Aerogel is a low-density solid-state material derived from gel in which the liquid component of the gel has been replaced with gas. The result is an extremely low density solid with several remarkable properties, most notably its effectiveness as an insulator. It is nicknamed frozen smoke, solid smoke or blue smoke due to its semi-transparent nature and the way light scatters in the material; however, it feels like expanded polystyrene (Styrofoam) to the touch.
Aerogel was first created by Steven Kistler in 1931, as a result of a bet with Charles Learned over who could replace the liquid inside a jam (jelly) jar with gas without causing shrinkage.
Aerogels are produced by extracting the liquid component of a gel through supercritical drying. This allows the liquid to be slowly drawn off without causing the solid matrix in the gel to collapse from capillary action, as would happen with conventional evaporation. The first aerogels were produced from silica gels. Kistler's later work involved aerogels based on alumina, chromia and tin oxide. Carbon aerogels were first developed in the early 1990s.
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