Diamond is million times harder than thought

Washington, Jan 27 : Diamond is the hardest object on earth, strong enough to slice through glass and steel.

Surprisingly, very little is known about its strength under extreme conditions. But Lawrence Livermore National Lab (LLNL) scientists proved that diamond becomes even stronger during rapid compression.

Using the Janus laser at LLNL and the Omega laser at the University of Rochester, they showed that when shock waves are applied to diamond with powerful lasers, it can withstand nearly a million times atmospheric pressure before being crushed.

"It could also provide insights into the ancient history of natural diamonds found on Earth and in meteorites, where shock waves caused by impact are common," said Stewart McWilliams, who led the study.

McWilliams conducted the experiments as a graduate student at University of California Berkley (UC-B) while on a Student Employee Graduate Research Fellowship (SEGRF) at LLNL.

Most natural diamonds are formed at high-pressure, high-temperature conditions existing at depths of 87 to 120 miles in the Earth's mantle.

Carbon-containing minerals provide the carbon source, and the growth occurs over periods from 1 billion to 3.3 billion years (25 percent to 75 percent of the age of the Earth).

In the recent research, the team measured the behaviour of natural diamond crystals under shock-wave compression between one million and 10 million atmospheres of pressure, and the diamonds were crushed and melted in just a nanosecond (one billionth of a second).

"What we found is that diamond exhibits considerable strength right up to the point it melts," McWilliams said.

"We reached some surprising conclusions about the strength of diamond," said LLNL co-author Jon Eggert. "This type of research informs us about the interiors of the gas giants as well our own planet."

Earlier research conducted by Livermore scientists show that diamond melts at around six million atmospheres of pressure and 14,000 degrees Fahrenheit, said a lab release.

Their experiments mimicked conditions on the icy gas giant planets (Uranus and Neptune) where, according to their research, icebergs of diamond could float on a sea of liquid carbon.

These findings are slated for publication in Physical Review B.