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Applied Surface Science (v.256, #10)

AES, LEED and PYS investigation of Au deposits on InSe/Si(111) substrate by B. Abidri; M. Ghaffour; A. Abdellaoui; M. Bouslama; S. Hiadsi; Y. Monteil (pp. 3007-3009).

Auger Electron Spectroscopy (AES), Low Energy Electron Diffraction (LEED) and Photoelectron Yield Spectroscopy (PYS) measurements have been used to monitor the interaction of gold (Au) deposits on InSe/Si(111) substrate. Au has been sequentially deposed under ultra-high vacuum onto 40Å-thick film of layered semiconductor InSe which is epitaxially grown by molecular beam epitaxy (MBE) on a Si(111)1×1-H substrate and kept at room temperature. Au coverage varies from 0.5 monolayer to 20 monolayers (ML) (in terms of InSe atomic surface plane: 1 ML=7.2 1014 at/cm²) which is corresponding to 1.30Å of Au-metal. The Au/InSe/Si(111) system was characterized as function of Au deposit, we noticed an interaction at room temperature starts as an apparent intercalation process until 5 ML. Beyond this dose Au islands begin to form on the sample surface without interaction with InSe substrate, thus the interface is far from to be a simple junction Au–InSe.

Keywords: AES; LEED; PYS; InSe; Interface; Au

Influence of conductive surface on adsorption behavior of ultrafiltration membrane by E. Salehi; S.S. Madaeni (pp. 3010-3017).

In this research the influence of conductivity on adsorptive behavior of PM30 ultrafiltration membrane was investigated using BSA solution as the feed. The conductive membrane was prepared from the originally nonconductive membrane by chemical polymerization of pyrrole as the conducting media on the membrane surface. Both Langmuir and Redlich–Peterson isotherms properly describe the quasi-equilibrium adsorption data which are produced using experimental results of flux and rejection. Higher capacity of protein adsorption was achieved using nonconductive in comparison with conductive membrane. Using nonconductive membrane, an excessive feasibility and spontaneity of BSA adsorption was observed based on the greater negative value of Gibbs free energy change (ΔG°) which is a criterion for spontaneity of adsorption. Determination of filtration mechanism was conducted for elucidation the dominant adsorption region within the membranes i.e. membrane surface or internal pores. The filtration mechanisms for BSA solution using nonconductive and conductive membranes were surface cake deposition and intermediate (partial) blocking, respectively. First-order-kinetic model versus second-order-kinetic model indicated a superior interpretation of adsorption kinetics for both membranes; however, the required time to reach to the equilibrium for nonconductive membrane was slightly higher. All the distinctions in adsorption behavior of the conductive membrane originate from the repulsive potential field appears on the surface of the membrane during preparation. This electrostatic field acts as a barrier against the passage of the negatively charged proteins. Moreover, the partial coverage of membrane surface and internal pores with poly(pyrrole) may reduce the quantity of the active adsorptive sites on the membrane surface and matrix or presumably deactivates a part of the sites.

Keywords: Adsorption; Conductive membrane; Isotherm; Filtration mechanism

Photo-irradiation effects on the surface morphology of poly( p-phenylene vinylene) films by Alexandre Marletta; M.L. Vega; C.A. Rodrigues; Y. Galvão Gobato; L.F. Costa; R.M. Faria (pp. 3018-3023).

In this work, we have studied the surface morphology of photo-irradiated poly( p-phenylene vinylene) (PPV) thin films by using atomic force microscopy (AFM). We have analyzed the first-order statistical parameters, the height distribution and the distance between selected peaks. The second-order statistical analysis was introduced calculating the auto-covariance function to determine the correlation length between heights. We have observed that the photo-irradiation process produces a surface topology more homogeneous and isotropic such as a normal surface. In addition, the polymer surface irradiation can be used as a new methodology to obtain materials optically modified.

Keywords: Atomic force microscopy; Surface morphology; Conjugated polymers; Statistical analysis

Effect of ECR-assisted microwave plasma nitriding treatment on the microstructure characteristics of FCVA deposited ultra-thin ta-C films for high-density magnetic storage applications by Gui-Gen Wang; Hua-Yu Zhang; Hong-Fei Zhou; Xu-Ping Kuang; Qi-Bao Wu; Hong-Bo Zuo; Jie-Cai Han; Hong-Tao Ma (pp. 3024-3030).

There are higher technical requirements for protecting layer of magnetic heads and disks used in future high-density storage fields. In this paper, ultra-thin (2nm thickness) tetrahedral amorphous carbon (ta-C) films were firstly prepared by filtered cathodic vacuum arc (FCVA) method, then a series of nitriding treatments were performed with nitrogen plasma generated using electron cyclotron resonance (ECR) microwave source. Here it highlighted the influence of nitrogen flow and applied substrate bias voltage on the structural characteristics of ta-C films during the plasma nitriding process. The chemical compositions, element depth distribution profiles, physical structures and bonding configurations of plasma-nitrided ta-C films were investigated by X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and UV–vis Raman spectroscopy. The experimental results show that the carbon nitride compounds (CN_x) are formed in nitrogenated ta-C films in which the N content and its depth distribution depends on bias voltage to large extent rather than N₂ flow. The N content of nitrogenated ta-C films can reach 16at.% for a substrate bias of −300V and a N₂ flow of 90sccm. With increasing nitrogen content, there is less G peak dispersion and more ordering of structure. Furthermore, appropriate nitriding treatment (substrate bias: −100V, N₂ flow: 150sccm) can greatly increase the fraction of sp³ and sp³C–N bonds, but the values begin to fall when the N content is above 9.8at.%. All these indicate that suitable ECR-assisted microwave plasma nitriding is a potential modification method to obtain ultra-thin ta-C films with higher sp³ and sp³C–N fractions for high-density magnetic storage applications.

Keywords: Plasma nitriding treatment; Electron cyclotron resonance; Tetrahedral amorphous carbon

Preparation of cross-linked copolymer microspheres 4VP/St and cobalt tetraphenylporphyrins supported on it by Ruixin Wang; Weizhou Jiao; Baojiao Gao (pp. 3031-3034).

The cross-linked microspheres 4VP/St made of 4-vinylpyridine (4VP) and styrene(St) were prepared with suspension copolymerization method using ethyl glycol dimethacylate (EGDMA) as cross-linker and polyvinyl alcohol (PVA) as disperser. The cobalt tetraphenylporphyrins (CoPs) were immobilized on 4VP/St microspheres via the axial coordination reaction between CoPs and the pyridine groups of 4VP/St microspheres, resulting in the functional microspheres CoP-4VP/St. The chemical structure of 4VP/St and CoP-4VP/St were characterized with infrared spectrum and their morphologies were observed with the scanning electron microscope. The experimental results show that via controlling the various reaction conditions of the suspension copolymerization, the 4VP/St microspheres with excellent sphericity and narrow particle diameter distribution can be gained. In addition, CoPs are successfully immobilized on 4VP/St microspheres by means of Co–N bonds, on which the immobilized content of CoPs goes up to 10.7–17.5μmol/g.

Keywords: 4-Vinylpyridine; Suspension polymerization; Cross-linked microsphere; Cobalt tetraphenylporphyrins; Immobilization

Growth process and mechanism of a multi-walled carbon nanotube nest deposited on a silicon nanoporous pillar array by Wei Fen Jiang; Lv Jian; Xiao Hui Yang; Xin Jian Li (pp. 3035-3039).

A large scale nest array of multi-walled carbon nanotubes (NACNTs) was grown on silicon nanoporous pillar array (Si-NPA) by thermal chemical vapor deposition. Through observing its macro/micromorphology and structure, ascertaining the catalyst component and its locations at different growth time by hiring field emission scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, and selected area electron diffraction, the growth process was deduced. Its thermal properties were also investigated by using a thermogravimetric analyzer. Our experiments demonstrated that the CNTs growth by means of root-growth mechanism at the initial growth stage, then a continuous growth process with its tip open is suggested, finally, a schematic growth model of NACNT/Si-NPA was presented.

Keywords: Nest array of multi-walled carbon nanotubes; Silicon nanoporous pillar array; Growth mechanism

Electrochemical and surface characterisation of gold nanoparticle decorated multi-walled carbon nanotubes by N. Alexeyeva; J. Kozlova; V. Sammelselg; P. Ritslaid; H. Mändar; K. Tammeveski (pp. 3040-3046).

A novel type of gold nanoparticle/multi-walled carbon nanotube (AuNP/MWCNT) composite electrodes is presented. The electrochemical reduction of oxygen on these hybrid electrodes was studied using the rotating disk electrode (RDE) method. The AuNP/MWCNT nanocomposites were prepared by sputter deposition of gold in argon atmosphere on MWCNTs followed by heat-treatment of the catalyst at different temperatures. High-resolution scanning electron microscopy (HR-SEM), glancing incidence angle X-ray powder diffraction (GIXRD) and small-angle X-ray scattering (SAXS) techniques were employed to characterise the surface structure and morphology of catalyst materials. Au nanoparticles with diameter around 20nm were dispersed at the tips and on the sidewalls of nanotubes. Electrochemical measurements were performed to demonstrate the electrocatalytic properties of the composite catalysts towards O₂ reduction in acid media. The successful preparation of AuNP/MWCNT nanocomposites by magnetron sputtering opens up the possibility of making an efficient dispersion of nanoparticles for electrocatalyst design.

