bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of Axi-Symmetrical Forging Process by “Inverse Approach”
Authors: Halouani Ali , Li Yu Ming , Abbès Boussad , Guo Y.Q.
Published: February 2011

The simplified method called Inverse Approach (I.A.) has been developed by Batoz, Guo et al.[1] for the sheet forming modelling. They are less accurate but much faster than classical incremental approaches. The main aim of the present work is to study the feasibility of the I.A. for the axi-symmetric forging process modelling. In contrast to the classical incremental methods, the I.A. exploits the known shape of the final part and executes the calculation from the final part to the initial billet. Two assumptions are used in this study: the assumption of proportional loading for cold forging gives an integrated constitutive law without considering the strain path and the viscoplasticity, the assumption of contact between the part and tools allows to replace the tool actions by nodal forces without contact treatment. The comparison with Abaqus shows that the I.A. can obtain a good strain distribution and it will be a good tool for the preliminary preform design.
Effects of Impurities Distribution on the Crystal Structure and Electrical Properties of Multi-Crystalline Silicon Ingots
Authors: Xing Qi Zhi , Dong Wei , Shi Shu Ang , Li Guo Bin , Tan Yi
Published: February 2011

Multi-crystalline silicon ingots were prepared by directional solidification using vacuum induction melting furnace. The content of aluminum and iron deeply decreased in the columnar crystal region of the multi-crystalline silicon ingots. The columnar crystal growth broke off corresponded to the iron contents sharply increased. The height of columnar crystal in the silicon ingots related to the pulling rates had been clarified by the constitutional supercooling theory. The maximum of the resistivity and the minority carrier lifetime closed to the transition zone where the conductive type changed from p-type to n-type in silicon ingots. Further analysis suggested that the electrical properties were related to the contents of shallow level impurities aluminum, boron and phosphorus.
Orthogonal Experimental Study on Preparation Conditions of V2O5/TiO2 Catalysts for the SCR of NO with NH3
Authors: Ren Bing Nan , Yang Qiao Wen , Lu Li Na
Published: February 2011

The optimal preparation condition of V2O5/TiO2 catalyst was investigated by the orthogonal experimental method. Five factors were chosen including A(molar ratio of NH4VO3 to oxalic acid),B(aging time of solution),C(active component content),D(impregnation temperature) and E(impregnation time). Every factor had four levels. The levels of A were1:2, 1:1, 3:2 and 2:1. The levels of B were 12h, 14h, 16h and 18h. The levels of C were 2%, 4%, 6% and 8%. The levels of D were 45°C, 55°C, 65°C, 75°C. The levels of E were 2h, 3h, 4h and 5h.The orthogonal experiment table was L16(45). Then the de-NOx rate of V2O5/TiO2 catalysts was tested in SCR catalytic reactor. The results showed that the influence of chosen factors decreased in the following order: C> B> E> D> A. The optimal plan of preparation experiments, obtained from the orthogonal experiment, is C3B1E3D3A4. So the optimal condition of preparation experiments are that active component content is 6%，aging time of solution is 12h，impregnation time is 4h，impregnation temperature is 65°C，molar ratio of ammonium metavanadate and oxalic acid is 2:1.
Enhanced Photocatalytic Activity of BiVO4 for Water Oxidation by Mo Doping
Authors: Yao Wei Feng , Ye Jin Hua
Published: February 2011

Photocatalytic activity of BiVO4 for the water oxidation was found extensively improved by Mo doping. The highest activity of Mo doped BiVO4 for O2 evolution appeared when the photocatalysts was doped by 0.2 at % Mo. The XRD patterens showed that the crystal structure of the photocatalyst was changed by Mo doping. The color and UV-Vis absorption spectra of the photocatalysts were also changed before and after the catalysts were doped by Mo.
Synthesis and Characterization of Mesoporous Silicon Spheres from Solid Silica Spheres
Authors: Zhu Jiang , Meng Chang Gong
Published: February 2011

A well known method was used to convert the solid silica spheres to porous silicon spheres with high surface area, with the starting shape retained. The presented work demonstrated that the porous silicon spheres are composed of polycrystal morphology. Due to the quantum confinement effect, the photoluminescence emission centered at 621 nm. The results of N2 adsorption and desorption analysis indicates the mesoporous silicon spheres possess a surface area around 88 m2 g-1 and single point micro-pore volume 0.173 cm3 g-1.
Direction-Independent Band Gaps Extension Based on Thue-Morse Photonic Heterostructures Containing Negative-Index Materials
Authors: Hong Ou Yang , Deng Xin Hua
Published: February 2011

The band structure and photonic spectrum of one dimensional Thue-Morse quasicrystal composed by negative-index materials and positive-index materials are studied. We show that a new type of the omnidirectional reflection band (ORB) exists in Thue-Morse photonic heterostructures. Compared to a single Thue-Morse quasicrystal, the frequency range of the ORB in a Thue-Morse photonic heterostructure can be notably enlarged, and the width and location of the ORB do not change with Thue-Morse order. The lower edge of the ORB depends only on transverse electric (TE) polarization, while the higher edge of the ORB depends only on transversemagnetic (TM) polarization. These results imply potential applications in improving planar microcavities, optical fibers, and Fabry–Perot resonators, etc.
Flexural Vibration Band Gaps in a Ternary Phononic Crystal Thin Plate
Authors: Yao Zong Jian , Yu Gui Lan , Li Jian Bao
Published: February 2011

