Rutile formation in hydrothermally crystallized nanosized titania

The present study shows that peptization aids in the anatase-rutile transformation in hydrothermally processed (250 degrees C, 4000 kPa) titania sols produced by the hydrolysis of alkoxide. HREM images show the presence of nanocrystals of 25-55 nm size, The anatase-rutile phase transformation in peptized titania is critically dependent on the conditions of hydrolysis such as the water/alkoxide concentration ratio and the size of the alkoxide. Hydrolysis of the ethoxide gave rise to a predominantly rutile phase whereas the isopropoxide and butoxide resulted in a predominantly anatase powder, under the same conditions of treatment, BET surface areas decrease from 107.1 to 68 m(2)/g when the alkoxide is changed from tert-butoxide to ethoxide for a given water/alkoxide ratio.