Alkoxide and colloidal silica gels and glasses, a comparison.
01 January 1985
A brief review of the structure of alkoxide and colloidal silica gels is presented. Hydrolysis and polymerization reactions at pH 8 result in the formation of interconnected, phase separated structural. One phase is a continuous three-dimensional network of silica glass with OH groups on the pore surfaces. The second phase is a water-alcohol solution in the pores. This structure is compared with Warren's structureal scheme for Na20 - Si02 glasses. At higher pH, silica is formed as particles. Gelation of collodial silica in water is attributed to the formation of hydrogen bonds between OH groups on the surface and water. The pore structure of the two types of gels is considered and its effect on sintering to glass is discussed.