ULTRASOUND AS A TOOL FOR THE PREPARATION OF GELS - EFFECT ON THE TEXTURAL PROPERTIES OF TIO2-SIO2 AEROGELS

TiO2-SiO2 aerogels have been prepared by hydrolysis and polycondensati on of alkoxides following two different methods: the classic one, usin g ethanol as a solvent, and the sonic one, by means of activation with ultrasound. The work is focused on the comparison of the textural pro perties of gels obtained by both synthetic routes. Nitrogen physisorpt ion, mercury pycnometry and transmission electron microscopy have been used as characterization techniques. The sonogels present higher valu es of specific surfaces and apparent densities, lower pore volumes, fi ner and sharper pore-size distributions and lower average particle siz e. These properties are discussed and related to the preparation techn iques.