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Applied Surface Science (v.257, #9)

Editorial Board (pp. ii).

The fabrication of 3-D nanostructures by a low- voltage EBL by Seung Hun Oh; Jae Gu Kim; Chang Seok Kim; Doo Sun Choi; Sunghwan Chang; Myung Yung Jeong (pp. 3817-3823).

▶ In the low-voltage EBL, the exposure depth and width approach a saturation value. ▶ The exposed patterns are strongly affected by the aperture size and baking temperature in the low voltage EBL. ▶ The depth in the superposed-dose area is 10–20% greater than that in the single-dosed area at 1kV. ▶ Using these characteristics of low-voltage EBL, we fabricated stepped 3-D nanostructures, V-groove patterns, and 3-D structures with depth variations of only a few nanometers.Three-dimensional (3-D) structures are used in many applications, including the fabrication of opto-electronic and bio-MEMS devices. Among the various fabrication techniques available for 3-D structures, nano imprint lithography (NIL) is preferred for producing nanoscale 3-D patterns because of its simplicity, relatively short processing time, and high manufacturing precision. For efficient replication in NIL, a precise 3-D stamp must be used as an imprinting tool. Hence, we attempted the fabrication of original 3-D master molds by low-voltage electron beam lithography (EBL). We then fabricated polydimethylsiloxane (PDMS) stamps from the original 3-D mold via replica molding with ultrasonic vibration.First, we experimentally analyzed the characteristics of low-voltage EBL in terms of various parameters such as resist thickness, acceleration voltage, aperture size, and baking temperature. From these e-beam exposure experiments, we found that the exposure depth and width were almost saturated at 3kV or lesser, even when the electron dosage was increased. This allowed for the fabrication of various stepped 3-D nanostructures at a low voltage. In addition, by using line-dose EBL, V-groove patterns could be fabricated on a cured electron resist (ER) at a low voltage and low baking temperature. Finally, the depth variation could be controlled to within 10nm through superposition exposure at 1kV. From these results, we determined the optimum electron beam exposure conditions for the fabrication of various 3-D structures on ERs by low-voltage EBL. We then fabricated PDMS stamps via the replica molding process.

Keywords: Three-dimensional (3-D) nano structure; Electron beam lithography; Low voltage; Nano imprint lithography (NIL); PDMS

Plasma treatment of carbon fibers: Non-equilibrium dynamic adsorption and its effect on the mechanical properties of RTM fabricated composites by Keming Ma; Baichen Wang; Ping Chen; Xia Zhou (pp. 3824-3830).

▶ Fluorescent label was used to study the change of curing agent content in the epoxy resin at the inlet and outlet of the RTM mould, which have been scarcely reported before. ▶ The effect of oxygen plasma treatment on the non-equilibrium dynamic adsorption of the carbon fabric reinforcements in RTM process was studied. ▶ Concentration changes of some oxygen containing polar groups and no oxygen containing groups on the carbon fiber surface induced by the oxygen plasma treatment may affect its adsorption ability to the resin and curing agent. ▶ An optimum plasma treatment condition existed for the mechanical properties of RTM fabricated composites.The effect of oxygen plasma treatment on the non-equilibrium dynamic adsorption of the carbon fabric reinforcements in RTM process was studied. 5-Dimethylamino-1-naphthalene-sulfonylchloride (DNS-Cl) was attached to the curing agent to study the change of curing agent content in the epoxy resin matrix. Steady state fluorescence spectroscopy (FS) analysis was used to study this changes in the epoxy resin at the inlet and outlet of the RTM mould, and XPS was used to study the chemical changes on the carbon fiber surfaces introduced by plasma treatment. The interlaminar shear strength (ILSS) and flexural strength were also measured to study the effects of this non-equilibrium dynamic adsorption progress on the mechanical properties of the end products. FS analysis shows that the curing agent adsorbed onto the fiber surface preferentially for untreated carbon fiber, the curing agent content in the resin matrix maintain unchanged after plasma treatment for 3min and 5min, but after oxygen plasma treatment for 7min, the epoxy resin adsorbed onto the fiber surface preferentially. XPS analysis indicated that the oxygen plasma treatment successfully increased some polar functional groups concentration on the carbon fiber surfaces, this changes on the carbon fiber surfaces can change the adsorption ability of carbon fiber to the resin and curing agent. The mechanical properties of the composites were correlated to this results.

Keywords: RTM; Fluorescence; Oxygen plasma treatment; Non-equilibrium dynamic adsorption

Preparation and electroactive properties of a PVDF/nano-TiO₂ composite film by Ningli An; Hongzhong Liu; Yucheng Ding; Min Zhang; Yiping Tang (pp. 3831-3835).

▶ A PVDF/nano-TiO₂ electroactive film was prepared with solution coating method. ▶ The composite film evaporating at 110°C contained PVDF β phase. ▶ TiO₂ improved the electroactive properties of the composite film.In the present study, poly(vinylidene fluoride) (PVDF)/nano-TiO₂ electroactive film was prepared by coating a substrate with an acetone/DMF solution, which was evaporated at a high temperature (110°C). The crystallisation behaviour, dynamic mechanical properties and electroactive properties of this PVDF/nano-TiO₂ electroactive film were investigated. The cross-section and surface of the film were observed with a scanning electron microscope (SEM). X-ray diffraction (XRD) results showed that the film containing the PVDF β phase, the desired ferroelectric phase, was obtained by crystallising the mixed solution of nano-TiO₂ and PVDF at 110°C, while the film containing the α phase was obtained from the crystallisation of the pure PVDF solution at the same temperature. It was found that the storage modulus, the room-temperature dielectric constant and the electric breakdown strength of the composite films were much higher than those of a pure PVDF film. TiO₂ improved the mechanical properties and electroactive properties of the film. The results indicate that PVDF/nano-TiO₂ composite films can be applied to the fabrication of self-sensing actuator devices.

Keywords: PACS; 77.55.+f; 82.35.NpPVDF; TiO; ₂; Composite materials; Solution; Thin films; Electroactive

Influence of MgO and ZrO₂ buffer layers on dielectric properties of Ba(Zr_0.20Ti_0.80)O₃ thin films prepared by sol–gel processing by L.N. Gao; J.W. Zhai; X. Yao (pp. 3836-3839).

▶ A modified sol–gel process was used to prepare BZT thin films. ▶ Orientation of BZT films can be tailored by using MgO and ZrO₂ buffer layers. ▶ High FOM and low leakage current density were achieved in BZT films with buffer layers.Ba(Zr_0.20Ti_0.80)O₃ (BZT) thin films are deposited on Pt(111)/Ti/SiO₂/Si, MgO and ZrO₂ buffered Pt(111)/Ti/SiO₂/Si substrates by a sol–gel process. The BZT thin films directly grown on Pt(111)/Ti/SiO₂/Si substrates exhibit highly (111) preferred orientation, while the films deposited on Pt(111)/Ti/SiO₂/Si substrates with MgO and ZrO₂ buffer layers show highly (110) preferred orientation. At 100kHz, dielectric constants are 417, 311 and 321 for the BZT thin films grown on Pt(111)/Ti/SiO₂/Si, MgO and ZrO₂ buffered Pt(111)/Ti/SiO₂/Si substrates, respectively. The difference in dielectric properties of three BZT films can be attributed to the series capacitance effect, interface conditions and their orientations.

Keywords: Thin film; Sol–gel; Dielectric properties; Orientation; Tunability

Controllable microstructures and multiferroic properties of Pb(Zr_0.53Ti_0.47)O₃–CoFe₂O₄ composite films by Lu-Yi Ding; Fei-Xiang Wu; Yan-Bin Chen; Zheng-Bin Gu; Shan-Tao Zhang (pp. 3840-3842).

▶ By combining lithography technology and pulsed laser deposition techniques, 1–3 and 2–2 types Pb(Zr_0.53Ti_0.47)O₃–CoFe₂O₄ (PZT–CFO) composite films with well controlled microstructures were prepared and the structures and properties were investigated. ▶ Intrinsic room temperature ferroelectric and magnetic behaviors are observed simultaneously, confirmed by saturated polarization-electric and magnetic-magnetic field loops. ▶ Our results may provide an alternative method to design and prepare multiferroic composite films with controllable microstructures.1–3 and 2–2 types Pb(Zr_0.53Ti_0.47)O₃–CoFe₂O₄ (PZT–CFO) composite films with controllable microstructures, consisted by CFO nanopillar embedded in PZT matrix and PZT–CFO gratings respectively, have been fabricated on Pt/Ti/SiO₂/Si substrates by combining lithography technology and pulsed laser deposition. X-ray diffraction confirms that the films are well crystallized under optimized postannealing conditions. Scanning electron microscope reveals that the periodic microstructures can be well controlled. Especially, intrinsic room temperature ferroelectric and ferrimagnetic behaviors are observed simultaneously. The structure–properties relationship is discussed. Our results may provide an alternative method to design and prepare multiferroic composite films with controllable microstructures.

Keywords: PACS; 77.84.−s; 77.80.−e; 75.80.+qMultiferroic; Composite films; PZT–CFO

The tribological chemistry of the triazine derivative additives in rape seed oil and synthetic diester by Rui Qiao; Jing Li; Hua Wu; Tianhui Ren; Yidong Zhao; Chenyan Ma (pp. 3843-3849).

▶ In this study, two new compounds are synthesized and their tribological properties have been discussed. ▶ We study the same and different properties of the TRLA in different base stocks have also been discussed in this paper. ▶ We find the new synthesized additives have better properties than those of the commercial additives. ▶ In this study, we discuss the mechanism of the two different additives by XANES.The additives, laurylamino-methylthio-1,3,5-triazine-2,4-dithiol (referred to as TRLA) and diisooctylamino-methylthio-1,3,5-triazine-2,4-dithiol (referred to as TREA), were prepared in our laboratory. The products were characterized by means of infrared spectroscopy (IR) and elemental analysis. Their tribological behaviors as additives in raped seed oil and diester were evaluated using four-ball friction and wear testers as well. The results suggest that all the synthesized compounds have excellent tribological behaviors and they were compared with sulfurized isobutene (referred to as SIB) which is a commercial additive. The results show that they have good tribological properties. The two additives were investigated on thermal films and tribofilms by using X-ray absorption near edge structure (XANES) spectroscopy. The results of surface analysis reveal that the thermal films formed from TREA and TRLA in rape seed oil (referred to as RSO) and diester (referred to as DE), all are consist of iron sulfate; under mild AW conditions, the tribofilms from TRLA and TREA in DE is mainly composed of FeS, while the tribochemcal film from TRLA in RSO is mainly composed of iron sulfite; under EP-1 (the maximum non-seizure load) conditions, the tribochemical films from TRLA and TREA in RSO and DE mainly consist of FeS and FeSO₄; under EP-2 (nearly weld load) conditions, the tribochemical films from TRLA and TREA in RSO and DE mainly consist of FeS.

Keywords: Triazine derivative additives; Tribological chemistry; XANES

Self assembled micro masking effect in the fabrication of SiC nanopillars by ICP-RIE dry etching by A. Kathalingam; Mi-Ra Kim; Yeon-Sik Chae; S. Sudhakar; T. Mahalingam; Jin-Koo Rhee (pp. 3850-3855).

▶ This paper deals the fabrication of 4H–SiC nanopillars using ICP-RIE dry etching in Cl₂/Ar gas plasma. ▶ Cylindrical nanopillars of 300nm diameter and 500nm height with smooth side walls were etched on SiC wafer. ▶ The novelty is the fabrication of nano pillars without patterned etch mask. ▶ The most interesting feature of this mask-less etching is the pore structure of the pillars that is each pillar has been produced as a hollow structure having a pore centrally along its length. ▶ The self assembled micro masking effect for the fabrication of this unique nanostructure has been investigated in this paper. ▶ To our knowledge, no report is available on the fabrication of SiC nanopillars without using patterned nano mask. ▶ In this report we present the experimental results on the novel fabrication of SiC nanopillars using mask-free Cl₂ based ICP-RIE etching technique.This report presents the results of the novel fabrication of 4H-SiC pillars with nanopores using ICP-RIE dry etching. Cl₂/Ar gas plasma with various mass flow rates was used in this etching process to produce SiC nanopillars without using patterned etch mask. Cylindrical pillars of 300nm diameter and 500nm height with smooth side walls were etched on SiC wafer. The etching condition for the optimized fabrication of SiC nanopillars is presented in this report. Each nanopillar has been produced with a nanosize pore at the center along its length and up to the middle of the cylindrical nanopillar; it is a unique feature has not ever been reported in case of SiC. Inclusion of oxygen was found influence the formation of nanopillars by the effect of SiO₂ micro masking. The formation of self assembled SiO₂ layer and its micro masking effect in the fabrication of this unique nanostructure has been investigated using TEM, STEM and EDAX measurements.

Keywords: Dry etching; Silicon carbide; ICP-RIE etching; Cl; ₂; /Ar gas plasma; Self assembled micro mask; Nanopillar

Effect of substrate temperature on the morphology, structural and optical properties of Zn1−_xCo_xO thin films by S.Y. Yang; B.Y. Man; M. Liu; C.S. Chen; X.G. Gao; C.C. Wang; B. Hu (pp. 3856-3860).

▶ Zn1−_xCo_xO thin films on sapphire (0001) substrates were prepared by PLD. ▶ Ts affected the microstructure, morphology and optical properties of all samples. ▶ The emission peak at 418 and 490nm was in relation to Zn_i and V_OZn_i, respectively. ▶ The quantity of Zn_i remained mostly invariable under a fixed work ambient pressure.Zn1−_xCo_xO thin films with c-axis preferred orientation were deposited on sapphire (0001) by pulsed laser deposition (PLD) technique at different substrate temperatures in an oxygen-deficient ambient. The effect of substrate temperature on the microstructure, morphology and the optical properties of the Zn1−_xCo_xO thin films was studied by means of X-ray diffraction (XRD), atomic force microscopy (AFM), UV–visible–NIR spectrophotometer, fluorescence spectrophotometer. The results showed that the crystallization of the films was promoted as substrate temperature rose. The structure of the samples was not distorted by the Co incorporating into ZnO lattice. The surface roughness of all samples decreased as substrate temperature increased. The Co concentration in the film was higher than in the target. Emission peak near band edge emission of ZnO from the PL spectra of the all samples was quenched because the dopant complexes acted as non-radiative centers. While three emission bands located at 409nm (3.03eV), 496nm (2.5eV) and 513nm (2.4eV) were, respectively, observed from the PL spectra of the four samples. The three emission bands were in relation to Zn interstitials, Zn vacancies and the complex of V_O and Zn_i (V_OZn_i). The quantity of the Zn interstitials maintained invariable basically, while the quantity of the V_OZn_i slightly decreased as substrate temperature increased.

Keywords: Zn; 1−; _x; Co; _x; O thin films; PLD; Substrate temperature; Morphology; Structural and optical properties

Fabrication and characterization of polycrystalline silicon nanowires with silver-assistance by electroless deposition by Xianzhong Sun; Ran Tao; Linhan Lin; Zhengcao Li; Zhengjun Zhang; Jiayou Feng (pp. 3861-3866).

▶ In the present work, we presented a facile fabrication process of polycrystalline silicon nanowires, and studied their surface chemical composition and bonding. The surface dangling bonds of as-etched silicon nanowire arrays are saturated by silver and hydrogen. ▶ After immersion in concentrated HNO₃ aqueous solution, silicon nanowires can be passivated by oxygen. The photoluminescence spectra of silicon nanowires show red light emissions centered around 700nm. The oxygen-passivated porous silicon nanowires show much higher photoluminescence intensities than the silver/hydrogen-passivated ones. ▶ The influences of surface chemical states on the wettability of silicon nanowire arrays were also studied. ▶ We obtained a superhydrophobic surface on the as-etched silicon nanowire arrays without surface modification with any organic low-surface-energy materials, and realized the evolution from superhydrophobicity to superhydrophilicity via surface modifications with HNO₃ solutions.Single crystal silicon wafers are widely used as the precursors to prepare silicon nanowires by employing a silver-assisted chemical etching process. In this work, we prepared polycrystalline silicon nanowire arrays by using solar-grade multicrystalline silicon wafers. The chemical composition and bonding on the surface of silicon nanowire arrays were characterized by Fourier Transform Infrared spectroscope, and X-ray photoelectron spectroscope. The photoluminescence spectra of silicon nanowires show red light emissions centered around 700nm. Due to the passivation effect of Si dangling bonds by concentrated HNO₃ aqueous solution, the photoluminescence intensities are improved by 2 times. The influences of surface chemical states on the wettability of silicon nanowire arrays were also studied. We obtained a superhydrophobic surface on the as-etched silicon nanowire arrays without surface modification with any organic low-surface-energy materials, and realized the evolution from superhydrophobicity to superhydrophilicity via surface modifications with HNO₃ solutions.

Keywords: Silicon nanowire arrays; Silver-assisted chemical etching; Photoluminescence; Superhydrophobicity; Superhydrophilicity

Surface properties of liquid In–Zn alloys by J. Pstruś; Z. Moser; W. Gąsior (pp. 3867-3871).

▶ Surface tension of In–Zn was determined with MBP method and density with dilatometric method ▶ For pure components surface tension was verified with SD method ▶ With increasing content of Zn the surface tension increases but density decreases ▶ Indium is adsorbed in the surface layer of the solution for the whole range of concentrations ▶ Alloys of low Zn content show good agreement between experiment and Butler model calculations.The measurements of surface tension and density of zinc, indium and liquid In–Zn alloys containing 0.9, 0.85, 0.75, 0.70, 0.60, 0.40, 0.25 and 0.10mole fraction of In were carried out using the method of maximum pressure in gaseous bubbles (MBP) as well as dilatometric technique. The technique of sessile drop was additionally applied in the measurements of surface tension for pure indium and zinc. The measurements were performed at temperature range 474–1151K. The isotherms of surface tension calculated based on Butler's equation at 700 and 1100K corresponded well with the experimental values for zinc content lower than 0.6mole fraction. The surface tension calculated for alloys of higher zinc concentrations (0.6< X_Zn<0.95) had a positive value of the surface tension temperature coefficient (d σ/d T), which did not coincide with the experimental results. The density as well as molar volume of liquid In–Zn alloys showed almost identical behaviour like the ideal solutions. The observed little deviations were contained within assessed experimental errors.

Keywords: In–Zn alloys; Surface tension; Pb-free solders; Surface concentration; Butler model; Density

Temperature controlled synthesis of SrCO₃ nanorods via a facile solid-state decomposition rout starting from a novel inorganic precursor by Fatemeh Davar; Masoud Salavati-Niasari; Sotirios Baskoutas (pp. 3872-3877).

Strontium carbonate nanorods have been successfully synthesized via solid-state decomposition of a new precursor, [Sr(Pht)(H₂O)₂] at 500°C. The obtained nanorods were found to be orthorhombic with the length of 70–100nm and the diameter of about 10–15nm. Effect of calcinations temperature on morphology and purity of the products has been investigated.Display Omitted▶ Strontium phthalate as new precursor. ▶ Solid-state decomposition as good method for synthesis of nano-sized SrCO₃. ▶ Various temperatures has different effects on the morphology.Strontium carbonate nanorods have been successfully synthesized via solid-state decomposition of a new precursor, [Sr(Pht)(H₂O)₂]. The obtained nanorods were found to be orthorhombic with the length of 70–100nm and the diameter of about 10–15nm. The Effect of calcinations temperature on morphology and purity of the products has been investigated. Strontium carbonate nanorods were formed at 500°C. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectroscopy. In addition, further evidence for the purity and stoichiometry of the product was obtained by XPS (X-ray photoelectron spectroscopy) spectrum.

Keywords: Inorganic precursor; SrCO; ₃; Phthalate; Solid-state decomposition

Modification of Pd–CeO₂ catalyst by different treatments: Effect on the structure and CO oxidation activity by Bin Wang; Duan Weng; Xiaodong Wu; Rui Ran (pp. 3878-3883).

▶ Redox treatment decreases the Pd–CeO₂ interface and so decreases the CO oxidation activity. ▶ Pd is encapsulated by the CeO₂ support during redox treatment and it is the SMSI mechanism in PM doped catalyst. ▶ CO oxidation over Pd–CeO₂ catalyst mainly via ceria mediated mechanism.To investigate the interaction between noble metal and CeO₂, a Pd-doped CeO₂ catalyst was prepared by sol–gel method, and the catalyst was then treated in static air and a H₂/O₂ alternating flow at 800°C, respectively. It is found by step-scanning XRD that Pd ions migrate out of the ceria lattice during the redox treatment, while the exudation of Pd is not so obvious after the oxidative treatment. For the CO oxidation activity, the redox treated catalyst is seriously weakened compared with the oxidative-treated one. This difference is ascribed to the encapsulation of Pd crystallites by the CeO₂ support during the redox treatment, which is confirmed by XPS and CO-TPR. Based on the activity and FTIR results, it is proposed that, CO oxidation at low temperatures proceeds mainly via the reaction between the adsorbed CO on Pd sites and the lattice oxygen of surface CeO₂ at the Pd–Ce interface.

Keywords: Palladium; Ceria; Oxidative/redox treatment; Encapsulation; Metal–support interaction

Dependence of aluminum-doped zinc oxide work function on surface cleaning method as studied by ultraviolet and X-ray photoelectron spectroscopies by Weiyan Wang; Quanyu Feng; Kemin Jiang; Jinhua Huang; Xianpeng Zhang; Weijie Song; Ruiqin Tan (pp. 3884-3887).

▶ Both acetone solvent and UV-ozone cleaning enhance AZO work function. ▶ UV-ozone treated AZO achieves relative higher work function of 4.26eV. ▶ Stoichiometry ratio and carbon contamination affect AZO work function, and the stoichiometry ratio is the controlling factor. ▶ AZO with high stoichiometry ratio and reduced carbon concentration possesses high work function.The dependence of aluminum-doped zinc oxide (AZO) work function on surface treatment, i.e. acetone solvent cleaning and ultraviolet (UV)-ozone cleaning, was studied by ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy. Comparing different cleaning methods, UV-ozone treated AZO achieved relative higher work function of 4.26eV; whereas acetone solvent treated AZO had relative lower work function of 3.94eV. Two factors, stoichiometry ratio of [O_ZnAl]/[Zn]+1.5[Al] and carbon contamination on AZO surface, affected the work function and, moreover, the stoichiometry ratio was supposed to be the controlling factor. It was concluded that AZO with high stoichiometry ratio and reduced carbon concentration possessed high work function.

Keywords: Al-doped zinc oxide; Work function; UV-ozone treatment; Ultraviolet photoelectron spectroscopy

Synthesis of chitosan/hydroxyapatite membranes coated with hydroxycarbonate apatite for guided tissue regeneration purposes by Alexandre Félix Fraga; Edson de Almeida Filho; Eliana Cristina da Silva Rigo; Anselmo Ortega Boschi (pp. 3888-3892).

Chitosan, which is a non-toxic, biodegradable and biocompatible biopolymer, has been widely researched for several applications in the field of biomaterials. Calcium phosphate ceramics stand out among the so-called bioceramics for their absence of local or systemic toxicity, their non-response to foreign bodies or inflammations, and their apparent ability to bond to the host tissue. Hydroxyapatite (HA) is one of the most important bioceramics because it is the main component of the mineral phase of bone. The aim of this work was to produce chitosan membranes coated with hydroxyapatite using the modified biomimetic method. Membranes were synthesized from a solution containing 2% of chitosan in acetic acid (weight/volume) via the solvent evaporation method. Specimens were immersed in a sodium silicate solution and then in a 1.5 SBF (simulated body fluid) solution. The crystallinity of the HA formed over the membranes was correlated to the use of the nucleation agent (the sodium silicate solution itself). Coated membranes were characterized by means of scanning electron microscopy – SEM, X-ray diffraction – XRD, and Fourier transform infrared spectroscopy – FTIR. The results indicate a homogeneous coating covering the entire surface of the membrane and the production of a semi-crystalline hydroxyapatite layer similar to the mineral phase of human bone.

Keywords: Biomimetic method; Chitosan; Membranes and hydroxyapatite

Compositional and structural characterization of nanoporous films produced by iron anodizing in ethylene glycol solution by Arūnas Jagminas; Kęstutis Mažeika; Nerijus Bernotas; Vaclovas Klimas; Algirdas Selskis; Dalis Baltrūnas (pp. 3893-3897).

