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Graphene sheet can be more economical than carbon nanotube for plastic composites

Graphene sheet is a thin film of carbon that is just one atom thick embedded in a polymer matrix. Graphene can be more economical and cost effective than carbon nanotubes for plastic composites. The composite, which conducts electricity, could be used to make new types of microelectronic devices and circuits, and can find use in aircraft and coatings.

Graphene, a novel type of material with good electrical properties - can be made by rubbing tiny pieces of its precursor, graphite, against a hard surface to detach flakes of the carbon material. However, this is not an easy process because the individual sheet tends to clump together. Moreover, graphite, is soft and flaky and so does not have the high mechanical strength of carbon nanotubes.
Rodney Ruoff at Northwestern University in Illinois , USA along with his colleagues has now devised a new technique to overcome these problems. The team found a version of graphite oxide chemically modified with organic compounds, when dipped in solvents and treated with ultrasound waves, dispersed into sheets of oxygenated graphene. From there, researchers then found they could fuse these sheets with commercial polymers such as rubbers or polystyrene and strip the oxygen away to make them electrically conductive graphene. The polymers help keep the graphene from sticking together.
The sheet remains separate because it repels another sheet on account of the oxygen-based chemical groups, which have an excess negative charge. The researchers then "tuned" the surface of the graphite by adding certain chemical groups so that it disperses in solvents routinely used to dissolve polymers. In this way, different polymers can be added to the solvent-graphite oxide mixture to make a composite material. The solvent is eventually removed to leave just the well-dispersed graphene sheet and polymer.

Using electron microscopy, Ruoff and co-workers observed that the polystyrene-graphene composite resembles a block of ice containing pieces of crumpled paper. This new material, which is light but stiff and tough, could be used to make fuselages for aircraft, as well as in electronics and potentially in paints and coatings. Strong, lightweight plastic-like composites made with highly electrically conductive sheets of carbon just one atom thick could find use in electronics and protect aircraft from lightning strikes.

The graphite found in pencils is made of layers just a single carbon atom thick known as graphene. Carbon nanotubes are simply graphene that has been rolled into a cylindrical shape. Investigators worldwide are researching carbon nanotubes for use in electronics because they are capable of conducting electricity at high speed with little energy loss.

Graphene appears to have many electronic properties similar to carbon. Using graphene is very economical as graphite is far less expensive than carbon nanotubes. Electronic properties of their graphene-polystyrene hybrids compare well with the best values reported for nanotube-polymer composites. Moreover, unlike the nanotube-polymer materials, the graphene-polystyrene composites are easy to process using standard industrial processes such as injection molding or hot pressing.

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