Study of the TiC1-x – TiO2 reactive interface

The TiC1-x–TiO2 reactive interface obtained at 1100 °C has been studied by local structural investigations using Transmission Electron Microscopy (TEM) and X-rays microdiffraction. These results were completed by coupling complementary chemical characterizations by Nuclear Reaction Analysis (NRA), Rutherford Backscattering (RBS) and STEM (Scanning Transmission Electron Microscopy). A complex pattern of reactive interlayers of various thicknesses was formed as a result of the crossed redox reactions between TiO2 and TiC1-x. Our results show that the TiC1-x carbide is not oxidized by forming TiCxOy oxycarbides in spite of the complete solid solution existing between TiC1-x and TiO. TiC1-x is in fact destabilized by the oxygen liberated during the transformation of TiO2 into Magneli type compounds (TinO2n-1) to form the most reduced Magneli sub-oxides following the reaction: 3 TiCxOy + (5-3y)/2 O2 = Ti3O5 + 3x C. Starting from TiO2, a progressive reduction is achieved showing spatially distributed TinO2n-1 Magneli phases characterized by high values of n close to TiO2 and lower values of n as reaching TiC1-x. The most reduced term is shown to be Ti3O5. Ti3O5 thus represents the final product of the reaction at 1100 °C both for the reaction of reduction of TiO2 and for the reaction of oxidation of TiC1-x.