Keywords: Oxygen reduction; Electrocatalysis; Gold nanoparticles; Multi-walled carbon nanotubes; Magnetron sputtering

Structural characterization and optical properties of UO₂ thin films by magnetron sputtering by Qiuyun Chen; Xinchun Lai; Bin Bai; Mingfu Chu (pp. 3047-3050).

Uranium dioxide films were deposited on Si (111) substrates by dc magnetron sputtering method at different sputtering parameters. The structure, morphology and chemical state of the films were studied by field emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and atomic force microscopy. Influences of film thickness on the microstructure and optical properties were investigated. Experimental results show that the film crystallites are preferentially oriented with the (111) planes. The average grain size increases with increasing film thickness. AFM images show that the root mean square roughness of the films is between 1.2nm and 2.1nm. Optical constants (refractive index, extinction coefficient) of the films in the wavelength range of 350–1000nm are obtained by ellipsometric spectroscopy. The result shows that the refractive index decreases with the increasing film thickness, while extinction coefficient increases with the film thickness.

Keywords: Uranium dioxide; Thin films; XRD; XPS; AFM; Ellipsometry

The interface structure and band alignment at alumina/Cu(Al) alloy interfaces—Influence of the crystallinity of alumina films by Michiko Yoshitake; Weijie Song; Jiří Libra; Karel Mašek; František Šutara; Vladimír Matolín; Kevin C. Prince (pp. 3051-3057).

Both epitaxial and amorphous ultra-thin alumina films were grown on a Cu-9at.%Al(111) substrate by selective oxidation of Al in the alloy in ultra high vacuum. The crystallinity of the alumina films was controlled by oxidation temperature. The photoelectron spectra of Al 2p, O 1s and valence band were measured in-situ during oxidation. The influence of the crystallinity on the interface structure between the alumina films and the substrate was discussed by analyzing the Al 2p spectra composed of multiple peaks. The energy difference between the Fermi level of the substrate and the valence band maximum of the alumina films (band offset) was derived from the valence band spectra. The energy band alignment at the interface between each of the two alumina films and the substrate was revealed by combining the binding energy values of the core levels with the band offset values. The influence of the alumina crystallinity on the band alignment was discussed.

Keywords: PACS; 73.40.Ns Metal–nonmetal contactsEpitaxial alumina film; Cu–Al alloy; Photoelectron spectroscopy; In-situ oxidation; Band alignment; Interface termination

Electric characterization of GaAs deposited on porous silicon by electrodeposition technique by M. Lajnef; R. Chtourou; H. Ezzaouia (pp. 3058-3062).

GaAs thin films were synthesized on porous Si substrate by the electrodeposition technique. The X-ray diffraction studies showed that the as-grown films were crystallised in mixed phase nature orthorhombic and cubic of GaAs. The GaAs film was then electrically characterized using current–voltage ( I– V) and capacitance–voltage ( C– V) techniques by the way of Al/GaAs Shottky junctions. The electric analysis allowed us to determine the n factor and the barrier height Ф_b0 parameters of Al/GaAs Schottky junctions. The ( C– V) characteristics were recorded at frequency signal 1MHz in order to identify the effect of the surface states on the behaviour of the capacitance of the device.

Keywords: Gallium arsenide; Thin films; Electrodeposition; Electric properties

Biocidal action of ozone-treated polystyrene surfaces on vegetative and sporulated bacteria by Ahlem Mahfoudh; Jean Barbeau; Michel Moisan; Annie Leduc; Jacynthe Séguin (pp. 3063-3072).

Surfaces of materials can be modified to ensure specific interaction features with microorganisms. The current work discloses biocidal properties of polystyrene (PS) Petri-dish surfaces that have been exposed to a dry gaseous-ozone flow. Such treated PS surfaces are able to inactivate various species of vegetative and sporulated bacteria on a relatively short contact time. Denaturation of proteins seems likely based on a significant loss of enzymatic activity of the lysozyme protein. Characterization of these surfaces by atomic-force microscopy (AFM), Fourier-transform infra-red (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) reveals specific structural and chemical modifications as compared to untreated PS. Persistence of the biocidal properties of these treated surfaces is observed. This ozone-induced process is technically simple to achieve and does not require active precursors as in grafting.

Keywords: Surface treatment; Antibacterial; Sporicide; Bioactivity; Polystyrene; Ozone

Effect of heat treatment on bioactivity of anodic titania films by Ying Zhao; Tianying Xiong; Wenhai Huang (pp. 3073-3076).

Anodic oxidation could be employed to produce crystalline titania films on Ti6Al4V surfaces for inducing apatite formation in simulated body fluid (SBF). In this work, the effect of further heat treatment on the bioactivity of anodic titania films was researched. The surface constitution, morphology, crystal structure and apatite-forming ability of titania films were characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicated the apatite formation on the Ti6Al4V surfaces could be attributed to abundance of Ti–OH groups formed via anodic oxidation, but subsequent heat treatment would decrease the amount of surface hydroxyl (OH) groups and result in the loss of the apatite-forming ability.

Keywords: Heat treatment; OH; Anodic oxidation; Bioactivity

Reactive Pulsed Laser Deposition of titanium nitride thin film: Optimization of process parameters using Secondary Ion Mass Spectrometry by R. Krishnan; Tom Mathews; A.K. Balamurugan; S. Dash; A.K. Tyagi; Baldev Raj; Vikram Jayaram (pp. 3077-3080).

Reactive Pulsed Laser Deposition is a single step process wherein the ablated elemental metal reacts with a low pressure ambient gas to form a compound. We report here a Secondary Ion Mass Spectrometry based analytical methodology to conduct minimum number of experiments to arrive at optimal process parameters to obtain high quality TiN thin film. Quality of these films was confirmed by electron microscopic analysis. This methodology can be extended for optimization of other process parameters and materials.

Keywords: TiN; SIMS; Thin films; Reactive Pulsed Laser Deposition; Multilayer

Filtering performance improvement in V-doped ZnO/diamond surface acoustic wave filters by J.T. Luo; F. Zeng; F. Pan; H.F. Li; J.B. Niu; R. Jia; M. Liu (pp. 3081-3085).

High-frequency surface acoustic wave (SAW) filters using undoped and V-doped ZnO films were fabricated on diamond. Compared with their counterparts, the SAW filters using V-doped ZnO films have higher electromechanical coupling coefficient of ∼2.9% and lower insertion loss. The filtering performance improvement is considered to be due to the ferroelectricity in V-doped ZnO films and the resultant high piezoresponse (∼110pm/V), which is one order of magnitude larger than that of undoped ZnO films. In addition, more perfect (002) preferred orientation, better uniform grains and smoother surface of V-doped ZnO films also contribute to the filtering performance improvement.

Keywords: ZnO; Vanadium; Piezoelectric; Surface acoustic wave; Filter; Diamond; Piezoresponse

In vitro investigation of anodization and CaP deposited titanium surface using MG63 osteoblast-like cells by J.M. Lee; J.I. Lee; Y.J. Lim (pp. 3086-3092).

The aim of the present study was to investigate surface characteristics in four different titanium surfaces (AN: anodized at 270V; AN-CaP: anodic oxidation and CaP deposited; SLA: sandblasted and acid etched; MA: machined) and to evaluate biological behaviors such as cell adhesion, cell proliferation, cytoskeletal organization, and osteogenic protein expression of MG63 osteoblast-like cells at the early stage. Surface analysis was performed using scanning electron microscopy, thin-film X-ray diffractometry, and a confocal laser scanning microscope. In order to evaluate cellular responses, MG63 osteoblast-like cells were used. The cell viability was evaluated by MTT assay. Immunofluorescent analyses of actin, type I collagen, osteonectin and osteocalcin were performed. The anodized and CaP deposited specimen showed homogeneously distributed CaP particles around micropores and exhibited anatase type oxides, titanium, and HA crystalline structures. This experiment suggests that CaP particles on the anodic oxidation surface affect cellular attachment and spreading. When designing an in vitro biological study for CaP coated titanium, it must be taken into account that preincubation in medium prior to cell seeding and the cell culture medium may affect the CaP coatings. All these observations illustrate the importance of the experimental conditions and the physicochemical parameters of the CaP coating.It is considered that further evaluations such as long-term in vitro cellular assays and in vivo experiments should be necessary to figure out the effect of CaP deposition to biological responses.

Keywords: CaP electron beam deposition; Surface characteristics; MG63 osteoblast-like cells; Immunofluorescent analyses; Osteogenic protein expression

Re-examination of characteristic FTIR spectrum of secondary layer in bilayer oleic acid-coated Fe₃O₄ nanoparticles by Kun Yang; Huabei Peng; Yuhua Wen; Ning Li (pp. 3093-3097).

Bilayer oleic acid-coated Fe₃O₄ nanoparticles can be applied in more areas than single layer oleic acid-coated ones because they can be well dispersed not only in nonpolar carrier liquids but also in polar carrier liquids, while the single layer oleic acid-coated ones can be dispersed only in nonpolar carrier liquids. Therefore, it is of significance to characterize the surface structure of bilayer and single layer oleic acid-coated Fe₃O₄ nanoparticles. However, there existed a discrepancy in the characteristic FTIR spectrum of the secondary layer in bilayer oleic acid-coated Fe₃O₄ nanoparticles. The goal of this paper was to resolve the discrepancy through using FTIR and TGA together with dispersibility to characterize the surface structure of bilayer and single layer oleic acid-coated Fe₃O₄ nanoparticles. The results showed that the band at 1710cm⁻¹ was the characteristic band of the secondary layer in bilayer oleic acid-coated Fe₃O₄ nanoparticles. It can be used to distinguish whether the oleic acid-coated Fe₃O₄ nanoparticles are bilayer or not.

