Advanced Materials Research Vols. 690-693

Abstract: Analysis of the vibration characteristics of slope is the basis of dynamic analysis of slope; therefore, it has an important engineering significance. In this paper, ideal joint rock slope was studied by the modal analysis and harmonic response analysis module in the ANSYS software, meanwhile, the section of the model size and the effects of the structural parameters on the vibration characteristics of slope were also discussed. The results show that the stiffness of the structural surface is the key factors that affect the vibration characteristics of slope, and with the stiffness of structural surface increases, the first modal shape of slope was changed from dislocation vibration that along the structural surface to horizontal vibration. Only the first natural frequency can be excited the "resonance" phenomenon in the horizontal direction under the seismic load. Therefore, the joint slope is more easily to be excited "resonance" under earthquake load because of the first natural frequency of joint slope is smaller than homogeneous slope; moreover, this is consistent to the investigation results of Wenchuan Earthquake.

Abstract: Since the country put forward the construction of low carbon city, government and citizens begin to make energy saving, environmental protection, and low carbon consciousness into their daily life. Construct the overall evaluation system of urban low-carbon level helps accurate understanding and quantifying citys low-carbon level, thus promotes its construction and development. Based on the analysis of the connotation of low carbon city, this paper selects indicators from six aspects, which are low-carbon economy, low-carbon construction, low-carbon traffic, low-carbon life, low-carbon environment and low-carbon society, to construct the evaluation system of urban low-carbon level, and assess whether the city had done a good job on low carbon development.

Abstract: The effect of natural slope stability due to the tunnel excavation in mountainous areas is studied used influence function method, and one tunnel excavation project in Hebei province was analyzed, the theoretical results obtained are in good agreement with the real monitoring data, therefore, the influence function method can be effectively used to predict the ground displacement caused by tunnel excavation in mountainous area, which could provide the basis for the evaluation of the safety of such works.

Abstract: Directional Solidification System (DSS) is the commonly used casting station in the solar industry. In order to better understand the casting process, we carried out global simulations of heat transfer to investigate effect of argon gas flow on the thermal field in a directional solidification system for multi-crystalline silicon (mc-Si). The effect of argon gas flow on the global heat transfer and the melt convection are investigated. It was found that the heat transfer at the melt free surface due to the gas convection can not be neglected, though the argon gas flow contributes little to the global heat transfer at most radiative surfaces.

Abstract: The distribution of impurities in metallurgical grade silicon before and after slag treatment was investigated for the purpose of upgrading metallurgical grade to solar grade silicon. It was found that metal impurities co-deposited with silicon and formed different intermetallics in the precipitated phase, and these intermetallics such as Si-Fe, Si-Ni, Si-Ti-V and Si-Ca-Al-Fe were substituted by Si-Fe-Ti-V after treatment of Na2CO3-SiO2 slag. Non-metallic impurities B and P were nearly homogeneous distribution in metallurgical grade silicon before and after slag treatment. Moreover, a particular analysis of the microstructure of slag has been carried out, it was determined that metal impurities Al and Ca could easily migrate from silicon to slag phase in the refining process.

Abstract: In this paper, magnesium hydride was used to react with water using a new design of control strategy to produce maximized on-demand hydrogen generation from the hydrolysis reaction. Magnesium hydride is the chemical compound MgH2, which contains 7.66% by weight of hydrogen and as a potential hydrogen source. Although the concept of reacting chemical hydride with water to produce hydrogen is not new, there have been a number of recent published papers which might be employed as on site generation of hydrogen for fuel cell applications. Under room temperature, the hydrolytic reaction between magnesium hydride and water to form a thin-layer of magnesium hydroxide on the outer surface impedes water from coming into direct contact with the magnesium hydride. The key to continual removal of this coherent magnesium hydroxide layer can induce the reaction of magnesium hydride with water near room temperature by the addition of citric acids. These additions act to disrupt the magnesium hydroxide layer on the magnesium hydride. This concept of using the magnesium hydride reaction with water to produce hydrogen has the following conclusions. This study presents a maximized on-demand hydrogen gas generator capable of producing hydrogen at an almost-constant H2 rate, which using this approach can reach the 6.4% by weight of hydrogen. In addition, based on the kinetics of magnesium hydride-water reaction, it does not need any noble-metals catalysts to meet the minimum hydrogen flow rate for fuel cell power systems. Finally, the cost of producing hydrogen from magnesium hydride-water approach would cost approximately $15 per kg hydrogen.

Abstract: Silicon was purified by solvent refining with Si-Sn binary alloy system. Two descend mold velocities, 10mm/h and 100mm/h were tested in directional solidification of the alloy melt. The morphology, structure and the ingredient of the ingots have been investigated by SEM, XRD, EPMA, GDMS and ICP-MS. The contents of Fe, N, C , Ca, Mn, Cu, P and B are significantly lower than that in raw silicon. Furthermore, the acid leaching experiments were introduced to remove tin from silicon. The temperature of acid leaching and the type of acids were the predominant conditions in tin separation from silicon by acid leaching.

Abstract: SiO-based materials as a new anode material has attracted widespread attention in lithium-ion battery industry for their high theoretical specific capacities. In this work, the SiO/C composites were prepared by a modified stöber method with TEOS and organic compounds (epoxy resin and sugar) as raw materials. The electrochemical performance of the prepared SiO/C composites were investigated by electrochemical charge/discharge tests and AC impedance method. As carbon source, epoxy resin can make the SiO/C composite with a higher specific capacity and stable electrode structure during charge/discharge process. The EIS results reveal that the SiO/C composite electrode derived from epoxy resin exhibits a higher lithium ion diffusion coefficient.

Abstract: Many studies show spinel LiMn2O4 is one of the most promising cathode materials for lithium ion batteries. At present, urgent need is that capacity attenuation in the process of charge / discharge and cycle stability at high temperature are developed. The methods can be classified into bulk doped, surface coated and nanometer particles. Research progress about improving the electrochemical performance of spinel LiMn2O4 is summarized and further research trend is pointed out in this paper.

Abstract: In order to better understand the casting process, we carried out global simulations of heat transfer to investigate the temperature distributions in furnace at 80 mm of insulation cage elevation and 40% of silicon melt solidification for multi-crystalline silicon (mc-Si) ingot using an industrial directional solidification furnace capable of producing 500 kg silicon ingot. The effect of heater position and the crystallization state of silicon melt on temperature distribution and interface shape are discussed as well to provide the essential knowledge for system optimization.