Cryomilling-Assisted Synthesis of Nanostructured Silicon

Rice husk-derived nanostructured silicon is synthesized using a cryogenic milling system. After calcination of rice husk at 700C, obtained silica was mixed with magnesium powder via cryomilling at -100°C for 1 to 6 hours, followed by a magnesiothermic reduction heat treatment. Electron microscopy results revealed the quality of mixing process with no chemical reaction occurred during milling as confirmed by Xray diffraction analysis. Prolonged cryomilling not only improved the distribution of the powders but also provided a highly active magnesium powder inside the mixture. As a result, a final product with larger total pore volume and higher surface area was obtained. Finally, cryomilling for 6 hours combined with magnesiothermic in powder form (as compared to pelletized material) resulted in the highest total pore volume of 0.258 cm^3.g^-1 (corresponding to average pore diameter of 20.42 nm) and specific surface area of 50.44 m^2.g^-1. The average crystallite size of all samples is in the range of 45.57 to 53.28 nm,thus confirming formation of the nanostructured silicon.