Applied Surface Science (v.285, #PB)

Crystallization of amorphous Ge2Sb2Te5 films induced by an ultraviolet laser by W.P. Zhou; F.R. Liu; N. Bai; Y.H. Wan; X. Lin; J.M. Chen (97-101).
The laser wavelength plays an important role in achieving high density in optical storage. Previous studies on the phase transition were mainly focused on the range from infrared to visible waveband. In this work, crystallization of amorphous Ge2Sb2Te5 thin film induced by an ultraviolet laser with the wavelength of 248 nm was investigated. The crystallization behavior of Ge2Sb2Te5 thin films was analyzed using X-ray diffraction, atomic force microscopy, Raman scattering and scanning electron microscope. Based on the X-ray diffraction pattern results, the phase transition from the amorphous Ge2Sb2Te5 to the face-centered cubic crystallized Ge2Sb2Te5 was obtained with the laser fluence in the range of 24.4–66.6 mJ/cm2. Atomic force microscopy images showed that the inhomogeneous crystalline structure with the grain size ranging from tens of nanometer to 250 nm was produced in spite of the lower laser fluence of 24.4 mJ/cm2. This structure can be attributed to the ultrafast violet laser radiance. A new peak at 140 cm−1 caused by the segregation of Te crystalline was possibly due to the higher photon energy absorbed by the ultraviolet laser radiance. This work is of significance for the optical storage in developing new applications by ultraviolet laser.
Keywords: Crystallization; Phase-change material; Ge2Sb2Te5; Ultraviolet laser;

Density functional theory (DFT) calculations were carried out to analyze the electronic and structural properties of pristine and aluminum or phosphorus doped (8,0) single walled carbon nanotube (SWCNT) as a sensor for the detection of nitrogen dioxide (NO2) and ammonia (NH3). The binding energies, equilibrium gas-nanotube distances, the amounts of charge transfer and molecular orbital schemes as well as the density of states have been calculated and used to interpret the mechanism of gas adsorption on the surface of nanotubes. In agreement with the experimental data, our results show considerable binding energy and energy gap alteration due to the adsorption of NO2 on pristine SWCNT. The results reveal that the doping of both Al and P atoms increase the capability of the nanotube for the adsorption of NO2, and the effect is more significant for the Al-doped nanotube. The Al-doped nanotube can also be considered as a good sensor for NH3 due to its high binding energy, considerable amount of charge transfer and energy band gap alteration.
Keywords: Ammonia; Nitrogen dioxide; Sensor; SWCNT; DFT;

A novel photoemission technique utilising localised discharge amplification of photo-yield is reported. It enables fast, accurate measurement of work function and ionisation potential for ultra-thin buffer layers vacuum deposited onto single and multilayer transparent conducting electrodes for organic solar cells and OLED's. Work function in most traditional transparent electrodes has to be raised to maximise charge transfer while high transmittance and high conductance must be retained. Results are presented for a range of metal oxide buffers, which achieve this goal. This compact photo-yield spectroscopy tool with its fast turn-around has been a valuable development aid since ionisation potential can vary significantly as deposition conditions change slightly, and as ultra-thin films grow. It has also been useful in tracking the impact of different post deposition cleaning treatments along with some storage and transport protocols, which can adversely reduce ionisation potential and hence subsequent device performance.
Keywords: Photo-emission; Ionisation potential; Discharge amplification; Transparent electrodes; OPV/OLED;

Structure and surface effect of field emission from gallium nitride nanowires by Y.Q. Wang; R.Z. Wang; M.K. Zhu; B.B. Wang; B. Wang; H. Yan (115-120).
Gallium nitride nanowires (GaN NWs) were synthesized by plasma-enhanced hot filament chemical vapor deposition under different ratios of nitrogen to hydrogen, which the GaN powder and nitrogen gas were used as the Ga and N sources. The characterization results indicate that the GaN NWs are grown in wurtzite crystalline structure with different length, diameters and surface adsorption. The field emission of GaN NWs was measured in the high vacuum condition of ∼10−6  Pa, which the results show that the turn-on field of GaN NWs changes from 0.86 to 2.8 V/μm depending on their structures and the current density can reach up to 830 μA/cm2 at the field of 6 V/μm. Combined the characterization results with the work function theory related to field emission, the origin of the field emission enhancement was analyzed, which associates with their surface potential and geometric structure. These results can enrich our knowledge on the field emission of GaN NWs and are highly related to the development of the next-generation of GaN nano-electronic devices.
Keywords: GaN nanowires; Field emission; Joule heat effect; Work function; Surface adsorption;

In order to search for an efficient photocatalysts working under visible light illumination, we have investigated the effect of metal and nonmetal ions (In, S) codoping on the photocatalytic activity of TiO2 nanoparticles (TiO2 NPs) prepared by combining of sol–gel (SG) and photodeposition (PD) methods using titanium tetra isopropoxide (TTIP), indium nitrate (In(NO3)3) and thiourea as precursors. In this regard, at first three different percentage of S (0.05, 0.2 and 0.5) doped into the TiO2 by SG method, and then different amount of In(III) loaded on the surface of the prepared samples by PD technique. The results showed that the In, S-codoped TiO2 (In, S-TiO2) with a spheroidal shape demonstrates a smaller grain size than the pure TiO2. Meanwhile, the UV–vis DRS of In, S-TiO2 showed a considerable red shift to the visible region. Finally, the photocatalytic activity of In, S-TiO2 photocatalysts were evaluated by photooxidative degradation of methyl orange (MO) solution under UV and visible light illumination. As a result, it was found that 0.05%S-0.5%In/TiO2, 0.2%S-1.5%In/TiO2 and 0.5%S-0.5%In/TiO2 had the highest catalytic activity under visible light in each group and among these samples 0.2%S-1.5%In/TiO2 showed the best photocatalytic performance under visible light and decomposes more than 95% MO in only 90 min.
Keywords: Sol–gel; Photodeposition; In, S-TiO2, MO degradation; Visible light;

Synthesis of self-assembled 3D hollow microspheres of SnO2 with an enhanced gas sensing performance by Yangen Li; Liang Qiao; Lili Wang; Yi Zeng; Wuyou Fu; Haibin Yang (130-135).
Formation process of the hierarchical SnO2 hollow spheres.In this paper, three-dimensional (3D) SnO2 hollow microspheres composed of numerous subunits of nanorods are prepared through a facile one-pot hydrothermal method. These SnO2 microspheres are structurally characterized by X-ray diffraction, field-emission scanning electron microscope, and high resolution transmission electron microscope, respectively. It is shown that the hierarchical SnO2 microspheres ranged from 600 to 900 nm in diameter are constructed from self-assembled one-dimensional tetragonal prism SnO2 nanorods. Most importantly, the gas sensor based on these hierarchical SnO2 microspheres exhibits excellent selectivity and fast response–recovery capability to ethanol. The response and recovery times are 2.6 s and 11 s, respectively, if the sensor is exposed to 50 ppm ethanol at the optimal operating temperature of 280 °C. The present study could offer potential applications in gas sensors.
Keywords: SnO2; Hierarchical nanostructures; Formation mechanism; Gas sensor;

Enhancing coating of brushite/hydroxyapatite layer on titanium alloy implant surface with additives by E.A. Abdel-Aal; D. El-Sayed; M. Shoeib; A.T. Kandil (136-143).
Brushite (CaHPO4·2H2O) was electrodeposited on titanium alloy substrate with and without H2O2. It was converted to hydroxyapatite [Ca10(PO4)6(OH)2] by NaOH treatment. Different H2O2 and NH4OH doses ranging from 0 ppm to 2400 ppm and from 0 ppm to 7000 ppm, respectively were used. The results showed that with increasing H2O2 dose up to 600 ppm, the weight gain and the coating thickness are increased. Further increase of H2O2 dose led to decrease of the weight gain and the coating thickness. Addition of ammonia led to decrease of the weight gain and the coating thickness. Thickness and weight gain of coated brushite layer are decreased with sodium hydroxide treatment and converted totally to hydroxyapatite. Coating thickness at Ca/P ratio of 1.67 and coating time of 1 h at current density of 1.5 mA/cm2 was about 14 and 18.5 μm without and with 600 ppm H2O2, respectively. It decreased to about 8 μm with addition of 7000 ppm ammonia solution.
Keywords: Hydroxyapatite; Calcium phosphate coatings; Hydroxyapatite coatings; Surface treatment;

Portuguese tin-glazed earthenware from the 16th century: A spectroscopic characterization of pigments, glazes and pastes by L.F. Vieira Ferreira; I. Ferreira Machado; A.M. Ferraria; T.M. Casimiro; Ph. Colomban (144-152).
Sherds representative of the Portuguese faience production of the early-16th century from the “Mata da Machada” kiln and from an archaeological excavation on a small urban site in the city of Aveiro (from late 15th to early 16th century) were studied with the use of non-invasive spectroscopies, namely: ground state diffuse reflectance absorption (GSDR), micro-Raman, Fourier-transform infrared (FT-IR) and proton induced X-ray (PIXE). These results were compared with the ones obtained for two Spanish productions, from Valencia and Seville, both from same period (late 15th century and 16th century), since it is well know that Portugal imported significant quantities of those goods from Spain at that time.The obtained results evidence a clear similarity in the micro-Raman spectrum in the glaze and clays of Portuguese pottery produced at “Mata da Machada” and sherds found at the mediaeval house of Homem Cristo Filho (HCF) street at Aveiro.The blue pigment in the sample from the household of Aveiro is a cobalt oxide that exists in the silicate glassy matrix in small amounts, which did not allow the formation of detectable cobalt silicate microcrystals. White glaze from Mata da Machada and Aveiro evidence tin oxide micro-Raman signatures superimposed on the bending and stretching bands of SiO2.All these are quite different from the Spanish products under study (Seville and Valencia), pointing to an earlier production of tin glaze earthenware in Portugal than the mid 16th century, as commonly assumed.
Keywords: Pottery; Ground state diffuse reflectance absorption spectroscopy; Raman micro-spectroscopy; Fourier-transform infrared spectroscopy; Particle induced X-ray spectroscopy; X-ray fluorescence spectroscopy;

Interface formation between an ultra thin MgO layer and the selenium passivated InAs surface has been investigated by soft X-ray photoemission spectroscopy. Atomic hydrogen cleaning of the native oxide covered InAs at 360 °C produced an oxide and carbon free InAs surface. The selenium passivation of the atomically clean InAs showed evidence of arsenic replacement in the near surface region. Subsequent MgO deposition resulted in the appearance of an oxidized indium signal indicating that the bonding interaction between the MgO and the substrate is via indium–oxide bond formation. The conduction and valence band offsets were also estimated for this dielectric–semiconductor structure.
Keywords: Core level photoemission; InAs surface cleaning; Selenium passivation; High-k deposition;

The optical and electrical properties of indium tin oxide (ITO) thin films deposited on flexible polyethylene terephthalate (PET) substrates using a DC magnetron sputtering technique are investigated as a function of the deposition time, the argon flow rate and the target–substrate distance. It is found that all of the ITO films contain a high fraction of amorphous phase. The volume fraction of crystallite precipitates in the amorphous host increases with an increasing deposition time or a reducing argon flow rate. The deposition time and argon flow rate have higher effects on the optical transparency of the ITO films than the target–substrate distance has. Increasing film thickness is not the only reason for the transmittance reduced. It is found that an increase of the extinction coefficient by increasing deposition time or an increase of the refractive index by decreasing argon flow rate also reduces the transmittance of thin film. For a constant deposition time, the resistivity of the ITO films reduces with a reducing argon flow rate or a reducing target–substrate distance. For a constant argon flow rate, a critical value of the deposition time exists at which both the resistivity and the effect of the target–substrate distance are minimized. Finally, it is concluded that the film resistivity has low sensitivity to the target–substrate distance if the best deposition conditions which mostly attain the lowest resistivity are matched.
Keywords: Indium tin oxide (ITO); Polyethylene terephthalate (PET); Spectroscopic ellipsometry; Magnetron sputtering;

Ni–Mo–Co ternary alloy as a replacement for hard chrome by Meenu Srivastava; C. Anandan; V.K. William Grips (167-174).
Hard chrome is the most extensively used electroplated coating in the aerospace and automotive industries due to its attractive properties such as high hardness and excellent wear resistance. However, due to the health risks associated with the use of hexavalent chromium baths during electroplating, there is a need to identify an alternative to this coating. In this study a nickel–molybdenum alloy with cobalt as the alloying element has been developed. The coating was characterized for its micro hardness, wear resistance, coefficient of friction and corrosion resistance. The coating was also subjected to heat treatment at temperatures in the range of 200°–600 °C. It was observed that the micro hardness of Ni–Mo–Co (730 KHN) alloy coating under optimized conditions is apparently quiet similar to that of the most probable substitute Co–P (745 VHN) and hard chrome (800 VHN) coatings. The tribological properties like the wear rate and coefficient of friction of the 400 °C heat treated Ni–Mo–Co coating were noticed to be better compared to hard chrome coating. The electrochemical impedance and polarization studies showed that the corrosion resistance of heat treated Ni–Mo–Co alloy was better than as-deposited Ni–Mo–Co and Ni–Mo coating.
Keywords: Ni–Mo–Co; Ni–Mo; Microstructure; Electrochemical impedance spectroscopy; Photoelectron spectroscopy;

Annealing temperature effect on structure and electrical properties of films formed of Ge nanoparticles in SiO2 by Ionel Stavarache; Ana-Maria Lepadatu; Toma Stoica; Magdalena Lidia Ciurea (175-179).
Ge–SiO2 films with high Ge/Si atomic ratio of about 1.86 were obtained by co-sputtering of Ge and SiO2 targets and subsequently annealed at different temperatures between 600 and 1000 °C in a conventional furnace in order to show how the annealing process influences the film morphology concerning the Ge nanocrystal and/or amorphous nanoparticle formation and to study their electrical behaviour. Atomic force microscopy (AFM) imaging, Raman spectroscopy and electrical conductance measurements were performed in order to find out the annealing effect on the film surface morphology, as well as the Ge nanoparticle formation in correlation with the hopping conductivity of the films. AFM images show that the films annealed at 600 and 700 °C present a granular surface with particle height of about 15 nm, while those annealed at higher temperatures have smoother surface. The Raman investigations evidence Ge nanocrystals (including small ones) coexisting with amorphous Ge in the films annealed at 600 °C and show that almost all Ge is crystallized in the films annealed at 700 °C. The annealing at 800 °C disadvantages the Ge nanocrystal formation due to the strong Ge diffusion. This transition in Ge nanocrystals formation process by annealing temperature increase from 700 to 800 °C revealed by AFM and Raman spectroscopy measurements corresponds to a change in the electrical transport mechanism. Thus, in the 700 °C annealed films, the current depends on temperature according to a T −1/2 law which is typical for a tunnelling mechanism between neighbour Ge nanocrystals. In the 800 °C annealed films, the current–temperature characteristic has a T −1/4 dependence showing a hopping mechanism within an electronic band of localized states related to diffused Ge in SiO2.
Keywords: Ge–SiO2 films; Ge nanocrystals; Raman spectroscopy; Electrical behaviour; AFM;

Electrolytic deposition of Sn-coated mesocarbon microbeads as anode material for lithium ion battery by Min-Jen Deng; Du-Cheng Tsai; Wen-Hsien Ho; Ching-Fei Li; Fuh-Sheng Shieu (180-184).
Deposited of crystalline tin (Sn) coatings on mesocarbon microbead (MCMB) powder as anodes of lithium ion (Li-ion) battery was conducted in the SnSO4 solution by a cathodic electrochemical synthesis. The Sn-coated MCMB specimens were characterized by X-ray diffraction, scanning electron microscopy, and charge/discharge tests. The synthesis condition of Sn-coated MCMB was optimized by considering the agglomeration, size, and adhesion of the samples to the current collectors in the battery. The Sn-coated MCMB electrodes exhibit increased reversible capacity without sacrificing its cycling behavior, compared with bare MCMB electrodes. It is concluded that electrolysis-deposited Sn-coated MCMB electrodes may emerge as a practical and promising anode material for secondary Li-ion batteries.
Keywords: Lithium ion battery; Electrolytic deposition; Sn-coated Mesocarbon microbead (MCMB);

Formation of three-dimensional nano-porous silver films and application toward electrochemical detection of hydrogen peroxide by Junpeng Fan; Xiufang Bian; Yuchao Niu; Yanwen Bai; Xinxin Xiao; Chuncheng Yang; Jianfei Yang; Jinyue Yang (185-189).
By using the chemically dealloying method, three-dimensional nano-porous silver films (3-D NPSFs) are fabricated into a novel sensor for detecting hydrogen peroxide. The precursor films are prepared by high vacuum magnetron co-sputtering. High-resolution transmission electron microscope (HRTEM) and scanning electron microscope (SEM) are taken to investigate the structure and the micro morphology of the precursor films and nano-porous films. We find that the precursor films are composed of glassy matrix and nanocrystallines. After dealloying, the films exhibit a combination of homogenously distributed pores and silver filaments, and exhibit an open, three dimensional bicontinuous interpenetrating ligament–channel structure. Thickness and morphology of the films can be easily controlled by the sputtering time and alloy composition of the precursor films, respectively. In addition, NPSFs show a good linear responding for the concentration of hydrogen peroxide in phosphate buffered solutions, which indicates NPSFs could be a promising electrochemical material for hydrogen peroxide detection.
Keywords: Nano-porous films; Magnetron co-sputtering; Microstructure; Hydrogen peroxide detection;

Adsorption of CH4 on nitrogen- and boron-containing carbon models of coal predicted by density-functional theory by Xiao-Qiang Liu; Ying Xue; Zhi-Yue Tian; Jing-Jing Mo; Nian-Xiang Qiu; Wei Chu; He-Ping Xie (190-197).
Three adsorption sites were taken into account for 5 × 5 × 1 graphenes, namely, Top, Bond and Center. The dotted line circle indicates the carbon atoms of graphene doped by nitrogen and/or boron. Three adsorption orientations of methane, including Down, Up and Parallel configurations.Graphene doped by nitrogen (N) and/or boron (B) is used to represent the surface models of coal with the structural heterogeneity. Through the density functional theory (DFT) calculations, the interactions between coalbed methane (CBM) and coal surfaces have been investigated. Several adsorption sites and orientations of methane (CH4) on graphenes were systematically considered. Our calculations predicted adsorption energies of CH4 on graphenes of up to −0.179 eV, with the strongest binding mode in which three hydrogen atoms of CH4 direct to graphene surface, observed for N-doped graphene, compared to the perfect (−0.154 eV), B-doped (−0.150 eV), and NB-doped graphenes (−0.170 eV). Doping N in graphene increases the adsorption energies of CH4, but slightly reduced binding is found when graphene is doped by B. Our results indicate that all of graphenes act as the role of a weak electron acceptor with respect to CH4. The interactions between CH4 and graphenes are the physical adsorption and slightly depend upon the adsorption sites on graphenes and the orientations of methane as well as the electronegativity of dopant atoms in graphene.
Keywords: Nitrogen-/Boron-containing graphenes; Coal models; CH4; Adsorption; DFT;

