Fabrication of nano-sized oxide composite coatings and photo-electric conversion/electron storage characteristics

Titanium dioxide TiO₂ can be used as a photo-anode to give generated electrons to the metal substrate under illumination. The transition metal oxide such as iron oxide Fe₂O₃ can be used to store electrons generated by the photo-electric conversion function of TiO₂ under the illuminated situation while the electrons are discharged from the transition metal oxide to the metal substrate in the dark. In this paper, coatings of nano-sized composite of TiO₂ and Fe₂O₃ were fabricated by the Warm Spray process, in which the feedstock powder is accelerated by a supersonic gas jet with speed above 1.0 km s^- 1 and temperature between 800 and 2500 K, and then impacted onto the target substrate continuously to form coatings. The coatings of TiO₂ and Fe₂O₃ nano-composite fabricated by Warm Spray showed no thermal deterioration such as phase transformation and particle growth of the feedstock during the spray process. The coatings fabricated by the Warm Spray had larger photo-current and the electron charge/discharge capacity than that by a conventional HVOF process. In addition, these characteristics were improved by decreasing the primary particle size of TiO₂ and Fe₂O₃.