May 12, 2009 in Manufacturing, Other Technology

Scientists from China and the United States believe they have discovered a new carbon material that is tough enough to crack diamond.

Yanming Ma of Jilin University in Changchun, China, and his colleagues believe that the new carbon material they theoretically model in the current volume of Physical Review Letters may already have been created in a 2003 laboratory experiment.

Working with a team of scientists in 2003, a co-author on the current work, Ho-kwang Mao of the Carnegie Institution in Washington, D.C., found that when he squeezed graphite in a diamond-toothed press, it formed a new material hard enough to crack the teeth of the press. But the original study, published in the journal Science (Mao, et al. 2003), did not theoretically explore the molecular make-up of the new carbon, which Ma and his team have named M-carbon.

Ma and his colleagues use a metric called bulk modulus — a measurement which describes a substance’s resistance to being uniformly squeezed. They say the new carbon is somewhere between graphite and diamonds on the spectrum of hardness (graphite being the softest and diamonds being the hardest) but that it is as hard as diamond when put under tremendous pressure. When the new carbon is not under pressure, it loses its remarkable hardness.

But some scientists argue that the more important metric of hardness is shear strength, not bulk modulus. Neil Ashcroft, a theoretical physicist at Cornell University, tells NatureNews “They [Ma, et al.] don’t present any direct information on the shear strength of their proposed new phase of carbon.”

But Ma and others maintain that a material that becomes ultra-hard only when squeezed might be useful in high-pressure gaskets and other applications that require the dynamic properties M-carbon can offer.

http://cleantechnica.com/2009/05/12/scientists-discover-new-carbon-material-as-hard-as-diamond/