Study on the fabricated non-stoichiometric titanium dioxide by in-situ reduction with carbon powder via spark plasma sintering

A novel technology was proposed to fabricate non-stoichiometric titanium dioxide (TiO2-x) compacts in one-step thermal process by in-situ reduction of rutile TiO2 with carbon powder via spark plasma sintering (SPS). The rutile TiO2 powder was reduced with three different carbon powders for comparison, and the effect of the sintering conditions on the fabricated compacts was investigated. It is found that the in-situ reduction of rutile TiO2 with charcoal powder was easily achieved at a low pressure and high temperature (above 1473 K). Besides, the design of dynamic sintering pressure during SPS was proposed, and the results suggest that the dynamic sintering pressure contributes to the reduction of TiO2 and the fabrication of the compacts with high-density. In addition, density methods, X-ray diffraction, scanning electronic microscopy and laser micro-Raman spectrometer were performed to analyze the sintering sates, microstructures, crystal structures and phase distributions. The results show that a stable sintering environment without an increase in the pressure caused by reaction gas is a crucial role for the reduction of TiO2 and the TiO2-x fabrication, even the formation of Magneli phases TinO2n-1. Finer charcoal powder is more conducive to fabricating the compact with a single Magneli phase Ti6O11. It is expected to achieve a new breakthrough in fabrication method of the non-stoichiometric TiO2 by a safe and economically viable method.