Ultra Hard Diamonds

Diamonds might not be as rare or eternal as diamond miners would like everyone to believe, but they’re still rare enough that creating synthetic diamond is a worthwhile scientific endeavor. Natural diamonds only form deep in the Earth under intense heat and pressure, but researchers from the Australian National University (ANU) and RMIT University say they’ve developed a way to create diamonds at room temperature, and some of them are harder than your run-of-the-mill gemstones.

While the team didn’t need extreme heat to make diamonds, they did need a great deal of pressure. Using a device known as a diamond anvil cell, the team compressed carbon atoms with a force equivalent to 640 African elephants. That’s the big impressive number, but it was also about the finesse — the way researchers applied that pressure was the key to creating not one but two kinds of diamond.

The anvil cell was configured in such a way that the samples could experience shearing force. The researchers hypothesize this twisting and sliding movement allows carbon atoms to reorient themselves to form a strong diamond lattice. However, you can’t just dump some coal inside and come out with a glittering gemstone. The resulting samples are a mishmash of regular diamond and an alternative form of diamond called Lonsdaleite. They almost missed it, too. The sample didn’t have the expected properties after being exposed to so much pressure, but microscopic examination of the carbon atoms showed large blocks of Lonsdaleite surrounding bands of pure diamond.

The diamond found in these small veins is the same material that makes up the diamond gemstones but in very small quantities. This research is mostly focused on creating diamonds for industrial and scientific uses, and that means Lonsdaleite is the more interesting finding. Lonsdaleite is a hexagonal diamond and is theoretically much stronger than “regular” diamond, which has a cubic lattice.

Testing suggests Lonsdaleite could be 58 percent harder than those cubic diamonds, and there’s nowhere on Earth we can mine Lonsdaleite in any meaningful amount. Lonsdaleite exists in microscopic amounts in geological formations around some meteorite impact sites. So, the possibility that we could produce Lonsdaleite in the laboratory is exciting. If you need to cut something very hard, diamond is a common material to use in your tools. An even harder diamond is naturally even better, and that might be the eventual outcome of this research. The team hopes to devise a way to produce meaningful amounts of Lonsdaleite in the future.

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