Study of TiO2 nanocrystallites in TiO2-SiO2 composites

A titania-silica nanocomposite system with six different compositions (10/90, 20/80, 40/60, 50/50, 60/40, 80/20 molar ratio of TiO2/SiO2) was prepared by a sol-gel method. Different experimental techniques such as XRD, TEM, EDAX, DTA and density measurements by Archimedes' method were used to characterize each compostion. The synthesized specimens had two structural phases: (i) crystalline TiO2 in anatase form; and (ii) a Si-O-Ti bonded glassy phase. TEM results showed that spherical shaped TiO2 particles are dispersed in a disk-shaped Si-O-Ti bonded glassy matrix. This glassy matrix creates an anti-sintering effect, which controls the growth of the TiO2 particles. The size of the TiO, crystallites vary with an increase of the sintering temperature and in the range 10-50 nm. At 1300 degrees C, two types of structural modifications, (i) anatase to rutile and (ii) crystallization of SiO2, occur within the system. The calculated bulk density value increases with sintering temperature and also with an increase of TiO2 concentration. (C) 1998 Elsevier Science B.V.