X-ray diffraction study of Ti-O-C system at high temperature and in a continuous vacuum

The reduction of TiO2 by graphite or metallic titanium was monitored in an oven for X-rays with a graphite resistance under continuous vacuum. We demonstrate that this brought into play the formation of various oxides, oxycarbides and titanium carbides likely to be formed between 293 and 2300 K, in accordance with a reaction mechanism which we found to take place over four stages. We determined the crystalline characteristics at high temperature for all observed solid phases as well as their composition: TiO2-x, TinO2n-1 with 9 greater than or equal to n greater than or equal to 4,Ti2O3, TiO, Ti2O, TiC1-xOx, TiC. Particular importance is attached to the study of thermal expansion of Magneli phases which we identified at high temperatures as well as to that of the titanium sesquioxide phase. (C) 1999 Elsevier Science S.A. All rights reserved.