Dense sintered shaped articles of polycrystalline alpha -silicon carbide and process for their manufacture

摘要

There are provided shaped articles of polycrystalline silicon carbide having densities of at least 97% and improved mechanical properties particularly at high temperatures, said articles consisting of at least 95.4% by weight of alpha -silicon carbide, about 0.1 to 2.0% by weight of additional carbon, about 0.2 to 2.0% by weight of aluminium, about 0 to 0.5% by weight of nitrogen, and about 0 to 0.1% by weight of oxygen, the alpha -silicon carbide being in the form of a homogeneous microstructure with an average grain size of less than 10 mu m. There is also provided a process for the preparation of such articles by pressureless sintering submicron powder compacts consisting of alpha -silicon carbide and aluminium- and carbon-containing additives as sintering aids.