The band structures of flexural waves in a ternary locally resonant phononic crystal thin plate are studied using the improved plane wave expansion method. And the thin concrete plate composed of a square array of steel cylinders hemmed around by rubber is considered here. Absolute band gaps of flexural vibration with low frequency are shown. The calculation results show that the band gap width is strongly dependent on the filling fraction, the radius ratio, the mass density and the Young’s modulus contrasts between the core and the coating. So by changing these physical parameters, the required band gap could be obtained.
Resistivity Distribution Characteristics of Metallurgical Silicon Ingot after Directional Solidification
Authors: Shi Shu Ang , Dong Wei , Sun Shi Hai , Tan Yi , Li Guo Bin , Xu Fu Min
Published: February 2011

The distribution of resistivity, impurity and polarity in multicrystalline silicon ingot prepared by directional solidification method was detected. The effect of impurity distribution on resistivity was also researched. The results show that the shapes of equivalence line of resistivity in the cross section and vertical section of the silicon ingot depend on the solid-liquid interface. The resistivity in the vertical section increases with the increasing of solidified height at the beginning of solidification and reaches to maximum at the polarity transition point, then decreases rapidly with the increasing of solidified height and tends to zero on the top of the ingot because of the high impurity concentration. Study proves that the variation of resistivity in the vertical section is mainly relevant to the concentration distribution of the impurities such as Al, B and P in the growth direction.
Electrical Properties of Ag–La0.67Sr0.33MnO3
Authors: Huang Bao Xin
Published: February 2011

A series of La0.67Sr0.33MnO3/Ag composites were synthesized using a sol-gel method followed by a conventional solid-state reaction route. The temperature dependence of the magnetic properties and electrical resistivity has been investigated between 80 and 450 K. Except for the sample with x = 0.01, Ag addition has increased the conductivity of this system dramatically. Curie temperature (TC) is almost independent of Ag content and is 352 K for Ag-dopant samples, while the metal–insulator transition temperature TP increases with Ag addition, which is mainly due to the improvement of grain boundaries and opening a new metal conductivity channel caused by the segregation of Ag on the grain surfaces. At low temperature, the ρ - T curves are fitted well by the expression of ρ= ρ0 + ρ2T2 + ρ4.5T4.5 while all data for the above TC can be fitted by using the adiabatic small-polaron-hopping model ρ = ρ0T exp(E/kBT ).
Preparation of Oil Core/Polyelectrolyte Shell Microcapsules by a Coacervation Method
Authors: Fan Wu Kun , Zhao Wen , Li Zhong Xiao
Published: February 2011

Microcapsules with triallylamine-containing core surrounded by polyelectrolyte shell of controlled thickness were prepared via layer-bylayer assembly technology. First, isocyanate end-capped polyurethane was synthesized through the reaction of isophorone diisocyanate and poly(1,4- butylene adipate). Then, polyurea microcapsules containing triallylamine were prepared by the interfacial polymerization with branched polyethylenimine (PEI) as the water-phase macro-monomer and the prepared isocyanate end-capped polyurethane as the oil-phase macromonomer. Finally, stable weak polyelectrolyte microcapsules were prepared by assembly of poly(acrylic acid)(PAA) and branehed PEI to build up polyelectrolyte multi-layers, and this was followed by glutaraldehyde mediated cross-linking to further increase the mechanical strength of the final capsules. Results showed that the obtained microcapsules were narrowly distributed in size and the mean diameter could be adjusted. This kind of capsule might be used to construct pressure-sensitive materials.
Investigation on Post Treatment of Nano-Size Silver Conductive Film
Authors: Zhao Wen , Li Lu Hai , Xin Zhi Qing , Danzeng Luo Bu
Published: February 2011

To achieve a satisfied conductivity of nano-size silver printed circuit, post deal with nano-size silver conductive film was investigated. Based on the preparation of nano-size conductive ink and conductive circuit, the coated conductive film was treated by series concentrations of hydrochloride solutions, and then scanned by laser beam. The influence of resolutions concentration and dipping time were investigated separately. Atomic force microscopy (AFM), fourier transform infrared (FTIR) and four-probe tester, were applied to characterize the different tested samples. It was found that when the coated silver conductive ink samples were dipped in 20% hydrochloride for 60min, 15°C before laser scanning, the conductivity reaches 0.3Ω/□. It is therefore considered that the “dip in” method provide an efficient alternative to improve the conductivity which from nano-size silver ink.
A Modified Electro-Mechanical Impedance Model for Dynamic Analysis of PZT Sensor Coupled with Beam Structure
Authors: Li Ji Cheng , Wu Di , Lin Li , Li Xi Meng
Published: February 2011

In this paper, the exact solutions of PZT coupled electric impedance and structure mechanical impedance were derived with the investigation of the dynamic interaction between the PZT and the host structure. In the frequency range of 0.1-120 kHz, numerical simulation of the PZT coupled electric impedance was performed using MATLAB code. Experimental investigations were conducted with a PZT excitation and electric impedance measurement system developed by our laboratory in the frequency ranges of 30-55 kHz and 80-100 kHz. The profile and resonant frequencies of predicted and measured impedance frequency spectra were in close agreement and the largest deviation is 0.402%.
An Analysis of Phase Transformations for Porous Shape Memory Alloy Considering Hydrostatic Stress
Authors: Liu Bing Fei , Dui Guan Suo , Zhu Yu Ping
Published: February 2011

