AGGREGATION MODEL OF SONOGELS ON SINTERING

This work presents the application of a geometrical model to dry gels prepared by ultrasonic energy applied to alkoxide-water mixtures (sono gel). The xerogel structure is described as a hierarchical arrangement of spherical units clustered in successive steps. The model takes int o consideration the clustering index (number of elementary units in a cluster) and the hierarchical ratio (quotient of cluster to elementary unit size), and accounts for the degree of branching and connectivity along sintering. The structural parameters have been evaluated from s mall-angle X-ray scattering and gas adsorption data (Brunauer-Emmett-T eller method). The results reveal ultrasonic dose-dependent structural changes on sintering in the 200-900 degrees C temperature range.