One-step process of synthesis of ceramics of desired shape based on titanium, zirconium, and hafnium nitrides

Abstract

Using the approach of oxidative constructing, the synthesis of dense ceramics based on titanium, zirconium, and hafnium nitrides activated by resistive heating of a metallic preform of predetermined shape in a molecular nitrogen environment is carried out. It is found that nitridation of titanium, zirconium, and hafnium is controlled by interdiffusion of metal atoms to the surface of the preform and nitrogen atoms into the volume. It is shown that the presence of oxygen in the reaction medium leads to the formation of a surface oxide layer influencing the process of transport of nitrogen into the metal, and the entire oxidation process operates through the transport of metal atoms from the volume to the surface. In polycrystalline samples of zirconium and hafnium nitrides, a sharp decrease in the electrical resistance in the temperature range of 200–250 K is found.