Diamonds have been usurped as the world's hardest material, thanks to researchers in Germany, who have made a new material by compressing carbon-60 molecules. They have dubbed their new form of carbon "aggregated diamond nanorods".

The University of Bayreuth team, led by Natalia Dubrovinskaia, have patented their breakthrough, which they expect will have many applications in industry.

A material's hardness is measured in terms of its 'isothermal bulk modulus' - that is to say, how a solid's volume changes as pressure is applied, at a constant temperature. Diamond has a modulus of 442 gigapascals, but the new material has a modulus of 491 gigapascals.

The new material is created by subjecting carbon-60 to 200 times atmospheric pressure, while heating to 2500 Kelvin, the researchers say. This creates the aggregated diamond nanorods - so called because the material is made of interlocking diamond rods, each around one micron long, and having a diameter of between five and 20nm.

The scientists, who are now looking for partners to commercialise their discovery, say more work is needed to determine exactly why this new material is so tough.

The research was published in Applied Physics Letters. ®