ABSTRACT
Sol-gel materials encompass a wide range of inorganic and organic/inorganic com posite materials which share a common preparation strategy. They are prepared via sol-gel processing involving the generation of colloidal suspensions (“sols”) which are subsequently converted to viscous gels and thence to solid materials. 1 This controlled method has many advantages, which led to its historical use before the underlying scientific principles were understood. In recent years increased under standing of these principles has led to a great increase of interest in the method, and to its application in the production of a wide variety of advanced materials. To appreciate these developments it is first necessary to consider some general features of the process.