Keywords: FTIR spectrum; Fe; ₃; O; ₄; nanoparticles; Oleic acid; Bilayer; Secondary layer

Ni–WC composite coatings by carburizing electrodeposited amorphous and nanocrystalline Ni–W alloys by Saadia Latif; Mazhar Mehmood; Jamil Ahmad; Muhammad Aslam; Maqsood Ahmed; Zhi-dong Zhang (pp. 3098-3106).

In situ formation of tungsten carbide in the matrix of FCC nickel has been achieved by carburizing of the electrodeposited Ni–W alloy coatings. The size of the carbide particles ranges between 100 and 500nm. The carbide phase is also present in the form of very small precipitates inside the nickel grains. The size of such precipitates is between 10 and 40nm. The carburizing environment was created by introducing a flowing mixture of vaporized 95.5% alcohol (0.25ml/min, liquid) and argon (0.5L/min, gas) into the carburizing furnace. Supersaturated nature of electrodeposited amorphous and nanocrystalline alloys, in addition to high diffusivity, have been attributed for the formation of carbide phase in the deposits at a temperature range of 700–850°C. The carbide–metal interface is clean and the composite coatings are compact. Hardness values up to about 1100KHN are achieved. Hardness increases with tungsten content and carburizing temperature.

Keywords: Amorphous and nanocrystalline alloys; Coatings; Composites; Metal–matrix composites

Effect of ZnO on phase emergence, microstructure and surface modifications of calcium phosphosilicate glass/glass–ceramics having iron oxide by K. Sharma; A. Dixit; S. Bhattacharya; Jagannath; M.N. Deo; G.P. Kothiyal (pp. 3107-3115).

The effect of ZnO on phase emergence and microstructure properties of glass and glass–ceramics with composition 25SiO₂–50CaO–15P₂O₅–(10− x)Fe₂O₃– xZnO (where x=0, 2, 5, 7mol%) has been studied. They have been characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Surface modifications of these glass–ceramics in simulated body fluid have been studied using Fourier transform infrared reflection spectroscopy (FTIR), XPS and SEM. Results have shown a decrease in the fraction of non-bridging oxygen with increase in zinc oxide content. Emergence of crystalline phases in glass–ceramics at different heat treatment temperatures was studied using XRD. When glass is heat treated at 800°C calcium phosphate, hematite and magnetite are developed as major phases in the glass–ceramics samples with ZnO up to 5mol%. In addition to these, calcium silicate (Ca₃Si₂O₇) phase is also observed when glass is heat treated at 1000°C. The microstructure of the glass–ceramics heat treated at 800°C exhibits the formation of nano-size (40–50nm) grains. On heat treatment at 1000°C crystallites grow to above 50nm size and more than one phase are observed in the microstructure. The formation of thin flake-like structure with coarse particles is observed at high zinc oxide concentration ( x=7mol%). In vitro studies have shown the surface modifications and formation of Ca–P-rich layer on the glass–ceramics when immersed in simulated body fluids (SBF) for different durations. The bioactive response was found to depend on ZnO content.

Keywords: Glass ceramic; XPS; Magnetite; SEM; Simulated body fluid (SBF)

Enhanced photocatalytic activity of silver metallized TiO₂ particles in the degradation of an azo dye methyl orange: Characterization and activity at different pH values by L. Gomathi Devi; K. Mohan Reddy (pp. 3116-3121).

The photocatalytic activity of silver deposited Degussa P25 titanium dioxide (Ag-DP25) in the photodegradation of methyl orange (MO) was investigated. The photocatalysts were characterized using PXRD, SEM, EDX, FTIR and UV–vis spectrophotometer. The obtained results show that the silver (Ag⁰) deposited TiO₂ exhibited visible light plasmon absorption band. The degradation experiment reveals that the catalytic property of Ag-DP25 in the degradation of MO is more efficient than that of commercially available Degussa P25 TiO₂ (DP25) samples. The improvement of Ag-DP25 catalyst efficiency strongly depends on the content of silver (Ag) deposits. The present study shows that the degradation process is dominated by Ag–TiO₂ photocatalytic system, complying with pseudo-first order rate law. The higher rate of photodegradation observed on Ag-DP25 at pH 6.6 can be correlated to the ratios of the concentrations of the ionized to the neutral dye molecules and also to the higher concentration of hydroxylated surface, which are able to effectively scavenge photogenerated valence band holes. Accumulation of the holes in the semiconductor particles increases the probability of formation of excited oxygen atom which is a reactive species readily oxidizing the organic dye molecule. The reduction of pH during the course of the reaction is attributed to the complete mineralization of the dye.

Keywords: Silver deposited titanium dioxide; Methyl orange; Photocatalytic degradation

X-ray diffraction studies on crystallite size evolution of CoFe₂O₄ nanoparticles prepared using mechanical alloying and sintering by Samaila Bawa Waje; Mansor Hashim; Wan Daud Wan Yusoff; Zulkifly Abbas (pp. 3122-3127).

Nanosized cobalt ferrite spinel particles have been prepared by using mechanically alloyed nanoparticles. The effects of various preparation parameters on the crystallite size of cobalt ferrite which includes milling time; ball-to powder weight ratio (BPR) and sintering temperature, were studied using X-ray diffractometer (XRD). Scherrer's equation was used to study the crystallite size evolution of the as-prepared materials. The results of the as-milled sample revealed that both milling time and BPR plays a role in determining the crystallite size of the milled powder. However, where sintering is involved, the sintering temperature results in grain growth, and thus plays a dominant role in determining the final crystallite size of the samples sintered at higher temperature (above 900°C). From the vibrating-sample magnetometer (VSM) measurement it was observed that the coercivity of the as-milled samples without sintering is almost negligible, which is a type characteristic of superparamagnetic material. However, for the sintered samples, the saturation increases while coercivity decreases with increases sintering temperature.

Keywords: Crystallite size; Sintering temperature; X-ray diffraction; Nanoparticles

A simple model for the growth kinetics of Fe₂B iron boride on pure iron substrate by M. Keddam; M. Ortiz-Domínguez; I. Campos-Silva; J. Martínez-Trinidad (pp. 3128-3132).

The present work evaluates the growth kinetics of Fe₂B iron boride forming on iron substrate by means of a diffusion model in the temperature range 1223–1323K. The model takes into account the effect of the boride incubation time during the formation of Fe₂B phase. The parabolic growth constant at the (Fe₂B/Fe) interface and the mass gain generated by this treatment were estimated. Likewise a simple relationship was proposed to describe the variation of the parabolic growth constant as a function of both the temperature and the boron content in the Fe₂B phase. Furthermore, the simulation results show a good agreement with our experimental results.

Keywords: Paste-boriding; Incubation time; Growth kinetics; Diffusion model; Parabolic growth constant

Substrate temperature influenced structural, electrical and optical properties of dc magnetron sputtered MoO₃ films by S. Uthanna; V. Nirupama; J.F. Pierson (pp. 3133-3137).

Molybdenum oxide (MoO₃) films were deposited on glass and (111) silicon substrates by sputtering of metallic molybdenum target in an oxygen partial pressure of 2×10⁻⁴mbar and different substrate temperatures in the range 303–623K using dc magnetron sputtering technique. X-ray photoelectron spectrum of the films formed at 303K showed asymmetric Mo 3d_5/2 and Mo 3d_3/2 peaks due to the presence of mixed oxidation states of Mo⁵⁺ and Mo⁶⁺ while those deposited at substrate temperatures ≥473K were in Mo⁶⁺ oxidation state of MoO₃. The films formed at substrate temperatures ≥473K were polycrystalline in nature with orthorhombic α-phase MoO₃. Fourier transform infrared spectra of the films showed an absorption band at 1000cm⁻¹ correspond to the stretching vibration of MoO, the characteristic of the α-MoO₃ phase. The electrical resistivity increased from 3.3×10³ to 8.3×10⁴Ωcm with the increase of substrate temperature from 303 to 473K respectively due to improvement in the crystallinity of the films. Optical band gap of the films increased from 3.03 to 3.22eV with the increase of substrate temperature from 303 to 523K.

Keywords: PACS; 64.70 F; 81.15 Cd; 68.35 B; 81.40 TvMolybdenum oxide; Reactive sputtering; Structure; Electrical and optical properties

Photoluminescence and charge storage characteristics of silica nanocrystals: The role of stress-induced interface defects by C.L. Yuan; W. Lei (pp. 3138-3141).

SiO₂ nanocrystals embedded in Lu₂O₃ thin film were fabricated using pulsed-laser deposition method. Two dimensional finite element calculations clearly reveal that SiO₂ nanocrystals certainly experienced great compressive stress in Lu₂O₃ thin film. This may lead to a great deal of stress-induced defects at the interface of SiO₂ nanocrystals embedded in Lu₂O₃ thin film and thus induced the observed photoluminescence peak and charge storage properties. The findings presented here indicate that the matrix environment of the nanocrystals plays a significant role in determining their electrical and optical properties.

