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Hybrid graphene material promises to ease manufacturing

Posted: 08 Apr 2014 ?? ?Print Version ?Bookmark and Share

Keywords:Rice University? manufacturing? graphene? carbon nanotube?

A recent discovery at Rice University has pointed the way to a potentially easier way to handle graphene with respect to manufacturing. Carbon nanotubes are reinforcing bars that make 2D graphene much easier to handle in a new hybrid material grown by researchers at Rice University. James Tour, chemist at Rice Labs, set nanotubes into graphene in a way that not only mimics how steel rebar is used in concrete but also preserves and even improves the electrical and mechanical qualities of both.

The technique should make large, flexible, conductive and transparent sheets of graphene much easier to manipulate, which should be of interest to electronics manufacturers, Tour said. He suggested the new hybrid could, upon stacking in a few layers, be a cost-effective replacement for expensive indium tin oxide (ITO) that is being used in displays and solar cells.

Graphene, a single-layer matrix of carbon atoms, may be one of the strongest materials on the planet, but it can be a challenge to lift the tiny sheets from the catalyst substrate on which they're grown, generally by chemical vapour deposition (CVD), Tour said.

"Normally you grow graphene on a metal, but you can't just dissolve away the metal," Tour said. "You put a polymer on top of the graphene to reinforce it, and then dissolve the metal."

"Then you have polymer stuck to the graphene. When you dissolve the polymer, you're left with residues, trace impurities that limit graphene's effectiveness for high-speed electronics and biological devices. By taking away the polymer support step, we greatly expand the potential for this material."

To create what they call rebar graphene, the researchers simply spin-coat and then heat and cool functionalised single- or multiwalled carbon nanotubes on copper foils, using the nanotubes themselves as the carbon source. When heated, the functional carbon groups decompose and form graphene, while the nanotubes partially split and form covalent junctions with the new graphene layer.

Rebar graphene

Graphene transferred from its metal substrate with a polymer coating, left, shows polymer residues (dark spots) remain stuck to the graphene after processing. The rebar graphene, right, created at Rice University is created without the need for a polymer transfer step and stays clean. (Credit: Tour Group/Rice University)

"The nanotubes actually become one with the material in certain places," Tour said. "It's a true hybrid with in-plane nanotubes covalently bonded to graphene."

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