Scientists first observed and recorded the process of graphite-generating hexagonal diamond

Stefan Turneaure, the first author of the article, is preparing to shoot the target room. Image source: Washington State University

A new study by researchers at Washington State University answers the long-standing question of the formation of rare diamonds by the impact of large meteorites. Hexagonal diamond or hexagonal carbon is harder than ordinary wedding diamond ring diamonds, and it is also thought to be naturally formed by large graphite-bearing meteorites hitting the earth.

Since being discovered in the meteorite fragments of Arizona half a century ago, scientists have been pondering the precise pressures and other conditions required to make hexagonal diamonds.

Now, a group of WSU researchers have observed and documented for the first time the process of generating hexagonal diamond under impact compression in a highly preferred orientation of pyrolytic graphite, and revealed the key details of its formation. This finding helps planetary scientists use the presence of hexagonal diamonds in craters to estimate the severity of the impact.

This research has the potential to benefit from an unprecedented experimental development - the Dynamic Compression Division (DSC) led by WSU at the Argonne Advanced Photon Source National Laboratory. DCS is the first experimental facility to correlate different shock wave compression capabilities with synchrotron radiation X-rays. Utilizing its unique capabilities, the Washington State team is able to take real-time shots of X-ray snapshots of graphite converted to hexagonal diamonds.

The researchers' research results were published in the journal Science Progress.

“The conversion of hexagonal diamonds took place at a lower pressure than previously thought,” said Yogendra Gupta, WSU's tenured professor and director of the Institute for Impact Physics, who said: “This result is used to estimate the location of the meteorite impact on the ground. The thermodynamic conditions are of great significance."

Manufacturing diamond

WSU impact physicist Stefan Turneaure and a team of researchers found that at 500,000 atmospheres, the highly oriented graphite form of the crystalline structure transforms into a rare form of hexagonal diamond, which is about four times lower than previously shown. .

To get their results, the researchers shot a lithium fluoride impactor at a speed of 11,000 miles per hour onto a 2 mm thick graphite disk. Then, when the shock wave compresses the graphite sample, they take a snapshot of the pulsed synchrotron X-ray at a rate of 150 billion per second. Their work clearly shows that graphite samples are converted to hexagonal diamonds before being pulverized into dust.

“Most of the previous studies used microscopic examination of samples to impact compression to infer what might happen,” Turneaure said. “This late measurement does not indicate that the material has occurred during impact compression. what."

Late outlook

Turneaure and Gupta said that the next study will explore under what conditions pure hexagonal diamond can be repaired after impact compression.

“Diamond is a very exciting material, and our work in this area has only just begun,” Gupta said. “Next, we plan to study the durability of this diamond at low pressure. Because it is considered Ordinary cubic diamonds are about 60% hard, so if they can be successfully repaired after impact compression, hexagonal diamonds will have many potential uses in the industry."

The article is from the rdmag website, the original title is Researchers Document Transformation of Graphite into Hexagonal Diamond

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