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Posted: Jul 14, 2016
'Rivet graphene' proves its mettle
(Nanowerk News) Nanoscale "rivets" give graphene qualities that may speed the wonder material's adoption in products like flexible, transparent electronics, according to researchers at Rice University.
The Rice lab of chemist James Tour reported the creation of "rivet graphene," two-dimensional carbon that incorporates carbon nanotubes for strength and carbon spheres that encase iron nanoparticles, which enhance both the material's portability and its electronic properties.
The material is the subject of a paper in the American Chemical Society journal ACS Nano ("Rivet Graphene").
A single “rivet,” a carbon-wrapped nanoparticle of iron, attached to graphene that has been reinforced by an interconnected web of carbon nanotubes, which are also visible in this transmission electron microscope image. (Image: Tour Group)
Until now, researchers have had to transfer graphene grown via chemical vapor deposition with a polymer layer to keep it from wrinkling or ripping. But the polymer tended to leave contaminants behind and degrade graphene's abilities to carry a current.
"Rivet graphene proved tough enough to eliminate the intermediate polymer step," Tour said. "Also, the rivets make interfacing with electrodes far better compared with normal graphene's interface, since the junctions are more electrically efficient.
"Finally, the nanotubes give the graphene an overall higher conductivity. So if you want to use graphene in electronic devices, this is an all-around superior material," he said.
Tests proved rivet graphene retained the strength of the Tour lab's rebar graphene (which incorporates nanotube reinforcement) as well as rebar's ability to float on water. But the rivets also enhanced the material's ability to transfer current between electrodes and the graphene, even when bent, the researchers reported.
The rivets are layers of carbon wrapped around a 30-nanometer iron core, dubbed "nano-onions" by the lab. The structures are grown in place in the CVD furnace after the dispersal of nanotubes and deposition of graphene. A final step welds all the elements together, Tour said.
Rivet graphene is transparent enough for flexible and transparent electronics, he said, and the simplified process should be scalable.