28 August 2013

Graphene aerogel is seven times lighter than air, can balance on a blade of grass

Chinese material scientists have created the world’s lightest material: A graphene aerogel that is seven times lighter than air, and 12% lighter than the previous record holder (aerographite). A cubic centimeter of the graphene aerogel weighs just 0.16 milligrams — or, if you’re having a problem conceptualizing that, a cubic meter weighs just 160 grams (5.6 ounces). The graphene aerogel is so light that an cube inch of the stuff can be balanced on a blade of grass, the stamen of a flower, or the fluffy seed head of a dandelion (see pictures below).

Most aerogels are produced using a sol-gel process, where a gel is dehydrated until only the aerogel remains. Some aerogels are also produced using the template  method — aerographite, for example, is created by growing carbon on a lattice (template) of zinc oxide crystals — and then the zinc oxide is removed in an oven, leaving just the carbon aerogel. To create the graphene aerogel, however, researchers at Zhejiang University use a novel freeze-drying method. Basically, it seems like the researchers  create a solution of graphene and carbon nanotubes, pour it into a mold, and then freeze dry it. Freeze drying dehydrates the solution, leaving single-atom-thick layers of graphene, supported by carbon nanotubes. The researchers say that there’s no limit to the size of the container: You could make a mini graphene aerogel using this process, or a meter-cubed aerogel if you wish.
Graphene aerogel, propped up on the stamen of a flower. The cube, which is roughly an inch across, probably weighs less than 5 milligrams.

The end result is an aerogel that weighs just 0.16 milligrams per cubic centimeter, and has truly superb elasticity and absorption. The graphene aerogel can recover completely after more than 90% compression, and absorb up to 900 times its own weight in oil, at a rate of 68.8 grams per second. With these two features combined, lead researcher Gao Chao hopes that the material might be used to mop up oil spills, squeezed to reclaim the oil, and then thrown back in the ocean to mop up more oil. Beyond filtration, graphene aerogel might be used as insulation — or, if it’s as conductive as aerographite (which seems likely), graphene aerogel could enable the creation of lighter, higher-energy-density batteries.

Over the next few pages we’ve compiled some amazing photos of aerogels. Click through if you want to see lumps of carbon balancing on a blade of grass, centimeter-thick slabs of aerogel that can insulate against the blue flame of a Bunsen burner,  or a two-gram piece of aerogel that can hold up a 2.5-kilogram brick,

 The Chinese graphene aerogel, sitting on top of a plant’s leaves

 The graphene aerogel, balancing on the petals of a flower.

Another shot of the graphene aerogel, balanced on the spine of a plant.

A metallic microlattice, which has many of the same features of an aerogel, balancing on a dandelion seed head.

A 2.5-kilo brick, perched atop a 2-gram block of silica aerogel

NASA scientist Peter Tsou, holding an aerogel cube

A slab of silica aerogel, insulating some crayons against a Bunsen burner

Now read: Carbyne - A new form of carbon that’s stronger than graphene

Research paper: DOI: 10.1002/adma.201204530 – “Ultralight and Highly Compressible Graphene Aerogels”


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