Materials Science Forum Vols. 610-613

Abstract: The GaN film deposited on ITO glass substrate by PECVD was characterized using XPS, SEM and reflectance spectra. XPS analysis indicated that the chemical status of the film surface was predominated in mixture phase of GaN and Ga2O3. It was observed that Tthe film annealed at 400°C exhibited platelet-shaped and hexagonal structure and c-plane textured morphology from SEM images. The reflectance spectra show that the absorption cutoff wavelength of the sample annealed at 400 °C was broadened to 1100nm roughly. From the results, Iit is concluded that the GaN film grown on ITO glass substrate by PECVD will be a promising full spectra material.

Abstract: The fracture problems of ecomaterial (aluminum alloyed cast iron) under extra-low cycle rotating bending fatigue loading were studied using artificial neural networks (ANN) in this paper. The training data were used in the formation of training set of ANN. The ANN model exhibited excellent in results comparison with the experimental results. It was concluded that predicted fracture design parameters by the trained neural network model seem more reasonable compared to approximate methods. It is possible to claim that, ANN is fairly promising prediction technique if properly used. Training ANN model was introduced at first. And then the Training data for the development of the neural network model was obtained from the experiments. The input parameters, notch depth, the presetting deflection and tip radius of the notch, and the output parameters, the cycle times of fracture were used during the network training. The neural network architecture is designed. The ANN model was developed using back propagation architecture with three layers jump connections, where every layer was connected or linked to every previous layer. The number of hidden neurons was determined according to special formula. The performance of system is summarized at last. In order to facilitate the comparisons of predicted values, the error evaluation and mean relative error are obtained. The result show that the training model has good performance, and the experimental data and predicted data from ANN are in good coherence.

Abstract: According to the principle of accumulative roll bonding(ARB),the 20 ply clad sheet from austenitic stainless steel (STS304)/pure aluminum(Al1060)/aluminum alloy(Al3003) …/ austenitic stainless steel (STS304)sheets with excellent heat, anti-corrosion and mechanical properties of stainless steel and the high thermal and electrical conductivities of aluminum was fabricated by accumulative clad rolling (ACR). Well-bonded clad plate was successfully obtained in the procedure: Al1060 sheets with a thickness of 0.5mm and Al3003 sheets 0.5mm thick and STS304 sheets 0.5mm thick were employed. Basic clad sheet from different ply Al1060/Al3003 sheets was obtained with an initial rolling reduction of 44% at 450°C followed by annealing at 300°C, then ACR was with reduction of 50% at 550°C from STS304 on each side. The stretch property, bonding property, microscopic structure and interface composition were measured and analyzed. It was indicated that the best clad sheet had bonding strength of 129MPa and stretch strength of 225MPa. was of 129Mpa bonding strength and 225Mpa stretch strength. At the end,STS304 sheet with thickness of 3mm which being used in superior quality kitchenware and finishing material and so on was taken the place of the clad sheet from STS304 sheets of 1mm and Al1060 of 1mm and Al3003 of 1mm. Therefore, it decreased by 44% in weight and economizes rare metal elements Cr and Ni of 66% in weight.

Abstract: The nano-particle pyrite in nano-particle form was synthesized by the deposition hydrothermal reaction using FeCl3•6H2O, Na2S•9H2O and S as the starting materials. The property of particles was investigated by X-ray diffraction, transmission electron microscope, UV-Vis spectrophotometer. The results indicated that the pure iron pyrite could be achieved in the alkaline condition. Increasing the proportion of S avails to removing marcasite and ferric oxide . Wwhen the amount of FeCl3, Na2S and S is in the ratio of 1:3:1.5, the product is pure pyrite FeS2 powder with a polyhedron shape is obtained and the average particle size isof about 20~40nm, and this result can be easily repeated. Optical analysis indicates that the optic energy band gap is about 1.62 eV. Its open circuit voltage is 456mV, and the corresponding short circuit current is 19 μA.

Abstract: An Ag-Ce-TiO2 composite film was prepared by incorporating Ag in the Ce-TiO2 films with an impregnation method through photoreduction. The bactericidal activity of the Ag-Ce-TiO2 composite film and the effect of deposition of silver and doping cerium in the different irradiations on the antibacterial performance were assessed against Escherichia coli (E. coli). TIhrough characterization of X-ray diffraction (XRD), X-ray photoelectronic spectra (XPS) and UV/VIS diffusive reflectance spectra (DRS), it was found that the Ag-Ce-TiO2 composite film was composed of predominant anatase titania, cerium oxides (in the form of Ce2O3/CeO2) and silver nanoparticles. Moreover, the bactericidal activity of the Ag-Ce-TiO2 composite film and the effect of deposition of silver and doping cerium in the different irradiations on the antibacterial performance were assessed against Escherichia coli (E. coli). The results show that the Ag-Ce-TiO2 composite film has much higher antibacterial efficiency than that of glass and pure TiO2 film either in the room light or in the dark. Therefore, this composite film is promising in applications of antimicrobial and self-clean technologies.

