Effect of a Catalyst on the Formation of SiC Whiskers from Polycarbosilane. Nickel Ferrite as a Catalyst

Abstract

Abstract 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 having a catalyst, while noodle-like SiC products were obtained at above 1473 K from porous bodies having no catalyst. A scanning electron-microscopic analysis and an energy-dispersive X-ray analysis revealed that SiC whiskers were formed via a vapor–liquid–solid process. An X-ray diffraction measurement revealed that the whiskers consisted of β-SiC, and that their crystallinity was significantly high in spite of the heating temperature (1373 to 1623 K). Based on changes in the infrared absorption spectra and gas-evolution curves during the heating process, it was presumed that the pyrolyzing process of polycarbosilane in the two kinds of porous bodies, one with a catalyst, and the other without a catalyst, remarkably resembled each other. SiC whiskers were proved to grow remarkably with decreasing the Si–O bondings 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.