Display Omitted▶ The anodizing of iron in ethylene glycol containing NH₄F and H₂O has been optimized. ▶ In this electrolyte, nanoporous films up to 10μm thick can be formed. ▶ Mössbauer spectra evidenced these films consisting of lepidocrocite (γ-FeOOH) and some Fe(II) compounds.We report on the composition and morphology of as-grown anodic oxide films onto the iron surface in an ethylene glycol solution containing some NH₄F and H₂O by anodizing under direct current bias. Decrease in the content of NH₄F and the temperature of electrolyte allow us to form either nanochannel or nanotubular films over a larger potential window, ca. from 30 to 100V. By this way, the films in thickness of up to10μm have been formed. Mössbauer spectra recorded at room to cryogenic temperatures under conversion electron and transmission modes revealed the formation of lepidocrocite (γ-FeOOH) film containing some Fe(OH)₂ and/or FeF₂·4H₂O. An increase in anodizing voltage results in fabrication of more porous and less Fe(II) compounds containing films.

Keywords: Nanostructures; Anodizing; Iron oxides; Mössbauer spectroscopy

Properties of a-Si:H films deposited by RF magnetron sputtering at 95°C by D. Girginoudi; C. Tsiarapas; N. Georgoulas (pp. 3898-3903).

▶ Study of optoelectronical properties of RF sputtered (at 95°C) a-Si:H films. ▶ Strong correlation between H content, dangling bonds and optoelectronic properties. ▶ Enhanced disorder of the films introduced by large number of inactive impurities. ▶ Existence of SiH and SiH₂ bonds – high values of [SiH_x] – low doping efficiency. ▶ n–i–p solar cells fabricated on polyimide substrates with an efficiency of 1.54%.In this work we have investigated the dependence of optical and electrical properties of RF sputtered undoped a-Si:H films and B or P doped a-Si:H films on hydrogen flow rate ( F_H). Low deposition temperature of 95°C was used, a process compatible with low-cost plastic substrates. FTIR spectroscopy and ESR measurements were used for the investigation of Si–H_x bonding configurations, and concentrations of hydrogen and dangling bonds. We found that there is a strong correlation between the total hydrogen concentration, the dangling bonds density and the optoelectronic properties of the films. The best photosensitivity value was found to be 1.4×10⁴ for the undoped films. The dark conductivity ( σ_D) of the doped layers varied from 5.9×10⁻⁸ to 6.5×10⁻⁶ (Ωcm)⁻¹ for different ratios F_Ar/ F_H. These variations are attributed to both the different B and P concentrations in the films (according to SIMS measurements) and the enhanced disorder of the films introduced by the large number of inactive impurities. The B doping efficiency is lower compared to the P one. A small photovoltaic effect is also observed in n–i–p solar cells fabricated on polyimide (PI) substrates having ITO as antireflective coating, with an efficiency of 1.54%.

Keywords: PACS; 71.23.Cq; 73.50.Pz; 73.61.JcAmorphous silicon; Low temperature sputtering; Doping; Structural-optoelectronic properties; Solar cells

Poly-dimethylsiloxane derivates side chains effect on syntan functionalized Polyamide fabric by V. Migani; H. Weiss; M.R. Massafra; A. Merlo; C. Colleoni; G. Rosace (pp. 3904-3912).

▶ Syntan crosslinks silicone polymers onto Polyamide-6,6 textile fabric. ▶ Polyether and Amino-Polyether silicone improve hydrophilicity of syntanned PA. ▶ Silicone ether side chains support the formation of a porous structure. ▶ Silicone amino side chains improve interactions onto syntanned substrate.Poly-dimethylsiloxane (PDMS) polymers finishing of Polyamide-6,6 (PA66) fabrics involves ionic interactions between reactive groups on the PDMS polymers and the ones of the textile fabric. Such interactions could be strengthened by a pretreatment with a fixing agent to promote either ion–ion and H-bonding and ion-dipole forces. These forces could contribute towards the building of substantial PDMS-PA66 systems and the achieving of better adhesion properties to fabrics. Four different silicone polymers based on PDMS were applied on a synthetic tanning agent (syntan) finished Polyamide-6,6 fabric under acid conditions. Soxhlet extraction method and ATR FT-IR technique were used to investigate the application conditions. The finishing parameters such as pH and temperature together with fastness, mechanical and performance properties of the treated samples were studied and related to PDMS side chains effect on syntan functionalized Polyamide fabric.

Keywords: Textile finishing; Poly-dimethylsiloxane; Crosslinking; Syntan; Polyamide; ATR FT-IR

Surface modification of Al–20Si alloy by high current pulsed electron beam by Y. Hao; B. Gao; G.F. Tu; S.W. Li; S.Z. Hao; C. Dong (pp. 3913-3919).

▶ Firstly, special “halo” microstructure caused by interdiffusion of Al and Si atoms appears on the treated surface. ▶ Secondly, the metastable structures, such as supersaturated solid solution of Al, nano-silicon and subgrain, are formed on the modified surface. ▶ Thirdly, the microhardness of “halo” presents a gradient change after 15 pulses, and the hardness of remelted layer of 25-pulsed sample is higher than of the matrix.Hypereutectic Al–20Si (Si 20wt.%, Al balance)alloy surface was treated with high current pulsed electron beam (HCPEB) under different pulse numbers. The results indicate that HCPEB irradiation induces the formation of metastable structures on the treated surface. The coarse primary Si particle melts, producing a “halo” microstructure with primary Si as the center on the melted surface. A supersaturated solid solution of Al is formed in the melted layer caused by Si atoms dissolving into the Al matrix. Cross-section structure analysis shows that a 4μm remelted layer is formed underneath the top surface of the HCEPB-treated sample. Compared with the matrix, the Al and Si elements in the remelted layer are distributed uniformly. In addition, the grains of the Al–20Si alloy surface are refined after HCPEB treatment, as shown by TEM observation. Nano-silicon particles are dispersed on the surface of remelted layer. Polygonal subgrains, approximately 50–100nm in size, are formed in the Al matrix. The hardness test results show that the microhardness of the α(Al) and eutectic structure is increased with increasing pulse number. The hardness of the “halo” microstructure presents a gradient change after 15 pulse treatment due to the diffusion of Si atoms. Furthermore, hardness tests of the cross-section at different depths show that the microhardness of the remelted layer is higher than that of the matrix. Therefore, HCPEB technology is a good surface modification method for enhancing the surface hardness of hypereutectic Al–20Si alloy.

Keywords: High current pulsed electron beam; Al–20Si alloy; Surface modification; Metastable structures; Microhardness

Hydrothermal synthesis of C-doped Zn₃(OH)₂V₂O₇ nanorods and their photocatalytic properties under visible light illumination by Hongxu Guo; Jianhua Chen; Wen Weng; Shunxing Li (pp. 3920-3923).

A visible-light-driven photocatalyst, C-doped Zn₃(OH)₂V₂O₇, prepared by a hydrothermal method was studied. The as-prepared catalyst was characterized by the methods of SEM, XRD, DRS and XPS, and exhibited efficient photocatalytic activity in the degradation of methylene blue (MB) under visible-light irradiation.Display Omitted▶ A visible-light-driven photocatalyst, C-doped Zn₃(OH)₂V₂O₇, prepared by a hydrothermal method was firstly studied. ▶ The catalyst exhibited efficient photocatalytic activity in the degradation of methylene blue under visible-light irradiation. ▶ The carbon existing on the surface of Zn₃(OH)₂V₂O₇ nanorodes is free and carbide formation.A visible light-driven photocatalyst, C-doped Zn₃(OH)₂V₂O₇, prepared by a hydrothermal method was studied. The as-prepared catalyst was characterized by SEM, XRD, DRS, and XPS, and exhibited efficient photocatalytic activity in the degradation of methylene blue (MB) under visible-light irradiation. Besides decoloring, the decomposition of MB was also observed, further demonstrating the performance of the photocatalyst. The carbon existing on the surface of Zn₃(OH)₂V₂O₇ nanorods was free and in carbide form. Dye degradation followed first-order kinetics, and was explained on the basis of the Langmuir–Hinshelwood mechanism.

Keywords: Visible-light-driven photocatalyst; C-doped Zn; ₃; (OH); ₂; V; ₂; O; ₇; Methylene blue; Langmuir–Hinshelwood mode

Scattering effects of primary electrons in Co/Cu(111) measured by Auger; elastic and loss electrons by D. Turko; I. Morawski; J. Siwiak; M. Nowicki (pp. 3924-3928).

▶ The novelity of this work is the measurement of electron losses as a function of the primary electron beam, which give structural as well as chemical information. ▶ We duscussed different mechanisms of electron emission in DEELS, DAES, and DEPES.Electron energy losses were measured as a function of the incidence angle of the primary electron beam for the Co/Cu(111) adsorption system. The measurements performed for the clean and covered substrate reveal characteristic intensity maxima associated with the close packed rows of atoms, as it was observed in the so called directional Auger and directional elastic peak electron spectroscopy profiles. The incidence angle dependent signal of electron energy losses measured for the clean (Cu 3p_3/2) and covered (Co 3p_3/2) substrate gives the so called directional electron energy loss spectroscopy (DEELS) profiles which contain structural as well as chemical information. The scattering of primaries and different emission processes associated with electron energy losses, Auger, and elastically backscattered electrons are discussed. A change in the h_Cu (Cu M_2,3VV transition) Auger signal recorded during the continuous cobalt deposition shows that the growth mode is not a pure layer by layer type. The complete covering of the substrate by Co at higher coverages is confirmed by the comparison between experimental and theoretical ratios of the Auger peak heights.

Keywords: PACS; 91.60Ed; 91.55.Nc; 61.05.jdPrimary electron scattering; Electron energy losses; Directional elastic peak electron spectroscopy (DEPES); Directional Auger electron spectroscopy (DAES); Cobalt; Copper; Crystalline structure

Sol–gel titania films on YHfAl foils and their influence on inhibition of transition aluminas during oxidation at high temperatures by R. Chegroune; M. Keddam; Y. Wouters; A. Galerie; E. Salhi (pp. 3929-3935).

▶ Sol–gel technique was used as surface coating of YHfAl alloys to avoid the formation of transition aluminas. ▶ A sol–gel TiO₂ film of nearly 60nm thick has proven its efficiency and has allowed to reduce the presence of transition aluminas.In this experimental work, sol–gel technique was used as surface coating of YHfAl alloys to avoid the formation of transition aluminas ( δ and θ). This technique has an advantage of low cost and rapidity. The preparation conditions of TiO₂ sol–gel coatings were presented with a description of their evolution with temperature during the first stages of YHfAl oxidation. It is noted that the rutile is the only detected phase at 800°C. The sol–gel thin films were prepared in order to inhibit the formation of transition aluminas. An important gain mass was recorded at a temperature of 875°C and the first grains of aluminas were appeared after 0.5h of oxidation. A sol–gel TiO₂ film of nearly 60nm thick has proven its efficiency and has allowed to reduce the presence of transition aluminas.

Keywords: Sol–gel; Kinetics; Titanium oxide; Transition aluminas; Alumina α; High temperature oxidation

Ammonia modification of activated carbon to enhance carbon dioxide adsorption: Effect of pre-oxidation by Mohammad Saleh Shafeeyan; Wan Mohd Ashri Wan Daud; Amirhossein Houshmand; Arash Arami-Niya (pp. 3936-3942).

Display Omitted▶ Decomposition of oxygen functionalities was an intermediate stage to development of active sites before amination for the formation of nitrogen surface groups. ▶ Oxidation followed by high temperature amination considerably enhanced the CO₂ uptake at higher temperatures. ▶ Compared to the textural characteristics, formation of basic nitrogen functionalities plays a more active role on CO₂ adsorption at higher temperatures. ▶ CO₂ capture capacity depends on both the type and amount of the nitrogen surface groups introduced onto the carbon surface.A commercial granular activated carbon (GAC) was subjected to thermal treatment with ammonia for obtaining an efficient carbon dioxide (CO₂) adsorbent. In general, CO₂ adsorption capacity of activated carbon can be increased by introduction of basic nitrogen functionalities onto the carbon surface. In this work, the effect of oxygen surface groups before introduction of basic nitrogen functionalities to the carbon surface on CO₂ adsorption capacity was investigated. For this purpose two different approaches of ammonia treatment without preliminary oxidation and amination of oxidized samples were studied. Modified carbons were characterized by elemental analysis and Fourier Transform Infrared spectroscopy (FT-IR) to study the impact of changes in surface chemistry and formation of specific surface groups on adsorption properties. The texture of the samples was characterized by conducting N₂ adsorption/desorption at −196°C. CO₂ capture performance of the samples was investigated using a thermogravimetric analysis (TGA). It was found that in both modification techniques, the presence of nitrogen functionalities on carbon surface generally increased the CO₂ adsorption capacity. The results indicated that oxidation followed by high temperature ammonia treatment (800°C) considerably enhanced the CO₂ uptake at higher temperatures.

Keywords: Activated carbon; Ammonia treatment; Oxidation; Heat treatment; Surface characterization; Carbon dioxide adsorption

Formation of a high hydrophilic/hydrophobic contrast surface on PET substrates by ECR generated sulfur hexafluoride plasma by Miao-Ju Chuang; Ann-Kuo Chu (pp. 3943-3947).

▶ High hydrophilic/hydrophobic contrast surfaces on PET substrates. ▶ This was accomplished using a mask and by controlling the distance of the mask to the substrate in SF₆ plasma. ▶ The best contract in water contact angle obtained from the treated PET samples was larger than 100°.High hydrophilic/hydrophobic contrast surfaces on polyethylene terephthalate (PET) substrates were formed by shadow mask technique in electron cyclotron resonance generated sulfur hexafluoride plasma atmosphere. The X-ray photoelectron spectroscopy (XPS) analyses indicate that the unmasked PET surfaces contained a high proportion of the CF₂–CF₂ groups, and therefore were hydrophobic with large water contact angle. However, the surface wettability was found to increase drastically on the masked PET surfaces. This could be resulted from a mass of COF (acid fluoride) compounds observed by XPS on the masked film surfaces. The COF compounds could react with atmospheric moisture to form –COOH groups, which in turn increased the surface wettability. In addition, the surface wetting property of the masked areas was found to change significantly with the plasma treatment time, the mask-to-substrate distance and the storage time after the treatment. The best contract in water contact angle obtained from the treated PET samples was larger than 100° after 168h of storage.

Keywords: Hydrophilic; Hydrophobic; X-ray photoelectron spectroscopy (XPS); Polyethylene terephthalate (PET)

Leakage current and sub-bandgap photo-response of oxygen-plasma treated GaN Schottky barrier diodes by Fuxue Wang; Hai Lu; Xiangqian Xiu; Dunjun Chen; Ping Han; Rong Zhang; Youdou Zheng (pp. 3948-3951).

▶ GaN surface is treated by oxygen plasma in an ICP etching system. ▶ GaN-based Schottky barrier diodes are then fabricated. ▶ The treated diodes exhibit reduced leakage current in low reverse bias range. ▶ The diodes have larger sub-bandgap photoresponse due to newly-generated surface defects.The effect of oxygen plasma treatment on the performance of GaN Schottky barrier diodes is studied. The GaN surface is intentionally exposed to oxygen plasma generated in an inductively coupled plasma etching system before Schottky metal deposition. The reverse leakage current of the treated diodes is suppressed in low bias range with enhanced diode ideality factor and series resistance. However, in high bias range the treated diodes exhibit higher reverse leakage current and corresponding lower breakdown voltage. The X-ray photoelectron spectroscopy analysis reveals the growth of a thin GaO_x layer on GaN surface during oxygen plasma treatment. Under sub-bandgap light illumination, the plasma-treated diodes show larger photovoltaic response compared with that of untreated diodes, suggesting that additional defect states at GaN surface are induced by the oxygen plasma treatment.

Keywords: GaN; Schottky barrier diode; Oxygen plasma treatment; Leakage current

Composition-dependent phase separation effects of organic solar cells using P3HT:PCBM as active layer and chromium oxide as hole transporting layer by Pingli Qin; Guojia Fang; Nanhai Sun; Xi Fan; Qiao Zheng; Fei Chen; Jiawei Wan; Xingzhong Zhao (pp. 3952-3958).

▶ With the help of the UV/visible spectrophotometer, optical microscopy and scanning electron microscope, we found that the cluster of PCBM at the interface or surface was affected by Al cathode, the composition of the blends and thermal annealing. ▶ Organic solar cells (OSCs) based on blends of poly (3-hexylthiophene) and fullerene derivative [6,6]-phenyl-C₆₁ butyric acid methyl ester have been fabricated with p-type chromium oxide film as hole-transporting layer, which has not reported. ▶ The disc-like shape crystals of PCBM substituted for the needle-like ones at higher PCBM compositions at the ATL/Al interface, which led to stronger contacts and bigger.Phase separation of the poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) active layer (ATL) was investigated by varying their relative ratio in the organic solar cells (OSCs). With the help of the UV/visible spectrophotometer, optical microscopy and scanning electron microscope, we found that the cluster of PCBM at the interface or surface was affected by Al cathode, the composition of the blends and thermal annealing. The disc-like shape crystals of PCBM substituted for the needle-like ones at higher PCBM compositions at the ATL/Al interface, which led to stronger contacts and bigger contact area. It could make short circuit current density increase, but may affect the blend morphology and result in parallel resistance and open circuit voltage decreased with the PCBM ratio increasing from 40 to 60%. The microstructure of the P3HT:PCBM ATL, determined by the composition dependent phase separation, supported the optimized performance of the OSCs with the composition of 40–50% PCBM.

Keywords: Organic solar cell; Phase separation; Interface; Active layer

Superhydrophobic alumina surface based on stearic acid modification by Libang Feng; Hongxia Zhang; Pengzhi Mao; Yanping Wang; Yang Ge (pp. 3959-3963).

▶ Chemicals without fluoroalkylsilane is used as the water-repellent agent in this method. ▶ The process for the grafting of hydrophobic agent is facile. ▶ The superhydrophobic alumina surface takes on an uneven flowerlike structure.A novel superhydrophobic alumina surface is fabricated by grafting stearic acid layer onto the porous and roughened aluminum film. The chemical and phase structure, morphology, and the chemical state of the atoms at the superhydrophobic surface were investigated by techniques as FTIR, XRD, FE-SEM, and XPS, respectively. Results show that a super water-repellent surface with a contact angle of 154.2° is generated. The superhydrophobic alumina surface takes on an uneven flowerlike structure with many nanometer-scale hollows distribute in the nipple-shaped protrusions, and which is composed of boehmite crystal and γ-Al₂O₃. Furthermore, the roughened and porous alumina surface is coated with a layer of hydrophobic alkyl chains which come from stearic acid molecules. Therefore, both the roughened structure and the hydrophobic layer endue the alumina surface with the superhydrophobic behavior.

Keywords: Alumina; Superhydrophobic; Stearic acid; Roughened; Porous; Structure

Structural properties and electrical characteristics of high- k Dy₂O₃ gate dielectrics by Tung-Ming Pan; Wei-Tsung Chang; Fu-Chien Chiu (pp. 3964-3968).

▶ We report the structural properties and electrical characteristics of thin Dy₂O₃ dielectrics deposited on Si substrates through reactive sputtering. ▶ The structural and morphological features of these films after postdeposition annealing were studied by X-ray diffraction and X-ray photoelectron spectroscopy. ▶ We found that Dy₂O₃ dielectrics annealed at 700°C exhibit a thinner capacitance equivalent thickness and better electrical properties.This paper describes the structural properties and electrical characteristics of thin Dy₂O₃ dielectrics deposited on silicon substrates by means of reactive sputtering. The structural and morphological features of these films after postdeposition annealing were studied by X-ray diffraction and X-ray photoelectron spectroscopy. It is found that Dy₂O₃ dielectrics annealed at 700°C exhibit a thinner capacitance equivalent thickness and better electrical properties, including the interface trap density and the hysteresis in the capacitance–voltage curves. Under constant current stress, the Weibull slope of the charge-to-breakdown of the 700°C-annealed films is about 1.6. These results are attributed to the formation of well-crystallized Dy₂O₃ structure and the reduction of the interfacial SiO₂ layer.

Keywords: Dy; ₂; O; ₃; film; Gate dielectric; Postdeposition annealing (PDA)

Sputtering pressure effects on the structural and mechanical properties of TiVCr alloy coatings by Du-Cheng Tsai; Yen-Lin Huang; Sheng-Ru Lin; De-Ru Jung; Fuh-Sheng Shieu (pp. 3969-3973).

▶ The TiVCr coatings have a composite structure with amorphous and bcc crystal phases. ▶ The driving force for the crystallization is the intrinsic stress in films. ▶ Higher sputtering pressure leads to increase in void density and decrease in hardness.In this study, TiVCr alloy coatings were deposited on Si substrates by magnetron sputtering system at different working pressures (0.33–1Pa). The TiVCr coatings have a composite structure with amorphous and body-centered cubic (bcc) crystal phases comprised of bundles of fine fibrous structures and V-shaped columnar structures, respectively. Compared with the amorphous zone, the crystalline zone has a denser and more compact structure. The coating microstructure became more porous as working pressure increased. Consequently, the crystal zones of the deposited coatings at 0.33Pa obtained higher hardness (11.6GPa) while the deposited coatings at 1Pa achieved lower hardness (4.5GPa).

Keywords: Coating materials; Alloy materials; Thin films; Vapor deposition; Crystal structure; Microstructure

Optical and electrochemical properties of Cu-doped NiO films prepared by electrochemical deposition by Lili Zhao; Ge Su; Wei Liu; Lixin Cao; Jing Wang; Zheng Dong; Meiqin Song (pp. 3974-3979).

▶ Films containing Cu present the structure of nanorods. ▶ Cu doping increases the crystallinity of the films. ▶ Absorption edges of Cu doped NiO films exhibit an obvious red-shift. ▶ The film with the Cu/Ni molar ratio of 1:8 has better electrochromic properties. ▶ Cu-doped films show better reversibility and faster response time.Cu-doped nickel oxide (NiO) thin films were prepared by electrochemial deposition (cathodic deposition) technique onto the fluorine doped tin oxide (F: SnO₂; FTO) coated glass substrates from organic solutions. Effects of Cu content on the morphology, structure, optical and electrochromic properties of NiO films were investigated by means of scanning electron microscope (SEM), X-ray diffraction (XRD), ultraviolet–visible spectrophotometer (UV–vis) and cyclic voltammetry (CV), respectively. SEM images indicated the formation of nanorods after Cu was added. The films were formed with amorphous or short-range ordered NiO grains and a trace of face-centered cubic Ni_xCu1−_xO confirmed by XRD. The transmittances of both bleached state and colored state were significantly lowered when Cu was added. The NiO films doped with Cu (the molar ratio was 1/8) exhibited the optimum electrochromic behavior with a variation of transmittance (Δ T) up to ∼80% at the wavelength range of 350–600nm. Cu doping reduces the response time for both the coloring and bleaching states, and the reversibility of the redox reaction was increased as well.

Keywords: Cu-doped NiO films; Cathodic deposition; Electrochromic; Variation of transmittance

Corrosion behaviour of sintered NdFeB coated with Al/Al₂O₃ multilayers by magnetron sputtering by Shoudong Mao; Hengxiu Yang; Feng Huang; Tingting Xie; Zhenlun Song (pp. 3980-3984).

▶ Al/Al₂O₃ multilayers were deposited by magnetron sputtering on NdFeB magnets. ▶ The columnar structure was effectively inhibited in the Al/Al₂O₃ multilayers. ▶ The multilayers presented excellent corrosion resistance.Al/Al₂O₃ multilayers were deposited on sintered NdFeB magnets to improve the corrosion resistance. The amorphous Al₂O₃ films were used to periodically interrupt the columnar growth of the Al layers. The structure of the multilayers was investigated by Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HRTEM). It was found that the columnar structure was effectively inhibited in the multilayers. Subsequent corrosion testing by potentiodynamic polarization in 3.5wt.% NaCl and neutral salt spray test (NSS) revealed that the Al/Al₂O₃ multilayers had much better corrosion resistance than the Al single layer. Furthermore, for multilayers with similar thickness, the corrosion resistance was improved as the period decreased.

