃ film prepared on polished Ti sheet showed considerable enhancement in photocurrent as compared to WO₃ films made on unpolished and pre-oxidized Ti sheets. These results suggest that in situ formation of a thin WO_x–TiO_y interfacial composite layer and improved adhesion of WO₃ nanoparticles owing to increased reactive sites on polished Ti substrate play a significant role in enhancing the photoresponse. Such photoanodes are potential candidates in photoelectrochemical water splitting system for hydrogen generation.

Keywords: WO; ₃; /Ti thin films; Photoanode; Water splitting; Photoelectrochemical

Effect of UV and electrochemical surface treatments on the adsorption and reaction of linear alcohols on non-porous carbon fibre by S. Osbeck; S. Ward; H. Idriss (pp. 272-280).

Display Omitted► Treatment of fibre carbon with UV/O₃ results in functionalisation of its surface. ► Increasing the surface oxygen content increases the surface coverage of alcohols. ► UV/O₃ treatment resulted in three orders of magnitudes increase of surface coverage.The adsorption properties of untreated, electrochemically treated and ultra-violet/ozone treated polyacrylonitrile based carbon fibres were investigated using temperature programmed desorption (TPD) on a series of linear alcohols as probes in order to understand its surface properties. Surface uptake was found to be sensitive to both the surface treatment and the nature of the adsorbates. Surface coverage increased with increasing alcohol chain due to the increase in their polarizability. It also increased with the level of surface oxygen of the fibres most likely because it facilitates the OH bond dissociation of the alcohol functional group. In addition, the desorption temperature (during TPD) tracked the surface oxygen levels (as determined from XPS O1s signal) suggesting increasing in the adsorption energy. The reactions of C1–C4 linear alcohols were also investigated on the surface of the fibre carbon. The main reaction was dehydrogenation to the corresponding aldehydes; the dehydration reaction to olefins was not observed. The dehydrogenation reaction was sensitive to the length of the alky chain. It was highest for methanol (to formaldehyde) and decreased with increasing the carbon number. Overall TPD of linear alcohols was shown to be a promising method for quantifying the level and strength of bonding occurring on carbon fibre surfaces.

Keywords: Fibre carbon surface; UV/O; ₃; treatment; Temperature programmed desorption; Linear alcohols reaction; Dehydrogenation and dehydration reactions

Investigation on bend displacement and surface quality induced by laser shock micro-adjustment by Chunxing Gu; Zongbao Shen; Huixia Liu; Pin Li; Mengmeng Lu; Qiang Zhang; Xiao Wang (pp. 281-286).

► Laser shock micro-adjustment is a new adjustment technique. ► Laser shock wave can reduce the average surface roughness. ► The bend displacement and crater depth are studied under this adjustment method.Laser shock micro-adjustment is a new adjustment technique using laser-shock-waves to adjust the curvature of micro-components (micro-mechanical cantilevers). A full empirical study has been conducted, with the effects of laser energy, laser shock region and sample thickness investigated. And, the influences of laser processing parameters on the surface qualities are also taken into consideration and investigated. According to the result, compared with the surface roughness in the shock and un-shock regions, it can be found that the average surface roughness ( R_a) of adjustment surface is lower than that of other un-shock surface, implying the surface quality would be upgraded via the shock micro-adjustment processing. A fine surface quality can be obtained by means of adjusting the laser parameters and the thickness of coating, as well as other process details. Such a technique is simple to implement, yet very useful for applications involving adjustment of micro-components in the field of MEMS.

Keywords: Laser shock micro-adjustment; Curvature adjustment; Surface quality; Surface roughness

Hydrogenated amorphous silicon-carbide thin films with high photo-sensitivity prepared by layer-by-layer hydrogen annealing technique by S.X. Li; Y.Q. Cao; J. Xu; Y.J. Rui; W. Li; K.J. Chen (pp. 287-291).

► a-SiC:H films were prepared by layer-by-layer hydrogen plasma annealing technique. ► The electrical and optical properties of prepared films were studied. ► Photo-conductivity was improved after hydrogen plasma annealing. ► High photo-sensitivity (∼10⁶) was achieved for 10s layer-by-layer annealed film.Hydrogenated amorphous silicon carbide thin films with high photo-sensitivity were fabricated by using layer-by-layer hydrogen annealing technique in conventional plasma enhanced chemical vapor deposition system. It was found that the photo-conductivity is increased from 1.9×10⁻⁷ to 1.5×10⁻⁶S/cm after layer-by-layer hydrogen annealing. The photo-sensitivity can reach as high as 10⁶ for sample with optical band gap of 2.11eV. The influence of the hydrogen annealing time on film quality and optical properties were investigated. It was demonstrated that the layer-by-layer hydrogen annealing technique can improve the film quality, which can be attributed to both the hydrogen chemical annealing and hydrogen passivation effect.

Keywords: Amorphous silicon-carbide; Photo-conductivity; Layer-by-layer hydrogen annealing

Self-assembly Ag nanoparticle monolayer film as SERS Substrate for pesticide detection by Li Zhang (pp. 292-294).

Display Omitted► A simple self-assembled method was used to fabricate ordered Ag nanosized film. ► The assembled ordered Ag nanosized film was monolayer, and the ordered film with large area. ► The assembled monolayer film with excellent Raman enhancement and reproducibility, which has been used to detect pesticide.A self-assembled protocol is introduced to provide effective platforms for the fabrication of ordered Ag nanosized monolayer film. The assembled Ag nanosized monolayer film was characterized using scanning electronic microscopy and surface-enhanced Raman scattering (SERS). The results show that the assembled SERS substrate own excellent Raman enhancement and reproducibility. The synthesized SERS-active substrate was further used to detect methyl-parathion, and the limitation of detection can reach 10⁻⁷M.

Keywords: Self-assembly; SERS; Ag nanoparticle; Methyl-parathion

Engineering the size and density of silicon agglomerates by controlling the initial surface carbonated contamination by Ł. Borowik; N. Chevalier; D. Mariolle; E. Martinez; F. Bertin; A. Chabli; J.–C. Barbé (pp. 295-300).

Display Omitted► New method to control size and surface density of the Si agglomerates. ► We influence the dewetting by the deposition carbon layer. ► Thickness of carbon layer is controlled by scanning electron microscopy irradiation. ► We induce alternative dewetting mechanism for the case of strained silicon film.Actually, thermally induced thin-films dewetting silicon in the silicon-on-insulator is a way to obtain silicon agglomerates with a size and a density fixed by the silicon film thickness. In this paper we report a new method to monitor both the size and the density of the Si agglomerates thanks to the deposition of a carbon-like layer. We show that using a 5-nm thick layer of silicon and additional ≤1-nm carbonated layer; we obtain agglomerates sizes ranging from 35nm to 60nm with respectively an agglomerate density ranging from 38μm⁻² to 18μm⁻². Additionally, for the case of strained silicon films an alternative dewetting mechanism can be induced by monitoring the chemical composition of the sample surface.

Keywords: Dewetting; Density control; Size control; UHV annealing; SEM irradiation; Carbonated contamination

Growth of 4H-SiC epilayers with low surface roughness and morphological defects density on 4° off-axis substrates by Lin Dong; Guosheng Sun; Jun Yu; Liu Zheng; Xingfang Liu; Feng Zhang; Guoguo Yan; Xiguang Li; Zhanguo Wang (pp. 301-306).

Display Omitted► We presented the results on surface roughness and morphological defects of 4H-SiC epilayers on 4° off-axis substrates with 100mm diameter. ► The impacts of the etch processes on the surface roughness of substrates and grown epilayers were shown. ► Smooth epilayer surfaces without step-bunching were obtained by optimizing etch processes. ► The increase in the Cl/Si ratio was demonstrated to effectively suppress the morphological defects on the epilayers with smooth surfaces. ► We can obtain the total morphological defects density lower than 1cm⁻² on 4H-SiC epilayers with roughness of 0.2nm.In situ etching and epitaxial growth have been performed on 4H-SiC 4° off-axis substrates with 100mm diameter. In situ etching process optimizations lead to obtain step-bunching free epilayer surfaces with roughnesses of 0.2nm and 0.8nm, which were grown on the substrates with and without chemical mechanical polishing, respectively. Yet the epilayer surfaces free of step-bunching are more likely to suffer from various types of morphological defects than the ones with step-bunching. An increase in chlorine/silicon ratio during epitaxy can effectively suppress the appearance of defects on the step-bunching free epilayer surfaces. Using optimized epitaxial processes, we can obtain the total morphological defects density lower than 1cm⁻² on 4H-SiC epilayers with surface roughness of 0.2nm.

Keywords: 4H-SiC; 4° off-axis; Surface roughness; Morphological defects; Etching; Epitaxial growth

Structural characterization of nanoparticles-assembled titanium dioxide films produced by ultrafast laser ablation and deposition in background oxygen by S. Amoruso; S. Tuzi; D.K. Pallotti; C. Aruta; R. Bruzzese; F. Chiarella; R. Fittipaldi; S. Lettieri; P. Maddalena; A. Sambri; A. Vecchione; X. Wang (pp. 307-311).

► Ultrafast laser ablation of titanium dioxide. ► Elaboration of titanium dioxide nanostructures by femtosecond pulsed laser deposition. ► Structural and morphological variation of TiO₂ nanoparticles-assembled films with oxygen pressure in femtosecond pulsed laser deposition. ► Changes of nanoparticles-assembled titanium dioxide films by annealing treatments.Ultrafast laser ablation of titanium dioxide and deposition of nanoparticles-assembled films in oxygen ambient gas at pressures going from high-vacuum up to several mbar is investigated. We identify various regimes of the plumes propagation into the background gas as well as of the material deposition rate. These reflect on the structural characteristics of the nanoparticles-assembled films: the film morphology changes from a structure with glue-like nanoparticulates, at low pressure, to a highly porous assembly of individual nanoparticles, at larger pressure. Our findings indicate that background gas pressure provides an interesting key for additional control on the structural characteristics of oxide nanostructures produced by femtosecond laser deposition.

Keywords: PACS; 52.38.Mf; 79.20.Eb; 81.07.−bUltrafast pulsed laser ablation and deposition of oxides; Titanium dioxide; Nanoparticles-assembled films

A new precursor strategy to prepare ZnCo₂O₄ nanorods and their excellent catalytic activity for thermal decomposition of ammonium perchlorate by Zhigang Jia; Daping Ren; Qiuze Wang; Rongsun Zhu (pp. 312-318).

Display Omitted► ZnCo₂(C₂O₄)₃·6H₂O nanorods are prepared by eco-friendly method. ► The solvent is pivotal for 1D growth of ZnCo₂(C₂O₄)₃·6H₂O nanorods. ► ZnCo₂(C₂O₄)₃·6H₂O nanorods convert to 1D ZnCo₂O₄ nanostructures. ► ZnCo₂O₄ nanorods show excellent catalytic activity to the decomposition of AP.We present a new preparation of zinc cobaltite (ZnCo₂O₄) nanorods via a hydrothermal-annealing method. Zinc cobalt oxalate (ZnCo₂(C₂O₄)₃·6H₂O) nanorods as the precursor have been firstly synthesized by solvothermal method at 120°C using the mixed solvents as the reaction medium without the assistance of soft/hard template. It is found that the mixed solvent plays an important role for zinc cobalt oxalate precursor nanorods and 1D growth of zinc cobalt oxalate precursor is gradually improved with the increasing ethylene glycol (EG) in the mixed solvent. The as-prepared zinc cobalt oxalate precursor (ZnCo₂(C₂O₄)₃·6H₂O) nanorods can convert to 1D zinc cobaltite (ZnCo₂O₄) nanostructures while maintaining original frame structure. The obtained samples are characterized by means of XRD, SEM, TEM and HRTEM. Furthermore, the effect of zinc cobaltite (ZnCo₂O₄) nanostructures on the thermal decomposition of ammonium perchlorate (AP) is investigated by differential thermal analysis (DTA). The results show that the addition of zinc cobaltite (ZnCo₂O₄) nanorods to AP remarkably decreases the decomposition temperature. The as-prepared zinc cobaltite (ZnCo₂O₄) nanorods are promising as a high-performing ballistic modifier in AP-based composite solid rocket propellants.

Keywords: Oxalate; Morphology; Metal oxide; Thermal decomposition; Nanostructure

In situ preparation of high dielectric constant, low-loss ferroelectric BaTiO₃ films on Si at 500°C by Meiling Yuan; Wei Zhang; Xianyang Wang; Wei Pan; Li Wang; Jun Ouyang (pp. 319-323).

► BaTiO₃ films were prepared on (100) Si substrates @ 500°C by rf magnetron sputtering. ► The effects of gas pressure and target power on the property of BaTiO₃ were studied. ► Under high target power, ferroelectric BaTiO₃ films were obtained without annealing. ► These ferroelectric films showed a (001) texture and a smooth surface with Ra∼1.7nm. ► These films showed good ferroelectric and dielectric properties at room temperature.In an attempt to build a CMOS-compatible process with reduced thermal budget for the integration of barium titanate ferroelectric films into Si-based MEMS and IC devices, BaTiO₃ films were prepared on Pt/Ti/(100) Si substrate at 500°C by a rf magnetron sputtering process without a post-growth annealing. Effects of substrate temperature, gas composition, gas pressure and target power on the microstructure of these films were analyzed in details. The BaTiO₃ films deposited under the conditions of 500°C substrate temperature, 120W target power and 0.3Pa gas pressure with a 4:1 Ar/O₂ flow ratio displayed good ferroelectric and dielectric properties. The microstructure analysis by XRD and AFM indicated that these BaTiO₃ films were polycrystalline with a preferred (001) orientation and a smooth surface with a Ra∼1.7nm. The twice remnant polarization 2Pr was 10.9μC/cm² @ 1kHz, while the relative dielectric constant and dielectric loss tangent were measured to be 720/0.042 @ 1kHz, and 360/0.038 @ 1MHz, respectively.

Keywords: BaTiO; ₃; Ferroelectric film; Magnetron sputtering; Si; CMOS-compatible

Effect of CH₄ concentration on the growth behavior, structure, and transparent properties of ultrananocrystalline diamond films synthesized by focused microwave Ar/CH₄/H₂ plasma jets by Wen-Hsiang Liao; Chii-Ruey Lin; Da-Hua Wei (pp. 324-330).

► Effects of CH₄ concentration on growth and properties of UNCD films were studied. ► Nanodiamond films transformed from UNCD to NCD by increasing CH₄ concentration. ► Grain size and nondiamond contents in nanodiamond films concurrently increased. ► Modification of UNCD films was reconfirmed by transmittance studies.The effects of CH₄ concentration (0.5–5%) on the growth mechanisms, nanostructures, and optically transparent properties of ultrananocrystalline diamond (UNCD) films grown from focused microwave Ar/CH₄/H₂ (argon-rich) plasma jets were systematically studied. The research results indicated that the grain size and surface roughness of the diamond films increased with increasing CH₄ concentration in the plasma jet, however, the nondiamond contents in films would not be correspondingly decreased resulting from the dispersed diamond nanocrystallites in the films synthesized at higher CH₄ concentration. The reason is due to that the relative emission intensity ratios of the C₂/H_α and the CH/C₂ in the plasma jets were increased and decreased with increasing CH₄ concentration, respectively, to lower the etching of nondiamond phase and the renucleation of diamond during synthesis. The studies of transmission electron microscopy demonstrated that, while the CH₄ introduction of 1% into the plasma jet produced the UNCD films with a spherical geometry (4–8nm) and the CH₄ introduction of 5% into the plasma jet led to the elongated (∼90nm in length and ∼35nm in width) grains in the nanocrystalline diamond (NCD) films with a dendrite-like geometry. The transmittance of diamond films was decreased gradually by films transition from UNCD to NCD, resulting from the enhanced surface roughness and nondiamond contents in films to concurrently increase the light scattering and absorption during photon transmission.

