RUTILE FORMATION IN HYDROTHERMALLY CRYSTALLIZED NANOSIZED TITANIA

The present study shows that peptization aids in the anatase-rutile tr ansformation in hydrothermally processed (250 degrees C, 4000 kPa) tit ania sols produced by the hydrolysis of alkoxide. HREM images show the presence of nanocrystals of 25-55 nm size, The anatase-rutile phase t ransformation in peptized titania is critically dependent on the condi tions of hydrolysis such as the water/alkoxide concentration ratio and the size of the alkoxide. Hydrolysis of the ethoxide gave rise to a p redominantly rutile phase whereas the isopropoxide and butoxide result ed in a predominantly anatase powder, under the same conditions of tre atment, BET surface areas decrease from 107.1 to 68 m(2)/g when the al koxide is changed from tert-butoxide to ethoxide for a given water/alk oxide ratio.