Scientists Turn Graphite into Graphene

Researchers have developed a way to turn graphite into graphene, one-atom-thick sheets of carbon that can be mixed into other materials such as glass and ceramics to manipulate properties such as strength and thermal conductivity.

The method, developed at Northwestern University, produces individual graphene-based sheets with exceptional physical, chemical and barrier properties that could be mixed into materials such as polymers and ceramics. The Northwestern team, led by materials scientist and physical chemist Rod Ruoff and composed of chemists, physicists and engineers, reports the results of their research in the July 20 issue of the journal Nature.

“This research provides a basis for developing a new class of composite materials for many applications, through tuning of their electrical and thermal conductivity, their mechanical stiffness, toughness and strength, and their permeability to flow of various gases through them,” said Ruoff, professor of mechanical engineering in Northwestern's McCormick School of Engineering and Applied Science. “We believe that manipulating the chemical and physical properties of individual graphene-based sheets and effectively mixing them into other materials will lead to discoveries of new materials in the future.”

The Northwestern team's approach to its challenge was based on chemically treating and thereby “exfoliating” graphite to individual layers. Graphite is a layered material of carbon with strong chemical bonds in the layers but with moderately weak bonds between the layers. The properties of the individual layers have been expected to be exceptional because the “in-plane” properties of graphite itself are exceptional, but until now it was not possible to extract such individual layers and to embed them as a filler material in materials such as polymers, and particularly not by a scalable route that could yield large quantities.

There are approximately one million metric tons of graphite sold annually around the world, and there are roughly 800 million metric tons of untapped natural graphite that could be mined and used in the future, according to the US Geological Survey. Graphite is used in a wide variety of applications such as those related to friction (brake linings are one example), in gaskets, as a lubricant and as an electrode material in steelmaking.

Ruoff has worked and published extensively on other novel carbon materials such as fullerenes (“buckyballs”) and carbon nanotubes. His Northwestern research team included SonBinh Nguyen, professor of chemistry; chemist and postdoctoral fellow Sasha Stankovich; physicist and research assistant professor Dmitry Dikin; physicist and research scientist Richard Piner; and graduate students Eric Zimney, Geoffrey Dommett and Kevin Kohlhaas. Professor Eric Stach of Purdue University helped analyze transmission electron microscopy images acquired by the Northwestern team.

For more information, visit: www.northwestern.edu