Lab-made paracrystalline diamond’s unique structure allows it to tolerate extreme heat

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A new form of diamond created by crushing buckyballs is as strong as natural diamond and better able to withstand heat

Physics



24 November 2021

Cloudy mineral rocks

Shutterstock / Cheshirskiy Kot

A new form of diamond has been created. The diamond’s unique structure gives it properties that are similar to natural diamonds, but it is more stable under extreme heat, so may be useful in tools that operate in hot conditions.

There are two main types of molecular structure in diamonds and many other materials: crystalline structure, in which all of the atoms are neatly organised in repeating arrangements, and amorphous structures, which mostly are mostly disorganised. Howard Sheng at George Mason University in Virginia and his colleagues have made a diamond with a structure between these two for the first time.

The new material, called paracrystalline diamond, is made up of of small structures called paracrystallites consisting of just a few carbon atoms. There is no particular order to the way the paracrystallites are arranged. “This is totally different from the diamond we know,” says Sheng.

Sheng and his colleagues created the material by crushing a type of carbon molecule called Buckminsterfullerene, or buckyballs, between six ultra-hard carbide anvils. At pressures of about 30 gigapascals – about 450 times the pressure at the bottom of the Mariana trench – and temperatures in excess of 1200°C, the buckyballs turned into paracrystalline diamond.

“We took it for granted that there were just amorphous and crystalline structures, but there is this intermediate state that we’ve been overlooking,” says Sheng. Similar paracrystalline states might exist in other solids as well, says Sheng, who hopes to find other new materials.

The paracrystalline diamonds are much more stable than many other forms of diamond at high temperatures. They are also just as hard as natural diamonds, so could be used in saws and other industrial tools that need to function for a long time at high temperatures, Sheng says.

Journal reference: Nature, DOI: 10.1038/s41586-021-04122-w

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