Absorption of Pb on a zigzag (10,  0) carbon nanotube (CNT) surface, pure and functionalized with carboxyl (―COOH) and hydroxyl (―OH) groups was investigated using the density functional theory. Binding energy calculations were performed and indicated that adsorption of the Pb metal on the surface of the three nanotubes were stable, through a chemisorption. Therefore, CNTs are a feasible active material for filters that retain such metal. After Pb adsorption, the CNT and COOH-CNT conductivity changed, from semiconductor to half-metallic for CNT and from semiconductor to metallic for COOH-CNT, which can serve as a signal for Pb sensor. In all three cases adsorption produced a change in nanotube magnetism, which can also serve as a sensitive signal for chemical sensors. After adsorption of Pb, the changes in binding energy, charge transfer, conductance and magnetism may lead to the different response in the CNTs-based sensors. Thus, it is expected that these results could provide helpful information for the design and fabrication of the Pb sensing devices.
Keywords: Nanostructures; Ab initio calculations; Electronic structure; Band-structure;

A novel fabrication of a superhydrophobic surface with highly similar hierarchical structure of the lotus leaf on a copper sheet by Zhiqing Yuan; Xian Wang; Jiping Bin; Chaoyi Peng; Suli Xing; Menglei Wang; Jiayu Xiao; Jingcheng Zeng; Yong Xie; Ximei Xiao; Xin Fu; Huifang Gong; Dejian Zhao (205-210).
A novel and facile avenue was developed to successfully fabricate a regular hierarchical surface structure on a copper sheet via the combination of polydimethylsiloxane (PDMS) template and chemical etching method in this paper. The as-prepared hierarchical surface structure was comprised of uniform-sized microprotrusions and nanostructures which was similar to the natural lotus leaf. After modified by stearic acid, the surface was covered with a layer of hydrophobic chemical groups and became superhydrophobic. The values of its water contact angle and sliding angle were about 153° and 7°, respectively. Its wettability kept rather stable when it was exposed to humid conditions for 3 months. This study provides a new way to fabricate uniform surface microstructures that are highly similar to natural biological surfaces on metal materials.
Keywords: Copper; Superhydrophobic; Hierarchical surface structure; Contact angle; Sliding angle;

Evolution of step-terrace (vicinal or stepped) structure of cleaned c-plane sapphire substrates irradiated with low-pressure air plasma (18 W/12 MHz) was studied with atomic force microscopy (AFM). Depending on plasma irradiation time and post-annealing treatment, original structure with uniform terrace width and sharp steps undergoes distinct morphology changes. With longer plasma irradiation up to 30 min, we observed pairing of neighboring terraces into alternating wider and narrower terraces, steps roughening and terrace etching, and “step-terrace free” morphology with etched pits which are stable against annealing. These phenomena are discussed in terms of surface diffusion and chamber temperature effects. The findings reported here will have important implications for plasma modification and contamination control of sapphire substrates.
Keywords: Sapphire; Step-terrace structure; Morphology evolution; Plasma treatment; Atomic force microscopy;

First principles and experimental study of NH3 adsorptions on MnO x surface by De Fang; Feng He; Da Li; Junlin Xie (215-219).
The shorter Mn―N bonds and the more negative E ads values indicated that NH3 adsorptions took place easily on Mn2O3 (2 2 2) and Mn3O4 (2 1 1) surfaces, which was in line with the NH3-TPD and NH3-SCR performances.The oxidative abstraction of hydrogen from adsorbed ammonia is the first step in selective catalytic reduction (SCR) and NH3 adsorptions on the MnO x surfaces played a significant role in the mechanism of SCR with NH3. NH3 adsorptions on the Mn2O3 (2 2 2), Mn3O4 (2 1 1) and MnO2 (1 1 0) surfaces were investigated by the density functional theory (DFT) method. With more negative adsorption energy values, the Mn2O3 (2 2 2) and Mn3O4 (2 1 1) surfaces tended to be the favorable adsorption sites for NH3 molecule. In addition, the shorter Mn―N bonds indicated that NH3 adsorptions took place easily on Mn2O3 (2 2 2) and Mn3O4 (2 1 1) surfaces. According to the ammonia temperature programmed desorption (NH3-TPD) performance, Mn2O3 and Mn3O4 showed significantly higher amount of desorbed NH3, which was in good agreement with the DFT study. Meanwhile, the NH3-SCR performances of Mn2O3 and Mn3O4 for NO conversion below 433 K show higher performance than that of MnO2.
Keywords: Density functional theory; NH3 adsorptions; MnO x surface; SCR reaction;

Novel titania and hafnia structures on top of silica wafer were produced using atomic layer deposition through the accessible pores created by a patterned polydimethylsiloxane (PDMS) stamp in conformal contact. Typically, the processing temperature was in the range of 125 °C in order to avoid damaging the stamp and also to create an amorphous metal oxide deposit. Interestingly, the deposit formation tended to be dominated by condensation of the metal oxide precursor and water in the vicinity of the contact edges of the stamp and substrate. Upon removal of the stamp, the deposit patterns thus exhibited narrow features of much finer lateral resolution than the channel width of the stamp. Furthermore, it was demonstrated that oxide patterns of complex geometries were formed through the accessible pores.
Keywords: Soft lithography; Atomic layer deposition; Mineral oxide; Condensation;

Effects of substrate microstructure on the formation of oriented oxide nanotube arrays on Ti and Ti alloys by C.P. Ferreira; M.C. Gonçalves; R. Caram; R. Bertazzoli; C.A. Rodrigues (226-234).
The formation of nanotubular oxide layers on Ti and Ti alloys has been widely investigated for the photocatalytic degradation of organic compounds due to their excellent catalytic efficiency, chemical stability, and low cost and toxicity. Aiming to improve the photocatalytic efficiency of this nanostructured oxide, this work investigated the influence of substrate grain size on the growth of nanotubular oxide layers. Ti and Ti alloys (Ti–6Al, Ti–6Al–7Nb) were produced by arc melting with non-consumable tungsten electrode and water-cooled copper hearth under argon atmosphere. Some of the ingots were heat-treated at 1000 °C for 12 and 24 h in argon atmosphere, followed by slow cooling rates to reduce crystalline defects and increase the grain size of their microstructures. Three types of samples were anodized: commercial substrate, as-prepared and heat-treated samples. The anodization was performed using fluoride solution and a cell potential of 20 V. The samples were characterized by optical microscopy, field-emission scanning electron microscopy and X-ray diffraction. The heat treatment preceding the anodization process increased the grain size of pure Ti and Ti alloys and promoted the formation of Widmanstätten structures in Ti6Al7Nb. The nanotubes layers grown on smaller grain and thermally untreated samples were more regular and homogeneous. In the case of Ti–6Al–7Nb alloy, which presents a α + β phase microstructure, the morphology of nanotubes nucleated on α matrix was more regular than those of nanotubes nucleated on β phase. After the annealing process, the Ti–6Al–7Nb alloy presented full diffusion process and the growth of equilibrium phases resulting in the appearance of regions containing higher concentrations of Nb, i.e. beta phase. In those regions the dissolution rate of Nb2O5 is lower than that of TiO2, resulting in a nanoporous layer. In general, heat treating reduces crystalline defects and promotes the increasing of the grain sizes, not favoring the process of nanotube nucleation and growth on the metallic surface.
Keywords: TiO2 nanotubes; Ti alloys; Ti alloys anodization;

Li2MnO3 stabilized LiNi1/3Co1/3Mn1/3O2 cathode materials are discussed by xLi2MnO3·(1 −  x)LiNi1/3Co1/3Mn1/3O2 (x  = 0.3 and 0.7) solid solutions. The solid solutions were synthesized by annealing the mixing LiNO3, Mn(NO3)2 and LiNi1/3Co1/3Mn1/3O2 powder at 900 °C for 12 h, and it was found that the cathode particle size increased from 200–300 to 300–500 nm. The pristine LiNi1/3Co1/3Mn1/3O2 showed the 30th discharge capacity of 174.5 mAh g−1. Our results indicated that the introduction of Li2MnO3 in the cathode could increase performance. 0.3Li2MnO3·0.7LiNi1/3Co1/3Mn1/3O2 cathode shows higher discharge of 182.0 mAh g−1 in the 30th cycle. And the discharge capacity of 214.1 mAh g−1 was obtained when the Li2MnO3 content increased to 0.7. Moreover, the cyclic performance at 55 °C was also increased by Li2MnO3. For instance, the discharge capacities were 191.2 mAh g−1 (x  = 0.3) and 229.3 mAh g−1 (x  = 0.7) and the capacity retentions are 94.9% and 91.4% after 40 cycles, respectively. The DFT calculations show that stable Li2MnO3-enriched layer is as a result of enhanced performance.
Keywords: Lithium ion battery; Cathode materials; Solid solution xLi2MnO3·(1 −  x)LiNi1/3Co1/3Mn1/3O2;

Chemical sensors based on ZnO nanorod arrays were prepared using chemical bath deposition (CBD) to investigate the sensing performance for the detection of several organic solvents with low concentrations (0.1%, 0.5%, 1%, v/v) at room temperature. High quality and high aspect-ratio (value ∼28) ZnO nanorods have a diameter of about 74 nm and average length of 2.1 μm. Nyquist plots and Bode plots of the ZnO sensors under different organic solvents were obtained by electrical impedance spectroscopy (EIS). The sensing properties such as charge-transfer resistance, double-layer capacitance and dielectric parameters were determined from the impedance spectra to explore the charge transport in low-concentration aqueous solutions. The decreasing trend of the charge-transfer resistance (R ct) as decreasing solvent concentrations is observed, and a straight line at low frequency regime indicates adsorption of water molecules on the oxide surface. The sensitivity of the ZnO sensors was calculated from the resistance variation in target solvents and in deionized water. We demonstrated the use of ZnO nanorod arrays as a chemical sensor capable of generating a different response upon exposure to methanol, ethanol, isopropyl alcohol, acetone and water, wherein the methanol sensing exhibited highest sensitivity. In addition, the ZnO sensor also demonstrates good stability and reproducibility for detection of methanol and ethanol.
Keywords: Chemical sensor; High-aspect-ratio ZnO; Ethanol; Organic solvent detection; Impedance measurement;

Application of ultrasound irradiation on sol–gel technique for corrosion protection of Al65Cu20Fe15 alloy powder by Bo Liang; Baoyan Zhang; Guodong Wang; Di Li; Xiaoming Zhang (249-257).
Al65Cu20Fe15 alloy powder was firstly encapsulated by the conventional sol–gel technique utilizing tetraethoxysilane (TEOS) as the precursor in order to improve its corrosion resistance. The optimization was based on nine well-planned orthogonal experiments (L9 (34)). Four main factors in the encapsulation process (i.e. reaction temperature, ethylenediamine concentration, TEOS concentration and feeding method) were investigated. According to the visual analyses of the result, the optimum condition was obtained. Based on the optimal condition in the conventional sol–gel technique, the encapsulation process was then conducted under ultrasonic irradiation. The effects of ultrasound amplitude and irradiation time on the encapsulation process were also studied. FTIR, XRD, SEM, DLS and EDS were also used to characterize the resulting sample. Finally, the corrosion inhibition efficiency of encapsulated powder attained 99.3% in the acidic condition of pH 1, and the average grain size (d50) of the encapsulated powder was just 4.8% larger than that of the raw powder, implying that there was a thin silica film on the surface of powder.
Keywords: Sol–gel technique; Ultrasound irradiation; Acidic inhibition; Coating;

Removal of uranium(VI) from aqueous solutions by CMK-3 and its polymer composite by Yunhai Liu; Qin Li; Xiaohong Cao; Youqun Wang; Xiaohui Jiang; Min Li; Ming Hua; Zhibin Zhang (258-266).
The ability of PANI–CMK-3 composite (PANI–CMK-3) by in site polymerizing aniline onto the surface of mesoporous carbon (CMK-3) has been explored for the removal and recovery of uranium from aqueous solutions. The results of FTIR, SEM, TG/DTA and N2 adsorption–desorption demonstrated that aniline was successfully polymerized onto the inside and outside surface of CMK-3 rather than occupying the mesopore. The U(VI) sorption on PANI–CMK-3 was well fitted to the Langmuir adsorption isothermal and pseudo-second kinetics models. The monolayer maximum capacity of PANI–CMK-3 was improved from 50.12 mg g−1 of CMK-3 to 118.30 mg g−1 at 298 K due to the imine and amine groups in PANI. The thermodynamic parameters (ΔH, ΔS and ΔG) showed the U(VI) adsorption on CMK-3–PANI and CMK-3 were all endothermic and spontaneous in nature. Selective adsorption experiments (co-existing ions, Na+, Mg2+, Zn2+, Mn2+, Ni2+ and Sr2+) show that the selectivity of CMK-3 was enhanced after aniline polymerization. Moreover, the U(VI) adsorbed on the surface of PANI–CMK-3 can be eluated by 1.0 mol L−1 HCl solution with high desorption rate of 98%.
Keywords: Composite adsorbent; Uranium; Polyaniline; Ordered mesoporous carbon (CMK-3);

The CeO2-Al2O3 supports prepared with impregnation (IM), deposition precipitation (DP), and solution combustion (SC) methods for MoO3/CeO2-Al2O3 catalyst were investigated in the sulfur-resistant methanation. The supports and catalysts were characterized by N2-physisorption, transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy (RS), and temperature-programmed reduction (TPR). The N2-physisorption results indicated that the DP method was favorable for obtaining better textural properties. The TEM and RS results suggested that there is a CeO2 layer on the surface of the support prepared with DP method. This CeO2 layer not only prevented the interaction between MoO3 and γ-Al2O3 to form Al2(MoO4)3 species, but also improved the dispersion of MoO3 in the catalyst. Accordingly, the catalysts whose supports were prepared with DP method exhibited the best catalytic activity. The catalysts whose supports were prepared with SC method had the worst catalytic activity. This was caused by the formation of Al2(MoO4)3 and crystalline MoO3. Additionally, the CeO2 layer resulted in the instability of catalysts in reaction process. The increasing of calcination temperature of supports reduced the catalytic activity of all catalysts. The decrease extent of the catalysts whose supports were prepared with DP method was the lowest as the CeO2 layer prevented the interaction between MoO3 and γ-Al2O3.
Keywords: CeO2-Al2O3 support; Preparation method; MoO3/CeO2-Al2O3; Catalytic activity; Sulfur-resistant methanation;

Study of interaction between radioactive nuclides and graphite surface by the first-principles and statistic physics by Xiaofeng Luo; Chao Fang; Xin Li; Wensheng Lai; Lifeng Sun; Tongxiang Liang (278-286).
The adsorption and desorption of four kinds of main radioactive productions (cesium, iodine, strontium and silver) on graphite surface in high temperature gas cooled reactors (HTGRs) have been studied. Using the first-principles density-functional theory, adsorptive geometry, energy and electron structure on the perfect and defective graphite surfaces have been calculated. It turns out that the adsorption of Cs, I and Sr atoms belongs to chemisorption while the adsorption of Ag is a pure physisorption. When introducing a vacancy in graphite surface, nuclide adatoms will be trapped by the vacancy and form chemical bonds with three nearest neighbor carbon atoms, leading to significant increase of the adsorption energy. In addition, a model of grand canonical ensemble is employed to deduce the adsorption rate as a function of temperature and partial pressure of nuclides produced. The transition temperate from adsorption to desorption of nuclides on graphite surface is defined as the inflexion point of the adsorption rate and its variation with nuclide density is obtained.
Keywords: Adsorption; Graphite surface; The first principle; HTGRs;

TiAlN/Al2O3 multilayers which have constant TiAlN layer thickness (10 nm) and various Al2O3 layer thicknesses ranging from 0.5 nm to 4.5 nm were synthesized on alumina substrate by magnetron sputtering. The effects of annealing on the mechanical and structural properties of the multilayers were investigated using X-ray diffractometry (XRD), X-ray reflection (XRR), X-ray photoelectron spectroscopy (XPS), and Nanoindenter. It was found that the hardness for the multilayers with Al2O3 layer thickness from 0.5 nm to 4.5 nm was much higher than TiAlN or Al2O3 monolayer and their hardness values were over 36 GPa. The annealed multilayers displayed high-temperature stable hardness and elastic modulus. The hardness increases from 36 GPa of as-deposited to 39 GPa of annealed multilayer at 700 °C in the case of l Al 2 O 3 = 1.2 nm . It also indicates the highest elastic modulus of 560 GPa after 700 °C annealing. The multilayers had polycrystallines of TiAlN(1 1 1) and TiAlN(2 2 2) textures. Compared with as-deposited multilayers, the annealed multilayers exhibited unchanged textures. The interface and layered structure also showed good high-temperature stability.
Keywords: TiAlN/Al2O3 multilayers; Thermal stability; Hardness; Magnetron sputtering; Layer thickness;

Room temperature deposition of single and multiple layers of silicon and molybdenum has been explored in vacuo by scanning tunneling microscopy at growth conditions used for typical Mo/Si multilayer optics, enabling the study of the topography down to the nanometer scale. Periodic Mo/Si multilayer films with a molybdenum layer thickness of 2.5 nm and a silicon layer thickness of 5 nm show an evolution of the surface roughness that is similar to polycrystalline self-affine film growth. By applying an ion beam treatment of the silicon layers this increase of the roughness with layer thickness is completely mitigated, yielding a final roughness of the entire stack similar to that of the first ion treated silicon layer. The ion treatment step used here is most efficient at spatial frequencies around 1/10 nm−1. Polycrystalline growth of molybdenum on this ion treated silicon layer is observed only when the layer exceeds 3 nm thickness, while smaller amounts of molybdenum do not significantly increase the surface roughness. The almost identical values for the roughness of ion treated silicon and the 2.5 nm molybdenum grown on top of ion treated silicon show that the roughness of Si-on-Mo and Mo-on-Si interfaces have a similar contribution to the optical performance of Mo/Si multilayer films. The contributions originate mainly from spatial frequencies above 1/4 nm−1.
Keywords: Thin film growth; Scanning tunneling microscopy; Ion beam sputtering; Silicon; Interfaces, structure and roughness;

