Characterization of Nano-crystalline Metallurgical-Grade Silicon Prepared from Rice Husk Ash

Rice husk (RH), an agricultural waste product, contains a large proportion of silicate minerals, making it a potential source of low-cost metallurgical-grade silicon (MG-Si) suitable as a solar-grade silicon material. Processing rice husk ash into MG-Si requires careful control of temperature and time during the initial ashmaking procedure and subsequent refinement to remove impurities. In this work, silica of between 95.24 and 98.03% has been prepared from RHA (ash made at 700, 800, 900, and 1000 degrees C for 6 h). Furthermore, the silica value was boosted by use of hydrometallurgical purification process. The improved purification processes yielded between 99.18 and 99.51% of silica. The metallic trace impurities were significantly reduced beyond detection of the X-ray Fluorescence (XRF) after the final processing step. Metallothermic reduction of pulverized Mg and SiO2 mixture at ratio 1:1 g was post hydrometallurgical purified to further eliminate all soluble impurity. XRF showed silicon powder with purity >98% and the X-ray Diffraction (XRD) showed that Rice Husk Ash (RHA) transformation from amorphous to crystalline material depends on temperature and time. Transmission Emission Microscopy (IBM) investigation shows that derived silicon consists of agglomerate polycrystalline materials with grain sizes of 20-67.08 nm.