JAN 19, 2016 11:49 PM PST

Pull very fast and graphene paper gets brittle

Plasticity is the ability of a material to permanently deform when strained. Researchers, thinking about future things like flexible electronics, decided to see how graphene oxide “paper” would handle shear strain, in which the sheets are pulled by the ends.

Their tests show that random molecules scattered within layers of otherwise pristine graphene affect how the layers interact with each other under strain.
 
"These structures could be a thermal substrate for electronic devices, they could be filters, they could be sensors, or they could be biomedical devices," says Chandra Sekhar Tiwary. "But if we're going to use a material, we need to understand how it behaves."

Such knowledge is important when making novel advanced materials, says Chandra Sekhar Tiwary, a lead author of the new paper in Nano Letters and a Rice University postdoctoral research associate.
“We want to build three-dimensional structures from two-dimensional materials, so this kind of study is useful,” he says. “These structures could be a thermal substrate for electronic devices, they could be filters, they could be sensors, or they could be biomedical devices.

“But if we’re going to use a material, we need to understand how it behaves.

The graphene oxide paper they tested was a stack of sheets that lay atop each other like pancakes. Oxygen molecules “functionalized” the surfaces, adding roughness to the otherwise atom-thick sheets.

In experiments and computer models, the team found that with gentle, slow stress, the oxides would indeed catch, causing the paper to take on a corrugated form where layers pulled apart. But a higher strain rate makes the material brittle.

“The simulation performed by our collaborators in Brazil provides insight and confirms that if you pull it very fast, the layers don’t interact, and only one layer comes out,” Tiwary says.

“After this study, we now know there are some functional groups that are useful and some that are not. With this understanding we can choose the functional groups to make better structures at the molecular level.”

Other researchers from Rice and the State University of Campinas, Brazil collaborated on the project, which received support from the Department of Defense and Air Force Office of Scientific Research.

This article was originally published on futurity.org.
About the Author
  • Futurity features the latest discoveries by scientists at top research universities in the US, UK, Canada, Europe, Asia, and Australia. The nonprofit site, which launched in 2009, is supported solely by its university partners (listed below) in an effort to share research news directly with the public.
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