Nanosecond and sub-nanosecond pulsed laser ablation of thin single and multi-layer packaging films by Adrian H.A. Lutey; Michele Sozzi; Simone Carmignato; Stefano Selleri; Annamaria Cucinotta; Pier Gabriele Molari (300-308).
Translating single and multi-layer packaging films are exposed to 0.5–0.8 ns laser pulses of wavelength 1064 nm and 10–12.5 ns laser pulses of wavelength 515 nm. Ablation depths and threshold fluences are reported for single-layer polyethylene (PE), polypropylene (PP) and aluminium of thickness 20–50 μm. Interaction and cut widths are reported for the same single-layer films and for four multi-layer films comprising aluminium-polypropylene and aluminium-paper. Ablation of the PE and PP films is only possible in the tested parameter range with 0.5 ns, 1064 nm pulses. Though a one order of magnitude reduction in the ablation threshold of aluminium is observed with 0.5–0.8 ns, 1064 nm pulses, the efficiency of material removal for fluences >8 J cm−2 is superior with 10–12.5 ns, 515 nm pulses. Multi-layer film response is found to be heavily dictated by the thickness of metallic layers. For multi-layer films with aluminium layers of thickness 7–9 μm, adjacent layers are removed by inter-layer heat conduction from the aluminium layer, in some cases leading to very large cut widths. For multi-layer films with aluminium layers of thickness <0.1 μm, direct ablation of all layers must take place for complete film penetration. The study provides quantitative results regarding process efficiency and quality for application of pulsed laser sources within the packaging industry.
Keywords: Laser ablation; Aluminium; Polypropylene; Polyethylene; Paper; Multi-layer films;

In an attempt to increase the stability, bioactivity and corrosion resistance of Ti–6Al–4V alloy, chitosan (CS) biocomposite coatings reinforced with multiwalled-carbon nanotubes (MWCNTs), and calcium carbonate (CaCO3) for surface modification were utilized by electroless deposition. Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) reveals the formation of a compact and highly crosslinked coatings. Electrochemical techniques were used to investigate the coats stability and resistivity for orthopedic implants in simulated body fluid (SBF). The results show that E st value is more positive in the following order: CaCO3/MWCNTs/CS > CS/MWCNTs > CS > MWCNTs. The calculated i corr was 0.02 nA cm−2 for CaCO3/MWCNTs/CS which suggested a high corrosion resistance.
Keywords: Carbon nanotube; Chitosan; Calcium carbonate; Electrochemical impedance;

Stability and prospect of UV/H2O2 activated titania films for biomedical use by Erik Unosson; Ken Welch; Cecilia Persson; Håkan Engqvist (317-323).
Biomedical implants and devices that penetrate soft tissue are highly susceptible to infection, but also accessible for UV induced decontamination through photocatalysis if coated with suitable surfaces. As an on-demand antibacterial strategy, photocatalytic surfaces should be able to maintain their antibacterial properties over repeated activation. This study evaluates the surface properties and photocatalytic performance of titania films obtained by H2O2-oxidation and heat treatment of Ti and Ti-6Al-4V substrates, as well as the prospect of assisting photocatalytic reactions with H2O2 for improved efficiency. H2O2-oxidation generated a nanoporous coating, and subsequent heat treatment above 500 °C resulted in anatase formation. Tests using photo-assisted degradation of rhodamine B showed that prior to heat treatment, an initially high photocatalytic activity (PCA) of H2O2-oxidized substrates decayed significantly with repeated testing. Heat treating the samples at 600 °C resulted in stable yet lower PCA. Addition of 3% H2O2 during the photo-assisted reaction led to a substantial increase in PCA due to synergetic effects at the surface and H2O2 photolysis, the effect being most notable for non-heat treated samples. Both heat treated and non-heat treated samples showed stable PCA through repeated tests with H2O2-assisted photocatalysis, indicating that the combination of H2O2-oxidized titania films, UV light and added H2O2 can improve efficiency of these photocatalytic surfaces.
Keywords: TiO2; Heat treatment; Photocatalysis; Hydrogen peroxide photolysis; Synergy;

Thermal stability of pulsed laser deposited iridium oxide thin films at low oxygen atmosphere by Yansheng Gong; Chuanbin Wang; Qiang Shen; Lianmeng Zhang (324-330).
Iridium oxide (IrO2) thin films have been regarded as a leading candidate for bottom electrode and diffusion barrier of ferroelectric capacitors, some process related issues need to be considered before integrating ferroelectric capacitors into memory cells. This paper presents the thermal stability of pulsed laser deposited IrO2 thin films at low oxygen atmosphere. Emphasis was given on the effect of post-deposition annealing temperature at different oxygen pressure (P O2) on the crystal structure, surface morphology, electrical resistivity, carrier concentration and mobility of IrO2 thin films. The results showed that the thermal stability of IrO2 thin films was strongly dependent on the oxygen pressure and annealing temperature. IrO2 thin films can stably exist below 923 K at P O2  = 1 Pa, which had a higher stability than the previous reported results. The surface morphology of IrO2 thin films depended on P O2 and annealing temperature, showing a flat and uniform surface for the annealed films. Electrical properties were found to be sensitive to both the annealing temperature and oxygen pressure. The room-temperature resistivity of IrO2 thin films with a value of 49–58 μΩ cm increased with annealing temperature at P O2  = 1 Pa. The thermal stability of IrO2 thin films as a function of oxygen pressure and annealing temperature was almost consistent with thermodynamic calculation.
Keywords: IrO2 thin films; Thermal stability; Low oxygen pressure; Pulsed laser deposition;

Ag- and Cu-doped multifunctional bioactive nanostructured TiCaPCON films by D.V. Shtansky; I.V. Batenina; Ph.V. Kiryukhantsev-Korneev; A.N. Sheveyko; K.A. Kuptsov; I.Y. Zhitnyak; N.Yu. Anisimova; N.A. Gloushankova (331-343).
A key property of multicomponent bioactive nanostructured Ti(C,N)-based films doped with Ca, P, and O (TiCaPCON) that can be improved further is their antibacterial effect that should be achieved without compromising the implant bioactivity and biocompatibility. The present work is focused on the study of structure, chemical, mechanical, tribological, and biological properties of Ag- and Cu-doped TiCaPCON films. The films with Ag (0.4–4 at.%) and Cu (13 at.%) contents were obtained by simultaneous sputtering of a TiC0.5–Ca3(PO4)2 target and either an Ag or a Cu target. The film structure was studied using X-ray diffraction, transmission and scanning electron microscopy, energy dispersive X-ray spectroscopy, glow discharge optical emission spectroscopy, and Raman-shift and IR spectroscopy. The films were characterized in terms of their hardness, elastic modulus, dynamic impact resistance, friction coefficient and wear rate (both in air and normal saline), surface wettability, electrochemical behavior and Ag or Cu ion release in normal saline. Particular attention was paid to the influence of inorganic bactericides (Ag and Cu ions) on the bactericidal activity against unicellular yeast fungus Saccharomyces cerevisiae and gram-positive bacteria Lactobacillus acidophilus, as well as on the attachment, spreading, actin cytoskeleton organization, focal adhesions, and early stages of osteoblastic cell differentiation. The obtained results show that the Ag-doped films are more suitable for the protection of metallic surfaces against bacterial infection compared with their Cu-doped counterpart. In particular, an excellent combination of mechanical, tribological, and biological properties makes Ag-doped TiCaPCON film with 1.2 at.% of Ag very attractive material for bioengineering and modification of load-bearing metal implant surfaces.
Keywords: Bioactive nanostructured films; Sputtering; Antimicrobial activity; Alkaline phosphatase activity;

Micro/nano-porous ZnO films were synthesized through a simple biotemplate-directed method using mango core inner shell membranes as templates. The achieved ZnO films with wrinkles on the surface are combined of large holes and small pores in the bulk. High specific surface area, numerous microspaces, and small channels for fluid circulation provided by this unique structure along with the good biocompatibility and electron communication features of ZnO material make the product an ideal platform for the immobilization of enzymes The fabricated glucose biosensor based on the porous ZnO films exhibits good selective detection ability of analyte with good stability, high sensitivity of 50.58 μA cm−2  mM−1 and a wide linear range of 0.2–5.6 mM along with a low detection limit of 10 μM.
Keywords: ZnO; Biotemplate; Porous film; Glucose; Enzyme; Bisosensor;

Can CO2 molecule adsorb effectively on Al-doped boron nitride single walled nanotube? by Peng Shao; Xiao-Yu Kuang; Li-Ping Ding; Jing Yang; Ming-Min Zhong (350-356).
Contour plot of electron density for both (6, 0) Al-doped BNNTs at GGA level.The adsorption of carbon dioxides (CO2) is very important in environmental and industrial applications. The boron nitride nanotube (BNNT) with large surface and polarity may be a good candidate as CO2 capture. Unfortunately, the pristine BNNT is almost inert to the highly stable CO2. To renew technical applications of BNNT for CO2 adsorption, we explore the possibility of CO2 adsorption on various (n, 0) (n  = 6, 8, 10, 12 and 14) Al-doped BNNT by density functional theory (DFT) calculations. The results show that the Al-doped BNNT could be a potential CO2 adsorption material, and the CO2 adsorption energies are independent of BNNT diameters. Furthermore, the interactions between CO2 and exemplified (6, 0) Al-doped BNNT are investigated by density of states (DOS) and electron density. We found the interaction between CO2 and AlB-BNNT is stronger than that of CO2 and AlN-BNNT. The adsorption of CO2 can induce new density of state, as well as a local charge fluctuation due to more electron density redistribution on the atoms near CO2 molecule.
Keywords: Adsorption; CO2 molecule; Al-doped BNNT; Electronic properties;

Dependence of morphological evolution and variation of corresponding localized surface plasmonic properties of the ultra-thin Ag island films deposited by thermal evaporation at different substrate temperatures have been investigated. It has been observed that the particle diameter, height, aspect ratio, surface coverage, roughness and particle density of the films are strongly dependent on the substrate temperature and film thickness. Depending on the trend of the shift of localized surface plasmon dip overall thermal process is divided into two stages: in first stage apparent change in localized surface plasmon dip takes place with the shift towards the shorter wavelengths. In the second stage, it is red shifted. Both these changes can be attributed to the change of morphology of the Ag island films. Strong temperature dependence between the morphological evolution and optical properties variation has been observed. Bandwidth, position and relative intensity of localized surface plasmon resonance induced absorption dip have been correlated with various morphological characteristics. Effective medium extended Maxwell–Garnett theory is used to simulate the optical transparency of these Ag metal island thin films. With the increment of substrate temperature up to 250 °C these silver metal island thin films exhibit high optical transparency in the range 600–1100 nm.
Keywords: Localized surface plasmons; Silver nanoparticles; Optical properties; Maxwell–Garnett theory; AntiReflecting coatings;

Controlled growth and properties of p-type cuprous oxide films by plasma-enhanced atomic layer deposition at low temperature by Jung-Dae Kwon; Se-Hun Kwon; Tae-Hoon Jung; Kee-Seok Nam; Kwun-Bum Chung; Dong-Ho Kim; Jin-Seong Park (373-379).
Various copper oxide films were successfully grown by plasma-enhanced atomic layer deposition (PEALD) at a low temperature of 100 °C. X-ray diffraction analysis of the films indicated that phase-controlled deposition of CuO x phases (0 ≤  x  < 1) was possible by controlling the number of Cu deposition steps during one PEALD cycle with a fixed oxidation step. When Cu deposition was executed in one step, an amorphous CuO x (x  = 0.9) film with a smooth surface (RMS roughness of 0.97 nm) was obtained. On the other hand, when the number of Cu deposition steps was increased to three, a CuO x (x  = 0.6) thin film with a polycrystalline phase (grain size: 25 nm) was obtained. The as-deposited CuO0.6 film showed p-type conductivity (Hall mobility ∼37 cm2/V·s and hole concentration ∼5.4 × 1014  cm−3). Moreover, p-type CuO0.6/n-type ZnO heterojunction diodes fabricated on a flexible polyethylene terephthalate substrate exhibited electrical rectification with a threshold voltage of 1.2 V.
Keywords: Cuprous oxide; PEALD; p-type; Semiconductor; XPS; XRD; Heterojunction;

Electrochemical and morphological characterisation of polyphenazine films on copper by Carla Gouveia-Caridade; Andreia Romeiro; Christopher M.A. Brett (380-388).
The morphology of films of the phenazine polymers poly(neutral red) (PNR), poly(brilliant cresyl blue) (PBCB), poly(Nile blue A) (PNB) and poly(safranine T) (PST), formed by potential cycling electropolymerisation on copper electrodes, in order to reduce the corrosion rate of copper, has been examined by scanning electron microscopy (SEM). The copper surface was initially partially passivated in sodium oxalate, hydrogen carbonate or salicylate solution, in order to inhibit copper dissolution at potentials where phenazine monomer oxidation occurs, and to induce better polymer film adhesion. SEM images were also taken of partially passivated copper in order to throw light on the different morphology and anti-corrosive behaviour of the polyphenazine films. Analysis of the morphology of the polymer-coated copper with best anti-corrosive behaviour after 72 h immersion in 0.1 M KCl, Cu/hydrogen carbonate/PNB, showed that the surface is completely covered by closely packed crystals. By contrast, images of PST films on copper partially passivated in oxalate solution, that had the least protective behaviour, showed large amounts of insoluble corrosion products after only 4 h immersion in 0.1 M KCl.
Keywords: Polyphenazine films; Morphology; Partially passivated copper; Corrosion inhibition;

Comparative studies on damages to organic layer during the deposition of ITO films by various sputtering methods by Hao Lei; Meihan Wang; Yoichi Hoshi; Takayuki Uchida; Shinichi Kobayashi; Yutaka Sawada (389-394).
Aluminum (III) bis(2-methyl-8-quninolinato)-4-phenylphenolate (BAlq) was respectively bombarded and irradiated by Ar ions, oxygen ions, electron beam and ultraviolet light to confirm damages during the sputter-deposition of transparent conductive oxide (TCO) on organic layer. The degree of damage was evaluated by the photoluminescence (PL) spectra of BAlq. The results confirmed the oxygen ions led to a larger damage and were thought to play the double roles of bombardment to organic layer and reaction with organic layer as well. The comparative studies on PL spectra of BAlq after the deposition of TCO films by various sputtering systems, such as conventional magnetron sputtering (MS), low voltage sputtering (LVS) and kinetic-energy-control-deposition (KECD) system, facing target sputtering (FTS) were performed. Relative to MS, LVS and KECD system, FTS can completely suppress the bombardment of the secondary electrons and oxygen negative ions, and keep a higher deposition rate simultaneously, thus it is a good solution to attain a low-damage sputter-deposition.
Keywords: Damage to organic layer; Magnetron sputtering (MS); Low voltage sputtering (LVS); Kinetic-energy-control-deposition (KECD); Facing target sputtering (FTS); PL spectra;

A surface rejuvenation process was developed for generation variable thickness of metal deposits on polymer microspheres via electroless plating. Thus, Ni(II), Cu(II) and Ag(I) complexes formed on triethylenetetramine (TETA) functional crosslinked poly(glycidyl methacrylate) (PGMA) microspheres were reduced to zero-valent metals. The resulting metals (1.1–1.5 mmol g−1) were employed as seed points for electroless metal plating (self-seeding) without using Pd or tin pre-activating species. Treatment of the metalized surfaces with hydrazine or hydrazinium formate was demonstrated to reactivate (rejuvenate) the surface and allows further metal deposition from electroless plating solutions. Followed repeating of the surface rejuvenation-metalization steps resulted in step wise increasing of the metal deposits (90–290 mg per g in each cycle), as inferred from metal analyses, ESEM and XPS analysis. Experiments showed that, after 6 times of cycling the metal deposits exceed 1 g per g of the microspheres on average. The process seemed to be promising for tuning up of the metal thickness by stepwise electroless plating.
Keywords: Electroless metal plating; Surface modification; Polymer microspheres; Chelating polymer; Metal coated surface;

Effect of temperature on the adsorption of sulfanilamide onto aluminum oxide and its molecular dynamics simulations by Ying-xue Ji; Feng-he Wang; Lun-chao Duan; Fan Zhang; Xue-dong Gong (403-408).
The effect of temperature on the adsorption of sulfanilamide (SA) onto aluminum oxide was researched through batch adsorption experiments, and was then simulated using the molecular dynamics (MD) method. The results show that SA can be adsorbed effectively by the adsorbent of aluminum oxide due to their interactions between SA molecule and the surface of aluminum oxide crystal, and temperature is a key factor which influences the adsorption efficiency obviously. The removal ratio of SA at 298 K is the highest among the selected temperatures (293 K, 298 K, 303 K). MD simulations revealed the interactions between SA molecules and (0 1 2) surface of aluminum oxide crystal at molecular level. The SA molecule has clung to the (0 1 2) face of aluminum oxide crystal, and its structure is deformed during its combining process with the surface. Both binding energies (E b ) and deformation energies (ΔE deform) in the SA-aluminum oxide system follow the same order as: SA-Al2O3 (298 K) > SA-Al2O3 (293 K) > SA-Al2O3 (303 K). Their deformation energies are far less than their non-bonding energies. Analysis of radial distribution functions (RDFs) indicates that SA can be adsorbed effectively by aluminum oxide crystal mainly through non-bond interactions. The simulation results agree well with the experimental results, which verify the rationality and reliability of the MD simulation. The further MD simulations provide theoretically optimal temperature (301 K) for the adsorption of SA onto aluminum oxide. The molecular dynamics simulation will be useful for better understanding the adsorption mechanism of antibiotics onto metal oxides, which will also be helpful for optimizing experimental conditions to improve the adsorptive removal efficiency of antibiotics.
Keywords: Sulfanilamide (SA); Aluminum oxide; Adsorption; Temperature; Molecular dynamics simulation;