Keywords: NdFeB; Aluminum; Magnetron sputtering; Corrosion resistance

Microstructure and corrosion properties of diode laser melted friction stir weld of aluminum alloy 2024 T351 by Samar Jyoti Kalita (pp. 3985-3997).

▶ Effects of laser melting on a friction stir weld of aluminum alloy 2024 was studied. ▶ Melting produced fine microstructure at the surface free from precipitates. ▶ The melt zone exhibited epitaxially grown columnar grains. ▶ Immersion test (21 days) showed no pitting on melted region. ▶ The pit nucleation resistance was noticeably increased.Friction stir welding is a promising solid state joining process for high strength aluminum alloys. Though friction stir welding eliminates the problems of fusion welding as it is performed below melting temperature ( T_m), it creates severe plastic deformation. Friction stir welds of some aluminum alloys exhibit relatively poor corrosion resistance. This research enhanced the corrosion properties of such welds through diode laser surface melting.A friction stir weld of aluminum alloy 2024 T351 was laser melted using a 1kW diode laser. The melt-depth and microstructure were investigated using optical and scanning electron microscopy. The melt zone exhibited epitaxially grown columnar grains. At the interface between the melted and the un-melted zone, a thick planar boundary was observed. Energy dispersive spectroscopy analyzed the redistribution of elemental composition. The corrosion properties of the laser melted and native welds were studied in aqueous 0.5M sodium chloride solution using open circuit potential and cyclic potentiodynamic polarization. The results show noticeable increase in the pit nucleation resistance (390mV) after the laser surface treatment. The repassivation potential was nobler to the corrosion potential after the laser treatment, which confirmed that the resistance to pit growth was improved.

Keywords: Laser surface melting; Friction stir weld; Aluminum alloy 2024; Cyclic potentiodynamic polarization

Structural and optical properties study of nanocrystalline Si (nc-Si) thin films deposited on porous aluminum by plasma enhanced chemical vapor deposition by M. Ghrib; M. Gaidi; N. Khedher; T. Ghrib; M. Ben Salem; H. Ezzaouia (pp. 3998-4003).

▶ In this paper we report detail investigation and correlation between micro-structural and optical properties of nano-crystalline silicon (nc-Si) deposited by plasma enhancement chemical vapor deposition (PECVD) on porous aluminum structure. ▶ The effect of anodisation currents on the microstructure of aluminium surface layer and nc-Si films was systematically studied by Atomic Force Microscopy (AFM) and Tranmission Electron microscopy (TEM), Raman spectroscopy and X-ray diffraction (XRD). ▶ The optical constants ( n and k as a function of wavelength) of the films were obtained using variable angle spectroscopic ellipsometry (SE) in the UV-vis-NIR regions.In this paper we report detail investigation and correlation between micro-structural and optical properties of nanocrystalline silicon (nc-Si) deposited by plasma enhancement chemical vapor deposition (PECVD) on porous aluminum structure. The influence of the microstructure of the nc-Si thin films on their optical properties was investigated through an extensive characterization. The effect of anodisation currents on the microstructure of aluminum surface layer and nc-Si films was systematically studied by atomic force microscopy (AFM) and transmission electron microscopy (TEM), Raman spectroscopy and X-ray diffraction (XRD). The optical constants ( n and k as a function of wavelength) of the films were obtained using variable angle spectroscopic ellipsometry (SE) in the UV–vis–NIR regions. The silicon layer (SL) was modeled as a mixture of void, crystalline silicon and aluminum using the Bruggeman approximation. Based on this full characterization, it is demonstrated that the optical characteristics of the films are directly correlated to their micro-structural properties. A very bright photoluminescence (PL) was obtained and find to depend on anodisation current.

Keywords: Porous aluminum; Nanocrystalline silicon (nc-Si); Ellipsometry; Photoluminescence (PL)

DFT study on surface properties and dissolution trends of Al(100) surfaces doped with Zn, Ga, In, Sn and Pb by Jiancai Liu; Xinming Zhang; Mingan Chen; Li Li; Bing Zhu; Jianguo Tang; Shengdan Liu (pp. 4004-4009).

Display Omitted▶ The nature of the impurity atom species and the monolayer coverage have effect on the surface energy of Me–Al(100) surfaces. ▶ The work function decreases almost linearly with the monolayer coverage of solute elements Me. ▶ With increasing Me coverage, the stability of Al atoms in Me–Al(100) surfaces are weakened. ▶ A negative electrode potential shift for Me–Al(100) surfaces compared with pure Al(100) surfaces.In this paper, the properties and dissolution trends of the surfaces doped with different metal atoms on the Al(100) surface were investigated by the density functional theory calculations. A surface impurity model was proposed by replacing the topmost surface layer Al atoms by Me (Me=Zn, Ga, In, Sn and Pb) atoms with the coverage of 1/9, 1/4, 1/2, and 3/4 monolayer, respectively. Results show that the surface energy of Me–Al(100) surfaces depends primarily on the nature of the impurity atom species and the monolayer coverage. The work function of Me–Al surfaces is smaller than that of pure Al(100) surface, and decreases almost linearly with the amount of Me. It is found that the Me–Al alloys are more easily dissolvable than the pure Al, due to the fact that the electrochemical dissolution potential shifts were negative for all Me–Al(100) surfaces with respect to the clean pure Al(100) surface.

Keywords: Density functional theory; Electrochemical dissolution potentials; Surface energy; Work function; Mülliken charge population

Structural and optical properties of the SiCN thin films prepared by reactive magnetron sputtering by Yinqiao Peng; Jicheng Zhou; Baoxing Zhao; Xiaochao Tan; Zhichao Zhang (pp. 4010-4013).

▶ The optical band gap of the films monotonically decreases with the increase of C₂H₂ flow rate. ▶ There is not Si–C bond in the surface of the SiCN film. ▶ The bonding structures in the surface of the SiCN film are different from those in the SiCN film. ▶ The SiCN films deposited by reactive magnetron sputtering have an even surface.Silicon carbonitride (SiCN) thin films were deposited on n-type Si (100) and glass substrates by reactive magnetron sputtering of a polycrystalline silicon target in a mixture of argon (Ar), nitrogen (N₂) and acetylene (C₂H₂). The properties of the films were characterized by scanning electron microscope with an energy dispersive spectrometer, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectrometry and ultraviolet-visible spectrophotometer. The results show that the C₂H₂ flow rate plays an important role in the composition, structural and optical properties of the films. The films have an even surface and an amorphous structure. With the increase of C₂H₂ flow rate, the C content gradually increases while Si and N contents have a tendency to decrease in the SiCN films, and the optical band gap of the films monotonically decreases. The main bonds are Si–O, N–H_n, C–C, C–N, Si–N, Si–C and Si–H in the SiCN films while the chemical bonding network of Si–O, C–C, C–O, C–N, N–Si and CN is formed in the surface of the SiCN films.

Keywords: PACS; 81.15.Cd; 73.61.Jc; 78.66.−w; 78.30.−j; 82.80.PvSiCN; Reactive magnetron sputtering; C content; Structure; Optical band gap

Kinetics and mechanical study of plasma electrolytic carburizing for pure iron by F. Çavuşlu; M. Usta (pp. 4014-4020).

▶ This study was driven by the lack of studies on the plasma electrolytic surface carburizing of pure iron. ▶ At the present study, the pure iron samples were carburized in aqueous solution of 20% glycerin. ▶ The samples were carburized at 750°C, 800°C, 900°C and 950°C temperatures for 5, 10 and 30min. ▶ The effect of temperature, time and the amount of glycerin on the kinetics of this process was evaluated.In this work, plasma electrolytic surface carburizing of pure iron in aqueous solution consisting of water, glycerin and NH₄Cl was investigated. Surface carburizing was carried out in 20% glycerin solution treated at 750°C, 800°C, 900°C and 950°C temperatures for 5, 10 and 30min. The formation of hard carbon-rich layer on the surface of pure iron was confirmed by XRD analysis. Metallographic and SEM studies revealed a rough and dense carburized layer on the surface of the pure iron. Experimental results showed that the thickness of the carburized layers changes with the time and temperature. The average thickness of the carburized layer ranged from 20 to 160μm. The hardness of the carburized samples decreased with the distance from the surface to the interior of the test material. The average hardness values of the carburized layers on the substrate ranged 550–850HV, while the hardness of the substrate ranged from 110HV to 170HV. The dominant phases formed on the pure iron were found to be a mixture of cementite (Fe₃C), martensite (Fe+C) and austenite (FCC iron) confirmed by XRD. Wear resistance in all plasma electrolytic carburized samples is considerably improved in relation to the untreated specimen. After carburizing, surface roughness of the samples was increased. Friction coefficients were also increased because of high surface roughness.

Keywords: Pure iron; Carburizing; Aqueous solution; Plasma electrolytic surface hardening

Enhanced dielectric and ferroelectric properties of Pb1−3 x_/2La_x(Zr_0.5Ti_0.5)O₃ thin films with low lanthanum substitution by S.Q. Zhang; W.L. Li; L.D. Wang; N. Li; W.D. Fei (pp. 4021-4025).

▶ Large dielectric constants of the films are obtained within range of 800–1600 which are almost comparable to those observed in bulk ceramics. ▶ Low lanthanum substitution contributes to higher electric properties of the films due to the improvement of non-180° domain wall mobility as well as the stabilization of tetragonal phase.Effects of lanthanum (La) substitution (0.003≤ x≤0.015) on the dielectric and ferroelectric properties of Pb(Zr_0.5Ti_0.5)O₃ thin films have been investigated. The films were synthesized on the Pt (111)/Ti/SiO₂/Si (100) substrates by a sol–gel method. Large dielectric constants of the films are obtained within range of 800–1600 which are almost comparable to those observed in bulk ceramics. The films also show improved remnant polarization values and reduced coercive field values with the increasing addition of La substitution. Our results suggest that low La substitution contributes to enhance film electric properties due to the improvement of non-180° domain wall mobility as well as the stabilization of tetragonal phase.

Keywords: Ferroelectric thin films; Sol–gel; La substitution; Dielectric properties; Ferroelectricity

Thickness study of Al:ZnO film for application as a window layer in Cu(In1−_xGa_x)Se₂ thin film solar cell by M.M.Islam; S. Ishizuka; A. Yamada; K. Matsubara; S. Niki; T. Sakurai; K. Akimoto (pp. 4026-4030).

▶ Structural, electrical and optical properties of various Al:ZnO thin film were studied. ▶ Electrical and structural properties of Al:ZnO film improved with increasing its thickness, ▶ The optical properties of Al:ZnO film degraded with thickness. ▶ J_sc of the CIGS solar cell was influenced by Al:ZnO layer thickness. ▶ Electrically and optically optimized Al:ZnO window give best efficiency solar cell.Structural, electrical and optical properties of Al doped ZnO (Al:ZnO) thin film of various thicknesses, grown by radio-frequency magnetron sputtering system were studied in relation to the application as a window layer in Cu(In1−_xGa_x)Se₂ (CIGS) thin film solar cell. It was found that the electrical and structural properties of Al:ZnO film improved with increasing its thickness, however, the optical properties degraded. The short circuit current density, J_sc of the fabricated CIGS based solar cells was significantly influenced by the variation of the Al:ZnO window layer thickness. Best efficiency was obtained when CIGS solar cell was fabricated with electrically and optically optimized Al:ZnO window layer.

Keywords: Solar cell; Cu(In; 1−; _x; Ga; _x; )Se; ₂; Al:ZnO layer thickness; Efficiency

Structural and optical properties of ZnO thin films prepared by sol–gel method with different thickness by Linhua Xu; Xiangyin Li; Yulin Chen; Fei Xu (pp. 4031-4037).

▶ It is found that the thickness has a great effect on the structural and optical properties of ZnO thin films deposited from sol-gel method. ▶ With the increase of film thickness, both the crystalline quality and ultraviolet emission of ZnO thin film are gradually improved. ▶ The growth process of highly c-axis oriented ZnO thin films prepared by sol-gel method is a self-template process. ▶ With the increase of film thickness, a growth mode from vertical growth to lateral growth is found and the transition point is between 270 and 360nm thickness.In this work, ZnO thin films with different thickness were prepared by sol–gel method on glass substrates and the structural and optical properties of these films were studied by X-ray diffractometer, atomic force microscope, UV–visible spectrophotometer, ellipsometer and fluorophotometer, respectively. The structural analyses show that all the samples have a wurtzite structure and are preferentially oriented along the c-axis perpendicular to the substrate surface. The growth process of highly c-axis oriented ZnO thin films derived from sol–gel method is a self-template process. With the increase of film thickness, the structural disorder decreases and the crystalline quality of the films is gradually improved. A transition of crystal growth mode from vertical growth to lateral growth is observed and the transition point is found between 270 and 360nm thickness. The optical analyses show that with the increase of film thickness, both the refractive index and ultraviolet emission intensity are improved. However, the transmittance in the visible range is hardly influenced by the film thickness, and the averages are all above 80%.

Keywords: PACS; 61.05.cp; 68.37.Ps; 68.55.−a; 78.55.EtZnO thin films; Film thickness; Sol–gel method; Growth mode; Optical properties

A contact angle and ToF-SIMS study of SAM–thiol interactions on polycrystalline gold by Michal Tencer; Heng-Yong Nie; Pierre Berini (pp. 4038-4043).

▶ Interaction of a PEG terminated SAM on non-textured gold with dodecanethiol in solution leads to no noticeable exchange over the first 3 hrs and then asymptotically approaches ∼50% replacement. ▶ The reverse exchange (dodecanethiol SAM with TPEG) does not show such an induction time and proceeds to completion.A process of chemical differentiation of neighboring Au features on a substrate (for biosensing applications) involves a step, where after electrochemical removal of a self-assembled monolayer (SAM) from one feature, another SAM is deposited onto it by incubation with a different thiol. During this incubation step, other undesorbed features are also exposed to this thiol which may lead to a partial SAM–thiol exhange, the extent of which is a function of time. Here, such surface reactions were followed on polystalline Au in both directions using contact angle measurements and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The thiols involved were dodecanethiol (DDT) which forms SAM promoting adsorption of proteins and 11-mercaptoundecyl)tri(ethylene glycol) (TPEG) whose SAM prevents such adsorption. The surface reactions in both directions cannot be described by a simple pseudo-first-order kinetics. It was found that while the DDT SAM interaction with a TPEG solution leads eventually to a total replacement, the reverse process, TPEG SAM interaction with DDT, leads to no noticeable exchange over the first 3h and then asymptotically approaches ∼50% replacement.

Keywords: SAMs; Thiols; Exchange; Contact angle; ToF-SIMS; Gold

Influence of TaCl₅ partial pressure on texture structure of TaC coating deposited by chemical vapor deposition by Zhao-Ke Chen; Xiang Xiong; Ying Long (pp. 4044-4050).

Display Omitted▶ TaC coating are deposited at 800°C and 1200°C with different TaCl5 pressure by chemical vapor deposition. ▶ Super-saturation is responsible for different coating morphology and texture structure. ▶ The growth mechanism of the texture coating is explained by the competitive growth model. ▶ A diffusion model of deposition species around step-edge-corner was proposed.TaC was deposited on graphite substrate with different TaCl₅ partial pressure at 800°C and 1200°C by chemical vapor deposition. Microstructures and texture structures of the prepared coatings were researched with X-ray diffraction and scanning electronic microscopy. When the coating deposition process is controlled by surface reaction kinetics (800°C), TaCl₅ partial pressure had little influence on the microstructure and texture structure of the coating. When the coating formation process is controlled by diffusion kinetics (1200°C), the microstructure, texture structure of the prepared TaC grains vary greatly with TaCl₅ partial pressure. In the diffusion controlled process, the increasing of TaCl₅ partial pressure will result in the changing of gas supersaturation, and then the occurrence of secondary nucleation, which is the main reason for the changing of coating morphology and texture structure. With the help of competitive growth in (100) and (111) directions, the formation mechanism of the different texture coatings are discussed in detail. In addition, a diffusion model of deposition species around step-edge-corner was also proposed to explain the growth mechanism of the texture coatings.

Keywords: TaC; Chemical vapor deposition; Preferential orientation; Surface morphology

Thickness effect on the evolution of morphology and optical properties of ZnO films by Aihua Zhong; Jin Tan; Huali Huang; Shengchang Chen; Man Wang; Sai Xu (pp. 4051-4055).

▶ The grain size increases obviously with the increase of film thickness. ▶ The grain shape strongly depends on thickness. ▶ The emission center shifts from ultraviolet to blue region. ▶ Film thickness has a complex effect on the electrical properties of ZnO.N–Al co-doped ZnO films with various thicknesses were deposited on glass substrates by ultrasonic spray pyrolysis (USP). The crystalline microstructure, morphology, distribution of elements and photoluminescence properties of ZnO films were characterized by X-ray diffraction (XRD), field emission scanning microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS) and photoluminescence (PL) spectroscopy. The XRD and FESEM results show that with the increase of film thickness the grain size increases and the grain shape changes from regular hexagonal sheet-like to wedge-shaped, even pyramidal. The PL spectra illustrate that there is an obvious red-shift for the emission center from ultraviolet to blue region, and the intensities of defects emissions increase with the increase of thickness. In addition, the electrical properties are proved to be strongly affected by film thickness.

Keywords: Film thickness; Morphology; Photoluminescence; ZnO films

Sonochemical synthesis, size controlling and gas sensing properties of NiO nanoparticles by Alireza Aslani; Vahid Oroojpour; Mehrab Fallahi (pp. 4056-4061).

▶ In this work, we synthesized NiO Nano-sized particles (NiO-NP) by using a simple sonochemical method for the preparation of NiO nanoparticles directly without any additive from nickel acetate solutions. ▶ NiO-NP based chemoresistive gas sensors were realized and gas sensing tests towards NO₂ and CO were performed, showing promising results compared with the NiO thin films gas sensors. ▶ The gas sensing tests on resulting devices show remarkable response to NO₂ even at very low operating temperatures and good responses towards CO. ▶ This result is attributed to the preparation of highly Nano-sized oxide particles and to their processing for the device realization. In fact, the final sensing layer results a porous and not sintered structure resulting in extensive interaction with the gases. ▶ The results obtained are very promising and stimulating and in further developing of NiO-NP based sensor devices.Nanoparticles of NiO (NP-NiO) were prepared by a novel sonochemical route from Ni acetate and sodium hydroxide without any requirement of calcinations steps at high temperature and without surfactants. Drop casting of the nanocrystals onto alumina substrates allowed the fabrication of gas sensing devices, which were tested towards NO₂ and CO and showed promising results. At low working temperature, the NiO nanoparticles based sensors are selective to nitrogen oxide; in fact a good sensitivity is shown at 200°C at low concentration (2ppm), while at temperature above 350°C, high responses are obtained for carbon monoxide. The results obtained are stimulating for further developing of NP-NiO based sensor devices.

Keywords: NiO nanoparticles; NO; ₂; CO; Gas sensor

Atmospheric air-plasma treatment of polyester fiber to improve the performance of nanoemulsion silicone by Mazeyar Parvinzadeh; Izadyar Ebrahimi (pp. 4062-4068).

▶ Introduction of plasma before silicone treatment of PET as a novel research work. ▶ Enhancement of wetting properties of the polyester after plasma. ▶ Uniform coating of silicone on PET.Influence of atmospheric air plasma treatment on performance of nanoemulsion silicone softener on polyethylene terephthalate fibers was investigated by the use of fourier transform infrared spectroscopy (FTIR), bending lengths (BL), wrinkle recovery angles (WRA), fiber friction coefficient analysis (FFCA), moisture absorbency (MA), scanning electron microscopy (SEM) and reflectance spectroscopy (RS). Results indicated that the plasma pretreatment modifies the surface of fibers and increases the reactivity of substrate toward nanoemulsion silicone. Moisture regain and microscopic tests showed that the combination of plasma and silicone treatments on polyethylene terephthalate can decrease moisture absorption due to uniform coating of silicone emulsion on surface of fibers.

Keywords: Plasma; Polyester; Drapeability; Reflectance

Effect of the surface roughness on interfacial properties of carbon fibers reinforced epoxy resin composites by Wei Song; Aijuan Gu; Guozheng Liang; Li Yuan (pp. 4069-4074).

▶ Aqueous ammonia significantly improve the surface roughness of carbon fibers. ▶ Aqueous ammonia does not obviously change chemical compositions of carbon fibers. ▶ The surface roughness of fibers increases with the increase of the treating time. ▶ Treated fiber with big surface roughness has better interfacial adhesion with resin.The effect of the surface roughness on interfacial properties of carbon fibers (CFs) reinforced epoxy (EP) resin composite is studied. Aqueous ammonia was applied to modify the surfaces of CFs. The morphologies and chemical compositions of original CFs and treated CFs (a-CFs) were characterized by Atomic Force Microscopy (AFM), and X-ray Photoelectron Spectroscopy (XPS). Compared with the smooth surface of original CF, the surface of a-CF has bigger roughness; moreover, the roughness increases with the increase of the treating time. On the other hand, no obvious change in chemical composition takes place, indicating that the treating mechanism of CFs by aqueous ammonia is to physically change the morphologies rather than chemical compositions. In order to investigate the effect of surface roughness on the interfacial properties of CF/EP composites, the wettability and Interfacial Shear Strength (IFSS) were measured. Results show that with the increase of the roughness, the wettabilities of CFs against both water and ethylene glycol improves; in addition, the IFSS value of composites also increases. These attractive phenomena prove that the surface roughness of CFs can effectively overcome the poor interfacial adhesions between CFs and organic matrix, and thus make it possible to fabricate advanced composites based on CFs.

Keywords: Surface roughness; Carbon fiber; Interfacial properties; Composite

Thermal stability of HfO₂ nanotube arrays by Xiaofeng Qiu; Jane Y. Howe; Harry M. Meyer III; Enis Tuncer; M. Parans Paranthaman (pp. 4075-4081).

Display Omitted▶ Highly ordered hafnium oxide nanotube arrays prepared through anodic oxidation. ▶ As-formed HfO₂ nanotubes are amorphous and contain significant amounts of fluorine. ▶ HfO₂ nanotubes are stable up to 700°C in Ar. ▶ HfO₂ nanotube morphology degraded at 900°C in Ar. ▶ Dielectric permittivity values of HfO₂ nanotubes are close to that of bulk literature values.Thermal stability of highly ordered hafnium oxide (HfO₂) nanotube arrays prepared through an electrochemical anodization method in the presence of ammonium fluoride is investigated in a temperature range of room temperature to 900°C in flowing argon atmosphere. The formation of the HfO₂ nanotube arrays was monitored by current density transient characteristics during anodization of hafnium metal foil. Morphologies of the as-grown and post-annealed HfO₂ nanotube arrays were analyzed by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Although monoclinic HfO₂ is thermally stable up to 2000K in bulk, the morphology of HfO₂ nanotube arrays degraded at 900°C. A detailed X-ray photoelectron spectroscopy (XPS) study revealed that the thermal treatment significantly impacted the composition and the chemical environment of the core elements (Hf and O), as well as F content coming from the electrolyte. Possible reasons for the degradation of the nanotube at high temperature were discussed based on XPS study and possible future improvements have also been suggested. Moreover, dielectric measurements were carried out on both the as-grown amorphous film and 500°C post-annealed crystalline film. This study will help us to understand the temperature impact on the morphology of nanotube arrays, which is important to its further applications at elevated temperatures.

Keywords: Hafnium oxide; HfO; ₂; Nanotube arrays; Anodic oxidation; Thermal stability; Dielectric properties

Optimisation of the ammonium sulphide (NH₄)₂S passivation process on In_0.53Ga_0.47As by B. Brennan; M. Milojevic; C.L. Hinkle; F.S. Aguirre-Tostado; G. Hughes; R.M. Wallace (pp. 4082-4090).

▶ (NH₄)₂S passivation parameters investigated for optimal chemical passivation of InGaAs. ▶ XPS and AFM used to determine level of native oxide and surface roughness present. ▶ Variations in (NH₄)₂S concentration, treatment time, temperature and pre-treatment. ▶ 10% (NH₄)₂S for 20min at room temperature provides optimal chemical passivation.The passivation of III–V semiconductor materials with sulphur is widely reported to reduce interface state defects and improve semiconductor device performance. The most common approach utilises ammonium sulphide ((NH₄)₂S), however there are wide variations in the reported processing parameters involved in this procedure. This study provides a comprehensive review of the various parameters used as well as determining the optimal processing conditions in terms of sample pre-treatments, temperature of the (NH₄)₂S solution, length of time the sample is in the solution and (NH₄)₂S concentration, by measuring the level of residual native oxides and surface roughness by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively.

