In the summer of 2009 before entering Caltech I went to D.C for some congressional seminar. During a tour of the city two friends and I ditched the group and headed to the Smithsonian Air n Space Museum. I'd heard about aerogel, and I knew the museum had it on display so I was itching to see it. It looks so ethereal:
silica-based frozen smoke
It's particularly useful in space missions when you want to bring back airtight samples in a zero gravity environment. You can trap space dust which would otherwise vaporise in a solid medium and pass through a gaseous one. Aerogel seemed like the Goldilocks zone between solid and gas.
a star dust collector with aerogel blocks
The Smithsonian sample was developed in JPL earlier on and had 3 times the density of air; current samples are less dense than air, some as low as 43% of the density of air. (But these technically aren't 'aerogels' because they are composed of nanotubes and not a dendritic lattice with evenly spaced pores) Aerogel can be structurally very diverse, consisting of 99.9% air.
It is constructed by surrounding the material mass with an impermeable film and flooding it with light gases like hydrogen and helium, or pump out the air in the material to create vacuums within the structures.
Structurally aerogels are very porous and either are crosslinked polymers all looped together or dendritic polymers branching outwards.
Aerogels can easily shatter (friable) but are incredibly strong structurally and can support up to 1000 times their weight. Since they are so light, this is still less than an atmosphere which is why squeezing it will shatter the cube.
The yawho? article really a distinction between monolithic aerogels and carbon nanotube aerogels (what the article means by an Eiffel tower structure). The stronger, less dense aerogels are made of carbon nanotubes so the lattice structure is more organized than dendritic aerogel, which is weaker by virtue of its random structure.
P.S read the image tag in the article! Caltech worked to develop this new model
P.P.S as best as I could understand it by monolithic structure purists mean aerogel has a singular dendritic structure, while the nanotube structures consist of multiple carbon cylinders woven together. In this case, aerogel is 'cut' off a single stone of chemical building material
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