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Graphene oxide 'paper' changes with strain

Researchers say material is more or less brittle, depending on how hard it's pulled

Date:
January 19, 2016
Source:
Rice University
Summary:
The same slip-and-stick mechanism that leads to earthquakes is at work on the molecular level, where it determines the shear plasticity of nanoscale materials, report scientists. Plasticity is the ability of a material to permanently deform when strained. The 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.
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Graphene oxide layers deform evenly under gentle strain, according to experiments and computer models by Rice University researchers. They discovered that the mechanical properties of the material change, depending on the rate of strain.
Credit: Ajayan Research Group/Rice University

The same slip-and-stick mechanism that leads to earthquakes is at work on the molecular level in nanoscale materials, where it determines the shear plasticity of the materials, according to scientists at Rice University and the State University of Campinas, Brazil.

The Rice lab of materials scientist Pulickel Ajayan found that random molecules scattered within layers of otherwise pristine graphene affect how the layers interact with each other under strain.

Plasticity is the ability of a material to permanently deform when strained. The Rice 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.

Such deep knowledge is important when making novel advanced materials, said Chandra Sekhar Tiwary, a lead author of the new paper in the American Chemical Society journal Nano Letters and a Rice postdoctoral research associate.

"We want to build three-dimensional structures from two-dimensional materials, so this kind of study is useful," he said. "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 said.

"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."


Story Source:

The above post is reprinted from materials provided by Rice University. Note: Content may be edited for style and length.


Journal Reference:

  1. Soumya Vinod, Chandra Sekhar Tiwary, Leonardo D. Machado, Sehmus Ozden, Juny Cho, Preston Shaw, Robert Vajtai, Douglas S. Galvão, Pulickel M. Ajayan. Strain Rate Dependent Shear Plasticity in Graphite Oxide. Nano Letters, 2016; DOI: 10.1021/acs.nanolett.5b04346

Cite This Page:

Rice University. "Graphene oxide 'paper' changes with strain: Researchers say material is more or less brittle, depending on how hard it's pulled." ScienceDaily. ScienceDaily, 19 January 2016. <www.sciencedaily.com/releases/2016/01/160119092822.htm>.
Rice University. (2016, January 19). Graphene oxide 'paper' changes with strain: Researchers say material is more or less brittle, depending on how hard it's pulled. ScienceDaily. Retrieved August 30, 2016 from www.sciencedaily.com/releases/2016/01/160119092822.htm
Rice University. "Graphene oxide 'paper' changes with strain: Researchers say material is more or less brittle, depending on how hard it's pulled." ScienceDaily. www.sciencedaily.com/releases/2016/01/160119092822.htm (accessed August 30, 2016).