SiC whiskers from rice hulls: formation, purification, and characterisation

High purity beta-SiC whiskers, 50-60 mu m long and <1 mu m diameter, have been prepared by the pyrolysis of rice hulls in a reduced pressure of nitrogen at 1000-1500 degrees C without the use of external reducing agents of catalysts. Characterisation of the product by X-ray diffraction, scanning electron microscopy, infrared spectroscopy, and chemical analysis confirmed the formation of beta-SiC whiskers as the major component with a small amount of particulate material of the same composition. Cleaning the pyrolised product with an acid treatment removed small amounts of amorphous material and wool like fibres, to leave it consisting essentially of smooth beta-SiC whiskers with needle like morphology. The physical and chemical characteristics, and the mechanism of formation of the whiskers are discussed.