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A theoretical model to determine distribution of iron impurity during silicon purification by directional solidification with fluctuant crystal growth rate is proposed in this paper. The crystal growth rate is fluctuant usually and it has profound effect on the distribution of iron impurity in practical production. The model validation by the distribution of iron impurity during silicon purification...
A theoretical model for investigating the crystal growth rate and the solidified height during silicon purification by directional solidification is proposed. The growth rate is not constant usually and it has profound effects on the distribution of metal impurity in production process. The crystal growth rate and the solidified height, based on thermal equilibrium on the melt–crystal interface, were...
A numerical model is proposed to investigate influences of process parameters, including crucible pulling down rates and heater temperature, on crystal growth rates for silicon purification by vacuum directional solidification. The crystal growth rates of a silicon ingot are analyzed based on the interface energy balance equation combining with the temperature field calculated by software of ProCAST,...
The behavior of carbon in multicrystalline silicon scraps by electron beam melting was investigated in this study. It was found that the process favors nucleation of SiC on Si3N4. Furthermore, carbon tends to gather to top surface of the ingots with increasing melting time, and the reaction between oxygen and carbon favors carbon migration. The melt convection and temperature gradient caused by electron...
A theoretical model for investigating the back diffusion of iron impurity during silicon purification by vacuum directional solidification is proposed in this paper. The back diffusion of iron impurity in directional solidification process can markedly reduce the purifying effect; thus, clarifying the back-diffusion behavior of iron impurity has great significance in silicon purification by directional...
A multicrystalline silicon ingot was obtained from metallurgical-grade silicon after directional solidification under low vacuum condition. The concentration distributions of metal impurities such as copper (Cu), manganese (Mn) and sodium (Na) along the growth direction of the ingot were investigated. The result shows that the concentration of Cu and Mn decrease respectively from 28.56 ppmw and 10...
Purification process of MG-Si was limited by the difficulties involved in reducing boron content. The possibility of removing impurity boron (B) in MG-Si using CaO–Al 2 O 3 –SiO 2 –CaF 2 slags was investigated in the present study. Different from traditional research methods, the whole melting process was carried out under atmosphere condition, which was closer to the...
A multicrystalline silicon ingot was obtained from metallurgical-grade silicon by vacuum induction melting and directional solidification. Based on the concentration distributions of aluminum and calcium along the growth direction, the removal mechanism of such impurities with both high saturated vapor pressures and low segregation coefficients is investigated. The results show that the removal of...
The purification of metallurgical grade silicon, especially the removal of aluminum, was investigated by electron beam melting and solidification. Small amounts of silicon raw materials were melted in an electron beam furnace with same melting time and different solidification time to obtain the distribution of Al in silicon ingot. The removal mechanisms in different stages were also discussed. The...
In this paper a mathematical model is developed to investigate the removal of volatile impurities in molten silicon by electron beam melting (EBM) with a high efficiency and low energy consumption. The temperature distribution of molten silicon is obtained using the commercial software FLUENT. Based on the temperature distribution, the vaporization behaviors of phosphorus and silicon are investigated...
According to the traditional metallurgical theory, the evaporation process of phosphorus and silicon during silicon refining by electron beam melting (EBM) is discussed and a theoretical model is established to obtain the loss rate of silicon, the removal efficiency of phosphorus and the corresponding energy consumption. The results show that phosphorus can be removed from silicon melt efficiently...
Solidification rate has a significant influence on purification of silicon due to segregation of impurities at a liquid–solid interface of a solidifying silicon ingot. A mathematical model is developed to evaluate time-dependent position of the liquid–solid interface and solidification rate of electron beam melted ingots. A series of solidification experiments with different cooling rates are conducted...
During the refinement of metallurgical-grade silicon (MG-Si), Al and Ca cannot be reduced to a target level by conducting directional solidification only once. Electron beam candle melting (EBCM) is a new method that can be used to further reduce Al and Ca by directly melting Si ingots after directional solidification. A certain stable molten pool with a maximum surface area and a minimum depth exists...
Small amounts of metallurgical grade silicon were melted in an electron beam furnace in different experimental conditions in order to investigate the aluminum (Al) evaporation behavior during the electron beam melting (EBM) process. Impurity was significantly decreased in the early periods of melting at 9, 15, and 21 kW. These changes slowed down with the extension of the melting time. Moreover, the...
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