UNC-CH Study Shows Carbon Nanotubes Display Remarkable Strength, Flexibility

October 08, 1997

By DAVID WILLIAMSON
UNC-CH News Services


CHAPEL HILL -- Carbon tubes so thin it would take several million lying side by side to cover an inch show such remarkable flexibility, strength and resiliency that industry should be able to incorporate them into high performance sports and aerospace materials, according to new experiments. Many other products also could be made stronger and possibly safer, scientists believe.

The research, conducted at the University of North Carolina at Chapel Hill, for the first time used a unique computer-linked microscope to bend and record properties of carbon nanotubes.

Researchers create the materials -- a form of soot -- by arcing electricity between two sticks of carbon. About six years ago, Japanese scientist Sumio Iijima discovered the tiny tubes, which are proving to be stiffer and stronger than any other known substance.

"Carbon nanotubes are a new material that scientists around the world have been studying intensively," said Michael R. Falvo of UNC-CH. "What we have found is that under large strains, they have the extraordinary property of being one of the stiffest materials known, while also being able to bend without breaking and then be bent back into their original shape. This is unique."

Falvo is a doctoral student working under the direction of Dr. Richard Superfine, assistant professor of physics and astronomy.

A report on the research appears as the cover story in Thursday's issue (Oct 9) of the journal Nature. Besides Falvo and Superfine, authors of the report are graduate student Gregory J. Clary; Russell M. Taylor II, research assistant professor of computer science; Vernon Chi, director of the microelectronics systems laboratory; Dr. Frederick P. Brooks Jr., Kenan professor of computer science; and Dr. Sean Washburn, professor of physics and astronomy.

The UNC-CH scientists used a device they invented and called the nanoManipulator to bend the nanotubes, which are extremely light, and then measure the curvature of the bends. They also studied the tubes' buckling behavior -- whether or not they buckled under pressure like drinking straws in a child's hands and stayed bent and damaged.

"We found that most of the bending was reversible, and that's exciting because it was not known before," Falvo said. "Even after repeated bending and straightening of the nanotubes, they did not break. In fact, we have never observed a tube fail after repeated bending."

The unique nanoManipulator combines a commercially available atomic force microscope with a force-feedback virtual reality system. The former employs an atomically small probe capable of bending and otherwise manipulating molecule-sized particles. The latter allows the scientists to see and feel a representation of the surface a million times bigger than its actual size.

Carbon fibers already are used in graphite composite tennis rackets and other products because of their strength and lightness, Falvo said. The UNC-CH experiments indicate that carbon nanotubes are significantly stronger than carbon fibers and hundreds of times stronger than steel.

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Note: Falvo and Superfine can be reached at (919) 962-3526 and 962-1185, respectively.

Contact: David Williamson

University of North Carolina at Chapel Hill

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