Microstructures and CO gas sensing properties of Cu-TiO₂ powders prepared by the oxidation of mechanically synthesized Cu-TiN and Cu-TiH₂ composites

Cu-TiH₂ and Cu-TiN powders were synthesized using a ball milling process under pressurized H₂ and N₂ atmospheres, respectively. Cu-TiO₂-h and Cu-TiO₂-n sensing materials were prepared by oxidizing the synthesized Cu-TiH₂ and Cu-TiN powders at 600 °C. The mean size of the Cu-TiN particles (34.5 nm) was much smaller than that of Cu-TiH₂ powder (106.1 nm). The TiH2 phase of the Cu-TiH₂ powder entirely changed to a rutile phase while Cu-TiO₂-n powder consisted of both anatase and rutile phases. The Cu-TiO₂-n device had higher responses than the others at all CO concentrations and operating temperatures of 250-450 °C. The Cu-TiO2-n powder exhibited an anatase phase and a larger surface area than the Cu-TiO₂-h powder. Additionally, the Cu-TiO₂-n powder had a microstructure with well dispersed CuOx. Therefore, it is believed that the mechanical nitrifying process is more effective to enhance the sensing performance of Cu-TiO₂ to CO gas.