Keywords: InGaAs; Sulphur passivation; Photoemission; Surface roughness; Native oxide; Ammonium sulphide; Chemical passivation

Improvement of electrospun polymer fiber meshes pore size by femtosecond laser irradiation by Esther Rebollar; Diego Cordero; Albino Martins; Stefano Chiussi; Rui L. Reis; Nuno M. Neves; Betty León (pp. 4091-4095).

▶ Micropores can be formed in polymeric fiber meshes by laser irradiation. ▶ Pore size can be controlled by controlling laser parameters. ▶ Chemistry of the fibers is kept after femtosecond irradiation. ▶ Integrity of the laser irradiated fibers is kept (no sealed pores).Polymer meshes have recently attracted great attention due to their great variety of applications in fields such as tissue engineering and drug delivery. Poly(ɛ-caprolactone) nanofibers were prepared by electrospinning giving rise to porous meshes. However, for some applications in tissue engineering where, for instance, cell migration into the inner regions of the mesh is aimed, the pore size obtained by conventional techniques is too narrow. To improve the pore size, laser irradiation with femtosecond pulses (i.e., negligible heat diffusion into the polymer material and confined excitation energy) is performed. A detailed study of the influence of the pulse energy, pulse length, and number of pulses on the topography of electrospun fiber meshes has been carried out, and the irradiated areas have been studied by scanning electron microscopy, contact angle measurements and spectroscopic techniques. The results show that using the optimal laser parameters, micropores are formed and the nature of the fibers is preserved.

Keywords: Pore size; Femtosecond laser; Fiber mesh; Electrospinning; Laser ablation

Immobilization of naringinase on mesoporous molecular sieve MCM-41 and its application to debittering of white grapefruit by Shengjiao Lei; Yongxia Xu; Gang Fan; Ming Xiao; Siyi Pan (pp. 4096-4099).

▶ In the present report, naringinase has been adsorbed on to MCM-41 by cross linking agent glutaraldehyde. ▶ The results showed that the immobilized preparation of naringinase seemed to be very suitable for debitterring of grapefruit. ▶ The properties of the free and immobilized naringinase such as hydrolytic activity, thermal stability, reusability and kinetic behavior were investigated, using naringin hydrolysis. ▶ The impact of naringin enzymatic hydrolysis in the white grapefruits was evaluated. ▶ Furthermore, the molecular sieve MCM-41 and MCM41–naringinase matrix were characterized by FT-IR, elemental analysis and the nitrogen adsorption–desorption isotherms.Naringinase was bound to mesoporous silica MCM-41 via adsorption with glutaraldehyde and used to debitter white grapefruit. K_m value of the immobilized naringinase was lower than that of free naringinase. The immobilized catalysts showed excellent thermal stability and storage stability and could be recycled 6 times retained about 44.57% activities. The unaltered structural order of the prepared catalyst was characterized with reference to bulky and surface properties by infrared spectroscopy (FT-IR), elemental analysis and nitrogen adsorption–desorption isotherms analysis.

Keywords: Naringinase; Immobilization; MCM-41; Debittering

Preparation and luminescence of water soluble poly (N-vinyl-2-pyrrolidone)/LaF₃:Eu³⁺ nanocrystals by Jianshe Wang; Yanxia Li; Qianqing Ge; Hongchang Yao; Zhongjun Li (pp. 4100-4104).

▶ Poly (N-vinyl-2-pyrrolidone) capped LaF₃:Eu³⁺ nanocrystals have been prepared. ▶ The nanocrystals can be readily dispersed in water, forming transparent colloidal solution, which display unique red luminescence under ultraviolet excitation. ▶ The nanocrystals may have promising applications for fluorescent labels.Lanthanide-doped luminescent nanocrystals have great potential as biological luminescent labels, but their use has been limited because of most of these nanocrystals are hydrophobic. In this work, water soluble LaF₃:Eu³⁺ down-conversion nanocrystals were prepared by encapsulated individual nanocrystals with polyvinylpyrrolidone (PVP). Their morphology, surface structure and luminescence properties were explored in detail. The results indicate that these nanocrystals can be readily dispersed in water, forming a stable and transparent colloidal solution. The colloidal solution displayed unique red luminescence with high emission intensity under ultraviolet excitation. These results suggest that these nanocrystals have great potential as luminescent labeling materials for biological applications.

Keywords: Optical materials; Photoluminescence spectroscopy; Luminescence

Interfacial reactions and oxidation behavior of Al₂O₃ and Al₂O₃/Al coatings on an orthorhombic Ti₂AlNb alloy by H.Q. Li; Q.M. Wang; J. Gong; C. Sun (pp. 4105-4112).

▶ The interfacial reactions of Al₂O₃/Ti₂AlNb and Al₂O₃/Al/Ti₂AlNb specimens at 750°C were investigated. ▶ The Al₂O₃/Al/Ti₂AlNb specimens exhibited excellent oxidation resistance at 750°C. ▶ No internal oxidation or oxygen and nitrogen dissolved zone could be observed in the coated alloy with Al₂O₃/Al coating.The uniform and dense Al₂O₃ and Al₂O₃/Al coatings were deposited on an orthorhombic Ti₂AlNb alloy by filtered arc ion plating. The interfacial reactions of the Al₂O₃/Ti₂AlNb and Al₂O₃/Al/Ti₂AlNb specimens after vacuum annealing at 750°C were studied. In the Al₂O₃/Ti₂AlNb specimens, the Al₂O₃ coating decomposed significantly due to reaction between the Al₂O₃ coating and the O-Ti₂AlNb substrate. In the Al₂O₃/Al/Ti₂AlNb specimens, a γ-TiAl layer and an Nb-rich zone came into being by interdiffusion between the Al layer and the O-Ti₂AlNb substrate. The γ-TiAl layer is chemically compatible with Al₂O₃, with no decomposition of Al₂O₃ being detected. No internal oxidation or oxygen and nitrogen dissolution zone was observed in the O-Ti₂AlNb alloy. The Al₂O₃/Al/Ti₂AlNb specimens exhibited excellent oxidation resistance at 750°C.

Keywords: Al; ₂; O; ₃; O-Ti; ₂; AlNb alloy; Interfacial reaction; Oxidation

Analysis of a fibre laser welding case study, utilising a matrix flow chart by J. Karlsson; A.F.H. Kaplan (pp. 4113-4122).

▶ Improved documentation and generalization of knowledge is desired. ▶ For varied parameters, shapes are categorized into top and root surface classes. ▶ The Matrix Flow Chart is developed to increase the pictoral presentation of results. ▶ Different trends of defects and shapes are found by changing the input parameters. ▶ Formulation of trends in the MFC is made as a generalization starting point.For fibre laser welding of an eccentric corner joint, the quality of the resulting weld cross section was studied with respect to the dependence on process parameters like lateral laser beam alignment, beam inclination, focal plane position or welding speed. The complex load situation of the support beamer was simplified to bending of one corner. Due to fatigue load, the weld properties causing the peak stress are essential, in particular the top and root shape of the weld cross section. For the parameters varied, the resulting shapes were categorized into different top and root classes, determined by certain key dimensions, considering also welding defects like undercuts. The shapes are boundary conditions for Finite Element Analysis of the joint under load for quantitative comparative analysis of the maximum stress. As two high strength steel grades were joined, the hardness transition across the weld was of interest, too. High speed imaging of the weld pool surface shape provided additional information on the relation between the parameter input and quality output. The different trends identified were discussed and guidelines were derived. As the systematic documentation of results is unsatisfactory in welding, a new method was developed and applied for the first time, called the Matrix Flow Chart. It enables an illustrative view on the resulting welding trends in a combined manner and is extendable by other researchers.

Keywords: Laser welding; Parameters; Geometry; Load; Shape; Defect

Effects of non-flat contact and interference on self-assembled monolayers under sliding friction by Cheng-Da Wu; Te-Hua Fang; Yan-Jiun Huang (pp. 4123-4128).

Snapshots of the sliding process at an interference of 0.3nm as the θ value of the slider is (a) 5°, (b) 10°, (c) 15° and (d) 20°, respectively. The number of CH₂ molecules is 11 per chain.Display Omitted▶ The contact area and exerted normal force increase with decreasing the tilt angle of the slider. ▶ The periods of normal force and shear force are delayed as the tilt angle of the slider increases. ▶ The contact interference increases, the normal force and shear force increase together. ▶ Short SAM molecules are more sensitive to a compressive loading and react to a larger normal force.The nanotribology mechanism of alkanethiol self-assembled monolayers (SAM) chemisorbed on a gold surface under a non-flat contact by a tilt plane was studied using molecular dynamics (MD) simulations. The molecular trajectories, tilt angles, normal forces, shear forces, and frictional coefficient of the SAM were evaluated during the friction and relaxation processes for various parameters, including the tilt angle of the slider, interference magnitude, and SAM length. At the nanoscale, the magnitude of interface interactional forces is strongly dependent on the magnitude of the contact area, not on the surface geometry. The contact area and the exerted normal force of the SAM increase with decreasing the tilt angle of the slider at the same contact interference. In contrast, the periods in both normal force and shear force are gradually delayed as the tilt angle of the slider increases. Once the contact interference increases, the normal force and shear force increase together. During the sliding friction process with a smaller tilt slider angle, SAM molecules can maintain a better collective ordered structure. Short SAM molecules are more sensitive to a compressive loading and react to a larger normal force under the same contact interference due to the deformation of a larger tilt angle and decrease in chain length. The friction coefficient of SAM is significantly more dependent on the tilt angle of the slider than the contact interference.

Keywords: SAM; Nanotribology; Sliding friction; Tilt angle; Normal force; Shear force

Structure and photoluminescence of VAC-functionalized ZnO nanoparticles by plasma polymerization by Huihui Yang; Rongjin Huang; Hao Zhang; Laifeng Li; Xiangdong Xu; Lihe Qian (pp. 4129-4132).

▶ VAC-functionalized ZnO nanoparticles have been created by plasma polymerization. ▶ VAC polymer layer is uniformly deposited on the surfaces of the ZnO nanoparticles. ▶ The PL intensity of the ZnO nanoparticles is decreased due to the deposited films. ▶ Plasma films indicate better UV shielding ability for the smaller particles.A plasma polymerization method was used to modify the surfaces of ZnO nanoparticles, and the effects of plasma surface modification on photoluminescence (PL) property of ZnO nanoparticles were studied. High-resolution transmission electron microscopy images revealed that a thin film of vinyl acetate (VAC) polymer layer (∼4nm) was uniformly deposited on the surfaces of the ZnO nanoparticles. The chemical structure of the polymer layer was identified by Fourier transform infrared (FTIR) experiments. The photoluminescence (PL) intensity of the ZnO nanoparticles was found to be significantly decreased by the deposited plasma films. For the particle of smaller size, the ultrathin film indicated better ultraviolet (UV) shielding ability.

Keywords: Plasma polymerization; Nano-ZnO particles; Surface modification; Photoluminescence

Preparation and biocompatibility of electrospun poly(l-lactide-co-ɛ-caprolactone)/fibrinogen blended nanofibrous scaffolds by Zhengdong Fang; Weiguo Fu; Zhihui Dong; Xiangman Zhang; Bin Gao; Daqiao Guo; Hongbing He; Yuqi Wang (pp. 4133-4138).

▶ Composite scaffolds were fabricated by electrospinning blended solutions of PLCL and fibrinogen. ▶ Properties of the scaffolds were strongly influenced by the concentration of fibrinogen. ▶ The electrospun PLCL/fibrinogen scaffolds provided good support for cell growth. ▶ The composite scaffolds have great potential for tissue engineering applications in the future.Electrospun blended nanofibrous scaffolds were fabricated from an synthetic biodegradable polymer (poly(l-lactide-co-ɛ-caprolactone): PLCL; 8% solution) and a natural protein (fibrinogen; 100mg/ml solution) with different volume ratios. Results showed that the blended scaffolds consisted of nanoscale fibers with mean diameters ranging from 224 to 450nm. The deposition of the fibrinogen amino groups on the surfaces of the blended scaffolds was confirmed by XPS. The hydrophilicity of the blended scaffolds were improved with the fibrinogen content increasing in the blended system. Cell viability assay and SEM results showed that human umbilical vein endothelial cells (HUVECs) had progressive growth and well spread morphology on the blended scaffolds. This study demonstrated that electrospun PLCL/fibrinogen blended scaffolds have potential application in tissue engineering.

Keywords: Electrospinning; Tissue engineering; Nanofibrous scaffold; Natural polymer; Synthetic polymer

Fabrication of open-ended TiO₂ nanotube arrays by anodizing a thermally evaporated Ti/Au bilayer film by Zhi-Kun Zhang; Deng-Zhu Guo; Ying-Jie Xing; Geng-Min Zhang (pp. 4139-4143).

▶ Thermally evaporated Ti/Au bilayer film. ▶ Well-aligned TiO₂ nanotube arrays by anodizing Ti film. ▶ Open-ended structure with a large area ratio. ▶ A specific non-aqueous organic based electrolyte.Fabrication of TiO₂ nanotube arrays (TNAs) with through-hole morphology is practical significance to enhance the photocatalytic activity of TNAs, as well as expanding their applications. In present work, open-ended TNAs are synthesized on a conductive Au layer by anodizing a thermally evaporated Ti/Au bilayer film. In the anodizing process, the upper Ti layer is transformed into well-aligned TNAs. The barrier layer under the growing TNAs ultimately touches the Au layer and is completely dissolved by the electrochemical etching. In order to avoid the bubble disruption of TNAs caused by the water electrolysis after the Au layer is exposed to the electrolyte, a specific non-aqueous electrolyte is used. The XRD results reveal that the as-formed open-ended TNAs are amorphous and can be transformed into anatase by annealing at 350°C.

Keywords: TiO; ₂; Nanotube; Film; Anodization

Evolution of micro-arc oxidation behaviors of the hot-dipping aluminum coatings on Q235 steel substrate by Lu Lihong; Shen Dejiu; Zhang Jingwu; Song Jian; Li Liang (pp. 4144-4150).

▶ Evolution of micro-arc oxidation behaviors was systematically and roundly studied. ▶ The ingrown and outgrown thicknesses of the ceramic coatings were studied. ▶ The ratio of ingrown/outgrown thicknesses was investigated. ▶ Main phenomenon during the PEO process was analyzed referring to Dittrich model.Micro-arc oxidation (MAO) is not applicable to prepare ceramic coatings on the surface of steel directly. In this work, hybrid method of MAO and hot-dipping aluminum (HDA) were employed to fabricate composite ceramic coatings on the surface of Q235 steel. The evolution of MAO coatings, such as growth rate, thickness of the total coatings, ingrown and outgrown coatings, cross section and surface morphologies and phase composition of the ceramic coatings were studied. The results indicate that both the current density and the processing time can affect the total thickness, the growth rate and the ratio of ingrown and outgrown thickness of the ceramic coatings. The total thickness, outgrown thickness and growth rate have maximum values with the processing time prolonged. The time when the maximum value appears decreases and the ingrown dominant turns to outgrown dominant little by little with the current density increasing. The composite coatings obtained by this hybrid method consists of three layers from inside to outside, i.e. Fe–Al alloy layer next to the substrate, aluminum layer between the Fe–Al layer and the ceramic coatings which is as the top exterior layer. Metallurgical bonding was observed between every of the two layers. There are many micro-pores and micro-cracks, which act as discharge channels and result of quick and non-uniform cooling of melted sections in the MAO coatings. The phase composition of the ceramic coatings is mainly composed of amorphous phase and crystal Al₂O₃ oxides. The crystal Al₂O₃ phase includes κ-Al₂O₃, θ-Al₂O₃ and β-Al₂O₃. Compared with the others, the β-Al₂O₃ content is the least. The MAO process can be divided into three periods, namely the common anodic oxidation stage, the stable MAO stage and the ceramic coatings destroyed stage. The exterior loose part of the ceramic coatings was destroyed badly in the last period which should be avoided during the MAO process.

Keywords: Evolution; Q235 steel; Hot-dipping aluminum; Micro-arc oxidation; Ceramic coatings

Deactivation of photocatalytically active ZnO nanoparticle and enhancement of its compatibility with organic compounds by surface-capping with organically modified silica by Zhi Cao; Zhijun Zhang (pp. 4151-4158).

▶ TEOS and DEDMS were used as the co-precursors of the sol–gel process for preparing ormosil. ZnO nanoparticles were surface-capped by the as-prepared ormosil. The surface properties of the ZnO nanoparticles can be tuned easily and precisely. The ormosil-capped ZnO nanoparticles showed strong hydrophobicity and compatibility with organic phase. And their photocatalytic activity significantly reduced while their UV-shielding ability almost unchanged.Tetraethyl orthosilicate (TEOS) and dimethyldiethoxysilane (DEDMS) were used as co-precursors to prepare organically modified silica (ormosil) via sol–gel process. The resultant ormosil was adopted for surface-capping of ZnO nanoparticle, where methyl (organic functional group) and silica (inorganic component) were simultaneously introduced onto the surface of the nanoparticles for realizing dual surface-modification. The ormosil-capped ZnO nanoparticle showed strong hydrophobicity and good compatibility with organic phases, as well as effectively decreased photocatalytic activity and almost unchanged ultraviolet (UV)-shielding ability. More importantly, the comprehensive properties of ormosil-capped ZnO nanoparticle could be manipulated by adjusting the molar ratio of TEOS to DEDMS during sol–gel process. This should help to open a wider window to better utilizing the unique and highly attractive properties such as high UV-shielding ability and high-visible light transparency of ZnO nanoparticle in sunscreen cosmetics.

Keywords: ZnO nanoparticles; Organically modified silica; Surface-capping; Hydrophobicity; Photocatalytic activity; UV-shielding ability

Effect of Al mole fraction on structural and electrical properties of Al_xGa1−_xN/GaN heterostructures grown by plasma-assisted molecular beam epitaxy by A. SH. Hussein; Z. Hassan; S.M. Thahab; S.S. Ng; H. Abu Hassan; C.W. Chin (pp. 4159-4164).

▶ The successful growth of Al_xGa1−_xN thin films on Si (111) substrate with various Al mole fractions has been obtained. ▶ Structural and morphology studies indicate that relatively larger tensile strain exits in the sample with the smallest Al mole fraction. ▶ A smaller compressive strain and larger grain size appears with Al mole fraction=0.3. ▶ Strain is relaxed with the highest Al mole fraction sample. ▶ Linear relationship between the barrier height and Al mole fraction has been obtained.The effect of Al mole fractions on the structural and electrical properties of Al_xGa1−_xN/GaN thin films grown by plasma-assisted molecular beam epitaxy (PA-MBE) on Si (111) substrates has been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and current–voltage ( I– V) measurements. X-ray results revealed that the AlGaN/GaN/AlN was epitaxially grown on Si substrate. By applying Vegard's law, the Al mole fractions of Al_xGa1−_xN samples were found to be 0.11, 0.24, 0.30 and 0.43, respectively. The structural and morphology results indicated that there is a relatively larger tensile strain for the sample with the smallest Al mole fraction; while a smaller compressive strain and larger grain size appear with Al mole fraction equal to 0.30. The strain gets relaxed with the highest Al mole fraction sample. Finally, the linear relationship between the barrier height and Al mole fraction was obtained.

Keywords: PA-MBE; XRD; AlGaN; SEM

Surface treatment of aramid fiber by air dielectric barrier discharge plasma at atmospheric pressure by Caixia Jia; Ping Chen; Wei Liu; Bin Li; Qian Wang (pp. 4165-4170).

▶ The atmospheric air DBD plasma treatment time had great influence on aramid surface. ▶ The plasma treatment increased the fiber surface wettability. ▶ After treatment a kind of resin, PPESK showed better wetting behavior on the fiber. ▶ An optimum plasma treatment condition existed for the aramid surface modification.Aramid fiber samples are treated by air dielectric barrier discharge (DBD) plasma at atmospheric pressure; the plasma treatment time is investigated as the major parameter. The effects of this treatment on the fiber surface physical and chemical properties are studied by using surface characterization techniques. Scanning electron microscopy (SEM) is performed to determine the surface morphology changes, X-ray photoelectron spectroscopy (XPS) is analyzed to reveal the surface chemical composition variations and dynamic contact angle analysis (DCAA) is used to examine the changes of the fiber surface wettability. In addition, the wetting behavior of a kind of thermoplastic resin, poly(phthalazinone ether sulfone ketone) (PPESK), on aramid fiber surface is also observed by SEM photos. The study shows that there seems to be an optimum treatment condition for surface modification of aramid fiber by the air DBD plasma. In this paper, after the 12s, 27.6W/cm³ plasma treatment the aramid fiber surface roughness is significantly improved, some new oxygen-containing groups such as C–O, CO and OC–O are generated on the fiber surface and the fiber surface wettability is greatly enhanced, which results in the better wetting behavior of PPESK resin on the plasma-treated aramid fiber.

Keywords: Aramid fiber; Air DBD plasma; Treatment time; Surface characterization; Wetting behavior

The crystalline orientation and ferroelectric properties of Bi_3.25La_0.75Ti₃O₁₂ thin films mediated by the intermediate layer of LaNiO₃ by J.B. Wang; P.J. Li; X.L. Zhong (pp. 4171-4174).

▶ The crystalline orientation of Bi_3.25La_0.75Ti₃O₁₂ (BLT) thin films are successfully controlled by the intermediate layer of LaNiO₃ (LNO) with chemical solution deposition (CSD). ▶ The anisotropic polarization of BLT thin films is studied, which shows that the vector of the main spontaneous polarization in these layered perovskite materials (BLT) is along a axis. ▶ The crystalline orientation LNO thin film is directly controlled by two different thermal treating processes with chemical solution deposition. c-Axis-oriented and (117)-oriented Bi_3.25La_0.75Ti₃O₁₂ (BLT) thin films are successfully controlled by the intermediate layer of LaNiO₃ (LNO) with chemical solution deposition (CSD), respectively. X-ray diffraction (XRD) demonstrates that the structure and orientation of LNO thin films have a strong effect on the orientation of BLT thin films. Scanning electron microscopy suggests that BLT thin films on LNO electrode exhibit crack-free, uniform size grains and dense microstructure. A crystalline orientation dependent remanent polarization is observed in BLT thin films, and it is found that the remanent polarization (2 P_r) of (117)-oriented films is larger than that of c-axis-oriented films. Our research directly demonstrates that the vector of the main spontaneous polarization in these layered perovskite materials (BLT) is along a-axis.

Keywords: BLT; Ferroelectric; CSD; Orientation

Shape and size transformation of gold nanorods (GNRs) via oxidation process: A reverse growth mechanism by Govindasamy Chandrasekar; Karine Mougin; Hamidou Haidara; Loïc Vidal; Enrico Gnecco (pp. 4175-4179).

▶ Bromide ion catalyses the oxidative anisotropic transformation of as-synthesised gold nanorods (GNRs) to spherical shape in the presence of hydrogen peroxide via Au(III)–CTAB complexation. ▶ UV–vis spectroscopic analysis showed the blue shifting of longitudinal Plasmon due to shortening of GNRs. ▶ Transmission electron microscopy (TEM) images further confirmed the sequential shortening of GNRs. ▶ This anisotropic behaviour provides, the information to the GNRs growth mechanism, as both growth and shortening occurs preferentially at the edge of single-crystalline GNRs in the presence of Br⁻ ions.The anisotropic shape transformation of gold nanorods (GNRs) with H₂O₂ was observed in the presence of “cethyl trimethylammonium bromide” (CTAB). The adequate oxidative dissolution of GNR is provided by the following autocatalytic scheme with H₂O₂: Au⁰→Au⁺, Au⁰+Au n⁺→2Au³⁺, n=1 and 3. The shape transformation of the GNRs was investigated by UV–vis spectroscopy and transmission electron microscopy (TEM). As-synthesised GNRs exhibit transverse plasmon band (TPB) at 523nm and longitudinal plasmon band (LPB) at 731nm. Upon H₂O₂ oxidation, the LPB showed a systematic hypsochromic (blue) shift, while TPB stays at ca. 523nm. In addition, a new emerging peak observed at ca. 390nm due to Au(III)–CTAB complex formation during the oxidation. TEM analysis of as-synthesised GNRs with H₂O₂ confirmed the shape transformation to spherical particles with 10nm size in 2h, whereas centrifuged nanorod solution showed no changes in the aspect ratio under the same condition. Au³⁺ ions produced from oxidation, complex with excess free CTAB and approach the nanorods preferentially at the end, leading to spatially directed oxidation. This work provides some information to the crystal stability and the growth mechanism of GNRs, as both growth and shortening reactions occur preferentially at the edge of single-crystalline GNRs, all directed by Br⁻ ions.

