AEROGELS AND THEIR APPLICATIONS

Aerogels have been in existence now for 60 years. The attraction which these low density materials exert on physicists, chemists and material scientists can be recognized from the approximately 200 papers on aerogels currently published each year. In a recent issue of Science, aerogels were rated among the top ten scientific and technological developments. This paper describes the most important methods to produce silica and other aerogels. It reports on possibilities to modify these materials by sintering and doping. In addition, the most suitable experimental techniques to investigate the nanostructural build-up are described. Several promising applications for silica aerogels are briefly described: monolithic silica aerogels are used in Cerenkov detectors in high energy physics; several houses have been insulated with layers of translucent granular silica aerogels for passive solar energy usage; opacified aerogel powders are being tested as substitutes for CFC-blown polyurethane foams and as thermal superinsulations in heat storage systems; experiments are performed with aerogels as catalytic substrates, as acoustic impedance matching layers and as gas filters; and another new application is the use of aerogels in radioluminescent light and energy sources.