Abstract: Metal and/or metalloid nitride and/or carbide powders, e.g., amorphous or crystalline spherical particulates having a mean diameter greater than 0.2 .mu.m 90% of which being less than 0.4 .mu.m in size, well suited for the production of ceramic shaped articles exhibiting good thermomechanical properties and useful, for example, in the automotive and aeronautic fields, are prepared by flash pyrolyzing coarse drops of a precursor compound convertible into such nitride and/or carbide, at an elevated temperature and for such period of time as to convert the precursor compound into said amorphous or crystalline powder.

Abstract: Whisker-free particulates of silicon nitride (Si.sub.3 N.sub.4), e.g., spheres, beads, or a variety of other shaped articles exhibiting a regular and controlled particle size, are produced by incorporating a primary reaction mixture of silica and carbon into a porous, carbon-based matrix material, next carbonitriding the composite thus formed, and characteristically eliminating excess carbon from the carbonitrided composite.