Keywords: Ultrananocrystalline diamond films; Focused microwave plasma jet; CH; ₄; concentration; Transmission electron microscopy; Transmittance

Conversion of Y₃(Al,Ga)₅O₁₂:Tb³⁺ to Y₂Si₂O₇:Tb³⁺ thin film by annealing at higher temperatures by A. Yousif; H.C. Swart; O.M. Ntwaeaborwa; E. Coetsee (pp. 331-339).

Display Omitted► Y₃(Al,Ga)₅O₁₂:Tb thin films were grown on Si(100) substrates. ► Y₃(Al,Ga)₅O₁₂:Tb thin film was converted to Y₂Si₂O₇:Tb due to Si interdiffusion at high temperature annealing. ► The presence of different types of traps resulting from the change on the structure of the thin films was monitored with thermoluminescence. ► The excitation and the emission bands changed due to new compound formation.Y₃(Al,Ga)₅O₁₂:Tb thin films were grown on Si(100) substrates in an Ar working atmosphere by using the pulsed laser deposition (PLD) technique. The Y₃(Al,Ga)₅O₁₂:Tb target was ablation deposited onto a Si(100) substrate using a 266nm Nd:YAG laser. The influence of post deposition annealing temperature (1073K to 1473K) on the excitation and the emission bands, and the crystal structure of the thin film were monitored. X-ray diffraction (XRD) and photoelectron spectroscopy (XPS) depth profiles of the thin films indicate that there were annealing induced changes in the crystal structure and chemical composition causing changes in the excitation bands. These changes (structure and composition) are attributed to interdiffusion of atomic species between the substrate and the Y₃(Al,Ga)₅O₁₂:Tb³⁺ thin film. The XRD and XPS data confirm that after annealing, Y₃(Al,Ga)₅O₁₂:Tb³⁺ was converted to Y₂Si₂O₇:Tb³⁺. A change in the relative ratios of the excitation band intensities was measured. Atomic force microscopy (AFM) showed that topographical changes also occurred during the annealing process. Thermoluminescence (TL) glow curves of the Y₃(Al,Ga)₅O₁₂:Tb³⁺ thin films before and after annealing, indicated the presence of different types of traps resulting from the change on the structure of the thin films.

Keywords: PLD; Y; ₃; (Al,Ga); ₅; O; ₁₂; :Tb; Y; ₂; Si; ₂; O; ₇; :Tb; Thin films; Defect trap levels; Photoluminescence (PL); XPS

Preparation and properties of KCl-doped Cu₂O thin film by electrodeposition by Xiaojiao Yu; Xinming Li; Gang Zheng; Yuchen Wei; Ama Zhang; Binghua Yao (pp. 340-345).

► Cu₂O thin film were fabricated by electrodeposition KCl as doping agent. ► KCl-doped influence morphology of Cu₂O thin film. ► KCl-doped influence resistivity, open-circuit voltage and conduction type. ► Annealing processing influence resistivity and open-circuit voltage. ► The forbidden band width of Cu₂O thin film is 1.98eV.With the indium tin oxide-coated glass as working electrode, cuprous oxide thin film is fabricated by means of electrodeposition. The effects of KCl doped and annealing treatment upon Cu₂O thin film morphology, surface resistivity, open-circuit voltage, electric conduction types and visible light response are studied. The research results indicate that KCl doped has a great effect upon Cu₂O crystal morphology, thus, making Cu₂O thin film surface resistivity drop, and the open-circuit voltage increase and that electric conduction types are transformed from p type into n type, and the visible light (400–500nm) absorption rate is slightly reduced. Annealing treatment can obviously decrease Cu₂O thin film surface resistivity and improve its open-circuit voltage. When KCl concentration in electrolytic solution reaches 7mmol/L, Cu₂O thin film morphology can be changed from the dendritic crystal into the cubic crystal and Cu₂O thin film surface resistivity decreases from the initial 2.5×10⁶Ωcm to 8.5×10⁴Ωcm. After annealing treatment at 320°C for 30min, the surface resistivity decreases to 8.5×10²Ωcm, and the open-circuit voltage increases from the initial 3.1mV to 79.2mV.

Keywords: Cuprous oxide thin film; Potassium chloride doped; Electrodeposition; Performance

Laser-induced damage of the optical coatings due to organic contamination in vacuum by Xiulan Ling; Gao Wang; Yuanan Zhao; Xiaofeng Liu; Jianda Shao (pp. 346-351).

► We show the effect of organic contaminations on the laser-induced damage in vacuum. ► Surface adsorption layer model was presented to evaluate this impact. ► The distributions of electric field and temperature field were calculated. ► The mere organic contaminations cannot induce the thermal damage of the films. ► The decrease of LIDTs is due to the inter-coupling between defects and contaminations.Monolayer ZrO₂ and multi-layer ZrO₂/SiO₂ films were contaminated deliberately with toluene in vacuum environments. Laser-induced damage tests were made on clean and contaminated ZrO₂/SiO₂ high reflective films. Surface adsorption layer model was presented to evaluate the impact of organic contaminations on the laser-induced damage. Based on this model, the distributions of electric field and temperature field in multi-layer ZrO₂/SiO₂ films were calculated. Results show that the mere organic contaminations cannot induce the thermal damage of optical films. The inter-coupling between defects and organic contaminations is probably attributed to the decrease of the laser-induced damage threshold in contaminated samples.

Keywords: Vacuum; Laser-induced damage; Defect; Organic contaminationPACS; 42.79.Wc; 81.70.Fy; 68.37.Hk

Deposition of fluorocarbon films by Pulsed Plasma Thruster on the anode side by Rui Zhang; Daixian Zhang; Fan Zhang; Zhen He; Jianjun Wu (pp. 352-358).

► Low fluorine–carbon ratio (0.64–0.86) fluorocarbon films are deposited by PPT. ► The chemical composition of the films shows different trends in different regions. ► The surface roughness decreases with the increase in the deposition angles. ► The optical properties show significant angular dependence.Fluorocarbon thin films were deposited by Pulsed Plasma Thruster at different angles on the anode side of the thruster. Density and velocity of the plasma in the plume of the Pulsed Plasma Thruster were determined using double and triple Langmuir probe apparatus respectively. The deposited films were characterized by X-ray photoelectron spectroscopy (XPS), scanning probe microscope (SPM) and UV–vis spectrometer. Low F/C ratio (0.64–0.86) fluorocarbon films are deposited. The F/C ratio decreases with angle increasing from 0 degree to 30 degree; however it turns to increase with angle increasing from 45 degree to 90 degree. The films deposited at center angles appear rougher compared with that prepared at angles beyond 45 degree. These films basically show having strong absorption properties for wavelength below 600nm and having enhanced reflective characteristics. Due to the influence of the chemical composition and the surface morphology of the films, the optical properties of these films also show significant angular dependence.

Keywords: Abbreviations; PPT; Pulsed Plasma Thruster; XPS; X-ray photoelectron spectroscopy; SPM; Scanning probe microscope; FTIR; Fourier transform infrared spectroscopy; AES; Auger Electron SpectroscopyPulsed Plasma Thruster; Plume deposition; Fluorocarbon film; XPS; SPM

Na adsorption on SrTiO₃ (001) surface and its interaction with water: A DFT calculation by Jiajia Wang; Zhaosheng Li; Zhigang Zou (pp. 359-363).

► TiO₂ termination of SrTiO₃ (001) surface is more favorable for Na adsorption. ► The SrO termination has stronger screening effect than the TiO₂ termination. ► Doping N into SrTiO₃ is able to enhance Na adsorption on SrTiO₃ (001) surface. ► The Na adsorbed SrTiO₃ (001) surface does not facilitate water dissociation.Na adsorption on SrTiO₃ (001) surface and its interaction with water were studied by using density functional theory approach. Our results showed that, owing to the stronger screening effect of SrO termination, TiO₂ termination was more favorable for Na adsorption than the SrO termination. Doping with N at the site of oxygen in SrTiO₃ was used to enhance Na adsorption. The adsorption energy of Na adsorption on the N doped SrTiO₃ (001) surface was enhanced remarkably, which attributed to charge compensation between Na and N. However, the Na adsorbed SrTiO₃ (001) surface did not facilitate water dissociation, which was consistent with the experimental results.

Keywords: SrTiO; ₃; (0; 0; 1) surface; Na adsorption; Water adsorption; DFT calculation

The influence of potassium doping on hydrogen adsorption on carbon nanocone material studied by thermal desorption and photoemission by Xiaofeng Yu; Steinar Raaen (pp. 364-369).

► Potassium doping of a carbon nanocone containing material has been studied. ► Experimental techniques are photoemission and temperature programmed desorption. ► Hydrogen is adsorbed on the K doped material. ► The hydrogen desorption temperature increases by more than 100K upon doping. ► An increased hydrogen uptake of about 40% is observed.Hydrogen adsorption/desorption on potassium doped carbon nanocones was studied by temperature programmed desorption (TPD), X-ray photoelectron spectroscopy, and ultraviolet photoelectron spectroscopy. TPD shows that the hydrogen storage was enhanced by up to 40% after potassium doping. Hydrogen adsorption on K-modified carbon nanocone material seems more stable than that on the undoped material. The XPS results indicate that there is charge transfer from potassium to carbon. The C 1s binding energy increases with increased potassium doping and the peak becomes wider. These binding energy shifts may be explained by work function changes related to potassium doping. The K 2p spectra indicate that there are two different local environments for potassium on the carbon cone material.

Keywords: Carbon nanocones; Hydrogen adsorption; TPD; XPS; UPS; Charge transfer

Experimental and theoretical studies on the influence of water vapor on the performance of a Ce-Cu-Ti oxide SCR catalyst by Xuesen Du; Xiang Gao; Liwen Cui; Zhizhan Zheng; Peidong Ji; Zhongyang Luo; Ke-fa Cen (pp. 370-376).

Display Omitted► H₂O inhibits the SCR performance of the Ce-Cu-Ti-O catalyst at low temperatures. ► H₂O enhances the NO conversion of the Ce-Cu-Ti-O catalyst at high temperatures. ► The presence of H₂O would greatly decrease the NH₃ adsorption amount. ► NH₃ oxidation at high temperatures decreases with the addition of 10% H₂O.H₂O inhibits the SCR performance of the Ce-Cu-Ti (CCT) oxide catalyst at low temperatures, while it promotes SCR performance at high temperatures above 300°C. A combination of experiments and DFT calculations was applied to study this phenomenon. NH₃ adsorption profiles showed that the presence of H₂O would greatly decrease the NH₃ adsorption amount, especially the weakly adsorbed NH₃ part. The DFT calculations of H₂O and NH₃ adsorption on the CCT catalyst showed that the presence of H₂O would compete with NH₃ to be adsorbed on the catalyst. NH₃ oxidation experiments indicated that NH₃ oxidation at high temperatures decreases with the addition of 10% H₂O. The DFT calculation also indicated that H₂O would inhibit NH₃ oxidation. The inhibition effect of H₂O at low temperatures could be attributed to the competing adsorption of H₂O with NH₃. The promotional effect of H₂O at high temperatures was due to the inhibition of NH₃ oxidation.

Keywords: Selective catalytic reduction; Ceria oxide; Copper oxide; Anatase; Water vapor; DFT calculation

Growth and characterization of lead-free piezoelectric BaZr_0.2Ti_0.8O₃–Ba_0.7Ca_0.3TiO₃ thin films on Si substrates by B.C. Luo; D.Y. Wang; M.M. Duan; S. Li (pp. 377-381).

► Lead-free piezoelectric BCZT thin films were grown on Si by magnetron sputtering. ► The conduction mechanisms and local electromechanical properties were investigated. ► A considerably high effective piezoelectric coefficient of 94±4pm/V was observed.Lead-free piezoelectric BaZr_0.2Ti_0.8O₃–Ba_0.7Ca_0.3TiO₃ (BCZT) thin films were grown on La_0.7Sr_0.3MnO₃-buffered Si (001) by off-axis RF magnetron sputtering at temperatures ranging from 550 to 810°C. In this article, we present the detailed investigation on structure, leakage current behaviors and electromechanical properties of BCZT thin films. The crystallographic texture and grain size of the as-grown thin films are strongly dependent on the growth temperature, which consequently affects the leakage behaviors and local electromechanical properties. The crystallographic orientation becomes better and the grain size increases when increased the substrate temperature. The dominant leakage mechanism is found to be space-charge-limited conduction at low electric field, while a Fowler-Nordheim tunneling is confirmed in high electric field region for the films deposited at 710°C and 810°C. The increasing growth temperature also leads to remarkable improvement in the local electromechanical properties of the films. The BCZT film deposited at an optimal temperature of 810°C exhibits a considerably high effective piezoelectric coefficient d33,_f of 94±4pm/V, which is comparable to that of a typical lead zirconate titanate thin film.

Keywords: Lead-free piezoelectricity; Leakage; Electromechnical properties

Direct laser writing of 3D polymer micro/nanostructures on metallic surfaces by Sima Rekštytė; Albertas Žukauskas; Vytautas Purlys; Yuri Gordienko; Mangirdas Malinauskas (pp. 382-387).

► Fabrication of 2.5D and 3D microstructures on opaque surfaces is demonstrated. ► Structures out of various photopolymers are fabricated with submicrometer resolution. ► Surface roughness lower than microstructure's height has no significant impact to its quality.Spectra of fields for applications of polymeric 3D micro/nanostructures are rapidly widening thus demanding the development of versatile precise and efficient fabrication methods that can be used to process a variety of materials and could be implemented to form tiny devices on a variety of surfaces without influencing their structural quality. We present the latest results obtained using laser lithography approach: 3D polymeric structures with submicrometer spatial resolution on different opaque surfaces such as semiconductors (Si) and various metals (Cr, Al, Fe and Ti). The photostructuring was performed using a range of photosensitive materials such as acrylate based AKRE23, acrylated biodegradable PEG-DA-258, epoxy based mr-NIL 6000, hybrid organic-inorganic SZ2080 and Ormocore b59.

Keywords: Direct laser writing; Hybrid polymers; 3D microstructures; Opaque surfaces; Integrated microsystems; Electro conductive surfaces

Stable Ir/SiO₂ catalyst for selective hydrogenation of crotonaldehyde by Xiao Hong; Bo Li; Yuejuan Wang; Jiqing Lu; Gengshen Hu; Mengfei Luo (pp. 388-394).