According to micromechanics, consider the porous shape memory alloy (SMA) as a composite-sphere model. Isolate a constant thickness spherical shell which is composed of SMA, and is traction free on its inner surface and subjected to the uniform hydrostatic pressure and the deviatoric stress on its external surface. Then, a constitutive model for porous SMA considering hydrostatic stress is proposed by elasticity solution. The stress distribution of the spherical shell was calculated. Corresponding to different applied stresses, the spherical shell is divided into different regions of pure austenite, pure martenite, and austenite/martensite mixture under isothermal circumstances. The martensite volume fraction is then obtained. The predicted results have been compared with the obtained experimental data by Zhao and Sia Nemat-Nasser. It shows that the modeling results are in good agreement with the experiments and the initial phase transition point for porous SMA is lower than the dense SMA.
Dynamic Responses of TiNi Phase Transformation Cylindrical Shell under Radial Impact Load
Authors: Zhang Hui Jie , Tang Zhi Ping , Huang He
Published: February 2011

In this paper, radial impact responses of TiNi phase transformation cylindrical shell were experimentally studied on two-directional constraint. The nominal load-displacement curve was gained by advanced SHPB; meanwhile, the deformation process of the cylindrical shell was recorded by the high speed camera (30000 fps). The effect of stress wave on the whole structure during load process was as follows: the load-displacement curve fluctuated fiercely and rose gradually in the beginning period, whose frequency was basically the same as that of the stress wave propagation in the Striker 2; After that, the load-displacement curve tended to flat, the shell structure became to be ellipse as the compression increases, and the whole unload process slowed down. Finally, the surface strain was obtained by processing the shell deformation image, and the dynamic effect of the material phase transition and phase transition hinge on the cylindrical shell was examined.
Effect of Stress and Magnetic Field on Young’s Modulus of Tb0.3Dy0.7Fe2 <110> Oriented Alloy
Authors: Wang Bo Wen , Huang Wen Mei , Weng Ling , Yi Yu Fa , Hao Yan Ming
Published: February 2011

The <110> grain oriented alloy was grown by zone melting directional solidification technique. The strain-stress curves of Tb0.3Dy0.7Fe2 <110> oriented alloy in different magnetic fields have been measured and the magnetic field dependence of Young’s modulus under different compressive stress has been confirmed. It is found that Young’s modulus gradually decreases with increasing the magnetic fields when the compressive stress is in the range of 15-25 MPa and changes a little in the range of 40-50 MPa. The experimental result indicates that the magnetic field has a marked effect on the Young’s modulus of the Tb0.3Dy0.7Fe2 <110> oriented alloy at a low compressive stress and its change should be considered during the design of magnetostrictive devices.
Elasto-Plastic Earthquake Response Analysis of High-Speed Railway Bridge Fabricated Isolation Bearings
Authors: Chen Ling Kun , Jiang Li Zhong , Liu Peng
Published: February 2011

Basin rubber bearings are frequently used in high-speed railway bridge or passenger special line railway bridge, lead rubber bearings (LRB) are infrequently used in those railway bridges nowdays, the study on earthquake-resistant capability of railway bridge fabricated isolation bearing - the intelligent and functional structure - would be beneficial in engineering practices. Elasto-plastic earthquake responses of high-speed railway bridges fabricated LRB are studied by means of the finite element program, earthquake responses of railway bridges under high-speed vehicles and different earthquake action fabricated and unfabricated isolation bearing are calculated respectively. The results show that: plastic hinge will develop at the bottom of piers in regard to railway bridges with mid-high and low pier; LRB can reduce displacement and inner forces of structures and improve earthquake-resistant capability of structures effectively.
Uniform High Magnetostrictive Properties of Terfenol-D Composites Prepared by a Dry Process
Authors: Dong Xu Feng , Qi Min , Ou Jin Ping , Guan Xin Chun
Published: February 2011

Magnetostrictive composites were usually fabricated using a wet process. The settlement of particles in liquid polymers due to the gravity results in the inhomogeneous and low magnetostrictive properties. To solve the problem, magnetostrictive composites were prepared using a dry process, and their properties were tested in this paper. Measurement of magnetostriction on different positions along the length direction of the material indicates the magnetostrictive composites prepared by the dry process present uniform properties due to the uniform distribution of the active particles in the polymer matrix. The saturation magnetostriction and the maximum dynamic magnetostriction of the [1-3] Terfenol-D composites prepared in the study was 1005ppm and 4.08nm/A, respectively, which was larger than the [0-3] ones.
Effect of Negative Pulse Voltage on the Microstructure and Corrosion Resistance of Microarc Oxidation Film of A356 Aluminum Alloy
Authors: Peng Guang Huai , Han Bao Jun , Fang Ling , Guo Xue Feng , Zhang Xiao Lian
Published: February 2011

The effect of negative pulse voltage on the microstructure and corrosion resistance of microarc oxidation film of A356 aluminum alloy treated by microarc technique was investigated by SEM, coating thickness gauge and electrochemical workstation etc. The results show the negative pulse voltage greatly influences the microstructure and corrosion resistance of microarc oxidation film by its electrode reaction. The film thickness increases while the size of pore and roughness of the film surface decreases initially and then increases with negative pulse voltage increasing. The microarc oxidation treatment considerably improved corrosion resistance, and the highest corrosion potential was -1.16V, which was 0.38V higher than that of substrate, and the corrosion current was lower than that of substrate about three orders of magnitude.
Formation of TiO2/Ti Composite Photocatalyst Film by 2-Step Mechanical Coating Technique
Authors: Lu Yun , Yoshida Hiroyuki , Nakayama Hiroyuki , Hao Liang , Hirohashi Mitsuji
Published: February 2011

