ABSTRACT
Colloidal Dispersions and Colloid Science . . . . . . . . 11
Commercial Colloidal Silicas . . . . . . . . . . . . . . . . . . 12
Sols, Gels, and Powders. . . . . . . . . . . . . . . . . . . . . . . 12
Colloidal Silica — Stability and Aggregation . . . . . 13
Gelation, Coagulation,
Flocculation, and Coacervation . . . . . . . . . . . . . . . . 15
Fractal Approach to Colloid Systems . . . . . . . . . . . . 17
Silica Nucleation, Polymerization, and Growth:
Preparation of Monodisperse Silica Sols. . . . . . . . . 19
Stability of Silica Sols . . . . . . . . . . . . . . . . . . . . . . . . 20
Silica Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Silanol Groups, Siloxane Bridges, and Physically
Adsorbed Water . . . . . . . . . . . . . . . . . . . . . . . . . 22
Concentration of Hydroxyl Groups on the
Silica Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Dehydration of the Silica Surface . . . . . . . . . . . . 27
Dehydroxylation of the Silica Surface . . . . . . . . 27
Rehydroxylation of the Silica Surface . . . . . . . . 28
Structurally Bound Water in Silica Particles . . . 30
Coalescence and Sintering . . . . . . . . . . . . . . . . . . 30
Particle Size and Characterization Techniques. . . . . 31
The Concept of Zeta Potential . . . . . . . . . . . . . . 31
Colloidal Dispersions. . . . . . . . . . . . . . . . . . . . . . . . . 31
Electrokinetic Effects and the Concept of
Zeta Potential . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Sol-Gel Science and Technology. . . . . . . . . . . . . . . 31
Gels and Powders . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Uses of Silica — From the Caves of Altamira and
Cro-Magnon to Silicon Valley and Outer Space . . 33
Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Silicon dioxide is the main component of the crust of the earth. Combined with the oxides of magnesium,
aluminum, calcium, and iron, it forms the silicate minerals in our rocks and soil.