Keywords: Gold; Nanorods; Plasmon; Oxidation; Dissolution; H; ₂; O; ₂

Synthesis of magnetocoated tetrapod ZnO-whiskers by polymer precursor derived method by Xin Xing; Gongyi Li; Lin Liu; Xiaodong Li; Zengyong Chu; Haifeng Cheng (pp. 4180-4184).

▶ Magnetocoated tetrapod ZnO-whiskers can be synthesized by precursor derived method. ▶ The precursor polymer can be prepared from FeCl₃ modified polymethylsilane. ▶ The precursor can be pyrolyzed and coated on the surface of whiskers at above 800°C. ▶ Magnetocoated tetrapod ZnO-whiskers show magnetic loss from a μ″ between 0.1 and 0.3.Magnetic coatings were synthesized in situ on the surface of tetrapod ZnO-whiskers (ZnOws) via a Fe-containing polymer precursor derived method. Raw ZnOws were dispersed in polymer solution prepared from FeCl₃ modified polymethylsilane. Then the dispersion was solidified and cured. When the curing temperature was high enough, the polymer to inorganic conversion occurred, and ZnOws with magnetic coatings were obtained. Results of scanning electron microscopy, energy diffraction of X-ray spectroscopy, and X-ray diffraction proved that magnetic ZnOw maintains a tetrapod morphology and Fe has been introduced on the surface of ZnOw. The appropriate pyrolysis temperature is above 800°C. A study of the electromagnetic parameters of the composite powder proved that μ″ is between 0.1 and 0.3. The material has radar-absorbing properties. At a thickness of 2.6mm, the calculated maximum reflection loss for the absorber is about −9.2dB at 2–8GHz.

Keywords: Tetrapod ZnO-whisker; Modified polymethylsilane; Magnetic coatings; Polymer precursor derived; Surface treatments; Radar-absorbing materials

On the dissolution/reaction of small-grain Bioglass^® 45S5 and F-modified bioactive glasses in artificial saliva (AS) by Valentina Aina; Luca Bertinetti; Giuseppina Cerrato; Marta Cerruti; Gigliola Lusvardi; Gianluca Malavasi; Claudio Morterra; Linda Tacconi; Ledi Menabue (pp. 4185-4195).

▶ The reactivity in AS of F-containing bioactive glasses was fully investigated. ▶ The formation, in AS, of crystalline CaCO₃ is peculiar of F-modified glasses. ▶ The formation in AS of a CaP phase on F-containing glass surface is reduced. ▶ The pH increase is higher for HCaCaF₂ than for HNaCaF₂ glass.The reaction of small-grain Bioglass^® 45S5 in artificial saliva (AS), to produce a layer of hydroxy-apatite (HA) and/or hydroxy-carbonate apatite (HCA), has been studied and compared to the results obtained in a simple buffered solution (TRIS). Some potentially bioactive glasses based on the composition of Bioglass^® and containing CaF₂ (HCaCaF₂ 5% and HNaCaF₂ 5%) have also been studied, in order to analyze the effects/changes produced when a F-containing glass surface is contacted with AS. The insertion of fluorine has been proposed to improve bioactive glass bone-bonding ability, and to parallel fluorine-containing glass-ceramics currently used in dentistry. ICP-OES analysis of the solution, and FTIR spectroscopy of the solid samples provided compositional information on the stages of reaction. These data were integrated with XRD and the textural and morphological data, obtained by specific surface areas determination and TEM-EDS measurements. In the case of Bioglass^® 45S5, a comparison at corresponding reaction times indicates that the precipitation of an amorphous Ca-phosphate phase is faster in AS, but the crystallization of HA/HCA is delayed in AS with respect to the TRIS solution. For fluoride-containing glasses, the sample HCaCaF₂ 5%, in which CaF₂ replaces part of CaO, possesses the fastest rate for HA/HCA crystallization (1 week) in AS. Some lines of interpretation for these results are proposed.

Keywords: F-containing bioactive glasses; Protein adsorption; Dissolution/reaction study; Surface characterization

Weathering performance of the polyurethane nanocomposite coatings containing silane treated TiO₂ nanoparticles by S.M. Mirabedini; M. Sabzi; J. Zohuriaan-Mehr; M. Atai; M. Behzadnasab (pp. 4196-4203).

▶ This work explains an efficient approach to improve weathering performance of an polyurethane based coating with employing silane coupling agent treated TiO₂ nanoparticles. ▶ Weathering performance of PU nanocomposites coatings was investigated utilizing colour coordinates data collection, tensile strength measurements and surface morphology evaluation. ▶ TEM and AFM observations revealed that the APS treated nanoparticles have a better dispersion and smaller agglomeration, compared with their untreated counterparts. ▶ The results revealed that addition of 0.5–1.0wt.% APS treated TiO₂ nanoparticles reduces photocatalytic activity, and improves the weathering performance PU nanocomposite coatings. ▶ Results also revealed that the colour measurement is a useful technique and non destructive method for evaluation of coating's performance against weathering conditions.Nano-filled polyurethane coatings were prepared by incorporation of various amounts of untreated and amino propyltrimethoxy silane (APS) treated TiO₂ nanoparticles. TEM and AFM techniques were employed to evaluate dispersion of nanoparticles and surface morphology of the coating, respectively. TEM observations revealed that the APS treated nanoparticles have a better dispersion and smaller agglomeration, compared with their untreated counterparts. AFM images revealed that, surface roughness of the coatings increased with increasing of nanoparticles content, however, at equal level of loadings; coatings containing untreated nanoparticles showed a higher surface roughness.Colour changes (colour coordinates data measurements), mechanical properties and surface morphology of the PU nanocomposite coatings, before and after being exposed to a QUV chamber for 1000h were studied using various techniques. The results revealed that addition of 0.5 to 1.0wt.% APS treated TiO₂ nanoparticles reduces photocatalytic activity, and improves the weathering performance PU nanocomposite coatings. Tensile strength measurements showed significant improvement of mechanical properties of PU coatings containing modified TiO₂ nanoparticles. Results also revealed that the colour measurement is a useful technique and non destructive method for evaluation of coating's performance against weathering conditions. The experimental results showed a good correlation between different techniques findings.

Keywords: TiO; ₂; nanoparticles; Photo-catalyst; Dispersion; Weathering; Morphology; Mechanical properties

The effect of iridium precursor on oxide-supported iridium catalysts prepared by atomic layer deposition by H. Vuori; A. Pasanen; M. Lindblad; M. Valden; M. Veringa Niemelä; A.O.I. Krause (pp. 4204-4210).

▶ New iridium precursor for atomic layer deposition was tested. ▶ Effect of precursor on catalyst surface species, chemical state and characteristics. ▶ New precursor allows Ir deposition at lower T compared to conventional precursor.Alumina, silica and beta zeolite supported iridium catalysts were prepared by atomic layer deposition (ALD) from two different metal precursors, Ir(acac)₃ and Ir(thd)(COD). The use of Ir(thd)(COD) in ALD is reported for the first time. The aim was to investigate the effect of the precursor on catalyst surface species, chemical state and characteristics.Controllable ALD reaction was successful with both iridium precursors on alumina and with Ir(acac)₃ on β zeolite. On these catalysts, iridium particle sizes were very small (1–3nm). Instead, some thermal decomposition of both precursors was observed during deposition on silica. At conditions, where no or very little decomposition of the precursors took place, the differences in the chemical state and characteristics of the as-prepared Ir/support samples were negligible, In ALD, Ir(acac)₃ is slightly more stable at high deposition temperatures (>200°C) while Ir(thd)(COD) enables the utilization of larger temperature range since it vaporizes at lower temperature compared to Ir(acac)₃. The results thus indicate that Ir(thd)(COD) is a suitable new precursor for ALD.

Keywords: Iridium catalysts; ALD; Metal precursor; Catalyst characterization

Investigations of the hydrophobic and scratch resistance behavior of polystyrene films deposited on bell metal using RF-PACVD process by A.J. Choudhury; S.A. Barve; Joyanti Chutia; A.R. Pal; D. Chowdhury; R. Kishore; Jagannath; N. Mithal; M. Pandey; D.S. Patil (pp. 4211-4218).

▶ RF-PACVD technique is utilized to deposit polystyrene films on bell metal. ▶ The cross-linked chemical structure of the polystyrene film increases with RF power. ▶ Peroxy polystyryl radicals in the film lose more oxygen with increasing RF power. ▶ RF power effects hydrophobic and scratch resistance behavior of polystyrene films. ▶ Higher RF power deteriorates the observed films characterization results.Polystyrene films are deposited on bell metal substrates using radiofrequency plasma assisted chemical vapor deposition (RF-PACVD) process. The deposition of polystyrene film is carried out at working pressure of 1.6×10⁻¹mbar and in the RF power range of 20–110W. The hydrophobic and mechanical behaviors of the polystyrene films are studied as a function of RF power. The chemical compositions and surface chemistry of the polystyrene films are investigated using Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). It is revealed that enhanced cross-linked chemical structure and higher loss of oxygen by peroxy polystyryl radical with increasing RF power results in the formation of polystyrene films with more hydrophobic and scratch resistance behavior. However, extensive destruction of cross-linked chemical structure due to high energetic ion bombardment tends to decrease the hydrophobic and scratch resistance behavior of the polystyrene film deposited at RF power of 110W. Atomic force microscopy (AFM) images show quite uniform and crack free surfaces of the polystyrene films having rms roughness in the range of 0.35–0.87nm. Attempts are made to correlate the characterization results with the parameters that are used for thin film depositions.

Keywords: RF-PACVD; Polystyrene thin film; XPS; Hydrophobic; Scratch resistance

Quantification of MgO surface excess on the SnO₂ nanoparticles and relationship with nanostability and growth by Douglas Gouvêa; Gilberto J. Pereira; Léon Gengembre; Marlu C. Steil; Pascal Roussel; Annick Rubbens; Pilar Hidalgo; Ricardo H.R. Castro (pp. 4219-4226).

▶ Surface excess in MgO doped SnO₂ nanoparticles plays an important role in the system's energetics and size stability. ▶ The amount of Mg ions on the surface was directly related to the nanoparticles total free energy, in a sense that the dopant will always spontaneously distribute itself to minimize it if enough diffusion is provided. ▶ The effect of MgO on the surface was particularly important and has a direct effect on the equilibrium particle size (nanoparticle stability).In this work, we experimentally showed that the spontaneous segregation of MgO as surface excess in MgO doped SnO₂ nanoparticles plays an important role in the system's energetics and stability. Using X-ray fluorescence in specially treated samples, we quantitatively determined the fraction of MgO forming surface excess when doping SnO₂ with several different concentrations and established a relationship between this amount and the surface energy of the nanoparticles using the Gibbs approach. We concluded that the amount of Mg ions on the surface was directly related to the nanoparticles total free energy, in a sense that the dopant will always spontaneously distribute itself to minimize it if enough diffusion is provided. Because we were dealing with nanosized particles, the effect of MgO on the surface was particularly important and has a direct effect on the equilibrium particle size (nanoparticle stability), such that the lower the surface energy is, the smaller the particle sizes are, evidencing and quantifying the thermodynamic basis of using additives to control SnO₂ nanoparticles stability.

Keywords: SnO; ₂; Nanoparticles; Stability; MgO; Dopant

Structural study of sol–gel Au/TiO₂ films from nanopowders by Dorel Crişan; Nicolae Drăgan; Mălina Răileanu; Maria Crişan; Adelina Ianculescu; Dumitru Luca; Andrei Năstuţă; Diana Mardare (pp. 4227-4231).

Display Omitted▶ Au-doped TiO₂ sol-gel films from nanopowders were performed. ▶ The presence of the dopant in the TiO₂ lattice induces greater internal strains. ▶ The best hydrophilic performance is attributed to the Au-doped samples at 400°C.TiO₂ represents one of the most important sol–gel materials, due to its photocatalytic properties, in the case of both powders and coatings. Nanostructured titania has been reported to be used in many applications in different fields ranging from optics to gas sensor via solar energy. Recent researches point out the existence of new procedures used in order to enhance the efficiency of the photocatalytic process. The metal ion doping is such an example. Two types of 2wt.% Au containing TiO₂ powders have been embedded in sol–gel vitreous TiO₂ matrices. Au-doped TiO₂ films have been prepared from these sols, by dipping procedure using quartz microscopic slides, as substrates. The relationship between the synthesis conditions and the properties of titania nanosized materials, such as thermal stability, phase composition, crystallinity, and the influence of dopant was investigated. The hydrophilic properties of the films were correlated with their structure, composition and surface morphology.

Keywords: Sol–gel process; Au-doped TiO; ₂; Nanopowder; Film; Surface properties; Structural studies

A DFT study on the formation of CH₃O on Cu₂O(111) surface by CH₃OH decomposition in the absence or presence of oxygen by Zhang Riguang; Liu Hongyan; Ling Lixia; Li Zhong; Wang Baojun (pp. 4232-4238).

▶ Oxygen-precovered exhibits strong catalytic activity for the CH₃O formation. ▶ The oxygen of CH₃O formed comes from the O atom of CH₃OH. ▶ The C–O bond-breaking path for the CH₃O formation is inhibited by dynamics.The formation mechanism of CH₃O by the adsorption and decomposition of CH₃OH on clean and oxygen-precovered Cu₂O(111) surface has been investigated with density functional theory method together with the periodic slab models. Two possible formation pathways of CH₃O by CH₃OH decomposition on oxygen-precovered (O_pre) Cu₂O(111) surface were proposed and discussed. One is the O–H bond-cleavage of CH₃OH with H migration to O_pre to form CH₃O; the other is the C–O bond-scission of CH₃OH with CH₃ migration to O_pre leading to CH₃O_pre. The calculated results show that the O–H bond-breaking path has the lowest activation barrier 26.8kJmol⁻¹, the presence of oxygen-precovered on Cu₂O(111) surface exhibits a high surface reactivity toward the formation of CH₃O by the O–H bond-cleavage of CH₃OH, and reduce the activation barrier of O–H bond-cleavage. The C–O bond-breaking path was inhibited by dynamics, suggesting that the O atom of CH₃O is not from the oxygen-precovered, but comes from the O of CH₃OH. Meanwhile, the calculated results give a clear illustration about the formation mechanism of CH₃O in the presence of oxygen and the role of oxygen at the microscopic level.

Keywords: Cu; ₂; O(1; 1; 1); Oxygen-precovered; Methanol; Methoxyl; Density functional theory

Co removal and phase transformations during high power diode laser irradiation of cemented carbide by M. Barletta; G. Rubino; A. Gisario (pp. 4239-4245).

▶ Use of a continuous wave-high power diode laser to remove surface Co-binder from Co-cemented tungsten carbide. ▶ Study of phase transformations and micro-structural modifications of the WC–Co substrates by varying the energy density during laser processing. ▶ Increasing the energy density, the micro-structure of the WC–Co is progressively transformed, with the removal of Co and the formation of larger grains. ▶ At very high energy density, local melting of the WC grains with the formation of big agglomerates of interlaced grains is observed. ▶ Crystalline structure of the irradiated substrate shows the presence of a brittle ternary eutectic phase of W, Co and C, detrimental to the mechanical properties of WC–Co.The use of a continuous wave-high power diode laser for removing surface Co-binder from Co-cemented tungsten carbide (WC–Co (5.8wt%.)) hardmetal slabs was investigated. Combined scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction analyses were performed in order to study the phase transformations and micro-structural modifications of the WC–Co substrates occurring during and after laser irradiation. The micro-structure of the WC–Co progressively transforms as energy density increased, exhibiting stronger removal of Co and WC grain growth. At very high energy density, local melting of the WC grains with the formation of big agglomerates of interlaced grains is observed, and the crystalline structure of the irradiated substrate shows the presence of a brittle ternary eutectic phase of W, Co and C (often referred to as the η-phase). The latter can be detrimental to the mechanical properties of WC–Co. Therefore, the proper adjustment of the laser processing parameters plays a crucial role in surface treatments of WC–Co substrates prior to post-processing like diamond deposition.

Keywords: Diode laser; Surface treatments; Hardmetal; Cobalt

Mechanical characteristics of Fe-based coating obtained by nanoindentation by Li Hua-Yi; Li Guo-Lu; Wang Hai-Dou; Xu Bin-Shi (pp. 4246-4249).

▶ AFM combined with O&P method was put forward to investigate materials of pile-up. ▶ Properties obtained by G&S and new proposed methods showed the same distribution. ▶ Both hardness and elastic modulus showed certain surface roughness dependence. ▶ Elastic modulus obtained by AFM combined with O&P method was insensitive to RMS.In this study, clad layers of iron-based alloy with a nature of self-fluxing were melted on low carbon steel by plasma cladding process. Nanoindentation with atomic force microscopy (AFM) has been used to investigate the mechanical properties of the coating. Hardness and elastic modulus at ultra-low loads were first determined using the method proposed by Giannakopoulos and Suresh (G&S method). The true contact area and mechanical properties were then determined using atomic force microscopy (AFM) combined with the Oliver and Pharr method (new proposed method) as the correction group. The mechanical properties calculated by the two methods showed the same distribution while had deviation in specific values. The effect of surface roughness to the calculated mechanical properties was investigated. Both hardness and elastic modulus were found to exhibit certain surface roughness dependence. When root mean square (RMS) roughness ranged from 2.2nm to 4.4nm, hardness calculated by both the methods increased obviously and reached maximums around 4.1nm. Elastic modulus calculated by G&S method at different RMS showed the same distribution with that of hardness, while reduced elastic modulus obtained by AFM was insensitive to the range of RMS.

Keywords: Plasma cladding; Nanoindentation; Hardness; Elastic modulus; AFM; RMS

Facile route for preparation of silver nanoparticle-coated precipitated silica by Dang Viet Quang; Pradip B. Sarawade; Askwar Hilonga; Sung Dae Park; Jong-Kil Kim; Hee Taik Kim (pp. 4250-4256).

▶ Silver nanoparticle-coated precipitated silica was prepared by using sodium silicate. ▶ Precipitated silica (PS) was synthesized and functionalized through one step process. ▶ Silver nanoparticles were found mostly coated on the exterior layer of PS.In this research, a facile route was used to prepare silver nanoparticle-coated precipitated silica using sodium silicate, a cheap precursor. Precipitated silica (PS) was synthesized by dropping 8% H₂SO₄ into a mixed solution of sodium silicate 24% (Na₂O·3.4SiO₂) and NaCl 4%; under constant stirring. The precipitated silica was then modified by simultaneous addition of 3-aminopropyltriethoxysilane (3-APTES) and 8% H₂SO₄. The resulting material was aged at 80°C for 1h to produce amino-functionalized precipitated silica (AFPS). Silver nanoparticle-coated precipitated silica (Ag–NPS) was synthesized by adding silver nitrate (AgNO₃). The synthesis procedure also involved mixing for 2h and dropping 0.05M sodium borohydride (NaBH₄). The final products, namely, PS, AFPS, and Ag–NPS were characterized using BET analyzer, FE-SEM, TEM and XRD. Silver nanoparticles with an average size ranging from 18 to 25nm were found mostly coated on the exterior layer of the precipitated silica. The synthesis method reported in this work is facile and might be used for large-scale industrial production of inexpensive Ag–NPS.

Keywords: Precipitated silica; Porous silica; Silver nanoparticles; Sodium silicate

Oxidation of TiNi surface with hyperthermal oxygen molecular beams by Michio Okada; Makoto Souwa; Toshio Kasai; Yuden Teraoka (pp. 4257-4263).

▶ We report results of our detailed studies on the initial oxidation process of TiNi. ▶ We elucidated the oxidation processes using high-resolution XPS measurements. ▶ We succeeded in fabricating thick Ni-free TiO₂ layer on TiNi using molecular beams.We report results of our detailed studies on the initial oxidation process of TiNi with a 2eV hyperthermal oxygen molecular beam (HOMB) and thermal O₂ in the backfilling. The oxidation processes are monitored by X-ray photoemission spectroscopy (XPS) measurements in conjunction with synchrotron radiation (SR). In the early stage of oxidation, the precursor mediated dissociative adsorption is the dominant reaction mechanism. In the oxide formation process at higher O coverage, HOMB has the advantage in the dissociation process of O₂ molecule and can grow TiO₂ layers with the underlying TiO_x-rich and/or Ni-rich layers. We succeeded in fabricating thick Ni-free TiO₂ layer, possibly blue colored rutile TiO₂, combining HOMB and surface annealing.

Keywords: TiNi alloy; Hyperthermal molecular beam; Oxidation

Assessment of barium sulphate formation and inhibition at surfaces with synchrotron X-ray diffraction (SXRD) by Eleftheria Mavredaki; Anne Neville; Ken Sorbie (pp. 4264-4271).

▶ The main crystal faces of barium sulphate were identified from the in situ SXRD patterns in the absence and in the presence of inhibitors. The lattice planes of BaSO₄ reveal the same growth trend on the surface independently of the supersaturation index and the temperature. ▶ At 95°C 10ppm PPCA inhibits the growth of the dominant barite surfaces by 80%. ▶ At 95°C DETPMP performs as a nucleation inhibitor for barium sulphate formed on the surface. ▶ An effective inhibition of barite occurs when the (011) and (111) crystal faces of BaSO₄ are retarded. ▶ Strontium co-precipitates within the barite lattice resulting in formation of celestine barian. The growth of the celestine barian lattice planes follows the same growth trend with the one of the barite crystal faces.The precipitation of barium sulphate from aqueous supersaturated solutions is a well-known problem in the oil industry often referred to as ‘scaling’. The formation and growth of barite on surfaces during the oil extraction process can result in malfunctions within the oil facilities and serious damage to the equipment. The formation of barium sulphate at surfaces remains an important topic of research with the focus being on understanding the mechanisms of formation and means of control. In situ synchrotron X-ray diffraction (SXRD) was used to investigate the formation of barium sulphate on a stainless steel surface. The effect of Poly-phosphinocarboxylic acid (PPCA) and Diethylenetriamine–penta-methylenephosphonic acid (DETPMP) which are two commercial inhibitors for barium sulphate was examined. The in situ SXRD measurements allowed the identification of the crystal faces of the deposited barite in the absence and presence of the two inhibitors. The preferential effect of the inhibitors on some crystal planes is reported and the practical significance discussed.

Keywords: Barium sulphate; In situ; SXRD; Crystallography; Inhibitors

Effect of chemical etching on the Cu/Ni metallization of poly (ether ether ketone)/carbon fiber composites by LiZhi Di; Bin Liu; Jianjing Song; Dan Shan; De-An Yang (pp. 4272-4277).

Display Omitted▶ Cr₂O₃/H₂SO₄ chemical etching increased the surface concentration of CO bond and resulted in the partially exposure of carbon fibers. The surface roughness also increased. ▶ PEEK/Cf composites were metalized by copper electroless plating and then nickel electroplating. ▶ The high adhesive strength was mainly attributed to the bonding between carbon fiber and metal layer.Poly(ether ether ketone)/carbon fiber composites (PEEK/Cf) were chemical etched by Cr₂O₃/H₂SO₄ solution, electroless plated with copper and then electroplated with nickel. The effects of chemical etching time and temperature on the adhesive strength between PEEK/Cf and Cu/Ni layers were studied by thermal shock method. The electrical resistance of some samples was measured. X-ray photoelectron spectroscopy (XPS) was used to analyze the surface composition and functional groups. Scanning electron microscopy (SEM) was performed to observe the surface morphology of the composite, the chemical etched sample, the plated sample and the peeled metal layer. The results indicated that CO bond increased after chemical etching. With the increasing of etching temperature and time, more and more cracks and partially exposed carbon fibers appeared at the surface of PEEK/Cf composites, and the adhesive strength increased consequently. When the composites were etched at 60°C for 25min and at 70–80°C for more than 15min, the Cu/Ni metallization layer could withstand four thermal shock cycles without bubbling, and the electrical resistivity of the metal layer of these samples increased with the increasing of etching temperature and time.

