Synthesis and Thermal Analyses of TiO₂-Derived Nanotubes Prepared by the Hydrothermal Method

TiO₂-derived nanotubes were prepared by hydrothermal treatment of TiO₂ powder in NaOH aqueous solution. High-temperature x-ray diffraction (HT-XRD) andthermogravimetry-differential thermal analysis (TG-DTA) demonstrated the formation of TiO₂ (B) phase (a metastable polymorph of titanium dioxide) from the nanotubes under heating at ∼800 °C, which indicates the as-prepared nanotubes should be composed of layered titanate, most probably as H₂Ti₃O₇·nH₂O (n < 3). Dehydration behavior and phase transformation confirmed by the HT-XRD study have suggested reliable reaction path and have well-solved the contradictions on the nanotube-formation mechanism among previous studies.