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Applied Surface Science (v.254, #18)

Effects of parallel magnetic field on electrocodeposition behavior of Ni/nanoparticle composite electroplating by Chao Wang; Yunbo Zhong; Weili Ren; Zuosheng Lei; Zhongming Ren; Jing Jia; Airong Jiang (pp. 5649-5654).

In this paper, an external high parallel magnetic field was superimposed into the codeposition process of Ni/nano-Al₂O₃ composites. It was found that the distribution of nanoparticles showed the network shape when superimposing a magnetic field, and the average size of the single network increased with increasing the current density. High concentration of nanoparticle could be obtained at low current density with a magnetic field, while a high current density was needed to realize that when without a magnetic field. The superimposed magnetic filed would improve the current efficiency. A possible mechanism on forming network shape was discussed.

Keywords: High static magnetic field; Nickel; Nano-alumina particle; Composite electroplating; Micro-MHD

Effect of surface modification by thermally oxidization and HF etching on UV photoluminescence emission of porous silicon by Huabing Song; Zhiwei Li; Hao Chen; Zhifeng Jiao; Zhou Yu; Yong Jin; Zhimei Yang; Min Gong; Xiaosong Sun (pp. 5655-5659).

Photoluminescence of porous silicon (PS) is instable due perhaps to the nanostructure modification in air. The controllable structure modification processes on the as-prepared PS were conducted by thermal oxidization and/or HF etching. The PL spectra taken from thermally oxidized PS showed a stable photoluminescence emission of 355nm. The photoluminescence emission taken from both of PS and oxidized porous silicon (OPS) samples etched with HF were instable, which can be reversibly recovered by the HF etching procedure. The mechanism of UV photoluminescence is discussed and attributed to the transformation of luminescence centers from oxygen deficient defects to the oxygen excess defects in the thermal oxidized PS sample and surface absorbed silanol groups on PS samples during the chemical etched procedure.

Keywords: PACS; 81.05.Rm; 81.07.BcPorous silicon; Oxidization; HF etching; Photoluminescence; Oxygen defect

Infrared optical properties of Ba(Zr_0.20Ti_0.80)O₃ and Ba(Zr_0.30Ti_0.70)O₃ thin films prepared by sol–gel method by Aiyun Liu; Jianqiang Xue; Xiangjian Meng; Jinglan Sun; Zhiming Huang; Junhao Chu (pp. 5660-5663).

Ba(Zr_xTi1−_x)O₃ (BZT) ( x=0.20 and 0.30) thin films are deposited on Pt(111)/Ti/SiO₂/Si(100) substrate by sol–gel method. X-ray diffraction patterns show that the thin films have a good crystallinity. Optical properties of the films in the wavelength range of 2.5–12μm are studied by infrared spectroscopic ellipsometry (IRSE). The optical constants of the BZT thin films are determined by fitting the IRSE data using a classical dispersion formula. As the wavelength increases, the refractive index decreases, while the extinction coefficients increase. The effective static ionic charges are derived, which are smaller than that in a purely ionic material for the BZT thin films.

Keywords: PACS; 77.55.+f; 78.20.−e; 78.20.CiBZT; Optical properties; Sol–gel method

Influence of a controlled oxidation at moderate temperatures on the surface chemistry of nitinol wire by D. Vojtech; L. Joska; J. Leitner (pp. 5664-5669).

Commercial nitinol wire is oxidised at 480–530°C/10min in air. Surface morphology and chemistry is studied in detail using scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction, Raman spectrometry and X-ray photoelectron spectroscopy. It is found that the main oxidation product at both temperatures is rutile containing a few at.% Ni. Beneath the rutile layer, there are titanium sub-oxides, showing characteristic maxima in depth profiles. Nickel in an oxidised state is present on the surface, whereas in a sub-surface region of scales, there is only metallic nickel. Thickness of the total oxide layers is 70 and 140nm after oxidation at 480 and 530°C, respectively. The preferential oxidation of titanium causes the formation of a Ni-enriched and Ti-depleted zone, suggesting the presence of Ni₃Ti phase. XRD reveals that the presence of cubic B2 NiTi phase in the base alloy is not affected by oxidation at 480–530°C/10min.

Keywords: PACS; 71.20.Lp; 68.47.Gh; 68.55.−aNiTi alloy; Shape memory alloy; Oxidation; X-ray photoelectron spectroscopy

Copper diffusion in TaN-based thin layers by J. Nazon; B. Fraisse; J. Sarradin; S.G. Fries; J.C. Tedenac; N. Fréty (pp. 5670-5674).

The diffusion of Cu through TaN-based thin layers into a Si substrate has been studied. The barrier efficiency of TaN/Ta/TaN multilayers of 150nm in thickness has been investigated and is compared with that of TaN single layers. Thermal stabilities of these TaN-based thin layers against Cu diffusion were determined from in situ X-ray diffraction experiments, conducted in the temperature range of 773–973K. The TaN/Ta/TaN barrier appeared to be more efficient in preventing Cu diffusion than the TaN single layer.

Keywords: PACS; 85.40.Ls; 66.30.Ny; 66.30.XjTantalum nitride; Reactive sputtering; Microstructure; Diffusion; In situ glancing analysis

Catalytic conversion of air–methane flow by nanostructured ruthenium dioxide: FTIR spectroscopy and modeling by Pawel Nowakowski; Sylvie Villain; Agnieszka Kopia; I. Suliga; Jean-Raymond Gavarri (pp. 5675-5682).

Nanostructured powders of ruthenium dioxide RuO₂ were synthesized via a sol–gel route involving acidic solutions with pH varying between 0.4 and 4.5. The RuO₂ nanopowders were characterized by X-ray diffraction. Crystallite sizes measured from X-ray diffraction profiles and TEM analysis varied in the range 8–16nm, with a minimum of crystallite dimension for pH 1.5. Catalytic conversion of methane by these RuO₂ nanostructured catalysts was studied as a function of pH, catalytic interaction time, air methane composition, and catalysis temperature, by the way of Fourier transform infrared (FTIR) spectroscopy coupled to homemade catalytic cell. The catalytic efficiency defined as FTIR absorption band intensities I(CO₂) was maximum for sample prepared at pH 1.5, and mainly correlated to crystallite dimensions. A modeling approach of catalytic conversion is proposed for such a specific experimental configuration.

Keywords: Ruthenium dioxide; Sol–gel process; Nanopowders; X-ray diffraction analysis; Catalytic properties; Infrared spectroscopy; Modeling approach

Investigation of heat-treatment and pre-treatment on microstructure and electrochemical properties of cerium nano-oxide films on AA7020-T6 by sol–gel methods by H. Hasannejad; Taghi Shahrabi; Alireza Sabour Rouhaghdam; M. Aliofkhazraei; E. Saebnoori (pp. 5683-5690).

In this paper cerium nano-oxide films were applied on AA7020-T6 alloy by sol–gel method. Potentiodynamic polarization and EIS studies have been used to study the corrosion behavior of cerium oxide nano films in 3.5% NaCl. Microstructural and phase properties of cerium oxide were investigated by SEM and XRD. The results showed that heat-treatment temperature and pre-treatment have an important effect on microstructure and electrochemical properties of cerium nano-oxide films. It can be seen from the results that with increasing heat-treatment temperature from 150 to 300°C, the corrosion resistance of the films increased. It is related to increase the condensation of the films with adding temperature. Also, it can be seen that with adding temperature from 300 to 400°C, the corrosion resistance of the films decrease. This is an important case related to crystallization of the cerium oxide films between 300 and 400°C which showed that crystallized ceria films illustrate less corrosion resistance with respect to an amorphous film. Although with applying cerium oxide films the corrosion resistance of the films increased but still the passive region of the ceria films was tiny. So that in this research especially pre-treatment (etching in NaOH solution for 1min, washing with deionized water for 5min, etching with acid solution which contained several acids (H₂SO₄, HF, HCl, H₃PO₄), washing with deionized water for 5min and after that following the samples in boiling deionized water for 1h) was applied on samples before ceria treatment. The results showed that after applying this pre-treatment the passive region of the films increased extremely. It is related to formation of the thick and porous alumina films after applying pre-treatment which are similar to millepore.

Keywords: Cerium nano-oxide; Heat-treatment; Pre-treatment; Sol–gel; SEM; XRD

Comparative study on modification of multi-walled carbon nanotubes by a hydrophilic polymer with different approaches by Jun Qiu; Guo-Jian Wang (pp. 5691-5694).

The multi-walled carbon nanotubes (MWNTs) modified by a hydrophilic polymer were prepared with polymerization and blending approaches. The differences of both modified MWNTs were compared by Fourier transform infrared and Raman spectroscopies, thermogravimetric analysis and transmission electron microscopy. Chemical grafting reaction had occurred between MWNTs and polyvinyl pyrrolidone (PVP) after modification with polymerization and blending approaches. Polymerization modification can graft more PVP on the surface of MWNTs compared with blending modification. Polymerization modification of MWNTs belongs to the “grafting from” mechanism, while blending modification belongs to the “grafting to” mechanism. Modified MWNTs exhibit remarkable solubility in water, ethanol and dimethyl formamide.

Keywords: Nanomaterials; Multi-walled carbon nanotubes; Modification; Polymers; Surfaces

Light-induced reversible hydrophilicity of ZnO structures grown by aqueous chemical growth by G. Kenanakis; E. Stratakis; K. Vlachou; D. Vernardou; E. Koudoumas; N. Katsarakis (pp. 5695-5699).

