SAXS INVESTIGATIONS OF STRUCTURE FORMATION IN ALCOHOLIC ZRO2-SIO2 SOLUTIONS

Small-angle X-ray scattering was used to examine in situ formation of ZrO2-SiO2 structures in alcoholic solution of tetraethoxysilan (TEOS) as a function of the ratio of ZrO2 to SiO2. For the moment of the first measurement (15 min after the preparation) primary particles with R(g) approximate to 1.5 nm exist in all investigated mixed gels. These particles aggregated to secondary clusters. The resulting clusters can be described by means of fractal theory, where the determining mechanism of formation is cluster-cluster aggregation (diffusion or chemical limited). The time of gelation is a function of the ZrO2 concentration. The higher the ZrO2 concentration in the solution, the faster is the aggregation to secondary clusters. Gelation times were between 170 and 970 h.