Keywords: Poly(ether ether ketone); Composite; Chemical etching; Metallization

Preparation and characterization of Cu(In,Ga)(Se,S)₂ films without selenization by co-sputtering from Cu(In,Ga)Se₂ quaternary and In₂S₃ targets by Y.C. Lin; J.H. Ke; W.T. Yen; S.C. Liang; C.H. Wu; C.T. Chiang (pp. 4278-4284).

▶ We report a chalcopyrite CIGS films prepared by co-sputtering a quaternary alloy target and an In₂S₃ binary target with a one-stage annealing process without post-selenization. ▶ Experimental results showed that the stoichiometry ratios of the CIGSS film were Cu/(In+Ga)=0.92, Ga/(In+Ga)=0.26, and Se/(S)=0.49 that approached device-quality stoichiometry ratio (Cu/(In+Ga)<0.95, Ga/(In+Ga)<0.3, and (Se/S)≈0.5). ▶ The resistivity of the sample was 14.8Ωcm, with a carrier concentration of 3.4×10¹⁷cm⁻³ and mobility of 1.2cm²V⁻¹s⁻¹. ▶ The resulting film exhibited p-type conductivity with a double graded band-gap structure.In this study, Cu(In,Ga)(Se,S)₂ (CIGSS) thin films were deposited onto a bi-layer Mo coated soda-lime glass by co-sputtering a chalcopyrite Cu(In,Ga)Se₂ (CIGS) quaternary alloy target and an In₂S₃ binary target. A one-stage annealing process was performed to form CIGSS chalcopyrite phase without post-selenization. Experimental results show that CIGSS films were prepared by the proposed co-sputter process via CIGS (70W by radio frequency) and In₂S₃ (30W by direct current) with a substrate temperature of 373K, working pressure of 0.67Pa, and one-stage annealing at 798K for 30min. The stoichiometry ratios of the CIGSS film were Cu/(In+Ga)=0.92, Ga/(In+Ga)=0.26, and Se/(S)=0.49 that approached device-quality stoichiometry ratio (Cu/(In+Ga)<0.95, Ga/(In+Ga)<0.3, and (Se/S)≈0.5). The resistivity of the sample was 14.8Ωcm, with a carrier concentration of 3.4×10¹⁷cm⁻³ and mobility of 1.2cm²V⁻¹s⁻¹. The resulting film exhibited p-type conductivity with a double graded band-gap structure.

Keywords: Cu(In,Ga)(Se,S); ₂; Co-sputter process; One-stage annealing

Hydrodynamic size distribution of gold nanoparticles controlled by repetition rate during pulsed laser ablation in water by Ana Menéndez-Manjón; Stephan Barcikowski (pp. 4285-4290).

Display Omitted▶ Nanoparticle generation by fs-laser ablation in water at variable repetition rates. ▶ Constant ablation efficiency between 100 and 5000Hz. ▶ Polydispersity of the size distribution is reduced at higher repetition rates. ▶ Low repetition rates are more efficient for laser-induced fragmentation.Most investigations on the laser generation and fragmentation of nanoparticles focus on Feret particle size, although the hydrodynamic size of nanoparticles is of great importance, for example in biotechnology for diffusion in living cells, or in engineering, for a tuned rheology of suspensions. In this sense, the formation and fragmentation of gold colloidal nanoparticles using femtosecond laser ablation at variable pulse repetition rates (100–5000Hz) in deionized water were investigated through their plasmon resonance and hydrodynamic diameter, measured by Dynamic Light Scattering. The increment of the repetition rate does not influence the ablation efficiency, but produces a decrease of the hydrodynamic diameter and blue-shift of the plasmon resonance of the generated gold nanoparticles. Fragmentation, induced by inter-pulse irradiation of the colloids was measured online, showing to be more effective low repetition rates. The pulse repetition rate is shown to be an appropriate laser parameter for hydrodynamic size control of nanoparticles without further influence on the production efficiency.

Keywords: Fragmentation efficiency; Ablation efficiency; Polydispersity

X-ray photoelectron spectroscopy studies of Co-doped ZnO–Ga₂O₃–SiO₂ nano-glass–ceramic composites by Xiulan Duan; Chunfeng Song; Fapeng Yu; Duorong Yuan; Xiaoyu Li (pp. 4291-4295).

▶ Co-doped ZnO–Ga₂O₃–SiO₂ nano-glass–ceramic composites were prepared by sol–gel method. ▶ The Zn (2p_3/2), Ga (2p_3/2) and O (1s) XPS spectra for the material were deconvoluted into two peaks. ▶ The material is composed of an amorphous silicate network and ZnGa₂O₄ nanocrystalline particles. ▶ The amount of nanocrystals increases with the annealing temperature.Co-doped ZnO–Ga₂O₃–SiO₂ nano-glass–ceramic composites were prepared by sol–gel method. X-ray diffraction patterns showed that the crystallization temperature was 800°C. X-ray photoelectron spectroscopy (XPS) was used to study the effect of heat-treatment temperature on the electronic structure of Co-doped ZnO–Ga₂O₃–SiO₂ nano-glass–ceramic composites. The Zn (2p_3/2), Ga (2p_3/2) and O (1s) XPS spectra for the glass–ceramics heat-treated at 800–1000°C could be deconvoluted into two peaks corresponding to these elements in glass network and in nanocrystals, respectively. The results indicate that the material is composed of an amorphous silicate network and ZnGa₂O₄ nanocrystalline particles. The amount of nanocrystals increases with the annealing temperature. The photoelectron peak of Si (2p) shifts to higher binding energy at higher annealing temperature, revealing the charge transfer from Si to O increased. The relationship between the microstructure of Co-doped ZnO–Ga₂O₃–SiO₂ sample and its absorption properties was discussed, and the suitable heat-treatment temperature was proposed.

Keywords: Nano-glass–ceramics; Sol–gel process; X-ray photoelectron spectroscopy

Fabrication of two biomimetic superhydrophobic polymeric surfaces by Z.P. Fan; W.L. Liu; Z.J. Wei; J.S. Yao; X.L. Sun; M. Li; X.Q. Wang (pp. 4296-4301).

Display Omitted▶ Biomimetic superhydrophobic surfaces were obtained by phase separation method. ▶ The as-prepared films show excellent superhydrophobicity and self-cleaning property. ▶ The deduction of the CB relation matched well with the measured values.Two biomimetic superhydrophobic polymeric surfaces were obtained by a simple approach under ambient atmosphere. Water and ethanol were used as the nonsolvents in the method of phase separation in different systems. The influences of various factors in the process were investigated. Both of the as-prepared films showed excellent superhydrophobicity, depending on the high contact angle and the low contact angle hysteresis. Moreover, the classic and a new modified Cassie–Baxter relation were used on the polystyrene and poly-α-methyl styrene films to confirm the superhydrophobic performance.

Keywords: Superhydrophobic surface; Cassie–Baxter relation; Contact angle; Coral-like; Porous; Phase separation

Effect of crystalline structure of TiO₂ substrates on initial growth of atomic layer deposited Ru thin films by Seong Keun Kim; Sora Han; Jeong Hwan Han; Cheol Seong Hwang (pp. 4302-4305).

▶ Ru films were grown on polymorphic TiO₂ substrates by ALD. ▶ Anatase TiO₂ shows a shorter incubation cycle for Ru ALD. ▶ The difference in the incubation cycle affects the surface morphology of Ru films.Ru thin films were grown on polymorphic TiO₂ thin film substrates at 230 and 250°C by atomic layer deposition using 2,4-(dimethylpentadienyl)(ethylcyclopentadienyl)Ru and an O₂ gas. While the Ru films grown on amorphous and rutile TiO₂ substrates showed a relatively long incubation cycle number of approximately 350 and 100 at 230 and 250°C, respectively, the Ru films grown on anatase TiO₂ substrates exhibited a significantly shorter incubation delay which was attributed to the catalytic activity of anatase TiO₂. This difference in the incubation cycle affected the surface morphology of the Ru films on different TiO₂ substrates.

Keywords: Ru; Atomic layer deposition; Initial growth

An interface study of crystalline Fe/Ge multilayers grown by molecular beam epitaxy by S. Tari (pp. 4306-4310).

▶ Crystalline Ge was grown on single crystal Fe layers. ▶ Ge grows on Fe in islanding growth mode. ▶ Fe/Ge multilayers grown at 150°C is ferromagnetic. ▶ Fe/Ge multilyers grown at 200°C shows paramagnetic behavior.Fe/Ge multilayers were grown on single crystal Ge(001) substrates by molecular beam epitaxy. The structural, electronic and magnetic properties of Fe/Ge have been studied. The analysis shows that Fe grows in a layer-by-layer epitaxial growth mode on Ge(001) substrates at 150°C and no intermixing has been observed. Growth of a crystalline Ge film at 150°C on a single crystal Fe film has been observed. At this temperature Ge films grow by means of the island growth mode according to reflection of high energy electron diffraction patterns. Fe layers of 36nm thickness, deposited at 150°C on Ge(001) substrates, show two magnetization reversal values indicating the growth of Fe in two different crystal orientations. 36nm thick Fe and Ge layers grown at 150°C in Ge/Fe/Ge/Fe/Ge(001) sequence shows ferromagnetic behavior, however, the same structure grown at 200°C shows paramagnetic behavior.

Keywords: Spintronics; Interface; Epitaxy; Intermixing; Crystalline; MBE; XPS

The role of surface oxidation on luminescence degradation of porous silicon by Ersin Kayahan (pp. 4311-4316).

▶ The degradation of photoluminescence spectra of porous silicon during dark-aging and photo-aging was studied. ▶ Blue shifts in the photoluminescence spectra were observed. ▶ The change in the photoluminescence spectra has been investigated by overlapping of two different PL bands. ▶ Quantum size effect as being responsible for the porous silicon luminescence which, in addition, is influenced by the chemical composition of the porous silicon surface.This study reports a comparative analysis on time dependent degradation of photoluminescence (PL) spectra of porous silicon (PS) during dark-aging (DA) and photo-aging (PA). Fourier Transform Infrared (FTIR) spectroscopy studies have been performed to get an insight on possible chemical changes in the PS surface. It has been found that SiH_x bonds decrease progressively while SiO_x bonds increase. FTIR and PL measurements revealed presence of blue shifts in the PL spectra during the aging stages (PA and DA). While the PL intensity of dark aged PS shows a decrease during the first 3 weeks and an increase afterwards, the PL intensity decreases continuously for photo-aged PS. The change in the PL spectra has been investigated by overlapping of two different PL bands which are reflective of oxidation of PS surface and size of Si naonocrystallites. A possible bond configuration model about the oxidation of PS surface has also been proposed. The results are interpreted in terms of quantum size effects in PS and the influence of the surface composition.

Keywords: Porous silicon; Luminescence degradation; Oxidation; Photo and dark aging

Fast epitaxial growth of a-axis- and c-axis-oriented YBa₂Cu₃O7−_δ films on (100) LaAlO₃ substrate by laser chemical vapor deposition by Pei Zhao; Akihiko Ito; Rong Tu; Takashi Goto (pp. 4317-4320).

▶ Laser chemical vapor deposition of a-axis and c-axis oriented YBCO film. ▶ Rapid growth of epitaxial YBCO films faster than conventional MOCVD. ▶ High critical temperature of 90K with high deposition rate. a-axis- and c-axis-oriented YBa₂Cu₃O7−_δ (YBCO) films were epitaxially grown on (100) LaAlO₃ substrates by laser chemical vapor deposition. The preferred orientation in the YBCO film changed from the a-axis to the c-axis with increasing laser powers from 77 to 158W (the deposition temperatures from 951 to 1087K). The a-axis-oriented YBCO film showed in-plane epitaxial growth of YBCO [001]//LAO [001], and the c-axis-oriented YBCO film showed that of YBCO [010]//LAO [001]. A c-axis-oriented YBCO film with a high critical temperature of 90K was prepared at a deposition rate of 90μmh⁻¹, about 2–1000 times higher than that of metalorganic chemical vapor deposition.

Keywords: YBa; ₂; Cu; ₃; O; 7−; _δ; Laser chemical vapor deposition; High critical temperature; High deposition rate

Abrupt transition from wavelength structure to subwavelength structure in a single-crystal superalloy induced by femtosecond laser by Wei Zhang; Guanghua Cheng; Qiang Feng; Lamei Cao; Fengping Wang; Rongqing Hui (pp. 4321-4324).

▶ Transition from wavelength structure (LSFL) to subwavelength structure (HSFL). ▶ Transition is initiated by generation of new grooves on main ridges of LSFL ripples. ▶ Relationship between structures and their parametric dependence is established. ▶ Second harmonic generation is responsible for the formation of HSFL.The abrupt transition from low-spatial-frequency laser-induced periodic surface structure (LSFL) to high-spatial-frequency laser-induced periodic surface structure (HSFL) in single-crystal superalloy CMSX-4 during femtosecond laser irradiation has been reported. Microstructural investigations indicate that the transition was initiated by the generation of new grooves on the main ridges of LSFL ripples. This transition resulted in the period of HSFL nearly equal to half of LSFL period. Furthermore, the relationship between both LSFL and HSFL and their parametric dependence was established. The microstructural observation of the abrupt transition provides a morphological evidence of second harmonic generation being responsible for the formation of HSFL.

Keywords: Femtosecond laser; Microstructure; Abrupt transition; Second harmonic generation

Direct synthesis of mesoporous carbon from the carbonization of hydroxypropyl- β-cyclodextrin/silica composite and its catalytic performance by Hui Chun Wang; Bao Lin Li; Jiang Tao Li; Pei Lin; Xiao Bing Bian; Jiang Li; Bo Zhang; Zhuan Xin Wan (pp. 4325-4330).

▶ Mesoporous carbon was prepared by directly carbonizing β-HPCD/silica composite. ▶ Mesoporous carbon has a uniform wormlike structure and high surface area. ▶ Mesoporous carbon has certain degree graphitic phase characteristic in pore wall. ▶ Mesoporous carbon has high catalytic activity for the reduction of p-nitrotoluene.A simple and efficient route is reported for the synthesis of mesoporous carbon materials by directly carbonizing hydroxypropyl- β-cyclodextrin-silica composites. The resulting carbon materials, with uniform wormlike mesoporous structure and certain degree graphitic phase characteristics in porous wall, possess narrow pore size distribution, high surface area (>1000m²g⁻¹) and pore volume (>1.2cm³g⁻¹). It is worth mentioning that the carbon materials have high catalytic activity for the reduction of p-nitrotoluene using hydrazine hydrate as the reducing agent; moreover, the catalytic activity is not reduced notably after being reused for six times.

Keywords: Mesoporous carbon; Hydroxypropyl-; β; -cyclodextrin; Silica; Wormlike structure; Graphitic phase; Catalytic activity

Improved aging performance of vapor phase deposited hydrophobic self-assembled monolayers by Arun Kumar Gnanappa; Cian O’Murchu; Orla Slattery; Frank Peters; Tony O’Hara; Balázs Aszalós-Kiss; Syed A.M. Tofail (pp. 4331-4338).

Display Omitted▶ Degradation of Hydrophobic monolayer in contact with water. ▶ Growth of condensed silane mounds with hydrophilic sites around during immersion in water. ▶ Effect of nitrogen annealing on the improved aging properties of FOTS monolayer have been investigated. ▶ CF₃ and CF₂ groups on annealed surface explains the effect of annealing.A hydrophobic self-assembled monolayer (SAM) of fluoro-octyl-trichloro-silane (FOTS) was deposited on silicon using a vapor phase technique. The aging of the hydrophobic layer was examined using water contact angle measurements. It has been found that while such monolayer films suffer from a loss of hydrophobicity with time, pre-immersion nitrogen annealing can significantly improve the aging characteristics of these monolayers. The effect of nitrogen annealing on the improved aging properties of SAM coatings has been investigated by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The hydrolytic stability and the effect of nitrogen annealing were studied by morphological evolution during immersion. A spontaneous formation of silane mounds on the surface of the monolayers was found by AFM. These mounds have been irreversibly transformed from initially uniform hydrophobic surface layers. It is highly probable that the compliance of these mounds can reasonably allow hydrophilic sites to be located around the mounds. Interestingly, the density of these mounds formation is very less on the annealed samples. XPS reveals a higher level of coverage by the N₂-annealed film due to agglomeration. A relative abundance of CF₃ and CF₂ moieties in the annealed film may explain the enhancement of the hydrophobicity as revealed by higher level of water contact angle. This hydrophobicity was found to be significantly stable in water. This novel finding explains the improved hydrophobic stability of FOTS monolayers as primarily a morpho-chemical effect that originates from the densification of the monolayers upon annealing.

Keywords: Thin films; Self-assembled monolayer (SAM); FOTS; Hydrophobic coating; Annealing; Contact angle; Aging; Atomic force microscopy; Mounds; Agglomeration; XPS

The effect of post-annealing on surface acoustic wave devices based on ZnO thin films prepared by magnetron sputtering by Duy-Thach Phan; Gwiy-Sang Chung (pp. 4339-4343).

▶ ZnO thin films by r.f. sputtering. ▶ Effects of post-annealing on ZnO film quality. ▶ Effects of post-annealing on SAW properties. ▶ Optimal temperature for post-annealing.Zinc oxide (ZnO) thin films were deposited on unheated silicon substrates via radio frequency (RF) magnetron sputtering, and the post-deposition annealing of the ZnO thin films was performed at 400°C, 600°C, 800°C, and 1000°C. The characteristics of the thin films were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The films were then used to fabricate surface acoustic wave (SAW) resonators. The effects of post-annealing on the SAW devices are discussed in this work. Resulting in the 600°C is determined as optimal annealing temperature for SAW devices. At 400°C, the microvoids exit between the grains yield large root mean square (RMS) surface roughness and higher insertion losses in SAW devices. The highest RMS surface roughness, crack and residual stress cause a reduction of surface velocity (about 40m/s) and increase dramatically insertion loss at 1000°C. The SAW devices response becomes very weak at this temperature, the electromechanical coupling coefficient ( k²) of ZnO film decrease from 3.8% at 600°C to 1.49% at 1000°C.

Keywords: ZnO; r.f. Sputtering; SAW devices; Post-annealing

Quantitative relation between the thermionic contrast of metal surfaces and their degree of monocrystallization by Hiroyuki Kawano (pp. 4344-4349).

▶ We calculate effective work functions ( ϕ⁺, ϕ^e) for ionic and electronic emissions. ▶ All of ϕ⁺, ϕ^e and contrast (Δ ϕ^*≡ ϕ⁺− ϕ^e) agrees well with experimental data. ▶ Δ ϕ^*=4 c δ_m (1− δ_m) for monocrystallization degree ( δ_m) of 0.5–1. ▶ For W, Δ ϕ^*= c=0.53±0.09eV for δ_m≲0.5, agreeing with experimental data. ▶ Our theoretical model gives a clue to clarify the peculiarity of work function.For better understanding the peculiarities of work function, a simple model is devised to calculate the effective work functions ( ϕ⁺ and ϕ^e) for positive-ionic and electronic emissions from polycrystalline surfaces, which have a work function range from the maximum ( ϕ_max) to the minimum ( ϕ_min). Analysis of the theoretical results thus obtained and also of experimental data published to date enables us to find the quantitative relation between the thermionic contrast (Δ ϕ^*≡ ϕ⁺− ϕ^e) and the degree of monocrystallization ( δ_m), thereby yielding the three formulae of (1) Δ ϕ^*= c for 0< δ_m≲1/2 (polycrystal), (2) Δ ϕ^*=4 cδ_m (1− δ_m) for l/2≲ δ_m≲1 (polycrystal), and (3) Δ ϕ^*=0 for δ_m=1 (monocrystal). For a given surface consisting of a number of patchy faces ( i), δ_m corresponds to the largest among its fractional surface areas ( F_i) having different values of local work function ( ϕ_i). In a typical case of tungsten, the constant of c is evaluated theoretically to be 0.53±0.09eV, which well agrees with 0.59±0.06eV determined experimentally by many workers and also which satisfies the essential condition of Δ ϕ^*≦ c< ϕ_max− ϕ_min≈0.8–1.0eV. Our theoretical model is quite simple, but it is very useful for (1) evaluating both ϕ⁺ and ϕ^e with an uncertainty of less than ±0.1eV, (2) finding the quantitative relation between Δ ϕ^* and δ_m for actual surfaces of both poly- and monocrystals, and also (3) getting a substantial clue as to the problem how the effective work functions are governed by the surface characteristics of both F_i and ϕ_i.

Keywords: PACS; 73.30.+y; 79.20.RfEffective work function; Thermionic contrast; Monocrystallization degree; Local work function; Positive ion emission; Electron emission

The improvement of moisture resistance and thermal stability of Ca₃SiO₄Cl₂:Eu²⁺ phosphor coated with SiO₂ by Jiaqing Zhuang; Zhiguo Xia; Haikun Liu; Zepeng Zhang; Libing Liao (pp. 4350-4353).

▶ Sol–gel process was adopted to encapsulate the as-prepared Ca₃SiO₄Cl₂:Eu²⁺ phosphors with tetraethylorthosilicate (TEOS) as silicon coating reagent in order to enhance the chemical and thermal stability. ▶ The water-resistance stability of the coated phosphor was improved to some degree because the pH value and the luminance intensity variation were both smaller than the uncoated phosphor after steeping within the same time. ▶ The thermal stability of coated phosphors was enhanced obviously compared to the original samples based on the temperature dependent emission spectra measurement.Green-emitting phosphors Ca₃SiO₄Cl₂:Eu²⁺ were prepared by the high temperature solid-state method. Sol–gel process was adopted to encapsulate the as-prepared phosphors with tetraethylorthosilicate (TEOS) as silicon coating reagent. Fluorescence spectrometer, scanning electron microscopy (SEM) and powder X-ray diffraction (XRD) patterns were employed to characterize the emission spectra, the surface morphologies and the phase structures, respectively. The chemical stability testing was operated by the method of soaking the phosphors in deionized water and roasting them at different temperatures. The results indicated that the surfaces of the green phosphors were evenly coated by SiO₂ and the phase structure of the coated phosphors remained the same as the uncoated samples. The luminance centre of Eu²⁺ did not shift after surface treatment and the luminance intensity of coated phosphors was lower than that of the uncoated samples. The results demonstrated that the water-resistance stability of the coated phosphor was improved to some degree because the pH value and the luminance intensity variation were both smaller than the uncoated phosphor after steeping within the same time. Moreover, the thermal stability of coated phosphors was enhanced obviously compared to the original samples based on the temperature dependent emission spectra measurement.

Keywords: Phosphor; SiO; ₂; coating; Chemical stability; pH value

In situ growth of Ge-rich poly-SiGe:H thin films on glass by RF magnetron sputtering for photovoltaic applications by Chao-Yang Tsao; Ziheng Liu; Xiaojing Hao; Martin A. Green (pp. 4354-4359).

▶ The Si fraction influences various properties of the SiGe films. ▶ The decrease of Si fraction results in an increase of RMS roughness. ▶ The decrease of Si fraction results in an increase of grain size. ▶ The decrease of Si fraction narrows the band gap. ▶ The decreasing Si fraction leads to a dramatic decrease of the resistivity.Hydrogenated polycrystalline Si_xGe1−_x films, with a varying silicon fraction x≤0.246, were in situ deposited in an argon and hydrogen mixture at 500°C using radio frequency sputtering with an aim to develop a material for the bottom cell of a low cost monolithic tandem solar cell. Silicon and germanium atomic compositions of the films were determined by X-ray photoelectron spectroscopy (XPS). Structural evolution revealed by Raman and X-ray diffraction (XRD) indicated that the crystallinity of the films was improved with decreasing silicon fraction, accompanied with an increase of surface roughness verified by atomic force microscopy (AFM). Optical band gaps of these films derived from Tauc plots, which were calculated from reflectance/transmittance measurements, decreased with decreasing silicon fraction. Resistivity of the films, determined by four-point-probe technique, significantly decreased as well. High quality with low thermal budget obtained in this work suggests the films could be used in thin film solar cells on glass.

Keywords: Polycrystalline SiGe:H; Thin film; Sputtering

Effect of plasma pretreatment on adhesion and mechanical properties of UV-curable coatings on plastics by T. Gururaj; R. Subasri; K.R.C. Soma Raju; G. Padmanabham (pp. 4360-4364).

