European Workshop on Glasses and Gels

J. Phys. IV France 02 (1992) C2-127-C2-130
DOI: 10.1051/jp4:1992214

Gel to glass transformation in base catalysed silica

K DAHMOUCHE¹, C. BOVIER¹, A BOUKENTER², J. DUMAS¹, E. DUVAL², C. MAI³ and J. SERUGHETTI<sup>1

1</sup>  Département de Physique des Matériaux, UA 172 CNRS, Université Claude Bernard, Lyon I, 43 bd du 11 novembre 1918, 69622 Villeurbanne, France
²  Physicochimie des Matériaux Luminescents, UA 442 CNRS, Université Claude Bernard, Lyon I, 43 bd du 11 novembre 1918, 69622 Villeurbanne, France
³  GEMPPM, UA 341 CNRS, INSA de Lyon, 20 avenue Albert Einstein, 69622 Villeurbanne, France

Abstract
The effects of heat-treatments on silica xerogels prepared from base catalyzed hydrolysis and condensation of TMOS are studied by low frequency Raman scattering, scanning electron microscopy, small angle X-ray scattering and BET measurements. Raman scattering in the range 3-700 cm-1 reveals a low-frequency band that arises from the discrete particulate character of base-catalysed gels at very small scale. A continuous evolution of the structure inside particles is observed during the thermal treatment and the Raman spectra is similar to the fused silica one after treatment at 1050°C. Electron microscopy observations of the nanostructure of the xerogels correlate with the particle Raman band maximum. Complementary SAXS and BET measurements allows us to propose a model for the gel-to-glass transformation.

© EDP Sciences 1992