Mechanisms of Hydrogen-Assisted Magnesiothermic Reduction of TiO₂

Direct reduction of TiO₂ powder has been attempted for decades by researchers in an effort to decrease titanium (Ti) metal production costs. The main objective has been to avoid energy-intensive steps involved in production of primary Ti by the Kroll process. The emerging hydrogen-assisted magnesiothermic reduction process, which uses Mg to directly reduce TiO₂ powder under a H₂ atmosphere, has been shown to have the potential to compete directly with the Kroll process. The present studies represent an effort to understand the reduction reaction mechanisms of this process. Phase transformations and the reaction pathways are examined by SEM/EDX analysis of partially reduced powder cross-sectional, X-ray diffraction, and other analytical techniques. The results show important morphological changes, the prominent intermediate and final phases under the H₂ atmosphere, as well as the local deposition behavior of the MgO byproduct. The effect of the specific surface areas of the initial particles is also discussed.