KINETIC APPROACH TO CARBOTHERMIC REDUCTION OF TITANIA

Kinetics of the titanium carbide synthesis by titania carbothermic red uction between 1470 and 1670 K, points out successively three reaction s: (i) the fast reduction of the dioxide into the suboxide Ti3O5 up to a progress coefficient alpha=0.17; (ii) the oxycarbide Ti2OC formatio n with c.f.c. structure (a 4.295 angstrom) for progress coefficient al pha like 0.17<alpha<0.75, associated with an energy of activation E = 380+/-20 kJ mol-1, involving the following steps: 2 Ti3O5 <-- --> 6 Ti O + 2 O2 6 TiO + 3 CO <-- --> 3 Ti2OC + 3 O2 5 O2 + 5 C --> 5 CO2 5 CO 2 + 5 C <-- --> 10 CO; (iii) the carbide formation resulting from the substitution of oxygen by carbon, according to a slow diffusional proc ess within the oxycarbide grains.