Keywords: PACS; 61.46.Hk; 78.55.−m; 77.55.+fNanocrystals; Stress; Photoluminescence; Metal-insulator-semiconductor devices

Ultra smooth NiO thin films on flexible plastic (PET) substrate at room temperature by RF magnetron sputtering and effect of oxygen partial pressure on their properties by S. Nandy; S. Goswami; K.K. Chattopadhyay (pp. 3142-3147).

Transparent p-type nickel oxide thin films were grown on polyethylene terephthalate (PET) and glass substrates by RF magnetron sputtering technique in argon+oxygen atmosphere with different oxygen partial pressures at room temperature. The morphology of the NiO thin films grown on PET and glass substrates was studied by atomic force microscope. The rms surface roughnesses of the films were in the range 0.63–0.65nm. These ultra smooth nanocrystalline NiO thin films are useful for many applications. High resolution transmission electron microscopic studies revealed that the grains of NiO films on the highly flexible PET substrate were purely crystalline and spherical in shape with diameters 8–10nm. XRD analysis also supported these results. NiO films grown on the PET substrates were found to have better crystalline quality with fewer defects than those on the glass substrates. The sheet resistances of the NiO films deposited on PET and glass substrates were not much different; having values 5.1 and 5.3kΩ/□ and decreased to 3.05, 3.1kΩ/□ respectively with increasing oxygen partial pressure. The thicknesses of the films on both substrates were ∼700nm. It was also noted that further increase in oxygen partial pressure caused increase in resistivity due to formation of defects in NiO.

Keywords: NiO; Transparent conducting oxide; RF sputtering; PET; HRTEM

Construction of europium hexacyanoferrate film and its electrocatalytic activity to tyrosine determination by Yingju Liu; Zehao Yang; Yuanwen Zhong; Jiayu Yu (pp. 3148-3154).

In this work, a rare-earth metal hexacyanoferrate film, europium hexacyanoferrate film, was electrodeposited on the graphite electrode. For the first time, XPS was employed to confirm that the valences of Fe in the film were changed during the electrochemical reaction, and proper electrochemical equations were proposed. Then, the electrochemical characterization of the film, such as film thickness, the number of electrons, and the apparent heterogeneous electron transfer rate constant, was deduced from cyclic voltammograms. Furthermore, this film was found to exhibit an electrocatalytic activity to the oxidation of tyrosine. The experimental conditions, pH value and the applied potential, are investigated in detail. At the optimal conditions, the electrocatalytic response is a linear relationship with the concentration of tyrosine in the range of 10μM and 0.6mM, with a detection limit of about 8μM.

Keywords: Europium hexacyanoferrate; Tyrosine; Electrocatalysis

X-ray photoelectron and X-ray absorption spectroscopic study on β-FeSi₂ thin films fabricated by ion beam sputter deposition by F. Esaka; H. Yamamoto; N. Matsubayashi; Y. Yamada; M. Sasase; K. Yamaguchi; S. Shamoto; M. Magara; T. Kimura (pp. 3155-3159).

A combination of X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) using synchrotron radiation is applied to clarify surface chemical states of β-FeSi₂ films fabricated by an ion-beam sputtering deposition method. The differences in the chemical states of the films fabricated at substrate temperatures of 873, 973 and 1173K are investigated. For the film fabricated at 873K, Si 2p XPS spectra indicate the formation of a relatively thicker SiO₂ layer. In addition, Fe L-edge XAS spectra exhibit the formation of FeSi2−_X by preferential oxidation of Si or the presence of unreacted Fe. The results for the film fabricated at 1173K imply the existence of FeSi₂ with α and ɛ phases. In contrast, the results for the film fabricated at 973K indicate the formation of relatively homogeneous β-FeSi₂. These imply that the relatively excellent crystal property of the film fabricated at 973K is due to the formation of homogeneous β-FeSi₂. As a conclusion, the combination of XPS and XAS using synchrotron radiation is a powerful tool to elucidate the surface chemical states of thin films.

Keywords: XPS; XAS; Iron silicide; Surface

Preparation and characterization of L-Leucine-modified amphiprotic bifunctional mesoporous SBA-15 molecular sieve as a drug carrier for ribavirin by Zhigang Xu; Yongsheng Ji; Min Guan; Huayu Huang; Chuande Zhao; Haixia Zhang (pp. 3160-3165).

In this study, an amphiphilic bifunctional mesoporous SBA-15 material (AMPBIF-SBA-15) was synthesized through post-synthesis method as a drug carrier. Ribavirin was selected as the model drug and whose release from both unmodified and functionalized SBA-15 was evaluated in four media solutions with different pH or ionic strength. The release process indicated that AMPBIF-SBA-15 was a pH-sensitive drug carrier, which showed a phased low-release effect to ribavirin in the simulated body fluid (PBS, pH 7.4) solution. The materials were further characterized by Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption–desorption measurements and elemental analysis. This study provided a novel drug carrier for ribavirin to improve curative effect of ribavirin.

Keywords: Mesoporous SBA-15 silica molecular sieves; Amphiprotic groups; Drug carrier; Controlled release; Ribavirin

Laser surface micro-drilling and texturing of metals for improvement of adhesion joint strength by H.C. Man; K.Y. Chiu; X. Guo (pp. 3166-3169).

The surface texture of a metallic surface plays an important role in its adhesion strength in an adhesion joint. The same applies to medical implants in regard to fixation and tissue integration. To achieve a strong adhesion for a structural joint or a bone tissue fixation for medical implants, the effects of laser drilled micro-holes at the surface of the metals were investigated. The effect of the number of holes per unit area on the adhesion strength of the adhesion joint was evaluated and the results showed that the number of holes per unit area on the adherend surface logarithmically correlated with the bonding strength. Other holes geometries are suggested for enhanced adhesion and bone tissue fixation.

Keywords: Laser drilling; Adhesion; Implants; Bone fixation; Mechanical locking

Synthesis and characterization of TiO₂ thin films coated on metal substrate by Peng Sun; Haibo Liu; Haibin Yang; Wuyou Fu; Shikai Liu; Minghui Li; Yongming Sui; Yanyan Zhang; Yixing Li (pp. 3170-3173).

Nanostructured titanium dioxide (TiO₂) thin films have been prepared on metal substrates using a facile layer-by-layer dip-coating method. The phase structure and morphologies of preparing samples were characterized by means of X-ray powder diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The results confirm that films are highly crystalline anatase TiO₂ and free from other phases of titanium dioxide. Scanning electron microscopy (SEM) shows that the nanoparticles are sintered together to form a compact structure. The electrical properties of samples were investigated by cutternt–voltage analysis, the result indicates that a rectifying junction between the nanocrystalline TiO₂ film and metal substrate was formed. The photoelectrochemical characteristics recorded under 1.5AM illumination indicates that the as-fabricated thin film electrode possesses the highest photocurrent density at 450°C, which is 1.75mA/cm² at 0V vs. Ag/AgCl.

Keywords: Sol–gel preparation; Nanomaterials; Photoelectrochemical properties

Substrate temperature dependence of the properties of scandium-doped ZnO films deposited by sputtering by Miao Cun-Xing; Zhao Zhan-Xia; Zhao Lei; Ma Zhong-Quan (pp. 3174-3177).

Structural and optical properties of Sc-doped ZnO films grown by RF magnetron sputtering at different substrate temperatures were investigated. All the ZnO:Sc films are polycrystalline with the hexagonal wurtzite structure. X-ray diffraction patterns of the films showed that the doped-films have (002) as preferred orientation when the deposition temperature was increased from 250°C to 300°C. All the films are in a state of compressive stress, whereas the stress decreases gradually with increasing substrate temperature. The average transmittance of these films was above 90% in the wavelength range from 400nm to 800nm. The optical band gap of these films was determined. The optical constants of these films were determined using transmittance and reflectance spectra.

Keywords: Sputtering; SZO films; Stress; Optical properties

Atmospheric pressure chemical vapour deposition of NbSe₂–TiSe₂ composite thin films by Nicolas D. Boscher; Claire J. Carmalt; Ivan P. Parkin (pp. 3178-3182).

Atmospheric pressure chemical vapour deposition of titanium tetrachloride and niobium pentachloride with di- tert-butyl selenide at 550°C was investigated for different precursors’ flow rates. Scanning electron microscopy of the films showed that they were composed of two different kinds of plate-like crystallites. Point wavelength dispersive X-ray (WDX) analyses of the crystallites revealed that they either had the NbSe₂ or the TiSe₂ composition. The presence of the two phases was confirmed by X-ray diffraction (XRD) and the calculated cell parameters indicate that niobium or titanium was not incorporated into each others’ lattice. WDX and XRD analyses highlighted how the NbSe₂:TiSe₂ ratio in the composite films could be controlled by precursor flow rate.

Keywords: CVD; Atmospheric pressure; Metal selenide; Composite film

Preparation of highly ordered mesoporous AlSBA-15–SO₃H hybrid material for the catalytic synthesis of chalcone under solvent-free condition by Wei Li; Kejin Xu; Leilei Xu; Jianglei Hu; Fengyan Ma; Yihang Guo (pp. 3183-3190).