ZnO wurtzite microrods and flowerlike structures were deposited on glass and ITO substrates by the aqueous chemical growth (ACG) technique at mild temperature (95°C). Wettability studies revealed that the as-deposited structures are hydrophilic and super-hydrophilic for short and long growth times, respectively. The hydrophilic ZnO surfaces could be reversibly switched to super-hydrophilic by alternation of UV illumination and dark storage. Our results demonstrate that ACG at low temperatures can be efficiently employed to deposit transparent photosensitive ZnO structures exhibiting reversible wettability changes.

Keywords: ZnO; Microstructures; Aqueous chemical growth; Wettability

Role of reactive gas in atmospheric plasma for cell attachment and proliferation on biocompatible poly ɛ-caprolactone film by Hyun-Uk Lee; Ye-Sul Jeong; Se-Young Jeong; So-Young Park; Jong-Seong Bae; Hyun-Gyu Kim; Chae-Ryong Cho (pp. 5700-5705).

This paper reports the surface modification of a biocompatible poly ɛ-caprolactone (PCL) film treated by atmospheric cold plasma (ACP) with reactive gases. The change in wettability and surface morphology of the PCL film after the plasma treatment with the reactive gases (Ar, H₂, N₂ and O₂) were determined using contact angle and surface roughness measurements. The chemical bonding states and molecular vibration modes of the activated organic groups on the polymer surface were examined by X-ray photoelectron spectroscopy and Fourier-transformation infrared techniques. The surface of the ACP-treated PCL films was also examined for their in vitro cell attachment and proliferation using human prostate epithelial cells (HPECs). The increase in the hydrophobicity of the Ar+H₂ plasma-treated PCL film resulted in a lower cell loading in the initial step of cell culture as well as a decrease in the level of cell attachment and proliferation compared with the pristine film. However, the hydrophilic properties of the Ar+N₂, Ar and Ar+O₂ plasma-treated PCL film improved the adhesion properties. Therefore, the Ar+N₂, Ar and Ar+O₂ plasma-treated PCL films showed a better cell distribution and growth than that of the pristine PCL film. The ACP-treated PCL film is potentially useful as a suitable scaffold in biophysics and bio-medical engineering applications.

Keywords: PACS; 52.77.−j; 52.25.−b; 52.40.Hf; 82.33.Xj; 52.77.BnAtmospheric plasma; Surface modification; Poly ɛ-caprolactone; Cell proliferation

Adsorption and dissociation of ammonia on Au(111) surface: A density functional theory study by Ruiqiu Liu; Wei Shen; Jinsheng Zhang; Ming Li (pp. 5706-5710).

Periodic density functional theory (DFT) calculations using plane waves had been performed to systematically investigate the stable adsorption amine and its dehydrogenated reaction on Au(111) surface. The equilibrium configuration including on top, bridge, and hollow (fcc and hcp) sites had been determined by relaxation of the system. The adsorption both NH₃ on top site and NH₂ on bridge site is favorable on Au(111) surface, while the adsorption of NH on hollow (fcc) site is preferred. The adsorbates are adsorbed on the gold surface with the interaction between p orbital of adsorbate and the d orbital of gold atoms. The interaction between adsorbate and gold slab is more evident on the first layer than on any others. Furthermore, the dissociation reaction of NH₃ on clean gold surface, as well as on the pre-covered oxygen atom and pre-covered hydroxyl group surface had been investigated. The results show that the dehydrogenated reaction energy barrier on the pre-covered oxygen gold surface is lower. The adsorbed O can promote the dehydrogenation of amine. Additionally, OH as the product of the NH₃ dissociation reaction participates in continuous dehydrogenation reaction, and the reaction energy barrier is the lowest (22.77kJ/mol). The results indicated that OH_ads play a key role in the dehydrogenated reaction on Au(111) surface.

Keywords: Gold surface; Adsorption; Amine dissociation; DFT

Chemical bath-deposited ZnS thin films: Preparation and characterization by Qi Liu; Mao Guobing; Ao Jianping (pp. 5711-5714).

Chemical bath deposition of ZnS thin films from NH₃/SC(NH₂)₂/ZnSO₄ solutions has been studied. The effect of various process parameters on the growth and the film quality are presented. The influence on the growth rate of solution composition and the structural, optical properties of the ZnS thin films deposited by this method have been studied. The XRF analysis confirmed that volume of oxygen of the as-deposited film is very high. The XRD analysis of as-deposited films shows that the films are cubic ZnS structure. The XRD analysis of annealed films shows the annealed films are cubic ZnS and ZnO mixture structure. Those results confirmed that the as-deposited films have amorphous Zn(OH)₂. SEM studies of the ZnS thin films grown on various growth phases show that ZnS film formed in the none-film phase is discontinuous. ZnS film formed in quasi-linear phase shows a compact and a granular structure with the grain size about 100nm. There are adsorbed particles on films formed in the saturation phase. Transmission measurement shows that an optical transmittance is about 90% when the wavelength over 500nm. The band gap ( E_g) value of the deposited film is about 3.51eV.

Keywords: PACS; 81.15.Lm; 68.55.ag; 78.66.HfChemical bath deposition (CBD); ZnS thin film; CIGS solar cells

Microstructure characteristics of laser–MIG hybrid welded mild steel by Ming Gao; Xiaoyan Zeng; Jun Yan; Qianwu Hu (pp. 5715-5721).

To deepen the understanding of laser–arc hybrid welding, the weld shape and microstructure characteristics of laser–metal inert gas hybrid welded mild steel were analyzed. The results showed typical hybrid weld could be classified as two parts: the wide upper zone and the narrow nether zone, which were defined as arc zone and laser zone, respectively. In the hybrid weld, the microstructure, alloy element distribution and microhardness all have evident difference between laser zone and arc zone. The microstructure of arc zone consists of coarse columnar dendrite and fine acicular dendrite between the columnar dendrites, but that of laser zone is composed of fine equiaxed dendrite in weld center and columnar dendrite around the equiaxed dendrite. Compared to arc zone, laser zone has finer grain size, higher microhardness, smaller alloy element content in the fusion zone and narrower heat affected zone. The discussions demonstrated that the observed difference was caused by the difference of temperature gradient, crystallizing and the effects of arc pressure on the molten pool between laser zone and arc zone.

Keywords: Microstructure; Hybrid welding; Laser welding; Metal inert gas

Fluorination of polymethylmethaacrylate with tetrafluoroethane using DC glow discharge plasma by S. Guruvenket; Ganjigunte R.S. Iyer; Larisa Shestakova; Per Morgen; N.B. Larsen; G. Mohan Rao (pp. 5722-5726).

Fluorination of polymer surfaces has technological applications in various fields such as microelectronics, biomaterials, textile, packing, etc. In this study PMMA surfaces were fluorinated using DC glow discharge plasma. Tetrafluoroethane was used as the fluorinating agent. On the fluorinated PMMA surface, static water contact angle, surface energy, optical transmittance (UV–vis), XPS and AFM analyses were carried out. After the fluorination PMMA surface becomes hydrophobic with water contact angle of 107° without losing optical transparency. Surface energy of fluorine plasma-treated PMMA decreased from 35mJ/cm² to 21.2mJ/cm². RMS roughness of the fluorinated surface was 4.01nm and XPS studies revealed the formation of C–CF_x and CF₃ groups on the PMMA surface.

Keywords: Plasma polymerization; PMMA; Fluorocarbon coatings

Secondary ion species containing nitrogen atoms from plasma-enhanced chemical vapor deposited silicon oxide films on silicon by Kiyoshi Chiba; Yoshinori Tsuji (pp. 5727-5731).

Secondary ion species from plasma-enhanced chemical vapor deposited (PECVD) SiO₂ films have been investigated using time-of-flight secondary ion mass spectrometry (TOF-SIMS). Comparative studies of PECVD SiO₂ films prepared using a mixture of SiH₄/N₂O reaction gas at 400°C with thermally oxidized SiO₂ films grown at 900°C were carried out in the mid-range mass spectra from 95 to 165amu. Small amounts of ion species containing nitrogen atoms, including Si₂O₂N⁺, Si₃O₂N⁺and Si₃O₃N⁺, were detected in the SiO₂ bulk from the PECVD SiO₂ films. Furthermore, large amounts of Si₃O₂N⁺ and Si₂O₃N⁻ were found at the interface between silicon and the SiO₂ films. Depth analysis showed that the intensity peak shapes of these ion species containing nitrogen atoms at the interface were closely coincident with those of Si₃O₃⁺ corrected by subtracting the influence of the SiO₂ matrix. The variation in the spectra of these ion species clearly indicates that two types of structures of oxynitride exist for the PECVD SiO₂ films in the SiO₂ bulk films and at the interface. These are likely produced by the reaction of reactive gas with SiO₂ and silicon surfaces where dangling bonds of silicon may exist in the different form.

Keywords: PACS; 68.49.Sf; 68.55.Jk; 73.40.Qv; 77.55.+fSilicon oxide; Nitrogen incorporation; Oxynitride; Secondary ion species; Time-of-flight secondary ion mass spectrometry

Structural studies of evaporated Co_xCr1−_x/Si (100) and Co_xCr1−_x/glass thin films by A. Kharmouche; I. Djouada (pp. 5732-5735).

