Formation Mechanism of Titanium Nitride from Titanium(III) Chloridet

Abstract

Formation mechanism of titanium nitride (TiN) by the reaction of TiCl₃ and N₂ in the presence of Al has been investigated by means of thermogravimetry, X-ray diffractometry and EPMA-SEM.
In a TiCl₃-Al-N₂ system, the reduction of TiCl₃ by Al began at ca.350°C in preference to the disproportionation of TiCl₃, and Ti was formed above ca.500°C by way of the formation of TiCl₂. At this temperature Ti reacted immediately with N₂ and with residual Al by competitive reaction to form TiN and A1Ti, respectively. TiN was formed by the reaction of AlTi and TiCl₂ under N2 at 500°C, too. On the other hand, in a TiCl₃-Al system AlTi was formed at 500°C and reacted with TiCl₂ above 700°C to form Ti2Al. This shows that a portion of TiCl₂ is reduced by Al in AlTi to Ti which has structural imperfections and is active against N₂.
In the TiCl₃ -Al-N₂ system, it was confirmed that TiN is formed above ca.500°C by nitridation of Ti formed by Al reduction of TiC13 and reaction of AlTi with TiCl₂. Above 700°CTiN was obtained as a single phase. The crystallite size and the amount of TiN increased with increasing temperature. The product obtained by this reaction at 1000°C for 2 hr had the composition of TiN0.90and the lattice constant of a0=4.234A.