stack of papers

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.

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.

[Physicists make tiniest machines by cutting nano-paper]

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.

Source: Rice University