A systematic study of four parameters within the alkaline hydrothermal treatment of three commercial titania powdersanatase, rutile, and Degussa P25was made. These powders were treated with 5, 7.5, 9, and 10 M NaOH between 100 and 220 °C for 20 h. The effects of alkaline concentration, hydrothermal temperature, and precursor phase and crystallite size on the resultant nanostructure formation have been studied through X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and nitrogen adsorption. Through the correlation of these data, morphological phase diagrams were constructed for each commercial powder. Interpretation of the resultant morphological phase diagrams indicates that alkaline concentration and hydrothermal temperature affect nanostructure formation independently, where nanoribbon formation is significantly influenced by temperature for initial formation. The phase and crystallite size of the precursor also significantly influenced nanostructure formation, with rutile displaying a slower rate of precursor consumption compared with anatase. Small crystallite titania precursors formed nanostructures at reduced hydrothermal temperatures.
Abstract-Novel nanostructured titania nanotubes and hydrogen titanate nanoribbons were synthesised using hydrothermal treatment of Degussa P25. The nanostructure types formed were monitored as a function of the hydrothermal conditions. Changes in structure was evaluated using X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Raman spectroscopy.X-ray photoelectron spectroscopy (XPS) of Ti(2p 3/2 ) and O(1s) binding energies in titania nanotubes were measured and a systematic trend in the XPS binding energies was observed. This indicated a strengthening of the Ti-O bond occurred as the material phase changed from titania nanotube to the titanate ribbon form. The changes in binding energies for both the Ti and O XPS peaks were consistent with changes observed in the Raman spectra of nanostructured titania.
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