Display Omitted► Selective hydrogenation of crotonaldehyde was conducted over Ir/SiO₂ catalysts. ► The catalysts did not deactivate during the reaction and reached steady state in 9h. ► The Ir/SiO₂ catalysts contained Ir⁰ and Ir^δ+ species. ► Chemical nature of Ir species and surface acidity were important for the reaction.Vapor-phase selective hydrogenation of crotonaldehyde was conducted over Ir/SiO₂ catalysts to investigate the effects of Ir loading on the catalytic behaviors. The catalysts were characterized by X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), CO chemisorption, temperature-programmed reduction (TPR), diffuse reflectance infrared Fourier transform spectra of CO adsorption (CO-DRIFTS), NH₃ temperature-programmed desorption (NH₃-TPD), and temperature-programmed oxidation (TPO). It was found that the particle size of Ir in the catalyst increased with Ir loading, being 2.1, 3.9 and 6.7nm for the 1Ir/SiO₂, 3Ir/SiO₂ and 5Ir/SiO₂ catalyst, respectively. The Ir species on the Ir/SiO₂ catalysts consisted of Ir⁰ and Ir^δ+, but the average valence of Ir species decreased with increasing Ir loading. Also, catalytic testing results revealed that the reactivity of the catalyst increased with Ir loading. Interestingly, it was found that the reaction underwent an induction period, with the conversion of crotonaldehyede and the selectivity to crotyl alcohol gradually increasing during the reaction, and eventually reaching a steady state. The highest selectivity (77.6%) to crotyl alcohol was obtained over the 3Ir/SiO₂ catalyst, and the conversion increased gradually to 15.6%. The catalytic behavior of these stable catalysts could be attributed to the proper Ir particle size, the existence of Ir⁰ and Ir^δ+ species on the surface, and high amount of surface acid sites in these catalysts.

Keywords: Ir/SiO; ₂; catalyst; Crotonaldehyde; Selective hydrogenation; Crotyl alcohol

Corrosion of Cr bearing low alloy pipeline steel in CO₂ environment at static and flowing conditions by Lining Xu; Shaoqiang Guo; Wei Chang; Taihui Chen; Lihua Hu; Minxu Lu (pp. 395-404).

► Corrosion behavior of Cr3MoNi steel at flowing and static condition in CO₂ environment. ► Flow enhances the chemical removal of FeCO₃ corrosion product. ► Flow leads to an uniform distribution of Cr compound in the amorphous corrosion scales. ► Flow suppresses the presence of the potential pits and leads to a more flat scale/substrate interface. ► Potential pit presented at static condition can be controlled by the Cr reenrichment of scales in the pit.We study the corrosion performance of Cr bearing low alloy pipeline steel (Cr3MoNi) in CO₂ saturated formation water, under both static and flowing conditions. Cross-sectional morphologies of corrosion scales at progressively increased test duration are observed by scanning electron microscopy. The characteristic of the corrosion scales are investigated by energy dispersive X-ray spectroscopy and X-ray diffraction. Our results show that the corrosion rate of Cr3MoNi steel at flowing condition is higher than that of static condition, and the degree of Cr enrichment in the scales at flowing condition is also higher. Flow also makes ions distribute evenly in the solution close to the specimen, leading to a uniform distribution of Cr compound in the amorphous corrosion scales. In this way, flow suppresses the presence of the potential pits and also leads to a more flat scale/substrate interface.

Keywords: Corrosion; Cr bearing low alloy steel; Carbon dioxide; Flowing condition; Static condition; Scales

In situ diffuse reflectance infrared Fourier transform spectroscopy study of formaldehyde adsorption and reactions on nano γ-Fe₂O₃ films by Kaijin Huang; Lingcong Kong; Fangli Yuan; Changsheng Xie (pp. 405-410).

► The nano γ-Fe₂O₃ films gas sensor could effectively monitor formaldehyde gas. ► The surface adsorption and reaction process was studied by in situ DRIFTS method. ► The possible mechanism of the reaction process was discussed.The nano γ-Fe₂O₃ films gas sensor was fabricated by the screen printing technology. The phase structures and morphologies of nano γ-Fe₂O₃ films were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM), respectively. The gas sensitivity of the films to 100ppm formaldehyde was investigated. The surface adsorption and reaction process between nano γ-Fe₂O₃ films and formaldehyde was studied by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) method at different temperatures. DRIFTS results showed that dioxymethylene, formate ions, polyoxymethylene and molecularly formaldehyde surface species were detected when the nano γ-Fe₂O₃ films exposed to 100ppm formaldehyde at different temperatures. A possible mechanism of the reaction process was discussed.

Keywords: Gas sensors; Nano γ-Fe; ₂; O; ₃; films; Formaldehyde; DRIFTS; Gas sensing mechanism

Diamond-coated ATR prism for infrared absorption spectroscopy of surface-modified diamond nanoparticles by Z. Remes; H. Kozak; B. Rezek; E. Ukraintsev; O. Babchenko; A. Kromka; H.A. Girard; J.-C. Arnault; P. Bergonzo (pp. 411-417).

► A novel tool for attenuated total reflectance (ATR) FTIR employing diamond-coated prism. ► Enhanced sensitivity, resolution and repeatability. ► IR absorption spectra characterizing surface moieties, in particular on plasma-oxidized and hydrogenated diamond nanoparticles.Linear antenna microwave chemical vapor deposition process was used to homogeneously coat a 7cm long silicon prism by 85nm thin nanocrystalline diamond (NCD) layer. To show the advantages of the NCD-coated prism for attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) of nanoparticles, we apply diamond nanoparticles (DNPs) of 5nm nominal size with various surface modifications by a drop-casting of their methanol dispersions. ATR-FTIR spectra of as-received, air-annealed, plasma-oxidized, and plasma-hydrogenated DNPs were measured in the 4000–1500cm⁻¹ spectral range. The spectra show high spectral resolution, high sensitivity to specific DNP surface moieties, and repeatability. The NCD coating provides mechanical protection against scratching and chemical stability of the surface. Moreover, unlike on bare Si surface, NCD hydrophilic properties enable optically homogeneous coverage by DNPs with some aggregation on submicron scale as evidenced by scanning electron microscopy and atomic force microscopy. Compared to transmission FTIR regime with KBr pellets, direct and uniform deposition of DNPs on NCD-ATR prism significantly simplifies and speeds up the analysis (from days to minutes). We discuss prospects for in situ monitoring of surface modifications and molecular grafting.

Keywords: ATR FTIR; CVD; Nanocrystalline diamond; Microwave; Hydrogenation; Nanopowder

Novel high damage-tolerant, wear resistant MoSi₂-based nanocomposite coatings by Jiang Xu; Zhengyang Li; Zong-Han Xie; Paul Munroe; Xiao Lin Lu; Xiu Feng Lan (pp. 418-427).

► The nanocomposite coatings show an improved in both hardness and toughness. ► The soft amorphous Si₃N₄ phase arrests cracks, strongly reducing the crack driving force. ► The nanocomposite coatings exhibit a higher wear resistance than monolithic MoSi₂.In this study, novel MoSi₂-based nanocomposite coatings were deposited on Ti-6Al-4V substrates by a two-step process involving firstly, deposition of MoSi₂-based coatings, using a double cathode glow discharge process and, secondly, plasma nitridation of the as-deposited coatings. The aim of this latter step is to introduce nitrogen into the coating and promote the formation of amorphous silicon nitride. The resulting coatings were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscope (XPS), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). It was found that the nanocomposite coatings were composed of nanocrystallite Mo₅Si₃ and MoSi₂ grains embedded in an amorphous Si₃N₄ matrix. The mechanical properties and damage resistance of the coatings were evaluated by both Vickers indentation and nanoindentation techniques. Dry sliding wear tests were performed using a ball-on-disc type tribometer, in which the coated samples were tested against a ZrO₂ ceramic ball at normal loads of 2.8 and 4.3N under ambient conditions. Compared with the monolithic MoSi₂ nanocrystalline coating, the specific wear rates of the nanocomposite coatings decreased by an order of magnitude. The specific wear rate was further improved by about 20% through the addition of Al, which was attributed to an optimum combination of mechanical properties.

Keywords: Nanocomposites; Mechanical properties; Wear; Coatings

Effects of substrate temperature on structural and electrical properties of SiO₂-matrix boron-doped silicon nanocrystal thin films by Junjun Huang; Yuheng Zeng; Ruiqin Tan; Weiyan Wang; Ye Yang; Ning Dai; Weijie Song (pp. 428-431).

► The effects of T_s on the micro-structure and electrical properties of boron-doped Si-NC thin films were investigated. ► The phase separation of annealed SRSO thin films was hindered when the T_s was increased from 373K to 676K. ► When the T_s was increased from 373K to 676K, the crystalline fraction of 1373K-annealed thin films decreased from 52.2% to 38.1%. ► The dark conductivity of 1373K-annealed thin films reduced from 8×10⁻³S/cm to 5.5×10⁻⁵S/cm when the T_s was increased from 373K to 676K.In this work, silicon-rich SiO₂ (SRSO) thin films were deposited at different substrate temperatures ( T_s) and then annealed by rapid thermal annealing to form SiO₂-matrix boron-doped silicon-nanocrystals (Si-NCs). The effects of T_s on the micro-structure and electrical properties of the SiO₂-matrix boron-doped Si-NC thin films were investigated using Raman spectroscopy and Hall measurements. Results showed that the crystalline fraction and dark conductivity of the SiO₂-matrix boron-doped Si-NC thin films both increased significantly when the T_s was increased from room temperature to 373K. When the T_s was further increased from 373K to 676K, the crystalline fraction of 1373K-annealed thin films decreased from 52.2% to 38.1%, and the dark conductivity reduced from 8×10⁻³ S/cm to 5.5×10⁻⁵S/cm. The changes in micro-structure and dark conductivity of the SiO₂-matrix boron-doped Si-NC thin films were most possibly due to the different amount of SiO₄ bond in the as-deposited SRSO thin films. Our work indicated that there was an optimal T_s, which could significantly increase the crystallization and conductivity of Si-NC thin films. Also, it was illumined that the low-resistivity SiO₂-matrix boron-doped Si-NC thin films can be achieved under the optimal substrate temperatures, T_s.

Keywords: Si nanocrystal; Substrate temperature; Phase separation; Electrical property

Synthesis of hollow carbonyl iron microspheres via pitting corrosion method and their microwave absorption properties by Chunlei Yin; Yuebin Cao; Junmei Fan; Liuyang Bai; Fei Ding; Fangli Yuan (pp. 432-438).

Display Omitted► Hollow carbonyl iron microspheres were prepared via pitting corrosion of commercial carbonyl iron microspheres in ferric solution. ► Several other hollow metal particles such as Ni, Co and Cu can also be prepared through this pitting corrosion method. ► The hollow carbonyl iron microspheres show more excellent microwave absorption properties than the initial ones.In this paper, we report a new method to prepare hollow carbonyl iron microspheres, which is called pitting corrosion method. The comparison of the morphology, specific surface area and apparent density of the initial and pitting corroded carbonyl iron microspheres demonstrate that the pitting corroded carbonyl iron has a hollow structure. The pitting corrosion process is uncovered through the concentration change of ferrous ion in the reaction solution and the TEM images with different pitting corrosion time. The formation mechanism of hollow microspheres via pitting corrosion is analyzed. Furthermore, this pitting corrosion method can also be used to prepare other hollow metal particles, such as Ni, Co, and Cu particles. The electromagnetic parameters of the samples before and after pitting corrosion are measured. The calculated reflection loss of the pitting corroded sample for single layer of 0.5mm or 1.0mm thickness at 2–18GHz is much better than that of the initial one. The mechanism of the improvement of the microwave absorption properties is discussed.

Keywords: Carbonyl iron; Hollow microspheres; Pitting corrosion; Microwave absorption

Effect of indium doping level on certain physical properties of CdS films deposited using an improved SILAR technique by K. Ravichandran; V. Senthamilselvi (pp. 439-444).

► Introduction of new SILAR method, named as Improved SILAR (ISILAR) technique. ► Comparatively good stoichiometry is achieved. ► Results from different studies are corroborated well.The influence of indium (In) doping levels (0, 2, …, 8at.%) on certain physical properties of cadmium sulphide (CdS) thin films deposited using an improved successive ionic layer adsorption and reaction (ISILAR) method has been studied. In this improved SILAR technique, a fresh anionic solution was introduced after a particular number of dipping cycles in order to achieve good stoichiometry. All the deposited films exhibited cubic phase with (111) plane as preferential orientation. The calculated crystallite size values are found to be decreased from 54.80nm to 23.65nm with the increase in In doping level. The optical study confirmed the good transparency (80%) of the film. A most compact and pinhole free smooth surface was observed for the CdS films with 8at.% of In doping level. The perceived photoluminescence (PL) bands endorsed the lesser defect crystalline nature of the obtained CdS:In films. The chemical composition analysis (EDAX) showed the near stoichiometric nature of this ISILAR deposited CdS:In films.

Keywords: In doped CdS thin films; ISILAR; Structural; Morphology; Photoluminescence; Window layer

Effects of solution pH on the structure and biocompatibility of Mg-containing TiO₂ layer fabricated on titanium by hydrothermal treatment by Xingling Shi; Kanji Tsuru; Lingli Xu; Giichiro Kawachi; Kunio Ishikawa (pp. 445-451).

► Magnesium was combined into TiO₂ layer on titanium to improve biocompatibility. ► Effects of hydrothermal solution pH on oxide layer properties were investigated. ► pH 5.5 was found to be the optimum according to initial cellular responses.Pure titanium was subjected to surface modification in order to improve its bioactivity. Samples wet-polished by abrasive paper were hydrothermally treated in 0.1mol/l MgCl₂ solutions with different pH values (5.5, 7.5 and 9.5) at 200°C for 24h. By forming nano-sized anatase precipitations, hydrothermal treatment increased the thickness of the oxide layer obviously and Mg was found to distribute all through the oxide layer. Treatment in solution with a low pH formed TiOMg bond as MgTiO₃, whereas, high pH induced Mg(OH)₂ precipitation onto the samples. Cell attachment and spreading were improved on samples treated in the solution of pH 5.5. As treatment solution pH rose, protein (Bovine Serum Albumin, BSA) adsorption on treated samples increased; however, initial osteoblast attachment and spreading were impaired. It is suggested that, hydrothermal treatment in MgCl₂ solution can improve the bioactivity of titanium by immobilizing Mg into oxide layer, however, the chemical state and amount of Mg should be well controlled.

Keywords: Titanium; Magnesium; Hydrothermal treatment; MC3T3-E1

Effects of pre-sputtered Al interlayer on the atomic layer deposition of Al₂O₃ films on Mg–10Li–0.5Zn alloy by P.C. Wang; T.C. Cheng; H.C. Lin; M.J. Chen; K.M. Lin; M.T. Yeh (pp. 452-456).

► Deposition of a dual-layer Al/Al₂O₃ films on Mg–10Li–0.5Zn substrate using both techniques of magnetron sputtering and atomic layer deposition (ALD). ► Identify the crystal structure, chemical composition, surface morphology of the dual-layer Al/Al₂O₃ films. ► Clarify the effects of dual-layer Al/Al₂O₃ films on the corrosion resistance of Mg–Li alloys.In this study, a dual-layer of Al/Al₂O₃ films was deposited on the Mg–10Li–0.5Zn substrate using both techniques of magnetron sputtering and atomic layer deposition (ALD). The pre-sputtered Al interlayer has a crystalline structure and the ALD-Al₂O₃ film is amorphous. The Al interlayer could effectively obstruct the diffusion out of Li atoms from the Mg–10Li–0.5Zn substrate during the deposition of ALD-Al₂O₃ film. The Mg–10Li–0.5Zn specimen with a dual-layer of Al/Al₂O₃ films exhibits a much better corrosion resistance than those specimens with a single layer of sputtered Al or ALD-Al₂O₃.

