Aerogels Description

Aerogels.

Aerogels are solid, rigid, and dry materials that do not resemble a gel in their physical properties: the name comes from the fact that they are made from gels. Despite the fact that aerogels are among the lightest solid materials known to man, within the aerogel structure, very little is solid material, with up to 99.8% of the structure consisting of nothing but air. They were first invented in the 1930s as a result of a bet between Samuel Stephens Kistler and Charles Learned over who could replace the liquid in "jellies" with gas without causing shrinkage or in other words, without affecting the solid structure. Samuel Stephens Kistler won.Aerogels are created by combining a polymer with a solvent to form a gel, and then removing the liquid from the gel through supercritical drying and replacing it with air. The gel is put in a high-pressure vessel called autoclave and is heated to the high-temperature, high-pressure point called the critical point of the liquid when the liquid is transformed into a semi-liquid, semi-gas called a supercritical fluid. At this point there is no distinction between liquid and gas and when the vessel is depressurized, the solid skeleton, that 1% of the mass of the gel, is left behind intact, except for where there was liquid in the pores before is now gas, and that solid skeleton, that nanoporous solid is what is called aerogel.