In the present work, 2-step mechanical coating technique (2-step MCT), an advanced MCT, was proposed and carried out to form TiO2/Ti composite photocatalyst film with anatase TiO2. The microstructures and photocatalytic activity of the composite film were investigated. The results show that the proposed 2-step MCT is a simple process for forming TiO2/Ti composite film. The composite film has a microstructure with a nonuniform thickness, like random distribution islands. The TiO2/Ti composite film has high photocatalytic activity, which is related with crystallinity and volume of the TiO2 in the composite film.
Analysis on the Mechanical and Electrical Properties of PI/MWNTs Nano-Hybrid Films
Authors: Zhang Ming Yan , Diao Peng He , Zhu Xiao Ying
Published: February 2011

In this paper, MWNTs (multi-walled carbon nanotubes) were modified by the mixture acid of H2SO4 and HNO3, the PI (polyimide)/MWNTs nano-hybrid films were prepared by means of ultrasonic vibration and in-situ polymerization. The surface morphology was characterized by SEM, the chemical structure was characterized by FT-IR. The tensile strength and Young’s modulus increased at first and then decreased with the increase of MWNTs content. The dielectric constant was tested at a frequency of 1 kHz. The dielectric constant had no obvious variation when MWNTs content was less than 2.9 wt%, as the MWNTs content exceeded 5.36 wt%, the dielectric constant increased rapidly. In general, the dielectric loss of PI/MWNTs nano-hybrid films was higher than the dielectric loss of pure polyimide films. The dielectric loss increased slowly in low frequency region but rapidly in high frequency region. All the test results were attributed to the dispersion degree of MWNTs doping and the combination degree between PI matrix and modified MWNTs in PI/MWNTs nano-hybrid films.
Highly Textured (111) Pt Substrates for Preferred Orientation Controlled AlN Films
Authors: Harumoto Takashi , Muraishi Shinji , Shi Ji , Nakamura Yoshio
Published: February 2011

Preferred orientation of AlN films has been improved to c-axis using a highly (111) textured Pt layer. The highly textured (111) Pt layer is obtained by inserting an AlN layer between the Pt layer and substrate. Thus, Pt/AlN/substrate could be termed a substrate for preferred orientation controlled AlN films. X-ray diffraction (XRD) profiles reveal that the degree of preferred orientation of such highly (111) textured Pt layer surpasses the one originated from the crystal structure of Pt. The (2θ, ψ) intensify maps of diffracted X-ray collected as a function of the diffraction angle (2θ) and the tilting angle (ψ) exhibit that the films are perfectly (111) preferred orientated, however, they do not show in-plane texture. The (2θ, ψ) maps also demonstrate that a residual stress in films is subject to compressive.
Antiferromagnetic Layer Thickness Dependence of Exchange Bias in Sputter-Deposited Co/CoO/Co Trilayer
Authors: Wang Jian , Muraishi Shinji , Shi Ji , Nakamura Yoshio
Published: February 2011

We have used ferromagnet/antiferromagnet/ferromagnet sandwich structure to probe the antiferromagnetic layer thickness dependence of exchange bias in sputter-deposited Co/CoO/Co trilayer. The exchange coupling occurring at the upper ferromagnetic/antiferromagnetic interface is always found to be stronger than the one at the lower antiferromagnetic/ferromagnetic interface. The grain growth with increasing antiferromagnetic layer thickness can lead to a gradient of grain size distribution through the whole antiferromagnetic layer. Consequently, the relatively large grains at the upper interface would results in a rougher interface which we treat as structural defects and can significantly enhance exchange bias through domain state model. The slightly decrease of exchange coupling with increasing antiferromgnetic layer thickness indicates that the exchange bias is only governed by the grains that are thermally stable but whose anisotropy energy is low enough to be set.
Research on Corrosion-Resistance of High Velocity Arc Spray Coatings on Surface of Steel Structure in Splash Zone Environment
Authors: Wei Shi Cheng , Xu Bin Shi , Liang Xiu Bing , Wang Yu Jiang , Liu Yi
Published: February 2011

The most severe corrosion of offshore steel structure occurs in splash zone. There are many factors affecting the steel structure corrosion in the splash zone, such as corrosion problems caused by seawater and effect of impacted brought by the ocean wave. Considering the corrosion characteristics in splash zone and the corrosion invalidity behaviors of offshore steel structure, the Zn-15Al, Al-RE, Zn-Al-Mg-RE and FeBSiNb uncrystal coatings were prepared by automatic high velocity arc spraying. The different anti-corrosion behaviors of the four coatings were studied through the corrosion comparative tests and the microstructures analyzed of the coatings before and after the corrosion tests. The anti-corrosion coating systems suitable for using on surface of steel structure corrosion in the splash zone were found, which provided technique guarantee for extending the using life of offshore steel structures.
Study on Photoluminescence of Porous Silicon with Cu Deposition
Authors: Chen Xiu Hua , Ma Wen Hui , Ma Ting Ting , Wu Xing Hui
Published: February 2011

Detailed studies on Photoluminescence (PL) of porous silicon (PS) with copper deposition were presented. PS was prepared via double electrobath, and then copper was deposited on PS surface by chemical plating. Atomic force microscopy (AFM) measurement indicates that there are different surface morphologies of PS samples with hemispherical, mountain, and tubes-like shape in different etching conditions. PL results show that the PL spectrum intensity of PS with Cu post-deposition increases 50% and do not decay after being laid 4 months than that of PS with pre-deposition. And the peak position from the PL spectrum with Cu deposition has a 14nm blue shift due to the surface stress effect of Cu to PS.
Microstructure and Corrosion Resistance of TiN Coating on HSS by Pulsed Bias Cathodic Arc Ion Plating
Authors: Yao Xiao Hong , Tang Bin , Tian Lin Hai , Li Xiao Fang , Ma Yong
Published: February 2011

