Hot pressing silicon carbide to obtain high density - using as additive a boride of silicon or aluminium, boron nitride or aluminium carbide

摘要

SiC ceramic having a density of >=95% theoretical density is made with the aid of an additive selected from SiB4, SiB6, AlB2, AlB12, BN or Al4C3, used in amt. 0.5-5 wt.% w.r.t. the wt. of SiC. The SiC ceramic is prepared by forming a homogeneous dispersion of 3 mu dia particles of SiC and the chosen additive (10 mu particles) and heating the dispersion to bring the density to the desired value, pref. under a pressure >=250 kg/cm2. and in a neutral atmosphere, at 1900-2100 degrees C for 5-30 mins. Process is less expensive than prior art since particles larger than 1 mu may be used, with consequent saving of grinding energy.