Erbium doped CeO2 thin films were deposited on both Corning glass substrates and indium doped tin oxide (ITO) coated glass substrates by pulsed e-beam deposition (PED) method at room temperature. Structural features of Er doped CeO2 thin films were studied with X-ray diffraction (XRD) and micro-Raman spectra. The XRD patterns of all films showed polycrystalline nature and cubic crystalline structure. Raman active peaks for both undoped CeO2 and Er doped CeO2 films were determined at ∼465 cm−1. The Raman shift observed in this study can also be assigned to Raman active modes of CeO2 that are shifted from the original position due to different doping concentration. The optical properties of CeO2 films and Er doped CeO2 films, which were determined from transmittance and reflectance measurements at room temperature, were very similar in character. The refractive indices and extinction coefficients, which were calculated from 3.5 to 1.25 eV (300–1000 nm), were between 1.5–3 and 0.05–0.2, respectively. The optical band gaps were deduced from the absorption coefficient according to solid band theory. The electrochromic measurements revealed that 2% Er doped CeO2 films grown on ITO + WO3 substrates had highest charge density compared to the other samples. Long-time cyclic voltammetry (CV) and chronoamperometry (CA) measurements were carried out to investigate the stability of this film.
Keywords: Electrochromic materials; CeO2 crystal structure; Er doping; Optical properties; Electrochemical properties;

Structure, morphology and electrical properties of Mg2Si layers deposited by pack cementation by D. Stathokostopoulos; D. Chaliampalias; E.C. Stefanaki; G. Polymeris; E. Pavlidou; K. Chrissafis; E. Hatzikraniotis; K.M. Paraskevopoulos; G. Vourlias (417-424).
Magnesium silicide (Mg2Si) is a promising narrow gap semiconductor which can be used as a thermoelectric material. Chemical vapor deposition by pack cementation, which is a simple and low cost technique, was used for the first time in this work for the formation of Mg2Si compound. A series of experiments were carried out at temperatures 500–650 °C with different deposition times ranging between 15 and 180 min. As a result single phase thick layers have been prepared, depending on growth temperature and deposition time. Mg2Si was formed as a result of the Mg diffusion into the Si matrix while the film thickness increased with the deposition time, and temperature. Electrical and optical properties of the grown layers have been investigated. The examination of the as formed material was completed by performing thermal stability tests, for the determination of the safe service temperature range of the coupons. From all the experimental outcomes, it is concluded the optimum conditions for the formation of Mg2Si films is at 650 °C for a 180 min deposition period.
Keywords: Thermoelectric materials; Chemical vapor deposition; XRD; SEM; FTIR; Thermal stability;

Controlled growth of hierarchical nanostructured MnO2/carbon hybrids by Ying Chen; Bingqiao Xie; Shiyu Luo; Yong Zhang (425-430).
An exceptional hierarchical nanostructured MnO2/carbon hybrid was in situ generated by a mild wet chemical pre-treatment and then hydrothermal method. The thickness of the representative petal-like nanosheet was measured below 5 nm. Growth mechanism of the achieved hierarchical hybrid is associated with simultaneously occurred redox and oxidation-intercalation reactions. The surface layers of carbon black (XC-72) were partly exfoliated, and redox reaction between KMnO4 and hydroxyl group occurred on the both side of these layers, resulting in the hierarchical hybrid of MnO2/carbon.
Keywords: MnO2; Carbon black; Petal-like nanosheets; Hybrid; Hydrothermal method;

Chemical and structural properties of polymorphous silicon thin films grown from dichlorosilane by C. Álvarez-Macías; B.M. Monroy; L. Huerta; M.A. Canseco-Martínez; M. Picquart; J. Santoyo-Salazar; M.F. García Sánchez; G. Santana (431-439).
We have examined the effects of hydrogen dilution (R H) and deposition pressure on the morphological, structural and chemical properties of polymorphous silicon thin films (pm-Si:H), using dichlorosilane as silicon precursor in the plasma enhanced chemical vapor deposition (PECVD) process. The use of silicon chlorinated precursors enhances the crystallization process in as grown pm-Si:H samples, obtaining crystalline fractions from Raman spectra in the range of 65–95%. Atomic Force Microscopy results show the morphological differences obtained when the chlorine chemistry dominates the growth process and when the plasma–surface interactions become more prominent. Augmenting R H causes a considerable reduction in both roughness and topography, demonstrating an enhancement of ion bombardment and attack of the growing surface. X-ray Photoelectron Spectroscopy results show that, after ambient exposure, there is low concentration of oxygen inside the films grown at low R H, present in the form of Si―O, which can be considered as structural defects. Instead, oxidation increases with deposition pressure and dilution, along with film porosity, generating a secondary SiO x phase. For higher pressure and dilution, the amount of chlorine incorporated to the film decreases congruently with HCl chlorine extraction processes involving atomic hydrogen interactions with the surface. In all cases, weak silicon hydride (Si―H) bonds were not detected by infrared spectroscopy, while bonding configurations associated to the silicon nanocrystal surface were clearly observed. Since these films are generally used in photovoltaic devices, analyzing their chemical and structural properties such as oxygen incorporation to the films, along with chlorine and hydrogen, is fundamental in order to understand and optimize their electrical and optical properties.
Keywords: Polymorphous silicon; Dichlorosilane; PECVD; Nanocrystals; AFM; Raman; XPS; FTIR;

Characterization of silicon nitride thin films deposited by hot-wire CVD at low gas flow rates by Clive J. Oliphant; Christopher J. Arendse; Theophillus F.G. Muller; Dirk Knoesen (440-449).
We examined the chemical, structural, mechanical and optical properties of amorphous hydrogenated silicon nitride thin films deposited by hot-wire chemical vapour deposition using SiH4, NH3 and H2 gases at total flow rates below 33 sccm. Time of flight secondary ion mass spectroscopy reveal that the film surfaces consist of predominantly Si with hydrogenated Si x N y O z species. Energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy corroborate on the N/Si ratio. Electron energy loss spectroscopy discloses that the thickness of the nitrogen rich oxidized interface between the SiN x films and the c-Si substrate decrease with an enhancing NH3 flow rate. By varying the NH3 flow rate, dense SiN x films can be realized with hydrogen content between 16 and 9 at.%, a refractive index between 3.5 and 1.9 and optical band gap ranging from 2 to 4.5 eV. The SiN x film stress is compressive for N/Si < 0.4 and tensile for higher N/Si > 0.55. Mechanisms relating the HWCVD conditions and the film structure and properties are proposed.
Keywords: Surface roughness; Composition; Stress; Microstructure; Crystallinity; Band gap;

Effect of surface physics of metal oxides on the ability to form metallic nanowires by Jenn-Ming Song; Shih-Yun Chen; Yu-Lin Shen; Chi-Hang Tsai; Shih-Wei Feng; Hsien-Tse Tung; In-Gann Chen (450-457).
This study demonstrates that through the control on surface physics of oxide films, nanowires of various metals can be readily grown on the surface of oxide films. The photo-induced surface defects and surface roughness are suggested to be the key factor dominating the number of nucleation sites and thus the population of nanowires.Through the control of surface physics of oxide films, nanowires of various metals can be readily grown on the surface of oxide films without templates and surfactants. To clarify how the characteristics of oxides affect the formation of metallic nanowires, this report investigated the influence of the surface physical characteristics, including morphological, electrical, optical and hydrophilic properties of the metal oxide substrates (TiO2, CeO2, and indium tin oxide), on the yield of Ag and Pt nanowires. In addition to the surface roughness, photo-induced defects were suggested to be the key factor dominating the number of nucleation sites and thus the population of nanowires.
Keywords: Metal oxide; Metallic nanowires; Surface physics; Nucleation and growth;

This study investigated the interaction between the Al in the Zn bath and the surface oxides formed by selective oxidation on a 1.2Si–1.5Mn TRIP steel during hot-dip galvanizing. XPS and TEM were employed for characterization. The results indicated that the amorphous xMnO·SiO2 oxide could react with Al to form a Si–Mn–Al-containing oxide. The crystalline MnSiO3 and Mn2SiO4 oxides could be largely reduced by Al to form holes in the oxide film. Consequently, the steel covered by a layer of mixed xMnO·SiO2 and MnSiO3 could form a continuous Fe2Al5 inhibition layer and showed the highest galvanizability among the three samples examined.
Keywords: Steel; Zinc; TEM; XPS; Selective oxidation; Interfaces;

Effect of film compatibility on electro-optic properties of dye doped polymer DR1/SU-8 by Xiaoqiang Sun; Ying Xie; Xuliang Zhao; Dehui Li; Shimin Zhao; Yuanbin Yue; Xibin Wang; Jian Sun; Lei Liang; Changming Chen; Daming Zhang; Fei Wang; Zhiyuan Xie (469-476).
The physic-chemical compatibility of passive cladding and poled Dispersed Red 1 (DR1) doped ultraviolet (UV) curable polymer SU-8 was investigated. The multilayer films consisting of DR1/SU-8 core and Norland Optical Adhensive 73 (NOA73), SU-8, polydimethylsiloxane (PDMS), or polymethylmethacrylate (PMMA) upper-cladding were fabricated on the silicon substrate, respectively. The interface morphologies were characterized through scan electronic microscope. Parallel plate electric field poling was carried out to align the polarity of chromophores in SU-8. The core–cladding interface with no chemical erosion or delamination was obtained by adopting an excess UV exposure and higher temperature dealing when NOA73 was used as the upper-cladding. The root mean square roughness of the upper-cladding surface was measured by atomic force microscope to verify the poling process. The electro-optic (EO) signal response amplitude of these multilayer films was used to characterize the polarizability alignment of DR1 chromophores by means of Teng–Man method after poling. Resistivity of claddings was measured at the glass transition temperature of DR1/SU-8 to explain the EO response difference. The configuration of NOA73/(DR1/SU-8) exhibited the best EO performance and time relaxation in amplitude within 550 h by prolonging the cooling time in poling process. A channel waveguide was fabricated to study the poling-induced optical loss. The results show that the selection of passive cladding with favorable electrical and chemical property is essential to establish optical nonlinearity in the dye–polymer system.
Keywords: Electro-optic polymers; Compatibility; Passive cladding; Waveguide;

Effect of confining overlay in micro scale laser bulge forming by Chao Zheng; Sheng Sun; Guofang Zhang; Libin Song; Zhong Ji (477-482).
Micro scale laser bulge forming (μLBF) shows great potential in fabricating high precision and high-aspect-ratio metallic micro components. The present paper investigated the effect of the confining overlay in μLBF experimentally. The surface morphology of micro bulged parts of pure copper foils with and without confining overlay was explored through the scanning electron microscope. The surface features of quartz glasses with different thickness shocked by single and multiple laser pulses were observed using the optical microscope. The effect of thickness of the confining overlay on the maximum bulging height of micro parts was investigated. Experiments reveal that the application of the confining overlay in μLBF has significant influence on both the surface morphology and plastic deformation of micro bulged parts. The change of laser ablation mode is responsible for forming results. In addition, there is a moderate thickness of the confining overlay to induce noticeable plastic deformation without failure.
Keywords: Micro scale laser bulge forming; Laser shock waves; Plastic deformation; Confining overlay; Surface morphology;

Surface modified carbon cloth for use in electrochemical capacitor by JiaXun Du; Dillip Mishra; Jyh-Ming Ting (483-489).
The paper reports enhanced power densities for electrochemical capacitor through grafting carbon nanotubes (CNTs) onto the surface of activated carbon cloth (ACC). The surface-modified ACCs were first examined for their material properties and then evaluated for their electrode performance such as capacitance, equivalent series resistance, energy density, and power density. Improved electrochemical performance was obtained due to the surface modification by CNTs. In particular, the CNTs lower the contact resistance and therefore increase the power density of the electrochemical capacitor. Furthermore, we show that through such a surface modification, the specific capacitance can be increased from 108 to 117 F/g, i.e., an 8.3% increase, the energy density can be increased from 16.7 to 17.64 Wh/kg, i.e., a 5.4% increase, or the power density can be increased from 4.8 to 11.3 kW/kg, i.e., a 135% increase. To our best knowledge, the energy density and power density of a electrochemical capacitor having CNT-grafted ACC electrode have not been reported. Also, a 70% retention at a scan rate of 500 mV s−1 and a long cycle life of 20,000 cycles at a scan rate of 200 mV s−1 are demonstrated.
Keywords: High power supercapacitor; Carbon nanotubes; Activated carbon cloth; Electric double layer capacitor; Sputter deposition; Microwave plasma;

The Ag@AgCl layer in situ deposited on the surface of ZnO particle achieved the photosensitization of ZnO through SPR effect; it established heterojunction interface electric field between ZnO and Ag@AgCl at the same time, facilitating the photogenerated electron–hole separation and accelerating their transfer, thereby effectively increasing the photocatalytic activity of the composites.Metal-semiconductor compounds, such as Ag@AgX (X = Cl, Br, I), enable visible light absorption and separation of photogenerated electron–hole through surface plasmon resonance (SPR) effect. However, the electron–hole generated and separated by light are vulnerable in Ag@AgX phase because of the occurrence of secondary recombined. In order to more effectively utilize the SPR photocatalytic effect, a heterojunction interface electric field was implemented effectively by introducing some cost-effective semiconductor materials with wide band gap to Ag@AgX compound, thereby preventing photogenerated electrons from secondarily compounding with the holes. In this article, by mixing 500 nm diameter ZnO and Ag@AgX compounds with mole ratio 1:1, studies show that 15 min illumination under visible light can complete degradation of rhodamine B (RhB), and indicate a high stability of photocatalytic degradation. Through Mott–Schottky plots and photoinduced It curve, the results show that through the ZnO/Ag@AgCl composition, heterojunction interface electric field can be formed effectively, thus increasing the separation efficiency and transfer speed of photogenerated electrons and holes, and improving the photocatalytic performance. Meanwhile, Ag@AgCl can implement the photosensitization of ZnO with high efficiency through SPR effect, which will enlarge the response range of photocatalyst to the visible area.
Keywords: ZnO; Ag@AgCl; Surface plasmon resonance; Photocatalytic; Visible light;

Chitosan-coated MnFe2O4 nanoparticles (CCMNPs) of uniform size were synthesized by an eco-friendly method. The obtained product was characterized by XRD, TEM, FTIR and SQUID. The results show that NaOH played a key role in the formation of CCMNPs. The as-prepared CCMNPs with a saturation magnetization of 16.5 emu/g were used as magnetic nanoadsorbents to remove toxic Cu(II) and Cr(VI) ions from aqueous solution. Factors influencing the adsorption of heavy metal ions, such as pH value, agitation time and initial metal concentration were investigated. The maximum adsorption capacities of Cu(II) and Cr(VI) on CCMNPs were 22.6 and 15.4 mg/g, respectively. The competitive adsorption of Cu(II) and Cr(VI) from binary solution by CCMNPs was also studied, and the result shows that the affinity between Cu(II) and CCMNPs was much higher than that between Cr(VI) and CCMNPs.
Keywords: Composites; Magnetic materials; Nanostructures; Magnetic properties; Adsorption;

Enhanced field emission from vertically aligned carbon nanotubes on metal mesh electrode by Chi Li; Shuyi Ding; Wei Lei; Xiaobing Zhang; Baoping Wang (505-508).
A vertically aligned carbon nanotube (CNT) mesh emitter array on metal mesh electrode has been fabricated with a low temperature growth process, from which a current density of up to 5 A/cm2, and a threshold field of 0.9 V/μm for a current density 1 mA/cm2 were obtained, which show much better performance than CNT mesh on a flat electrode. This result was attributed to the enhanced edge effect of CNT mesh on metal mesh electrode. The numerical calculation results proved that the electric field on top of CNT emitter on mesh electrode was enhanced compared to that on flat electrode.
Keywords: Carbon nanotubes; Micro structure; Field emission; Metal mesh; Large current density;

BiOCl nanosheets immobilized on electrospun polyacrylonitrile nanofibers with high photocatalytic activity and reusable property by Yuechen Chou; Changlu Shao; Xinghua Li; Chunyan Su; Hongchuan Xu; Mingyi Zhang; Peng Zhang; Xin Zhang; Yichun Liu (509-516).
We fabricated one-dimensional BiOCl/PAN composite nanofibers with high photocatalytic activity and reusable property by combining electrospinning technique and solvothermal method.One-dimensional BiOCl/PAN composite nanofibers which are composed of bismuth oxychloride (BiOCl) nanosheets on electrospun polyacrylonitrile (PAN) nanofibers were fabricated by combining electrospinning technique and solvothermal method. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, UV–vis diffuse reflectance, Fourier transform infrared spectrum, X-ray photoelectron spectroscopy, thermal gravimetric and differential thermal analysis, were used to characterize the as-fabricated BiOCl/PAN composite nanofibers. The results revealed that BiOCl nanosheets were successfully immobilized on electrospun PAN nanofibers. The contents of the BiOCl nanosheets were controlled by adjusting the precursor concentrations for the fabrication of BiOCl/PAN composite nanofibers during the solvothermal synthesis processes. It was found that some interactions might exist between BiOCl and PAN molecules of BiOCl/PAN composite nanofibers. The obtained BiOCl/PAN composite nanofibers exhibited high photocatalytic activity for degradation of rhodamine B under ultraviolet light irradiation. The trapping experiments confirmed that the main active species for photocatalysis was hydroxyl radicals, which was produced by both the oxidative pathway and reductive pathway. Notably, the BiOCl/PAN composite nanofibers photocatalysts not only had good reusable property because of their one-dimensional structure and flexibility but also retained high photocatalytic stabilities after several cycles due to the interaction between BiOCl and PAN molecules.
Keywords: BiOCl nanosheets; PAN nanofibers; Electrospinning; Photocatalysis; Reuse;

Cyclodextrin directed self-assembly of TiO2 nanoparticles by Sungkwon Yoon; William T. Nichols (517-523).
In this paper we study the self-assembly of TiO2 nanoparticles with cyclodextrin molecules into a self-supporting fiber network. We observe the network's macroscopic growth and evolving microstructure as a function of time and relate these to the chemical changes of the solution and the composition of the growing network. From this data we elucidate the steps of the self-assembly process. The TiO2 nanoparticles initiate a photocatalytic reaction that results in a ring breaking and dehydration of the cyclodextrin molecules in solution. This dehydration exposes the hydrophobic regions of the cyclodextrin molecule to the water solution, supplying the force that drives self-assembly. This same hydrophobic force also leads to branch and junction formation between fibers that ultimately build up the self-supporting network structure.
Keywords: Cyclodextrin; Titania; Self-assembly; Nanofiber; Biomimetics;