TiN coating with thickness of 2.5μm was deposited on high-speed steel (HSS) substrate by pulsed bias cathodic arc ion plating. The surface and cross-section morphologies, composition depth profile and phase structure were characterized by FESEM, GDOES and XRD, respectively. Scratch test for adhesion evaluation, microhardness test for hardness measurement, and potentiodynamic polarization for corrosion resistance test were used. The results show that the TiN coating exhibits smooth surface, dense columnar grain structure and an obviously preferred orientation of TiN(111). The adhesion of the coating to substrate is exceeded more than 100N. The hardness of the coating is about 26 GPa. The low corrosion current density (Icorr) and rather high corrosion potential (Ecorr) value imply that the TiN coating displays a good corrosion resistance in 0.5mol/l NaCl solution. However, pitting is still existed due to the defects in the coating.
Effect of the Si3N4 Coating on the Mc-Si Ingot in the Process of Multicrystalline Silicon Purification by Metallurgical Methods
Authors: Li Jia Yan , Tan Yi , Liu Mei , Dong Wei
Published: February 2011

The Si3N4 protective coating has an important impact on avoiding melting silicon from contacting with the crucible wall directly. A mixed Si/Si3N4 layer was formed on the interface of silicon and Si3N4 coating, and the declination of N content was observed in this mixed layer. With the ingots condition of 1500oC for 2 h, the large Si3N4 and SiC particles appeared in the mixed layer and the formation mechanism was discussed. The Si3N4 coating had significantly increased the lifetime of minority carriers by decreasing impurity content.
Microstructure and Mechanical Properties of AlN Ceramics Sintered with Yttrium Nitrate
Authors: Zhang Zhi Jun , Xu Fu Min , Tan Yi , Shi Xiao Lei , Dong Wei
Published: February 2011

AlN ceramics were prepared by hot-pressing process with Y(NO3)3·6H2O as a sintering additive. Microstructure and mechanical properties of sintered AlN ceramics were measured and compared with that of monolithic AlN ceramic prepared by the same process. The results showed that the density and mechanical properties of monolithic AlN ceramics were drastically enhanced by adding Y(NO3)3·6H2O. Especially, the AlN ceramic with 3.24 wt% Y(NO3)3·6H2O (2 wt% Y2O3) displayed striking enhancement in mechanical propertie. However, such enhancement did not follow a consistent behavior with the increase of Y(NO3)3·6H2O content. A significant drop present at contents over inflection point (3.24 wt% Y(NO3)3·6H2O).
Influence of La2O3 on the Electrical Properties of Dense SnO2 Electrodes
Authors: Wang Qing Wei , Wang Hong Zhi , Ning Wei
Published: February 2011

We prepared La2O3 doped SnO2 powder by a co-deposition method and used the doped material to manufacture tin dioxide electrodes by traditional ceramics methods.. The results showed that La2O3 led to an obvious decrease in electrical resistivity at room temperature but it had little influence at temperatures higher than 600 °C. The samples were characterized by X-ray diffraction and section scanning electron microscopy. We found that La2O3 increased the rate of tin dioxide crystal growth. At La2O3 concentrations as high as 1 wt%, a new La2Sn2O7 phase was present and this phase plays an important role in improving the electrical properties of the La2O3-doped SnO2.
Oxidation Kinetic and Diffusion Mechanism Study of a Zr-Based Bulk Metallic Glass Alloy
Authors: Wang Bin , Huang Dong Ya , Chen Zhe , Prud’homme Nathalie , Ji Vincent
Published: February 2011

Oxidation kinetic of a Zr55Cu30Al10Ni5 bulk metallic glass (BMG) and its crystalline counterpart were studied under dry artificial air (20% of O2 and 80% of N2) at 673 K by thermogravimetry analysis (TGA) method. According to TGA profiles, the oxidation kinetic in both amorphous and crystalline states followed a protective parabolic law. However, the oxidation rates for the amorphous alloy were obviously higher than those for the crystalline alloy. Pseudo-grazing incident X-Ray diffraction (GIXRD) has been carried out to identify the oxides nature and their crystalline structure. Tetragonal-ZrO2 dominated the oxide scale formed on both alloys (BMG and crystalline) at T = 673 K; meanwhile, a slight amount of Cu was detected on the oxide surface of studied BMG alloy. The atomic diffusion mechanism was investigated using a two-stage oxidation treatment to study oxide scale growth kinetics. The studied specimens were oxidized firstly under dry artificial air and then under 18O2 isotopic tracer gas for 1.5 hours respectively at 673 K. The evident solute penetration zone and ion diffusion characteristic through the oxide scale were determined by Cs+ secondary ion mass spectrometry (SIMS) depth profile. The results showed the mechanism of the oxide layer formation of both alloys was not only due to Oxygen ions diffusion from oxide surface to interior scale, but also to an outward diffusion of Zirconium ions from substrate to oxide layer and the ZrO2 oxide growth seemed to occur at the oxide/gas interface in our studied case.
Initial Oxidation Behavior of Zr55Cu30Al10Ni5 Bulk Metallic Glass in Short-Term Stage
Authors: Huang Dong Ya , Wang Bin , Ji Vincent , Zhang Tao
Published: February 2011

