Molecular chemical aspects of silica gel formation

This chapter describes some molecular chemical aspects of the formation of silica gels from aqueous silicate solutions. Experiments involved silicon-29 nuclear magnetic resonance spectroscopy and small-angle scattering of X-rays. Cations are shown to significantly affect the dissolution and oligomerization processes responsible for the formation of silica gels. Aging of aqueous silica gels is described in terms of the changes in fractal dimensionality of the silica structure. Preliminary SAXS experiments on gel transformations occurring in zeolite A synthesis mixtures indicate large-scale changes in gel morphology before crystalline zeolite formation occurs.