Papers by Author: Bin Yang

Abstract: The disproportionation of AlCl was investigated by thermodynamics analysis. The results demonstrated that Gibbs free energy change of the disproportionation of AlCl decreases with decreasing temperature and increasing the AlCl pressure. The onset temperature of the disproportionation is 1521K in the standard atmosphere, and those are 878K and 1096K, respectively, at the AlCl partial pressure of 5Pa and 200Pa as the AlCl₃ partial pressure is 200Pa. The AlCl equilibrium partial pressure is about 10^-4Pa at 500K, demonstrating that the disproportionation of AlCl is complete below this temperature. The temperature in the condenser used in the experiments was below 1200K and the top near to the water-cooled cover of the furnace should be below 500K, therefore the disproportionation of AlCl occurred and was completed in the condenser.

Abstract: Ion exchange method was used to remove the sodium ions from the mother liquor of sodium fluorosilicate in this study. Some experiments were done at different conditions of the amount of 732 resin, reaction temperature and time. At the same time, the regeneration method of 732 resins and the effect of removing sodium ions of the regenerative resins were investigated either. The optimum conditions were obtained. The result indicated that ion exchange method was feasible. And the resins could be regenerated and reused for many times. Ion exchange method was pollution-free and low cost in the treatment process of mother liquor of sodium fluorosilicate.

Abstract: Preparing titanium powders by calcium vapor reduction of titanium oxide directly is a new way with short flow sheet and CaTiO3 is the very important intermediate compound in this process. In this paper, the behavior of intermediate CaTiO3 in the reduction process of TiO2 was investigated. The thermodynamic calculation indicated that the Gibbs free energy change of the reaction to produce CaTiO3 by CaO and TiO2 was always negative below 1000 °C; The reaction Gibbs free energy change of the calciothermic reduction of CaTiO3 was lower than that of TiO, which would be the most predominant step from TiO2 to Ti. The experimental results showed that CaTiO3 phase derived from the reaction between TiO2 and the reduction by-product CaO, and the reaction between TiO2 and the decomposition product CaO from the additive of CaCl2 with crystal water as well in the calcium vapor reduction process of titanium oxide. But CaTiO3 could be reduced to Ti much easier than that of TiO2 by calcium vapor.

Abstract: The extraction of aluminum by the AlCl disproportionation process in vacuum was researched using the furnace designed by ourselves. The features of aluminum products were characterized by X-ray diffraction, scanning electronic microscope and energy-dispersive X-ray spectroscopy. The results indicated that the purity of aluminum products increased with decreasing condensation temperature; aluminum products could be oxidized as their size was too small; the residues of the extraction of aluminum from alumina could be further treated with this process to generate metallic aluminum with a little carbon; aluminum products with high Al₄C₃, C and Al₂O₃ impurities could be purified by this process. The conclusions could provide bases for the industrial application of the process.

Abstract: In this study, high-purity Li₂CO₃ was prepared by carbonation-decomposition and ion-exchange methods using the industrial-grade lithium carbonate, and the effect of cycles and ion-exchange of the mother liquor on purification was investigated. Results showed that the process of cycles can improve the purity and productivity of Li₂CO₃. The impurities (such as K, Na, Ca and Mg) could be removed in the process. The purity of product decreased and the impurity contents increased after 4 cycles. At the same time, the ion-exchange process by D412 resin was used to deeply remove the residual Ca and Mg after the simple carbonation-decomposition and cycle process. The comparison of different flowing speed of solution through the ion-exchange resin indicated that the low flowing speed was beneficial for the deep removal of the Ca and Mg. considering the problem of efficiency, the flowing speed of 10-20 ml/min was appropriate. The high purity and productivity of Li₂CO₃ indicated that the carbonation-decomposition method combining with the mother liquor cycles and ion-exchange method has a good perspective in the field of lithium carbonate purification.

Abstract: We used high-purity multicrystalline silicon prepared by metallurgical method for the study of directional solidification. The optical microscope was used to observe the etch pits on the surface of silicon wafers, and we calculated their dislocation density. The result showed the space distribution of dislocation density presented “V” shape for each ingot produced at different drop-down rates. The dislocation density of slicon ingots followed the order 10<20<30<40μm/s. The high-resolution glow discharge mass spectroscopy was used to analyze the concentration of transition metal impurities. The macro-morphology of vertical-section of silicon ingots growth at different drop-down rates was observed. The x-ray diffraction measurement was performed to analyze the crystallographic orientations of the silicon ingot growth at 20μm/s, which was a better drop-down rate for producing high-quality multicrystalline silicon.

Abstract: Vacuum evaporation is usually utilized to remove volatile impurities in metallurgical grade silicon to prepare solar grade silicon by metallurgical routes. Especially phosphorus needs to be removed by vacuum evaporation. And the removal efficiency of impurities strongly influenced the quality and performance of products. In this paper, the removal efficiency of impurities is studied by using different raw material. The results indicated that the content of impurities in raw material had deep effect on the removal efficiency of vacuum evaporation. The high quality product can be obtained by vacuum evaporation only once from raw materials with the lower content of impurities whereas it is not for high content of impurities in raw material. This is due to the vapor-liquid equilibrium in the vacuum furnace. The impurities can be removed effectively by vacuum evaporation many times.

Abstract: La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) thin film electrolytes were fabricated on La0.7Sr0.3Cr0.5Mn0.5O3-δ (LSCM) porous anodes by radio-frequency (RF) magnetron sputtering. The formation and microstructure of LSGM thin films were characterized by X-ray diffraction(XRD) and scanning electron microscopy (SEM). The effects of different sputtering conditions, such as Ar gas pressure, substrate temperature and sputtering power, on the performance of LSGM electrolyte film were estimated. Dense LSGM thin film electrolytes with thickness of about 2μm, which are compatible with LSCM-based anodes and without crack, have been successfully fabricated on LSCM-based anode supports by RF magnetron sputtering when sputtering power density is 5.2W·cm-2, Ar gas pressure is 5Pa and substrate temperature is 300°C. It is found that high sputtering power density and high Ar gas pressure, as well as high substrate temperature, are beneficial to deposition of dense electrolyte thin film, close bonding of electrolyte thin film with anode substrate, and formation of large three phase boundaries between anode and electrolyte.

Abstract: The diffusion layer and melt of silicon-boron are respectively obtained after quenched in water at 1300 oC by using metallurgical grade silicon (MG-Si) powder and amorphous boron powder. The phase equilibria for boron in MG-Si have been investigated by using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The back scattered electron (BSE) image of diffusion layer displays the intermediate phase SiB4 in silicon-boron phase band, and the XRD results also indicate that SiB4 exists in silicon-boron diffusion layer at 1300 oC. It is inferred that the intermediate phase SiB4 is formed by the reaction (Si) + SiB6 ↔ SiB4 according to the equilibrium composition of Si/B=4/1 as quantified by Energy Dispersive Spectroscopy.

Abstract: The carbothermal reduction of alumina in a vacuum was investigated by XRD and thermodynamic analysis. Experiments on mixtures of alumina and graphite in a vacuum furnace at 1743-1843K proved that the residues consisted of Al2O3and C, and the deposits formed on the upper wall of the crucible contained Al4O4C, C, Al4C3 and Al2O3. Thermodynamic analysis indicated that alumina should react with carbon to form gaseous Al2O and Al above 1671K and 1713K at 100Pa respectively, Al2O and Al react back with CO to form Al4O4C, C, Al4C3 and Al2O3, which constitute deposits.