Synthesis of Titanate Nanotubes Under Hydrothermal Conditions and Their Acid Stability

Abstract

Products with different nanostructures are prepared by hydrothermal treatment on commercial TiO2 nanopowders in NaOH solution and followed by post washing. The hydrothermal treatment from 0 h to 72 h affects not only the extent of particle-to-nanotube conversion but also the extent of nanotube-to-nanofiber conversion. After 36 h of hydrothermal reaction, P25 nanopowders transform into nanotubes. Nanofibers are the major products if the reaction proceeds up to 72 h. The surface area of the nanotubes reaches ca. 357 m2/g at 36 h and decreases to ca. 21 m2/g at 72 h. For structural analysis, FE-SEM and TEM are used. Results show that post washing treatment is a key factor in controlling the morphologies of the final products; intermediate nanosheets transform into nanotubes or nanofibers during post washing process. XRD analysis indicates that post-treatment can also affect the chemical composition of the final nanoproducts. The structural stability of the nanotubes in acid aqueous solution is also studied. The local structure of as-prepared nanotubes gradually collapses as the proof the backwashing solution decreases. This finding demonstrates that titanate nanotube is acid sensitive material.