Impact of Hydrothermal Processing Conditions on High Aspect Ratio Titanate Nanostructures

High aspect ratio TiO x nanostructures were produced by simple hydrothermal treatment and the nature of two distinct morphologies, compact nanofibers and hollow nanotubes, was explored as a function of preparation conditions. The crystal phase of the TiO 2 starting material was found to be a key parameter for the determination of the general morphology, whereas particle size mainly influenced the conversion yield. Other parameters, such as hydrothermal temperature and solid/liquid ratio, exert control over the size and shape of the product. The findings can be interpreted in terms of a dissolution/recrystallization formation mechanism. Detailed characterization by Raman spectroscopy and X-ray/electron diffraction is provided; the data show that the nanoscale products were based on a variety of hydrated and often sodium-containing titanate crystal phases, such as trititanate or pentatitanate, rather than anatase or rutile. Variations in the washing procedure were found to have no significant influence on the overall morphology of the products, but did affect other properties, such as the specific surface area and annealing behavior, that are important for many practical applications.