New synthetic diamonds are hardest gems ever created

Researchers have created synthetic diamonds that are less prone to deformation and breaking than both natural and man-made diamonds.

Researchers, led by Yongjun Tian and Quan Huang at Yanshan University in China, used tiny particles of carbon, layered like onions, and subjected them to high temperatures and pressures.

The resulting diamonds had a unique structure that makes them more resistant to pressure and allows them to tolerate more heat before they oxidise and turn to either gas (carbon dioxide and monoxide) or ordinary carbon, losing many of their unique diamond properties.

Artificial diamonds used on tools are harder because they are polycrystalline diamonds, or aggregates of diamond grains called domains, that measure a few micrometers or nanometers across.

The grains help to prevent the diamond from breaking, as the boundaries act like small walls that keep chunks of diamond in place. The smaller the domains are, the stronger the diamond, 'Live Science' reported.

Tian's team used the onionlike carbon nanoparticles to make diamonds with domains that are a few nanometers in size and are mirror images of each other.

Such "nanotwinned" crystals are much harder than ordinary diamonds, by a factor of two.
The team tested the artificial diamond's hardness by pressing a pyramid-shaped piece of diamond into the nanotwinned diamond.

The group made a small indentation in their artificial diamond, applying pressures equivalent to nearly 200 gigapascals (GPa) - about 1.9 million atmospheres.

An ordinary natural diamond would crush under just half that pressure.

The study is detailed in the journal Nature.