Comparison of the Magnesiothermic Reduction Behavior of Nb2O5 and Ti2Nb10O29

Abstract

Nb-Ti binary alloys are widely employed as high value-added materials in the manufacture of super heat-resistant alloys, biomaterials, and superconductors. Therefore, there is significant interest to produce Nb-Ti master alloys in a cost-effective manner. In this study, we investigated the magnesiothermic reduction of Nb2O5 and Ti2Nb10O29 over the temperature range of 1073 to 1223 K and comparatively evaluated the reaction outcomes. The reduction product was composed of metal (Nb or Nb-Ti) particles and MgO, which covered the surface of the reduced metal particles. After the reduction reaction, the surface MgO phase was removed by pickling with hydrochloric acid (HCl) to finally recover the Nb metal or Nb-Ti alloy as a pure product. Scanning electron microscopy and X-ray diffraction analyses of the pure Nb metal and Nb-Ti alloy powders revealed that the reduction of both raw materials was successful at temperatures exceeding 1173 K. Reaction kinetics analysis revealed that the activation energy for the reduction of the mixed metal oxide (Ti2Nb10O29) is lower than that of Nb2O5 reduction. This is because of the different reaction mechanism behaviors during reduction and the different thermodynamic stabilities of the precursors.