RF plasma MOCVD of Y2O3 thin films: Effect of RF self-bias on the substrates during deposition by S.S. Chopade; S.A. Barve; K.H. Thulasi Raman; N. Chand; M.N. Deo; A. Biswas; Sanjay Rai; G.S. Lodha; G.M. Rao; D.S. Patil (524-531).
Yttrium oxide (Y2O3) thin films have been deposited by radio frequency plasma assisted metal organic chemical vapor deposition (MOCVD) process using (2,2,6,6-tetramethyl-3,5-heptanedionate) yttrium (commonly known as Y(thd)3) precursor in a plasma of argon and oxygen gases at a substrate temperature of 350 °C. The films have been deposited under influence of varying RF self-bias (−50 V to −175 V) on silicon, quartz, stainless steel and tantalum substrates. The deposited coatings are characterized by glancing angle X-ray diffraction (GIXRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry and scanning electron microscopy (SEM). GIXRD and FTIR results indicate deposition of Y2O3 (BCC structure) in all cases. However, XPS results indicate nonstoichiometric cubic phase deposition on the surface of deposited films. The degree of nonstoichiometry varies with bias during deposition. Ellipsometry results indicate that the refractive index for the deposited films is varying from 1.70 to 1.83 that is typical for Y2O3. All films are transparent in the investigated wavelength range 300–1200 nm. SEM results indicate that the microstructure of the films is changing with applied bias. Results indicate that it is possible to deposit single phase cubic Y2O3 thin films at low substrate temperature by RF plasma MOCVD process. RF self-bias that decides about the energy of impinging ions on the substrates plays an important role in controlling the texture of deposited Y2O3 films on the substrates. Results indicate that to control the structure of films and its texture, it is important to control the bias on the substrate during deposition. The films deposited at high bias level show degradation in the crystallinity and reduction of thickness.
Keywords: Y2O3; MOCVD; XPS; RF plasma;

Mechanical and electrical properties of GeSb2Te4 film with external voltage applied by Guang-Gui Cheng; Zhong-Qiang Zhang; Jian-Ning Ding; Zhiyong Ling; Yu-Bing Chen (532-537).
A GeSb2Te4 (GST) film was deposited by RF magnetron sputtering with microwave electron cyclotron resonance plasma chemical vapor deposition equipment. Mechanical and electrical properties together with the morphologies of the film were studied by a nanoindenter which was equipped with nano-electrical contact resistance (nano-ECR) tool and atomic force microscope (AFM). Results show that when no voltage applied between sample and indent tip during indenting, the pile-up phenomenon was observed, the hardness and elastic modulus increases with the load mainly due to the underestimate of the contact area; when external voltages of −7 V, −8 V, −9 V, −10 V were applied, the resistance of the film decreased with applied voltages in about four orders of magnitude, while the elastic modulus increased from 159 GPa to 233 GPa, this changing in mechanical and electrical properties demonstrated that phase change happen during intending, a shrinking region with radius of about 2.5 μm was observed around the indentation when −8 V applied. Furthermore, indent load can also promote the phase change at given negative voltage.
Keywords: GeSb2Te4 film; Nanoindentation; Electric caused phase change; Mechanical and electrical properties; Phase change shrinking;

Chitin butyrate coated electrospun nylon-6 fibers for biomedical applications by Hem Raj Pant; Han Joo Kim; Lok Ranjan Bhatt; Mahesh Kumar Joshi; Eun Kyo Kim; Jeong In Kim; Abdalla Abdal-hay; K.S. Hui; Cheol Sang Kim (538-544).
In this study, we describe the preparation and characterizations of chitin butyrate (CB) coated nylon-6 nanofibers using single-spinneret electrospinning of blends solution. The physicochemical properties of nylon-6 composite fibers with different proportions of CB to nylon-6 were determined using FE-SEM, TEM, FT-IR spectroscopy, and water contact angle measurement. FE-SEM and TEM images revealed that the nylon-6 and CB were immiscible in the as-spun nanofibers, and phase separated nanofiber morphology becomes more pronounced with increasing amounts of CB. The bone formation ability of composite fibers was evaluated by incubating in biomimetic simulated body fluid. In order to assay the cytocompatibility and cell behavior on the composite scaffolds, osteoblast cells were seeded on the matrix. Results suggest that the deposition of CB layer on the surface of nylon-6 could increase its cell compatibility and bone formation ability. Therefore, as-synthesized nanocomposite fibrous mat has great potentiality in hard tissue engineering.
Keywords: Nylon-6; Chitin butyrate; Nanofibers; Biomaterials; Electrospinning;

Valence band offset and Schottky barrier at amorphous boron and boron carbide interfaces with silicon and copper by Sean W. King; Marc French; Guanghai Xu; Benjamin French; Milt Jaehnig; Jeff Bielefeld; Justin Brockman; Markus Kuhn (545-551).
In order to understand the fundamental charge transport in a-B:H and a-BX:H (X = C, N, P) compound heterostructure devices, X-ray photoelectron spectroscopy has been utilized to determine the valence band offset and Schottky barrier present at amorphous boron compound interfaces formed with (1 0 0) Si and polished poly-crystalline Cu substrates. For interfaces formed by plasma enhanced chemical vapor deposition of a-B4–5C:H on (1 0 0) Si, relatively small valence band offsets of 0.2 ± 0.2 eV were determined. For a-B:H/Cu interfaces, a more significant Schottky barrier of 0.8 ± 0.16 eV was measured. These results are in contrast to those observed for a-BN:H and BP where more significant band discontinuities (>1–2 eV) were observed for interfaces with Si and Cu.
Keywords: Boron; Carbide; XPS; Valence band offset; Amorphous;

High current pulsed electron beam (HCPEB) irradiation was conducted on a WC-6% Co hard alloy with accelerating voltage of 27 kV and pulse duration of 2.5 μs. The surface phase structure was examined by using glancing-angle X-ray diffraction (GAXRD), scanning electron microscope (SEM) and high resolution transmission electron microscope (HRTEM) methods. The surface tribological properties were measured. It was found that after 20 pulses of HCPEB irradiation, the surface structure of WC/Co hard alloy was modified dramatically and composed of a mixture of nano-grained WC1−x , Co3W9C4, Co3W3C phases and graphite precipitate domains ∼50 nm. The friction coefficient of modified surface decreased to ∼0.38 from 0.6 of the initial state, and the wear rate reduced from 8.4 × 10−5  mm3/min to 6.3 × 10−6  mm3/min, showing a significant self-lubricating effect.
Keywords: High current pulsed electron beam; Surface modification; WC/Co hard alloy; Nanostructure; Tribological property;

Titanium hydride films irradiated by intense pulsed ion beam have been investigated by using scanning electronic microscopy, surface profilometer, X-ray diffraction and secondary ion mass spectroscopy in order to explore the mechanisms of interactions between intense pulsed ion beam and titanium hydride. Three sets of titanium hydride films are irradiated respectively for several times at energy density of 0.1 J/cm2, 0.3 J/cm2 and 0.5 J/cm2. Surface morphologies start to reveal a feature of intense melting and network cracks only after energy density reaches close to 0.5 J/cm2. Additionally, desorption of hydrogen from the film has been confirmed by X-ray diffraction, and a titanium dihydride (TiH2(x)) with a body centered tetragonal structure, seldom reported by researchers and formed under extreme conditions, has also been identified under this condition. Depth profile of hydrogen isotope with secondary ion mass spectroscopy seems to suggest that the bulk hydrogen isotope seems to serve as a reservoir for the drainage of top hydrogen, and its fast diffusion can quickly compensate for the exhaustion of top hydrogen isotope atoms.
Keywords: Titanium hydride; Pulsed ion beam; XRD; Secondary ion mass spectroscopy;

Role of nanocrystalline ZnO coating on the stability of porous silicon formed on textured (1 0 0) Si by Daisy Verma; Shailesh N. Sharma; Aneeta Kharkwal; G. Bhagavannarayana; Mahesh Kumar; Shiv Nath Singh; Parakram Kumar Singh; Syed Sazad Mehdib; Mushahid Husain (564-571).
In this study, a colloid of nanocrystalline ZnO particles prepared by chemical route is sprayed on porous silicon layers. Porosity and thickness of PS layers were estimated by gravimetric analysis. Upon adsorption of ZnO colloids on PS films, oxidation of nanocrystalline Si causes shrinkage of the Si-core due to the breaking of Si―Si bonds resulting in a blue-shift in PL spectra. The PL blue-shift can also be related to Si―O species or due to defects and the silica networks on which OH groups are absorbed due to ZnO incorporation as also supported by our Fourier transform infrared (FTIR) and X-ray photoelectron (XPS) studies, respectively. From high resolution X-ray diffraction (HRXRD) studies, a better crystalline perfection and considerable reduction in stress/strain values were observed for PS/ZnO layers as compared to virgin PS layers. The changes in the chemical composition at the surface of PS upon adsorption of ZnO colloids as elucidated by FTIR and XPS studies could be responsible for different PL emission and lattice-mismatch characteristics. The improved stability properties of PS are attributed to the strong absorption/adsorption of ZnO into the highly porous vertical layers separating macroscopic domains of nanoporous silicon and the mechanism of light emission from PS/ZnO layers is discussed on the basis of proposed energy band gap diagram.
Keywords: Colloids; ZnO; Porous silicon; Stability; PL; XPS and FTIR;

Modulation of porphyrin photoluminescence by nanoscale spacers on silicon substrates by Y.C. Fang; Y. Zhang; H.Y. Gao; L.G. Chen; B. Gao; W.Z. He; Q.S. Meng; C. Zhang; Z.C. Dong (572-576).
We investigate photoluminescence (PL) properties of quasi-monolayered tetraphenyl porphyrin (TPP) molecules on silicon substrates modulated by three different nanoscale spacers: native oxide layer (NOL), hydrogen (H)-passivated layer, and Ag nanoparticle (AgNP) thin film, respectively. In comparison with the PL intensity from the TPP molecules on the NOL-covered silicon, the fluorescence intensity from the molecules on the AgNP-covered surface was greatly enhanced while that for the H-passivated surface was found dramatically suppressed. Time-resolved fluorescence spectra indicated shortened lifetimes for TPP molecules in both cases, but the decay kinetics is believed to be different. The suppressed emission for the H-passivated sample was attributed to the weaker decoupling effect of the monolayer of hydrogen atoms as compared to the NOL, leading to increased nonradiative decay rate; whereas the enhanced fluorescence with shortened lifetime for the AgNP-covered sample is attributed not only to the resonant excitation by local surface plasmons, but also to the increased radiative decay rate originating from the emission enhancement in plasmonic “hot-spots”.
Keywords: Photoluminescence; Time-resolved fluorescence; Porphyrin, Ag nanoparticles; Surface plasmon; Hydrogen passivation;

ZnO/Al2O3 composite coatings were fabricated by atmospheric plasma spraying technology (APS). The effects of annealing temperature and atmospheres (in air or vacuum) on the microstructure and phase transformation of the sprayed coatings were studied by scanning electron microscope (SEM) and X-ray diffraction spectroscopy (XRD). The microwave dielectric properties of these coatings after annealing treatment were also discussed in the frequency range of 8.2–12.4 GHz. Both the real part and the imaginary part of the permittivity decreased significantly with increased annealing temperature when the annealing process is carried out in air atmosphere, while the complex permittivity of the coating annealed in vacuum atmosphere was obviously increased compared to the initial sprayed coating. The mechanism for the variation of dielectric properties of sprayed ZnO/Al2O3 composite coating caused by annealing treatment was discussed in this study.
Keywords: ZnO/Al2O3 composite coating; Plasma spraying; Annealing treatment; Dielectric properties; High-temperature absorbing material;

Facile approach in fabricating superhydrophobic ZnO/polystyrene nanocomposite coating by Yongquan Qing; Yansheng Zheng; Chuanbo Hu; Yong Wang; Yi He; Yong Gong; Qian Mo (583-587).
In this paper, we report a simple and inexpensive method for fabricating modified-ZnO/polystyrene superhydrophobic surface on the cotton textiles. The surface wettability and topology of coating were characterized by contact angle measurement, Scanning electron microscope and Fourier transform infrared spectrometry. The results showed that the hydrophobic ―CH3 and ―CF2 ― group was introduced into ZnO particles via modification, the ZnO nanoparticles were modified from hydrophilic to hydrophobic. When the weight ratio of modified-ZnO to polystyrene was 7:3, the ZnO/polystyrene composite coating contact angle was 158°, coating surface with hierarchical micro/nano structures. Furthermore, the superhydrophobic cotton texiles have a very extensive application prospect in water–oil separation.
Keywords: Superhydrophobic coating; Polystyrene; ZnO nanoparticles; Water–oil separation; Micro/nano structures;

Nonlinear waves generated on liquid silicon layer by femtosecond laser pulses by S. Lugomer; A. Maksimović; Z. Geretovszky; T. Szörényi (588-599).
Two-dimensional nonlinear waves are generated by multipulse femtosecond ultraviolet laser irradiation of silicon above the ablation threshold. The train of 120–190 pulses generates the unidirectional cnoidal-like waves as well as the Y- and X-type configurations. In the region of high laser intensity, the interaction of line solitary-like waves give rise to the complex network structure. For 200 ≤  N  < 220, the transition from stable into unstable waves takes place. At the critical number of pulses (≥230), the catastrophic destruction of cnoidal-like and solitary-like waves, takes place. Thus, the number of pulses plays the role of the control parameter. The stable cnoidal-like and solitary-like waves in a thin layer of molten silicon are reproduced by using the Kadomtsev–Petviashvili equation with negative dispersion (KP-II), and the unstable ones by using the KP-I equation with positive dispersion.
Keywords: Nonlinear waves; Kadomtsev–Petviashvili equation; Femtosecond laser interaction; Silicon surface; Atomic force microscopy;

Experimental research on laser shock forming metal foils with femtosecond laser by Y.X. Ye; Y.Y. Feng; X.J. Hua; Z.C. Lian (600-606).
Laser shock forming metal foils with femtosecond (fs) laser has been investigated experimentally in this article. A new transparent material was used as confining layer. Two destroying mechanisms of the confining layer have been observed and analyzed. With appropriate processing parameters, we have validated that macro plastic deformations (micro dents) can be formed on metal foils through fs laser-induced shock wave. Surface morphologies and 3D profiles of dents were measured. Results show that there exists a relatively optimum pulse range for obtaining better shock effects. Too short pulse duration will induce serious nonlinear absorption of confining layer, while too large pulse duration will decrease light intensities. Both are detrimental for improving laser shock effect. One abnormal phenomenon about the influence of impact times on dent depths has been found. Through analysis and experiments, we analyzed that loose constraint condition of samples led to flattening effect on deeper dents and then decrease the dent depths. Confining layer can significantly enhance laser shock effect and improve plastic deformation, which is same as ns laser. The new confining layer has been proved to be suitable for fs laser shock forming.
Keywords: Femtosecond laser; Laser shock forming; Plastic deformation; Metal foils;

Residual stress distribution of Ti-6Al-4V alloy under different ns-LSP processing parameters by K.Y. Luo; J.Z. Lu; Q.W. Wang; M. Luo; H. Qi; J.Z. Zhou (607-615).
A finite element modeling (FEM) model is developed to simulate the effects of overlapping rate, laser spot diameter and laser power density on residual stress of Ti-6Al-4V alloy at the surface and in the depth direction using ABQUAS software, and a simulated residual stress field is analyzed and compared with the experimental data. Results showed the fluctuation ratio of surface residual stress decreases gradually with increasing overlapping rate. The increment of laser power density can increase the affected depth of residual stress, and the higher value of surface residual stress can be obtained by increasing laser spot diameter when laser power density remains unchanged. In addition, the influence mechanism of overlapping LSP impacts on Ti-6Al-4V alloy is clearly also investigated.
Keywords: Laser shock processing; Residual stress field; Ti-6Al-4V alloy; Overlapping rate;

Design of H3PW12O40/TiO2 nano-photocatalyst for efficient photocatalysis under simulated sunlight irradiation by Kun Zhao; Ying Lu; Nan Lu; Yahui Zhao; Xing Yuan; Hao Zhang; Lianghui Teng; Fu Li (616-624).
H3PW12O40/TiO2 (PW12/TiO2) nano-photocatalyst was successfully synthesized through a modified sol–gel-hydrothermal method. The X-ray diffraction (XRD) patterns, Fourier transform infrared (FT-IR) spectra, UV–vis diffuse reflectance spectrum (UV–vis DRS), and N2 adsorption–desorption isotherms were characterized respectively to investigate the physical and chemical properties of prepared catalysts. Under simulated sunlight (320 nm <  λ  < 780 nm) irradiation, the degradation of fuchsin acid, malachite green and p-nitrophenol (PNP) were carried out to evaluate the photocatalytic activity of PW12/TiO2. The results showed that the pollutants degradation followed first-order kinetics, and the kinetic constants of photocatalytic degradation of fuchsin acid, malachite green and PNP were 2.82, 4.66, and 3.48 times as great as that using pristine TiO2, respectively. The high pollutants degradation efficiency was ascribed to the synergistic effect between H3PW12O40 and TiO2, which resulted in enhanced quantum efficiency and high light harvesting efficiency. We believe this work could provide new insights into the fabrication of photocatalyst with high photocatalytic performance and facilitate their practical application in environmental issues.
Keywords: H3PW12O40/TiO2 nano-photocatalyst; Fuchsin acid; Malachite green; Quantum efficiency; Light harvesting efficiency; Photocatalytic activity;

Electronic transport properties in aluminum indium nitride nanorods grown by magnetron sputter epitaxy by Ruei-San Chen; Chih-Che Tang; Ching-Lien Hsiao; Per Olof Holtz; Jens Birch (625-628).
The electronic transport properties of the wide-bandgap aluminum indium nitride (AlInN) nanorods (NRs) grown by ultrahigh-vacuum magnetron sputter epitaxy (MSE) have been studied. The conductivities of the ternary compound nanostructure locates at the value of 15 Ω−1  cm−1, which is respectively one and two orders of magnitude lower than the binary GaN and InN counterparts grown by chemical vapor deposition (CVD). The very shallow donor level/band with the activation energy at 11 ± 2 meV was obtained by the temperature-dependent measurement. In addition, the photoconductivity has also been investigated. The photoconductive (PC) gain of the NRs device can reach near 2400 under a low bias at 0.1 V and the light intensity at 100 W m−2 for ultraviolet response in vacuum. The power-insensitive gain and ambience-dependent photocurrent are also observed, which is attributed to the probable surface-controlled PC mechanism in this ternary nitride nanostructure.
Keywords: Aluminum indium nitride; Nanorod; Photoconductivity; Magnetron sputter epitaxy;