Series of Co_xCr1−_x thin films have been evaporated under vacuum onto Si (100) and glass substrates. Chemical composition and interface properties have been studied by modelling Rutherford backscattering spectra (RBS) using SIMNRA programme. Thickness ranges from 17 to 220nm, and x from 0.80 to 0.88. Simulation of the energy spectra shows an interdiffusion profile in the thickest films, but no diffusion is seen in thinner ones. Microscopic characterizations of the films are done with X-ray diffraction (XRD) measurements. All the samples are polycrystalline, with an hcp structure and show a 〈0001〉 preferred orientation. Atomic force microscopies (AFM) reveal very smooth film surfaces.

Keywords: PACS; 61.60.−i; 81.30.Dz; 75.70.−i; 82.80.Yc; 68.37.PsX-ray diffraction (XRD); CoCr system; Thin films; Rutherford backscattering spectrometry (RBS); Atomic force microscopies (AFM)

Investigation of electrical and ammonia sensing characteristics of Schottky barrier diode based on a single ultra-long ZnO nanorod by Ning Zhang; Ke Yu; Lijun Li; Ziqiang Zhu (pp. 5736-5740).

Novel ultra-long ZnO nanorods, with lengths about 0.5–1.5mm and diameters ranging from 100 to 1000nm, in mass production have been synthesized via the vapor-phase transport method with CuO catalyst at 900°C. Rectifying Schottky barrier diodes have been fabricated by aligning a single ultra-long ZnO nanorod across paired Ag electrodes. The resulting current–voltage ( I– V) characteristics of the SBD exhibit a clear rectifying behavior. The ideality factor of the diode is about 4.6, and the threshold voltage is about 0.54V at room temperature (300K). At the same time the detailed I–V characteristics have been investigated in the temperature range 423–523K. In addition, after exposure of the Schottky diodes to NH₃, the forward and reverse currents increase rapidly, indicating a high sensitivity to NH₃ gas.

Keywords: PACS; 81.05.Dz; 73.40.Ei; 07.07.DfZinc oxide nanomaterials; Schottky barrier diode; Gas sensor

Roughness of pigment coatings and its influence on gloss by J. Järnström; P. Ihalainen; K. Backfolk; J. Peltonen (pp. 5741-5749).

A robust method is used for analyzing roughness at a wide range of lateral length scales. The method is based on two-point correlation where both the amplitude and lateral spacing of surface heights are considered when determining the roughness. Atomic force microcopy and confocal optical microscopy images were captured for a set of pigment-coated samples. The effects of sampling interval, image size and filtering on surface roughness were studied. Isotropy and periodicity of roughness were determined by analyzing the angular distribution of the correlation length ( T) and the autocorrelation function (ACF). A clear dependence of root mean square (RMS) roughness ( σ) on T was established for randomly distributed surfaces. By taking into account the σ– T dependence it was possible to obtain σ for various length scales for each sample and thus attaining the most relevant σ for a certain surface function, which in this study was specular reflection of light (gloss). The roughness analysis showed that a small amount of DPP coating was sufficient to completely cover and change the surface of the substrate, while kaolin coatings gave a different response.

Keywords: Surface roughness; Topography; Autocorrelation function; Correlation length; Gloss; Pigment coating; Atomic force microscopy; Confocal optical microscopy

Simulation of the transport of sputtered atoms and effects of processing conditions by A. Settaouti; L. Settaouti (pp. 5750-5756).

Sputter deposition is a complex process; it is obvious that the energy and direction of the particles arriving at the substrate is in close relation with the transport process from the target to the substrate, it is desirable to model this transport of atoms through the background gas. The transport of sputtered Ag atoms during sputter deposition through the gas phase in the facing targets sputtering system studied by Monte Carlo simulation is presented. The model calculates the flux of the atoms arriving at the substrate, their energy, direction and number of collisions they underwent. The dependence of the deposition rates of Ag atoms on the gas pressure and the distance between the targets and substrate were investigated.

Keywords: PACS; 52.77.−j; 52.25.−bMonte Carlo simulations; Sputtering; Sputtered particle transport

Preparation of needle shaped nano-copper by microwave-assisted water system and study on its application of enhanced epoxy resin coating electrical conductivity by Xifeng Zhang; Xiaonong Cheng; Hengbo Yin; Jian Yuan; Chi Xu (pp. 5757-5759).

Needle shaped nano-copper 90nm in length and 3nm in diameter was synthesized in microwave-assisted water system in which copper acetate, ascorbic acid and surfactant made by us are used as precursor, reductant, and modifiers, respectively. The as-prepared nano-copper was characterized by XRD, TEM and TG-DSC. The epoxy resin coating exhibited a better excellent electrical conductivity added to as-prepared needle shaped nano-copper, ρ_V=3.4×10⁻⁶Ωm than that of the coating added to sphere nano-copper, ρ_V=8.9×10⁻⁶Ωm.

Keywords: Copper nanocrystals; Microwave-assisted; Liquor-phase reduction synthesis; Needle shaped; Electrical conductivity

Optimization of plasma parameters for high rate deposition of titanium nitride films as protective coating on bell-metal by reactive sputtering in cylindrical magnetron device by Sankar Moni Borah; Arup Ratan Pal; Heremba Bailung; Joyanti Chutia (pp. 5760-5765).

Nano-structured titanium nitride (TiN) thin film coating is deposited by reactive sputtering in cylindrical magnetron device in argon and nitrogen gas mixtures at low temperature. This method of deposition using DC cylindrical magnetron configuration provides high uniform yield of film coating over large substrate area of different shapes desirous for various technological applications. The influence of nitrogen gas on the properties of TiN thin film as suitable surface protective coating on bell-metal has been studied. Structural morphological study of the deposited thin film carried out by employing X-ray diffraction exhibits a strong (200) lattice texture corresponding to TiN in single phase. The surface morphology of the film coating is studied using scanning electron microscope and atomic force microscope techniques. The optimized condition for the deposition of good quality TiN film coating is found to be at Ar:N₂ gas partial pressure ratio of 1:1. This coating of TiN serves a dual purpose of providing an anti-corrosive and hard protective layer over the bell-metal surface which is used for various commercial applications. The TiN film's radiant golden colour at proper deposition condition makes it a very suitable candidate for decorative applications.

Keywords: PACS; 52.77.Dq; 52.80.SmNano-structured titanium nitride thin film; Reactive sputtering; Cylindrical magnetron; Bell-metal; Anti-corrosive

Electrical conductivity and electromagnetic interference shielding characteristics of multiwalled carbon nanotube filled polyacrylate composite films by Yong Li; Changxin Chen; Song Zhang; Yuwei Ni; Jie Huang (pp. 5766-5771).

Multiwalled carbon nanotubes (MWCNTs) were homogeneously dispersed in pure acrylic emulsion by ultrasonication to prepare MWCNT/polyacrylate composites applied on building interior wall for electromagnetic interference (EMI) shielding applications. The structure and surface morphology of the MWCNTs and MWCNT/polyacrylate composites were studied by field emission scanning microscopy (FESEM) and transmission electron microscopy (TEM). The electrical conductivity at room temperature and EMI shielding effectiveness (SE) of the composite films on concrete substrate with different MWCNT loadings were investigated and the measurement of EMI SE was carried out in two different frequency ranges of 100–1000MHz (radio frequency range) and 8.2–12.4GHz (X-band). The experimental results show that a low mass concentration of MWCNTs could achieve a high conductivity and the EMI SE of the MWCNT/polyacrylate composite films has a strong dependence on MWCNTs content in both two frequency ranges. The SE is higher in X-band than that in radio frequency range. For the composite films with 10wt.% MWCNTs, the EMI SE of experiment agrees well with that of theoretical prediction in far field.

Keywords: PACS; 81.07.−b; 82.35.CdMultiwalled carbon nanotubes; Polyacrylate; Composite; Electromagnetic interference shielding; Concrete substrate

Studies on sintering of solid state synthesized Ba1−_xK_xBiO3−_δ superconducting phase by F.I.Shaikh; R.S. Kalubarme; S.H. Pawar (pp. 5772-5775).

Superconducting Ba1−_xK_xBiO3−_δ pellets were synthesized by solid state reaction followed by sintering. Thermo-gravimetric and differential thermo-gravimetric analysis (TG–DTA) of the mixture of nitrates was carried out to study the reactions during the phase formation. The effect of different sintering temperatures on the phase formation was studied. The X-ray diffraction data confirms the formation of superconducting Ba_0.6K_0.4BiO_2.23 phase at 700°C. The surface morphological studies as a function of sintering temperature were studied by SEM. It is observed that the pellets prepared by solid state reaction followed its sintering at 700°C shows the superconducting transition at 26.8K.

Keywords: Superconductivity; Solid state synthesis; TG–DTA

Surface analysis of oxygen plasma treated poly( p-phenylene benzobisoxazole) fibers by Chengshuang Zhang; Ping Chen; Baolei Sun; Wei Li; Baichen Wang; Jing Wang (pp. 5776-5780).