Single-step preparation of SBA-15 materials functionalized with both propylsulfonic acid groups and aluminum species (AlSBA-15–SO₃H) was carried out by hydrothermal treatment of a mixture of aluminum isopropoxide, 3-mercaptopropyltriethoxysilane, tetraethoxysilane, and triblock copolymer surfactant. At Si/Al molar ratio of 11–96, the materials exhibited well-ordered hexagonally arranged mesopores with pore diameter of ca. 9nm, BET surface area of 546.9–666.0m²g⁻¹, and pore volume of 0.82–1.03cm³g⁻¹. As-prepared AlSBA-15–SO₃H was successfully used in the Claisen–Schmidt condensation reaction of benzaldehyde with acetophenone to produce chalcone under solvent-free condition, and the influence of the reaction parameters including temperatures, molar ratios of BZD to APN, and aluminum loadings were considered during the chalcone synthesis procedure. It showed that AlSBA-15–SO₃H exhibited significantly high catalytic activity and selectivity, outperforming the reference catalysts such as sulfuric acid, ZSM-5, and acidic MCM-49. In addition, the catalytic stability and regeneration of AlSBA-15–SO₃H was studied.

Keywords: SBA-15; Hybrid catalyst; Claisen–Schmidt condensation; Chalcone; Solvent-free

Formation process of a strong water-repellent alumina surface by the sol–gel method by Libang Feng; Hui Li; Yongfeng Song; Yulong Wang (pp. 3191-3196).

A novel strong water-repellent alumina thin film is fabricated by chemically adsorbing stearic acid (STA) layer onto the porous and roughened aluminum film coated with polyethyleneimine (PEI). The formation process and the structure of the strong water-repellent alumina film are investigated by means of contact angle measurement and atomic force microscope (AFM). Results show that the water contact angles for the alumina films increase with the increase of the immersion time in the boiling water, and meanwhile, the roughness of the alumina films increases with the dissolution of the boehmite in the boiling water. Finally, the strong water-repellent film with a high water contact angle of 139.1° is obtained when the alumina films have distinct roughened morphology with some papillary peaks and porous structure. Moreover, both the roughened structure and the hydrophobic materials of the STA endow the alumina films with the strong water-repellence.

Keywords: Alumina; Strong water-repellence; Sol–gel; Contact angle; Morphology

The melting behaviors of the Nb(110) nanofilm: a molecular dynamics study by Xi-Yuan Yang; Dan Wu (pp. 3197-3203).

By using molecular dynamics (MD) and the modified analytic embedded atom method (MAEAM), we have studied the melting point, the melting mechanism and the correspondingly dynamical behaviors of a Nb(110) nanofilm. Firstly, in accordance to the MD time dependence of the potential energy, the melting point of this nanofilm has been roughly estimated. Then, the melting mechanism of the nanofilm have been analyzed in detail with the application of the structure factor. The results clearly indicate that the melting transition of the 8th, 9th, and 10th atomic layer of the nanofilm has been characterized by the exponential, polynomial and linear sequence respectively when the thickness of the quasiliquid film attains to about 1.3nm. Thirdly, the dynamical behaviors of the nanofilm melting, such as the melting front propagation velocity and the kinetic coefficient, which have also been analyzed, demonstrate that the melting front propagation velocity has linearly increased with the incremental temperature and the evaluated kinetic coefficient has approximately equaled 1.43 m/( sK). Finally, by extrapolating the melting front propagation velocity to zero, we can accurately deduce the melting point of the Nb(110) nanofilm to 2568.3K, which is much lower than the counterpart (2740K) of the bulk niobium.

Keywords: PACS; 64.70.dj; 68.35.Md; 61.46.−w; 31.15.xvMelting mechanisms; Dynamical behaviors; Melting point; The Nb(1; 1; 0) nanofilm; Atomic simulation

Application of XPS spectral subtraction and multivariate analysis for the characterization of Ar⁺ ion beam modified polyimide surfaces by Svitlana Pylypenko; Kateryna Artyushkova; Julia E. Fulghum (pp. 3204-3210).

This paper presents results of a detailed X-ray photoelectron spectroscopy (XPS) characterization of complex changes at a polyimide surface resulting from Ar⁺ ion beam modification. The changes in chemical composition in the surface layer lead to formation of a layer that can act as an alignment layer for liquid crystals. The goal of this paper is to report on the result of a combination of spectral subtraction and multivariate analysis for analysis of XPS spectra. Principal component analysis (PCA), applied to curve-fitting results of difference spectra and multivariate curve resolution (MCR), applied to raw spectra, provided consistent results, and allowed for extraction of chemical anisotropy, defining factor in the ion beam (IB) alignment mechanism. This study demonstrated that more detailed chemical information about complex systems can be obtained through application of multivariate analysis to XPS spectra and curve-fits. Further, this approach can be effectively used in the characterization of various complex materials to link chemical structure to their properties.

Keywords: Ion beam alignment; Polyimide; Anisotropy; XPS; Spectral subtraction; PCA; MCR–ALS

Microstructure and tribological behavior of pulsed laser deposited a-CN_x films by X.H. Zheng; J.P. Tu; R.G. Song (pp. 3211-3215).

The a-CN_x films were deposited onto high-speed steel substrate by pulsed laser deposition at different nitrogen pressures. The tribological properties of the films in humid air and in vacuum were investigated using a ball-on-disk tribometer under various loads. The composition, microstructure and morphology of the films, wear tracks and paired balls were characterized by energy dispersive X-ray analysis (EDXA), X-ray photoelectron spectrum (XPS), Raman spectroscopy and scanning electron microscopy (SEM). With increasing the deposition pressure, the fraction of sp³ C bond reduces, the fraction of trapped nitrogen increases and the friction coefficient of the films declines both in humid air and vacuum. The friction coefficient of a-CN_x film decreases with increasing normal load. The tribological performances of the films in humid air are better than those of in vacuum. A transferred graphite-like tribo-layer is observed from a-CN_x film to the paired ball for both environments.

Keywords: Carbon-based coatings; Wear testing; Amorphous carbon nitride; Pulsed laser deposition

Cu–Zn–Al mixed metal oxides derived from hydroxycarbonate precursors for H₂S removal at low temperature by Dahao Jiang; Lianghu Su; Lei Ma; Nan Yao; Xiaoliang Xu; Haodong Tang; Xiaonian Li (pp. 3216-3223).

One series of Cu–Zn and two series of Cu–Zn–Al hydroxycarbonate precursors with varying metal molar ratios were prepared via co-precipitation or multi-precipitation method, and the mixed metal oxides obtained by calcination of the precursor materials were used as adsorbents for H₂S removal in the range of 25–100°C. The results of H₂S adsorption tests showed that these mixed oxides, especially two series of Cu–Zn–Al mixed metal oxides exhibited markedly high breakthrough sulfur capacities (ranging from 4.4 to 25.7gS/100g-sorbent with increase of Cu/Zn molar ratio) at 40°C. Incorporation Cu and/or Al decreased the mean crystalline sizes of ZnO and CuO species in the Cu–Zn and Cu–Zn–Al mixed metal oxide adsorbents by decreasing of mean crystalline sizes of hydroxycarbanate phases mainly including hydrozincite, aurichalcite and malachite, segregation of Al phase, etc. Higher breakthrough sulfur capacity of each adsorbent in two ternary series than that of the corresponding adsorbent in binary series should be ascribed to the enhancement of the dispersion of ZnO and/or CuO species with incorporation of aluminum, thereby increasing the overall rate of reaction between the adsorbent and H₂S by reducing the thickness of potential sulfide shell on the outer layer of the oxide crystalline grains and increasing the area of the interface for the exchange of HS⁻/S²⁻ and O²⁻. For each series of adsorbents, the breakthrough sulfur capacity increased with the increase of Cu/Zn molar ratio regardless of changes of the dispersion of CuO and/or ZnO. This phenomenon might be mainly attributed to faster rate of the lattice diffusion of HS⁻, S²⁻ and O²⁻ or exchange of HS⁻/S²⁻ and O²⁻ during the sulfidation of CuO than that during the sulfidation of ZnO due to less rearrangement of the anion lattice.

Keywords: H; ₂; S removal; Low temperature; Hydroxycarbonate precursors; Cu–Zn–Al mixed metal oxides

Synthesis and characterization of Ag/BiVO₄ composite photocatalyst by Aiping Zhang; Jinzhi Zhang (pp. 3224-3227).

Ag/BiVO₄ composite photocatalysts were hydrothermal synthesized and characterized by XRD, SEM, XPS and DRS techniques. Their photocatalytic activities were determined by oxidative decomposition of methyl orange in aqueous solution under visible light irradiation. It revealed that the doped Ag species greatly improved the visible light absorption abilities and morphologies of the composites, and thus lead to enhanced photocatalytic activities compared with that of the pure BiVO₄.

Keywords: Visible light; Ag/BiVO; ₄; composite; Photocatalysis

Adsorptive removal of anionic dyes by modified nanoporous silica SBA-3 by Mansoor Anbia; Saba Asl Hariri; S.N. Ashrafizadeh (pp. 3228-3233).

