Effect of a catalyst on the formation of SiC whiskers from polycarbosilane. Nickel ferrite as a catalyst

The effect of a catalyst, nickel ferrite, on the formation of SiC whiskers from porous bodies containing polycarbosilane and milled carbon fibers was studied. SiC whiskers were deposited at above 1373 K from porous bodies hav ing a catalyst, while noodle-like SiC products were obtained at above 1473 K from porous bodies having no catalyst. A scanning electron-microscopic an alysis and an energy-dispersive X-ray analysis revealed that SiC whiskers w ere formed via a vapor-liquid-solid process. An X-ray diffraction measureme nt revealed that the whiskers consisted of beta-SiC, and that their crystal linity was significantly high in spite of the heating temperature (1373 to 1623 K). Based on changes in the infrared absorption spectra and gas-evolut ion curves during the heating process, it was presumed that the pyrolyzing process of polycarbosilane in the two kinds of porous bodies, one with a ca talyst, and the other without a catalyst, remarkably resembled each other. SIC whiskers were proved to grow remarkably with decreasing the Si-O bondin gs by infrared spectroscopy and a chemical analysis. It could therefore be presumed that the formation mechanism of the SiC whiskers was analogous to that of silica-carbothermal reduction.