The influence of oxygen plasma treatment on surface properties of poly( p-phenylene benzobisoxazole) (PBO) fibers and aging effect of the oxygen plasma modified PBO fiber surfaces were investigated by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and dynamic contact angle analysis (DCAA), respectively. The results indicated that the oxygen plasma treatment introduced some polar groups to PBO fiber surfaces, enhanced surface roughness and changed surface morphologies of PBO fibers by plasma etching and oxidative reactions. Surface wettability of PBO fibers may be significantly improved by increasing surface free energy of the fibers via oxygen plasma treatment. Aging effect of the oxygen plasma treated PBO fibers showed that the fiber surface wettability degraded in the first several days after the plasma treatment, and it was found to be changeless as the aging time continued as long as 30 days.

Keywords: PBO fiber; Plasma treatment; XPS; AFM; Surface wettability

Chemical, energetic, and geometric heterogeneity of device-quality (100) surfaces of single crystalline silicon after HF_aq etching by G.F. Cerofolini; A. Giussani; A. Modelli; D. Mascolo; D. Ruggiero; D. Narducci; E. Romano (pp. 5781-5790).

An analysis, based on angle-resolved X-ray photoelectron spectroscopy, multiple-internal-reflection infrared spectroscopy, and atomic force microscopy, of device-quality (100)silicon surfaces after etching in dilute aqueous solution of HF is presented. The analysis shows that the surface is mainly formed by a heterogeneous distribution of SiH, SiH₂and SiH₃ terminations, but contains sub-stoichiometric oxidized silicon. The analysis shows moreover the existence of a form of reduced silicon, not consistent with the currently accepted picture of the native HF_aq-etched surface.

Keywords: PACS; 68.35.Md; 68.45.Da; 82.30.Hk; 82.65.My(1; 0; 0)Silicon; Hydrogen termination; Substoichiometric oxide; Angle-resolved X-ray photoelectron spectroscopy; Multiple-internal-reflection infrared spectroscopy; Atomic force microscopy

The crystallization and physical properties of Al-doped ZnO nanoparticles by K.J. Chen; T.H. Fang; F.Y. Hung; L.W. Ji; S.J. Chang; S.J. Young; Y.J. Hsiao (pp. 5791-5795).

Un-doped Al (0–9at.%) nanoparticles and doped ZnO powders were prepared by the sol–gel method. The nanoparticles were heated at 700–800°C for 1h in air and then analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectra and photoluminescence (PL). The results of un-doped (ZnO) and Al-doped ZnO (AZO) nanoparticles were also compared to investigate the structural characteristics and physical properties. XRD patterns of AZO powders were similar to those of ZnO powders, indicating that micro-Al ions were substituted for Zn atoms and there were no variations in the structure of the ZnO nanoparticles. From the XRD and SEM data, the grain size of the AZO nanoparticles increased from 34.41 to 40.14nm when the annealing temperature was increased. The Raman intensity of the AZO nanoparticles (Al=5at.%) increased when the annealing temperature was increased. Increasing the degree of crystalline not only reduced the residual stress, but also improved the physical properties of the nanoparticles.

Keywords: Sol–gel; ZnO; Crystallization

Microstructure, porosity and roughness of RF sputtered oxide thin films: Characterization and modelization by Fahd Oudrhiri-Hassani; Lionel Presmanes; Antoine Barnabé; Philippe Tailhades (pp. 5796-5802).

Spinel CoMnFeO₄ thin films are stable materials useful to study the influence of radio-frequency (RF) sputtering experimental conditions on the microstructure of oxide films. It has been demonstrated by various techniques such as electronic and atomic force microscopy (AFM), gas adsorption techniques and ellipsometry, that films prepared with 0.5Pa sputtering argon pressure and 5cm target–substrate distance are very dense. On the other hand, the samples obtained under higher pressure and/or longer distances are microporous with a mean pore size generally lower than 2nm. The specific surface areas of such films reach about 75m²/g.According to the simple model proposed, the films are made of three layers. From the bottom to the top of the film, the first one at the interface with the substrate is 100% dense. The second layer is made of cylindrical rods set up according to a compact plane. Its porosity is due to the lattice interstices. Hemispheric domes covering each rod make up the third layer, which displays a degree of roughness related to the shape and the hexagonal arrangement of the domes. The surface enhancement factor (SEF), the porosity and roughness, calculated from the model, are in corroboration with the experimental values. The porosity factor is however slightly underestimated by the model for very porous samples.

Keywords: PACS; 68.55.a; 61.15.Cd; 68.55.JkSpinel oxide; Thin films; Microstructure; Sputtering; Ellipsometry; Surface enhancement factor

Evolution of InP surfaces under low fluence pulsed UV irradiation by O.R. Musaev; O.S. Kwon; J.M. Wrobel; D.-M. Zhu; M.B. Kruger (pp. 5803-5806).

An InP wafer was irradiated in air by a series of UV pulses from a nitrogen laser with fluences of 120mJ/cm² and 80mJ/cm². These fluences are below the single-pulse ablation threshold of InP. Over the studied region the distribution of the radiation intensity was uniform. The number of pulses varied from 50 to 6000. The evolution of the surface morphology and structure was characterized by atomic force microscopy, optical microscopy and Raman spectroscopy. The relationship between mound size and the number of pulses starts out following a power law, but saturates for a sufficiently high number of pulses. The crossover point is a function of fluence. A similar relation exists for the surface roughness. Raman spectroscopic investigations showed little change in local crystalline structure of the processed surface layer.

Keywords: Indium phosphide; Laser damage; Surface morphology

Internal stresses and stability of the tetragonal phase in zirconia thin layers deposited by OMCVD by B. Benali; A.M. Huntz; M. Andrieux; M. Ignat; S. Poissonnet (pp. 5807-5813).

Zirconia thin films were deposited by OMCVD (organo-metallic chemical vapour deposition) at various temperatures and oxygen partial pressures on a AISI 301 stainless steel substrate with Zr(thd)₄ as precursor. The as deposited 250nm thin zirconia films presented a structure consisting of two phases: the expected monoclinic one and also an unexpected tetragonal phase. According to the literature, the stabilization of the tetragonal phase (metastable in massive zirconia) can be related to the crystallite size and/or to the generated internal compressive stresses.To analyze the effect of internal and external stresses on the thin film behaviour, in-situ tensile experiments were performed at room temperature and at high temperature (500°C).Depending on the process parameters, phase transformations and damage evolution of the films were observed. Our results, associated to XRD (X-ray diffraction) analyses, used to determine phase ratios and residual stresses within the films, before and after the mechanical experiments, are discussed with respect to their microstructural changes.

Keywords: Zirconia thin films; Tetragonal and monoclinic phases; Phase transformation; Tensile test; Annealing

Properties of NiO thin films deposited by chemical spray pyrolysis using different precursor solutions by L. Cattin; B.A. Reguig; A. Khelil; M. Morsli; K. Benchouk; J.C. Bernède (pp. 5814-5821).

NiO thin films have been deposited by chemical spray pyrolysis using a perfume atomizer to grow the aerosol. The influence of the precursor, nickel chloride hexahydrate (NiCl₂·6H₂O), nickel nitrate hexahydrate (Ni(NO₃)₂·6H₂O), nickel hydroxide hexahydrate (Ni(OH)₂·6H₂O), nickel sulfate tetrahydrate (NiSO₄·4H₂O), on the thin films properties has been studied. In the experimental conditions used (substrate temperature 350°C, precursor concentration 0.2–0.3M, etc.), pure NiO thin films crystallized in the cubic phase can be achieved only with NiCl₂ and Ni(NO₃)₂ precursors. These films have been post-annealed at 425°C for 3h either in room atmosphere or under vacuum. If all the films are p-type, it is shown that the NiO films conductivity and optical transmittance depend on annealing process. The properties of the NiO thin films annealed under room atmosphere are not significantly modified, which is attributed to the fact that the temperature and the environment of this annealing is not very different from the experimental conditions during spray deposition. The annealing under vacuum is more efficient. This annealing being proceeded in a vacuum no better than 10⁻²Pa, it is supposed that the modifications of the NiO thin film properties, mainly the conductivity and optical transmission, are related to some interaction between residual oxygen and the films.

Keywords: PACS; 68.55.Jk; 68.55.Nq; 81.15.Rs; 81.15.LmNickel oxide; Thin films; Spray pyrolysis; Transmittance; Conductivity

Diffusions of small clusters on Pt(111) and Cu(111) surfaces by Jianxing Jiang; Peng Zhang; Yiqun Xie; Xijing Ning; Min Zhuang; Yufen Li; Jun Zhuang (pp. 5822-5826).

Diffusions of small cluster Pt₆ on Pt(111) surface and Cu₆ on Cu(111) are studied by molecular dynamics simulation, respectively. The atomic interaction is modeled by the semiempirical potential. The results show that the diffusion processes in the two systems are far different. For example, on Pt(111) surface, the hopping of single atom and the shearing of two atoms of hexamer only occur on the adatom(s) adsorbed at B-step, while on Cu(111) surface they can appear on the adatom(s) either at A-step or B-step. To the concerted translation of the parallelogram hexamer, the anisotropy in the diffusion path is observed in the two systems, the mechanisms and then the preferential paths, however, are completely different. The reasons for these diffusion characteristics and differences are discussed.

Keywords: Surface diffusion; Clusters; Metallic surfaces; Molecular dynamics

A DFT study of H adsorption on Pt(111) and Pt–Ru(111) surfaces by Carolina Pistonesi; Estela Pronsato; Alfredo Juan (pp. 5827-5830).