Abstract: Tin and tin-aluminum thin film anodes for lithium ion battery are deposited on a copper substrate by radio frequency (RF)-magnetron sputtering at room temperature. Charge/discharge characteristics are compared. It is indicateds that tin-aluminum anode has higher capacity and better cycle performance than that of pure tin anode. XRD shows that tThe tin-aluminum thin film is a mischcrystal alloy. The first discharge capacities of tin and tin-aluminum are 750mAh/g and 1205mAh/g respectively. After 30 times charge/discharge, the specific capacity of tin-aluminum anode is 780mAh/g. , compared with 530mAh/g for pure tin anode. From above results, tThe mischcrystal alloying tin with aluminum has effectively improved the electrochemical performance of tin anode. The tin-aluminum mischcrystal alloy will be a promising anode material for lithium ion battery.

Abstract: In this work, we have synthesized LaNi5/A and Mg2Ni/A (A = graphite, copper or palladium) nanocomposites. The A elements were distributed on the surface of ball milled alloy particles homogenously and role of these particles is to catalyze the dissociation of molecular hydrogen on the surface of studied alloy. Mechanical coating with graphite or palladium effectively reduced the degradation rate of the studied electrode materials. Results showed a significant broadening of the valence bands of studied nanocomposites compared to those obtained by theoretical band calculations. The reasons responsible for the band broadening of the nanocrystalline LaNi5- and Mg2Ni-type alloys are probably associated with a strong deformation of the nanocrystals in the mechanically alloyed (MA) samples. Normally the interior of the nanocrystal is constrained and the distances between atoms located at the grain boundaries expanded. The valence band spectra of the MA samples could be also broadened due to an additional disorder introduced during formation of the nanocrystalline structure.

Abstract: In this paper, the influences of different binders (Hydroxypropyl Methyl Cellulose (HPMC), Carboxymethyl Cellulose Sodium (CMC), Polytetrafluoroethylene (PTFE) and Styrene- butadiene Rubber (SBR)) on high-rate discharge performances at low temperature for the negative electrode of Ni/MH battery have been studied by orthogonal experimental design. Electrochemical measurements have been conducted to investigate the capacity, charge-discharge performance, cyclic voltammetry and electrochemical impedance characteristics. The surface morphology and chemical compositions have been investigated by SEM and EDS. Based on the range analysis, the primary and secondary influence factors as well as the optimization results were obtained. From the CV characteristic curves, the oxidization peaks and reduction peaks are not clearly shown, which indicates that the redox reaction does not occur clearly after binders added. The EIS experiments show that the deterioration of the voltage characteristic of the battery is due to drying out of the separator that increases the ohmic resistance (Rs ), and the decay of the discharge capacity is due to the passivity surface that increases the charge-transfer resistance (Rt) of the battery.

Abstract: CoO was usually added to the positive electrodes of MH/Ni batteries as the conductive agent. In this paper, well crystallized multi-walled carbon nanotubes (CNTs) with diameter about 10 nm were added to the positive electrodes of MH/Ni batteries together with CoO. During the process of transformation from CoO to CoOOH, a complex conductive network was created with CNTs as the frame. Because of the high conductivity and the excellent tension characteristics of CNTs, the charge-transfer capability of the electrode was improved and the integrality of the complex conductive network was enhanced. The electrochemical measurements indicated that the impedance of the electrode with CNT-CoO complex conductive agent was lessened compared to the electrode with simple CoO agent. Performance tests of the sealed batteries showed that the positive electrodes with CNT-CoO complex conductive agent exhibited higher discharge voltage, improved capacity, modified discharge stability and prolonged lifespan, especially at high current rates.

Abstract: In this experiment, electroless plating method was used to obtain the hollow nickel fibres. Polyacrylonitrile fibres with the diameter about 10μm and 3mm length were chosen as the templates of electroless-plating through screening and optimizing various fibres. Low temperature alkaline solution with the sodium hypophosphite as the reducer was adopted and the optimal parameters were determined. Polyacrylonitrile composite fibres with a dense nickel coating about 5~7 μm thickness were obtained. The plated fibres were then sintered in the air to remove the organic templates. It had been found that the sintering temperature had great influences on the formation of the hollow fibres. The Polyacrylonitrile fibres could not be removed completely at low temperature (300°C), and when the temperature increased to 400°C, no organic fibres could be observed from SEM and the hollow nickel oxide fibres with dense wall were obtained. However, when the sintering temperature further increased to 500°C, great changes had been found, the hollow fibres with brittle porous wall were obtained. A dense and uniform hollow nickel fibres with nickel content higher than 90% were finally obtained after the hydrogen reduction treatment at the temperature of 750°C for 2 hours.