Dense shaped articles of polycrystalline alpha -silicon carbide and process for the manufacture thereof by hot-pressing

摘要

The invention relates to dense shaped articles of polycrystalline alpha -silicon carbide containing from 0.1 to 0.4%, by weight, of aluminum and optionally, a small amount of nitrogen and/or phosphorus, having a homogeneous virtually single-phase microstructure. The additional constituents are substantially in the form of a solid solution in the alpha -SiC lattice. The shaped articles are distinguished by flexural strength of at least 600 N/mm2 up to 1450 DEG C. and low subcritical crack propagation under mechanical stress. The fracture mechanism is trans granular up to at least 1450 DEG C. The shaped articles are manufactured by simultaneously shaping and hot pressing pulverulent alpha -silicon carbide containing a small amount of an aluminum-containing additive, such as aluminum powder, aluminum nitride and/or aluminum phosphide, at temperatures between 1850 DEG C. and 2300 DEG C. under a pressure of at least 100 bar (10 MPa).