STRUCTURAL STUDIES OF GEL PHASES .4. AN INFRARED REFLECTANCE AND FOURIER-TRANSFORM RAMAN-STUDY OF SILICA AND SILICA TITANIA GEL GLASSES

Infrared reflectance and Fourier transform Raman spectroscopy have been used to study silica and silica/titania monoliths produced by the sol-gel route which had been subjected to a series of heat treatments. With increasing thermal treatment temperature, the gel-glass matrix is strengthed by bond shortening and a reduction in mean Si-O-Si bond angle and angular distribution for this feature. Results obtained at a range of temperatures were in good agreement to those obtained for vitreous silica. The incorporation of low levels (3% by weight) of titanium led to more disordered glasses which contain titanium in tetrahedral sites only. Evidence was obtained for the formation of Si-O-Ti bonds, principally during the latter stages of densification at temperatures between 615 and 1000-degrees-C.