Formation and Structure of Silicon Carbide Whiskers from Rice Hulls

Abstract

A study of the distribution of Si in rice hulls was carried out to aid in understanding the observed formation of SIC whiskers by the thermal decomposition and reaction of these natural materials. Scanning electron microscopy, Auger electron spectroscopy, and energy‐dispersive X‐ray analysis confirm the presence of a major amount of Si in the inner and outer epidermal regions of the rice hull. The Si is present as a hydrated amorphous form of SiO 2 which is evidently bound in the inner layer to organic constituents, placing it adjacent to a source of carbon but interfering with its solubility in HF. The SIC produced by pyrolysis is in the form of ultrafine particles with cubic crystal structure and whiskers exhibiting stacking faults and twins perpendicular to the whisker axis, easily visible by transmission electron microscopy. These whiskers are very similar to ones obtained by chemical vapor deposition with SiO and CO as the primary reactants.