Aerogel is the lightest and lowest-density solid known to exist

Submitted by enlively on Sat, 07/05/2008 - 18:37.

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Aerogel is a super-strong substance and is the lightest solid known to man.It is nicknamed frozen smoke,solid smoke or blue smoke due to its semi-transparent nature and the way light scatters in the material.

Aerogel isn't exactly space-age technology. It was invented in 1931 by Steven Kistler, in response to a bet made by a fellow scientist. Kistler found a way to remove the liquid from a silica gel without destroying the long silica molecule chains that gave the gel its structure.

It's so light it feels nearly weightless, like a chunk of solidified fog or smoke.It's cloudy, translucent and virtually weightless and is also surprisingly tough.This exotic substance has many unusual properties, such as low thermal conductivity, refractive index and sound speed in addition to its exceptional ability to capture fast moving dust.It is the lightest and lowest-density solid known to exist, and holds an unbelievable 15 entries in the Guinness Book of World Records, including best insulator and lowest density solid.

Aerogel is comprised mostly of air and weighs only three times as much. It has insulating properties 37 times greater then fiberglass.It can withstand a direct blast of 1kg of dynamite and protect against heat from a blowtorch at more than 1,300C.In the image above, the material is insulating a hand from the heat of a blowtorch.

(The matches on top of the aerogel are protected from the flame underneath)

Aerogel is not like conventional foams, but is a special porous material with extreme microporosity on a micron scale. It is composed of individual features only a few nanometers in size. These are linked in a highly porous dendritic-like structure.
Modern scientists make aerogel by pressurizing and heating an ordinary gel to its "supercritical" point, where the liquid's fluid and gaseous phases are indistinguishable, and then draining off the supercritical liquid. Because there's no gas-liquid interface, there is no surface tension and so the liquid can be removed without destroying the gel's polymer structure. With the liquid gone, air fills up the spaces between the polymers, and the result is a meringue-like aerogel.

(A 2.5 kg brick is supported on top of a piece of aerogel weighing only 2 grams)

There are a variety of tasks for which aerogels are used:

Because the substance is near transparent, it could be sandwiched between panes of glass or perhaps used in paint for an insulating coating on walls and ceilings or as a thickening agent.
Commercially, aerogels have been used in granular form to add insulation to skylights.

(Closeup of particles that have been captured in aerogel are shown here)

Chemically similar to glass, aerogel is used on the space shuttle to trap tiny spaceborne particles traveling at high speed so they can be brought back to Earth for analysis.
NASA used aerogel to trap space dust particles aboard the Stardust spacecraft. The particles vaporize on impact with solids and pass through gases, but can be trapped in aerogels. NASA also used aerogel for thermal insulation of the Mars Rover and space suits.

It certainly looks very promising and could prove to be a revolutionary technology in an age obsessed with making objects lighter yet stronger.

Source:

http://eetd.lbl.gov/ECS/aerogels/
http://en.wikipedia.org/wiki/Aerogel
http://www.unitednuclear.com/aerogel.htm
http://www.timesonline.co.uk/tol/news/uk/science/article2284349.ece
http://www.lbl.gov/Science-Articles/Archive/aerogel-insulation.html

With research and development proceeding at an ever increasing rate, it is likely that many more advances in aerogel technology and applications are imminent.