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Aerogel is basically a synthetic porous ultralight material extracted from a gel, where the liquid component for the gel has been removed and replaced with a gas without much of a collapse of the original gel structure. The final result is a solid with extremely low density and also extremely low thermal conductivity. It is also known as frozen smoke, solid smoke, solid air, solid cloud, blue smoke because of its translucent nature and the way it scatters light in the material. While silica aerogels feel like fragile expanded polystyrene when touched, but other polymer based aerogels feel like rigid foams when touched. Infact aerogels can be made from a myriad of chemical compounds.
The story of aerogel creation is also very interesting. It was first created by Samuel Stephens Kistler in 1931, due to a bet with Charles Learned on the pretext to replace the liquid in "jellies" with gas without causing much of a shrinkage.
Aerogel production is done by extracting the liquid component of a gel through supercritical drying (also known as freeze-drying). This process make the liquid to dry off at a very slow rate without causing the solid matrix in the gel to collapse due to capillary action, which could happen with conventional evaporation. The first aerogels were produced from silica gels, however later Kistler's work led to the development of aerogels based on alumina, chromia and tin dioxide. Also carbon aerogels were first developed in the late 1980s.
Aerogels are used for a variety of applications:
Firstly, aerogel is used in insulation. As for example, aerogel has been added in granular form to skylights for this purpose.
Secondly, as chemical adsorber for cleaning up spillage.
Thirdly, silica aerogels can also be used for filtration because of its high surface area, porosity, and it being ultrahydrophobic. They may even be used to remove heavy metals, which could be applied for wastewater treatment.
Fourthly, it can be used as a catalyst or a catalyst carrier.
Fifthly, silica aerogels have also found usage in imaging devices, optics, and light guides.
Sixthly, as a thickening agents in some paints and cosmetics.
Seventhly, as components in energy absorbers.
Eighthly, as a material for impedance matchers for transducers, speakers and range finders.
Ninethly, aerogels are used for more flexible materials such as clothing and blankets.
Tenthly, silica aerogel can also capture cosmic dust, also known as space dust. These aerogel dust collectors are known to have very low mass. NASA has also used aerogel for thermal insulation for the Mars rovers.
Eleventhly, metal aerogel nanocomposites can be used as catalysts, sensors, electromagnetic shielding, and in waste disposal.
Twelvethly, carbon aerogels have found usage in the construction of small electrochemical double layer supercapacitors.
Thirteenthly, Dunlop Sport is known for using aerogel in some of its racquets for sports such as tennis.
Fourteenthly, chalcogels have shown promise in absorbing the heavy metal pollutants mercury, lead, and cadmium from water.
Fifteenthly, aerogels can be used to separate oil from water, which could help in quick response to oil spills.
Sixteenthly, aerogels have found usage to disinfect water and killing bacteria.
Seveenthly, in aircraft de-icing, a new proposal has been made to use carbon nanotube aerogel.
Eighteenthly, silica aerogels may be used for sound insulation, such as on windows or for other purposes.
So we can see how a little event can change the course of history and benefit mankind as can be seen through the example of aerogel.
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