| The high purity Si powder was prepared by Self-propagating High-temperature Synthesis(SHS) Process from a mixture of SiO₂and Mg as raw materials. The effect of the processing parameters on the characteristics of the product such as molar ratio, particle size, compaction pressure and leaching conditions were studied. In the case of 20∼60 mesh of Mg particle size, the complete reduction of SiO₂ required excess magnesium, 2.6 mole, whereas unreacted SiO₂was completely eliminated with stoichiometric molar ratio, 2.0 mole of 140∼200 mesh Mg powder. As the Mg particle size was decreased, the combustion temperature increased and the particle size of the product decreased. The concurrently formed MgO in the product was leached with an diluted HCl solution at 70℃ for 3 hours. The product silicon had a purity of 99.88% which was higher than that of the reactant SiO₂. This is because the impurities were either volatilized at the high temperature generated during the rapid exothermic reaction or dissolved into the HCl solution during leaching. |
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