Abstract: The present invention is a process for producing .beta.-sialon based sintered bodies having a fracture toughness (K.sub.IC) of at least 6.5 MPam.sup.1/2.The process comprises preparing a feed that consists of 0.5-20 wt % of a sintering aid (e.g. MgO) with an average particle size of no more than 5.0 .mu.m, 3-40 wt % of an additive (e.g. SiC) with an average particle size of no more than 5.0 .mu.m, with the remainder being a .beta.-sialon powder having an average particle size of no more than 2.0 .mu.m, wet mixing the individual feeds to form a slurry, drying the slurry and sintering the dried slurry.

Abstract: A process for producing non-oxide compounds such as silicon nitride and silicon carbide by using a multi-stage apparatus constructed of a raw material drier section, a reactor section including a multiplicity of reaction vessels, and a non-oxidizing gas feeder section, is disclosed. The sections are arranged serially in the vertical direction. Raw materials are reacted with one another while fluidizing or bubbling by a hot non-oxidizing gas (argon or nitrogen) occurs in the raw material drier section and reaction vessels.