In this work a comparative analysis between different Pt–Ru(111) surface models and pure Pt(111) surface is presented. Some aspects of the electronic structure of the surfaces and hydrogen adsorption are analysed based on density functional theory calculations. The hydrogen adsorption energy is significantly reduced when Ru is present on the surface. The substitution of Pt atoms by Ru atoms reinforce the Pt–H bond while the metal–metal bond is strongly modified, making the system less stable.

Keywords: PACS; 71.15.Mb; 73.20.At; 81.05.BxPt–Ru; Alloy; Hydrogen; DFT

c-C₅H₅ on a Ni(111) surface: Theoretical study of the adsorption, electronic structure and bonding by E. Germán; S. Simonetti; E. Pronsato; A. Juan; G. Brizuela (pp. 5831-5836).

In the present work the ASED-MO method is applied to study the adsorption of cyclopentadienyl anion on a Ni(111) surface. The adsorption with the centre of the aromatic ring placed above the hollow position has been identified to be energetically the most favourable. The aromatic ring remains almost flat, the H atoms are tilted 17° away from the metal surface. We modelled the metal surface by a two-dimensional slab of finite thickness, with an overlayer of c-C₅H₅⁻, one c-C₅H₅⁻ per nine surface Ni atoms. The c-C₅H₅⁻ molecule is attached to the surface with its five C atoms bonding mainly with three Ni atoms. The NiNi bond in the underlying surface and the CC bonds of c-C₅H₅⁻ are weakened upon adsorption. We found that the band of Ni5dz2 orbitals plays an important role in the bonding between c-C₅H₅⁻ and the surface, as do the Ni 6s and 6p_z bands.

Keywords: Ni(1; 1; 1); Cyclopentadienyl; Chemisorption; Molecular orbitals

Theoretical study of the influence of cation vacancies on the catalytic properties of vanadium antimonate by S. Messina; A. Juan; S. Larrondo; B. Irigoyen; N. Amadeo (pp. 5837-5843).

We have theoretically studied the influence of antimony and vanadium cation vacancies in the electronic structure and reactivity of vanadium antimonate, using molecular orbital methods. From the analysis of the electronic properties of the VSbO₄ crystal structure, we can infer that both antimony and vanadium vacancies increase the oxidation state of closer V cations. This would indicate that, in the rutile-type VSbO₄ phase the Sb and V cations defects stabilize the V in a higher oxidation state (V⁴⁺). Calculations of the adsorption energy for different toluene adsorption geometries on the VSbO₄(110) surface have also been performed. The oxidation state of Sb, V and O atoms and the overlap population of metal–oxygen bonds have been evaluated. Our results indicate that the cation defects influence in the toluene adsorption reactions is slight. We have computed different alternatives for the reoxidation of the VSbO₄(110) surface active sites which were reduced during the oxygenated products formation. These calculations indicate that the V cations in higher oxidation state (V⁴⁺) are the species, which preferentially incorporate lattice oxygen to the reduced Sb cations. Thus, the cation defects would stabilize the V⁴⁺ species in the VSbO₄ structure, determining its ability to provide lattice oxygen as a reactant.

Keywords: Oxidation catalysts; Vanadium antimoniate; Oxygen vacancies; Antimonium

Chemical synthesis of spinel nickel ferrite (NiFe₂O₄) nano-sheets by J.L. Gunjakar; A.M. More; K.V. Gurav; C.D. Lokhande (pp. 5844-5848).

The present investigation is related to the deposition of single-phase nano-sheets spinel nickel ferrite (NiFe₂O₄) thin films onto glass substrates using a chemical method. Nano-sheets nickel ferrite films were deposited from an alkaline bath containing Ni²⁺ and Fe²⁺ ions. The films were characterized for their structural, surface morphological and electrical properties by means of X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and two-point probe electrical resistivity techniques. The X-ray diffraction pattern showed that NiFe₂O₄ nano-sheets are oriented along (311) plane. The FT-IR spectra of NiFe₂O₄ films showed strong absorption peaks around 600 and 400cm⁻¹ which are typical for cubic spinel crystal structure. Microstructural study of NiFe₂O₄ film revealed nano-sheet like morphology with average sheet thickness of 30nm. The room temperature electrical resistivity of the NiFe₂O₄ nano-sheets was 10⁷Ωcm.

Keywords: Thin films; Spinel nickel ferrite (NiFe; ₂; O; ₄; ); Structural and surface morphological studies

From hexagonally arrayed nanorods to ordered porous film through controlling the morphology of ZnO crystals by Lan Ding; Zhang Yinmin; Wang Yuren (pp. 5849-5853).

The macrostructure can be changed by changing the morphology of its units. In this article, we use a colloidal template route, combined with hydrothermal growth method, to get the hexagonally arrayed ZnO nanorods on the polycrystalline ZnO substrate. More significantly, through controlling the morphology of ZnO crystals by adding structure-directing agent in the precursor solution, the highly ordered porous ZnO films were obtained instead of ZnO nanorods. This templated solvent-thermal method has great potential in micro/nano-fabrication.

Keywords: Macro-porous film; ZnO; Nanospace; Colloid template; Polystyrene spheres

Evaluating the use of laser radiation in cleaning of copper embroidery threads on archaeological Egyptian textiles by Omar Abdel-Kareem; M.A. Harith (pp. 5854-5860).

Cleaning of copper embroidery threads on archaeological textiles is still a complicated conservation process, as most textile conservators believe that the advantages of using traditional cleaning techniques are less than their disadvantages. In this study, the uses of laser cleaning method and two modified recipes of wet cleaning methods were evaluated for cleaning of the corroded archaeological Egyptian copper embroidery threads on an archaeological Egyptian textile fabric. Some corroded copper thread samples were cleaned using modified recipes of wet cleaning method; other corroded copper thread samples were cleaned with Q-switched Nd:YAG laser radiation of wavelength 532nm. All tested metal thread samples before and after cleaning were investigated using a light microscope and a scanning electron microscope with an energy dispersive X-ray analysis unit. Also the laser-induced breakdown spectroscopy (LIBS) technique was used for the elemental analysis of laser-cleaned samples to follow up the laser cleaning procedure. The results show that laser cleaning is the most effective method among all tested methods in the cleaning of corroded copper threads. It can be used safely in removing the corrosion products without any damage to both metal strips and fibrous core. The tested laser cleaning technique has solved the problems caused by other traditional cleaning techniques that are commonly used in the cleaning of metal threads on museum textiles.

Keywords: Archaeological copper threads; Q-switched Nd:YAG laser radiation; Cleaning methods; SEM-EDX; Laser-induced breakdown spectroscopy (LIBS)

Effect of nitrogen content on the properties of CrN_xO_yC_z coating prepared by DC reactive magnetron sputtering by Yongjing Shi; Siyuan Long; Liang Fang; Shicai Yang; Fusheng Pan (pp. 5861-5867).

The CrN_xO_yC_z coatings were deposited by planar DC reactive magnetron sputtering onto AZ31 Mg alloy and high speed tool steel (HSTS) substrates at a substrate temperature of 200°C. The effect of N₂ content on composition and structure of the CrN_xO_yC_z coatings was investigated. The structure of the CrN_xO_yC_z coatings was analyzed by a glancing angle X-ray diffraction (GXRD). The cross-section morphology and thickness of the CrN_xO_yC_z coatings were checked by a field emission scanning electron microscope (FESEM), and the composition profile and chemical state were carried out by an X-ray photoelectron spectroscopy (XPS). The experimental results showed that the structure and phase composition of the CrN_xO_yC_z coatings depended on N₂ content. The evolution of the structure of CrN_xO_yC_z coatings was consistent with CrN_x-based coatings, and the CrN_xO_yC_z coatings contained Cr₂O₃, CrO₂, CrO, Cr₃C₂, CrN_x (Cr, CrN, Cr₂N), as well as different chromium oxynitride. However, the carbide and oxynitride were oxidized after annealing.

Keywords: Magnetron sputtering; CrN; _x; O; _y; C; _z; coatings; Composition; Structure; Property; XPS

Influence of oxygen partial pressure on optoelectrical properties of aluminum-doped CdO thin films by R.K. Gupta; K. Ghosh; R. Patel; S.R. Mishra; P.K. Kahol (pp. 5868-5873).

Highly conducting and transparent aluminum-doped CdO thin films were deposited on quartz by ablating the sintered target of CdO containing 2wt% of aluminum with a KrF excimer laser ( λ=248nm and pulsed duration of 20ns). The effect of oxygen partial pressure on structural, electrical, and optical properties was studied. It is observed that the (200) plane is highly preferred for the films grown under high oxygen pressure. The conductivity, carrier concentration and mobility of the films decrease with increase in the oxygen pressure after attaining maximum. Low resistivity (2.27×10⁻⁵Ωcm), and high mobility (79cm²V⁻¹s⁻¹) is observed for the film grown under oxygen pressure of 1.0×10⁻³mbar. The optical band gap is found varying between 2.68 and 2.90eV for various oxygen pressure.

Keywords: PACS; 72.20; 78.66; 73.50J; 61.16CCadmium oxide; Pulsed laser deposition; Transparent electrode; Hall effect; Mobility

Direct laser interference patterning of multi-walled carbon nanotube-based transparent conductive coatings by M.R.S. Castro; A.F. Lasagni; H.K. Schmidt; F. Mücklich (pp. 5874-5878).