Surface integrity after pickling and anodization of Ti–6Al–4V titanium alloy by Eric Vermesse; Catherine Mabru; Laurent Arurault (629-637).
The surface integrity of Ti–6Al–4V titanium alloy was studied at different stages of surface treatments, especially pickling and compact anodization, through surface characteristics potentially worsening fatigue resistance.No significant changes of the equiaxe microstructure were detected between sample core and surface, or after the pickling and anodization steps. Surface hydrogen and oxygen superficial contents were found to remain unchanged. Roughness characteristics (i.e. R a, R z but also local K t factor) similarly showed only slight modifications, although SPM and SEM revealed certain random local surface defaults, i.e. pits about 400 nm in depth. Finally internal stresses, evaluated using X-ray diffraction, highlighted a significant decrease of the compressive internal stresses, potentially detrimental for fatigue resistance.
Keywords: Titanium alloy; Pickling; Anodization; Roughness; Internal stresses;

AFM friction and adhesion mapping of the substructures of human hair cuticles by James R. Smith; John Tsibouklis; Thomas G. Nevell; Steven Breakspear (638-644).
Using atomic force microscopy, values of the microscale friction coefficient, the tip (silicon nitride) - surface adhesion force and the corresponding adhesion energy, for the substructures that constitute the surface of human hair (European brown hair) have been determined from Amonton plots. The values, mapped for comparison with surface topography, corresponded qualitatively with the substructures’ plane surface characteristics. Localised maps and values of the frictional coefficient, extracted avoiding scale edge effects, are likely to inform the formulation of hair-care products and treatments.
Keywords: Atomic force microscopy; AFM; Friction coefficient; Human hair cuticle.;

Comparative study of the tribological behavior under hybrid lubrication of diamond-like carbon films with different adhesion interfaces by R.P.C. Costa; D.A. Lima-Oliveira; F.R. Marciano; A.O. Lobo; E.J. Corat; V.J. Trava-Airoldi (645-648).
This paper reports the influence of the adhesion interlayer between stainless steel and diamond-like carbon (DLC) films in two different contact conditions: in dry air and deionized water. The water was the liquid used to understand the mechanism and chemical reactions of the tribolayer formation under boundary lubrication. The effect of silicon and carbonitride adhesion interlayer was investigated on uncoated and coated DLC films. The results show that DLC/DLC pairs using carbonitride in air (30% RH) showed 60% less friction coefficient and wear less than three orders of magnitude than DLC/DLC pairs using silicon as interlayer. In deionized water, DLC/DLC pairs using carbonitride as interlayer showed 31% less friction coefficient when compared to DLC/DLC pairs with silicon. Raman related the chemical and structural changes in the DLC films during sliding in air and in the presence of water. Scratch tests showed a critical load of 14 N and 33 N in DLC films with silicon and carbonitride, respectively.
Keywords: Diamond-like carbon; Adhesion interlayer; Tribological properties and hybrid lubrication;

The localized surface plasmon resonance (LSPR) properties and local electric field distributions of the gold nanodumbbell are theoretically studied by using the finite-difference time-domain (FDTD) calculation. The decrease of both positive curvature radius in the spherical end and the negative curvature radius in the midsection results in the absorption peak corresponding to longitudinal plasmon mode red shifts distinctly. However, the transverse plasmonic absorption peak is not sensitive to the change of the curvature radii. The physical mechanism has been illuminated by studying the shape transformation dependent local field distribution between nanorod and nanodimer. It has been found that the decrease of the radii of curvature leads to the dumbbell-shaped particle transforming to a dimer-like structure, while the change in inter-particle plasmon coupling results in the “hot spots” of the local field migrating from the spherical ends to the midsection of the particle. There is an associated red shift of longitudinal LSPR. These results indicate that the transition of surface curvature between positive and negative greatly affects the surface charge distribution, local field enhancement and plasmon coupling.
Keywords: Gold nanodumbbell; Localized surface plasmon resonance (LSPR); Surface curvature radius; Local field distribution;

Thermoelectric properties of bismuth-selenide films with controlled morphology and texture grown using pulsed laser deposition by Phuoc Huu Le; Chien-Neng Liao; Chih Wei Luo; Jiunn-Yuan Lin; Jihperng Leu (657-663).
Polycrystalline, thermoelectric thin films of bismuth selenide (Bi2Se3) were grown on SiO2/Si (1 1 1) substrates, using pulsed laser deposition (PLD). Bi2Se3 films with highly c-axis-oriented and controlled textures were fabricated by maintaining the helium gas pressure (P) between 0.7 and 173 Pa and the substrate temperature (T s) between 200 and 350 °C. The carrier concentration (n) of films decreased with increasing P, which was attributed to the increase of Se concentration from Se deficiency (P  ≤ 6.7 Pa) to stoichiometry to slight Se enrichment (P  ≥ 40 Pa). The Seebeck coefficient (S) was enhanced considerably because of the reduction in n, following the S  ∼  n 2/3 relation approximately. The average grain size increased from approximately 100 to 500 nm when T s was raised from 200 to 350 °C, resulting in enhanced carrier mobility (μ) and electrical conductivity (σ) and a reduced full width at half maximum of (0 0 6) peaks. The shape of grains transformed from rice-like at T s of 200–250 °C to layered-hexagonal platelets (L-HPs) or super-layered flakes (S-LFs) at T s of 300–350 °C. Films that were grown at 300 °C and 40 Pa and contained highly c-axis oriented L-HPs possessed the highest power factor (PF =  S 2 σ), which reached 5.54 μW cm−1  K−2, where S  = 75.8 μV/K and σ  = 963.8 S cm−1.
Keywords: Bi2Se3; Thermoelectric properties; Nanostructure morphologies; Pulsed laser deposition (PLD); SiO2/Si(1 1 1) substrates;

Bio-absorbable magnesium (Mg) based alloys have been introduced as innovative orthopedic implants during recent years. It has been specified that rapid degradation of Mg based alloys in physiological environment should be restrained in order to be utilized in orthopedic trauma fixation and vascular intervention. In this developing field of healthcare materials, micro-arc oxidation (MAO), and MgF2 conversion coating were exploited as surface pre-treatment of AZ91 magnesium alloy to generate a nanostructured hydroxyapatite (n-HAp) coating via electrophoretic deposition (EPD) method. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy (TEM) techniques were used to characterize the obtained powder and coatings. The potentiodynamic polarization tests were carried out to evaluate the corrosion behavior of the coated and uncoated specimens, and in vitro bioactivity evaluation were performed in simulated body fluid. Results revealed that the MAO/n-HAp coated AZ91 Mg alloy samples with a rough topography and lower corrosion current density leads to a lower Mg degradation rate accompanied by high bioactivity.
Keywords: Magnesium; Bio-degradable implant; Nanostructured hydroxyapatite; Electrophoretic deposition; Micro arc oxidation; Fluoride conversion coating;

The corrosion inhibition characteristics of cation-rich and anion-rich catanionic mixtures of cetyltrimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS), as corrosion inhibitor of mild steel (MS), in aqueous solution of 3.5% NaCl were investigated using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and scanning electron microscopy (SEM). Solutions of CTAB/SDS mixtures showed more appropriate inhibition properties compared to the solutions of the individual surfactants, due to strong adsorption on the metal surface and formation of a protective film. Potentiodynamic polarization investigations indicated that the inhibitors studied were mixed type inhibitors. Adsorption of the inhibitors on the mild steel surface obeyed the Flory–Huggins adsorption isotherm. Furthermore, the values of the adsorption free energy (ΔG°ads) in both mixtures decreased compared with a single surfactant which is attributed to stronger interactions in mixtures.
Keywords: Corrosion; Inhibition; Surfactant; Adsorption isotherm;

Control wetting state transition by micro-rod geometry by Yang He; Chengyu Jiang; Shengkun Wang; Hengxu Yin; Weizheng Yuan (682-687).
Understanding the effect of micro-structure geometry on wetting state transition is important to design and control surface wettability. Micro-rod model was proposed and the relationship between micro-rod geometry and wetting state was investigated in the paper taking into account only the surface roughness and neglecting the chemistry interaction. Micro-rods with different geometric parameters were fabricated using micro-fabrication technology. Their contact angles were measured and compared with theoretical ones. The experimental results indicated that increasing the height and decreasing the space of micro-rod may result in Cassie wetting state, while decreasing the height and increasing the space may result in Wenzel wetting state. A suspended wetting state model due to scallops was proposed. The wetting state transition was interpreted by intruding height, de-pinning and sag mechanism. It may offer a facile way to control the surface wetting state transition by changing the geometry of micro-rod.
Keywords: Micro-rod; Geometry; Wetting state;

On sol–gel derived Au-enriched TiO2 and TiO2-ZrO2 photocatalysts and their investigation in photocatalytic reduction of carbon dioxide by Lenka Matějová; Kamila Kočí; Martin Reli; Libor Čapek; Vlastimil Matějka; Olga Šolcová; Lucie Obalová (688-696).
Gold-enriched TiO2 and TiO2-ZrO2 and their parent counterparts were prepared by using the sol–gel process controlled within the reverse micelles environment, followed by impregnation in AuCl3 solution. Catalysts were characterized by organic elementary analysis (OEA), inductively coupled plasma mass spectrometry (ICP MS), N2 physisorption, powder X-ray diffraction (XRD), transmission electron microscopy (TEM) combined with electron diffraction, UV–vis spectroscopy, and tested in CO2 photocatalytic reduction. The performance of photocatalysts iluminated by UV-lamp with the wavelenght maximum at 254 nm was decreasing in the order TiO2-ZrO2  > Au/TiO2-ZrO2  > TiO2  > Au/TiO2  > TiO2 Evonic P25. The photocatalytic performance decrease over Au/TiO2-ZrO2 and Au/TiO2, compared to their parent counterparts, can be explained by the presence of too large Au particles, which block the oxide surface and either reduce the light absorption capability of the catalysts, or serve as the recombination centres. Higher photocatalytic performance of the amorphous TiO2-ZrO2 than of the nanocrystalline TiO2 can be ascribed to the enlarged surface area and higher photoactivity of titania-zirconia oxide mixture under the UV lamp with the wavelenght maximum at 254 nm. With regard to crystalline materials the appropriate anatase crystallite-size plays a key role in performance of CO2 photocatalytic reduction. Moreover, correlation between the adsorption edge and the anatase crystallite-size was revealed.
Keywords: Gold; Titania-zirconia; Carbon dioxide; Photocatalysis; Microstructure; Optical properties;

KMnO4-treated, functionalized, biaxially oriented polypropylene (BOPP) films coated with nano-silica hybrid material were synthesized. The abrasion resistance of the films was examined using a reciprocating fabric abrasion tester. Functional groups were confirmed by Fourier-transform infrared spectroscopy. Contact angle measurements were performed on the BOPP film surface to quantify the effectiveness of the functionalization. Results indicate that the abrasion resistance and roughness of the composite film were significantly affected by the modification of the BOPP film. Water surface contact angle of the modified BOPP films decreased from 90.1° to 71.4°,when KMnO4 concentration increased from 0 M to 0.25 M. Wettability of the BOPP films clearly improved after KMnO4 treatment. Abrasion resistance of the functionalized films coated with hybrid materials improved by 27.4% compared with that of the original film.
Keywords: Abrasion resistance; Biaxially oriented polypropylene; Sol–gel; Surface modification; KMnO4;

Copper doped ZnO nanoparticles embedded on multi-walled carbon nanotubes (CNTs) were successfully synthesized using a facile, nontoxic sol method. The resulting visible light-responsive Cu-doped ZnO/CNTs composites were characterized using powder X-ray diffraction (XRD), high resolution transmission electron microscope (HR-TEM), transmission electron microscope (TEM), scanning electron microscope (SEM) with energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS) and Brunauer Emmett Teller (BET) surface area analyzer. Optical properties of Cu-doped ZnO/CNTs nanocomposites, studied using UV–vis diffuse reflectance spectroscopy and photoluminescence spectroscopy (PL), which exhibited extended light absorption in visible light region and possessed better charge separation capability, respectively as compared to Cu-doped ZnO, pure ZnO and ZnO/CNTs composite. The photocatalytic activity was tested by degradation of methyl orange (MO) dye under visible light irradiation. The results demonstrated that Cu-doped ZnO/CNTs nanocomposites effectively bleached out MO, showing an impressive photocatalytic enhancement over ZnO, commercial ZnO, Cu-doped ZnO nanoparticles and ZnO/CNTs nanocomposites. Chemical oxygen demand (COD) of textile wastewater was also measured before and after the photocatalysis experiment under sunlight to evaluate the mineralization of wastewater. The significant decrease in COD of the treated effluent revealed a complete destruction of the organic molecules along with color removal. This dramatically enhanced photoactivity of nanocomposite photocatalysts was attributed to greater adsorptivity of dyes, extended light absorption and increased charge separation efficiency due to excellent electrical properties of carbon nanotubes and the large surface area.
Keywords: Cu-doped ZnO; Photocatalysis; Methyl orange; Carbon nanotubes; COD;

Investigation on thermal stability of Ta2O5, TiO2 and Al2O3 coatings for application at high temperature by Peng Shang; Shengming Xiong; Linghui Li; Dong Tian; Wanjun Ai (713-720).
In this paper, tantalum pentoxide (Ta2O5), titanium dioxide (TiO2) and aluminum oxide (Al2O3) coatings are deposited on silicon substrates by ion beam sputtering (IBS). The influences of the thermal exposure at high temperature in air on the surface morphology, roughness, and the structure were investigated. The results indicate that the chemical composition of the as-deposited TiO2 and Ta2O5 coatings are apparently close to the stoichiometry ratios and both of them are amorphous structures. The peaks corresponding to anatase TiO2 appear at 400 °C while the anatase-to-rutile transformation is not observed after 800 °C and 1000 °C bake. Ta2O5 coating crystallizes at 800 °C and 1000 °C to form the hexagonal structure and orthorhombic structure, respectively. TiO2 and Al2O3 single layers all develop catastrophic damage at 400 °C in the form of noted spallation or blisters, whereas there is no visible damage for the Ta2O5 coating even at 1000 °C. To understand possible damage mechanisms, the thermal stress distributions through the thickness of Ta2O5 and TiO2 coatings and the influence of the microstructure transformation are discussed. Finally, some possible approaches to improve the thermal stability are also proposed.
Keywords: Thermal stability; TiO2/Ta2O5/Al2O3; Coating; Mismatch;

Fe-incorporated silica-pillared clays (Fe-SPCs) with ordered interlayer mesoporous structure have been synthesized through a new two-step procedure including the modification of the silica nano-pillars with potassium ferricyanide (K3Fe(CN)6) and successive calcination. X-ray diffraction, nitrogen adsorption–desorption, Fourier transform infrared spectra, X-ray fluorescence analyses, diffuse reflectance UV–vis spectra and X-ray absorption near-edge structure spectra were used to characterize the structures and the synthesizing mechanism of Fe-SPCs. Results show that all iron species were tetrahedrally coordinated with the interlayer silica nano-pillars, and the cationic surfactant molecule plays an important role in the intercalation of tetraethoxysilane and the introduction of iron into the intragallery silica framework. Moreover, the structural parameters of Fe-SPC can be adjusted by controlling the concentration of K3Fe(CN)6, as the concentration of K3Fe(CN)6 increases from 1 M to 2 M, the gallery height of Fe-SPC increases from 2.51 to 2.66 nm, while the Brunauer–Emmett–Teller (BET) surface area, pore volume and Barrett–Joyner–Halenda (BJH) pore size decrease from 856 to 794 m2/g, 0.75 to 0.69 cm3/g, and 2.2 to 2.0 nm, respectively. The Fe-SPCs show good catalytic activity in phenol hydroxylation using H2O2 as oxidant (phenol:H2O2  = 1:1, water), specifically, the phenol conversion is 46.2%, and the selectivity of dihydroxybenzenes is 70.6% at 343 K.
Keywords: Tetrahedral coordination; Iron incorporation; Silica-pillared clay; Phenol hydroxylation; Catalyst;

Preparation and properties of UV curable acrylic PSA by vinyl bonded graphene oxide by Beili Pang; Chong-Min Ryu; Xin Jin; Hyung-Il Kim (727-731).
Graphene oxide was modified to carry the vinyl groups on the surface for UV curing. UV-cured graphene oxide/acrylic PSA composites showed the thermal stability suitable for handling of thin silicon wafers.Acrylic pressure sensitive adhesives (PSAs) with higher thermal stability for thin wafer handling were successfully prepared by forming composite with the graphene oxide (GO) nanoparticles modified to have vinyl groups via subsequent reaction with isophorone diisocyanate and 2-hydroxyethyl methacrylate. The acrylic copolymer was synthesized as a base resin for PSAs by solution radical polymerization of ethyl acrylate, 2-ethylhexyl acrylate, and acrylic acid followed by further modification with GMA to have the vinyl groups available for UV curing. The peel strength of PSA decreased with the increase of gel content which was dependent on both modified GO content and UV dose. Thermal stability of UV-cured PSA was improved noticeably with increasing the modified GO content mainly due to the strong and extensive interfacial bonding formed between the acrylic copolymer matrix and GO fillers
Keywords: Pressure sensitive adhesive; Thermal stability; Modified graphene oxide; Acrylic copolymer; UV curing;

Sol–gel derived ZnO thin films: Effect of amino-additives by P. Hosseini Vajargah; H. Abdizadeh; R. Ebrahimifard; M.R. Golobostanfard (732-743).
Zinc oxide thin films were dip-coated from an alcoholic sol of zinc acetate with different amino-additives including monoethanolamine, diethanolamine, triethanolamine, triethylamine, and ethylenediamine. Sol–gel behavior, crystal structure, optoelectronic and morphological properties of thin films were investigated with focus on the effects of different amines and drying conditions. Investigations explicate the role of chemical and physical properties of amines such as organic chains, polarity, and boiling point as the main factors that cause distinct sol–gel behavior and film properties. It is shown that different amines in different molar ratios together with drying temperature cause dramatic impacts on sol transparency, stability, and consequently on structural, optoelectronic, and morphological properties of films. Notably, monoethanolamine and triethylamine films demonstrate a preferred orientation stimulated by increased molar ratio of amines. Further investigations indicated the positive effect of elevated drying temperature particularly on those films prepared from sols with high-boiling-point stabilizers. The variation of film optoelectronics seems to depend mainly on heat treatment, whereas sol chemistry influences the optical properties indirectly through the structural alteration. Peculiar morphologies in the ethylenediamine films disappeared with adjusting the drying conditions. The size of ZnO grains were approximately independent of amine types and primarily affected by the heat treatment
Keywords: ZnO sol–gel growth; Amino-additives; Thin film; Preferred orientation;