▶ Plasma treatment used to activate surface of polycarbonate and polymethylmethacrylate before deposition of sol–gel coatings ▶ Degree of surface activation is dependant on substrate and gets deactivated with time ▶ Plasma treatment improved the adhesion of sol–gel coatings on PC and PMMA substrates ▶ Improved mechanical properties in terms of scratch and abrasion resistance after plasma treatment.An attempt was made to study the effect of plasma surface activation on the adhesion of UV-curable sol–gel coatings on polycarbonate (PC) and polymethylmethacrylate (PMMA) substrates. The sol was synthesized by the hydrolysis and condensation of a UV-curable silane in combination with Zr- n-propoxide. Coatings deposited by dip coating were cured using UV-radiation followed by thermal curing between 80°C and 130°C. The effect of plasma surface treatment on the wettability of the polymer surface prior to coating deposition was followed up by measuring the water contact angle. The water contact angle on the surface of as-cleaned substrates was 80°±2° and that after plasma treatment was 43°±1° and 50°±2° for PC and PMMA respectively. Adhesion as well as mechanical properties like scratch resistance and taber abrasion resistance were evaluated for coatings deposited over plasma treated and untreated surfaces.

Keywords: Plasma activation; Plastics; Adhesion; Scratch resistance; Abrasion resistance

High sensitive self-assembled monolayer modified solid mounted resonator for organophosphate vapor detection by Jingjing Wang; Da Chen; Yaoguo Gan; Xuejun Sun; Yingying Jin (pp. 4365-4369).

▶ We present a novel design of the electro-acoustic thin film resonators based chemical sensors for trace organophosphate vapor detection. ▶ Our proposed sensor consisted of a solid mounted resonator working at 2.38GHz and a Cu²⁺/11-mercaptoundecanoic acid self-assembled monolayer. ▶ Our proposed sensor can yield a rapid, sensitive, reversible and reproducible response to nerve-agent stimulant (DMMP) vapor.We fabricated a self-assembled monolayer (SAM) modified solid mounted resonator (SMR) for organophosphate vapor detection. The SMR device consisted of a piezoelectric stack and an all-metal Bragg's reflector. The electrode surface is chemically modified with a Cu²⁺/11-mercaptoundecanoic acid SAM to capture organophosphate compounds. After chemical modification, both the resonance frequency and the Q-factor decrease. Fourier transform infrared external reflection spectroscopy was performed to verify the formation of SAM. Adsorption of organophosphate compounds onto the SAM increases its mass, and the resonance frequency proportionally goes down. The testing results show that the modified SMR can yield a rapid, sensitive, reversible and reproducible response to nerve-agent (dimethyl methyl phosphonate) vapor. This study proves that using the SAM modified SMR to detect trace organophosphate vapor is feasibility.

Keywords: Film bulk acoustic resonator; Self-assembled monolayer; Cu; ²⁺; /11-mercaptoundecanoic; Organophosphate vapor

Controlling wear failure of graphite-like carbon film in aqueous environment: Two feasible approaches by Yongxin Wang; Liping Wang; Qunji Xue (pp. 4370-4376).

Display Omitted▶ Wear of GLC film in aqueous environment includes micro-plough and delamination. ▶ Local delamination is critical to wear failure of GLC film in aqueous environment. ▶ Increase of film density will significantly reduce the delamination. ▶ Fabricating a proper interlayer can effectively eliminate the delamination.Friction and wear behaviors of graphite-like carbon (GLC) films in aqueous environment were investigated by a reciprocating sliding tribo-meter with ball-on-disc contact. Film structures and wear scars were studied by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and a non-contact 3D surface profiler. A comprehensive wear model of the GLC film in aqueous environment was established, and two feasible approaches to control critical factor to the corresponding wear failure were discussed. Results showed that wear loss of GLC films in aqueous environment was characterized by micro-plough and local delamination. Due to the significant material loss, local delamination of films was critical to wear failure of GLC film in aqueous environment if the film was not prepared properly. The initiation and propagation of micro-cracks within whole films closely related to the occurrence of the films delamination from the interface between interlayer and substrate. The increase of film density by adjusting the deposition condition would significantly reduce the film delamination from substrate, meanwhile, fabricating a proper interlayer between substrate and GLC films to prevent the penetration of water molecules into the interface between interlayer and substrate could effectively eliminate the delamination.

Keywords: Graphite-like carbon; Wear model; Delamination; Film density; Interlayer

Waterborne crackle decorative coatings and crack patterns by Yongchao Zhao; Linhui Qiang; Juntao Yan; Shijin Dong; Qiaoyun Zhang; Lisi Zhang; Xuejun Cui; Hongyan Wang (pp. 4377-4383).

▶ Three junction types of crack patterns were prepared in our study, which were T-junctions, Y-junctions and mixed type. ▶ Crack patterns with different spacing were prepared. ▶ Ventilation makes the cracks spacing small.A preparation method of waterborne crackle decorative coatings was reported in this paper and the factors that influence crack patterns were investigated. The crackle coating consisted of a waterborne basecoat and a waterborne topcoat. The basecoat was made from two-component epoxy emulsion and the topcoat was made from fluorine-containing acrylic emulsion, silicone-acrylic emulsion or styrene-acrylic emulsion. Three junction types of crack patterns were prepared by the three top coatings, which were T-junction, Y-junction and mixed junction. T-junction type with long and straight cracks was prepared from styrene-acrylic emulsion 296DS. Y-junction type with curve and short cracks was prepared from fluorine-containing acrylic emulsion A603C and mixed junctions type was made from silicone-acrylic emulsion. Crack patterns with different spacing were prepared by controlling the thickness of topcoat, dryness of basecoat or conditions of film forming. The characterize methods of type and spacing for crack pattern were developed and properties of coating film including adhesion, water resistance, scrub resistance and so on were tested. The results showed that the crackle coatings possessed satisfactory properties for practical application.

Keywords: Crackle coating; Waterborne coating; Crack pattern

Effect of reaction systems and surfactant additives on the morphology evolution of hydroxyapatite nanorods obtained via a hydrothermal route by Tianyuan Ma; Zhiguo Xia; Libing Liao (pp. 4384-4388).

▶ We prepared well-dispersed hydroxyapatite (HA) nanorods with different morphologies by a hydrothermal method in oleic acid, ethanol and water reaction system. ▶ The controlled experimental conditions in the systems, such as the content ratio of oleic acid/ethanol, pH value and the content ratio of Ca/P source had an significant effect on the morphology evolution of as-prepared HA nanorods. ▶ The selected surfactant additives, such as cetyltriethylammnonium bromide (CTAB), sodium dodecyl sulfate (K12) also play an important role in the formation of the uniform morphology of HA nanorods.Well-dispersed hydroxyapatite (HA) nanorods with different morphologies were synthesized by a hydrothermal method in oleic acid, ethanol and water reaction system, and the surfactant assisted modifications effect was also comparatively studied. The structure and morphology of samples were characterized using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM), respectively. The effect of reaction systems and surfactant additives on the morphology evolution of HA nanorods were discussed in detail. The results showed that the controlled experimental conditions in the systems, such as the content ratio of oleic acid/ethanol, pH value and the content ratio of Ca/P source had an significant effect on the morphology evolution of as-prepared HA nanorods. Further, the selected surfactant additives, such as cetyltriethylammnonium bromide (CTAB), sodium dodecyl sulfate (K12) also play an important role in the formation of the uniform morphology of HA nanorods. Some possible formation mechanisms of the HA nanorods in the present reaction systems is proposed.

Keywords: Inorganic compounds; Chemical synthesis

CuO–PAA hybrid films: Chemical synthesis and supercapacitor behavior by J.S. Shaikh; R.C. Pawar; A.V. Moholkar; J.H. Kim; P.S. Patil (pp. 4389-4397).

▶ Hybrid CuO–PAA thin films synthesized by spin coating at room temperature. ▶ Effect of annealing temperature in CuO–PAA hybrid films on specific capacitance, rate capability and stability in 1M H₂SO₄ is studied in systematic way. ▶ The film annealed at 500°C temperature exhibits highest specific capacitance of 136Fg⁻¹.We report the synthesis of CuO–Poly (acrylic) acid (PAA) hybrid thin films by a cost-effective spin coating technique for supercapacitor application. Coated films were annealed at 300, 400 and 500°C, to study the annealing effect on the supercapacitor behavior. Further films were characterized by X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform-Raman spectroscopy (FT-Raman) and Fourier transform-Infrared spectroscopy (FT-IR) techniques. Energy dispersive spectroscopy (EDS) shows the formation of amorphous blend of CuO and Cu₂O phases at 300°C. Further, films annealed at 400 and 500°C exhibit polycrystalline phase pure CuO with monoclinic structure. The scanning electron microscopy (SEM) micrographs show the transition of island-like structure to CuO crystals surrounded by PAA grafted composite ring with increase in annealing temperature. The possible growth mechanism of PAA and CuO bonding is discussed. Cyclic voltammetry (CV) is employed to calculate the specific capacitance ( C_sp) in 1M H₂SO₄ electrolyte. It is observed that the C_sp increases from 41 to136Fg⁻¹ with increase in annealing temperature.

Keywords: Copper oxide (CuO); Polyacrylic acid (PAA); Supercapacitor

Microstructure and friction and wear behavior of laser boronizing composite coatings on titanium substrate by Chun Guo; Jiansong Zhou; Jierong Zhao; Baogang Guo; Youjun Yu; Huidi Zhou; Jianmin Chen (pp. 4398-4405).

▶ Three kinds of laser boronizing composite coatings were in-situ synthesized on Ti substrate by using powders of B, BN and B₄C as starting materials. ▶ Microstructures of the laser boronizing composite coatings were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). ▶ Moreover, the friction and wear behavior of the boronizing composite coatings under dry sliding condition were systematically investigated.Three kinds of laser boronizing composite coatings were in situ synthesized on Ti substrate by using powders of B, BN and B₄C as starting materials. Microstructures of the laser boronizing composite coatings were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM); and their worn surface morphologies were also observed by using SEM. Moreover, the friction and wear behavior of the boronizing composite coatings under dry sliding condition were evaluated using a UMT-2MT friction and wear tester. It was found that all the three types of laser boronizing composite coatings had higher microhardness and better wear resistance than pure Ti substrate; and their microstructure and wear resistance varied with varying pre-placed powders of B, BN, and B₄C. Under the same dry sliding test conditions, the wear resistance of the three kinds of laser boronizing composite coatings, i.e., sample 1 prepared from pre-placed B, sample 2 obtained from pre-placed BN, and sample 3 fabricated from pre-placed B₄C, is ranked in an order of sample 1>sample 2>sample 3, which, surprisingly, well conforms to their order of hardness and friction coefficients.

Keywords: Titanium substrate; Laser boronizing; Composite coating; Microstructure; Friction and wear behavior

Well-confined Yb:GdVO₄ laser waveguide formed by MeV C³⁺ ion implantation by Liang-Ling Wang; Jie Cheng; Xiao-Jun Cui (pp. 4406-4409).

▶ The Yb:GdVO₄ planar waveguide has been fabricated by ion implantation. ▶ The dark mode spectra were measured by the prism coupling method. ▶ The refractive index profile includes a non-leaky guiding region. ▶ The beam propagation results indicate that the waveguide can be well-confined. ▶ The efficient Yb³⁺-related emission in Yb:GdVO₄ was observed at room temperature.The planar waveguide in x-cut Yb:GdVO₄ crystal has been fabricated by 6.0MeV carbon ion implantation with the fluence of 1×10¹⁴ ions/cm² at room temperature. The modes of the waveguide were measured by the prism-coupling method with the wavelength of 633nm and 1539nm, respectively. An enhanced ordinary refractive index region was formed with a width of about 4.0μm beneath the sample surface to act as a waveguide structure. By performing a modal analysis on the observed transverse magnetic polarized modes, it was found that all the transverse magnetic polarized modes can be well-confined inside the waveguide. Strong Yb-related photoluminescence in Yb:GdVO₄ waveguide has been observed at room temperature, which reveals that it exhibits possible applications for integrated active photonic devices.

Keywords: PACS; 61.80.−; x; 42.70.Hj; 42.65.WiIon irradiation effects; Laser materials; Nonlinear waveguide

Wettability of ZnO: A comparison of reactively sputtered; thermally oxidized and vacuum annealed coatings by Harish C. Barshilia; N. Selvakumar; Nisha Pillai; L. Mayura Devi; K.S. Rajam (pp. 4410-4417).

▶ The wettability of reactively sputtered ZnO, thermally oxidized Zn–ZnO and vacuum annealed ZnO coatings was studied by using various probe liquids. ▶ The wettability studies demonstrated that reactively sputtered ZnO coatings were hydrophobic, whereas thermally oxidized Zn–ZnO and vacuum annealed ZnO coatings were superhydrophobic with static water contact angles of 110.3°, 158.5° and 155.2°, respectively. ▶ The dynamic contact angle measurements indicated advancing and receding contact angles of 2° and 4°, respectively for thermally oxidized Zn–ZnO and vacuum annealed ZnO coatings. ▶ The work of adhesion of water was very low for thermally oxidized Zn–ZnO coating (5.06mJ/m²) when compared to reactively sputtered ZnO coating (90.41mJ/m²). Superior hydrophobic properties of thermally oxidized Zn–ZnO coatings are attributed to nanorod cluster like morphology along with the presence of high fraction of micron scale air pockets. ▶ The apparent surface free energy values for reactively sputtered ZnO, thermally oxidized Zn–ZnO and vacuum annealed ZnO coatings were 32.95, 23.21 and 18.78mJ/m², respectively.We have studied the wettability of sputter deposited ZnO, thermally oxidized Zn–ZnO and vacuum annealed ZnO coatings. The X-ray diffraction patterns showed the formation of hexagonal-wurtzite structure of ZnO, which was further confirmed by micro-Raman spectroscopy data. The X-ray photoelectron spectroscopy data indicated that the sputter deposited ZnO coatings were more stoichiometric than thermally oxidized Zn–ZnO and vacuum annealed ZnO coatings. The wettability measurements indicated that water contact angles of 158.5° and 155.2° with sliding angles of 2° and 4° were achieved for thermally oxidized Zn–ZnO and vacuum annealed ZnO coatings, respectively. The superhydrophobicity observed in thermally oxidized Zn–ZnO and vacuum annealed coatings is attributed to the nanorod cluster like morphology along with the presence of high fraction of micron scale air pockets. The water droplet on such surfaces is mostly in contact with air pockets rather than solid surface, leading to high contact angle. Whereas, the sputter deposited ZnO coatings exhibited a maximum water contact angle of 110.3°. This is because the sputter deposited ZnO coatings exhibited a densely packed nanograin-like microstructure without any air pockets. The work of adhesion of water was very low for thermally oxidized Zn–ZnO (5.06mJ/m²) and vacuum annealed ZnO coatings (6.71mJ/m²) when compared to reactively sputtered ZnO coatings (90.41mJ/m²). The apparent surface free energy (SFE) for these coatings was calculated using Neumann method and the SFE values for sputter deposited ZnO, thermally oxidized Zn–ZnO and vacuum annealed ZnO coatings were 32.95, 23.21 and 18.78mJ/m², respectively.

Keywords: Wettability; Surface free energy; Zinc oxide; FESEM; XRD; Neumann method; Sputtering; Thermal oxidation; Transmittance

Thermal degradation of Ni-based Schottky contacts on 6H–SiC by Bohumil Barda; Petr Macháč; Stanislav Cichoň; Marie Kudrnová (pp. 4418-4421).

▶ Thermal degradation of Ni and Ni₂Si Schottky contacts on lightly doped SiC. ▶ Better Schottky contacts were achieved by Ni after annealing at 750 and 850°C. ▶ Ni Schottky contacts gradually degraded after annealing at 960, 1065 and 1150°C. ▶ Ni₂Si contacts achieved ohmic behavior after annealing at 960°C. ▶ We propose explanation for the discrepancy reported in the literature for Ni contacts.We prepared Ni and Ni₂Si Schottky contacts on lightly doped (5.5×10¹⁵cm⁻³) n-type 6H–SiC and evaluated their thermal degradation after annealing in the temperature range of 750–1150°C. Ni contacts had Schottky behavior after annealing at 750 and 850°C; they gradually degraded at 960 and 1065°C, and achieved ohmic behavior at 1150°C. Ni₂Si contacts had higher values of saturation current density and lower Schottky barrier heights than Ni contacts after annealing at 750 and 850°C, and an abrupt transition from Schottky behavior at 850°C to ohmic behavior at 960°C. We assume that the abrupt transition from Schottky to ohmic behavior in the case of Ni₂Si metallization is caused by its low reactivity with silicon carbide, which was verified by XPS depth profiling. The results indicate that the discrepancy in the behavior of Ni contacts on lightly doped SiC reported in the literature might have been caused by non-equal processing or by inaccurate determination of the annealing temperature.

Keywords: SiC; Nickel; Nickel silicide; Schottky diode; Ohmic contact; Low doping level

Characterization of a controlled electroless deposition of copper thin film on germanium and silicon surfaces by Louis Scudiero; Ayuba Fasasi; Peter R. Griffiths (pp. 4422-4427).

▶ Cu films are deposited onto Ge disks and Si coupons from CuSO₄ solution containing dilute HF at RT. ▶ These films are characterized by AFM, XPS and PXRD. ▶ AFM images reveal differences in microstructure and thickness between films grown on Ge and Si. ▶ XPS shows the deposited Cu is in its elemental state (Cu⁰) and oxidizes very slowly with time in air. ▶ Cu films grows preferentially in the (111) and (200) orientations on both Si and Ge as shown by XRD.Nanofilms of copper were deposited on silicon and, for the first time, on polycrystalline germanium substrates by electroless deposition. Germanium or silicon disks were immersed in a 10mM copper sulfate solution containing dilute hydrofluoric acid at room temperature. This simple one-step deposition does not require the use of laborious operations or expensive equipment, that the reaction medium be degassed, or that the film be annealed. The copper film grows in a few minutes, producing a film on both Ge and Si that covers a very large area of the substrate in contrast to other metals such as Au, Ag, Pt and Pd for which deposition on Ge and Si produces islands or dendrites. Atomic force microscopy, X-ray photoelectron spectroscopy (XPS) and powder X-ray diffraction (PXRD) were used to characterize the microstructure and confirmed the formation of elemental copper nanofilms. The AFM micrographs reveal a Stranski–Krastanov type of film growth (layers+islands) that varies with the length of time the Ge or Si substrate is immersed in the CuSO₄ solution. Thicker films were observed on the Ge than on the Si substrate resulting in larger particles and rougher surface than on Si. XPS analysis shows that the elemental copper is deposited on both Ge and Si substrates and that the films oxidize over a period of weeks with air exposure at room temperature. Finally, PXRD data reveal two preferential orientations (111) and (200) for the copper crystallites grown on both Ge and Si. The same intensity of the (111)-texture was measured on both Ge and Si substrate which is an important result because it has been shown that the (111) texture reduces stress-induced voiding and increases resistance to electromigration in metal interconnects.

Keywords: Electroless deposition; Copper films; Oxidation; Silicon substrate; Germanium substrate

Dehydrogenation catalyst for optical organic-hydride detection by Kimio Yoshimura; Teruyuki Hakoda; Shunya Yamamoto; Masahito Yoshikawa (pp. 4428-4431).

▶ The leak detection of organic hydrides. ▶ Determination of dehydrogenation activity of Pt, Pd, Rh, Ir, Ni, and Cu. ▶ The hydrogen generation was observed over 100°C for Pt and Pd. ▶ The WO₃ films covered with Pt and Pd were prepared by a reactive RF-sputtering. ▶ Pt/WO₃ and Pd/WO₃ films heated to 200°C could detect organic-hydrides optically.The leak detection of organic hydrides, which are approvable carriers to store and transport hydrogen, has importance for safe usage. The potential use of hydrogen gasochromic materials was investigated with the combination of dehydrogenation catalysts for this purpose. The dehydrogenation activity of catalytic metals which are Pt, Pd, Rh, Ir, Ni, and Cu, was determined with loading alumina pellets with a content of 1wt.% for 5% cyclohexane as a organic hydride in N₂ gas. The hydrogen generation was observed over 100°C for Pt and Pd, and over 150°C for Rh and almost negligible for other metals. The Pt and Pd were selected as dehydrogenation catalysts to be combined with WO₃ of hydrogen gasochromic materials. The WO₃ films covered with Pt and Pd were prepared by a reactive RF-sputtering. The coloration of as prepared film was observed over 150°C when exposing with cyclohexane in N₂ gases. We found that Pt/WO₃ and Pd/WO₃ films heated to around 200°C were applicable to optical organic-hydride sensors.

Keywords: Dehydrogenation catalyst; Organic hydride; Tungsten trioxide; Leak detection; Optical sensor

Control of surface ripple amplitude in ion beam sputtered polycrystalline cobalt films by Jose M. Colino; Miguel A. Arranz (pp. 4432-4438).

▶ Low energy (1keV) ion sculpting is realised on polycrystalline cobalt films of varying thickness. ▶ Surface ripple patterns in polycrystalline Co confirm the shadowing instability mechanism in the initial selection of ripple pattern wavelength. ▶ Ripple pattern amplitude is controllable with the film roughness prior to ion erosion.We have grown both polycrystalline and partially textured cobalt films by magnetron sputter deposition in the range of thickness (50–200nm). Kinetic roughening of the growing film leads to a controlled rms surface roughness values (1–6nm) increasing with the as-grown film thickness. Ion erosion of a low energy 1keV Ar+ beam at glancing incidence (80°) on the cobalt film changes the surface morphology to a ripple pattern of nanometric wavelength. The wavelength evolution at relatively low fluency is strongly dependent on the initial surface topography (a wavelength selection mechanism hereby confirmed in polycrystalline rough surfaces and based on the shadowing instability). At sufficiently large fluency, the ripple wavelength steadily increases on a coarsening regime and does not recall the virgin surface morphology. Remarkably, the use of a rough virgin surface makes the ripple amplitude in the final pattern can be controllably increased without affecting the ripple wavelength.

Keywords: Ion sculpting; Thin films; Sputtering; Surface ripples; Force microscopy; X-ray

Influence of SnS buffer layers on the growth and properties of nanostructured Bi₂S₃ films by chemical bath deposition by Chao Gao; Honglie Shen; Zhou Shen; Lei Sun (pp. 4439-4442).

▶ Rod-shaped nanostructure Bi₂S₃ films are obtained. ▶ SnS buffer layer promotes the nucleation of Bi₂S₃ on the substrate. ▶ Homogeneity and adhesion of the Bi₂S₃ films are improved by the addition of SnS buffer layer. ▶ Electrical conductivity and optical absorption of the Bi₂S₃ films are also improved by the addition of SnS buffer layer.Nanostructured Bi₂S₃ films that comprise rod-shaped particles were prepared on glass substrates by chemical bath deposition. When a SnS buffer layer was deposited on the substrate before the deposition of the Bi₂S₃ films, the homogeneity and the adhesion of the prepared Bi₂S₃ films are largely improved. Furthermore, when the buffer layer is inserted, the electrical conductivity of the films increases from lower than 10⁻⁶Ω⁻¹cm⁻¹ to 4×10⁻⁵Ω⁻¹cm⁻¹, and the average optical absorption in the band between 350nm and 800nm increases from around 41% to around 76%. The reason for these results is considered to be that the SnS layer can promote the nucleation of the Bi₂S₃ on the substrate.

Keywords: Bi; ₂; S; ₃; films; Nanostructure; Buffer layer; Electrical and optical properties

Enhanced washing durability of hydrophobic coating on cellulose fabric using polycarboxylic acids by Wenqi Huang; Yanjun Xing; Yunyi Yu; Songmin Shang; Jinjin Dai (pp. 4443-4448).