Batch sorption experiments were carried out to remove dyes, methyl orange (MO), orange G (OG) and brilliant red X-3B (X-3B), from their aqueous solutions using a mesoporous silica SBA-3 as an adsorbent. The effect of surfactant template in SBA-3 on the removal of OG, MO and X-3B was investigated. Experiments were carried out to investigate the influence of contact time, initial concentration, pH, and adsorbent dosage on the adsorption performance. The adsorption results of anionic dyes on the uncalcined SBA-3 (noted as SBA-3) were compared with those of the calcined SBA-3 (noted as C-SBA-3). The uncalcined SBA-3 adsorbent has a large adsorption capacity and a strong affinity for the anionic dyes. Langmuir, Freundlich and Temkin isotherms were employed to model the experimental results, from which the Freundlich isotherm exhibited the most appropriate to predict the same. Freundlich isotherm exhibited the most appropriate to predict the experimental results. The kinetic data were also analyzed through pseudo-first-order and pseudo-second-order models. The pseudo-second-order kinetic model well depicted the kinetics of dyes adsorption on mesoporous SBA-3.

Keywords: Adsorption; Anionic dye; Methyl orange; Orange G; Brilliant red X-3B; Nanoporous silica SBA-3

Surface modification and characterization of magnesium hydroxide sulfate hydrate nanowhiskers by Chuan Hui Gao; Xian Guo Li; Li Juan Feng; Shao Yan Lu; Jin Yan Liu (pp. 3234-3239).

In order to enhance the compatibility with plastic polymers, magnesium hydroxide sulfate hydrate (MHSH) nanowhiskers were modified through grafting methyl methacrylate (MMA) on the surface of the nanowhiskers by emulsion polymerization. The influences of the reaction time, MMA monomer content, adding speed of monomer and the reaction temperature on the grafting ratio were investigated. Thermogravimetry (TG), Fourier transform infrared (FT-IR) spectroscopy, X-ray powder diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray (EDX) spectroscopy and surface contact angle measurement were used to characterize the effect of surface modification. The results showed that the MHSH nanowhiskers were uniformly coated by polymethyl methacrylate (PMMA), and a well-defined core–shell hybrid structure of MHSH/PMMA was obtained. The surface contact angle of the hybrid whiskers increased to 87.32° from 12.71° and the whiskers surface was changed from hydrophilic to lipophilic.

Keywords: Magnesium hydroxide sulfate hydrate (MHSH) nanowhisker; Surface modification; Polymethyl methacrylate (PMMA); Surface contact angle

Synthesis and enrichment of a macromolecular surface modifier PP- b-PVP for polypropylene by Man Xu; Xuhua Shi; Hanjia Chen; Tan Xiao (pp. 3240-3244).

Polypropylene-block-poly(vinylpyrrolidone) copolymer was synthesized through the esterification of dicarboxyl-terminated polypropylene with monohydroxyl-terminated poly(vinylpyrrolidone) and used as a macromolecular surface modifier to improve the surface hydrophilicity of PP. The results of ATR-FTIR and contact angles measurements indicated that PP -b-PVP could diffuse preferably onto the surface by the inducement of high energy interface and lower the water contact angle of polypropylene. Lower loading and lower molecular weight of PP and PVP segment would result in higher surface selective enrichment.

Keywords: Polypropylene; Block copolymers; Macromolecular surface modifier; ATR-FTIR

Interfacial morphology and domain configurations in 0-3 PZT–Portland cement composites by N. Jaitanong; H.R. Zeng; G.R. Li; Q.R. Yin; W.C. Vittayakorn; R. Yimnirun; A. Chaipanich (pp. 3245-3248).

Cement-based piezoelectric composites have attracted great attention recently due to their promising applications as sensors in smart structures. Lead zirconate titanate (PZT) and Portland cement (PC) composite were fabricated using 60% of PZT by volume. Scanning Electron Microscope and piezoresponse force microscope were used to investigate the morphology and domain configurations at the interfacial zone of PZT–Portland cement composites. Angular PZT ceramic grains were found to bind well with the cement matrix. The submicro-scale domains were clearly observed by piezoresponse force microscope at the interfacial regions between the piezoelectric PZT phase and Portland cement phase, and are clearer than the images obtained for pure PZT. This is thought to be due to the applied internal stress of cement to the PZT ceramic particle which resulted to clearer images.

Keywords: PZT; Cement; Composite; Ferroelectric domains; Piezoelectric force microscope

Influence of oxygen on the formation of cubic boron nitride by r.f. magnetron sputtering by Gang Qi; Yong-Kang Le (pp. 3249-3252).

Formation of cubic boron nitride by r.f. magnetron sputtering has been studied with O₂ addition to the common working gas Ar/N₂. The chemical and the phase composition were determined with Auger electron spectroscopy sputter depth profiling and Fourier transform infrared spectroscopy. The result shows that oxygen hinders the formation of cBN in sufficient nitrogen-supply, but facilitates the growth of cBN in insufficient nitrogen-supply. With insufficient nitrogen-supply, there exists an optimal oxygen-supply in the working gas that promoted the establishment of the stoichiometric condition in the growing film. O-concentration in the film increases with oxygen-supply in the working gas. cBN forms only when the oxygen concentration is below 5% and c_N/ c_B (ratio of concentration of nitrogen atoms and boron atoms) is 1 in the film.

Keywords: Cubic boron nitride; Influence of oxygen; Film composition

Influence of ethylene glycol pretreatment on effectiveness of atmospheric pressure plasma treatment of polyethylene fibers by Ying Wen; Ranxing Li; Fang Cai; Kun Fu; Shujing Peng; Qiuran Jiang; Lan Yao; Yiping Qiu (pp. 3253-3258).

For atmospheric pressure plasma treatments, the results of plasma treatments may be influenced by liquids adsorbed into the substrate. This paper studies the influence of ethylene glycol (EG) pretreatment on the effectiveness of atmospheric plasma jet (APPJ) treatment of ultrahigh molecular weight polyethylene (UHMWPE) fibers with 0.31% and 0.42% weight gain after soaked in EG/water solution with concentration of 0.15 and 0.3mol/l for 24h, respectively. Scanning electron microscopy (SEM) shows that the surface of fibers pretreated with EG/water solution does not have observable difference from that of the control group. The X-ray photoelectron spectroscopy (XPS) results show that the oxygen concentration on the surface of EG-pretreated fibers is increased less than the plasma directly treated fibers. The interfacial shear strength (IFSS) of plasma directly treated fibers to epoxy is increased almost 3 times compared with the control group while that of EG-pretreated fibers to epoxy does not change except for the fibers pretreated with lower EG concentration and longer plasma treatment time. EG pretreatment reduces the water contact angle of UHMWPE fibers. In conclusion, EG pretreatment can hamper the effect of plasma treatment of UHMWPE fibers and therefore longer plasma treatment duration is required for fibers pretreated with EG.

Keywords: Atmospheric pressure plasma treatment; Ethylene glycol; UHMWPE fiber; XPS; Interfacial shear strength

Sliding behavior of water drops on sol–gel derived hydrophobic silica films by Sanjay S. Latthe; Sunetra L. Dhere; Charles Kappenstein; Hiroaki Imai; V. Ganesan; A. Venkateswara Rao; Pratap B. Wagh; Satish C. Gupta (pp. 3259-3264).

Control on the wettability of solid state materials is a classical and key issue in surface engineering. Optically transparent methyltriethoxysilane (MTES)-based silica films with water sliding angle as low as 9° were successfully prepared by two-step sol–gel co-precursor method. The emphasis is given to the effect of trimethylethoxysilane (TMES) as a co-precursor on water sliding behavior of silica films. The coating sol was prepared with molar ratio of methyltriethoxysilane (MTES), methanol (MeOH), acidic water (0.01M, oxalic acid) and basic water (12M, NH₄OH) kept constant at 1:12.73:3.58:3.58 respectively, and the molar ratio of TMES/MTES (M) was varied from 0 to 0.22. The static water contact angle as high as 120° and the water sliding angle as low as 9° was obtained by keeping the molar ratio (M) of TMES/MTES at 0.22. When the modified films were cured at temperature higher than 280°C, the films became superhydrophilic. Further, the humidity study was carried out at a relative humidity of 90% at 30°C over 60 days. We characterized the water repellent silica films by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), % of optical transmission, humidity tests and static and dynamic water contact angle (CA) measurements.

Keywords: Sol–gel process; Hydrophobicity; Wetting; Humidity; Stability

Dry sliding wear behaviour of magnesium oxide and zirconium oxide plasma electrolytic oxidation coated magnesium alloy by P. Bala Srinivasan; J. Liang; C. Blawert; W. Dietzel (pp. 3265-3273).

Two types of PEO coatings, one consisting of magnesium oxide (MgO) and the other comprising zirconium oxide (ZrO₂) as the main phase composition were produced on AM50 magnesium alloy from alkaline and acidic electrolytes, respectively. The ZrO₂ coating was found to be spongy and thicker with a higher roughness, whilst the relatively more compact MgO coating was having contrasting features. In the dry sliding oscillating wear tests under two different loads viz., 2N and 5N, the ZrO₂ coating exhibited a very poor wear resistance. The MgO coating showed an excellent resistance to sliding wear under 2N load; however, the load bearing capacity of the coating was found to be insufficient to resist the wear damage under 5N load. The higher specific wear rates of the MgO coating under 5N load and that of the ZrO₂ coating under 2N and 5N loads were attributed to the poor load bearing capacity and a three-body-abrasive wear mechanism.

