How and Why: Graphene seems valuable for computers, batteries and other uses

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Monday, October 25, 2010; 3:56 PM

Nanomaterials rarely burst into the public consciousness. They are, after all, visible only through an electron microscope, a $40,000 luxury most people will never attempt to use. But this year's Nobel Prize for Physics put the spotlight on graphene, a single-layer sheet of carbon molecules with borderline magical properties.

Scientists have been investigating small bits of carbon for a long time. Researchers stumbled upon tiny geodesic carbon spheres in 1985 and named them buckyballs, after gonzo architect and dome meister Buckminster Fuller. Six years later, scientists began experimenting with carbon nanotubes. But the thinnest possible carbon sheets, just a single atom thick, eluded physicists. They lacked the tools to shave a material that thin, and none of their chemical reactions could produce just one layer.

By now, from the Nobel Prize coverage, you may know that Scotch tape came to the rescue. In 2004, two Russian-born scientists at the University of Manchester stuck Scotch tape to a chunk of graphite, then repeatedly peeled it back until they had the tiniest layer possible.

Now that graphene is everyone's favorite nanomaterial, it raises some questions: What is graphene good for, and when is it going to change our lives? A bunch of research centers are working feverishly on the answers.

The first and best-known potential use for graphene is in computer chips. Today's chips rely on silicon, which is a great material because it's cheap and changes its behavior in response to tiny electrical voltages. But we're nearing the limit of its potential. If the speed and power requirements of computers keep increasing, they will push silicon to its melting point.

Graphene's electrons move 100 to 1,000 times faster than those of silicon, meaning less power will be required for the same computing capacity. Such blazing speed might also help produce ever-tinier computing devices with more power than your clunky laptop.

Nongjian Tao, an Arizona State University professor who studies the basic properties of graphene, also foresees graphene-based chemical sensors to detect explosives in luggage and volatile organic compounds in the air. "Graphene allows you to convert a chemical reaction into an electronic signal," he says.

Graphene also flaunts incredible strength and stiffness. In 2008, scientists at Columbia University proved it to be the world's strongest material, pound for pound. To put it into perspective, if you had a sheet of graphene as thick as a piece of cellophane, it would support the weight of a car. If paper were as stiff as graphene, you could hold a 100-yard-long sheet of it at one end without its breaking or bending.

This incredible strength raises all sorts of possibilities. If you took small flakes of graphene and mixed them into other materials, you could use those composites to build far stronger, lighter products - anything from airplanes to tennis racquets.

Graphene might also revolutionize electrical energy storage by vastly improving ultra-capacitors. These are the specialized batteries that can supply huge bursts of energy over a short period.

Ultra-capacitors have lots of uses. Their quick energy surge helps cranes hoist loads, for example. The problem is that existing models just can't store that much energy. Graphene, which could be stacked up to create vast expanses of surface area for electrochemical reactions, might change that.

Hybrid cars are a potential application. When you apply the brakes in your Prius, its special battery captures the energy normally lost as friction between brake pads and wheel. As you accelerate, that battery then releases its energy stores to get the car going again.

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