Abstract:
Titanium hydroxide derived from stoichiometrically hydrolysed modified precursors usually takes as much as 14 days to gel under ambient conditions. These systems can however be made to gel within a few hours by raising the sol temperature to above 80°C or alternatively, by lowering it to below 10°C. A gellability zone has been identified between 10°C and 80°C on the temperature axis and between 0 and 14 days on the time axis, for all chelate ratios up to 1:4. The spread of the acetyl acetone gellability zone is wider than that for ethyl acetoacetate leading to a wider range of microstructural controls that may be imposed upon such systems. The locus of gel points on the gellability zone separates the sol state from the precipitated state. Thermoreversible gelling is seen within the titania gellability zone.