The isothermal initial oxidation kinetics of Zr55Cu30Al10Ni5 bulk metallic glass in glassy state (lower than Tg = 685K) and in surpercooled liquid state (Tg = 685 K < T < Tx=774 K) is investigated under dry air by thermogravimetric method in short-term stage (for 1.5 hours). A protective parabolic law is followed in glassy state, except at 573 K where a linear law is followed. The self-limiting oxidation kinetics evolves from a short linear stage to a steady mild growth stage in supercooled liquid state at 723 K, which is induced mainly by crystallization and by the fast growth of dense scale. The growth of the scale is dominated by the formation of tetragonal-ZrO2 (t- ZrO2) in the range of 623 K - 673 K in glassy state for 1.5 hours. The activation energy of oxidation is mainly piloted by the diffusion of oxygen ions.
A New Synthetic Route to Nano Metal Oxides
Authors: Zhao Hong , Yao Jin Hua , Jin Shu Bao , Liang Li Jun
Published: February 2011

Strong alkali anion exchange resin was employed as a hydroxyl source in the synthesis. OH- releasing rates were easily controlled by varying precursor salts, salt concentrations and temperatures, etc. The ratio between the nucleation speed and the speed of oxide crystallite growth was adjusted to favor the anisotropic growth of the crystal. Zinc and aluminum nano-sized oxide were obtained in various morphologies. X-ray diffraction (XRD), scanning electron microscope (SEM) and Energy Dispersion Spectroscopy (EDS) were employed to characterize the products. It is ascertained that the surface reaction on the resin and the mechanical grinding are the key steps in controlling the product morphology. The results show the flexibility and possibility of large scale production of various nano metal oxides and as well as mixed oxides.
The Effect of Strain Rate on the Plastic Deformation Mode of CP-Ti during Surface Nanocrystallization
Authors: Chen Chun Huan , Jin Cheng , Ren Rui Ming
Published: February 2011

The effect of the strain rate on the surface nanocrystallization of titanium is investigated both theoretically and experimentally in this paper. The strain rate variation and stress distribution from surface to the interior of titanium during shot peening are estimated firstly using finite element method. Then shot peening experiment is carried out on a commercially pure titanium (CP-Ti) plate, and the obtained surface microstructures is characterized by transmission electron microscopy (TEM). Combining theoretical simulations and experimental observations, the effect of strain rate on the strain accommodation mechanism and plastic deformation mode are discussed. It is concluded that the strain rate and stress achieve the highest at the top surface layer of CP-Ti, and the strain rate decrease dramatically from the surface to the interior. The strain rate at the top surface layer is up to 104 s-1, which leads to superplastic deformation of Ti. There is no mechanical twin in the surface layer, instead, deformation lamella and adiabatic shear bands are the dominating microstructures. By means of rotation recrystallization, those deformation bands evolve to nanocrystallines.
Study on Nanometer Size Structures in the Cr-Mo Electroplated Layer Using Transmission Electron Microscopy and Positron Lifetime Measurement
Authors: Tanita Yoshio , Matsui Daiji , Fukushima Hiroshi
Published: February 2011

Micro- and nano-structures of the Cr-Mo electroplated layers were studied mainly by Transmission Electron Microscopy (TEM), High Resolution TEM (HRTEM) and Positron Annihilation Lifetime Spectroscopy (PALS). These electroplated layers which were deposited in Cr-Mo electrolyte containing an organic sulfonic acid, showed surface structures having severe ups and downs of small crystal grains. Both selected area diffraction and dark-field image of TEM confirmed the presence of very small crystal grains of less than 50 nm. These small crystal grains exhibited textured structure when the electrolyte contained an organic sulfonic catalyst. PALS results indicated the presence of high density nano-size voids, and HRTEM analysis confirmed the presence of high density voids of 1 nm to 2 nm in diameter. Size and density of these nano-voids increased with the amount of catalyst in the electrolyte.
Investigation on the Removal of B Impurity in Metallurgical Grade Si by Electron Beam Melting
Authors: Jiang Da Chuan , Dong Wei , Tan Yi , Wang Qiang , Peng Xu , Li Guo Bin
Published: February 2011

The growth in the solar energy technology caused inshortage solar grade Si. As a lowcost, environmental friendly technology, metallurgical method purity silicon is developed significantly. However, as a typical impurity in Si, B is difficult to be removed by directional refining or vacuum melting due to its large segregation coefficient and less evaporation coefficient. In this paper, the big difference of evaporation pressure between Si and B can be applied to separate B from Si, in which, B is remained in molten Si, while most of Si becomes evaporant. Electron beam is applied to scan molten Si and the Si existed in the form of the evaporant is gather on the watercooled crystallizer. The content B in the evaporant is undetectable by ICP-MS.
How Crystals Form from a Cloud of Atoms
Authors: Häussler Peter , Stiehler Martin
Published: February 2011

Structure formation, the condensation of a cloud of atoms to a crystal is still not well understood. Disordered sytems (amorphous/liquid) should be in the center of this research, they are the precursors of any crystal. We consider elementary systems, as well as binary, or ternary amorphous alloys, irrespective whether they are metallically, covalently or ionically bonded and describe the process of structure formation in the formal language of thermodynamics but, as far as we know for the first time, by an extended version (general dynamics), based on the complete Gibbs fundamental equation, applied to internal subsystems. Major structural features evolve from global resonances between formerly independent internal subsystems by exchanging momenta and angular momenta, both accompanied by energy. By this they adjust mutually their internal features and create spherical-periodic structural order at medium-range distances. Under the given external constraints the resonances get optimized by selforganization. Global resonances of the type considered have clearly to be distinguished from local resonances between individual ions (described by quantum chemistry) forming local order. The global resonances cause anti-bonding (non-equilibrium) as well as bonding (equilibrium) states of the coupled total system, occupying the latter to form new structurally extended order. The transition to equilibrium creates entropy which itself leaves the system together with energy. At resonance the energetical splitting between the bonding and anti-bonding state is largest, the creation of entropy and the decrease of the total energy therefore, too. The crystal, finally, evolves by additionally optimizing a resonance based on angular momentum, and the additional adjustments of the local resonances to the global ones, theoretically done by applying Bloch’s theorem.
Preparation and Characteristics of MnAlC Nanoparticles by Plasma Arc-Discharge
Authors: Li Pu , Lee Jung Goo , Dong Xing Long , Choi Chul Jin
Published: February 2011

