PROCESS FOR PRODUCING CARBON MATRIX MATERIALS AND THE MATERIALS SO-PRODUCED

摘要

Carbon matrix materials of low porosity and high density, and process of producing the same. The invention requires the use of a particulate heat-treated sub-alpha alumina as a matrix texture modifier. The preferred matrix texture modifier is heat-treated gamma-alumina, and is most preferably the waste dust collected during the calcination of aluminum trihydrate carried out as a step of the Bayer process for the production of alumina. The sub-alpha alumina is heated at a temperature of 400 - 450.degree.C, usually for 12 - 24 hours, before use as a matrix texture modifier in the present invention. As an alternative to the use of this preferred modifier, a similar modifier may be prepared by the low temperature calcination of aluminum trihydrate at 400 - 500.degree.C followed by milling to produce particles of an appropriate size (generally <50.mu.m). The material produced by the invention has a greater density, a smaller pore size and a reduced tendency to shrink and crack during carbonization than equivalent material produced without the use of the matrix texture modifier. When the material is a carbon composite (i.e. a carbon matrix reinforced by fibres and/or fillers), fewer subsequent densification and baking steps are required to prepare a useful product than is usually the case with conventional procedures. The product of the invention can be used for the same applications as conventional carbon matrix materials.