Wafer-thin paper beats bucky tubes
Wafer-thin carbon paper said to be stronger, lighter and more flexible than the equivalent made from nanotubes has been developed in the US.
The paper is made from graphene oxide, which is derived from the cheap and plentiful form of carbon, graphite.
First, scientists oxidised graphite to form graphite oxide, a layered material, which sheds layers of graphene oxide in water.
They then filtered the sheets and formed them into neatly-structured layers, each a micrometre, or a millionth of a metre, thick.
The researchers have made small sheets of the dark-brown paper 1-100 micrometres thick and tested it successfully for stress and tensile resilience against other papers.
This includes so-called bucky paper, which is made of carbon nanotubes.
Graphene oxide paper owes its physical qualities to a unique interlocking-tile lattice at the atomic scale.
It also has intriguing electrical qualities, as the oxidisation process turns the material from a conductor into an insulator.
"In the future, it will be possible to tune the material as a conductor, semiconductor or insulator," Ruoff says. "One will be able to control the electrical properties without sacrificing exceptional mechanical properties."
The foil-like paper has many potential outlets, the scientists say.
It could be used alone or as a composite with plastics, ceramics or metals where flexible reinforcement is needed, such as in aircraft, cars and buildings.
It could also be used in batteries and supercapacitors, while its unique lattice structure could be electrically charged to make membranes with controllable permeability.
So far, only experimental sheets of the paper have been made, each of them around 12 centimetres in diameter.
But Ruoff believes that it would be quite easy to scale up to large sheets, helped by the fact that graphite is cheap and plentiful.
Ruoff's team is a pioneer in a new class of material called graphene, a sheet of carbon only one atom thick.
"The mechanical, thermal, optical and electrical properties of graphene are exceptional," says Ruoff.
"For example, the stiffness and strength of these grapheme-like sheets should be superior to all other materials, with the possible exception of diamond."