SOLID TITANIUM NITRIDE AND OTHER REFRACTORY COMPOUNDS MADE BY DIRECT GAS/METAL REACTION

Compacts of various metal powders have been prepared and converted to continuous oxide or nitride solids by heating in the appropriate atmosphere. The properties of the materials prepared in this way are described. They were: AIN, Al2O3, Cr2N, Cr2O3, MgO, Si3N4, TiN, and ZnO.Particle size, compact porosity and cohesion, and the reaction-temperature programme all affected the nature of the finished product. The best results were obtained where the metal had a low vapour pressure at the reaction temperature and where the change in molar volume from metal to compound was small. For these reasons, the reaction method is not suitable as a general process but for one of the materials, titanium nitride, it was very successful. This is of special interest since this material is difficult to sinter or hot press. Titanium nitride was made by the reaction method with a voids content of only 13% and a bend strength of 30,000 lb/in2.For a given material, optimum temperatures for the reaction method were low compared with those of conventional manufacturing methods. Special shapes were easily prepared from the parent metal. These advantages may justify the application of the technique to other potentially suitable compounds, which are suggested.