Researchers at Rice University in Houston, Texas have found that fracture-resistant "rebar graphene" is more than twice as tough as pristine graphene, something which could help in the development for flexible electronics of the future.
Regular graphene, which is a one-atom-thick sheet of carbon, is stronger than steel, but because it's so thin, it is still subject to ripping and tearing.
Rebar graphene was developed in the Rice lab of chemist James Tour in 2014. It is so-called because the principel is the same as the rebar (reinforcement bars) used in the construction industry, where steel bars are embedded in concrete to enhance the material's strength and durability. Rebar graphene uses carbon nanotubes for reinforcement.
However, according to the Rice scientists' new report - published in the American Chemical Society journal ACS Nano - fresh experiments have shown that the addition of nanotubes can help graphene stay 'stretchy' and also reduce the effects of cracks. This is because nanotube rebar diverts and bridges cracks that would otherwise propagate in unreinforced graphene.
This, the researchers claim, could be useful not only for flexible electronics of the future but also for electrically active wearables or other devices where stress tolerance, flexibility, transparency and mechanical stability are desired.
The study was led by Rice materials scientist Jun Lou, alongside graduate student and lead author Emily Hacopian and other collaborators, including Tour.
To stress-test rebar graphene, the team had to pull it to pieces and measure the force that was applied. Through trial and error, the lab developed a way to cut microscopic pieces of the material and mount it on a test bed for use with scanning electron and transmission electron microscopes.
"We couldn't use glue, so we had to understand the inter-molecular forces between the material and our testing devices," Hacopian said. "With materials this fragile, it's really difficult."
Rebar didn't keep graphene from ultimate failure, but the nanotubes slowed the process of decay by forcing cracks to zig and zag as they propagated. When the force was too weak to completely break the graphene, nanotubes effectively bridged cracks and in some cases preserved the material's conductivity.
Lou added that the rebar graphene results are a first step toward the characterisation of many new materials.
"We hope this opens a direction people can pursue to engineer 2D material features for applications," he said.
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