Colloid Chemistry of Silica: An Overview

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