Scientists develop strong and flexible graphene material

Rice University scientists have developed a new “rebar graphene” material that offers both extreme strength and flexibility.

This macroscale piece of rebar graphene was formed into a screw shape. Photo courtesy of Tour Group/Rice University.

The Rice lab of chemist James Tour developed a chunk of conductive graphene foam that is reinforced by carbon nanotubes. This material can support over 3,000 times its own weight while easily bouncing back to its original height.

The scientists also report that the material can be made into any shape and size and were able to demonstrate this by forming a screw-shaped piece of highly conductive foam. The team tested its new “rebar graphene” as a highly porous, conductive electrode in lithium ion capacitors and found it to be mechanically and chemically stable.

Carbon in the form of atom-thin graphene is among the strongest materials known and is highly conductive; multiwalled carbon nanotubes are widely used as conductive reinforcements in metals, polymers and carbon matrix composites. The Tour lab had already used nanotubes to reinforce two-dimensional sheets of graphene.

“We developed graphene foam, but it wasn’t tough enough for the kind of applications we had in mind, so using carbon nanotubes to reinforce it was a natural next step,” Tour said.

The 3D structures were created from a powdered nickel catalyst, surfactant-wrapped multiwall nanotubes and sugar as a carbon source. The materials were mixed and the water evaporated; the resulting pellets were pressed into a steel die and then heated in a chemical vapor deposition furnace, which turned the available carbon into graphene.

After further processing to remove remnants of nickel, the result was an all-carbon foam in the shape of the die, in this case a screw. Tour said the method will be easy to scale up.

Graphene foam invented at Rice University is reinforced with carbon nanotubes. It can hold thousands of times its own weight and still bounce back to its full height. (Credit: Tour Group/Rice University)

Graphene produced without the rebar could support only about 150 times its own weight while retaining the ability to rapidly return to its full height. But rebar graphene irreversibly deformed by about 25 percent when loaded with more than 8,500 times its weight.

The research appears in the American Chemical Society journal ACS Applied Materials and Interfaces.

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