Keywords: Magnesium alloys; Magnetron sputtering; Atomic layer deposition; Corrosion resistance

Oriented TiO₂ nanowire array grown on curved surface of Ti wire with superior photoelectrochemical properties by Xiang Dong; Yingying Li; Zhiwei Lin; Jie Ge; Jianbei Qiu (pp. 457-461).

► Well aligned TiO₂ nanowire arrays were prepared on the curved surface of the titanium wires via hydrothermal method. ► Hydrothermal condition and the morphology of the Ti substrate affect the growth orientation of the TiO₂ nanowire. ► TiO₂ nanowire arrays/Ti wire electrode shows superior photoelectrochemical properties. ► We report a facile method for preparing crystallized TiO₂ nanowire arrays on Ti wire substrate.Well-ordered titanium dioxide nanowire arrays were synthesized on the curved surface of titanium wire via hydrothermal method. The specimens were characterized respectively through scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD). It was found that the growing orientations of TiO₂ nanowire were all perpendicular to the wire surface within the range of 360°. The TiO₂ nanowire array were anatase after heat treatment at 450°C for 1h. Moreover, the optical properties of the samples were investigated by UV–vis light absorption spectrum. The growth orientation of the TiO₂ nanowire was mainly affected by hydrothermal condition and the morphology of the Ti substrate. Direct electrical pathway for electron transferring and the increased light-harvesting abilities were responsible for the superior photoelectrochemical activity of the synthesized TiO₂ nanowire array on curved surface of Ti wire. Furthermore, it can enlarge the practical applications range of TiO₂ due to its ringed shaper and flexibility.

Keywords: TiO; ₂; Nanowire array; Curved surface; Titanium wire

Flexible dye-sensitized solar cell fabricated on plastic substrate by laser-detachment and press method by Choonghoe Kim; Seongsu Kim; Myeongkyu Lee (pp. 462-466).

► TiO₂ electrode sinterd on glass is transferred onto plastic substrate by a pulsed laser. ► This process utilizes a laser-induced thermal desorption of nanoparticle film. ► A flexible dye-sensitized solar cell with efficiency of 5.68% is obtained.This report shows that flexible dye-sensitized solar cell can be fabricated by a laser-detachment and press method where the TiO₂ electrode typically sintered on glass source substrate is detached by a laser pulse and then is firmly adhered to the conductive plastic substrate by applying a high pressure. The cells fabricated by this process exhibited 36–43% smaller photocurrent and efficiency than the conventional glass cells with directly coated TiO₂ electrodes. It was attributed to the lowered dye coverage and electron diffusion length, both of which originate from the press-induced reduction of TiO₂ porosity. A maximum efficiency of 5.68% was obtained for the plastic cell. Bending of the electrode led to 20% loss of the current density and efficiency. However, no further performance degradation was observed even when the bending cycle was increased to 100, 300, and 500 times. This indicates that the bending-induced degradation of TiO₂ electrode on the plastic substrate takes place at the first bending.

Keywords: Flexible dye-sensitized solar cell; Laser; Press method

Blue-green and red luminescence from non-polar ZnO:Pb films by X.B. Li; S.Y. Ma; F.M. Li; F.C. Yang; J. Liu; X.L. Zhang; Q. Zhao; X.H. Yang; C.Y. Wang; J. Zhu; C.T. Zhu; X. Wang (pp. 467-472).

► Non-polar growth. ► Large red shift of the optical band gap is related to the decreasing of carrier concentration and incorporation of charged defects. ► The three main emission peaks may constitute white light. ► Non-polar growth of ZnO has improved greatly the luminous efficiency.Pure zinc oxide (ZnO) and lead (Pb) doped zinc oxide (ZnO:Pb) films with different Pb doping concentrations were deposited on glass substrate by using radio frequency reactive magnetron sputtering technique. X-ray diffraction spectroscopy measurements showed that all samples with the (100) preferential orientation were growth of the non-polar. The results of X-ray photoelectron spectroscopy analysis suggested that the Pb ions were successfully doped into lattice of ZnO and the valence of Pb in the ZnO films was a mixed state of +2 and +4. Optical band gaps of the ZnO:Pb were 3.24, 2.92, 2.86 and 2.74eV with the increase of Pb doping concentration, it could attribute this red shift phenomenon to the decrease of carrier concentration. Photoluminescence measurements showed that a broad emission band including the two blue emission peaks are about at 437nm and 470nm, one green and red emission peaks are about at 510nm and 710nm, which may compound white light. Moreover, growth of non-polar ZnO enhanced enormously the luminous efficiency of photoluminescence in our experiment. The current–voltage measurements between two surface electrodes showed the increase in resistance with increase of Pb doping concentration.

Keywords: Non-polar; Chemical state; Optical band gap; White light; I; –; V; characteristics

Surface chemical functionalities affect the behavior of human adipose-derived stem cells in vitro by Xujie Liu; Qingling Feng; Akash Bachhuka; Krasimir Vasilev (pp. 473-479).

.Display Omitted► Different plasma polymerized films were generated on hydroxyapatite substrates. ► The effect of surface chemical functionalities on behavior of hASCs was examined. ► TheNH₂ modified surfaces encourage osteogenic differentiation of hASCs. ► TheCOOH modified surfaces promote cell adhesion and spreading of hASCs.This study examines the effect of surface chemical functionalities on the behavior of human adipose-derived stem cells (hASCs) in vitro. Plasma polymerized films rich in amine (NH₂), carboxyl (COOH) and methyl (CH₃), were generated on hydroxyapatite (HAp) substrates. The surface chemical functionalities were characterized by X-ray photoelectron spectroscopy (XPS). The ability of different substrates to absorb proteins was evaluated. The results showed that substrates modified with hydrophilic functional group (COOH andNH₂) can absorb more proteins than these modified with more hydrophobic functional group (CH₃). The behavior of human adipose-derived stem cells (hASCs) cultured on different substrates was investigated in vitro: cell counting kit-8 (CCK-8) analysis was used to characterize cell proliferation, scanning electronic microscopy (SEM) analysis was used to characterize cell morphology and alkaline phosphatase (ALP) activity analysis was used to account for differentiation. The results of this study demonstrated that theNH₂ modified surfaces encourage osteogenic differentiation; theCOOH modified surfaces promote cell adhesion and spreading and theCH₃ modified surfaces have the lowest ability to induce osteogenic differentiation. These findings confirmed that the surface chemical states of biomaterials can affect the behavior of hASCs in vitro.

Keywords: Adipose-derived stem cell; Plasma polymerization; Surface modification; Hydroxyapatite; Differentiation

Performance of Cr-doped ZnO for acetone sensing by N.H. Al-Hardan; M.J. Abdullah; A. Abdul Aziz (pp. 480-485).

► Zinc oxide (ZnO) thin films were doped with chromium (Cr) through reactive dual sputtering for gas sensing applications. ► The Cr concentrations were in the range of 1–4at%, and were changed by controlling the sputtering power. ► The 1at% Cr doped ZnO showed the highest response at operating temperature of 300°C. ► The sensor shows repeatability and a linear response with the acetone concentrations at the range from 15 to 1000ppm.Zinc oxide (ZnO) doped with chromium (Cr) was synthesized by reactive co-sputtering for gas sensing applications. The effect of varying the contents of Cr (from 1 to 4at%) on the ZnO gas sensor response was studied. X-ray diffraction analysis reveals the high orientation of c-axis of the prepared films. The optimum operating temperature of the undoped ZnO was 400°C and shifted to 300°C for the Cr-doped ZnO under the acetone vapour. The 1% Cr doping ZnO gas sensor was most sensitive for the acetone vapour. The ability of the 1% Cr-doped ZnO to produce repeatable results under different acetone vapour concentrations was tested. The timing properties of the doped Cr ZnO gas sensor were 70 and 95s for the rise and recovery time respectively.

Keywords: Metal oxide gas sensors; Chromium-doped ZnO; VOC sensors; ZnO

Analysis of copper surface features obtained using TEA CO₂ laser at reduced air pressure by M. Momcilovic; M. Trtica; J. Ciganovic; J. Savovic; J. Stasic; M. Kuzmanovic (pp. 486-494).

► Rough copper surface modification with ns laser at reduced air pressure. ► Laser intensity 10⁸W/cm². ► Occurrence of melt pools, bubbles and “halo” effect at the irradiated surface. ► Nearly complete oxygen removal from the damage area. ► Differences in plasma spectral emission for non-rotating and rotating target regime.Interaction of a transversely excited atmospheric (TEA) CO₂ laser with rough copper surface, at reduced air pressure, was studied. Optical pulse duration of the laser employed was ∼2μs, with the initial spike FWHM of ∼100ns. Laser energy density of ∼32J/cm² (intensity ∼10⁸W/cm²) was above the plasma ignition threshold. Morphological features of the copper can be summarized as follows: (i) superficial damages, which take crater-shaped form at a higher number of accumulated laser pulses, (ii) development of melt pools with visible bubbles inside the damage region, (iii) formation of solid droplets at near periphery, and (iv) presence of “halo” effect at the irradiated surface. The laser induced surface changes were influenced by the target plasma formation. The formation of plasma influenced the laser–target interaction in two opposite ways: trough absorption of laser energy by the plasma, i.e. trough the effect of plasma shielding, and trough energy transfer from the plasma to the sample. Optical emission spectra were compared for laser induced plasma originated by a single and by cumulative laser pulses. It was found that plasma dimensions and emission intensities have a strong correlation with the number of accumulated laser pulses. Enhancement of both atomic and ionic copper lines was registered when laser induced plasma originated from a single pulse. Chemical analysis of the surface showed a tendency of copper content increase and oxygen content reduction when going from non-irradiated region to the central irradiated region. In the central damage zone, nearly pure copper was present which can be advantageous for some applications due to considerably lower contamination.

Keywords: Copper laser modification; ns TEA CO; ₂; laser; Laser induced plasma; Reduced air pressure

A facile route of microwave to fabricate PVA-coating Ag nanofilm used as NIR-SERS active substrate by Renming Liu; Mingjun Feng; Deqing Zhang; Yongbo Su; Chenbo Cai; Minzhen Si (pp. 495-502).

SEM micrograph of PVA-coating Ag nanofilm prepared using the facile method of microwave heating combined with electrostatic self-assembly, and this Ag nanofilm is used as a highly active (EF∼107) and biocompatible NIR-SERS substrate in detections of biological macromolecules. The spectroscopy reproducibility of this PVA-coating Ag nanofilm is checked by recording the area ratios for Raman bands at 1121/1041, 1234/1041, 1372/1041 and 1570/1041cm⁻¹ of hematin solution (10⁻⁶M) adsorbed on different PVA-coating Ag nanofilms.Display Omitted► The fabrication rout of the PVA-coating Ag nanofilm is facile, low-cost and time-saving. ► The maximum plasmon resonance band of this Ag nanofilm is at ∼780nm, indicating a good NIR characteristic. ► PVA-coating Ag nanofilm fabricated using this simple method is highly NIR-SERS active (EF∼10⁷). ► The roles of PVA molecules employed in fabricating of PVA-coating Ag nanofilm are studied.Surface-enhanced Raman spectroscopy (SERS) is a very sensitive and selective technique for detecting surface species. Recently, SERS has been increasingly employed in the study of biological macromolecules, from DNA and peptides to whole proteins, and cells. However, visible laser sources usually employed in SERS detections always lead to photochemical reactions as well as intensive fluorescence emission from the biological samples. A way to avoid these questions is the employment of near infrared (NIR) laser excitation; thus, it demands the appropriate designs of NIR-SERS substrates in order to obtain the maximum enhancement of the Raman signals from biological analytes. In this work, we demonstrate the fabrication of a new NIR-SERS substrate of polyvinyl alcohol (PVA) coating Ag nanofilms (PVA-coating Ag nanofilm) using a simple and low-cost microwave strategy. The experimental data show that, the plasmon resonance band of the PVA-coating Ag nanofilm is in the region of 400–900nm, and the maximum center is at ∼780nm, which matches well with the 785nm laser excitation employed in this work. With the NIR-SERS detections of hematin and hemoglobin molecules adsorbed on this PVA-coating Ag nanofilm, one can see that the NIR-SERS activity and spectroscopy reproducibility of this NIR-SERS substrate are all perfect. By using of the tested molecule of hematin, the PVA-coating Ag nanofilm shows a high enhancement factor (EF) of ∼10⁷. As the fabrication process of this NIR-SERS substrate is very simple and inexpensive, this method may be used in large-scale preparation of SERS substrates that have been widely applied in Raman analysis. Especially, this PVA-coating Ag nanofilm can also be served as a novel NIR-SERS substrate in biochemical analysis due to its good NIR characteristics.

Keywords: Near-infrared surface-enhanced Raman scattering (NIR-SERS); PVA-coating Ag nanofilm; Microwave; Biological macromolecule; Detection

A study on grinding surface waviness of woven ceramic matrix composites by Xiaoyan Cao; Bin Lin; Xiaofeng Zhang (pp. 503-512).

Display Omitted► Some outstanding characteristics of 2.5D SiO₂/SiO₂ grinding surface waviness are discovered. ► Three-dimensional morphology evaluation parameters are calculated to evaluate surface waviness. ► An experiment with surface profile measurement instrument is executed to validate the evaluated results. ► The performance of material surface is predicted.It is difficult to evaluate and predict the mechanical surface quality of woven ceramic matrix composites due to their anisotropic and non-homogeneous structure. The present paper proposed a new method of evaluating grinding surface quality on composites by the study on surface waviness. Using a non-contact optical measurement instrument, the method was developed on 2.5D SiO₂/SiO₂ composite. Three-dimensional (3D) surface characterization parameters were calculated to evaluate the surface waviness. Then the results were verified by an experiment using a contact surface profile measurement instrument. The formation mechanism of the waviness is also analysed in this paper according to knowledge on mechanical damage phenomenology. Fiber orientation plays the decisive role in grinding surface waviness of woven ceramic matrix composites, which is different from traditional waviness formation theory caused by machine tool system vibration. And we found some outstanding characteristics of the surface waviness. If the tow was perpendicular to the grinding surface, the surface waviness was properly on wave crest. while if the tow was parallel to the grinding surface, it was properly on wave trough. Based on the results obtained, grinding surface waviness of composites can be predicted, then it is expected to provide a useful guideline for optimizing the use performance such as assembling, sealing, lubricity, etc.

Keywords: Ceramic matrix composites; Grinding; Three-dimensional topography measurement; Surface waviness

Fabrication of visible-light-responsive titanium dioxide layer on titanium using anodic oxidization in nitric acid by Naofumi Ohtsu; Hirotaka Kanno; Shinji Komiya; Yoshiteru Mizukoshi; Naoya Masahashi (pp. 513-518).

