The novel reinforced graphene foam could be formed into a screw shape. Photo: Tour Group/Rice University.
The novel reinforced graphene foam could be formed into a screw shape. Photo: Tour Group/Rice University.

A chunk of conductive graphene foam reinforced by carbon nanotubes can support more than 3000 times its own weight and easily bounce back to its original height, according to scientists at Rice University. Better yet, the reinforced foam can be made into just about any shape and size, with the scientists demonstrating this ability by fabricating a screw-shaped piece.

The Rice lab of chemist James Tour also tested its new ‘rebar graphene’ as a highly porous, conductive electrode in lithium ion capacitors, and found it to be mechanically and chemically stable. This research is described in a paper in ACS Applied Materials and Interfaces.

Carbon in the form of atom-thin graphene is among the strongest materials known and is highly conductive, while 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 and so decided to try extending the concept to macroscale materials.

"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 three-dimensional structures were made using a powdered nickel catalyst, surfactant-wrapped multiwall carbon nanotubes and sugar as a carbon source. These 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 that the method should be easy to scale up.

Electron microscope images of the foam showed partially unzipped outer layers of the nanotubes had bonded to the graphene, which accounted for its strength and resilience. Graphene foam produced without the rebar could support only about 150 times its own weight while retaining the ability to rapidly return to its full height. Whereas the rebar graphene irreversibly deformed by only around 25% when loaded with more than 8500 times its weight.

This story is adapted from material from Rice University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.