Topographical structures were created on the surface of multi-walled carbon nanotube-based coatings deposited on borosilicate glass using the direct laser interference patterning (DLIP) technique. Films made by multi-walled carbon nanotubes (MWNTs) dispersed in antimony-doped tin oxide (ATO) matrix and networks of MWNTs with both low and high adherence to the substrates were irradiated with one single laser pulse. Due to the high absorption coefficient of ATO, the film was completely removed at the interference maxima positions leading to periodic arrays of high quality on macroscopic areas. Additionally, increase of the laser fluence has produced wider ablated regions. Irradiation of high adherent networks of MWNTs produced a periodic porous structure, what has been attributed to the presence of adherence promoters in the film. On the other hand, MWNT networks with low adhesion to the substrate were strongly removed at the interference maxima positions. In this case, however, the fabricated periodic structures presented several defects that result from the poor adherence of the film to the substrate.

Keywords: Laser interference; Carbon nanotubes; Patterning; Coating

Effect of Ti doping on Ta₂O₅ stacks with Ru and Al gates by A. Paskaleva; M. Tapajna; E. Atanassova; K. Frohlich; A. Vincze; E. Dobročka (pp. 5879-5885).

The Ti-doped Ta₂O₅ thin films (<10nm) obtained by rf sputtering are studied with respect to their composition, dielectric and electrical properties. The incorporation of Ti is performed by two methods – a surface doping, where a thin Ti layer is deposited on the top of Ta₂O₅ and a bulk doping where the Ti layer is sandwiched between two layers of Ta₂O₅. The effect of the process parameters (the method and level of doping) on the elemental distribution in-depth of the films is investigated by the time of flight secondary ion mass spectroscopy (ToF-SIMS). The Ti and Ta₂O₅ are intermixed throughout the whole thickness but the layers are very inhomogeneous. Two sub-layers exist in all the samples — a near interfacial region which is a mixture of Ta-, Ti-, Si-oxides as well as TaSiO, and an upper Ti-doped Ta₂O₅ sub-layer. For both methods of doping, Ti tends to pile-up at the Si interface. The electrical characterisation is performed on capacitors with Al- and Ru-gate electrodes. The two types of MIS structures exhibit distinctly different electrical behavior: the Ru gate provides higher dielectric permittivity while the stacks with Al electrode are better in terms of leakage currents. The specific metal-dielectric reactions and metal-induced electrically active defects for each metal electrode/high- k dielectric stack define its particular electrical behavior. It is demonstrated that the Ti doping of Ta₂O₅ is a way of remarkable improvement of leakage characteristics (the current reduction with more than four orders of magnitude as compared with undoped Ta₂O₅) of Ru-gated capacitors which originates from Ti induced suppression of the oxygen vacancy related defects.

Keywords: PACS; 73.40.Qv; 68.55.aj; 73.61.Ng; 77.55.+fMetal/high-; k; dielectric stacks; Ta; ₂; O; ₅; DRAM; ToF-SIMS

Preparation of poly(ɛ-caprolactone)-based polyurethane nanofibers containing silver nanoparticles by Hyun Jeong Jeon; Jin Sook Kim; Tae Gon Kim; Jung Hyun Kim; Woong-Ryeol Yu; Ji Ho Youk (pp. 5886-5890).

In this study, poly(ɛ-caprolactone)-based polyurethane (PCL-PU) nanofibers containing Ag nanoparticles for use in antimicrobial nanofilter applications were prepared by electrospinning 8wt% PCL-PU solutions containing different amounts of AgNO₃ in a mixed solvent consisting of DMF/THF (7/3w/w). The average diameter of the pure PCL-PU nanofibers was 560nm and decreased with increasing concentration of AgNO₃. The PCL-PU nanofiber mats electrospun with AgNO₃ exhibited higher tensile strength, tensile modulus, and lower elongation than the pure PCL-PU nanofiber mats. Small Ag nanoparticles were produced by the reduction of Ag⁺ ions in the PCL-PU solutions. The average size and number of the Ag nanoparticles in the PCL-PU nanofibers were considerably increased after being annealed at 100°C for 24h. They were all sphere-shaped and evenly distributed in the PCL-PU nanofibers, indicating that the PCL-PU chains stabilized the Ag nanoparticles well.

Keywords: Poly(ɛ-caprolactone); Polyurethane; Electrospinning; Nanofiber; Silver nanoparticles; Antimicrobial nanofilter

Novel hydrophobic/hydrophilic patterning process by photocatalytic Ag nucleation on TiO₂ thin film and electroless Cu deposition by Shunsuke Nishimoto; Atsushi Kubo; Xintong Zhang; Zhaoyue Liu; Noriaki Taneichi; Toshiki Okui; Taketoshi Murakami; Takashi Komine; Akira Fujishima (pp. 5891-5894).

A hydrophobic/super-hydrophilic pattern was prepared on a TiO₂ thin film by a new fabrication process. The process consists of five key steps: (1) photocatalytic reduction of Ag⁺ to Ag (nucleation), (2) electroless Cu deposition, (3) oxidation of Cu to CuO, (4) deposition of a self-assembled monolayer (SAM), and (5) photocatalytic decomposition of selected areas of the SAM. A hydrophobic/super-hydrophilic pattern with 500-μm² hydrophilic areas was obtained in this process. It is particularly noteworthy that a UV irradiation time of only 1s was sufficient for the nucleation step in the patterning process.

Keywords: PACS; 81.65.CfTiO; ₂; photocatalyst; Super-hydrophilic; Hydrophobic; Surface patterning

Structural, optical and electrochromic properties of Nb-doped MoO₃ thin films by S.S. Mahajan; S.H. Mujawar; P.S. Shinde; A.I. Inamdar; P.S. Patil (pp. 5895-5898).

Niobium (Nb) doped molybdenum trioxide (MoO₃) thin films have been synthesized using spray pyrolysis deposition technique. The structural changes were observed with the help of X-ray diffraction technique. With increasing Nb concentration, the structure of MoO₃ undergoes a phase transformation from α-orthorhombic to amorphous with nano-sized grains. The thread like reticulated morphology is converted into spongy like structure at higher Nb concentration (9at% Nb). It is seen that Nb doping can lead to significant surface morphology changes in MoO₃ films. It was found that the coloration efficiency increases with doping concentration. With increasing Nb concentration charge capacity, reversibility and electrochemical stability increases. The improvement is attributed to the amorphous structure of the doped samples that favors easy intercalation and deintercalation processes. Hence, we have successfully demonstrated formation of an adequate host for electrochromic devices with Nb (9at%) doped MoO₃ samples.

Keywords: Molybdenum oxide; Spray pyrolysis; Thin films; Structural; Optical and electrochemical properties

Fabrication of a superhydrophobic ZnO nanorod array film on cotton fabrics via a wet chemical route and hydrophobic modification by Bi Xu; Zaisheng Cai (pp. 5899-5904).

A superhydrophobic ZnO nanorod array film on cotton substrate was fabricated via a wet chemical route and subsequent modification with a layer of n-dodecyltrimethoxysilane (DTMS). The as-obtained cotton sample was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), scanning probe microscope (SPM) and X-ray photoelectron spectroscopy (XPS), respectively. The wettability of the cotton fabric sample was also studied by contact angle measurements. The modified cotton fabrics exhibited superhydrophobicity with a contact angle of 161° for 8μL water droplet and a roll-off angle of 9° for 40μL water droplet. It was shown that the proper surface roughness and the lower surface energy both played important roles in creating the superhydrophobic surface, in which the Cassie state dominated.

Keywords: PACS; 81.07.−b; 81.10.Dn; 81.16.Dn; 81.65.PsSuperhydrophobicity; Cotton fabrics; ZnO; Hydrothermal treatment

A new hydrothermal blackening technology for Fe₃O₄ coatings of carbon steel by Hongliang Zhu; Fahe Cao; Diantai Zuo; Luming Zhu; Dalai Jin; Kuihong Yao (pp. 5905-5909).

This paper proposes a new blackening technology for growing magnetite (Fe₃O₄) coating on surface of carbon steel. Dense black coating composed of Fe₃O₄ ultrafine particles could be successfully prepared by hydrothermal treatment of the carbon steel substrate in the N₂H₄·H₂O–FeSO₄–NaOH solution at 150°C. Electrochemical analysis, including Tafel and electrochemical impedance spectroscopy, indicated that the anodic dissolution reaction was effectively limited and the corrosion resistance increased by the Fe₃O₄ coating. The key factors and growth mechanism for the hydrothermal formation of the Fe₃O₄ coating are also discussed.

Keywords: Magnetite coating; Hydrothermal method; Blackening; Carbon steel

Effect of pulse electrodeposition parameters on the properties of Ni/nano-SiC composites by P. Gyftou; E.A. Pavlatou; N. Spyrellis (pp. 5910-5916).

Pure nickel and nickel matrix composite deposits containing nano-SiC particles were produced under both direct and pulse current conditions from an additive-free nickel Watts’ type bath. It has been proved that composite electrodeposits prepared under pulse plating conditions exhibited higher incorporation percentages than those obtained under direct plating conditions, especially at low duty cycles. The study of the textural perfection of the deposits revealed that the presence of nano-particles led to the worsening of the quality of the observed [100] preferred orientation. Composites with high concentration of embedded particles exhibited a mixed crystal orientation through [100] and [211] axes. The embedding SiC nano-particles in the metallic matrix by an intra-crystalline mechanism resulted in the production of composite deposits with smaller crystallite sizes and more structural defects than those of pure Ni deposits. A dispersion-hardening effect was revealed for composite coatings independently from applied current conditions. Pulse electrodeposition significantly improved the hardness of the Ni/SiC composite deposits, mainly at low duty cycle and frequency of imposed current pulses.

