Influence of the TiO_2 precursors on the thermal and structural stability of titanate-based nanotubes

摘要

The influence of different TiO_2 precursors (laboratory-prepared sol-gel powders, dried and thermally treated at 400 ℃, and commercial powders such as anatase by Aldrich and P25 Aeroxide by Evonik) on the structure and morphology of the titanate nanotubes obtained by hydrothermal method was investigated by x-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. In all cases, titanate-based nanotubes were obtained, having similar structure and morphology. The effect of the thermal treatment on the structural stability was also studied by differential thermal analysis and thermogravimetry analysis (TG/DTA) and differetial scanning calorimetry (DSC) measurements up to 600 ℃, to determine the transformation of titanate nanotubes into other phases. Complementarily, by XRD investigation, the phases that develop after the thermal treatment of the titanate nanotubes in 110-400 ℃ temperature range were identified. The TEM micrographs come to confirm the deterioration of morphology and transformation from nanotubes to particles. The thermal stability of the investigated nanotubes led to the conclusion that this property depends not only on the sodium content but also on the type of precursor. The highest thermal stability was noticed for the nanotubes synthesized starting with anatase (Aldrich) commercial powder.