Advanced Materials Research Vols. 306-307

Abstract: In the present work, the MCF model for semisolid metal slurries (SSMS) is applied to investigate the thixotropy of the Al-6.5wt%Si alloy under cyclic shear deformation. The study shows that the semisolid Al-6.5wt%Si alloy has the behavior of thixotropy. The area of the hysteresis loop increases with decreasing the up-time, the initial shear rate and increasing resting time, solid volume fraction and maximum shear rate, respectively. These results have qualitative agreement with the experimental data. The origin of the hysteresis loop is atrributed to the difference between the deagglomeration rate and the agglomeration rate.

Abstract: Charged Au nanoparticles with various diameters, from 2.7 nm to 10.3 nm, were synthesized by using various reducing agents. Then charged Au nanoparticles were self-assembled onto the NafionTM membrane surface as methanol barriers. It was found that the proton exchange membrane self-assembled with 3.9 nm Au particles had the lowest methanol crossover. The proton conductivity decreased with the increase of the particles size until the particles size was more than 6.2 nm and they had little influence on the membrane conductivity. All the self-assembled membranes have higher open circuit voltage (OCV) and performance than original Nafion212TM membrane. And the membranes self-assembled with 3.9 nm poly (diallymethylammonium chloride) (PDDA) modified Au (PDDA-Au) particles had the highest performance due to the reciprocal of the methanol permeation current density and membrane area resistance.

Abstract: Flexible dye-sensitized solar cells (DSCs) were prepared by using carbon nanotube transparent conductive films (CNT-TCFs) as flexible substrates, and their photovoltaic properties were investigated as well. The flexible DSCs show typical photovoltaic characteristics with short-circuit current of 0.78 μA and open-circuit voltage of 1.48 mV, which was strongly influenced by heat-treatment temperature, type of dyes, and electrical resistivity. In light of their lighter weight and higher flexibility than conventional DSCs based on conductive glass substrates, the flexible DSCs have great potential as functional photoelectric components in many fields.

Abstract: This article presents the texture evolution and the ductility improvement of the cold-rolled foils of boron-free Ni₃Al during the recrystallization and the subsequent grain growth. The cold-rolled foils had sharp {110} textures. After the recrystallization at 873K/0.5h, the texture was disintegrated with several texture components. Interestingly, most of them had a single rotation relationship. i.e. 40˚ around <111>. With the progress of the grain growth, however, the texture returned to the sharp, cold-rolled textures. This two-stage texture evolution, called as “Texture memory effect”, was explained assuming a high mobility of the grain boundary with the 40˚<111> rotation relationship. The texture returning was highly effective to improve the ductility of the foils.

Abstract: The formidable and multivariate coal-mining conditions during the production often lead to various improper damage and inactivation of guide foot. Wear is the most severe problem. We do the research on optimization design of the materials by plasma cladding technic to improve the wear resistance: The Cr28MnV ferrous alloy overlay was deposited on the surface of 45# tempered steel backing. The martensitic structure with high strength, high hardness, and high abradability evenly distributed alloy carbide can be gained after cooling the overlay. The combined backing has a good obdurability which can satisfy the requirement of coal mine complex conditions after modifying treatment.

Abstract: In order to reduce the reflection of solar collector cover tube and improve its transmissivity, a kind of SiO₂ anti-reflective coating on the cover tube was prepared using acid-base two-step sol-gel method. The surface morphology of the anti-reflective coating was observed using atomic force microscope and electronic scanning microscope. The scratch resistance of the coating was tested using pencil hardness apparatus. The transmissivity and anti-impact properties of the cover tube coated with the coating were measured respectively by means of the spectrophotometer and the relative standard method. The results showed that the anti-reflective coating possesses a higher scratch resistance and the coated cover tube has good transmissivity and anti-impact.

Abstract: This paper presents the characteristic features of the catalytic properties of the cold-rolled Ni₃Al foils for methanol decomposition which were developed in our group. Methanol was effectively decomposed into H₂ and CO over the foils above 713 K. The production rates of H₂ and CO increased with an increase of time during the initial period of reaction, indicating that the Ni₃Al foils were spontaneously activated under the reaction conditions. Surface analyses revealed that fine Ni particles dispersed on carbon nanofibers formed on the foils during the reaction. The high catalytic performance of the foils can be attributed to the spontaneous formation of this nanostructure during the reaction.

Abstract: NiO/Ni nanocomposites were prepared by chemically reduction-oxidation process in tetra-ethylene glycol (TEG) solution. The structure and morphology of the samples were examined by XRD and SEM. The results indicated the composite consisted of NiO and Ni and exhibited spherical morphology with diameter of 50-200 nm. The electrochemical performances of composite electrodes used in electrochemical capacitors were studied. The electrochemical measurements were carried out using cyclic voltammetry, galvanostatic charge/discharge and impedance spectroscopy in 6M KOH aqueous electrolyte using three-electrode Swagelok systems. The results showed that the composite had a high specific capacitance and excellent capacitive behavior. The specific capacitance of the composite decreased to 192F/g after 500 cycles. Due to the existance of Ni, the charge transfer resistance is lower than 1Ω. It revealed that the composite exhibited good cycling performance.

Abstract: Metal hydride (MH) alloy (MmNi_3.81Mn_0.41Al_0.19Co_0.76) is modified by the electroless nickel plating and used as the electroactive material of negative electrode in Ni/MH batteries. The effect of the concentrations of reductant (NaH₂PO₂×H₂O), complex agent (Na₃C₆H₅O₇×2H₂O), reaction time, and reaction temperature on the Ni loadings and the utilization of the modified MH are systematically studied. The experimental results reveal that the appropriate reaction time and temperature of electroless nickel plating are 30 min and 70 °C in this work. The loading amount of Ni-P on MH alloy is increased and decreased by increasing the concentration of reductant and complex agent, respectively. The steady utilization of unmodified MH alloy is 94.7±1.0 % in the forming process under the charge/discharge conditions of 0.2C charge to 160% SOC (state of charge) and 0.2C discharge to 0.95V. The utilization of MH alloys modified with conditions of [NaH₂PO₂×H₂O] = 40 g L^-1 and [Na₃C₆H₅O₇×2H₂O] = 20 g L^-1, T = 70 °C, t = 30 min and [MH] = 2g/100 ml, respectively, is improved to 101.9±0.3 %.

Abstract: The combustion characteristics of some biomass samples, such as rice straw and its cellulose, were investigated. Non-isothermal thermogravimetry, where the sample was heated in air and the temperature of which increased at a linear rate of 10°C/min, 20°C/min, 30°C/min, was used to investigate the combustion characteristics of the biomass samples. The differences in the TG-DTG-DSC curves of the samples were determined and discussed in detail. Conventional TG parameters, ignition index of samples were estimated which provided elaborate information on their basic combustion features. Results showed that cellulose with higher combustion characteristics.