Graphene is a flat hexagonal lattice of carbon atoms, just one atom thick. It is a form of carbon related to carbon nanotubes and buckyballs (C60). Although it has always occurred naturally, it is only recently that it has been isolated and it’s individual properties examined. It is now known that graphene has exceptional electrical, structural and chemical properties, leading to it being heralded as a wonder-material with many future applications. However, for a number of reasons, most of this potential is currently not realized.
Individual sheets of graphene have extremely high strength, almost 20 times that of the strongest carbon fibres, leading to speculation that it may be possible to realize this strength in bulk materials. However, graphene already occurs naturally in common forms of carbon. The graphite used in pencils consists of flat layers of graphene; these smooth layers can easily slide past one another, giving the material its softness.
The graphite used in carbon fibre composites is also made up of layers of graphene, but in this form the graphene sheets are crumpled, causing them to lock together giving the material high strength and stiffness. In both of these examples, it is the connections between the sheets of graphene, rather than the properties of the graphene sheets themselves, which determines the strength of the bulk material. If the extremely high theoretical strength of graphene is to be realized, some way of forming strong interconnections between sheets will be required.
Graphene is closely related to Buckminsterfullerene, also known as buckyballs or C60. C60 has a similar structure to graphene but some of the hexagons are reduced to pentagons. This causes the lattice to curve into a sphere with a very similar structure to a football. Since C60 was discovered in 1985, many other hollow molecules have been created with combinations of rings containing five, six and sometimes seven carbon atoms. These materials are generically known as Fullerenes and include carbon nanotubes (CNT). CNTs are basically tubes of graphene rolled into a hollow cylinder. Different diameters of CNT can be formed into multi-walled tubes and groups naturally form bundles similar to rope.
Some potential uses for graphene and carbon nanotubes include stronger and lighter structures, more efficient electrical systems, low-cost solar cells, desalination and hydrogen fuel cells. The applications for C60 are somewhat more limited, with great potential as a lubricant and also possible uses as a catalyst and in the delivery of pharmaceuticals within the body.
