Aerogel must be one of the strangest supermaterials to ever exist. Ghostly and shimmering in appearance, it's insanely light, incredibly strong, and an amazing thermal insulator. And its tricks look absolutely impossible when you see them up close.
Made for Fun
Aerogel material—often referred to as frozen smoke, solid smoke, solid air or blue smoke—is actually, like all the best things, the result of a wager. It was first created by Samuel Stephens Kistler in 1931, after he bet Charles Learned that he could replace the liquid in a jelly with gas, without causing shrinkage. Turned out, he was right!
To produce an aerogel, you take a normal gel and then—very slowly and carefully—remove the liquid, leaving behind just the solid structure. That process varies depending on the gel in question, but invariably requires some complex chemistry to facilitate removal of the liquid by supercritical drying, which carefully avoids the liquid-gas transition by using pressure and temperature variation to go from liquid to solid to gas instead. Otherwise, the evaporation process can destroy the structure. The result is a substance that looks like the original gel but feels like expanded polystyrene to the touch.
And the material properties! Oh, the material properties. Just look at what it can do.
Aerogel Is an Amazing Insulator
All the trapped air in aerogel makes it a remarkable insulator. In fact, silicon aerogel has a thermal conductivity of about 0.03 W/mK in atmospheric pressure down to 0.004 W/mK in modest vacuum—values similar to those exhibited by air itself. Hold it to a flame, and you won't notice much happen, either—silica aerogel doesn't melt until it reaches upwards of 2,000 °F. No, really. Look.
Aerogel Is Insanely Light
It's not all silica gel, though. Yes, graphene aerogel sounds like someone combined the two buzziest of materials buzzwords—but the results are amazing. In fact, this graphene aerogel snatched the title of the world's lightest material just a few of months ago—with a density lower than that of helium and just twice that of hydrogen at 0.16 mg/cm3. This stuff practically floats. (Incidentally, it's got air inside, which means that it doesn't.) The material was created using a new technique which involves freeze-drying solutions of carbon nanotubes and graphene to create a kind of carbon sponge. The resulting material is both strong and elastic, as well as incredibly light.