A light-absorbing midnight-black substance dubbed Aerographite has stolen the crown for the lightest material in the world, weighing just 0.2mg per cubic centimetre. And because of its special properties, it's a serious contender to build lithium-ion batteries small and light enough to power the electronic bikes and cars of the future.
Boffins in Germany constructed the new material by weaving together a network of porous carbon tubes at nano and micro level to create the stuff that is 75 times lighter than Styrofoam.
"Think of the Aerographite as an ivy-web, which winds itself around a tree. And then take away the tree," said Prof Rainer Adelung of Kiel Uni.
The previous record-holder for lightest-ever stuff was also made of nanotubes – but those weren't porous, and were made of nickel rather than carbon, which made the material heavier. “The hitherto lightest material of the world, a nickel material that was presented to the public about six months ago, is also constructed of tiny tubes. Only, nickel has a higher atomic mass than carbon. Also, we are able to produce tubes with porous walls. That makes them extremely light," said co-author Arnim Schuchard, a PhD student at Kiel University.
Adelung and other researchers from Kiel Uni and the Hamburg University of Technology (TUHH) worked together to make the substance using a powdered zinc oxide.
The boffins heated the zinc oxide up to 900°C to transform it into a crystalline structure. From that stuff, the scientists made a kind of pill, inside which the zinc oxide had formed micro and nano structures called tetrapods... so the "pill" is actually porous.
The pill was then stuffed into a reactor for chemical vapour deposition and cooked up to 760°C to lay on a few coats of graphite.
"In a streaming gas atmosphere that is enriched with carbon, the zinc oxide is being equipped with a graphite coating of only a few atomic layers," Schuchard explained, "This forms the tangled-web structures of the Aerographite. Simultaneously, hydrogen is introduced. It reacts with the oxygen in the zinc oxide and results in the emission of steam and zinc gas.
"The faster we get the zinc out, the more porous the tube's walls get and the lighter the material. There is considerable scope."
The stuff the boffins end up absorbs light rays almost completely so it is jet-black, it stays stable and is conductive and ductile. The aerographite is also resilient, withstanding both compression and tension.
The researchers reckon that these characteristics mean the new material could fit into the electrodes of lithium-ion batteries, which could in turn be used in electronic cars or bikes.
Aerographite also has potential for use in aviation and satellite construction because materials used need to be able to put up with a lot of vibration. The stuff could even be used in water purification, where it may act as an absorbent for pollutants. ®