Phase Transition of TiO2 Nanotubes: An X-ray Study as a Function of Temperature

Here, a study aimed to determine the phase transition temperature of titanium dioxide nanotubes, both in the presence and in the absence of a Ti layer underneath, is reported. Titania nanotube arrays with different diameters and wall thickness were synthesized via anodic growth at different potential values on a titanium foil. Ex and in situ high-temperature X-ray diffraction measurements were performed, respectively, on the arrays as such and on the powder obtained by detaching the nanotubes from the metallic substrate. Our results demonstrate that the presence of Ti dramatically influences the crystallization process decreasing the temperature formation of rutile, which tends to appear initially at the Ti/TiO2 interface.