Platelets for producing silicon carbide platelets and the platelets

Abstract

A process for producing silicon carbide platelets having a size of 20 .mu.m or less, and the platelets so produced. The process comprises reacting particles of a non-graphitizable form of hard carbon containing 0.5-1.5% by weight of aluminum and at least 0.2% by weight of iron (preferably anthracite coal, most preferably Pennsylvania anthracite), with silica or a silica precursor at a temperature in the range of 1800.degree.-2100.degree. C. under an inert atmosphere. If the carbon contains 0.2-1.0% by weight of iron, 0.1-10% by weight of boron, relative to the weight of SiO.sub.2, is added (if not already present). In the invention, 0.1-10% by weight of the reaction mixture of alpha silicon carbide particles having a size of 5 .mu.m or less are added to the reaction mixture to control the size of the platelets so that a majority have a size of less than 20 .mu.m. The carbon is in the form of particles of less than 50 .mu.m and the silica or precursor is preferably in the form of particles of less than about 1 .mu.m. The weight ratio of silica to carbon is greater than 1.67:1. The resulting small SiC platelets are substantially unagglomerated, have a high percentage (up to 95%) of small (<20 .mu.m) platelets and preferably have an aspect ratio greater than 5. The platelets can be used as reinforcements for ceramic and metal matrix materials.