Chinese Scientists Develop Tougher Synthetic Diamonds

Diamonds may be a girl's best friend, but they are also prized by oil drillers, road crews and experimental physicists for their unparalleled ability to bore, grind and cut. Now scientists in China have synthesised microscopic diamonds that are harder, tougher and more stable than any made in nature or in a lab.

These new nanodiamonds boast a special pattern in their crystal structure called nanotwinning, in which adjacent crystals share an interlacing boundary and grow into mirror images of one another. That twinning gives the diamonds their extraordinary hardness, the researchers say in a study published in yesterday's edition of the journal Nature.

Most diamonds are used not in engagement rings but for industrial purposes. Diamonds make sharp drill bits that penetrate the earth's crust in search of fossil fuels and minerals. They form diamond saw blades that grind down uneven road surfaces and immaculate crystals for conducting precise scientific experiments. But these functional diamonds need more than hardness to withstand the rigors of rough work.

Paradoxically, harder diamonds tend to fracture more easily, so scientists have long sought ways to make tougher materials that won't break under stress. Unfortunately, synthetic diamonds often involved trade-offs - when one quality (such as hardness) got better, another (toughness) got worse. Until now. Scientists at Yanshan University in Hebei province say that diamonds made with their new method surpass existing diamonds in every category.

The new nanodiamonds measure between 20 and 50 nanometres across, slightly larger than other nanodiamonds. A nanometre is equal to one billionth of a metre. But unlike their predecessors, the new stones contain twinning structures as small as five nanometres. That is roughly twice the thickness of a single strand of DNA.

"At these twinning boundaries, the crystals on each side are bonding together much better," said Bo Xu, a materials scientist who helped lead the study. All these advantages can be traced to the properties of a nanoparticle called onion carbon, the raw ingredient in the scientists' diamond recipe that they say deserves credit for their success.--iAbrasive report