A Lighter-Than-Air Building Material

Courtesy TUHH

This summer, as Olympic athletes go faster, higher, and stronger in London, a record has fallen in a lab in Hamburg: Scientists have created the world’s lightest material. The new carbon nanomaterial, called Aerographite, weighs 0.2 milligrams per cubic centimeter. That’s less than a quarter the weight of the last record-holder, a nickel-phosphorous microlattice created by American researchers last year. And it’s six times lighter than air.

Nanotechnology researchers have been working with carbon nanotubes for years (as the name suggests, these are very, very small tubes made of carbon atoms), building everything from superlight bicycles to medical implants. What the German team (from the University of Hamburg and the University of Kiel) figured out was how to build a network of branching nanotubules, thereby making the material stronger and a better conductor of electricity—two qualities that make it much more widely useful in electronics. The unprecedented lightness was an unexpected bonus.

Courtesy TUHH

Aerographite was created by a clever molecular-scale version of the lost-wax process: Carbon gas was pumped into a furnace, where it coated a lattice of zinc oxide molecules (think of Dairy Queen hard-shell coating soft-serve ice cream). Then hydrogen gas was pumped into the furnace, bonding with the oxygen in the zinc oxide to form water, which evaporated, and leaving the zinc to in turn evaporate as gas. What was left was a hollow interconnected web of carbon tubes.

Aerographite has a foam-like consistency, so it’s hard to imagine building Formula One race cars or fighter jets out of it. Because of its extraordinary lightness and strength, though, as well as its compressibility (it can be squashed down by 95 percent without any damage) and ability to conduct electricity, its creators believe it can be used to create better batteries and other electrical components like supercapacitors. Using Aerographite would remove weight, of course, but, more important for power sources, could add energy—the anodes in batteries work by storing electrons, and all of the tiny pores in Aerographite are spaces for electrons to become embedded.

A cubic centimeter of Aerographite is 99.99 percent air, and perhaps the weirdest thing about it is that all that air actually makes the material heavier. Normally, things are light because they’re airy—as in Styrofoam or cotton candy. Not so with Aerographite, whose carbon nanotubes are actually less dense than the molecules in a cubic centimeter of air (six times less, as you’ll recall). The air in Aerographite weighs it own. Suck it out somehow, and the stuff would just lift off the table like a helium balloon.

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