METAL CORED CERAMIC SURFACED FINE POWDER MATERIAL AND APPARATUS AND METHOD FOR MAKING IT

摘要

A ceramic surface-metallic core particle composite fine powder material is disclosed, composed of fine particles each having a metallic core and a ceramic surface layer, in which the average value of the ratio of the thickness of the surface layer of a powder particle to the radius of the particle is substantially greater than 0.05. A method and an apparatus for making this material from core metal and a gas which combines with the core metal to form the ceramic outer layer are also described, in which a gaseous mixture of vapor of the core metal and the gas is passed through a convergent-divergent nozzle and is thereby rapidly cooled by adiabatic expansion so that the core metal as it solidifies forms metal cores for fine particles while the gas reacts with the outer layers of these particles to form ceramic surface layers.