MnAlC nanoparticles were synthesized by plasma arc-discharge method. Heat treatment of these nanoparticles at temperature from 400 to 600 °C resulted in the formation of the ferromagnetic τ-phase. Most of the nanoparticles had nearly spherical shape, smooth surface and core/shell structure. The shells of the nanoparticles mainly consisted of Al2O3 and a small amount of Mn oxides. Though the saturation magnetization of MnAlC nanoparticles was lower than that of bulk samples due to the effect of nonmagnetic phases (β, γ2 and Mn3AlC) and the oxide shell, the highest coercivity, up to 5.6 kOe in the MnAlC magnets, was achieved when annealed at 500 °C for 30 min.
The Comparison between the Borate Glass Ceramic Porous Scaffolds Preparing by the Sintering and Binding Method
Authors: Tu Yi Fan , Piao Long Hua , Liu Qing Yan , Liang Wen
Published: February 2011

A β-NaCaPO4 containing borate glass ceramic is prepared. Two kinds of porous scaffolds are constructed by sintering glass particles in the size of 300~400μm and binding glass particles in the size of 200~300μm using 5 wt% sodium silicate solution respectively. The reaction of the scaffolds in the SBF solution, the bioactivity and biodegradation of the scaffolds are characterized by weight loss analysis, XRD, and SEM. The same is done to the 45S5 scaffolds as comparison. The results show that the borate glass ceramic scaffolds have better biodegradation and bioactivity. The final weight loss of the sintering scaffolds and the binding scaffolds are 50.71% and 70.68% respectively, which indicates that the high temperature during the course of the sintering has great influence on the bioactivity of the borate glass ceramic scaffolds. The XRD indicates that the hydroxylapatite has formed on the both kinds of the scaffolds, and the hydroxylapatite on the binding scaffolds has higher degree of crystallinity. The residual glass phase of the glass ceramics contributes to a quick apatite formation on the scaffolds due to its high solubility in SBF solution, while the β-NaCaPO4 crystal phase leads to a slower apatite formation which guarantees an improved mechanical stability of the scaffold. This combined reaction mechanism enables the biodegradation rate of the scaffolds to match with the growth rate of tissues, which makes the scaffolds a good potential prospect in the field of tissue engineering.
Determination of Holocellulose and Alpha-Cellulose Contents in Triploid Clones of Populus tomentosa Using NIRS
Authors: Yao Sheng , Xing Mian , Jiang Yi Fei , Wu Guo Feng , Pu Jun Wen
Published: February 2011

The aim of this work was to study the ability of NIR spectroscopy to determine holocellulose and alpha-cellulose contents in triploid clones of Populus tomentosa. For this purpose 90 trees with five families in different planting density grown in Shandong were analyzed. Calibration models were developed from wet chemical and NIR data using partial least squares (PLS) regression. High coefficients of determination (R2) and low root mean square errors of cross-validation (RMSECV) were obtained for holocellulose (R2 = 0.7805, RMSECV =0.652) and alpha-cellulose (R2 = 0.8702, RMSECV = 0.548) from wood meal. Prediction produced high correlation coefficients between laboratory and predicted values for holocellulose and alpha-cellulose contents, which R2 values are 0.7467 and 0.8505, and RMSEP are 0.993 and 0.553, respectively. This study showed that NIR analysis can be reliably used to predict holocellulose and alpha-cellulose contents in triploid clones of Populus tomentosa.
Formation of Porous (Ca, P)-Doped TiO2/Dense Ti Double Coatings on NiTi Alloy
Authors: Zhao Hong , Tian Cui Cui , Lin Guo Qiang , Ge Zhen Dong , Qi Min , Yang Da Zhi
Published: February 2011

NiTi alloys are widely used for bone implants due to their good mechanical properties. However, they can suffer certain disadvantages, such as leaching of toxic nickel ions and poor osteoinductive properties. A porous (Ca, P)-doped TiO2 /dense Ti double coatings on NiTi alloy with porous (Ca, P)-doped TiO2 coating as the top layer and a dense Ti coating as the interlayer should possess a very good combination of bioactivity and chemical stability. In this paper, the double coatings were formed by applying a duplex process of arc ion plating (AIP) and micro-arc oxidation (MAO). X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) have been used to investigate the microstructure and morphology of the coatings.
Compatibility and Accelerated Degradation of L-Tyrosine Derived Biodegradable Polycarbonate/PEG Blends
Authors: Huang Xia , Chen Jia Chang , Shen Chang Yu , Li Qian , Liu Chun Tai , Zhang Shi Xun
Published: February 2011

