ABSTRACT
This chapter examines the physics and chemistry of sol—gel processing and the ways in which these relate to the practical fabrication of ceramics and glasses. It is apparent that sol–gel processing offers considerable opportunities in both science and technology. A sol is a suspension of colloidal particles in a liquid or a solution of polymer molecules. A gel is a semirigid mass formed when the colloidal particles are linked to form a network or when the polymer molecules are cross-linked or interlinked. Metal alkoxides are the most common precursors used in sol–gel processing because they react readily with water. Structural evolution of sol—gel silicates in solution has been investigated on several length scales using a variety of techniques, such as nuclear magnetic resonanc, Raman and infrared spectroscopy, and x-ray, neutron, and light scattering. Prior to gelation, a sol or solution can be used for preparing thin films by common methods such as dipping, spinning, and spraying.
