Carbothermic Reduction of Oxide Powder Prepared from Titanium Dioxide and Cobalt Nitrate

摘要

The carbothermic reduction of a titanium-cobalt-oxygen-based oxide powder was analyzed to understand the carbothermal reduction step of the spray thermal conversion process for the synthesis of titanium carbide/cobalt composite powder. The starting powder was prepared by the combination of the spray drying and desalting methods using titanium dioxide powder and cobalt nitrate. The synthesized oxide powders were mixed with carbon black, and then these mixtures were heat treated under a flowing argon atmosphere. The changes in the phase structure and thermal gravity of the mixtures during heat treatment were analyzed using XRD and TG-DTA. The synthesized oxide powders have a mixed phase structure of anatase-TiO_2 and CoTiO_3 phases without regard to the cobalt content. These composite oxide powders were carbothermally reduced to the titanium carbide/cobalt composite powder through four steps with increasing temperature; reduction of CoTiO_3, reduction of anatase-TiO_2, formation of titanium oxycarbide and formation of TiC from titanium oxycarbide. The titanium carbide formability increased with the increasing relative amount of the complex oxide, CoTiO_3, in the titanium-cobalt-oxygen-based oxide powder.