This magical looking stuff is Aerogel. Formed by replacing the usually liquid "gel" with gas, it's incredibly light, impressively strong, and an amazing heat insulator.

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.(Those crazy scientists!). The first results were silica gels. Aerogel can be made of many different materials; Kistler's work involved aerogels based on silica, alumina, chromia, and tin oxide. Carbon aerogels were first developed in the early 1990s.



Silica aerogel holds 15 entries in the Guinness Book of Records for material properties, including best insulator and lowest-density solid.










To the touch, aerogels feel like a light but rigid foam, something between a Styrofoam peanut and the green floral foam used for potting fake flowers. Despite what their name may suggest, aerogels are dry materials and do not resemble a gel in their physical properties (the name comes from the fact that they are derived from gels). Pressing softly on an aerogel typically does not leave a mark; pressing harder will leave a permanent dimple. Pressing hard enough will cause a catastrophic breakdown in the sparse structure, causing it to shatter like glass--a property known as friability. Despite the fact that it is prone to shattering, it is very strong structurally, able to hold over 2000 times its own weight. Its impressive load bearing abilities are due to the dendritic microstructure, in which spherical particles of average size 2-5 nm are fused together into clusters. These clusters form a three-dimensional highly porous structure of almost fractal chains, with pores smaller than 100 nm. The average size and density of the pores can be controlled during the manufacturing process.

Aerogels are remarkable thermal insulators because they almost nullify three methods of heat transfer (convection, conduction, and radiation). They are good convective inhibitors because air cannot circulate throughout the lattice. Silica aerogel is an especially good conductive insulator because silica is a poor conductor of heat. (Metallic aerogel, on the other hand, would be a better heat conductor.) Carbon aerogel is a good radiative insulator because carbon absorbs the infrared radiation that transfers heat. The most insulative aerogel is silica aerogel with carbon added to it. SEAgel is a material similar to organic aerogel, made of agar.

Due to its hygroscopic nature, aerogel feels dry and acts as a strong desiccant. Persons handling aerogel for extended periods of time should wear gloves to prevent the appearance of dry brittle spots on the hands due to its hygroscopic nature.





Since it is mostly air, it appears semi-transparent. The color it does have is due to Rayleigh scattering of the shorter wavelengths of visible light by the nanosized dendritic structure. This causes it to appear bluish against dark backgrounds and whitish against bright backgrounds.

Aerogels by themselves are hydrophilic, but chemical treatment can make them hydrophobic. If moisture is absorbed, they will usually cause a structural change of contraction etc. and deteriorate; however, degradation can be prevented by turning them hydrophobic. The aerogel which has hydrophobicity to the interior can prevent degradation, even if a crack reaches deeper than its surface, compared with the aerogel that was turned hydrophobic only of their surface. Hydrophobic treatment makes processing easy because it allows the use of a water jet cutter.