The effects of excess carbon on the surface area and crystallinity of TiO₂ powders prepared by oxidizing mechanically-synthesized TiC and their CO gas-sensing properties

TiC-ec (with 20 at% excess carbon), with TiC and TiN powders as comparative samples, were synthesized via ball milling. TiO₂-ec and TiO₂-n, TiO₂-c sensing materials were prepared by oxidizing the synthesized TiC-ec, TiC, and TiN powders at 600 °C. Structural characterization was performed via X-ray diffraction, field emission scattering electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The mean particle size of TiO₂-ec was the smallest (40.8 nm), and its SSA was the largest (14.3 m²/g). The anatase crystallinity of the TiO₂-ec powder was higher than those of the TiO₂-n and TiO₂-c samples, although the particle size was the smallest. The response of TiO₂-ec to 1000 ppm CO gas at a working temperature of 550 °C was the highest (4.0) while the TiO₂-c and TiO₂-n samples showed a smaller response (1.2 and 1.4, respectively). The improved sensing properties of the TiO₂-ec samples were due to a better crystallinity and larger surface area. Therefore, the enhanced surface area and crystallinity of the TiO₂-ec are believed to be related to the presence of excess carbon.