► Nitrogen-doped TiO₂ layers were fabricated by anodizing a Ti plate in HNO₃ solution. ► All the TiO₂ layers could degrade methylene blue solution under UV light. ► The TiO₂ layers with a larger crystallite size showed visible light response.A visible-light-responsive titanium dioxide (TiO₂) layer was fabricated by anodizing a Ti plate in aqueous nitric acid (HNO₃) solutions, followed by annealing at 723K for 5h in air. The predominant structure of the oxide layer was TiO₂ with an anatase structure that contained ca. 1at% of incorporated nitrogen. The crystallite size of the anatase TiO₂ was enlarged as anodizing voltage increased, but the atomic ratio of the incorporated nitrogen was almost constant. The TiO₂ layers could degrade methylene blue (MB) solution under an UV light at 370nm, exhibiting photocatalytic activity. The activity increased monotonically as the crystallite size of the oxide increased. The TiO₂ layers with their crystallite size exceeding a specific value showed excellent response under visible light at 420, 450, and 505nm. Overall, the results of this study showed that anodic oxidization of Ti in HNO₃ solution is a promising technique for fabrication of a visible-light-responsive TiO₂ layer.

Keywords: Photocatalysis; Titanium dioxide; Nitrogen-doping; Anodic oxidation; Visible-light response

Microstructure and properties of duplex (Ti:N)-DLC/MAO coating on magnesium alloy by Wei Yang; Peiling Ke; Yong Fang; He Zheng; Aiying Wang (pp. 519-525).

► The duplex (Ti:N)-DLC coating with TiN crystalline phase on the MAO coating was deposited on AZ80 Mg alloy. ► The binding strength of duplex (Ti:N)-DLC/MAO coating was improved significantly. ► The duplex (Ti:N)-DLC/MAO coatings showed excellent tribological and corrosive properties.Ti and N co-doped diamond-like carbon ((Ti:N)-DLC) film was deposited on the MAO coated substrate using a hybrid beam deposition system, which consists of a DC magnetron sputtering of Ti target and a linear ion source (LIS) with C₂H₂ and N₂ precursor gas. The microstructure and properties of the duplex (Ti:N)-DLC/MAO coating were investigated. Results indicate that the (Ti:N)-DLC top film with TiN crystalline phase was formed. Ti and N co-doping resulted in the increasing I_D/ I_G ratio. The significant improvement in the wear and corrosion resistance of duplex (Ti:N)-DLC/MAO coating was mainly attributed to the increased binding strength, lubrication characteristics and chemical inertness of (Ti:N)-DLC top film. The superior low-friction and anti-corrosion properties of duplex (Ti:N)-DLC/MAO coating make it a good candidate as protective coating on magnesium alloy.

Keywords: AZ80 Mg alloy; Microarc oxidation; (Ti:N)-DLC top film; Microstructure; Properties

Laser surface cleaning of carbonaceous deposits on diesel engine piston by Y.C. Guan; G.K.L. Ng; H.Y. Zheng; M.H. Hong; X. Hong; Z. Zhang (pp. 526-530).

► Carbonaceous deposits on piston surface were removed by nanosecond pulse laser cleaning. ► Thick and thin layers of stubborn contaminants were deposited non-uniformly on the surface. ► Main constituents of the deposits were Fe₃C, Fe₃O₄, possibly FeOOH, oxygenated hydrocarbons and carboxylates. ► Fe₃C was removed completely and oxygenated hydrocarbons as well as carboxylates were reduced significantly after laser cleaning. ► Oxidation and melting effect took place during laser processing.Carbonaceous deposits of diesel engine piston are known to reduce engine durability and performance. Little research has been conducted on the deposits removal by laser technique. In this paper, the deposits on the surface of piston crown part before and after laser cleaning were examined by FTIR, XPS and SEM/EDX. The deposits were found to be distributed non-uniformly on the surface and they could be distinguished as a thicker layer of contaminants, located mainly in the plug region, while a thinner layer can be found in the remaining area. The main constituents of the deposits were analyzed as Fe₃C, Fe₃O₄, possibly FeOOH, oxygenated hydrocarbons as well as carboxylates. Laser cleaning can remove Fe₃C completely, and reduce the concentration of oxygenated hydrocarbons and carboxylates significantly. Fe₂O₃, instead of Fe₃O₄, was formed on the cleaned region.

Keywords: Carbonaceous deposits; Laser cleaning; Piston; FTIR; XPS

15-(4-Carboxyphenyl)-10,15,20-triphenylporphyrin manganese(III) chloride grafted on magnetic polyglycidyl methacrylate as biomimetic catalyst and their catalytic activity by Ying Wang; Pingping Jiang; Weijie Zhang; Jiawei Zheng (pp. 531-538).

Display Omitted► Manganese porphyrin grafted on magnetic polyglycidyl methacrylate through amide bond as a novel material. ► Catalyst was suitable for efficient isolation with high recovery yield. ► An excellent conversion with high selectivity was observed. ► The catalytic activity remained when the catalysts were recycled seven times.Manganese(III) 5-(4-carboxyphenyl)-10,15,20-triphenylporphyrin chloride (Mn(TCPP)Cl) was grafted through amide bond on magnetic polyglycidyl methacrylate (mPGMA) cross-linked by divinylbenzene (DVB). XRD, ICP-AES, N₂ physisorption, SEM, TEM, FTIR and thermal analysis were employed to analyze these novel materials. mPGMA supported catalyst was used for epoxidation with structural durability and steadily reusability. Mn-NH-mPGMA as biomimetic catalyst caused a liquid–solid heterogeneous epoxidation system, and exhibited an excellent conversion with high selectivity at room temperature. Catalytic activity remained when catalyst was recycled seven times. The recycled experiments presented in this article indicated that Mn(TCPP)Cl grafted on mPGMA was suitable for efficient isolation with high recovery yield.

Keywords: Manganese(III) porphyrin; Epoxidation; Magnetic microballoon sphere; Alkenes

Growth of Mn₃O₄ on cellulose matrix: Nanohybrid as a solid phase adsorbent for trivalent chromium by Abdullah M. Asiri; Sher Bahadar Khan; Khalid A. Alamry; Hadi M. Marwani; Mohammed M. Rahman (pp. 539-544).

► Growth of Mn₃O₄ on cellulose surface. ► Nanocomposite. ► Selective adsorbent for Cr³⁺. ► Sensitive sensor for Cr³⁺. ► Environmental applications.A lot of materials such as clays and polymers have been introduced for the detection and uptake of heavy metals in aqueous media but the prospective for industrial development, environmental supplement and health monitoring are still limited. Therefore, nanohybrid has been synthesized by simple growth of Mn₃O₄ on cellulose and the morphological and physiochemical structure of nanohybrid was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), and Fourier transforms infrared spectroscopy. Interestingly, FESEM showed aggregated nanoparticles with an average size of 30nm. From application point of view, the nanohybrid was investigated for the sorption study towards Cu²⁺, Cd²⁺, Co²⁺, Cr³⁺, Fe³⁺, Ni²⁺, Zn²⁺ and Zr⁴⁺ by inductively coupled plasma optical emission spectrometry. Nanohybrid was most selective towards Cr³⁺ and showed the highest sorption capacity for Cr³⁺ which was found to be 61.0mgg⁻¹ while the other metals under study follow the order Zn²⁺>Fe³⁺>Cd²⁺>Zr⁴⁺>Ni²⁺>Co²⁺>Cu²⁺. Moreover, adsorption isotherm data also confirmed that the adsorption process was mainly monolayer onto a surface containing a finite number of adsorption sites. Data of adsorption kinetic model demonstrated that the adsorption of Cr³⁺ onto the nanohybrid obeyed a pseudo second-order kinetic model.

Keywords: Cellulose; Mn; ₃; O; ₄; Nanohybrid; Cr; ³⁺; Adsorption

Effect of magnetism on the ethanol sensitivity of undoped and Mn-doped CuO nanoflakes by R.N. Mariammal; K. Ramachandran; G. Kalaiselvan; S. Arumugam; B. Renganathan; D. Sastikumar (pp. 545-552).

► CuO nanoflakes show room temperature ferromagnetism (RTFM) due to surface defects. ► Mn doping in CuO induces cluster formation on the surface, which destroys RTFM. ► CuO nanoflakes show more ethanol sensitivity compared to Mn-doped CuO nanoflakes. ► The surface has significant influence on both magnetism and ethanol sensitivity. ► Relation between magnetism and sensing mechanism is rarely reported in literature.Undoped and Mn-doped (5 and 10at.%) monoclinic CuO nanoflakes are synthesized by wet chemical method. Undoped CuO nanoflakes exhibit room temperature ferromagnetism (RTFM) due to the uncompensated surface spins originating mainly from the defects and oxygen vacancies on the surface. But Mn-doped CuO nanoflakes do not show RTFM, which is due to the formation of Mn clusters on the surface. FTIR analysis shows that the number of defects, which has significant influence on both the magnetic and ethanol sensing properties is more in undoped CuO than in Mn-doped CuO. The ethanol sensing studies show that CuO is more sensitive to ethanol compared with Mn-doped (10at.%) CuO, which reveals that the sample showing RTFM also shows more ethanol sensitivity compared with the sample that does not show RTFM. The results also reveal that the nature of the sample surface plays a significant role in both the magnetism and the sensing mechanism.

Keywords: Ethanol sensor; Fiber-optic sensor; Nanoflakes; Room temperature ferromagnetism

Surface properties of polyurethane composites for biomedical applications by Ida Dulińska-Molak; Małgorzata Lekka; Krzysztof J. Kurzydłowski (pp. 553-560).

► Synthesis of polyurethanes and polyurethane/calcium carbonate composite; ► Composites showed similar chemical composition with distinct CaCO₃ particle shape. ► The free surface energy of calcite was larger than for aragonite composite. ► The adhesion force to fibronectin correlated linearly with free surface energy. ► The cell growth showed calcite fillers to be potential improvements for implants.The development of tissue engineering in the field of orthopedic surgery is now booming. Biocompatibility is one of the most important characteristics of a biomedical polymer and composites material whose surface is required to interact with a biological system. Since proteins are viewed as the primary and the most important substrate in mediating polymer–organism interactions, the status of the proteins on a material surface is believed to determine the ultimate biocompatibility of a given biomaterial. In order to achieve specific responses between biomaterial surfaces and the adjacent cells, the principles for designing biocompatible materials are brought forth decorating polymer surfaces with bioceramic particles (aragonite and calcite) to induce specific protein adsorption and cell responses. In this work, we describe the adhesion properties of polyurethane/calcium carbonate composites. An understanding of the phenomena of cell adhesion and, in particular, understanding of the proteins involved in osteoblast adhesion on contact with the materials is of crucial importance, the adhesion between fibronectin (FN) and composites PUR/CaCO₃ surfaces were examined using atomic force microscopy (AFM). Moreover, it is found that is correlation between the detachment force and surface free energy (SFE). At the end, in order to estimate the cellular biocompatibility, the human bone derived cells (HBDC) were cultured on PUR/CaCO₃ composites.

Keywords: Polyurethane; Composites; Calcium carbonate; Adhesion force; Surface free energy

Surface functionalization of hexagonal boron nitride and its effect on the structure and performance of composites by Wenqin Jin; Wei Zhang; Yuwen Gao; Guozheng Liang; Aijuan Gu; Li Yuan (pp. 561-571).

► Organized hexagonal boron nitride (OhBN) was synthesized using a new method. ► OhBN has 5 times more amine groups than original hexagonal boron nitride (hBN). ► OhBN/bismaleimide (BD) composites have remarkably improved integrated performances. ► The surface nature of fillers plays obvious effect on the structure of composites.A new organized hexagonal boron nitride (OhBN) with significantly increased amount of amine groups was synthesized, and characterized by Fourier Transform Infrared (FTIR), X-ray Photoelectron Spectroscopy (XPS), Thermogravimetric (TG) analysis, UV–vis Transmittance Spectra, Transmission Electron Microscope (TEM) and the potentiometric titration. The content of amine groups for OhBN is about 5 times of that for original hexagonal boron nitride (hBN). Based on the preparation of OhBN, new composites consisting of OhBN and bismaleimide (BD) resin were developed, which show greatly improved integrated performance (including dynamic mechanical, dielectric and thermal properties) compared with BD resin and the hBN/BD composites. In the case of the OhBN/BD composite with 15wt% OhBN, its storage modulus, dielectric loss, thermal conductivity and coefficient of thermal expansion are about 1.2, 0.56, 1.11 and 0.92 times of the corresponding values of hBN/BD composite, respectively; moreover, the glass transition temperature of the former is 15°C higher than that of the latter. These interesting results suggest that the integrated performance of the composites is closely related to the surface nature of the fillers because the change in the surface nature not only varies the chemical structure, free volume and crosslinking density of the composite, but also determines the interfacial nature between inorganic fillers and the resin matrix. This investigation demonstrates that the method proposed herein provides a new approach to prepare organized inorganic fillers as well as corresponding composites with controlled structure and expected performances for cutting-edge industries.

Keywords: Hexagonal boron nitride; Bismaleimide; Interface; Dynamic mechanical property; Dielectric property

Study on the effects of different sulfur vaporization temperature on the properties of CuInS₂ thin films by Seung Wook Shin; Jun Hee Han; Jeong Yong Lee; Yeon Chan Park; G.L. Agawane; A.V. Moholkar; Myeong-Gil Gang; Chae Hwan Jeong; Jin Hyeok Kim; Jae Ho Yun (pp. 572-577).

► CIS thin films were synthesized by sulfurization of In/Cu metallic precursor. ► Effects of S vaporization temperatures on the properties of CIS thin films were investigated. ► The low cost and high PCE of TFSCs can be fabricated using CIS absorber layer.CuInS₂ (CIS) absorber thin films were prepared by sulfurization of In/Cu metallic stacked precursor. The precursor thin films were sulfurized using a commercial furnace system in the S₂ (s)+Ar atmosphere at 425°C for 1h. Effects of different S vapor temperature from 150 to 400°C on the structural, morphological, compositional and optical properties of CIS thin films were investigated. X-ray diffraction and Raman studies showed that the sulfurized thin films with S vaporization temperature below 300°C exhibited CIS tetragonal structure with secondary phases such as Cu_xS_y, CuIn₅S₈, and In_xS_y. The sulfurized thin films with S vaporization temperature over 350°C showed a single CIS tetragonal structure. Compositional ratio of CIS thin films showed that Cu/In and S/(Cu+In) ratio in the CIS thin films with S vaporization temperature over 350°C were 1.0–1.2 and 0.9–1.1, respectively, while compositional ratio deviated from stoichiometry when the sulfurized thin films below S vaporization temperature of 350°C. Optical study showed that the band gap energy and the absorption coefficient of CIS thin films were estimated from 1.18eV to 1.5eV and over 10⁴cm⁻¹, respectively.

Keywords: CuInS; ₂; (CIS); Thin film solar cells (TFSCs); Sulfurization; Vaporization temperature; S powder; Low cost process

Concentration dependent structural and optical properties of electrochemically grown ZnO thin films and nanostructures by Trilok Singh; D.K. Pandya; R. Singh (pp. 578-583).

► ZnO thin films and nanorods were synthesized on ITO and Si substrate. ► Electrolyte concentration dependent structural and optical properties have been studied. ► Crystal growth direction changes along (002) by changing electrolyte concentration. ► Defects related emissions are strongly dependent on the growth conditions.ZnO thin films and nanostructures have been grown on ITO and Si (100) substrates with varying concentration of electrolyte by electrodeposition at low temperatures. The structural analysis showed an evolution of directional growth along (002) crystallographic plane with the change of electrolyte concentrations. The peak position of defect-related bands depends upon the electrolyte concentration, and at higher molar concentration the dominant luminescent center corresponds to green emission. Furthermore, the nature of substrate also contributes to the origin of the different luminescent center. These results demonstrate that the electrolyte concentration and choice of substrate can tune the optical properties of ZnO thin films and nanostructures.

