It weighs less than air, yet withstands punishment from crushing to burning without a scratch and soaks up oil spills better than today’s materials. A new class of materials, carbon nanotube aerogels, is claiming title to the lightest material on Earth and, perhaps one day, among the most useful.
These featherweight materials of atom-thick sheets of carbon, or graphene, are formed when water is extracted from a wet gel and a strong matrix of nanoparticles is left behind. For the last two decades, the focus has been on creating silica or polymer aerogels (NASA used the substance to capture stardust in orbit and insulate the Mars rovers). But carbon nanotubes are opening up a whole new area of muscular applications, say scientists from the University of Pennslyvania (PDF).
While silica aerogels were fragile, carbon versions are pliable, elastic, and robust. Aerogels have emerged in recent years that can be bent, burnt, or squeezed without permanent damage, and that can support 8,000 times their own weight.
The world’s lightest carbon aerogel has reportedly emerged from the laboratory of Gao Chao of Zhejiang University in China, publishing in Advanced Materials. With a density of just 0.16 milligrams per cubic centimeter—a fraction that of air—the carbon aerogel has preserved its robust properties—elasticity and absorbency—while ditching even more of the weight than previous versions. The researchers show their creation perched atop delicate flower blooms without bending a petal. It was made using commercial carbon nanotubes and giant graphene sheets, although by volume the material is about 99.9% empty space.
The potential applications range from electronics to insulation. One of most immediate is absorbing oil spills. Since carbon aerogels are almost all porous spaces, they can absorb up to 900 times their own weight and do it in record time. Conventional materials also require expensive processing to separate out the oil; carbon aerogels can simply be squeezed or even burned, and then reused. For aerogels, what’s not there is almost as important as the stuff that is.