Study of the TiC1-x – TiO2 reactive interface

The TiC_1-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 TiC_1-x. Our results show that the TiC_1-x carbide is not oxidized by forming TiC_xO_y oxycarbides in spite of the complete solid solution existing between TiC_1-x and TiO. TiC_1-x is in fact destabilized by the oxygen liberated during the transformation of TiO₂ into Magnéli type compounds (Ti_nO_2n-1) to form the most reduced Magnéli sub-oxides following the reaction: 3 TiC_xO_y + (5-3y)/2 O₂ = Ti₃O₅ + 3x C. Starting from TiO₂, a progressive reduction is achieved showing spatially distributed Ti_nO_2n-1 Magnéli phases characterized by high values of n close to TiO₂ and lower values of n as reaching TiC_1-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 TiC_1-x.