Keywords: ZnO; Electrodeposition; Molar concentration; Photoluminescence

First-principles calculations on Mg/Al₄C₃ interfaces by K. Li; Z.G. Sun; F. Wang; N.G. Zhou; X.W. Hu (pp. 584-589).

► We study Al₄C₃ slabs and Mg(0002)/Al₄C₃(0001) interfaces with a DFT-GGA method. ► C-terminated Al₄C₃(0001) slabs is more active than that of Al-terminated slabs. ► C-terminated “OT” structure is the most stable Mg(0002)/Al₄C₃(0001) interface. ► Interfacial energy of Mg/Al₄C₃ interfaces do not depend on Al chemical potential. ► Al₄C₃ particle is effective heterogeneous nucleation substrate for α-Mg.In order to explore the interfacial structure of Mg/Al₄C₃ interface and clarify the heterogeneous nucleation potential of Al₄C₃ particles in Mg melt. The atomic structure, bonding, and interfacial energy of Mg/Al₄C₃ interfaces were studied by first-principles calculations to analyze the sequence of Mg atoms onto the surface of Al₄C₃ (0001) slab. Surface energy calculations show that the outmost layer of Al₄C₃ free surface having a preference of C atom termination. And polar covalent/ionic mixed bonds are formed across interface during the combination of Mg atoms with C-terminated Al₄C₃ surface. The calculated interfacial energy of Mg/Al₄C₃ interface is much smaller than that between α-Mg and magnesium melts, proving the excellent nucleation potency of Al₄C₃ particles for α-Mg grains from interfacial atomic structure and atomic bonding energy considerations.

Keywords: First-principles calculation; Interface; Heterogeneous nucleation; Al; ₄; C; ₃; Magnesium alloys; Grain refining

Alkali-hydrothermal synthesis and characterization of W-MCM-41 mesoporous materials with various Si/W molar ratios by Hai-Yan Wu; Xiao-Li Zhang; Chun-Yan Yang; Xi Chen; Xiu-Cheng Zheng (pp. 590-595).

Display Omitted► W-MCM-41 mesoporous materials were directly prepared and characterized. ► The catalytic performance for cyclohexene oxidation was studied. ► W-MCM-41 material was approved to be a very efficient catalyst.W-MCM-41 mesoporous materials were directly synthesized via an alkali-hydrothermal method and characterized by using various techniques. The effect of different Si/W molar ratios in the gels on the structure and catalytic performance in cyclohexene oxidation was comparatively investigated in details. The results showed that the as-prepared materials retained good mesoporous structure and the one prepared with Si/W=40 displayed the best catalytic properties.

Keywords: W-MCM-41; Alkali-hydrothermal process; Structure characterization; Cyclohexene oxidation

Investigation of morphology, structure and composition of biomass-oil soot particles by Enzhu Hu; Xianguo Hu; Tianxia Liu; Yiming Liu; Ruhong Song; Yazhou Chen (pp. 596-603).

► Both particles of the biomass-oil soot and carbon black contained the same elements and had the same spherical shapes with average diameters of 50 and 40nm, respectively. ► There are same oxygen functional groups (CO, OCO and COC) on the surfaces of both particles, except that the COH appears on the surface of biomass soot particles. ► The two carbon materials virtually had indistinguishable perturbed graphitic or turbostratic internal structures.Biomass-oil soot (BS) particles were characterized by a range of analytical techniques. A comparative analysis with commercial carbon black (CB), a surrogate for diesel soot particles, was carried out. The experimental results showed that the morphologies of BS and CB particles were both spherical, with average diameters of 50 and 40nm, respectively. There were only a few differences between the elemental composition of BS and CB. The groups (CO, OCO and COC) were presented on the surfaces of CB and BS. Moreover, it was also found that COH group was appeared on the surface of BS. BS contained more acidic and basic sites than CB, which was ascribed to the complex mixtures of biomass oil. Both BS and CB had virtually indistinguishable perturbed graphitic or turbostratic internal structures. Thus, CB can be a potential alternative to evaluate the aggregation and tribological behavior of BS in lubricating oils.

Keywords: Biomass-oil; Soot particles; Carbon black; Morphology; Structure; Composition

The influence of post-annealing treatment on the wettability of Ag⁺/Na⁺ ion-exchanged soda-lime glasses by Ahmad Razzaghi; Maniya Maleki; Yashar Azizian-Kalandaragh (pp. 604-610).

Display Omitted► Ion exchanged Ag⁺/Na⁺ soda lime glasses were annealed in different temperatures and times. ► Silver oxide nano-patterned layers were formed on the surfaces, which changed their wettability from hydrophilic to hydrophobic. ► The best condition for attaining the most hydrophobic surface was deduced. ► Contact angle changes were explained due to the surface roughness and the area fraction of the coated layers.In this paper, the effect of thermal annealing and the duration of ion-exchange on the wetting parameters of the Ag⁺/Na⁺ ion-exchanged glasses have been reported. The analysis of wetting angle in different post-annealing temperatures shows that the wetting angle is increased by increasing the annealing temperature. The wetting parameters of Ag⁺/Na⁺ ion-exchanged glasses at different ion-exchanged periods of time have been also investigated. Scanning electron microscopy (SEM), UV–Visible spectroscopy and Fourier transform infrared (FTIR) spectroscopy have been used for determination of surface morphology and composition analysis of the prepared samples. The results of SEM show changes in the surface of the samples for different post-annealing temperatures. The optical characterization using UV–Vis spectroscopy shows an increase in the intensity of the absorption peak with increasing the ion-exchange duration. The FTIR spectroscopy confirms the formation of silver oxide material on the surface of Ag⁺/Na⁺ ion-exchanged glasses.

Keywords: Ion-exchange method; Wetting phenomena; Ag nanoparticles; UV–Vis spectroscopy

The improvement of wave-absorbing ability of silicon carbide fibers by depositing boron nitride coating by Fang Ye; Litong Zhang; Xiaowei Yin; Yongsheng Liu; Laifei Cheng (pp. 611-616).

► BN coating was deposited on SiC fibers by CVI. ► After coated by BN, the tensile strength of SiC fiber bundles increased by 1.389%. ► After coated by BN, SiC fiber laminates had a great improvement of wave-absorbing ability with a minimum RC of −16.41dB at 15.38GHz.This work investigated electromagnetic wave (EMW) absorption and mechanical properties of silicon carbide (SiC) fibers with and without boron nitride (BN) coating by chemical vapor infiltration (CVI). The dielectric property and EM shielding effectiveness of SiC fiber bundles before and after being coated by BN were measured by wave guide method. The EM reflection coefficient of SiC fiber laminates with and without BN coating was determined by model calculation and NRL-arc method, respectively. Tensile properties of SiC fiber bundles with and without BN coating were tested at room temperature. Results show that SiC fibers with BN coating had a great improvement of EMW absorbing property because the composites achieved the impedance matching. BN with the low permittivity and dielectric loss contributed to the enhancive introduction and reduced reflection of EMW. The tensile strength and Weibull modulus of SiC fiber bundles coated by BN increased owing to the decrease of defects in SiC fibers and the protection of coating during loading.

Keywords: SiC fibers; BN coating; Dielectric property; Impedance matching; Tensile strength

Synthesis and characterization of AgI nanoparticles in β-CD/PAN nanofibers by electrospinning method by Haiou Liang; Chunping Li; Jie Bai; Lijuan Zhang; Liping Guo; Yarong Huang (pp. 617-620).

► Novel AgI–β-CD/PAN composite nanofibers were prepared. ► The methods combined electrospinning technology with the reaction of solid–liquid. ► AgI nanoparticles were dispersed on surface of composite nanofibers.AgI nanoparticles/β-cyclodextrin (β-CD)/polyacrylonitrile (PAN) composite nanofibers film were prepared via a new route which combined electrospinning technology with the reaction of solid–liquid process. In this article, AgI nanoparticles were successfully prepared in β-CD/PAN nanofibers which contained different concentration β-CD by the new route. Firstly, the AgNO₃–β-CD/PAN nanofibers were obtained via electrospinning method, then put the nanofibers into the solution of potassium iodide to prepare AgI–β-CD/PAN nanofibers. The morphology and structure of the composite nanofibers and nanoparticles have been investigated by scanning electron microscopy (SEM) and transmission electro microscopy (TEM). The existence of the AgI nanoparticles was proved by X-ray photoelectron spectroscopy (XPS) and X-ray diffractometer (XRD) patterns. The results of various characterizations indicated that the sample of AgI–β-CD (2wt%)/PAN have the optimum morphology and structure.

Keywords: Electrospinning; AgI nanoparticles; Composite nanofibers

The in situ preparation of novel α-Fe₂O₃ nanorods/CNTs composites and their greatly enhanced field emission properties by Fan Guo; Yun Ye; Zunxian Yang; Chunyan Hong; Liqin Hu; Chaoxing Wu; Tailiang Guo (pp. 621-626).

► Fe₂O₃ nanorods/CNTs nanocomposites has been researched in this article. ► The composites have been formed by dropping CNTs on iron sheet followed oxidation. ► The CNTs absorbed and wrapped outside of Fe₂O₃ nanorods, forming many CNT tips. ► The composites exhibit very good field emission performances.Novel field emitters with α-Fe₂O₃ nanorods/CNTs composites were simply prepared by dipping the iron into the oxalic acid solution, drop-coating CNTs to the iron substrate followed by in situ thermal oxidation. The surface morphology of the products has been characterized by scanning electron microscope (SEM). And further the composition was analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The results of SEM, XRD and XPS showed that CNTs have been homogenously dispersed and partly wrapped on α-Fe₂O₃ nanorods. α-Fe₂O₃ nanorods/CNTs composites had exhibited greatly enhanced field emission properties with low turn-on field (about 1.211V/μm), and high field enhancement factor of 8658. Therefore, the α-Fe₂O₃ nanorods/CNTs composites are promising field emitters for field emission applications.

Keywords: α-Fe; ₂; O; ₃; nanorods/CNTs composites; In situ preparation; Field emission

Effects of different fluorination routes on aramid fiber surface structures and interlaminar shear strength of its composites by Jie Gao; Yunyang Dai; Xu Wang; Jieyang Huang; Jin Yao; Jin Yang; Xiangyang Liu (pp. 627-633).

Display Omitted► The ILSS is improved by appropriate fluorination routes. ► The inappropriate fluorination route sharply decreases the ILSS. ► Different fluorination routes lead to different fiber surface morphology structures. ► Physisorbed water accelerates chain scission and leads to formation of unstable structures. ► These unstable structures became weak interface between the fiber and matrix.Poly-p-phenylene-benzimidazole-terephthalamide (PBIA) fiber was surface modified by direct fluorination under three different routes. The fiber was dried under vacuum to remove physisorbed water trapped on it and then fluorinated by the fluorine and oxygen gases or by the fluorine gas only. Results show that the interlaminar shear strength (ILSS) value of these two kinds of fluorinated fiber reinforced epoxy resin was 43.9MPa and 51.0MPa, which was improved about 14.0% and 32.5% compared with that of the virgin fiber (38.5MPa), respectively. In the third route, the fiber was fluorinated by the fluorine and oxygen gases without removing physisorbed water, and the ILSS value decreased for nearly 31.2%, i.e. from 38.5MPa to 26.5MPa. X-ray photoelectron spectroscopy (XPS) showed that oxygen-containing and fluorine-containing chemical groups were introduced onto the fiber surface after fluorination, providing a stronger chemical bonding to polymeric matrices. Scanning electronic microscopy (SEM) indicated that the surface morphology of the fluorinated PBIA fiber varied with the different fluorination routes. A mass of compact micro groove structures was formed by the route that the fiber was dried to remove physisorbed water and then fluorinated with fluorine gas only. And these structures would markedly improve the ILSS of the composites. But, a mass of unstable flake surface structures was formed by the route that the fiber was fluorinated with the fluorine and oxygen gases without removing physisorbed water. And these structures would be the weak interface between the fiber and matrix and decrease the ILSS, even a lot of polar chemical groups were bonded onto the fiber surface as well.

Keywords: PBIA; Surface modification; Direct fluorination; Interlaminar shear strength

Gas-phase noncovalent functionalization of carbon nanotubes with a Ni(II) tetraaza[14]annulene complex by Vladimir A. Basiuk; Laura Verónica Henao-Holguín; Edgar Álvarez-Zauco; María Bassiouk; Elena V. Basiuk (pp. 634-647).

Display Omitted► NiTMTAA was deposited onto carbon nanotubes from vapor phase. ► NiTMTAA–carbon nanotube hybrids were studied by different instrumental techniques. ► Molecular modeling found preferable orientations and distribution of NiTMTAA on nanotubes.The noncovalent functionalization of carbon nanotubes (CNTs) with aromatic polyazamacrocyclic compounds, based on π–π-interactions, keeps the intrinsic electronic structure of CNTs totally intact and allows for combining unique properties of the two interacting components. In addition to porphyrins and phthalocyanines, there are other, simpler compounds exhibiting similar properties, potentially useful for photovoltaic, catalytic and electrochemical applications: for example, tetraaza[14]annulenes. Many of them are highly thermally stable, which makes it possible to employ physical vapor deposition for the preparation of macrocycle–nanotube hybrids. One of such compounds is Ni(II) complex of 5,7,12,14-tetramethyldibenzo-1,4,8,11-tetraazacyclotetradeca-3,5,7,10,12,14-hexaene (also called Ni(II)-tetramethyldibenzotetraaza[14]annulene, or NiTMTAA for simplicity). In the present work, we attempted the noncovalent functionalization of both single-walled and multi-walled CNTs with NiTMTAA in the gas phase at two selected temperatures of 220 and 270°C, which does not require the use of organic solvents and therefore can be considered as ecologically friendly. The nanohybrids obtained were characterized by means of scanning and transmission electron microscopy, energy dispersive X-ray, Fourier-transform infrared and Raman spectroscopy, as well as thermogravimetric analysis. An additional insight into the structure of adsorption complexes of NiTMTAA on CNTs was provided from density functional theory and molecular mechanics calculations.

Keywords: Tetraaza[14]annulene; Ni(II) complex; Carbon nanotubes; Noncovalent functionalization; Experimental characterization; Theoretical DFT calculations; Molecular mechanics

Self-assembled monolayers assisted thin film growth of aluminum doped zinc oxide by spray pyrolysis method by Muluken Aklilu; Yian Tai (pp. 648-654).

Display Omitted► Highly c-axis oriented AZO films have been prepared by spray pyrolysis technique on SAM modified substrates. ► With SAM modified substrates the crystal structure of the films is significantly improved and the grain size is increased. ► The average transmittance in the visible region varies from 85% to more than 95% for films deposited on SAM modified substrate. ► Concentration of structural defects and resistivity decreases for films deposited on SAM modified substrates.In this work, aluminum doped zinc oxide (AZO) were deposited on pristine and self-assembled monolayer (SAM) modified glass substrates by chemical spray pyrolysis technique. The measurements of different parameters showed that modifying the surface of the glass substrates with the different SAMs resulted in excellent nucleation sites for the crystal growth of the AZO thin film. Among the different functional groups, SAMs withCH₃ terminal group improves the quality of the film remarkably, while the other groups improve the quality moderately. From the results we observed that our finding suggests a novel approach of improving the quality of AZO films deposited by spray pyrolysis technique.

