GRAPHENE

Description of Graphene



Graphene is a substance composed of pure carbon, with atoms arranged in a regular hexagonal pattern similar to graphite, but in a one-atom thick sheet. It is very light, with a 1-square-meter sheet weighing only 0.77 milligrams.

It is an allotrope of carbon whose structure is a single planar sheet of sp2-bonded carbon atoms, that are densely packed in a honeycomb crystal lattice. The term graphene was coined as a combination of graphite and the suffix -ene by Hanns-Peter Boehm, who described single-layer carbon foils in 1962. The crystalline or form of graphite consists of many graphene sheets stacked together.


Crystallography of Graphene




An ideal crystal is formed by an infinite repetition of identical groups of atoms. Each group of atoms, called the basis, is attached to a point on a periodic array called the lattice.

The carbon-carbon bond length in graphene is about 0.142 nanometers.Graphene sheets stack to form graphite with an interplanar spacing of 0.335 nm.

In the case of ideal graphene, a two atom basis is attached to a hexagonal lattice and the result is a two dimensional honeycomb crystal.

Graphene Properties



In 3D space, the bonding between carbon atoms is sigma. In other words, such electrons direct their charges along the bonds within the graphene sheet, itself- whereas the remaining available electron - one for each atom - lies in the z- or third dimension, above and below the graphene sheet. Such electrons are called pi electrons, and are highly mobile. Mobile electrons, put into motion, are electricity. In fact, graphene electron orbitals overlap and unite to form a "conduction band".

In addition to its exceptional electrical conductivity, graphene is the strongest known substance. By creating holes within a sheet of graphene, then "doping" those holes with desired impurities, semiconductors can be made that are nearly unbreakable and highly flexible.

As a bonus, graphene is a superb heat conducting material, so heat would not be the problem it is with current semiconductor materials.

Some Important Properties:

  • ~1100 GPa modulus, fracture strength ~130 GPa
  • Low density ~2 g/cm3.
  • Thermal conductivity ~3000 W/m-K in plane - but highly anisotropic: ~ 2 W/m-K out of plane.
  • Electrical conductivity: ballistic electron transfer; high mobility.
  • Physical properties can be 'chemically tuned'

    Optional Graphene Applications



  • Transparent electric conduction. Can you imagine heating your windshield with graphene fabric?
  • Structural devices such as turbine blades
  • Electrical energy storage
  • Catalyst support
  • Ppaper-like composites.
  • Others suggest graphene would be ideal for terahertz electronics (ultra-high frequency, requiring small dimensions) devices

    Back to top...