Improved energy storage properties of PbZrO3 thin films by inserting 0.88BaTiO3–0.12Bi(Mg1/2,Ti1/2)O3 layer by T. Chen; J.B. Wang; X.L. Zhong; Y.K. Zeng; F. Wang; Y.C. Zhou (744-747).
Trilayered PbZrO3/0.88BaTiO3–0.12Bi(Mg1/2,Ti1/2)O3/PbZrO3 (PZ/BT-BMT/PZ) thin films have been fabricated on Pt (1 1 1)/Ti/SiO2/Si substrates by sol–gel method. Compared with the PZ thin films, the PZ/BT-BMT/PZ trilayered thin films exhibit greatly enhanced electric breakdown strength, polarization and energy storage density. The polarization and energy storage density of the PZ/BT-BMT/PZ trilayered thin films are 92.2 μC/cm2 and 19.88 J/cm3 at a maximum applied electric field of 750 kV/cm, respectively. Moreover, the PZ/BT-BMT/PZ trilayered thin films show much better fatigue resistance than the PZ thin films. After 1.45 × 108 switching the polarization only reduces 8.12% for trilayered thin films while it is 25% for the PZ thin films. In order to further improve the energy storage properties of the PZ/BT-BMT/PZ thin films, the annealing process has been optimized and the trilayered thin films were prepared by layer-by-layer annealing. The layer-by-layer annealed PZ/BT-BMT/PZ trilayered thin films exhibit better energy storage properties than the trilayered thin films annealed once, and a maximum energy storage density of 28.36 J/cm3 was obtained.
Keywords: Ferroelectric materials; Thin films; Multilayers; Energy storage density; Sol–gel;

Photoluminescence and SERS investigation of plasma treated ZnO nanorods by Szetsen Lee; Jr-Wei Peng; Chih-Sheng Liu (748-754).
Hydrothermally synthesized ZnO nanorods were treated with hydrogen and oxygen plasmas. We have found that the photoluminescence (PL) intensity of ZnO nanorods increases with hydrogen plasma treatment, but decreases after the subsequent treatment of oxygen plasma. There is no significant increase of PL intensity only by oxygen plasma treatment. By analyzing the components of the deep level emission band, we have concluded the plasma-induced PL intensity variation and band position shift are related to the existence of intrinsic defects in ZnO nanorods. H2 plasma reduces the concentration of oxygen vacancy or singly ionized oxygen vacancy, whereas O2 plasma increases the concentration of interstitial oxygen. The PL result is compared with surface-enhanced Raman scattering (SERS), X-ray power diffraction and scanning electron microscope characterization. We believe that plasma-induced defect formation in ZnO is also the reason responsible for the observed SERS intensity enhancement.
Keywords: ZnO; Photoluminescence; SERS; Plasma;

Low resistivity of N-doped Cu2O thin films deposited by rf-magnetron sputtering by Guozhong Lai; Yangwei Wu; Limei Lin; Yan Qu; Fachun Lai (755-758).
N-doped Cu2O films were deposited on quartz substrates by reactive magnetron sputtering with a Cu2O target. The structure, deposited rate, and electrical properties of the films were influenced by the partial pressure of nitrogen. It is found that the structure and electrical properties of the films in different nitrogen partial pressure could be divided into three stages: the low, middle, and highly N-doping ranges. The film deposited at nitrogen partial pressure of 0.035 Pa has the lowest resistivity (0.112 Ω cm).
Keywords: Cu2O; N-doped; Sputtering;

An amorphous Si―O film tribo-induced by natural hydrosilicate powders on ferrous surface by Baosen Zhang; Binshi Xu; Yi Xu; Zhixin Ba; Zhangzhong Wang (759-765).
The tribological properties of surface-coated serpentine powders suspended in oil were evaluated using an Optimal SRV-IV oscillating friction and wear tester. The worn surface and the tribo-induced protective film were characterized by scanning electron microscope and focused ion beam (SEM/FIB) work station, energy dispersive spectroscopy (EDS) and transmission electron microscope (TEM). Results indicate that with 0.5 wt% addition of serpentine powders to oil, the friction coefficient and wear rate significantly decrease referenced to those of the base oil alone. An amorphous SiO x film with amorphous SiO x particles inserted has formed on the worn surface undergoing the interactions between serpentine particles and friction surfaces. The protective film with excellent lubricating ability and mechanical properties is responsible for the reduced friction and wear.
Keywords: Serpentine; Lubricant; Additive; Friction and wear;

Polarity driven morphology of CeO2(1 0 0) islands on Cu(1 1 1) by O. Stetsovych; J. Beran; F. Dvořák; K. Mašek; J. Mysliveček; V. Matolín (766-771).
Thin ceria films supported by metal substrates represent important model systems for reactivity studies in heterogeneous catalysis. Here we report the growth study of the polar CeO2(1 0 0) phase as part of a mixed CeO2(1 1 1)–CeO2(1 0 0) thin film supported by Cu(1 1 1). The two ceria phases grow on different areas of the substrate, what allows a reliable growth characterization of the CeO2(1 0 0) islands on Cu(1 1 1). Scanning tunneling microscopy measurements reveal CeO2(1 0 0) to grow in the form of highly dispersed three dimensional (3D) islands on a CeO2(1 0 0) interfacial layer. The CeO2(1 0 0) islands exhibit a 2 × 2 surface reconstruction. The presence of the surface reconstruction together with the highly dispersed growth of CeO2(1 0 0) islands corresponds to the requirement for compensation of the surface dipole moment on the CeO2(1 0 0). CeO2(1 0 0) islands are further characterized by reflection high energy electron diffraction yielding their epitaxial relations with respect to the Cu(1 1 1) substrate. The growth of well characterized CeO2(1 0 0) islands supported by Cu(1 1 1) represents a starting point for developing a novel template for structure-related reactivity studies of ceria based model catalysts.
Keywords: CeO2(1 0 0); Growth; Morphology; Reconstruction; Polar oxide surface; Surface dipole stabilization;

Fabrication of nanorod InGaN/GaN multiple quantum wells with self-assembled Ni nano-island masks by Guofeng Yang; Ying Guo; Huaxin Zhu; Dawei Yan; Guohua Li; Shumei Gao; Kexiu Dong (772-777).
The evolution of nano-sized Ni metal islands deposited by electron-beam evaporation on InGaN/GaN multiple quantum wells (MQWs) surface as a function of rapid thermal annealing (RTA) temperature and initial deposited Ni film thickness is reported. It is shown that the dimension and density of self-assembled Ni nano-islands depend critically on the annealing temperature and deposited Ni film thickness. The formation of the islands is described in terms of Ostwald ripening and coarsening mechanisms. Subsequently, the nano-masks are successfully applied to fabricate nanorod InGaN/GaN MQWs by using inductively coupled-plasma (ICP) etching. Uniform etching rate has been obtained by comparing the nanorod height etched for different times. Photoluminescence (PL) investigation shows the nanorod MQWs with optimized light output efficiency could be acquired under particular ICP and RF etching power. Strain relaxation and dislocation reduction effect would contribute to enhanced light output of nanorod InGaN/GaN MQWs compared with the as-grown plane MQWs.
Keywords: Ni nano-island; Rapid thermal annealing; Inductively coupled-plasma etching; Nanorod; InGaN/GaN MQWs;

Influence of electropolishing current densities on sulfur generation at niobium surface by P.V. Tyagi; M. Nishiwaki; T. Noguchi; M. Sawabe; T. Saeki; H. Hayano; S. Kato (778-782).
We report the effect of different current densities on sulfur generation at Nb surface in the electropolishing (EP) with aged electrolyte. In this regard, we conducted a series of electropolishing (EP) experiments in aged EP electrolyte with high (≈50 mA/cm2) and low (≈30 mA/cm2) current densities on Nb surfaces. The experiments were carried out both for laboratory coupons and a real Nb single cell cavity with six witness samples located at three typical positions (equator, iris and beam pipe). Sample's surfaces were investigated by XPS (X-ray photoelectron spectroscopy), SEM (scanning electron microscope) and EDX (energy dispersive X-ray spectroscopy). The surface analysis showed that the EP with a high current density produced a huge amount of sulfate/sulfite particles at Nb surface whereas the EP with a low current density was very helpful to mitigate sulfate/sulfite at Nb surface in both the experiments.
Keywords: Nb electropolishing; Current density; SRF cavity; Surface finishing; Sulfur generation; Field emissions;

Sub-micron ZnO:N particles fabricated by low voltage electrical discharge lithography on Zn3N2 sputtered films by C. García Núñez; J. Jiménez-Trillo; M. García Vélez; J. Piqueras; J.L. Pau; C. Coya; A.L. Álvarez (783-788).
This work analyzes the morphological, compositional and electrical modification of zinc nitride (Zn3N2) films through arc discharges produced by biasing a metal tip at a micrometric distance of the surface. Polycrystalline nitride layers are prepared by radio-frequency magnetron sputtering from a pure Zn target on glass substrates using N2 as working gas. Film properties after arc discharges are investigated by using scanning electron microscopy (SEM), ion beam analysis (IBA) techniques and four-probe resistivity measurements. Electrical discharge lithography performed at low bias voltages reveals as an effective mechanism to reduce resistivity by electrical breakdown of the thin oxide layer formed on top of the nitride. At higher voltages, electrical discharges along the scan increase nitride resistivity due to the severe modification of the structural properties. Additionally, compositional analysis reveals that nitrogen leaves the structure being replaced by ambient oxygen. This characteristic behavior leads to the formation of facetted submicron ZnO crystals whose size depends on the original Zn3N2 grain size and the probe voltage used. The excess of zinc forms self-assembled microstructures along the scan edge.
Keywords: Zinc nitride; Zinc oxide; Magnetron sputtering; Microfabrication; Arc discharge lithography;

A successive embedding of N-doping and CaCO3 surface modification was carried out in the TiO2 photoelectrodes for dye-sensitized solar cells (DSSCs). The combined effect was revealed with the great increase of the open-circuit voltage (V oc ), short-circuit current (J sc ), and photoelectric conversion efficiency (η) of the prepared cells; the efficiency (η) was improved from 5.42% of a commercial TiO2 photoelectrode to 7.47% of an unmodified N-doped electrode, and to 9.03% of a N-doped and CaCO3 surface modified electrode. An enhanced photoresponse in N-doped TiO2 nanoparticles generate more photo-excited electrons in adsorbed dye, as supported by measured UV–vis diffuse reflectance spectra and incident photon to current conversion efficiency (IPCE). A successive CaCO3 surface modification then form a barrier on the surface of N-doped TiO2 particles, suppressing charge recombination of photo-generated electrons from N-doped TiO2 to dye or electrolyte, and thus extending their life time in the electrode, as supported by electron impedance spectroscopy (EIS). Furthermore, the higher basicity of the CaCO3 modified TiO2 facilitates the dye adsorption, as supported by the direct measurement of the amount of adsorbed dye.
Keywords: Dye-sensitized solar cells; TiO2; Nitrogen-doped; CaCO3; Surface modification; Charge recombination;

Investigation of thermally grown oxide on 4H-SiC by a combination of H2O and HNO3 vapor with varied HNO3 solution heating temperature by Banu Poobalan; Jeong Hyun Moon; Sang-Cheol Kim; Sung-Jae Joo; Wook Bahng; In Ho Kang; Nam-Kyun Kim; Kuan Yew Cheong (795-804).
A new technique of oxidizing n-type 4H-SiC in a combination of H2O and nitric acid (HNO3) vapor at various heating temperatures (60 °C, 70 °C, 80 °C, 90 °C, 100 °C and 110 °C) of HNO3 solution has been introduced in this work. Utilizing secondary ion mass spectroscopy, effects of H+ and N on the passivation of structural defects at the bulk oxide and partial of the SiC/SiO2 interface have been discussed. The effects of heating temperature of HNO3 solution on structural properties of the SiC substrate; after the oxide has been removed have been systematically investigated. Contact angles and the surface roughness of the substrate were recorded from a Goniometer and an atomic force microscope, respectively. It has been revealed that as compared to oxide grown by conventional wet (H2O vapor only) oxidation technique; this “wet diluted nitridation” technique is able to produce oxide with lower interface-state density and higher breakdown voltage. Physical properties of the substrate after oxide removal show surface roughness reduces as the heating temperature of HNO3 solution increases, which is mainly attributed by the significant reduction of carbon content at the SiC/SiO2 interface.
Keywords: Silicon carbide; Silicon dioxide; Wet nitridation; HNO3 vapor;

Catalytic oxidation of formaldehyde over Pt/Fe2O3 catalysts prepared by different method by Nihong An; Ping Wu; Suying Li; Mingjun Jia; Wenxiang Zhang (805-809).
Iron oxide supported platinum catalysts were prepared by different methods, including co-precipitation, impregnation and colloid deposition methods. The catalytic properties of these catalysts were investigated for the complete oxidation of formaldehyde. It is found that the catalyst prepared by colloid deposition method (Pt/Fe2O3-CD) exhibited relatively high catalytic activity, which could completely oxidize HCHO even at room temperature. Based on a variety of physical–chemical characterization results, it is proposed that the presence of suitable interaction between Pt particles and iron oxide supports (i.e., Pt―O―Fe), which would influence the structure and properties of iron oxide supports, should play a positive role in determining the catalytic activity of Pt/Fe2O3-CD catalyst.
Keywords: Pt catalysts; Formaldehyde oxidation; Metal-support interaction; Iron oxide;

Molecular dynamics simulations are carried out for describing deposition and annealing processes of AlCoCrCuFeNi high entropy alloy (HEA) thin films. Deposition results in the growth of HEA clusters. Further annealing between 300 K and 1500 K leads to a coalescence phenomenon, as described by successive jump in the root mean square displacement of atoms. The simulated X-ray diffraction patterns during annealing reproduces the main feature of the experiments: a phase transition of the cluster structure from bcc to fcc.
Keywords: Molecular dynamics simulation; Thin film growth; Cluster growth; High entropy alloy; Magnetron sputter deposition;

Characteristics of plate-like and color-zoning cubic boron nitride crystals by Shuang Feng; Lixin Hou; Xiuhuan Liu; Yanjun Gao; Xinlu Li; Qi Wang; Zhanguo Chen; Gang Jia; Jie Zheng (817-822).
The polarities of a kind of plate-like and color-zoning cubic boron nitride (cBN) crystal were extensively investigated by microscopy, chemical etching, XPS, Raman scattering, and current–voltage measurements. The {1 1 1}B faces and { 1 ¯ 1 ¯ 1 ¯ } N faces of the cBN samples can be easily distinguished by optical microscope as there are a lot of defects incorporate in { 1 ¯ 1 ¯ 1 ¯ } N sectors serving as the color centers, while the {1 1 1}B sectors have less defects and are nearly colorless. Both XPS and Raman spectra also revealed the uneven distributions of N vacancies and substitutional impurities in cBN crystals. The determination of {1 1 1}B faces and { 1 ¯ 1 ¯ 1 ¯ } N faces can also be verified by the results of the chemical etching because the { 1 ¯ 1 ¯ 1 ¯ } N faces have much faster etch rates than the {1 1 1}B faces. According to XPS, the {1 1 1}B faces have more C and O contaminations than the { 1 ¯ 1 ¯ 1 ¯ } N faces, however the { 1 ¯ 1 ¯ 1 ¯ } N faces have larger atomic ratio of B:N after surface cleaning by Ar+ sputtering. In the Raman spectra of the { 1 ¯ 1 ¯ 1 ¯ } N sectors of cBN, several small broad infrared-active phonon bands emerge nearby TO and LO modes because of the disorder-activated Raman scattering. As for the {1 1 1}B sectors, this phenomenon disappears. In addition, the {1 1 1}B faces have much smaller leakage current than the { 1 ¯ 1 ¯ 1 ¯ } N faces, which indicates that the {1 1 1}B sectors have higher crystalline quality.
Keywords: Wide bandgap semiconductors; III–V compounds; Cubic boron nitride; Surface polarity;

Nanoscale surface characterization of aqueous copper corrosion: Effects of immersion interval and orthophosphate concentration by Stephanie L. Daniels; Phillip T. Sprunger; Orhan Kizilkaya; Darren A. Lytle; Jayne C. Garno (823-831).
Morphology changes for copper surfaces exposed to different water parameters were investigated at the nanoscale with atomic force microscopy (AFM), as influenced by changes in pH and the levels of orthophosphate ions. Synthetic water samples were designed to mimic physiological chemistries for drinking water, both with and without addition of orthophosphate over a pH range 6.5–9. Copper surfaces treated with orthophosphate as a corrosion inhibitor after 6 and 24 h were evaluated. Tapping mode AFM images revealed dosing of the water with 6 mg/L of orthophosphate was beneficial in retarding the growth of copper by-products. The chemical composition and oxidation state of the surface deposits were characterized with X-ray diffraction (XRD), near edge X-ray absorption fine structure (NEXAFS) spectroscopy and Fourier transform infrared spectroscopy (FTIR).
Keywords: AFM; Copper corrosion; Drinking water; Inorganic contaminants and orthophosphate;

Conventional pressure water reactors like CANDU use Zircaloy-4 as a fuel cladding tube. Surface roughness that arises from the manufacturing process, pilgering, may alter these tubes’ properties in various ways. This paper presents a comparative study of cladding tubes with different surface conditions in order to investigate their effect on the Zircaloy-4 substrate and oxide textures as well as the oxidation kinetic. The experimental results reveal that surface roughness affects the oxidation rate and weight gain of the cladding tubes. Although surface polishing slightly changes the substrate texture, it induces no significant change in the oxide texture. Moreover, oxidation time does not significantly change the preferred orientation of the zirconium oxide.
Keywords: Zircaloy-4; Pilgering; Surface roughness; Oxidation kinetic; Zirconium oxide texture;

