No 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.

As the ancient metal, Sn is widely used in all aspects of human life. Nowadays, S, as the vulcanizing agent, is used in the process of refining tin to separate Cu and Sn. However, there are few reports about the other agent of removing copper from stannum. In this study, SnS, a new sulfiding agent to separate Cu and Sn, was investigated. During the process, SnS replaces the combination of Sn and Cu. The variables considered in the experimental study were reaction temperature, time and the ratio of reactants. The experimental data indicated under certain conditions, the removal rate of Cu reach 94.3%. At last, we studied the vacuum reaction of Cu2S and Sn, results indicated that under appropriate conditions, the Cu is detected. The SnS is formed. And after the vacuum reaction, the SnS could be used recycling. This work presented a promising technology for separating Cu from tin.

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.

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.