Critical Evaluation and Thermodynamic Optimization of the Ti-C-O System and Its Applications to Carbothermic TiO2 Reduction Process

Based on the critical evaluation of available phase diagram, thermodynamic, and crystal structure data, the ternary Ti-C-O system is thermodynamically assessed using the Calculation of Phase Diagram method. Both binary Ti-C and Ti-O systems are reassessed to obtain the successful description of ternary Ti-C-O system for the first time. The liquid phase is described by the modified quasichemical model, which takes short-range ordering in liquid solution into account. All solid solutions are described using compound energy formalism. In particular, a completed solid solution between TiCx and TiOy with the excess solubilities of Ti, C, and O is accurately described with the (Ti, Va)(1)(C, O, Va)(1) solution structure. The thermodynamic models with a set of optimized self-consistent model parameters can reproduce available reliable experimental data within experimental error limits. The results are also applied to the thermodynamic analysis of complex carbothermic TiO2 reduction process. (C) The Minerals, Metals & Materials Society and ASM International 2015