In situ characterization of the effects of Nb and Sn on the anatase–rutile transition in TiO2 nanotubes using high-temperature X-ray diffraction

New metastable β-type Ti alloys for biomedical applications containing biocompatible alloying elements such as Nb can present remarkable mechanical behavior. Whenever the performance of an implant produced from β-type Ti alloys is considered, it is crucial to take into account their surface properties because they are intimately associated with osseo-integration. The osseo-integration of orthopedic implant devices made from CP–Ti to β-type Ti alloys depends directly on the properties of the oxide layer formed on their surface. The aim of this study was to investigate the formation of self-organized TiO2 nanotubes by an anodization process on CP–Ti and Ti–35Nb and Ti–35Nb–4Sn alloys (wt.%) and analyze the effects of Nb and Sn additions to CP–Ti on the amorphous–anatase and anatase–rutile phase transformations in TiO2 nanotubes using glazing-angle high-temperature X-ray diffraction. The results obtained suggest that the crystallization of TiO2 formed on CP-Ti occurs at 225 °C, whereas the anatase–rutile transition occurs at 400 °C. As Nb was added to Ti, the temperatures at which these phase transformations occur increased. When Sn was added to Ti–35Nb alloy, the kinetics of the phase transformations appeared to decrease.