Effect of temperature on morphology and phase transformations of nano-crystalline silica obtained from rice husk

Pyrolysis of rice husk (RH), an agricultural by-product, was studied at different temperatures (700–1100°C) in the presence of air. The changes in morphologies, compositions and phase transformations were studied critically by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffractometry, respectively. Different phases of silica obtained from RH were observed with respect to change in temperatures. Crystallite size and the amount of silica obtained from RH at each temperature were worked out using X-ray diffractometer (XRD) plots. Nano-crystalline silica could be revealed (4.87–18.61 nm) from charred RH at different temperatures (700–1100°C). The amount of silica with respect to other carbonaceous volatile matter was calculated from the XRD plot. Acid treatment (1 : 1 HCl) of RH was also done to remove the metallic impurities. A thermal analysis of raw RH was done to study the decomposition and energy changes in it.