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Asteroid impacts create diamond materials with an exceptionally complex structure

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According to an international study by UCL and Hungarian scientists, the shock waves caused by asteroid impacts on Earth create materials with a range of complex carbon structures that could be used for future engineering applications.

Posted today in Proceedings of the National Academy of SciencesA team of researchers have discovered that diamonds, formed during a high-energy shock wave from an asteroid impact about 50,000 years ago, have unique and exceptional properties caused by short-term high temperatures and extreme pressures.

The researchers say these structures could be designed for advanced mechanical and electronic applications, giving us the ability to design materials that are not only superhard, but malleable with tunable electronic properties.

For the study, scientists from the UK, USA, Hungary, Italy and France used detailed modern crystallographic and spectroscopic studies of the lonsdaleite mineral from the Canyon Diablo iron meteorite, first discovered in 1891 in the Arizona desert.

Named after the pioneering British crystallographer Professor Dame Kathleen Lonsdale, the first female professor at UCL, lonsdaleite was previously thought to be composed of pure hexagonal diamond, which set it apart from the classic cubic diamond. However, the team found that it is actually composed of nanostructured diamond and graphene-like growths (where two minerals in a crystal coalesce together) called diaphytes. The team also identified stacking defects, or “mistakes,” in sequences of repeating patterns of layers of atoms.

Lead author Dr. Peter Nemeth (Institute for Geological and Geochemical Research, RCAES) said: “By recognizing the different types of intergrowth between graphene and diamond structures, we can get closer to understanding the pressure and temperature conditions that occur during asteroid impacts. “

The team found that the distance between graphene layers is unusual due to the unique environment of carbon atoms that occur at the interface between diamond and graphene. They also demonstrated that the diaphyte structure is responsible for a previously unexplained spectroscopic feature.

Study co-author Professor Chris Howard (UCL Physics & Astronomy) said: “This is very exciting as we can now detect diaphytic structures in diamond with a simple spectroscopic technique without the need for costly and time-consuming electron microscopy.”

The structural units and complexity found in lonsdaleite samples can be found in a wide range of other carbonaceous materials produced by shock and static compression or vapor deposition, the scientists say.

Study co-author Professor Christoph Salzmann (Chemistry at UCLA) said: “Through the controlled growth of layers of structures, it should be possible to create materials that are both superhard and ductile, and also have adjustable electronic properties from conductor to insulator.

“The discovery therefore opened the door to new carbon materials with exciting mechanical and electronic properties that could lead to new applications ranging from abrasives and electronics to nanomedicine and laser technology.”

In addition to calling attention to the reported exceptional mechanical and electronic properties of carbon structures, the scientists are also challenging the current simplistic structural understanding of the mineral referred to as lonsdaleite.

The researchers are also grateful to late co-author Professor Paul Macmillan, who was the Sir William Ramsay Chair of Chemistry at the University of California, for bringing the team together, his tireless enthusiasm for this work, and his continued contributions to the field of diamond research.


Methods for Synthesizing Stable Diamane at High Pressure


Additional Information:
Impact molded carbon materials with intergrown sp3– and cn2-linked nanostructural units, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2203672119

Courtesy of University College London

Quote: Asteroid Impacts Create Exceptionally Complex Diamond Materials (2022 July 19), retrieved July 20, 2022 from https://phys.org/news/2022-07-asteroid-impacts-diamond-materials-exceptionally .html

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