Metallic Silicon Powder Produced by Vacuum Decomposition of Magnesium Silicide Prepared by Magnesiothermic Reduction

Metallic silicon powder has been widely used for the production of various industrial materials and parts such as refractory ceramics, solar cells, military parts and so on. Herein, we attempted to prepare pure silicon powder from SiO2 by a magnesium thermal reduction process. A mixed-phase, Mg2Si + MgO, was obtained by the reduction of SiO2 powder by magnesium gas at 1223 K for 20 h. To extract pure silicon powder, Mg was separated by evaporation under vacuum through Mg2Si decomposition above 1073 K, leading to the formation of Si + MgO, and the MgO by-product was eliminated by dissolution in an aqueous hydrochloric acid solution. X-ray diffraction analysis confirmed the formation of pure Si powder and particle size shown in microstructure and oxygen content were analyzed to be 1∼5 µm and 1.5∼6 wt.%, respectively.