Introduction to Sol-Gel Processing

Abstract

This chapter is focused on the chemical transformations of alkoxides or precursors derived from alkoxides in solution, to synthesize oxide sol-gel materials. It follows a pattern similar to Chap. 2. After addressing the structure of alkoxides, their hydrolysis and condensation reactions are next described, followed by a short review of the behavior of a few simple oxides made from these precursors: boron, silicon, aluminum, zirconium, and titanium oxides. The chemistry of silicon alkoxide is a special case, as it has seen a tremendous expansion during the last 20 years. The applications of glycol complexed silanes and polyhedral oligomeric silsesquioxanes (POSS) are summarized in special paragraphs. However, the functionalization of organo-alkoxysilane is largely connected to the very rich domain of hybrid organic-inorganic materials, and hence many of its aspects are treated separately in Chap. 10. The mixing of alkoxides with other alkoxides or precursors comes in a further section. Very interesting new sol-gel procedures, such as non-hydrolytic routes in water-free solvents, appear in the last section of this chapter along with their short review.