Phase Relations and Equilibrium Oxygen Partial Pressures in Iron-Titanium-Oxygen System at 1373 K

Abstract

Phase relations and the equilibrium oxygen partial pressures in the Fe–Ti–O ternary system at 1373 K have been studied using a thermogravimetric technique in various atmospheres buffered by a CO–CO2 gas mixture and X-ray diffraction technique. The results indicate that at 1373 K ilmenite (FeTiO3) can be reduced and decomposed to iron and rutile (TiO2). Consequently upgrading ilmenite to a rutile substitute is possible in principle.From the present results, the standard Gibbs energy change of the reactions in the temperature range of 1173–1373 K were obtained as follows:Fe(s)+FeTiO3(s)+1/2O2(g)=Fe2TiO4(s),ΔGr°/J·mol−1(Fe2TiO4)=−271600+63.35T⁄K±100,Fe(s)+TiO2(s)+1/2O2(g)=FeTiO3(s),ΔGr°/J·mol−1(FeTiO3)=−282400+62.93T⁄K±100.Both the activities of magnetite and ulvospinel in the Fe2TiO4–Fe3O4 spinel solid solutions coexisting with metallic iron at 1373 K obtained exhibit negative deviations from Raoult’s low.