Keywords: TCO; AZO; Doping; SAM; Spray pyrolysis

Visible-light photocatalytic degradation of methylene blue with Fe doped CdS nanoparticles by Ruby Chauhan; Ashavani Kumar; Ram Pal Chaudhary (pp. 655-660).

3, 5 and 10mol% Fe doped CdS nanopowders show strong photocatalytic activity under visible light irradiation, which was observed by measuring the degradation of methylene blue. The optimum Fe/Cd ratio was observed to be 3mol% for photocatalytic applications. In contrast, little degradation was observed for the pure CdS powder.Display Omitted► Fe doped CdS nanoparticles were synthesized by a chemical precipitation method. ► With increased the Fe doping concentration, the position of the Raman bands shifted towards higher wavenumbers and their intensities decreased drastically. ► Optical measurements indicated that the absorption edge shifted towards the longer wavelength side in Fe doped CdS nanoparticles. ► Fe doped CdS nanoparticles show excellent Photocatalytic activity under visible light irradiation. ► Optimum concentration of Fe doped CdS was observed to be 3mol% for photocatalytic applications.Fe doped CdS nanoparticles (Cd1−_xFe_xS; where x=0.00, 0.03, 0.05 and 0.10) were synthesized by a chemical precipitation method. The synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), Raman and UV–vis spectrometer. The XRD and TEM measurements show that the size of crystallites is in the range of 2–10nm. With increased the Fe doping concentration, the position of the Raman bands shifted towards higher wavenumbers and their intensities decreased drastically. Optical measurements indicated that the absorption band edge shifted towards longer wavelength upon Fe doping. Direct allowed band gap of undoped and Fe doped CdS nanoparticles measured by UV–vis spectrometer were 2.3 and 2.2eV at 100°C, respectively. Photocatalytic activities of CdS and Fe doped CdS were evaluated by irradiating the solution of methylene blue (MB) and sample under visible light. It was found that Fe doped CdS bleaches MB much faster than undoped CdS upon its exposure to the visible light. The optimum Fe/Cd ratio was observed to be 3mol% for photocatalytic applications. In contrast, little degradation was observed for the pure CdS powder.

Keywords: Nanoparticle; UV–vis spectrometer; Scanning electron microscope; Transmission electron microscope; Photocatalysis

In situ RHEED study of epitaxial gold nanocrystals on TiO₂ (110) surfaces by X. Chen; W.P. Gao; S. Sivaramakrishnan; H.F. Hu; J.M. Zuo (pp. 661-666).

► Transformation from randomly oriented Au nanoparticles to epitaxial Au nanocrystals upon annealing is revealed by in situ RHEED. ► Significant Au nanocrystal crystallization occurs at >500°C annealing temperatures for nanoparticles that are of ∼2nm in diameter. ► The NCs are faceted as evidenced by the shape of RHEED diffraction spots and electron imaging. ► High quality RHEED patterns allow the measurement of thermal expansion coefficients and Debye-Temperature of Au nanocrystals.We report a study of epitaxial gold nanocrystals (NCs) on rutile (TiO₂ (110)) surfaces using reflection high energy electron diffraction (RHEED) and ex situ electron imaging. The NCs are determined by RHEED have almost pure (111) out-of-plane epitaxy with the twin in-plane orientation relationships of [–110] Au || [001] TiO₂ and [1−10] Au || [001] TiO₂. The epitaxial Au NCs are formed by thermal annealing after depositing 0.1–0.4nm nominal thick Au on TiO₂. In situ RHEED monitoring shows that significant Au NC crystallization occurs at >500°C annealing temperatures for nanoparticles that are of ∼2nm in diameter. The NCs are faceted as evidenced by the shape of RHEED diffraction spots and electron imaging. The sharpness of the epitaxial Au RHEED diffraction spots with ∼0.55nm⁻¹ FWHM allows a measurement of thermal properties of Au/TiO₂, such as thermal expansion and Debye temperature of Au NCs on TiO₂.

Keywords: in situ RHEED; Epitaxy; Gold nanoparticles; Titanium oxide; Nanocrystals

A study on in vitro and in vivo bioactivity of HA/45S5 composite films by pulsed laser deposition by D.G. Wang; C.Z. Chen; Q.S. Ma; Q.P. Jin; H.C. Li (pp. 667-674).

► High substrate temperature improves the properties of the HA/BG composite PLD film. ► Comparative study of the bioactivity of the amorphous film and crystal film. ► The amorphous film has faster dissolution rate and reprecipitation rate in SBF solution than crystal film. ► The 600°C film is more suitable to serve as clinical application than the 200°C film.HA/45S5 composite films were deposited by pulsed laser, the crystalline phases, microstructure and bonding configurations of the films were studied by XRD, SEM and FTIR respectively, and the film-to-substrate adhesion was investigated by micro-scratch testing. In addition, the in vitro and in vivo assays were carried out.The results showed that the crystallinity and the adhesive strength of the films increased with the increase of the substrate temperature. The film deposited with the substrate temperature of 200°C is amorphous, while crystalline HA and β-TCP were detected in the film deposited at 600°C. The in vitro test indicates that the amorphous film has faster dissolution rate and reprecipitation rate, which implies that this film has better bioactivity than the crystalline film. However, the in vivo test suggested that the 600°C film was more suitable to serve as clinical application than the 200°C film, because new bone tissue grew better onto the 600°C film surface than onto the 200°C film surface when they were implanted in the rabbit shin bones.

Keywords: Hydroxyapatite; 45S5 bioglass; Bioactivity; Composite film; Pulsed laser deposition

Combined modification of a TiO₂ photocatalyst with two different carbon forms by Alejandro Ansón-Casaos; Ignacio Tacchini; Andrea Unzue; M. Teresa Martínez (pp. 675-684).

► We synthesized a new ternary SWCNT/C/TiO₂ nanocomposite photocatalyst. ► Interactions between carbon and titanium were characterized by XPS and IR. ► The ternary photocatalyst showed a substantial activity under visible light. ► The different carbon forms induced different photocatalytic mechanisms.Hydrothermally synthesized titanate nanotubes were carbon-doped through a thermal treatment in the presence of glucose followed by blending with single-walled carbon nanotubes (SWCNTs). A series of TiO₂-based materials was prepared with various initial glucose contents and two SWCNT types, resulting in total carbon contents from 0.3wt.% to nearly 26wt.%. Electron microscopy observations indicated that titanate nanotubes were converted into nanorods during the thermal treatment, and X-ray diffraction patterns confirmed that all the treated materials mostly consisted of anatase TiO₂. Glucose pyrolysis caused changes in the infrared and X-ray photoelectron spectra of the titania material, indicating an interaction between the inserted carbon atoms and titanium atoms. Raman spectra of SWCNT/C/TiO₂ hybrids showed characteristic bands of both the SWCNT and anatase TiO₂ phases. SWCNT/C/TiO₂ multicomponent materials demonstrated substantially better photocatalytic activities than P25 TiO₂ for methylene blue degradation under visible light irradiation. Independently from its origin, the presence of carbon caused a strong increase in the TiO₂ visible light absorption. However, the results obtained with the C/TiO₂ and SWCNT/C/TiO₂ photocatalysts clearly showed different photocatalysis mechanisms depending on the carbon form.

Keywords: Titanium dioxide; Nanorod; Carbon nanotubes; Nanocomposite; Photocatalysis; Visible

Facile hydrothermal synthesis of Bi₂WO₆ microdiscs with enhanced photocatalytic activity by Xinjun Wang; Linling Chang; Jinrui Wang; Ningning Song; Huanli Liu; Xiaoli Wan (pp. 685-689).

► Bi₂WO₆ microdiscs were synthesized via acetic acid-assisted hydrothermal process. ► The Bi₂WO₆ microdiscs were composed of numerous square nanoplates. ► The possible formation mechanism for the growth of microdiscs was discussed. ► Bi₂WO₆ microdiscs exhibit excellent photocatalytic activity.Bi₂WO₆ microdiscs were synthesized via acetic acid-assisted hydrothermal process. The results revealed that the microdiscs were composed of numerous square nanoplates, and the nanoplates were stacked together through a side-by-side manner. The possible formation mechanism for the growth of microdiscs was discussed. The photocatalytic activity of the Bi₂WO₆ samples under solar-light irradiation was evaluated for degradation Rhodamine B (RhB). The as-prepared Bi₂WO₆ microdiscs exhibited excellent photocatalytic activity, and nearly 98% of RhB was degraded within 120min, which was nearly 9 times than that of the products prepared by traditional solid-state reaction. The excellent photocatalytic performance can be attributed to porous structure and the higher surface area.

Keywords: Bi; ₂; WO; ₆; Acetic acid; Hydrothermal; Microdiscs; Photocatalysis

Surface recrystallization of a gamma-TiAl alloy induced by shot peening and subsequent annealing treatments by Wenyue Zhao; Yuzhuo Liu; Lei Liu; Youxing Yu; Yue Ma; Shengkai Gong (pp. 690-696).

► Fine recrystallized grains are achieved in shot-peened surface after annealing. ► Annealing at 900°C for 6–12h and lamellar orientation angle of closed to 45° are favorable. ► Growth of lamellar fragment via phase boundary bulging is the microscopic mechanism.Fine-grained recrystallization microstructure induced by shot peening and subsequent annealing treatment was achieved in the surface of Ti–48Al–2Cr–2Nb alloy. Annealing treatment at 900°C for 6–12h and the lamellar orientation angle of close to 45° are the most favorable conditions for recrystallization. The rotation, dissolution and invasion of the lamellae fragments into the adjacent normal lamellae under the driving force of residual deformation energy with phase boundary bulging mechanism is considered to be the most possible microscopic approach of the recrystallization.

Keywords: Titanium aluminides; Recrystallization; Microstructure; Electron microscopy

Template-confined dewetting of Au and Ag nanoscale films on mica substrate by F. Ruffino; M.G. Grimaldi (pp. 697-706).

Display Omitted► Micrometric template-confined nanometric thickness Au and Ag films are deposited on mica. ► The thermal-induced dewetting process of the template-confined Au and Ag films on mica is studied. ► Three stages of the dewetting process of Au and Ag films on mica are identified. ► Activation energies for the dewetting process of Au and Ag films on mica are quantified. ► Patterned arrays of Au and Ag nanoparticles on mica are obtained after the dewetting process of the films.In this work we report about the template-confined dewetting of Au and Ag nanoscale films on mica substrate toward surface patterning control. In this approach, the Au and Ag surface pattern order, on the mica substrate, is established by the template confined deposition on a micrometric scale, while the dewetting process is induced by thermal process. We expose the results of our studies on the dewetting kinetics both for Au and Ag on mica consisting, in particular, in the identification of three regimes of the process: a regime I in which holes nucleation in the Au and Ag films occurs (characterized by 130 and 72meV activation energies, respectively); a regime II consisting in the retraction phenomenon of the films limited by the Au or Ag surface diffusion; a regime III corresponding to the merging of the dewetted fronts of holes that come close to each other (and formation of Au and Ag nanoparticles as a consequence). Correspondently, the ordered surface patterns realized for the Au and Ag arrays of nanostructures on a large scale (micrometric) can be changed and controlled for specific applications.

Keywords: Au; Ag; Mica; Template-confined dewetting; Patterning

Electrochemical growth and characterization of CdTe nanorod arrays by Qian Li; Lecheng Tian; Kailin Chi; Haibin Yang; Meiling Sun; Wuyou Fu (pp. 707-711).

The straight one-dimensional CdTe nanorod arrays were electrosynthesized on ITO substrate from an acidic aqueous solution of CdSO₄ and Na₂TeO₃. XRD results show that the growth of films are highly preferential with (1 1 1) orientation.Display Omitted► High-density vertically CdTe nanorod arrays were achieved on ITO glass substrate by a convenient electrodeposition method. ► The growth temperature is room temperature. ► The photocatalytic were studied upon UV irradiation. ► CdTe nanorod arrays show superior photocatalytic activity.The straight one-dimensional CdTe nanorod arrays on indium tin oxide coated glass substrate with high purity have been synthesized using a rapid and convenient electrodeposition method. The electrodeposited thin ﬁlms were studied and investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV–vis absorption spectroscopy. The structural and optical studies revealed that ﬁlms are possess sphalerite phase. The device based on the aligned array-on-ITO conﬁguration demonstrates excellent photoresponse to the visible light, which is ascribed to the large absorption coefﬁcient of the material and also suggests good electronic structure quality of the nanorods.

Keywords: Electrodeposition; CdTe; Nanorod arrays; Photovoltaic

Influence of SiO₂ layer thickness on plasmon enhanced upconversion in hybrid Ag/SiO₂/NaYF₄:Yb, Er, Gd structures by J. Shen; Z.Q. Li; Y.R. Chen; X.H. Chen; Y.W. Chen; Z. Sun; S.M. Huang (pp. 712-717).

► We reported upconversion (UC) luminescence in Ag/SiO₂/UC nanorods structures. ► Ag nanoparticles were formed by annealing the sputtered Ag nano-films. ► SiO₂ spacer layers were prepared by RF sputtering. ► Effect of nano-metal and SiO₂ interface on the UC properties was studied. ► Switching between photoluminescence quenching and enhancement was demonstrated.We report enhanced up-conversion (UC) photoluminescence (PL) in Ag nanoparticles/SiO₂/NaYF₄: Yb, Er, Gd film sandwiched structures. The effect of SiO₂ layer thickness on the up-converting optical properties in the sandwiched system was investigated. The UC emission enhancement shows a pronounced distance dependence for the silica spacer layer thickness below 20nm. The UC emission spectrum of the hybrid structured sample shows a continuous increase in intensity as the thickness of the SiO₂ layer increases from 0nm to 15nm, but displays a quick decrease when the thickness of the SiO₂ layer increases further from 15nm. Time-resolved photoluminescence spectroscopy reveals that the fluorescence lifetimes are reduced both for green and red emissions. PL spectroscopy and excitation power studies also show that Ag nanoparticles modified the UC process in this sandwiched structure. We demonstrate switching between PL quenching and enhancement by varying the silica interface thickness. This approach allows us to perform a quantitative analysis of the effect of a metal on the UC nanorods PL intensity.

Keywords: 78.67.Bf; 73.22.Lp; 78.55.Hx; 68.43.Mn; 88.40.hjUpconversion nanomaterial; Plasmon-enhancement; Yb; ³⁺; -Er; ³⁺; -Gd; ⁺³; codoped NaYF; ₄; Sputtering

Photoelectrochemical behavior of mixed ZnO and GaN (ZnO:GaN) thin films prepared by sputtering technique by Sudhakar Shet; Yanfa Yan; Nuggehalli Ravindra; John Turner; Mowafak Al-Jassim (pp. 718-721).

► Photoelectrochemical behavior of mixed ZnO and GaN (ZnO:GaN) thin film deposited using sputtering technique. ► Badgap reduction of (ZnO:GaN) thin films by varying the O₂ mass flow. ► Enhanced crystallinity and visible light absorption resulted in improved photoresponseo.Mixed zinc oxide and gallium nitride (ZnO:GaN) thin films with significantly reduced bandgaps were synthesized by using zinc oxide and gallium nitride target at 100°C followed by post-deposition annealing at 500°C in ammonia for 4h. All the films were synthesized by RF magnetron sputtering on Fluorine-doped tin oxide-coated glass. We found that mixed zinc oxide and gallium nitride (ZnO:GaN) thin films exhibited significantly reduced bandgap, as a result showed improved PEC response, compared to ZnO thin film. Furthermore, mixed zinc oxide and gallium nitride (ZnO:GaN) thin films with various bandgaps were realized by varying the O₂ mass flow rate in mixed O₂ and N₂ chamber ambient.

