Aerogel

A MIRACLE material for the 21st century could protect your home against bomb blasts, mop up oil spillages and even help man to fly to Mars.
Aerogel, one of the world’s lightest and expensive solids, can withstand a direct blast of 1kg of dynamite and protect against heat from a blowtorch at more than 1,300C. It has the lowest density of any product known to man, yet at the same time it can do so much. Although aerogel is classed as a solid, 99% of the substance is made up of gas, which gives it a cloudy appearance.
Aerogel is nicknamed "frozen smoke" and is made by extracting water from a silica gel, then replacing it with gas such as carbon dioxide. The result is a substance that is capable of insulating against extreme temperatures and of absorbing pollutants such as crude oil. For those of you who have always wanted to touch an aerogel, it feels like styrofoam. Silica aerogel is transparent with a blue color.

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, but early versions were so brittle and costly that it was largely consigned to laboratories.

It was not until a decade ago that Nasa started taking an interest in the substance and putting it to a more practical use. In 2002 Aspen Aerogel, a company created by Nasa, produced a stronger and more flexible version of the gel. It is now being used to develop an insulated lining in space suits for the first manned mission to Mars, scheduled for 2018. Aerogel is also being tested for future bombproof housing and armour for military vehicles. In the laboratory, a metal plate coated in 6mm of aerogel was left almost unscathed by a direct dynamite blast.



In the picture, you can see a 2 gm of aerogel easily holding a brick of 2.5 kgs.

How is Aerogel Made?
Aerogel starts out as a gel, called alcogel. Alcogels are made by polymerizing a silicon alkoxide with water in a mixing solvent (such as ethanol). The reaction occurs by hydrolysis and water condensation, joining together the alkoxide molecules making silicon-oxygen bonds to form oligomers (mini-polymers). The oligomers join together and form one giant molecule, which is the solid part of a gel. The silica matrix in the alcogel is filled with ethanol, having tiny little pockets 5 to 150 nanometers across. These tiny pockets of ethanol in the gel are called nanopores.
Aerogel is made by drying the alcogel and extracting the liquid from the solid silica component. Instead of evaporating the solvent, the gel can be supercrtically dried. Supercritical drying is a process in which liquid can be removed from a gel without causing the gel to collapse. Supercritically drying alcogel is a way for the liquid in the gel to slowly sneak out of the solid silica matrix without causing the silica matrix to collapse from capillary action. This is done by heating the gel past its solvent's critical point. Once the liquid has snuck out of the gel, the solvent can be vented off as a gas. The remaining solid is made of silica, with tiny pockets (nanopores) filled with air, and is 50-99% of the volume of the original alcogel. This solid is called an aerogel.

why is aerogel blue?
The same reason the sky is blue--Rayleigh scattering or Raman Effect.

Rayleigh scattering is an optical phenomenon that results when white light scatters off of particles smaller than the wavelengths of light, particles typically of the size 5 to 200 nm. These particles scatter the shorter wavelengths of white light more easily than the longer wavelengths, meaning that blue and violet are scattered the most. Our eyes are much more sensitive to blue wavelengths than to violet wavelengths, and so we only see blue light. Aerogels contain nanopores of air that are only a few hundred times larger than atoms. These nanopores, made of silica (which is what glass is made out of) act as particles that scatter white light and make the aerogel appear blue.

Isn't it a great invention of this century, the best part is it can be used to save the mankind by providng blastproof house, on the contrary the worst part is it is very expensive material on the earth.

Hope you had enjoyed getting this gyan, i know part of it is too technical, but thats easy to understand as well.