Effect of ageing on the formation, structure and crystallistation of titania colloids

摘要

Titania (anatase) sols have been produced by the hydrolysis of pure alkoxide with water, and peptisation of the resulting hydrolysate with dillute nitric acid at 333K. The rate of peptisation depended on a range of parameters, including the acid-titania mole ratio, concentration of solids, reaction temperature and the age of the hydrolysate. The z-awveraged aggregate size of sols produced from fresh hydrolysates decreased from an initial value in excess of 10 mum to less than 100 nm after 10 hours of peptisation, but then the sol slowly re-aggregated, reaching a final size of approx130nm after about 150 hours. In contrast, hydrolysates aged in pure water at ambient temperature for at least 21 days peptised at a slower rate than fresh hydrolysates, to about 100nm. These differences were interpreted using DLVO theory.