Keywords: PACS; 81.15.Pq; 81.05.Ni; 82.45.Yz; 68.55.Jk; 62.20.QpNickel electrodeposition; Composite; Silicon carbide; Pulse plating; Preferred orientation; Microhardness

Fabrication of ZnO/Al₂O₃ core–shell nanostructures and crystalline Al₂O₃ nanotube by Jingyun Huang; Sha Liu; Ye Wang; Zhizhen Ye (pp. 5917-5920).

We have demonstrated the crystalline ZnO–Al₂O₃ core–shell nanowire structure by atomic layer deposition (ALD) at a temperature 100°C. The core–shell structure could have potential applications in the fabrication of ZnO field effect transistor. After dissolving the ZnO core, shape defined, rigid and robust crystalline Al₂O₃ shelled nanostructures have been fabricated. Nanowire ZnO nanostructures have been replicated by alumina shell. This is one of the most effective techniques for producing core–shell or shell/hollowed nanostructures of any desired objects. The Al₂O₃ shelled nanostructures could have potential applications as space confined nanoreactors, drug delivery, nanofluidic channels and optical transmitting.

Keywords: PACS; 81.05.DzZinc oxide; Alumina; Core–shell nanostructure; Atomic layer deposition

Langmuir probe investigation of surface contamination effects on metals during femtosecond laser ablation by G.O. Williams; G.M. O’Connor; P.T. Mannion; T.J. Glynn (pp. 5921-5926).

Characterisation of the plasma plume induced by femtosecond laser–metal interactions has been carried out using a Langmuir probe. A double peak distribution of ablated ions and electrons has been recorded during time of flight (TOF) experiments for three metals studied (Ag, Cu and Ni). The first peak which occurs earliest in time is attributed to a surface layer of contaminants on the metal surface as it is shown to disappear after several laser shots. The re-growth of this peak, thought to be due to a recontamination process on the surface of the metal, is the subject of this paper. Two re-contamination mechanisms were considered; adsorption of contaminants from the ambient gas, and surface diffusion effects from the surrounding contaminants. Re-contamination rates for Ag, Cu and Ni were studied under two distinct gas pressures to investigate the contamination effects from the ambient. Effects arising from surface diffusion were investigated by raising the temperature of the metal sample to increase the surface mobility of the contaminants. The total contribution of contamination species present in the ablation plume was estimated by conducting angular distribution measurements of the plume. Surface diffusion of the surrounding contaminants was found to be the dominant recontamination process.

Keywords: PACS; 52.38.MfFemtosecond laser; Langmuir probe; Ablation; Contamination; Plasma; Surface diffusion

Adsorption and kinetic studies of L-leucine as an inhibitor on mild steel in acidic media by Puja Singh; Kalpana Bhrara; Gurmeet Singh (pp. 5927-5935).

L-Leucine is evaluated as a potential inhibitor for mild steel in acidic medium by galvanostatic polarization and potentiostatic polarization techniques. The electrochemical results were supplemented by scanning electron microscopy (SEM) and infrared studies (IR).The electrochemical polarization results show that L-leucine is most effective at 10⁻¹M concentration at room temperature (298K). The efficiencies were found to decrease with decrease in concentration and increase in temperature. Electrochemical results also show that L-leucine acts as a mixed type of inhibitor (blocks the cathodic and anodic sites to same extent) which is evident from insignificant shift of open circuit potential.Potentiostatic polarization data shows that they are passivating type of inhibitors. The effect of this inhibitor on anodic reaction is mainly attributed to physical adsorption of the additive on the anodic metal surface and the electron pairs on oxygen atoms. This additive exists in the protonated form (a positive charge on nitrogen atom) in the present acid medium. Therefore, on the cathodic sites, the interaction between additive and metal surface is thought to be electrostatic in nature.The results of SEM and IR data supplement the results obtained by electrochemical techniques.

Keywords: Hot rolled mild steel IS226; Acid corrosion; L; -Leucine

Fabrication of protective tantalum carbide coatings on carbon fibers using a molten salt method by Z.J. Dong; X.K. Li; G.M. Yuan; Y. Cong; N. Li; Z.J. Hu; Z.Y. Jiang; A. Westwood (pp. 5936-5940).

Protective tantalum carbide (TaC) coatings were fabricated successfully on carbon fibers in the temperature range of 950–1100°C using a molten salt method. A salt mixture composed of LiCl–KCl–KF was used as a reaction medium in which the tantalum and the carbon fiber substrates reacted to form the TaC coatings. The structure and morphology of the TaC coatings were characterized by XRD, SEM and EDX analyses. The results show that the reaction temperature and time have significant influence on the thickness, integrity and surface morphology of the TaC coatings. A uniform, adherent and crack-free TaC coating can be obtained by controlling the reaction temperature and time. Thermo-gravimetric analysis indicated that the oxidation resistance of the carbon fibers was improved remarkably by coating them with a high-quality TaC layer.

Keywords: TaC; Coating; Carbon fiber; Molten salt method

Properties of Zn₃N₂-doped ZnO films deposited by pulsed laser deposition by J.M. Erie; Y. Li; M. Ivill; H.S. Kim; S.J. Pearton; B. Gila; D.P. Norton; F. Ren (pp. 5941-5945).

The optical properties of N-doped ZnO films grown by pulsed laser deposition are examined for which zinc nitride is used as the source of nitrogen. The motivation for this study is to determine if nitrogen-related acceptor state formation can be achieved in ZnO films using Zn₃N₂ doping in the ablation target. The films were deposited in oxygen or nitrogen on c-plane sapphire. Photoluminescence measurements at 20K reveal a 3.31eV acceptor-bound exciton emission due to nitrogen substitution on the oxygen site, donor–acceptor pair emission at 3.23±1eV and free electron-acceptor at 3.27eV. The binding energy of the N-related acceptor is estimated to be in the range of 170–15meV. While the as-deposited films were n-type, thermal annealing in oxygen yielded insulating behavior, consistent with compensating acceptor states.

Keywords: Zinc oxide; Pulsed laser deposition; Doping; Oxides

Langmuir and Langmuir–Blodgett (LB) films of tetrapyridyl metalloporphyrins by F.J. Pavinatto; A.F. Gameiro Jr.; A.A. Hidalgo; L.R. Dinelli; L.L. Romualdo; A.A. Batista; N.M. Barbosa Neto; M. Ferreira; O.N. Oliveira Jr. (pp. 5946-5952).

We report on the formation of Langmuir films of 5,10,15,20-tetra(4-pyridyl) 21 H,23 H-porphine, hereafter named tetrapyridyl porphyrins with distinct central ions (2H⁺, Zn²⁺, Cu²⁺, Ni²⁺). The films were characterized with surface pressure and surface potential isotherms and in situ UV–vis absorbance. The measurements indicated strong aggregation of porphyrin monomers at the air–water interface, with a red shift of the Soret band in comparison with the spectrum obtained from CHCl₃ solutions. The shift was larger for the non-substituted H₂TPyP, and depended on the metal ion. Significantly, aggregation occurred right after spreading of the Langmuir film, with no further shifts in the UV–vis spectra upon compression of the film, or even after transferring them onto solid substrates in the form of Langmuir–Blodgett (LB) films. The buildup of LB films from H₂TPyP and ZnTPyP was monitored with UV–vis spectroscopy, indicating an equal amount of material deposited in each deposition step. Using FTIR in the transmission and reflection modes, we inferred that the H₂TPyP molecules exhibit no preferential orientation in the LB films, while for ZnTPyP there is preferential orientation, with the porphyrin molecules anchored to the substrate by the lateral pyridyl groups.

Keywords: Tetrapyridyl porphyrins; Langmuir films; Langmuir–Blodgett films

Improvement of erosion and erosion–corrosion resistance of AISI420 stainless steel by low temperature plasma nitriding by Xi Yun-tao; Liu Dao-xin; Han Dong (pp. 5953-5958).

Plasma nitriding experiments were carried out with DC-pulsed plasma in 25% N₂+75% H₂ atmosphere at low temperature (350°C) and normal temperature (550°C) for 15h. The composition, microstructure, microhardness profiles, residual stress profiles and electrochemical impedance spectrum analyses of the nitrided samples were examined. The influence of plasma nitriding on the erosion and erosion–corrosion resistance of AISI 420 martensitic stainless steel was investigated using a jet solid particle erosion tester and a slurry erosion–corrosion tester.Results showed that the 350°C nitriding layer was dominated by ɛ-Fe₃N and α_N phase, a supersaturated nitrogen solid solution. However, nitrogen would react with Cr in the steel to form CrN precipitates directly during 550°C nitriding, which would lead to the depletion of Cr in the solid solution phase of the nitrided layer. Both 350 and 550°C plasma nitriding could improve the erosion resistance of AISI420 stainless steel under dry erosion, but the former showed better results. In both neutral and acid environment, while the erosion–corrosion resistance of AISI 420 was improved by means of 350°C nitriding, it was decreased through 550°C nitriding.

