SMALL-ANGLE X-RAY-SCATTERING (SAXS) STUDIES OF SOL TO GEL TRANSITION IN K2O-AL2O3-SIO2 SYSTEM

The structural evolution during a sol to gel transition reaction in th e K2O-Al2O3-SiO2 system was investigated by using in situ small angle X-ray scattering (SAXS) technique. The results are interpreted as evid ence of the presence of at least two different gel phases. The analysi s shows that the primary phase is composed of small particles with cha racteristic size of similar to 3.0 nm, and considerable size and shape variation. The primary phase is identified as a random phase in the D ebye sense. The primary particles aggregate into larger formations wit h spherical symmetry. The size of larger aggregates (second phase) inc reases continuously in the course of gelation and levels off after rea ching similar to 15.0 nm. The volume fraction of the second phase keep s increasing until the end of the measurement which is far after the g elation (3-fold of the gelation time).