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 X-ray 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 cm3.g-1 (corresponding to average pore diameter of 20.42 nm) and specific surface area of 50.44 m2.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.