MANUFACTURE OF TRANSITION METAL CARBIDE AND CARBONITRIDE WHISKERS WITH LOW RESIDUAL AMOUNTS OF OXYGEN AND INTERMEDIATE OXIDE PHASES

摘要

The present invention relates to a method of producing whiskers, with low residual amount of oxygen, in large volumes and at low cost to be used as reinforcing material. The whiskers consist of solid solutions between two or more transition metal carbides, nitrides and carbonitrides, (Me1-X-YMe'XMe''Y..etc.)C1-ZNZ, having preferably submicron diameters. The whiskers are suitable for use as a reinforcement material in a wide range of materials, including metals, intermetallics, plastics, ceramics and metallic bonded hard material. The transition metal oxides, hydroxides or alkali compounds thereof are mixed with carbon powder. The carbon powder is added in a hyperstoichiometric amount with respect to the stoichiometric requirements. A halogenide salt is used as a volatilisation agent for the transition metals and a catalyst such as Ni or Co that is able to dissolve transition metals plus C and/or N. The reactant powders are blended so as to intimately mix them. Finally, the mixed starting material is subjected to nitriding, carbonising or carbo-nitriding heat treatments in order to produce the desired whiskers.