ON THE TITANIUM CARBIDE TIC SYNTHESIS FRO M OXYCARBIDE TI2OC

Titanium carbide synthesis from oxycarbide Ti2OC following equation: T i2OC + 2 C --> 2 TiC + CO is the ultimate step in the industrial proce ss of carbothermic reduction of titanium dioxide. There is not really one solid/solid reaction but two simultaneous solid/gaz reactions Ti2O C + CO --> 2 TiC + O-2 2 C + O-2 double left right arrow 2 CO with an apparent activation energy of 492 +/- 12 kJ.mol(-1). The reaction mech anism is governed by a diffusionnal process whose limiting step is pro bably the centripetal diffusion of carbon inside tile oxycarbide grain s. Their composition slowly slides towards that of carbide during the reaction, but no morphological change is observed, except the growth o f the cubic lattice parameter from that of the oxycarbide (0.4295 nm) to that of the carbide (about 0.432 nm) which remains always slightly sub-stoechiometric.