Keywords: Magnesium alloy; Plasma electrolytic oxidation; Microstructure; Dry sliding wear

Hydrophilic modification of microporous polysulfone membrane via surface-initiated atom transfer radical polymerization of acrylamide by Jianhua Qiu; Yanwu Zhang; Yongbo Shen; Yatao Zhang; Haoqin Zhang; Jindun Liu (pp. 3274-3280).

Polyacrylamide (PAM) brushes were grafted from chloromethylated polysulfone (CMPSF) membrane surface by surface-initiated atom transfer radical polymerization (SI-ATRP) to improve the membrane's hydrophilic property. In order to anchor the initiator onto polysulfone (PSF) membrane surface, CMPSF was used to prepare the microporous membrane by phase-inversion process. Attachment of the PAM chains on membrane surface was confirmed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The grafted density of PAM was calculated to be 0.08chainsnm⁻². Field emission scanning electron microscopy (FESEM) and atomic force microscope (AFM) were used to characterize the surface morphology of the CMPSF membrane and modified membrane. The number-average molecular weight ( M_n) of PAM linearly increased with the polymerization time, while the static water contact angle ( θ) of the membrane grafted with PAM linearly decreased. This indicated the hydrophilic property of the membrane was linearly correlated with the chain length of graft polymer. Therefore linear control of PSF membrane's hydrophilic property was realized through adjusting polymerization time.

Keywords: Surface-initiated atom transfer radical polymerization (SI-ATRP); Membranes; Hydrophilic polymers; Graft density

Engineering the crystal growth behavior: “On substrate” MOD formation of ZnO hollow spheres by Paula A.R. Tafulo; Marta Ferro; Ariel Guerreiro; Gerardo González-Aguilar (pp. 3281-3285).

In this paper is described an easy, one-pot synthesis of ZnO hollow spheres with sizes ranging from 300nm to 500nm, by spin-coating deposition on aluminum substrate. Simplified models explaining the shape formation based on film–substrate interaction are discussed. The characteristic size and shape of the nanostructures obtained by the described method and the properties of ZnO as a low-cost biocompatible material make this methodology of synthesis interesting for a wide range of applications including optoelectronics, catalysis and (bio)sensors.

Keywords: ZnO; Microstructures; Discontinuous films; Catalysis

A facile, green, and tunable method to functionalize carbon nanotubes with water-soluble azo initiators by one-step free radical addition by Yingkui Yang; Shengqiang Qiu; Xiaolin Xie; Xianbao Wang; Robert Kwok Yiu Li (pp. 3286-3292).

Versatile functional groups were covalently attached to the surface of multiwalled carbon nanotubes (MWNTs) by one-step free radical addition of water-soluble azo initiators. The coverage density of functional groups is rationally controlled either by adjusting the feed ratio of azo initiators to MWNTs or by utilizing the starting chemicals of multifunctional groups. TEM observations in conjunction with solubility data imply that the functionalized-MWNTs have much better dispersibility and stability than pristine MWNTs in polar solvents. The attached carboxylic groups were then used as scaffolds to chelate Ag⁺ ions affording Ag/MWNTs nanohybrids in the presence of NaBH₄ reductant. This shows that the reactive groups anchored on MWNTs can be further chemically functionalized. The proposed method might open many new opportunities for the development of high-performance nanomaterials containing CNTs.

Keywords: Carbon nanotubes; Free radical addition; Green functionalization; Azo initiators

Effect of RF power on the optical and morphological properties of RF plasma polymerised linalyl acetate thin films by L.J. Anderson; M.V. Jacob (pp. 3293-3298).

Thin films derived from linalyl acetate were fabricated using the Radio Frequency (RF) plasma polymerisation technique between RF power levels of 10 and 75W. The optical properties of the films were investigated using spectroscopic ellipsometry and UV–vis spectroscopy between 200 and 1000nm. An optical band gap of approximately 3eV for all power levels was determined from Tauc plots. The surface morphology and hardness of the material were studied using AFM and nano-indentation respectively to determine the effect of RF power on the thin film properties. Smooth surfaces with an average roughness of approximately 0.2nm with consistent morphology were obtained across all power levels, while hardness demonstrated a linearly increasing dependence on RF deposition power, with values ranging between 0.29 and 0.44GPa. These studies indicate the ability to tailor film characteristics by varying the RF deposition power, and the potential for the films to be used within electronic devices as encapsulation layers, insulating layers, or as semiconducting layers with the introduction of charge carriers to the chemical structure of the material.

Keywords: Thin film; Optical band gap; Plasma polymerisation; UV–vis spectroscopy; Spectroscopic ellipsometry; AFM

Effect of strain relaxation of oxidation-treated SiGe epitaxial thin films and its nanomechanical characteristics by Bo-Ching He; Hua-Chiang Wen; Tun-Yuan Chinag; Zue-Chin Chang; Derming Lian; Wei-Hung Yau; Wen-Fa Wu; Chang-Pin Chou (pp. 3299-3302).

In this study, we examined the effect of high-temperature oxidation treatment on the SiGe epitaxial thin films deposited on Si substrates. The X-ray diffraction (XRD), atomic force microscopy (AFM), and nanoindentation techniques were employed to investigate the crystallographic structure, surface roughness, and hardness ( H) of the SiGe thin films, respectively. The high-temperature oxidation treatment led to Ge pileup at the surface of the SiGe thin films. In addition, strain relaxation occurred through the propagation of misfit dislocations and could be observed through the cross-hatch pattern (800–900°C) and SiGe islands (1000°C) at the surface of the SiGe thin films. Subsequent hardness ( H) measurement on the SiGe thin films by continuous penetration depth method indicated that the phenomenon of Ge pileup caused a slightly reduced H (below 50nm penetration depth), while relaxation-induced defects caused an enhanced H (above 50nm penetration depth). This reveals the influence of composition and defects on the structure strength of high-temperature oxidation-treated SiGe thin films.

Keywords: PACS; 61.72.uf; 61.05.cp; 81.16.Ta; 62.20.QpSilicon–germanium; X-ray diffraction; Atomic force microscope; Hardness

2D-isothermal compressibility of deposited gold layer on Au(111) surface by A.H. Ayyad (pp. 3303-3304).

Based on thermodynamic arguments, a simple formula is derived that relates the 2D-isothermal compressibility, κ_2D, directly to ( ∂L_D/ ∂E)_T and ( ∂L_D/ ∂N)_T, where L_D is the stripe separation of the Au(111) surface, E is the applied electrode potential and N is the surface concentration of deposit. It accounts for the deposition-induced compression of the top most Au(111) surface layer during gold deposition. Furthermore, the value of κ_2D for the deposited gold layer on Au(111) surface has been experimentally determined. The results reveal that the κ_2Dvalue for gold does not match the reported trend for other metals.

Fabrication and characterization of Au/SiO₂ nanocomposite films by Boshi Zhuo; Yuguo Li; Shuyun Teng; Aichun Yang (pp. 3305-3308).

Au/SiO₂ nanocomposite films were prepared by radio frequency sputtering technique and annealing. The above nanocomposite films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and atomic force microscopy (AFM). The surface of the nanocomposite films was uniform with the particle diameter of 100–300nm. The size of Au crystallites increased on increasing annealing time. The luminescent behavior of the nanocomposite films was characterized by photoluminescence (PL) with different excitation wavelengths. Two emission peaks at around 525nm and 560nm were observed with the excitation wavelength at 325nm. An intensive emission peak at around 325nm was observed with the excitation wavelength at 250nm, which is related to the defective structure of the amorphous SiO₂ layer because of oxygen deficiency, and could be applied to many fields, such as ultraviolet laser and ultraviolet detector.

Keywords: PACS; 79.60.Jv; 81.15.Cd; 78.55.−mAu/SiO; ₂; Nanocomposite film; Sputtering; Photoluminescence

Modification of bamboo-based activated carbon using microwave radiation and its effects on the adsorption of methylene blue by Qing-Song Liu; Tong Zheng; Nan Li; Peng Wang; Gulizhaer Abulikemu (pp. 3309-3315).

Modification of bamboo-based activated carbon was carried out in a microwave oven under N₂ atmosphere. The virgin and modified activated carbons were characterized by means of low temperature N₂ adsorption, acid–base titration, point of zero charge (pH_pzc) measurement, FTIR and XPS spectra. A gradual decrease in the surface acidic groups was observed during the modification, while the surface basicity was enhanced to some extent, which gave rise to an increase in the pH_pzc value. The species of the functional groups and relative content of various elements and groups were given further analysis using FTIR and XPS spectra. An increase in the micropores was found at the start, and the micropores were then extended into larger ones, resulting in an increase in the pore volume and average pore size. Adsorption studies showed enhanced adsorption of methylene blue on the modified activated carbons, caused mainly by the enlargement of the micropores. Adsorption isotherm fittings revealed that Langmuir and Freundlich models were applicable for the virgin and modified activated carbons, respectively. Kinetic studies exhibited faster adsorption rate of methylene blue on the modified activated carbons, and the pseudo-second-order model fitted well for all of the activated carbons.

Keywords: Activated carbon; Modification; Microwave; Adsorption; Methylene blue

Structural and electrical properties of (Na_0.85K_0.15)_0.5Bi_0.5TiO₃ thin films deposited on LaNiO₃ and Pt bottom electrodes by X.J. Zheng; S.H. Dai; X. Feng; T. Zhang; D.Z. Zhang; Y.Q. Gong; Y.Q. Chen; L. He (pp. 3316-3320).