CdS nanoparticles/functionalized graphene sheets (CdS NPs/FGS) nanocomposites were successfully prepared in a one-step hydrothermal synthesis route. The photocatalytic performance of CdS NPs/FGS composites in degradation of methyl orange (MO) was examined utilization of visible light.CdS nanoparticle/functionalized graphene sheet (CdS NP/FGS) nanocomposites were successfully prepared in a one-step hydrothermal synthesis route. The samples were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, photoluminescence spectroscopy, and Raman spectroscopy. In addition, the photocatalytic performance of CdS NP/FGS composites and pure CdS in the degradation of methyl orange (MO) was examined using visible light. Results show that the addition of FGS can enhance the photocatalytic performance of CdS NP/FGS composites with a maximum degradation efficiency of 98.1% under visible light irradiation as compared with pure CdS (60.1%). This finding can be attributed to three reasons. First is the strong redox ability of CdS in the nanocomposite with smaller crystal size. Second is the increase in specific surface area for more adsorbed MO. Third is the reduction in electron–hole pair recombination with the introduction of FGS. Based on their high photocatalytic activity, the CdS NP/FGS composites can be expected to be a practical visible light photocatalyst.
Keywords: Functionalized graphene sheets; Cadmium sulfide; Methyl orange; Photodegradation property;

Surface diffusion and coverage effect of Li atom on graphene as studied by several density functional theory methods by Zhi Ji; Flavio F. Contreras-Torres; Abraham F. Jalbout; Alberto Ramírez-Treviño (846-852).
The adsorption of Li atom on graphene is examined using density functional theory methods. Three different adsorption sites are considered, including the on top of a carbon atom (OT), on top of a C―C bond (Bri), and on top of a hexagon (Hol), as well as Li adsorbed at different coverage. The Hol site is found to be the most stable, followed by the Bri and OT sites. The order of stabilization is independent of coverage. The localization of Li–graphene interaction at all sites has reverse order with stabilization. The localization will cause different repulsive interaction between Li atoms which is believed to take responsibility for the difference between the charge transfer order and adsorption energy order of Li adsorption at all possible sites. Repulsive interaction also causes the decreasing of adsorption energies of Li at Hol site with increasing coverage, but the corresponding influence is bigger at low coverage range (0.020–0.056 monolayers) than that at high coverage range (0.056–0.250 monolayers). The trend of charge transfer and dipole moment with increasing coverage is also in agreement with that of adsorption energy. It is also found that the distance of Li above graphene will increase with increasing coverage, but a so-called “zigzag” curve appears, which exhibits an oscillatory behavior as a function of increasing coverage. The diffusion of Li atom on graphene is also studied. Li atom migrates from a Hol site to a neighboring Hol site through the Bri site between them is found to be the minimum energy path. Within the studied coverage range, the diffusion barrier decreases with increasing coverage which can be ascribed to the phenomenon of different repulsion interactions when Li atom adsorbs at different sites. The increasing coverage amplified the phenomenon.
Keywords: Graphene; Lithium; Surface diffusion; Density functional theory;

Effect of inhomogeneity and plasmons on terahertz radiation from GaAs (1 0 0) surface coated with rough Au film by Xiaojun Wu; Baogang Quan; Xinlong Xu; Fangrong Hu; Xinchao Lu; Changzhi Gu; Li Wang (853-857).
We measured terahertz (THz) radiation from GaAs (1 0 0) surface coated with rough Au film in the thickness ranging from 5 to 21 nm under the incident angle from 0° to 50°. Anomalous THz emission was observed with inhomogeneous crack structures at normal incidence, which originates dominantly from the lateral photo-Dember current. Meanwhile, enhanced THz radiation from Au/GaAs was investigated with the variation of the Au morphology, which confirmed that localized surface plasmons play an important role in the THz radiation. The results indicate the prospect of harnessing surface plasmons for efficient THz emission with controllable morphology of Au on semiconductors.
Keywords: Semiconductor surface; THz radiation; Surface plasmon;

Automatic recognition method for hot-rolled steel strip surface defects is important to the steel surface inspection system. In order to improve the recognition rate, a new, simple, yet robust feature descriptor against noise named the adjacent evaluation completed local binary patterns (AECLBPs) is proposed for defect recognition. In the proposed approach, an adjacent evaluation window which is around the neighbor is constructed to modify the threshold scheme of the completed local binary pattern (CLBP). Experimental results demonstrate that the proposed approach presents the performance of defect recognition under the influence of the feature variations of the intra-class changes, the illumination and grayscale changes. Even in the toughest situation with additive Gaussian noise, the AECLBP can still achieve the moderate recognition accuracy. In addition, the strategy of using adjacent evaluation window can also be used in other methods of local binary pattern (LBP) variants.
Keywords: Surface defect; Automatic recognition; Adjacent evaluation; Local binary pattern;

Novel chitosan-modified magnetic graphitized multi-walled carbon nanotubes (CS-m-GMCNTs) were synthesized via a suspension cross-linking method. Composition, morphology and magnetic properties of as-prepared CS-m-GMCNTs were characterized by XRD, SEM-EDS, BET and VSM. The large saturation magnetization (12.27 emu g−1) allows fast separation of CS-m-GMCNTs from treated aqueous solution. The adsorption of congo red (CR) on CS-m-GMCNTs was strongly dependent on pH, temperature of the aqueous phase and adsorbent dosage. Up to 100 and 94.58% color removal could be achieved in 100 min contact time with 10 and 50 mg L−1 of initial concentrations, respectively. The adsorption capacity of CR onto CS-m-GMCNTs could reach 262.9 mg g−1. The pseudo-second-order kinetic model with high correlation coefficients (R 2  > 0.999) was suitable to describe the process of CR adsorption onto CS-m-GMCNTs. The Langmuir model fitted the adsorption isotherm data better than the Freundlich model. Values of thermodynamic parameters (ΔG°, ΔH° and ΔS°) indicated that the adsorption process was strongly dependent on temperature of the aqueous phase, and spontaneous and endothermic process in nature. Therefore, CS-m-GMCNTs adsorbent displays main advantages of excellent dispersion, convenience separation and high adsorption capacity, which implies their potential application in the environmental cleanup.
Keywords: Adsorption; Graphitized multi-walled carbon nanotubes; Magnetic separation; Dye; Chitosan;

Probing carbon coatings on nanoparticle decorated carbon nanotubes by scanning transmission X-ray microscopy by Ming Li; Jing Gao; Lili Bai; Aiwu Pu; Jinyin Liu; Guanqi Zhao; Xuhui Sun; Jun Zhong (874-878).
Two kinds of carbon coating on carbon nanotubes (CNTs) after decoration with nanoparticles were observed by scanning transmission X-ray microscopy with a concurrent characterization of the electronic structure, revealing the complex compositions in CNTs after chemical modification. Moreover, a sandwich structure shown as CNT-nanoparticle-coating can be created with the exposure to X-ray for CNTs decorated with nanoparticle outside the wall. The coating shows an effective way for site-selective modification of CNTs with various carbon structures.
Keywords: X-ray absorption near-edge structure (XANES); Carbon nanotubes; Nanoparticles; Carbon coating; Scanning transmission X-ray microscopy (STXM);

First-principles calculations on Mg/Al2CO interfaces by F. Wang; K. Li; N.G. Zhou (879-884).
The electronic structure, work of adhesion, and interfacial energy of the Mg(0 0 0 2)/Al2CO(0 0 0 1) interface were studied with the first-principles calculations to clarify the heterogeneous nucleation potential of Al2CO particles in Mg melt. AlO-terminated Al2CO(0 0 0 1) slabs with seven atomic layers were adopted for interfacial model geometries. Results show that the “Over O” stacking interface is more stable than the “Over Al” stacking interface due to the larger interfacial adhesion and stronger mixed ionic/metallic bond formed across the interface. The calculated interfacial energies of Mg/Al2CO depend on the value of Δμ Al  + Δμ C, proving Al2CO particles can exist stably in Mg–Al alloys melt and become effective nucleation substrate for α-Mg grain under certain conditions. The above calculation and corresponding analysis provide strong theoretical support to the Al2CO nucleus hypothesis from interfacial atomic structure and atomic bonding energy considerations.
Keywords: First-principles calculation; Interface; Al2CO; Grain refining; Magnesium alloy;

Polyethylene naphthalate as an excellent candidate for ripple nanopatterning by P. Slepička; O. Neděla; P. Sajdl; Z. Kolská; V. Švorčík (885-892).
The surface of polyethylene naphthalate (PEN) foils was exposed to KrF excimer laser treatment. Due to presence of condensed benzene rings has this polymer better mechanical, chemical and thermal properties in comparison to polyethylene terephthalate, which is widely applicable in electronic devices and also as tissue cell carriers. The influence of laser fluence and number of laser pulses on surface chemistry and morphology was determined. The surface morphology was studied with atomic force microscopy (AFM) in combination with scanning electron microscopy and focused ion beam (FIB-SEM). Surface wettability was characterized by the contact angle measurement. Surface chemistry was evaluated from XPS spectra. The optimal PEN process parameters with the most regular pattern were determined. The foils with optimal ripple pattern were consequently sputtered with gold nanolayers of 100 nm thickness. The parameters of ripple pattern after the metallization were introduced. It was found that the gold nanolayer is formed of electrically continuous wires, the ripple pattern was maintained.
Keywords: Polyethylene naphthalate; Excimer laser; Ripples; Gold; Sputtering; Surface properties;

Sticky nano-thin films for the adhesion of polymers by Firas Awaja; Shengnan Zhang; David R. McKenzie (893-899).
Nanometre thick size films (about 2 nm thick) that were plasma deposited using a mixture of polymerizing and non-polymerizing gases on a PEEK polymer surface resulted in a remarkable autohesive strength (up to 10 fold when compared with the untreated control). Experimental results on autohesion of semi-crystalline PEEK surfaces treated with plasma immersion ion implantation and deposition (PIIID) showed exceptionally strong autohesive bonds in lap-shear testing. Electron spin resonance (ESR) showed that the radical concentration increased linearly with plasma bias voltage. X-ray photoelectron spectroscopy (XPS) measurements showed no correlation between autohesive bonding strength and the concentration of oxygen and nitrogen elements and or the concentration of C―O functional groups on the surface. Contact angle measurements showed that surface energy also showed no correlation. Bond strength values are linked with the percentage of the sp3 components of the C 1s region fitting in XPS spectra. There was strong relationship between the plasma treatment bias voltage and the plasma generated free radical density in the deposited thin film. Bond strength values are also correlated with the percentage of the sp3 components of the C 1s region fitting in XPS spectra. Free radicals induced covalent bonding might be suggested as the major contributor that leads to that the remarkable increase of the adhesion strength.
Keywords: Nano-thin films; Free radical; Autohesion; ESR; PEEK;

Improvement on electrochemical performance by electrodeposition of polyaniline nanowires at the top end of sulfur electrode by Kai Zhang; Jie Li; Qiang Li; Jing Fang; Zhian Zhang; Yanqing Lai; Yujie Tian (900-906).
Herein, we introduce a modification of the sulfur electrode by electrodepositing a covering layer of polyaniline nanowires at the top end for Li–S batteries. The as-fabricated electrodes are evaluated via SEM, FTIR, EDAX, EIS, CV and charge–discharge tests. The SEM images combined with FTIR spectra show that the surface of the electrode is covered by the PANI nanowires. The charge–discharge tests of PANI-5 display the best cyclic performance, delivering the initial discharge capacity of 1304 mAh g−1, and 725 mAh g−1 after 100 cycles at the current density of 320 mA g−1. The CV results of the PANI-5 present an overlapping of cathodic/anodic peaks, indicating that the suitable mass of PANI coating can increase the reversibility of the electrode. SEM combined with EDAX tests of the electrodes after cycles show that the sulfur species are trapped by the PANI nanowires. These results demonstrate that the PANI covering layer plays a barrier to restrain the dissolution of the polysulfides, and provide spaces as well as conductive media for sulfur species.
Keywords: Li–S battery; Cathode design; Surface modification; Polyaniline;

We report on the dynamic range and sensitivity simulations of a functional field emission-based pressure sensor. The device comprises a titanium nitride membrane acting as the anode in front of a flat boron nitride cold cathode emitter. We previously reported the problem of non-linearity of these sensors and studied their performance for different membrane geometries and membranes using different materials such as Si, Ti, Ta, and TiN [N. Badi et al., Appl. Surf. Sci. 256 (2010) 4990–4994]. Of the materials investigated, TiN seems to have the most desirable characteristics with respect to linearity. In this paper we report on the effects of membrane dimensions on the sensor operation. Results show how a sensor having a TiN membrane of standard dimension can be tuned during operation to have maximum dynamic range without affecting the sensitivity. The membrane dimensions have a strong effect on the device dynamic range. Small portions of the entire range could however be selected by changing the device operating voltage. We also have shown that smaller area membranes result in devices with better response in terms of constant sensitivity, as compared to those with thicker membranes. The device can be operated over its entire dynamic range by tuning the operating voltage of the device to keep the sensitivity a constant.
Keywords: Electron field emission; Boron nitride; Pressure sensor; Dynamic range and sensitivity; COMSOL multiphysics;

CdS quantum dot (QD)-decorated Cd x Zn1−x S cluster has been successfully synthesized by co-precipitation followed with hydrothermal method, which takes advantage of the photogenerated electrons from CdS QDs. Photocatalytic degradation of rhodamine.B (Rh.B) in the aqueous suspension has been employed to evaluate the visible induced photocatalytic activity of the CdS/Cd x Zn1−x S clusters. Quantum-sized CdS and Cd x Zn1−x S clusters alter the energy levels of the conduction and valence band edges in the coupled systems, which favor the interparticle electron transfer. In addition, CdS/Cd x Zn1−x S is believed to act in a cooperative manner by increasing the degree of charge carrier separation, hence improving the incident photon-to-electron conversion efficiency (IPCE) as well as the photocatalytic activity.
Keywords: CdS/Cd x Zn1−x S cluster; Photocatalytic activity; IPCE; Charge transfer;

Influence of gas and treatment time on the surface modification of EPDM rubber treated at afterglow microwave plasmas by J.V. da Maia; F.P. Pereira; J.C.N. Dutra; S.A.C. Mello; E.A.O. Becerra; M. Massi; A.S. da Silva Sobrinho (918-926).
The ethylene propylene diene monomer (EPDM) rubber possesses excellent physical/chemical bulk properties, is cost-effective, and has been used in the mechanical and aerospace industry. However, it has an inert surface and needs a surface treatment in order to improve its adhesion properties. Plasma modification is the most accepted technique for surface modification of polymers without affecting the properties of the bulk. In this study, an afterglow microwave plasma reactor was used to generate the plasma species responsible for the EPDM surface modification. The plasma modified surfaces were analyzed by means of contact angle measurement, adhesion tests, attenuated total reflection-infrared spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. Two experimental variables were analyzed: type of the plasma gases and exposure time were considered. The predominant failure mode was adhesive, for long treatment times a mixture of adhesive and cohesive failure can be observed and the best conditions tested there was an increase of the rupture strength of about 27%, that can be associated mainly with the creation of oxygen containing functional groups on the rubber surface (C―O, C―O―C and C=O) identified by spectroscopic methods. The predominant failure mode was adhesive, for long treatment times a mixture of adhesive and cohesive failure can be observed. In various conditions tested the contact angles easily decreased more than 500%. What can be concluded that high wettability is a necessary condition to obtain good adhesion, but this is not a sufficient condition.
Keywords: Adhesion improvement; Afterglow plasmas processes; EPDM rubber; Microwave plasma; Surface modification;

CO oxidation reaction mechanisms and energetics are examined on adsorbed Pd4 and Rh4 clusters and adsorbed Pd and Rh atoms on CeO2 and Ce0.75Zr0.25O2 support structures using DFT methods. Activation barriers and TS structures are computed with CI-NEB method. On cluster adsorbed systems, Zr affects CO binding position and O2 adsorption mode. Energetically, formation of two CO2 molecules without barrier and surface regeneration is possible only on Pd4-CeO2 surface. With metal atom substituted surfaces, Pd substituted Ce0.75Zr0.25O2 and CeO2 supports are found to be capable of completing catalytic cycle with consecutive CO oxidations by creating and filling surface oxygen vacancies.
Keywords: CO oxidation; Density functional theory; Three way catalysts; Ceria; Noble metals;

In this study, reduced graphene oxide (RGO) layer is prepared on a self-assembled monolayer (SAM) of 3-aminopropyltriethoxysilane (APTES) modified surface of deposited Ti substrates or Ti–29Nb–13Ta–4.6Zr (TNTZ) alloy substrate. The surface morphology was measured by SEM and AFM. Tribological behaviors in nano scale by AFM and in micro scale by UMT-2 were investigated and compared with titanium substrate, APTES SAM and GO-APTES nanolayer. XPS, water contact angle (WCA) and ellipsometry tests were carried out as assistant methods to discuss the tribological mechanisms. In both nano and micro scale tribological tests, the prepared film holds remarkable tribological properties. It also shows good anti-wear performance in our designed bio-tribological test. Nano and micro tribological mechanisms of the film are discussed.
Keywords: Self-assembled monolayer; Graphene oxide; Reduced graphene oxide; Titanium; Nano/micro tribology;

The mixed acid of H2SO4/HNO3-pretreated multi-walled carbon nanotubes was employed as supports and ultrasound-assisted co-precipitation method was designed to prepare multi-walled carbon nanotubes supported CuO–ZnO–Al2O3/HZSM-5 catalyst. The catalyst was characterized by means of X-ray diffraction spectrum (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), thermal analysis (TG) and Brunauer–Emmett–Teller (BET). The catalyst activity for the preparation of dimethyl ether from hydrogenation of CO2 was investigated in a fixed-bed reactor, which showed that multi-walled carbon nanotubes could promote the catalyst activity of CuO–ZnO–Al2O3/HZSM-5. Under the reaction conditions of temperature at 262 °C, pressure at 3.0 MPa, H2/CO2  = 3 (volume ratio) and space velocity (SV) = 1800 mL gcat −1  h−1, the conversion per pass of carbon dioxide was 46.2%, with the dimethyl ether yield and selectivity of 20.9% and 45.2%.
Keywords: Multi-walled carbon nanotubes; Catalyst promoter; Carbon dioxide hydrogenation; Dimethyl ether;