In the present study, the compatibility and degradability of L-tyrosine derived polycarbonate(PC)/Poly(ethylene glycol) blend were investigated. The PC was synthesized in our laboratory. Blends of the polymers with compositions 95/5, 85/15, 75/25,50/50 and 25/75 w/w were prepared by solution-casting. The blends were characterized by FT-IR,DSC,XRD,SEM. No obvious two phases were observed. Analysis of water absorption revealed that the combination of PC and PEG improved the hydrophilicity of PC. DSC and SEM analysis implied that all those components in consideration were compatible well in the blend formulation systems.Tg of the blends decreased with increasing PEG content. With the increase of the soft segment PEG content, the water retention ratio increases from 37% to 83%.
Effects of Temperature on the Crystallization of Calcium Carbonate in Egg White Protein Solution System
Authors: Zhu Wen Kun , Luo Xue Gang , Lin Xiao Yan , Zhou Jian , Lu Yan
Published: February 2011

Various crystal forms of calcium carbonate were successfully synthesized with CaCl2 and Na2CO3 in 10%(V/V) egg white protein solution system at 20 °C, 40 °C and 60 °C, respectively. The obtained calcium carbonate were characterized by SEM, XRD, FTIR and TG. In addition, the possible mechanism of crystal formation were analyzed. The results indicated that egg white protein could regulate the crystal forms of calcium carbonate and the calcium carbonate, which contained a small amount of egg white protein and consisted of mixed calcite and aragonite, was mainly spherical. With the temperature rosing, the vaterite content gradually increased while the calcite decreased.
TiOx Film Formation on NiTi Alloy (100) Surface: Density Functional Theory Investigation
Authors: Liu Xin , Guo Hui Min , Meng Chang Gong
Published: February 2011

NiTi shape memory alloy is widely used as biomaterial for its superior mechanical properties and good biocompatibility. Effective protocols based on the surface oxidation mechanisms, which would precisely control the formation of surface oxide, should be designed and implemented to improve the biocompatibility of NiTi alloy based biomaterials. To shed light on the TiOx species formation mechanism on NiTi surface, density functional theory (DFT) based calculations were carried out to study the adsorption and reactions of O2 on the NiTi alloy (100) surface. O2 is found activated and will decompose upon adsorption. At higher O2 coverage, the reconstructed bridge configuration will generate (110) surface of TiO2, and the hollow configuration will evolve to (100) surface of TiO. The formation of TiO2 phase is thermodynamically favored, but only feasible when the temperature is enough high. At lower temperature, the atomic diffusion is slowed down, and the surface reconstruction will be limited. This explains why TiO2 will be dominant TiOx at higher temperature, and TiO will exist at lower temperature. Our current work provides more insights on the initial oxidation of NiTi surface, and these findings would be beneficial to improve NiTi alloy based biomaterials, and might guide the design of new functional materials.
Structure Characteristics of the Hemifusus tuba Conch Shell
Authors: Liang Yan , Zhao Jie , Wu Cheng Wei , Mu Chen Xiao
Published: February 2011

The mollusk shell mobilizes calcium from environment for skeletal mineralization. This occurs through synthesizing solids in solution in the presence of organic molecules of specific interior regions of the conch shell. The ultrastructure of the Hemifusus tuba conch shell living in the Huang/Bo sea area is investigated in the paper. It is shown that the composition and microstructure of the mollusk shell vary in different positions. The prodissoconch shell consists only of aragonite with the crossed-lamellar microstructure. While the spiral shell and the body shell of the Hemifusus tuba conch shell are composed of one calcite layer and several aragonite layers. The calcite layer consists of cylindrical grains, but the aragonite layers are crossed-lamellar ultrastructure. The margin of shell aperture is only composed of calcite with cylindrical grains. This natural optimization of the shell microstructure is intimately due to the growth of the organic matrix. The process of growth allows a constant renewal of the material, thus enabling the functional adaptation of the shells.
Structure and CO Gas Sensing Properties of PPy/LaFeO3 Nanocomposites
Authors: Song Peng , Wang Qi
Published: February 2011

In this paper, perovskite LaFeO3 nanoparticles were synthesised by a sol-gel method. Then, polypyrrole (PPy)/LaFeO3 nanocomposites were prepared by a simple in situ chemical polymerization method. By means of X-ray diffraction (XRD), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM), the microstructure of PPy/LaFeO3 nanocomposites was characterized. The XRD patterns indicated that LaFeO3 nanoparticles have a perovskite phase with orthorhombic structure, and incorporation of PPy did not change the crystalline structure of LaFeO3. The PPy was evenly dispersed on the surface of LaFeO3 particles, which was endorsed by FTIR spectral analyses. And SEM images indicate that the PPy was evenly dispersed on the surface of LaFeO3 particles without apparent agglomeration. And we found that the nanocomposites exhibited a higher response to CO gas.
Relationship between Mechanical Properties of Modified Cementitious Composites and Properties of Polymer Films
Authors: Li Jin Mei , Bao Wang , Ni Kun , Zhong Shi Yun
Published: February 2011

Keep the mixing amount of styrene-acrylic ester (SAE) constant, the mixtures of SAE and cellulose ethers (CE) were confected with tap water and filtered cement water respectively. The relationship between the mechanical properties of polymer modified cementitious composites (PMCCs) and the properties of polymer films was studied. It is discovered that when the cellulose ether-latex ratio (CE/L) increases, the polymer films become fragile. The properties of polymer films mutate when CE/L increases from 0.5‰ to 1.0‰. The tensile strength of the polymer films with filtered cement water is higher than that with tap water. However, the elongation at break is lower than that with tap water. The compressive strength of PMCCs decreases with the increase of the tensile strength of polymer films. Yet, the flexural strength of PMCCs does not relate to the properties of polymer films. The adhesive strength increases when CE/L increases from 0 to 1.0‰, but no longer after that.