Keywords: Plasma nitriding; Stainless steel; Erosion; Erosion–corrosion

Atom-sensitive textiles as visual indicators for plasma post-discharges by Cristina Canal; Sandrine Villeger; Sarah Cousty; Benoit Rouffet; Jean-Philippe Sarrette; Pilar Erra; André Ricard (pp. 5959-5966).

The efficiency of surface treatments by plasma and post-discharge plasma processes is greatly dependent on the density of active species, such as neutral atoms in post-discharges. Therefore, many diagnostics exist to detect the presence and measure the concentrations of these species, but they often require expensive instrumentation and highly qualified personnel. These conditions are not often met when the process is industrially used and it becomes important to imagine simple indicators allowing to validate that the correct operating conditions are reached. In the present paper, we present the first results on the investigation of an inexpensive and easy to use visual indicator able to quantify the atomic species density in nitrogen post-discharge plasma processes. It is based on the differential recombination coefficients of N-atoms on metallic/textile fibres which are intrinsically bonded together in a fabric matrix which serves as support for a thermochromic ink. The specific heating of the metallic fibres by N-atom recombination heats the whole of the fabric, leading to a visible colour change of the thermochromic ink, and therefore, of the indicator. Through modelling, it was possible to estimate that the inclusion of copper fibres to a pure cotton matrix leads to a 60% increase of the global N-atom recombination coefficient of the fabric, sufficient enough to provide a clearly visible colour change.

Keywords: PACS; 52.70.−m Plasma diagnostic techniques and instrumentation; 82.33.Xj Afterglow (plasma reactions)Downstream plasma; Process control; Optical emission spectroscopy; Thermochromism; Textiles; Process indicators

Facile synthesis and characterization of acid–base bifunctionalized mesoporous silica by Ying Chen; Jinyu Han; Haitao Zhang (pp. 5967-5974).

A simple acid–base bifunctionalized approach has been developed through grinding the precursors, magnesium and aluminium nitrates, with the as-prepared SBA-15, and then the generation of acid–base active sites and removal of host template were combined into a single step in the subsequent calcination procedure. A series of acid–base bifunctional mesoporous materials MgO–Al₂O₃–SBA-15 (MA–SBA-15) have been successfully synthesized by means of this approach. X-ray diffraction (XRD), high-resolution transmission electron microscopes (HRTEMs), N₂ adsorption, FT-IR spectra,²⁷Al and²⁹Si magic-angle-spinning (MAS) NMR, NH₃- and CO₂-temperature programmed desorption (TPD), pyridine adsorption were employed to characterize the resultant mesoporous materials. The results indicate that the guests can be well dispersed in the channel of SBA-15, and the resultant materials exhibit excellent acid-basic properties with well mesoporous backbone, which make it possessing high activity for the synthesis of ethyl methyl carbonate, an important asymmetric carbonate ester compound.

Keywords: Mesoporous materials; Acid–base properties; MgO–Al; ₂; O; ₃; –SBA-15; Surface functionalization

Structure and infrared emissivity of collagen/SiO₂ composite by Xiaoyun Ye; Yuming Zhou; Yanqing Sun; Jing Chen; Zhiqiang Wang (pp. 5975-5980).

Collagen/SiO₂ composites were prepared in aqueous suspensions. Adsorption behaviors of collagen onto the surfaces of SiO₂ spheres were studied. Structure and thermal properties were measured with FTIR, SEM, TEM, and TGA-DTA. The results showed that the self-aggregation of collagen macromolecules was taken place during the adsorption of collagen on SiO₂ sphere. The morphology of collagen evolved from line to microfibrils with the increase in the concentration of collagen along with the distortion of SiO₂. Interfacial interactions of electrostatic forces and hydrogen bonding between the collagen macromolecule and SiO₂ sphere had a vital effect on the adsorption of collagen. The amount of the collagen adsorption was increased with the increase of the collagen concentration, yet decreased in increased pH value of the solution. It was found that the composites exhibited lower infrared emissivity values in the wavelength ranged from 8 to 14μm than not only pure collagen but also SiO₂ sphere, and the value of infrared emissivity was related to the adsorption amount of collagen in the composites.

Keywords: Collagen; SiO; ₂; Composite; Infrared emissivity

Characterization of water exposed plasma sprayed oxide coating materials using XPS by Mika Harju; Sami Areva; Jarl B. Rosenholm; Tapio Mäntylä (pp. 5981-5989).

The surface compositions and oxidation states of non-exposed and water exposed plasma sprayed oxide coatings were studied using X-ray photoelectron spectroscopy (XPS). Coating materials were TiO₂, Al₂O₃ and Cr₂O₃ and their mixtures. Water exposures were performed for free standing coating disks at mild electrolyte (1mmol NaCl solution) at pH 4, 7 and 9. The exposure time was two weeks.It was observed that pure plasma sprayed TiO₂ material was chemically stable over whole experiment pH range and only slight surface hydroxylation was observed for this material.In case of plasma sprayed Al₂O₃ materials the surface O/Al ratio increased considerably during water exposure especially at exposure pH 7. This was probably result of surface conversion to hydrous form. No surface oxidation state changes were observed for this material.The non-exposed Cr₂O₃ materials contained both Cr(III) and Cr(VI) oxides. The water exposures increased the surface oxygen and Cr(VI) contents at the expense of Cr(III). The most probable reason for that was the dissolution of surface Cr(VI) oxide phase during water exposures and the (re)adsorption of dissolved Cr(VI) species back to the surface.

Keywords: PACS; 81.15.Rs; 73.20.−r; 79.60.−iPlasma spraying; Surface states; X-ray photoelectron spectra in surface analysis

Impact of organic contamination on laser-induced damage threshold of high reflectance coatings in vacuum by Yun Cui; Yuanan Zhao; Hua Yu; Hongbo He; Jianda Shao (pp. 5990-5993).

The influence of organic contamination in vacuum on the laser-induced damage threshold (LIDT) of coatings is studied. TiO₂/SiO₂ dielectric mirrors with high reflection at 1064nm are deposited by the electron beam evaporation method. The LIDTs of mirrors are measured in vacuum and atmosphere, respectively. It is found that the contamination in vacuum is easily attracted to optical surfaces because of the low pressure and becomes the source of damage. LIDTs of mirrors have a little change in vacuum compared with in atmosphere when the organic contamination is wiped off. The results indicate that organic contamination is a significant reason to decrease the LIDT. N₂ molecules in vacuum can reduce the influence of the organic contaminations and prtectect high reflectance coatings.

Keywords: PACS; 42.79.Wc; 68.60.−p; 78.67.PtOptical coatings; Laser-induced damage threshold; Organic contamination; Vacuum; Atmosphere; Protective gas

Investigation into the photo-induced change in wettability of hydrophobized TiO₂ films by Gunter Risse; Sabine Matys; Horst Böttcher (pp. 5994-6001).

The photo-induced change in wettability of hydrophobized TiO₂ films has been investigated for steel coated with acidic TiO₂ nanosols containing varying concentrations of dispersed nanocrystalline titania, such as Degussa P25. The photo-induced change in wettability was evaluated by measuring the time-dependent drop of water contact angle (WCA) after samples had been soaked in either n-octyltriethoxysilane (OTS) or decanoic acid (DA). TiO₂ films treated in this way exhibit superhydrophobic behaviour, with WCA greater than 160°. After radiation with UV (black light), the superhydrophobic properties are transformed into superhydrophilic properties, with WCA of almost 0°. As P25 content and layer thickness increase, high rates of photo-induced change are found, but a moderate calcination regime is required. On the other hand, hardness and E modulus pass through a maximum at 25wt% P25, so that a P25 content between 25 and 50wt% is the optimum for practical uses. With such stable coatings, wettability can be controlled over a wide range, and the switch between hydrophobic and hydrophilic states can be carried out repeatedly when DA is used as the hydrophobizing agent. Use of a low calcination temperature (450°C) for the intermediate annealing of the single layers in multilayer coatings and a short final sintering step at a relatively high temperature (e.g. 630°C for 10min) allow the preparation of relatively thin TiO₂ films on steel with a high photoactivity.

Keywords: Nanocrystalline titania; Thin films; Photocatalytic activity; Switchable wettability

Separating small amount of water and hydrophobic solvents by novel superhydrophobic copper meshes by Qinmin Pan; Min Wang; Hongbo Wang (pp. 6002-6006).

A novel filtration device for the separation of small amount of water and hydrophobic solvents was proposed, and its separation efficiency was also quantitatively studied for the first time. This goal was achieved by a copper mesh with superhydrophobic and superoleophilic properties, which was fabricated by simply immersing in aqueous solution of NaOH and K₂S₂O₈, and subsequent modification with n-dodecanethiol. The results demonstrated that a slightly tilted copper mesh could separate small amount of hydrophobic solvents and water with high efficiency. This finding provides a new strategy to the development of functional filtration devices that may have many potential applications in the field such as biomedicine, microanalysis, purification, etc.

Keywords: Water and solvents mixture; Separation device; Superhydrophobic copper mesh; Separation efficiency

Erratum to “XPS study of five fluorinated compounds deposited on calcarenite stone. Part I: Unaged samples” [Appl. Surf. Sci. 254 (9) (2008) 2650–2658] by Alberto Torrisi (pp. 6007-6007).

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Applied Surface Science (v.254, #18)