One atom thick, graphene is one of the strongest materials ever measured, and it carries electricity and heat very well.
In 2008, engineers at Columbia University in New York stretched tiny flakes of graphene over holes and pressed on them with a diamond-tipped probe until they tore. A perfect sheet could bear about 200 times the pull, for its thickness, that tears structural steel, the steel in buildings and bridges. It was the strongest material anyone had measured.
Why it is so strong
Every carbon atom in the sheet is held by 3 strong bonds, and the bonds join into one network that runs across the whole sheet. To tear it, you have to break bond after bond all along the tear. The shared electrons add to every bond, so each bond is shorter than a C–C single bond, almost as short as the bonds in benzene's ring, and between the same two atoms a shorter bond is a stronger one.
Graphite feels soft and slippery because its sheets slide over each other, held together only by a weak pull. Each sheet on its own is held by these strong bonds.
Why it conducts
The spare electrons shared across the sheet are free to move. Connect a battery and they flow through the sheet as an electric current, the same reason graphite conducts. Electrons travel through graphene more easily than through silicon, the material of computer chips. Graphene also carries heat better than copper, and a single sheet absorbs only about 2.3% of the light that falls on it, so it is almost transparent.
| Property | Value |
|---|---|
| thickness | one atom (0.34 nm) |
| bond length | 0.142 nm |
| mass of 1 m² | 0.77 mg |
| breaking strength | about 200 times structural steel |
| light absorbed | about 2.3% |