Keqiang Xie

Study on Volatilization Rate of Silicon Melt at Vacuum

Abstract In this paper, the theoretical volatilization rate of silicon was analyzed at different temperatures in order to study the temperature influence on the volatilization rate of silicon under vacuum conditions. The experimental volatilization rates of silicon were obtained by experimental measurements.

Theoretical Study on the Interactions of Impurity Boron on Si(110) Surface with H+, OH– AND O2

This paper proposed the optimization work for the Si(110) structure before and after Boron-doped based on the first principle of the density functional theory (DFT). Construction optimization, bond length and population and density of states (DOS) calculation were applied on Si(110) surface where the impurity element boron interacted with H+, OH− or O2. The results showed that the structure of Si(110) surface after Boron-doped was significantly affected, and the interaction between H+, OH− or O2 with boron on Si(110) surface also affect the structure of Boron-doped on Si(110) surface significantly; H+, OH− or O2 interacted with boron had no obvious effect on the length and strength of Si-Si bond, and the strength of the Si-B bond was significantly weakened in turn. The results provided a theoretical basis of exploring the reaction mechanism of boron removal by hydrometallurgy from metallurgical grade silicon (MG-Si).

Boron Removal from Silicon Using Secondary Refining Techniques by Metallurgical Method

Impurity removal, the purification process from metallurgical grade silicon (MG-Si) required to obtain solar grade silicon (SoG-Si), is crucial to the preparation of silicon-based solar cells. Some processes for boron removal by metallurgical method were reviewed. Secondary refining techniques, including gas blowing, slag treatment, plasma refining, solvent refining and other refining silicon techniques were summarized. The effects of gas species and slag systems on boron removal efficiency were emphatically discussed. Experimental and theoretical investigations show that a united technique of combining water vapor and oxygen gases blowing with slag treatment containing chloride or fluoride has achieved an amazing improvement for boron removal from molten silicon. Plasma refining and solvent refining also display high efficiency but acid leaching treatments, vacuum volatilization, electron beam and directional solidifications are hardly effective to boron removal. As for the potential industrial application of this united technique, the authors propose that some experimental and theoretical studies in dynamics should be further explored.

Effect of acetic acid on the leaching behavior of impurities in metallurgical grade silicon

ABSTRACT To explore the potential of acid leaching in purification metallurgical grade silicon (MG-Si) for solar cells, the effect of acetic acid on the leaching behavior was investigated in the present work by focusing on the behavior of impurities affected by the addition of acetic acid to a conventional acid mixture composed of hydrochloric acid and hydrofluoric acid. The etching results reveal that the HCl–HF–CH3COOH mixture is a better lixiviant for dissolving impurity inclusions in MG-Si. The extraction yield of impurities in HCl–HF–CH3COOH leaching was found to increase by 7% compared to conventional HCl–HF leaching.