Density functional-based tight-binding modelling. Credit: http://www.nature.com/ncomms/2015/150820/ncomms9029/full/ncomms9029.html
>>inherent defects give rise to a surprising mechanical property caused by an unusual mechanochemical reaction.What they discovered could potentially unlock the secret to successfully scaling up graphene oxide. “Our team discovered that graphene oxide exhibits remarkable plastic deformation before breaking,” said Espinosa. “Graphene is very strong, but it can break suddenly. We found that graphene oxide, however, will deform first before eventually breaking.”
Huang compares the difference in the materials’ properties to common objects. “Ceramic is strong,” he says, “but if you break it, it will shatter. Now if a plastic cup is squeezed, it will bend before it snaps.”
The team found that graphene oxide’s plasticity is due to an unusual mechanochemical reaction. Graphene oxide comprises 2 C atoms and 1 O atom, a formation known as an epoxide. When an epoxide’s bonds are chemically broken, the carbon-oxygen bonds break, leaving the carbon-carbon bond in tact. The research team, however, found that when a mechanical force was applied to graphene oxide, the carbon-carbon bond broke first, leaving the carbon-oxygen bonds in place.
“We uncovered this surprise on the atomic scale,” Nguyen said. “This is completely different than what occurs in other materials and a very unusual property for the graphene oxide sheet.” The Northwestern team is now extending its research to understanding the mechanical properties of graphene oxide-polymer interfaces, which is critical to scaling up the material.
“With more information obtained at different length scales as well as advances in synthesis methods, we will eventually piece the puzzle together.” http://www.mccormick.northwestern.edu/news/articles/2015/08/graphene-oxides-secret-properties-revealed-at-atomic-level.html
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