PREPARATION OF LONG FIBROUS SILICON CARBIDE WHISKER CRYSTAL

摘要

In the semi-continuous or batch prodn. of SiC whiskers and their mats on a substrate by CVD at 1250-1500 deg.C from a gas mixt. contg. H2 and one or more oxygen-free cpds. contg. Si and C atoms in the presence of a metal catalyst, (a) a two-component Al-Fe catalyst is introduced during the growth period into the gas phase in the reaction zone by carbon redn. of an aluminosilicate ceramic contg. at least 73 wt.% Al2O3 and 0.3-3.0 wt.% iron oxides; and (b) the substrate is a woven fabric of carbonised rayon fibres pretreated, before carbonisation, with a borax soln. and a diammonium phosphate soln. to provide max. 4 wt.% B and max. 2 wt.% P in the fabric. Also claimed are mats of whiskers obtained by the above process, up to 80% of the whiskers being unidirectionally oriented.