Carbothermic reduction of anatase and rutile

The carbothermic reduction of anatase and rutile to TiC was investigated using a combination of thermogravimetric analysis and X-ray diffraction. Samples premilled for 50 h prior to heat treatment showed a much greater extent of reduction compared with the unmilled powders. Heating the rutile up to 800 °C and anatase up to 870 °C showed no evidence for reduction with the observed mass loss attributed to desorption of gas. After heating to 800 °C, most of the anatase has transformed to rutile. The reduction of rutile started at ∼830 °C whilst anatase underwent reduction at 870 °C. The initial identified products were Ti5O9 and Ti4O7 with the latter being the last apparently stable phase prior to TiC formation. The TiC formed from anatase was apparently stoichiometric whilst that from rutile was clearly sub-stoichiometric. Reasons for the difference in reduction behaviour are discussed.