The Sol-Gel Process for Non-Metallic Inorganic Materials

Abstract

This paper will give an overview over the potential and some special aspects of the sol-gel process. The sol-gel process has gained interest in industry as well as in the scientific field during the last 20 years. In general, the process describes the transition of a system from a liquid (mostly colloidal) into a solid (gel) phase. The gel phase may be defined according to P. Flory as at least diphasic where one phase is solid and where two phases are interpenetrating. The high interest in most cases results from the possibility of synthesizing non-metallic inorganic materials like glasses, glass ceramics or ceramic materials, at low temperatures compared to the high-temperature process required by glass melting or firing. In the past, a lot of work was carried out in order to investigate the potential of the process, the mechanisms and industrial applications. This work was carried out mainly from the materials science point of view in order to synthesize materials with special properties or to be able to use new and advantageous techniques. It could be shown that with different techniques it is possible to vary range of the composition of the synthesized materials over a wide range of the periodic system of elements [1 – 10].