Scientists and engineers may knew the useful information about Aerogel long time ago but for me it is something new and very interesting. First time I saw the picture about Aerogel, make me remember about gelatin. Well.. maybe it is almost similar in appearance with gelatin but very different in function, endurance and the power.
Aerogel, also know as frozen smoke, is the world’s lowest density solid, clocking in at 96% air. If you hold a small piece in your hand, it’s practically impossible to either see or feel, but if you poke it, it’s like styrofoam. It supports up to 4,000 times its own weight and can withstand a direct blast from two pounds of dynamite. It’s also the best insulator in existence.
The writer about Aerogel in wikipedia explain that
Aerogel is a synthetic porous ultralight material derived from a gel, in which the liquid component of the gel has been replaced with a gas. The result is a solid with extremely low density[1] and thermal conductivity. Nicknames include "frozen smoke", "solid smoke", "solid air" or "blue smoke" owing to its translucent nature and the way light scatters in the material; however, it feels like expanded polystyrene (styrofoam) to the touch.
Aerogel was first created by Samuel Stephens Kistler in 1931, as a result of a bet with Charles Learned over who could replace the liquid in "jellies" 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 dried 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 dioxide. Carbon aerogels were first developed in the late 1980s.
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| A flower is on a piece of aerogel which is suspended over a Bunsen burner. Aerogel has excellent insulating properties, and the flower is protected from the flame. |
Properties
A flower is on a piece of aerogel which is suspended over a Bunsen burner. Aerogel has excellent insulating properties, and the flower is protected from the flame.
Despite their name, aerogels are solid, rigid, and dry materials and do not resemble a gel in their physical properties; the name comes from the fact that they are derived (composed) from gels. Pressing softly on an aerogel typically does not leave even a minor mark; pressing more firmly will leave a permanent depression. Pressing extremely firmly enough will cause a catastrophic breakdown in the sparse structure, causing it to shatter like glass – a property known as friability; although more modern variations do not suffer from this. Despite the fact that it is prone to shattering, it is very strong structurally. 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 just under 100 nm. The average size and density of the pores can be controlled during the manufacturing process.
Aerogels are good thermal insulators because they almost nullify the three methods of heat transfer (convection, conduction, and radiation). They are good conductive insulators because they are composed almost entirely from a gas, and gases are very poor heat conductors. Silica aerogel is especially good because silica is also a poor conductor of heat (a metallic aerogel, on the other hand, would be less effective). They are good convective inhibitors because air cannot circulate through the lattice.
Owing to its hygroscopic nature, aerogel feels dry and acts as a strong desiccant. Persons handling aerogel for extended periods should wear gloves to prevent the appearance of dry brittle spots on their skin.
The slight 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 smoky blue against dark backgrounds and yellowish against bright backgrounds.
Aerogels by themselves are hydrophilic, but chemical treatment can make them hydrophobic. If they absorb moisture they usually suffer a structural change, such as contraction, and deteriorate, but degradation can be prevented by making them hydrophobic. Aerogels with hydrophobic interiors are less susceptible to degradation than aerogels with only an outer hydrophobic layer, even if a crack penetrates the surface. Hydrophobic treatment facilitates processing because it allows the use of a water jet cutter.
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| A 2.5 kg brick is supported by a piece of aerogel with a mass of only 2 grams. |
