Reaction-bonded titanium nitride ceramics

Reaction-bonded titanium nitride (RBTN) ceramics were formed using high surface area titanium powder (surface area 20 m(2) g(-1)), and nitrogen gas as precursor reactants. The titanium precursor was made by the combustion synthesis technique.(1) Owing to their microstructure and internal porosity, the metal particles are highly reactive towards nitrogen, and can be fully converted to the mononitride at comparatively low temperatures and short reaction times. Nitridation kinetics of these powders were determined at temperatures of up to 1000 degrees C by means of insitu gravimetry. Dry-pressed binderless porous titanium pellets were heat-treated in pure nitrogen at temperatures of up to 1000 degrees C, and fully converted to the porous TiN compacts With dimensional changes less than 5%. A reaction mechanism is proposed. The difference between the relative density of the final product and the packing density of the green body was negligibly small, but there is a considerable incr ease in the gas permeability and mechanical strength during nitridation. The porous end product is a suitable matrix for further applications and for making composites by infiltration deposition.