Anodic Fabrication And Properties Of Oxide Nanotubes On Titanium Alloys

Highly-ordered Ni-Ti-O and Ti-Nb-O oxide nanotube arrays were fabricated through anodization of NiTi and Ti35Nb alloys, respectively. The hydrogen sensing properties of Ni-Ti-O and Ti-Nb-O nanotubes were investigated.Experimental results indicated that the Ni-Ti-O nanotubes could keep their aligned nanotubular structures at a high temperature of 475°C. At the operating temperatures of both 100°C and 200°C, the Ni-doped nanotubes heat-treated at 425°C presented a quick response and good sensing reversibility and repeatability after exposure to the reducing atmospheres containing 1000 ppm H₂. The electrical resistance of the Ni-doped TiO₂ nanotubes demonstrated P-type semiconductor behavior in the presence of hydrogen-containing atmosphere, which is quite different from that of the undoped TiO₂ nanotubes. The nanotubular structures of the Ni-doped TiO₂ could work at relatively lower operating temperature.The Ti-Nb-O nanotubes could keep the integrity of the nanotubular structures at a high temperature of 600°C. At room temperature, the Nb-doped TiO₂ nanotubes heat-treated at 450°C demonstrated a good sensitivity for wide-range detection of both dilute and high-concentration hydrogen atmospheres ranging from 50 ppm to 2% H₂. The Nb-doped TiO₂ nanotubes heat-treated at 600°C had no response to the hydrogen-containing atmospheres at room temperature but presented a quick response to the 1000 ppm H₂ atmospheres when the operating temperature increased to 100°C. The Nb-doped titania nanotubes have great advantages as a robust and wide-range hydrogen sensor operating at either room temperature or slighter higher temperatures.