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February 4, 2013

Aerogel

While the diversity of stronger, lighter, less laborious and more energy efficient materials is continually expanding, there’s always room for improvement. And one material that’s developing towards greater application, some time after its inception, is aerogel, otherwise known as “frozen smoke”.

Being made up almost entirely of gas, aerogel has unique characteristics that distinguish it from other materials. It currently holds 15 entries in the Guinness World Records, more than any other material. You could protect yourself from a flame-thrower with aerogel, and even build yourself a warm protective dome on the moon with it.

Aerogel - photo by Jon Collier, Flickr - ImNotQuiteJack

Aerogel - photo by John Barrie, Flickr - jsbarrieThis is because the substance is made by extracting the liquid part of gels from alumina, chromia, tin oxide or carbon through supercritical drying. This liquid is then replaced with gas, leaving the material to comprise 99.8% empty space, which gives it its “frozen smoke” appearance.

By extracting the liquid of gels through superficial drying, the liquid is slowly dried off without causing the solid mass in the gel to collapse, which would most certainly happen with conventional evaporation. Once the gas fills the gel, what’s left is a very light solid with extremely low density and high thermal conductivity.

Gases are typically very poor conductors of heat, but good thermal insulators, as they largely annul the three methods of heat transfer – convection, conduction and radiation. Because aerogel is virtually impervious to heat, it has been investigated as a possible platform for building high-tech military armour.

Furthermore, aerogel is able to bear immense loads. This is due to the gel’s dendric microstructure, where its spherical particles of around 2-5 nanometres in size fuse together to form dense clusters.

Just how did this most interesting globule of strength come about? In 1931 Samuel Stephens Kistler came up with aerogel after waging a bet with Charles Learned over who could replace the liquid in gels with gas without causing the substance to shrink. It’s no surprise that Kistler won the bet, however aerogel wasn’t put into development until the late 1980s.

Here’s hoping that aerogel’s unique structural and insulating advantages will be further developed for commercial application, providing its benefits outweigh any latent cons.

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