Keywords: Bandgap; Sputter; Ambient; Photoelectrochemical; ZnO; GaN

Core–shell heterostructures of SnM (M=(Fe, Ni, and Cr) or Cu) alloy nanowires @ CNTs on metallic substrates by Yu Zhong; Yong Zhang; Mei Cai; Michael P. Balogh; Ruying Li; Xueliang Sun (pp. 722-727).

Display Omitted► Sn alloy nanowires encapsulated in carbon nanotubes directly grew on metallic substrates. ► Alloy elements were supplied by metallic substrates to nanowire growth. ► The morphology, structure and composition of products depended on the surface conditions of substrates. ► The core–shell structures formed in one-step CVD method.Sn alloy nanowires encapsulated in carbon nanotubes (SnM (M=(Fe, Ni, and Cr) or Cu) @ CNTs) were prepared in situ by a chemical vapor deposition (CVD) method, in which Sn came from a vaporized precursor while the alloy elements were supplied by the substrate. The heterostructures were grown on two types of substrates including stainless steel with high catalytic effectiveness and Cu substrates with low catalytic effectiveness for generating graphite layers, respectively. Pure Sn powder and C₂H₄ were employed to provide Sn and carbon precursors. The products were investigated by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy–energy dispersive X-ray spectroscopy (STEM–EDS) mapping. The morphology, structure and composition of the nanomaterials depended significantly on the surface conditions of the substrates. While SnCu alloy nanowires encapsulated in carbon nanotubes were grown on the Cu substrate, carbon nanotubes filled with alloy nanowires and porous carbon fibers decorated internally with alloy particles were observed on the stainless steel substrate. The growth mechanisms of the heterostructures were proposed.

Keywords: Core–shell structure; Alloy nanowires; Metallic substrates

Influence of the hydroxylation of γ-Al₂O₃ surfaces on the stability and growth of Cu for Cu/ γ-Al₂O₃ catalyst: A DFT study by Jingrui Li; Riguang Zhang; Baojun Wang (pp. 728-736).

Display Omitted► The stability of Cu_n( n=2–4) on γ-Al₂O₃(110) is stronger than that on (100) surface. ► Surface hydroxyls is beneficial to the stability of γ-Al₂O₃(110) surface. ► The growth of Cu_n on γ-Al₂O₃(110) is more favorable than that on (100) surface. ► The presence of surface hydroxyls reduces the stability and growth of Cu_n( n=2–4). ► The support reduces the growth ability of Cu_n( n=2–4) and inhibit the aggregations.The interaction of Cu_n( n=1–4) cluster with the dehydrated γ-Al₂O₃(110), hydrated γ-Al₂O₃(110) and dehydrated γ-Al₂O₃(100) surfaces has been systematically investigated to illustrate the influence of the hydroxylation of γ-Al₂O₃ surfaces on the stability and growth of Cu for Cu/ γ-Al₂O₃ catalyst. Here, we present the main results obtained by the density functional theory together with slab model calculations. Our results show that the adsorption of Cu_n( n=2–4) cluster on the γ-Al₂O₃(110) surface is more stable than that on the γ-Al₂O₃(100) surface, for the single Cu atom, the reverse becomes true. For the γ-Al₂O₃(110) surface, the adsorption of Cu_n( n=2–4) cluster on the dehydrated surface is more stable than that on the hydrated surface due to the presence of the surface hydroxyls, however, the adsorption of the single Cu atom on the hydrated surface is more stable than that on the dehydrated surface due to the larger Cu–support interaction energy. On the other hand, compared to the γ-Al₂O₃(100) surface, the γ-Al₂O₃(110) surface is more favorable for the growth of Cu_n clusters, in which the presence of surface hydroxyls reduces the growth ability of Cu_n clusters.

Keywords: Keyword; Cu; _n; (; n; =; 1–4) cluster; γ; -Al; ₂; O; ₃; Stability; Growth; Surface hydroxyl; Density functional theory

The study of the substrate temperature depended growth properties of microcrystalline silicon films deposited by VHF-PECVD method by Yongsheng Chen; Xiping Chen; Xiuli Hao; Jingxiao Lu; Shi-e Yang (pp. 737-740).

► The effect of substrate temperature on the properties of μc-Si:H films was simulated. ► Good agreements were obtained between the model and experimental results. ► The increase of the grain size is caused by the increase of the fraction of the surface dangling bonds. ► The temperature depended growth properties of facets may be responsible for the observed variations.In this paper, we have measured the temperature depended growth properties of hydrogenated microcrystalline silicon (μc-Si:H) films, prepared by very high frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) from SiH₄ and H₂ gas mixtures. And, a 1D plasma model coupled with a well-mixed reactor model is used to simulate the growth process, in which concentrations of gas phase species, the crystalline orientation, the hydrogen content and the deposition rate are calculated. It suggests that the increasing surface fraction of the dangling bonds with the increase of substrate temperatures is responsible for the increase in the grain sizes. At the same time, the observed variations of the X-ray-diffraction intensities and the deposition rates of the films with temperature result from the differences in the growth rates of the facets.

Keywords: Hydrogenated microcrystalline silicon film; Plasma enhanced chemical vapor deposition; Simulation; Substrate temperature

Effect of substrate on evaluation of the photocatalytic activity of TiO₂ nanocrystals with exposed {001} facets by Hengpeng Ye; Shaoming Lu (pp. 741-745).

► Microwave-assisted synthesis of high-energy TiO₂ nanocrystals at 200°C for 60min. ► The percentage of exposed {001} facets can be tuned by adjusting the volume of water. ► Substrate is important in evaluation of the photo-reactivity of high-energy TiO₂.There are increasing debates on the high photocatalytic activity of TiO₂ nanocrystals with exposed high-energy facets. In this paper, the effect of substrate on evaluation of the photocatalytic activity of anatase TiO₂ nanocrystals with exposed {001} facets was studied. Surface-clean anatase TiO₂ nanocrystals with exposed {001} facets were prepared by a microwave-assisted hydrothermal route in a Ti(OC₄H₉)₄-HF-H₂O mixed solution (both the amount of Ti(OC₄H₉)₄ and HF were 60mmol). It was found that the percentage of exposed {001} facets is negatively correlated with the molar ratio of water to titanium/or fluoride ( x). With increasing x from 0 to 21, the percentage of exposed {001} facets steadily decreases from 81% to 36%. Anionic dye Brilliant Red X-3B (X3B) and cationic dye Methylene Blue (MB) were used as probes to evaluate the relative photocatalytic activity of the prepared TiO₂ samples. TiO₂ nanocrystals with exposed 40% {001} facets at x=15 shows the highest photocatalytic activity in degradation of MB. However, an overwhelmingly better performance of TiO₂ sample with exposed 49% {001} facets at x=9 was found among all the photocatalysts in photocatalytic degradation of X3B, reflecting the importance of substrate on evaluation the photocatalytic activity of high-energy TiO₂ nanocrystals.

Keywords: Titanium dioxide; High-energy facets; Photocatalytic degradation; Microwave-assisted hydrothermal reaction

Y₂O₃–Lu₂O₃ co-doped molybdenum secondary emission material by Fan Yang; Jinshu Wang; Wei Liu; Xiang Liu; Meiling Zhou (pp. 746-750).

► A new kind of cathode has been successfully obtained. ► Y₂O₃–Lu₂O₃–Mo cathode exhibits excellent secondary emission performance. ► The experimental results can be well explained by the emission mechanism presented in this work.A new kind of RE₂O₃–Mo cathodes co-doped with Y₂O₃ and Lu₂O₃ were prepared by a solid–liquid method combined with the spark plasma sintering technique. The secondary electron emission property and secondary emission mechanism of the cathode have been studied. The results show that Y₂O₃–Lu₂O₃ co-doped Mo cathode exhibits better secondary emission property than single Y₂O₃ doped molybdenum cathode, and the maximum secondary emission yield ( δ_max) can reach 4.616 after being activated at 900°C_b. The Y₂O₃–Lu₂O₃ co-doped Mo cathode has high penetration depth of primary electrons and moderate escape depth of secondary electrons. Furthermore, the work function of Y₂O₃–Lu₂O₃–Mo cathode (2.41eV) is lower than that of Y₂O₃–Mo cathode (3.59eV). These phenomena are responsible for its excellent secondary emission property.

Keywords: Secondary electron emission; Y; ₂; O; ₃; –Lu; ₂; O; ₃; Cathode

Enhanced growth of highly lattice-mismatched CdSe on GaAs substrates by molecular beam epitaxy by Jyh-Shyang Wang; Yu-Hsuan Tsai; Hsiao-Hua Wang; Han-Xiang Ke; Shih-Chang Tong; Chu-Shou Yang; Chih-Hung Wu; Ji-Lin Shen (pp. 751-754).

► Zinc-blende CdSe epilayers were grown on GaAs substrate by molecular beam epitaxy. ► Surface diffusion of Cd atoms was enhanced by introducing a small amount of Te atoms. ► The improvements in structural quality and optical properties were found.This work demonstrates the improvement of the molecular beam epitaxial growth of zinc-blende CdSe on (001) GaAs substrate with a large lattice mismatch by introducing a small amount of Te atoms. Exposing the growing surface to Te atoms changes the reflection high-energy electron diffraction pattern from spotty to streaky together with (2×1) surface reconstruction, and greatly reduces the full width at half maximum of the X-ray rocking curve and increases the integral intensity of room-temperature photoluminescence by a factor of about nine.

Keywords: Zinc-blende CdSe epilayer; Molecular beam epitaxy; Te; Reflection high-energy electron diffraction; X-ray diffraction; Photoluminescence

Effect of cold work on surface reactivity and nano-hardness of alloy 800 in corroding environments by R.K. Zhu; B.T. Lu; J.L. Luo; Y.C. Lu (pp. 755-762).

► Cold work increases surface reactivity over passive surface exposed to corroding environment. ► Under cold-worked condition, surface reactivity is highly localized at the area around the fine inclusions. ► Cold-rolled material undergoes larger surface hardness loss induced by anodic dissolution. ► Cold work reduces the resistance of material to localized corrosion.In this paper, in situ scanning electrochemical microscopy (SECM) was used to investigate effect of cold work on surface reactivity of UNS N08800 alloy, and in situ nanoindentation technique was employed to measure corrosion-induced degradation of resistance to plastic deformation in surface layer. The SECM measurements indicated that cold work would cause an increase of surface reactivity, especially on surface area around non-inclusions. According to in situ nanoindentation measurements, anodic dissolution would reduce the surface hardness. This effect was enhanced by cold work.

Keywords: Plastic deformation; Steel; Scanning electrochemical microscopy; Nanoindentation

Large volume ablation of Sapphire with ultra-short laser pulses by A. Shamir; A.A. Ishaaya (pp. 763-766).

► High quality deep ablation of Sapphire using ultra-short laser pulses is demonstrated. ► Characterization of large area laser ablation in terms of pulse energy, scanning speed and scanning pattern is performed. ► Best performance is achieved at low power and low scan speed (100μJ, 90μm/s; at 1kHz). ► The process parameters and ablation depth are significantly different than those of hole drilling and line cutting.The superior optical and mechanical properties of Sapphire (Al₂O₃) are highly desirable in various opto-electronics and micro-mechanical applications. However, Sapphire's intrinsic hardness and resistance to most chemicals result in significant processing difficulties. Laser micro-machining is emerging as a promising technology, in particular, the use of ultra-short pulses for material ablation. In this work we investigate and characterize experimentally large volume ablation of Sapphire with femtosecond pulses, and compare the results to previously reported drilling and cutting experiments. We manage to identify optimized parameters for overcoming deleterious thermal effects and debris scattering, and demonstrate high quality 180μm-deep ablation of 1mm×15mm area in Sapphire.

Keywords: Sapphire etching; Femtosecond pulse laser ablation

Hydrous ferric oxide doped alginate beads for fluoride removal: Adsorption kinetics and equilibrium studies by M.G. Sujana; A. Mishra; B.C. Acharya (pp. 767-776).

► Hydrous ferric oxide and alginate composite beads were synthesised, characterised, and studied for fluoride removal efficiency. ► Showed fast kinetics, data fitted well by a pseudo-second order model. ► Demonstrated Langmuir F⁻ adsorption capacity of 8.90mgg⁻¹ at pH 7.0. ► Both specific and non-specific sorption mechanisms were identified on bead surface. ► HCl is quite effective and showed 75–80% desorption indicating the reusability.A new biopolymer beads, composite of hydrous ferric oxide (HFO) and alginate were synthesised, characterised and studied for its fluoride efficiency from water. The beads were characterised by chemical analysis, BET surface area, pH_PZC and X-ray diffraction (XRD) analysis. The optimum conditions for fluoride removal were determined by studying operational variables viz. pH, contact time, initial F⁻ concentration, bead dose and temperature. Presence of other anions like SO₄²⁻, PO₄³⁻, NO₃⁻, Cl⁻ and HCO₃⁻ effect on fluoride removal efficiency of prepared beads was also tested. The beads were 0.8–0.9mm in size and contain 32–33% Fe (III) and showed specific surface area of 25.80m²g⁻¹ and pH_PZC of 5.15. Modified beads demonstrated Langmuir F⁻ adsorption capacity of 8.90mgg⁻¹ at pH 7.0. The adsorption kinetics were best described by the pseudo-second order kinetic model followed by intra-particle diffusion as the rate determining step. It was found that about 80% of the adsorbed fluoride could be desorbed by using 0.05M HCl. The FTIR, Raman and SEM-EDAX analysis were used to study the fluoride adsorption mechanisms on beads. Studies were also conducted to test the potential application of beads for F⁻ removal from drinking water and the treated water quality.

Keywords: Adsorption; Alginate beads; Fluoride; Ferric oxide; Isotherm study

XPS analysis of aluminosilicate microspheres bioactivity tested in vitro by M. Todea; E. Vanea; S. Bran; P. Berce; S. Simon (pp. 777-783).

► Surface structure effect of Y₂O₃ addition to SiO₂–Al₂O₃ spray dried microspheres. ► Surface changes induced by 7 days incubation in simulated body fluid (SBF). ► XPS results point out both yttrium and SBF induced changes. ► Yttrium incorporation promotes the self assembly in SBF of an apatite type layer.The study aims to characterize surface properties of aluminosilicate microspheres incorporating yttrium, with potential biomedical applications. Micrometric particles of spherical shape were obtained by spray drying method. The behavior of aluminosilicate microspheres without yttrium and with yttrium was investigated under in vitro conditions, by seven days incubation in simulated body fluid (SBF). The surface elemental composition and the atomic environments on outermost layer of the microspheres, prior to and after incubation in SBF were evaluated by X-ray photoelectron spectroscopy (XPS) in order to investigate their bioactivity. The results were analyzed to underline the effect of yttrium addition on surface properties of the aluminosilicate microspheres and implicitly on the behavior of the samples in simulated body environments.

Keywords: Microspheres; Spray drying; Aluminosilicates; Yttrium; XPS

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Applied Surface Science (v.270, #)