A new process for making carbon fibers from graphene oxide promises to be a scalable, organic-solvent-free route to new kinds of strong, lightweight materials (ACS Nano 2014, DOI: 10.1021/nn501098d). Unlike conventional carbon fibers, these graphene oxide fibers can be knotted and knitted, with potential applications in energy-storing textiles, novel optical materials, and wearable electronics.

Conventional carbon fiber is made by spinning a polymer solution, typically polyacrylonitrile, into thin fibers and then carbonizing the material. The resulting fibers often end up in lightweight, strong structural composites in which the fibers are held together by polymer glue, in a similar fashion to papier-mâché.

Some materials scientists want to make carbon fibers out of nanomaterials, such as graphene and carbon nanotubes. Unlike conventional carbon fibers, these nanomaterial fibers are flexible enough to coil and knot without breaking, so it might be possible to fashion them into knotted or knitted textiles, says Mauricio Terrones of Pennsylvania State University.

Terrones and his team made the fibers by first coating a large surface with an aqueous solution of graphene oxide and letting the water evaporate. Then by taping down one end of the dried film and attaching an electric screwdriver to the other end, they spun the sheet into yarn. Terrones adds that the graphene oxide fibers can be reduced to graphene after spinning.

[+]Enlarge Credit: ACS Nano

Graphene oxide yarns made with this method are tough, withstanding forces as strong as 17 J/g, in the range of what conventional carbon fiber can handle. They’re also stretchy, elongating 76% before fracturing. Those with the best properties were about 300 μm in diameter and made from graphene oxide films about 5 μm thick.

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