(Na_0.85K_0.15)_0.5Bi_0.5TiO₃ thin films were deposited on LaNiO₃(LNO)/SiO₂/Si(100) and Pt/Ti/SiO₂/Si(100) substrates by metal–organic decomposition, and the effects of bottom electrodes LNO and Pt on the ferroelectric, dielectric and piezoelectric properties were investigated by ferroelectric tester, impedance analyzer and scanning probe microscopy, respectively. For the thin films deposited on LNO and Pt electrodes, the remnant polarization 2 P_r are about 22.6 and 8.8μC/cm² under 375kV/cm, the dielectric constants 238 and 579 at 10kHz, the dielectric losses 0.06 and 0.30 at 10kHz, the statistic d_33eff values 95 and 81pm/V. The improved piezoelectric properties could make (Na1−_xK_x)_0.5Bi_0.5TiO₃ thin film as a promising candidate for piezoelectric thin film devices.

Keywords: (Na; _0.85; K; _0.15; ); _0.5; Bi; _0.5; TiO; ₃; thin film; Metal–organic decomposition; Bottom electrode; Porosity; Dielectric; Piezoelectric

H₂ reactivity on the surfaces of In and Sn at 298K by Masahiro Terashima; Rui Yamakawa; Yukinori Tani; Hirohisa Uchida; Shunsuke Kato; Yoshihito Matsumura; Haru-Hisa Uchida; Masashi Sato; Volodymyr A. Yartys; Jan Petter Maehlen (pp. 3321-3324).

The reactivity of H₂ gas with the In and Sn surfaces was quantitatively measured by a volumetric method at pressures ranging from 10⁻⁷ to 10⁻²Pa at 298K. Significant enhancement of H₂ reactivity was observed when O₂ or H₂O preadsorbed on the surface of In and Sn before H₂ exposure. The formation of the oxygen deficient SnO2−_x and In₂O3−_z in the surface layers is proposed as a reason for such a facilitating the H₂ dissociation and resulting in the enhancement of the H₂ reactivity at 298K.

Keywords: Gas–solid reaction; Kinetics; Hydrogen; Indium; Tin

Multiple UV-blue luminescence emissions in electrochemical anodic etched n-type silicon wafer by Yunsen Zhang; Zhimei Yang; Donglai Niu; Eryong Nie; Xue Bai; Zhifeng Jiao; Yong Jin; Min Gong; Xiaosong Sun (pp. 3325-3329).

This very paper is focusing on the preparation of porous nanostructures in n-type silicon (111) wafer by chemical etching technique in alkaline aqueous solutions of 5M NaOH, 5M K₂CO₃ and 5M K₃PO₄, and particularly, on its ultraviolet-blue photoluminescence emission. The anodic chemical etched silicon wafer has been characterized by means of optical microscopy, scanning electron microscopy, fluorescence spectroscopy, atomic force microscopy and Fourier transform infrared spectroscopy. This very surface morphology characterization has been clearly shown – the effect of anodic-chemical-etching procedure processed in K₂CO₃ or K₃PO₄ was much vigorous than that processed in NaOH. The FTIR spectra indicate that the silicon oxide was formed on the surface of electrochemical etched n-Si (111) wafers, yet not on that of the pure chemical etched ones anyhow. And an intense ultraviolet-blue photoluminescence emission is observed, which then differs well from the silicon specimen etched in alkaline solution with no anodic potential applied. The proper photoluminescence mechanism is discussed, and hence there may be a belief that the intense ultraviolet-blue photoluminescence emission would be attributed to the silicon oxide coating formed on silicon wafer in anodic-chemical-etching process.

Keywords: Anodic chemical etching; n-Type silicon; UV-blue photoluminescence; Silicon oxide coating

Preparation and characterization of branched polymers as postoperative anti-adhesion barriers by Tzong-Der Way; Shih-Rong Hsieh; Chi-Jung Chang; Tsung-Wei Hung; Chun-Hwei Chiu (pp. 3330-3336).

Homopolymers and copolymers synthesized from biocompatible monomers with polyethylene glycol (PEG) and polycaprolactone side chains, were applied to separate healing tissues and prevent postsurgical adhesions. The results of the contact angle and the ESCA spectra reveal the presence of more PEG segments on the surface of the PEMC1 film than the P(EM)₃(EMC4)₁ film. The effects of the molecular structures on the surface properties, including the wetting properties and the anti-tissue adhesion behaviors, of the films were examined. Fluorescent polymer was fixed on the surface of the film to form the marking dot. The in vivo degradation behaviors of the surface-marked films were investigated non-invasively by monitoring the location of the fluorescent signal. The degradation behaviors of various films observed in the animal study were consistent with those observed by in vivo imaging. Proper arrangement of PEG segments on the polymer side chain helped to keep a large proportion of PEG segments close to the surface of the film. Such an arrangement represents an effective means of preventing postoperative tissue adhesion.

Keywords: Anti-adhesion barriers; Photopolymerization; Fluorescent; In vivo; imaging; Surface properties

Sol–gel derived 6SrO·6BaO·7Al₂O₃ thin films using metal alkoxides by P.M. Chavhan; R.K. Sharma; N.K. Kaushik (pp. 3337-3341).

A novel 6SrO·6BaO·7Al₂O₃ (S6B6A7) thin film has been deposited onto soda lime float glass via sol–gel dip coating technique. The optical and electrical properties of S6B6A7 films annealed in air and H₂ atmosphere have been investigated. The structural and compositional properties of the S6B6A7 thin films have been investigated using Fourier transferred infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The S6B6A7 films prepared using 5 (wt.%) sol and annealed at 450°C in air and H₂ atmosphere exhibit an average transmittance of over ∼91% in wide visible range. The electrical properties of the S6B6A7 films affect film thickness as revealed by sheet resistance measurements. The sheet resistance of the 150nm S6B6A7 films was 67.85 and 6.06 kilo ohms per square for air and H₂ annealed, respectively.

Keywords: Barium strontium aluminium oxide; Sol–gel; Thin films; XPS; Optical properties; Sheet resistance

Diffusion research between Ni₃Al coating and titanium alloy produced by plasma spraying process by Wenming Wang; Bin Yang; Lingzhong Du; Weigang Zhang (pp. 3342-3345).

A Ni₃Al coating was prepared by plasma spraying technique on the surface of titanium alloy. Ni–Al mixed powders, coatings and reaction products were investigated by scanning electron microscope, EDS, DSC and XRD. A tight bonding between the coating and the substrate was formed. The X-ray diffraction analysis of the patterns showed that the coating not only had Ni₃Al phase, but also had NiO and Al₂O₃ phase microcontent. Comparing Ni coated Al to Ni₃Al at 900°C, the diffusion was stronger and the diffusion layer was thicker. A minute pore structure was formed at 1200°C in the front edge of solid-state reaction layer. So Ni₃Al restrained the solid-state reaction of the coating with the substrate, and as a whole weakened the entry of oxygen atoms into the substrate and quenched the out-diffusion of titanium.

Keywords: Ni; ₃; Al; Plasma spraying; Diffusion; Intermetallics

Enhanced catalytic performances by surface silylation of Cu(II) Schiff base-containing SBA-15 in epoxidation of styrene with H₂O₂ by Ying Yang; Jingqi Guan; Pengpeng Qiu; Qiubin Kan (pp. 3346-3351).

Schiff base functionalized SBA-15 mesoporous materials were synthesized by post-grafting of salicylaldehyde onto silylated and non-silylated amino-modified SBA-15 and followed by the introduction of Cu(II) ions via a ligand exchange reaction. Both hybrid materials prepared were characterized by XRD, FT-IR, UV–vis spectroscopy, N₂ adsorption/desorption, TG/DTA and ICP-AES techniques and comparatively examined as catalysts in epoxidation of styrene with 30wt.% aqueous hydrogen peroxide as oxidant. It was found that the silylated material was more active and selective to styrene oxide than the non-silylated one in CH₃CN. The considerably improved activity (86.1%) and styrene oxide selectivity (95.2%) were achieved after 30min when adding sodium hydroxide to maintain a pH of 7.5–8.0 in reaction medium. Moreover, the silylated catalyst showed good recoverability and relatively high stability against leaching of active copper species. These superior effects were attributed to the high hydrophobic character of the solid surface produced by the silanol neutralization.

Keywords: Copper(II) Schiff base complex; Silylation; Hydrophobicity; Epoxidation of styrene

A study of indium incorporation in In-rich InGaN grown by MOVPE by Y. Guo; X.L. Liu; H.P. Song; A.L. Yang; X.Q. Xu; G.L. Zheng; H.Y. Wei; S.Y. Yang; Q.S. Zhu; Z.G. Wang (pp. 3352-3356).

InGaN/GaN heterostructures have been deposited onto (0001) sapphire by our home-made low pressure MOVPE with different growth parameters. It has been noted that the indium incorporation depends by a complex way on a number of factors. In this work, the effect of substrate temperature, trimethylindium input flow and V/III ratio on the indium incorporation has been investigated. Finally, by optimizing the growth parameters, we made a series of single-phase InGaN samples with indium content from 10% up to 45%.

Keywords: MOVPE; In-rich InGaN; Indium incorporation

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Applied Surface Science (v.256, #10)

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Applied Surface Science (v.256, #10)