A novel approach to directly produce Ti-Nb alloys through direct magnesiothermic reduction from intermediate TiNb2O7 (TNO) is demonstrated. Using a combination of X-ray diffraction, scanning electron microscope–energy dispersive spectroscopy, and scanning transmission electron microscopy, the observed phases, chemical composition, and crystal structure could be identified and the reaction pathway determined. Although thermodynamically favorable, the reductions carried out between 700°C and 900°C at various Mg/TNO stoichiometric molar concentrations showed 1.5 times the stoichiometric molar ratio (mass ratio Mg/TNO of 10.5) to produce Ti-Nb alloy products, but complete reduction was not possible owing to the depletion of Mg from vaporization and reactions. Excess amounts of Mg at 5 times the stoichiometric molar ratio (mass ratio Mg/TNO of 35) resulted in full reduction of the TNO powders to produce Ti-Nb alloys without Ti-Nb-Mg-O intermediate oxide phases. A comparison of the magnesiothermic reduction of the individual components, including TiO2, Nb2O5, and TNO, indicated the reduction of TiO2 to be complex and limiting, with reduction significantly easier for Nb2O5 and TNO at higher temperatures and excess Mg contents.
Bibliographical noteFunding Information:
This work was supported by the third stage of the Brain Korea 21 Plus Project of the Division of Creative Materials in 2017 (No. 2017-11-0016) and the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2018R1A2B2006609).
© 2019, The Minerals, Metals & Materials Society.
All Science Journal Classification (ASJC) codes
- Materials Science(all)