|A 3D model of a graphene nanotube. / Photo by: Eugene Sergeev via 123RF|
While graphene possesses strength greater than steel, its thin size has some consequences. To address this issue, researchers at Rice University applied reinforced bars to embed fracture resistance in graphene material.
Graphene is a material composed of an atom-thick sheet of carbon. Despite its exceptional thinness, it displays higher strength than most materials. However, a sufficient amount of stress can rip and tear the tiny size of graphene which often results in total breakage.
At Rice University, application of reinforced bars can improve the durability of graphene material, similar to embedded steel bars in concrete.
The research team used carbon nanotubes to act as reinforced bars of graphene. The carbon nanotubes were made from single-walled nanotubes spin-coated onto a copper substrate. To make the rebar graphene, the graphene was grown on top of the nanotubes using the chemical vapor deposition process.
To test the amount of stress that rebar graphene can handle, the team had to pull it to pieces and measure the applied force. They cut the microscopic pieces of the material and mounted it on a testbed, equipped with scanning electron and transmission electron microscopes, then applied conducted stress tests.
“We couldn’t use glue, so we had to understand the intermolecular forces between the material and our testing devices. With materials this fragile, it’s really difficult,” said Emily Hacopian, lead author of the study.
While rebar cannot keep graphene completely free from fractures, it managed to slow down the ripping and tearing process. The carbon nanotubes acted as bridges to keep the material from being entirely broken by force.
At the same time, the nanotubes sustained the conductivity of graphene, even if the material was under stress. Finally, the rebar helped the material to remain stretchy, a useful trait needed in manufacturing graphene-based flexible electronics and wearable devices.
“We hope this opens a direction people can pursue to engineer 2D material features for applications,” Lou added.