Sol–Gel Technology

Abstract

AbstractMany recent technical developments require materials fabricated by sol–gel technology. This article presents a short review of this huge field, with special accent on the various steps involved in the sol–gel processing technique and the applications of gels. The main definitions and historically scientific roots of sol–gel science are first briefly summarized. Then the specificity of the chemical process involved in the synthesis of a sol and a gel are examined with respect to the various classes of materials: silica, oxides other than silica, complex oxides, ceramics other than oxides and organic–inorganic hybrids. Drying a wet gel is a very critical step. The problems and techniques used to solve this are summarized, in particular the use of chemical additives and supercritical drying. Transformation of dry gels to dense ceramics by thermal treatment is briefly examined. Then the next major part of the article focuses on the interesting properties and applications of sol–gel derived materials, including dry aerogels, ceramic powders, fibers, coatings or monoliths, technical ceramics and materials for bioinorganic and medicinal applications. The last part gives a short account of the tremendous economical development, which the sol–gel technology presently experiences.