▶ Polycarboxylic acids improve washing durability of hydrophobic cotton. ▶ Distance between terminal carboxylic acid groups plays key role on improvement. ▶ Number of carboxylic acid group shows limited influence on improvement.Nine polycarboxylic acids were used to improve washing durability of hydrophobic cellulose fabric finished by sol–gel method. By simultaneous forming ester-bridge between cellulose and silica layer by ester bond, polycarboxylic acids could anchor silica coating onto cellulose fabric to strengthen the adhesion of organic–inorganic hybrid coating. The wettability of treated fabrics was characterized by water contact angle, spray test and hydrostatic pressure test. The results showed that all investigated polycarboxylic acids could improve the durability. The polycarboxylic acid with proper distance between terminal carboxylic acid groups and number of carboxylic acid groups showed the highest durability. 1,2,3,4-butanetetracarboxylic acid (BTCA) led to the best durability of hydrophobic cellulose fabric with water contact angle of 137.6° (recovery percentage of 94.2%) after 30 washing times. The effect of BTCA on durability was characterized by scanning electron microscopy. This study demonstrated that the surface treatment using polycarboxylic acids and mixed organosilanes is a promising alternative for achieving durable hydrophobic fabrics.

Keywords: Hydrophobicity; Cotton; Sol–gel; Durability; Polycarboxylic acid

The role of the substrate in micro-scale scratching of epoxy–polyester films by M. Barletta; A. Gisario (pp. 4449-4463).

▶ Influence of the contact conditions between epoxy–polyester coatings and 100, 200 and 800μm tip-radius indenter. ▶ Role of the loading conditions on the scratch and penetration resistance of the epoxy–polyester coatings. ▶ Analysis of the different responses of the epoxy–polyester coatings when deposited on untreated or pre-treated metal substrates and on intermediate layer of silicon-based release coating. ▶ Scratch results lead to a better understanding of the intrinsic roles of the polymeric material and substrate. ▶ Influence of the interfacial adhesion between epoxy–polyester coating and metal or silicon based substrate.The present investigation analyzes the deformation response of electrostatically sprayed epoxy–polyester powder coatings by ‘in situ’ micro-mechanical tests.The characterization of the performance of the coatings was carried out by micro-scale scratching, by varying the indenter type, the applied load and the sliding speed. The tests were carried out on polymeric coatings deposited on as-received, micro and macro-corrugated AISI 304 stainless steel substrates and ‘rigidly adhered’ to them. Further tests were performed on ‘free-standing’ coatings, that is, on the as-received metal substrates pre-coated with an intermediate layer of silicon-based heat curable release coating.Experimental data allow us to evaluate the influence of the contact conditions between substrate and indenter and the role of the loading conditions on the scratch and penetration resistance of the epoxy–polyester coatings. The different responses of the polymeric coatings when deposited on untreated or pre-treated substrates as well as on an intermediate layer of release coating, contribute to a better understanding of the intrinsic roles of the polymeric material and substrate as well as the influence of the interfacial adhesion between coating and substrate.

Keywords: Powder coatings; Scratch; Indentation; Adhesion; Substrate

Corrosion behavior of TiO₂ films on Mg–Zn alloy in simulated body fluid by Shuai Chen; Shaokang Guan; Bin Chen; Wen Li; Jun Wang; Liguo Wang; Shijie Zhu; Junhua Hu (pp. 4464-4467).

▶ TiO₂ films were fabricated on Mg–Zn alloy by DC reactive magnetron sputtering. ▶ TiO₂ films were of anatase structure without heat treatment. ▶ TiO₂ films could prevent substrates from rapid corrosion. ▶ TiO₂ films could induce the growth of HAp.Magnesium alloys have been widely investigated in the field of biomaterials due to their moderate mechanical properties close to human bone and gradual degradation in human physiological environment without second surgeries. But results from clinical studies showed that magnesium implants suffered from too rapid degradation in human physiological environment. To reduce the degradation rate of magnesium alloys, surface modification is essential and effective besides element alloying. In this study, TiO₂ films were deposited on Mg–Zn alloy by direct current reactive magnetron sputtering. The morphology and structure of the films were characterized by atomic force microscopy (AFM), scanning electron microscope (SEM) and X-ray diffraction (XRD). The corrosion resistance in simulated body fluid (SBF) at 37°C was evaluated by potentiodynamic polarization and hydrogen evolution tests. The corrosion behavior of the samples was investigated by SEM with energy dispersive spectroscopy (EDS) after immersion for different periods. The results showed that the compact films were composed of particles with the size of about 100nm and could effectively improve the corrosion resistance in SBF. After immersion for 10 days, the corrosion rates of the substrates and samples with TiO₂ films were 4.13mm/y and 1.95mm/y, respectively. During the immersion, the TiO₂ films could induce the growth of hydroxyapatite (HAp) to improve the bioactivity of the samples.

Keywords: Magnesium; TiO; ₂; film; Corrosion behavior; Simulated body fluid; HAp

Flattening of low temperature epitaxial Ge1−_xSn_x/Ge/Si(100) alloys via mass transport during post-growth annealing by Wei Wang; Shaojian Su; Jun Zheng; Guangze Zhang; Chunlai Xue; Yuhua Zuo; Buwen Cheng; Qiming Wang (pp. 4468-4471).

▶ Epitaxial Ge1−_xSn_x alloys were grown on Ge buffer/Si(100), with x≤0.08. ▶ High crystalline quality Ge_0.97Sn_0.03 alloy was grown on Ge buffer/Si(100). ▶ High crystalline quality Ge buffer was grown directly on Si(100). ▶ The surface morphology evolution was observed during post-growth annealing. ▶ The surface RMS roughness decreased after annealing.Epitaxial Ge1−_xSn_x alloys were grown on Si(100) by MBE with a Ge buffer layer. The Ge buffer was grown by two step method using GeH₄ as gas source. The epitaxial layers were characterized by Rutherford Backscattering Spectrometry (RBS), Double Crystal X-ray Diffraction (DCXRD), and Atomic Force Microscopy (AFM) measurements. Then the Ge1−_xSn_x alloys were annealed at 500°C for times ranging from 0 to 10min. During the annealing process, the surface morphology evolution, from three-dimensional round mounds to nearly two-dimensional ripples, and finally to flat, was observed. This result can be attributed to mass transport by surface diffusion.

Keywords: Germanium tin alloys; Germanium buffer; Surface morphology evolution; Mass transport

A mesoporous hollow silica sphere (MHSS): Synthesis through a facile emulsion approach and application of support for high performance Pd/MHSS catalyst for phenol hydrogenation by Xu Yang; Shijun Liao; Jianhuang Zeng; Zhenxing Liang (pp. 4472-4477).

Display Omitted▶ Hollow sphere with mesoporous silica shell. ▶ A facile sol–gel/emulsion method. ▶ High surface area, narrow pore size distribution and good thermal stability. ▶ High catalytic performance (phenol hydrogenation) of Pd/MHSS.A facile route to synthesize mesoporous hollow silica sphere (MHSS) via TEOS emulsion droplet assisted with dodecyl amine (DDA) was developed in this work. The particle sizes of MHSS are around 400–600nm and the BET surface area is high up to 951m²g⁻¹ and with a uniform pores diameter of 3.7nm in the silica wall. Thermogravimetric analysis found that the MHSS displayed good thermal stability. The effects of solvent, TEOS amount and DDA addition on the property of MHSS were also investigated. It was found that the solvent composition and the required DDA concentration are the key factors for the determination of hollow structure. Pd loaded MHSS catalyst showed high catalytic activity and good recycling ability in the liquid phenol hydrogenation under mild reaction conditions.

Keywords: Emulsion; Hollow sphere; Hydrogenation; Mesoporous

Characterization of a nanometer-thick sputtered polytetrafluoroethylene film by Lei Li; Paul M. Jones; Yiao-Tee Hsia (pp. 4478-4485).

▶ Characterized nanometer-thick sputtered PTFE films. ▶ Found that the nanometer-thick sputtered PTFE has crosslinked molecular structure with short segments between the crosslink points. ▶ Found that the nanometer-thick sputtered PTFE film has high thermal stability, low surface tension and good mechanical properties. ▶ Discussed structure–property relationships.Fast growth of nanotechnology, e.g. hard disk drive (HDD) and microelectromechanical system/nanoelectromechanical system (MEMS/NEMS), requires nanometer-thick protection films with high thermal stability and low surface energy. In this paper, we report the characterization results of a nanometer-thick sputtered polytetrafluoroethylene (PTFE) film prepared by radio frequency (RF) sputtering. Atomic force microscopy (AFM) and X-ray reflectivity (XRR) results show that the nanometer-thick sputtered PTFE film has good uniformity. Thermally programmed desorption (TPD) results show that the film is thermally stable up to 430°C. Surface energy measurement via contact angle method shows that the film has low surface energy with the thickness as low as 1.5nm. X-ray photoelectron spectroscopy (XPS) data suggests that the film has crosslinked molecular structure, which results in amorphous morphology as shown by X-ray diffraction (XRD) data. Nano-indentation testing shows that the sputtered film has higher hardness and modulus than bulk PTFE. The structure–property relationship has been discussed.

Keywords: Polymer thin film; PTFE; RF sputter; Thermal stability; Surface energy; Crosslink

Effect of heat treatment, top coatings and conversion coatings on the corrosion properties of black electroless Ni–P films by Y. Liu; D. Beckett; D. Hawthorne (pp. 4486-4494).

▶ Heat treatment, organic coatings and conversion coatings of black Ni-P film were investigated. ▶ Their morphology and compositions were compared to study the effect on their corrosion resistance. ▶ Their corrosion resistance was investigated by polarization measurements and salt spray test. ▶ HydroLac as the organic coating showed the excellent corrosion resistance. ▶ Conversion coating by Electrotarnil B passed the salt spray test for 3000h.Electroless black nickel–phosphorus plating is an advanced electroless nickel plating process formulated to deposit a black finish when processed through an oxidizing acid solution. Heat treatment, five types of top organic coating techniques and one conversion coating technique with three different experimental conditions were investigated to stabilize the black film and increase the hardness and corrosion resistance. Morphology and compositions of electroless nickel–phosphorous films with or without heat treatment, with five types of top organic coatings, and with three conversion coatings were compared to examine nickel, phosphorus, oxygen, carbon, silicon and chrome contents on the corrosion resistance of black surfaces by energy dispersive X-ray microanalysis and scanning electron microscope. Corrosion resistance of black electroless nickel–phosphorus coatings with or without heat treatment, with five types of top organic coatings, and with three conversion coatings was investigated by the polarization measurements and the salt spray test in 5% NaCl solution, respectively. HydroLac as the top organic coating from MacDermid showed the excellent corrosion resistance and the black EN film did not lose the black color after 48h salt spray test. Electrotarnil B process with 0.5 ASD for 1min stabilized the black Ni–P film immediately and increased the hardness and corrosion performance of the black Ni–P film. The black Ni–P coating with Electroarnil B process passed the 5% NaCl salt spray test for 3000h in the black color and had a minimal corrosion current 0.8547μA/cm² by the polarization measurement.

Keywords: Electroless nickel–phosphorus; Black treatment; Heat treatment; Top coating; Conversion coating; Corrosion

Investigations of DPPC effect on Al₂O₃ particles in the presence of (phospho)lipases by the zeta potential and effective diameter measurements by Agnieszka Ewa Wiącek (pp. 4495-4504).

▶ The metal oxide surface Al₂O₃ can be modified to a wide range of functionality owing to the presence of active surface groups. ▶ The presence of DPPC in the Al₂O₃ in 10⁻³M NaCl suspension affects the zeta potential and the stabilization of the suspension. ▶ In the monovalent electrolyte solution bonding between –PO moiety of the DPPC molecule and H–O-moiety on the alumina particle surface occurs. ▶ Despite the dispersion and electrostatic forces (ionic groups), possible steric stabilization and hydrophobic (phospholipid chain–chain) interactions should also be considered for description of the suspension properties. ▶ In the presence of lipase the zeta potential of Al₂O₃/DPPC particles is more negative (two palmitic acid molecules formed) than in the presence of PLA₂. ▶ It seems that pH=8 of the investigated Al₂O₃/DPPC in the NaCl systems, concerning the zeta potential changes, is optimal for lipase action and the effect of lipase is remarkable, contrary to that of PLA₂. ▶ The simultaneous changes occurring in the hydrophilicity of DPPC layers deposited on the solid surface in the presence of enzymes allow to control of the hydrolysis process and obtain surfaces of defined properties.Adsorption of phospholipid (DPPC) from NaCl electrolyte solution (or from chloroform solution) on Al₂O₃ particles in suspension was investigated by means of the zeta potential and effective diameter measurements as a function of pH using dynamic light scattering. Al₂O₃ particles were precovered with an amount of dipalmitoylphosphatidylcholine sufficient to cover the alumina surface by the statistical mono- or bilayer (ML or BL). It was found that DPPC from NaCl solution was adsorbed on Al₂O₃ surface independently of phospholipid concentration, which resulted in decrease of the initial zeta potential of Al₂O₃ suspension. When alumina was precovered with DPPC from chloroform (ML or BL) some reorientation of phospholipid molecules could take place. Despite the lowering of the zeta potential value in both cases (from both aqueous and chloroform solution) DPPC stabilized the Al₂O₃ particle aggregates, which resulted in smaller and smoother changes of the aggregate size during 2-experiment hours due to steric and electrostatic stabilization. In the next series of experiments the effect of enzymes (phospholipase A₂ or lipase Candida cylindracea) on the behavior of Al₂O₃/DPPC particles was studied. The kind of the enzymes, the hydrolysis products, which were palmitic acid and lysophosphatidylcholine (or glycerylphosphorylcholine), and pH changed the suspension zeta potential and influenced the stability of these systems. Lipase was found to be a more active enzyme than phospholipase. The electrokinetic parameters connected with the adsorption process and resulting from the enzyme action seem to be helpful for characterization of the Al₂O₃/DPPC suspension and the activity of the enzymes, which is discussed in the paper.

Keywords: Al; ₂; O; ₃; particles; Alumina suspension; DPPC; Effective diameter; Zeta potential; PLA; ₂; Candida cylindracea; lipase

Preparation, magnetic characterization, and optical band gap of EuTiO₃ nanoparticles by T. Wei; H.P. Liu; Y.F. Chen; H.Y. Yan; J.-M. Liu (pp. 4505-4509).

▶ High quality EuTiO₃ polycrystalline nanoparticles were synthesized first time through the simple sol–gel method. ▶ Magnetic properties of EuTiO₃ nanoparticles were investigated and the G-AFM ordering was confirmed which shed light on the current debate on the magnetic properties of ETO nano-films. ▶ Optical band gap of 1.03eV for the as-prepared ETO nanoparticles was determined from the UV–visible absorption spectra.Perovskite-type polycrystalline EuTiO₃ (ETO) nanoparticles were synthesized using the simple sol–gel technique. We investigated the magnetic properties of the as-prepared ETO nanoparticles and revealed the G-AFM phase below the Néel temperature ( T_N). Furthermore, the transition from the G-AFM order to the FM order, induced by magnetic field, was also demonstrated. The optical band gap of 1.03eV for the as-prepared ETO nanoparticles was determined from the UV–visible absorption spectra.

Keywords: PACS; 81.07.−b; 78.67.−nEuTiO; ₃; Nanaoparticles; Magnetic properties

Synthesis of antimicrobial monophase silver-doped hydroxyapatite nanopowders for bone tissue engineering by Vojislav Stanić; Djordje Janaćković; Suzana Dimitrijević; Sladjana B. Tanasković; Miodrag Mitrić; Mirjana S. Pavlović; Aleksandra Krstić; Dragoljub Jovanović; Slavica Raičević (pp. 4510-4518).

▶ The neutralization method has been used for synthesis of silver-doped hydroxyapatite samples. ▶ Particles of silver-doped hydroxyapatite samples are of nano size and homogenous in composition. ▶ The silver-doped hydroxyapatite samples showed excellent antimicrobial activity. ▶ AFM showed that silver-doped sample causes morphological changes of microorganism cells. ▶ Silver-doped samples are nonhemolytic and seen promising for medical applications.Monophase silver-doped hydroxyapatite (Ag_xCa10−_x(PO₄)₆(OH)₂; 0.002≤ x≤0.04) nanoparticles were prepared using a neutralization method and investigated with respect to potential medical applications. This method consists of dissolving Ag₂O in solution of H₃PO₄, and the slow addition to suspension of Ca(OH)₂ was applied for the purpose of homogenous distribution of silver ions. Characterization studies from XRD, TEM and FTIR spectra showed that obtained crystals are monophase hydroxyapatites and that particles of all samples are of nano size, with average length of 70nm and about 15–25nm in diameter. Antimicrobial studies have demonstrated that all silver-doped hydroxyapatite samples exhibit excellent antimicrobial activity in vitro against the following pathogens: Staphylococcus aureus, Escherichia coli and Candida albicans. The hydroxyapatite sample with the highest content of silver has shown the highest antimicrobial activity; killed all cells of E. coli and brought to more than 99% reduction in viable counts of S. aureus and C. albicans. The atomic force microscopic studies illustrate that silver-doped hydroxyapatite sample causes considerable morphological changes of microorganism cells which might be the cause of cells’ death. Hemolysis ratios of the silver-doped hydroxyapatite samples were below 3%, indicating good blood compatibility and that are promising as biomaterials.

Keywords: Hydroxyapatite; Silver; Antimicrobial; Bone; Hemolysis; AFM

Controllable synthesis of spindle-like ZnO nanostructures by a simple low-temperature aqueous solution route by Hong-xia Lu; Yun-long Zhao; Xiu-jun Yu; De-liang Chen; Li-wei Zhang; Hong-liang Xu; Dao-yuan Yang; Hai-long Wang; Rui Zhang (pp. 4519-4523).

▶ Monodisperse spindle-like ZnO nanocrystals were successfully produced via a simple direct precipitation at relative low temperature without calcination. ▶ The lowest temperature synthesis of ZnO is 40°C. ▶ Rod-like, spindle-like and prism-like ZnO were obtained by adjusting temperatures, additives and Zn²⁺/OH⁻ ratios. ▶ The possible formation mechanism was also proposed based on the experimental results.Spindle-like ZnO nanostructures were successfully synthesized through direct precipitation of zinc acetate aqueous solution at 60°C. Phase structure, morphology and microstructure of the products were investigated by X-ray diffraction, TG-DTA, FTIR and field emission scanning electron microscopy (FESEM). Result showed that hexagonal wurtzite structure ZnO nanostructures with about 100nm in diameter and 100–200nm in length were obtained. HMTA acted as a soft template in the process and played an important role in the formation of spindle-like ZnO nanostructures. Meanwhile, different morphologies were also obtained by altering synthetic temperature, additional agents and the ratios of Zn²⁺/OH⁻. Possible mechanism for the variations of morphology with synthesis parameters was also discussed in this paper.

Keywords: ZnO; Spindle-like; Nanostructures; Direct precipitation

Preparation, characterization and electromagnetic properties of carbon nanotubes/Fe₃O₄ inorganic hybrid material by Yingqing Zhan; Rui Zhao; Yajie Lei; Fanbin Meng; Jiachun Zhong; Xiaobo Liu (pp. 4524-4528).

A novel carbon nanotubes/Fe₃O₄ inorganic hybrid material was prepared by in situ decomposition of the precursor ferric chloride crystal and CNTs in liquid ethylene glycol. XRD, SEM, TEM, EDS were used to characterize the as-prepared products. Results indicated that the monodispersed magnetite microspheres with the size of about 100nm were uniformly self-assembled along the surface of the carbon nanotubes. The formation of magnetite nanoparticles on CNTs was through an aggregation process of subparticles on the surface of CNTs. The ferromagnetic signature emerged with the saturated magnetization of 60.94emug⁻¹, and the coercive force of 148.59Oe at 300K. The measured relative complex permittivity indicated a high resistivity existence in the CNTs/Fe₃O₄ inorganic hybrid material. The magnetic loss was caused mainly by natural resonance, which is in good agreement with the Kittel equation results. The novel electromagnetic hybrid material is believed to have potential applications in the microwave absorbing performances.

Keywords: Magnetic materials; Carbon nanotubes; Magnetite; Inorganic hybrid material; Electromagnetic properties

Surfactant assisted synthesis of lamellar nanostructured LiFePO₄ at 388K by Chao Liu; Dongxia Ma; Xiujie Ji; Shanshan Zhao; Song Li (pp. 4529-4531).

Lamellar nanostructured lithium iron phosphate (Lα-LFP) was synthesized using anion surfactant sodium dodecyl sulphonate (SDS) as supermolecular template in water–ethanol media at 388K under self-generated pressure. FeSO₄, (NH₄)₂HPO₄ and LiOH were used as Fe, P and Li sources, respectively. The inorganic phase was analyzed by X-ray diffraction (XRD). The morphology and the lamellar nanostructure were observed by field emitting scanning electron microscopy (FESEM). The results showed that the synthesized Lα-LFP presents not only the ordered lamellar microstructure accumulated by 20–40-nm thick LFP layers, but also the consequent self-assembled blocky particles of 0.5–1μm. In contrast, template free LFP (TF-LFP) show a flake-shaped and mess-orientated microstructure. As a soft template, SDS played the roles of inducing the lamellar nanostructure, purifying the inorganic phase and decreasing the synthesis temperature.

Keywords: Surfactant; Template; Lamellar; Nanostructure; LiFePO; ₄

Preparation, characterization and heterogeneous catalytic activity of heteropolyanion/polyaniline nanocomposite by Hossein Salavati; Nahid Rasouli (pp. 4532-4538).

A heteropolyanion–polyaniline (Na₅[PV₂Mo₁₀O₄₀] PVMo/PANI) nanocomposite was prepared through two different method. In the one-step method, aniline was polymerized in the presence of PVMo, and PVMo was incorporated into the polymer matrix during the polymerization process. While, in the two-step method, PVMo was immobilized only on the surface of the ready-made PANI support. The nanocomposite was characterized by FT-IR, XRD, UV–vis, SEM and elemental analysis and used as an efficient heterogeneous catalyst for epoxidation of alkenes.Various linear and cyclic alkenes were oxidized into the corresponding epoxides in high yield in the presence of PVMo/PANI nanocomposite under reflux and ultrasonic irradiation conditions.

Keywords: Heteropolyanion; Epoxidation; Polyaniline; Immobilization; Nanocomposite

Field emission arrays fabricated utilizing conjugated ZnO quantum dot/carbon nanotube hybrid nanocomposite by Chaoxing Wu; Fushan Li; Yongai Zhang; Tailiang Guo; Bo Qu; Zhijian Chen (pp. 4539-4542).

In situ growth of ZnO quantum dots (QDs) on the surface of multiwalled carbon nanotube (MWCNTs) was realized via a mild solution-process method, and their application in field emission device was demonstrated. High resolution transmission electron microscopy observation revealed the conjugation between ZnO QDs and MWCNTs. Field emission arrays based on ZnO QD/MWCNT hybrid nanocomposite exhibited significantly improved luminance intensity and emitting dot density when compared with the MWCNT-only arrays. It is proposed that the introduction of the ZnO QDs on the sidewall of MWCNTs can enhance the tunnelling probability, and result in the improved field emission property for the hybrid emitters.

Keywords: PACS; 73.63.Kv; 73.63.FgZnO quantum dot; Multiwalled carbon nanotube; Hybrid nanocomposites; Field emission

Surface barrier analysis of semi-insulating and n⁺-type GaAs(001) following passivation with n-alkanethiol SAMs by Gregory M. Marshall; Farid Bensebaa; Jan J. Dubowski (pp. 4543-4546).

▶ Surface Fermi level of GaAs(001) passivated with n-alkanethiols determined by XPS. ▶ GaAs integrated Au pads provide surface equipotential binding energy calibration. ▶ Characteristics according to the Advanced Unified Defect Model were observed. ▶ Effective technique for surface Fermi level band-edge referencing applied to SAMs.The surface Fermi level of semi-insulating and n⁺-type GaAs(001) was determined before and after passivation with n-alkanethiol self-assembled monolayers (SAMs) by X-ray photoelectron spectroscopy. Fermi level positioning was achieved using Au calibration pads integrated directly onto the GaAs surface, prior to SAM deposition, in order to provide a surface equipotential binding energy reference. Fermi level pinning within 50meV and surface barrier characteristics according to the Advanced Unified Defect Model were observed. Our results demonstrate the effectiveness of the Au integration technique for the determination of band-edge referenced Fermi level positions and are relevant to an understanding of emerging technologies based on the molecular–semiconductor junction.

Keywords: Self-assembled monolayers; X-ray photoelectron spectroscopy; Surface Fermi level; GaAs

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Applied Surface Science (v.257, #9)

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Applied Surface Science (v.257, #9)