Asteroid impact creates diamond materials with exceptionally complex structure

Shock waves from asteroid impacts create materials with many complex carbon structures that can be used to develop future engineering applications, according to an international study.

Scientists led by University College London found in a study published in the journal Proceedings. of National Academy of sciences 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 pressure.

The scientists say these structures could be designed for advanced mechanical and electronic applications, giving us the ability to design materials that are not only extremely strong, but also flexible with tunable electronic properties.

In this study, scientists from the United Kingdom, the United States, Hungary, Italy and France used detailed crystallographic and spectroscopic studies of the latest minerals from the Canyon Diablo iron meteorite, first discovered in 1891 in the Arizona desert, Lonsdaleite.

It was previously believed that lonsdalite (a rare natural allotrope of carbon), whose name comes from the name of the British crystallogist, Professor Dame Kathleen Lonsdale, the first female professor at the University of California at Los Angeles, was composed of pure hexagonal diamond, which distinguishes it from the classic cubic diamond.

However, the team found that it is actually made up of nanostructured diamonds and graphene-like intermediate segments (where two minerals grow together into a crystal) called diaphytes.

The team also identified cumulative defects or “errors” in the sequence of repeating patterns of layers of atoms.

“By identifying different types of growth between graphene and diamond structures, we can get closer to understanding the pressure and temperature conditions that occur during asteroid impacts,” said study lead author Dr. Peter Nemeth of the Geology and Geochemistry Research Institute (RCAES). .

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

Study co-author Professor Chris Howard from the Department of Physics and Astronomy at University College London explained: “This is very exciting as we can now detect diaphyte structures in diamonds using a simple spectroscopic method without the need for costly and painstaking research. electron microscopy.”

The structural units and complexity found in lonsdalite samples can occur in a wide variety of other carbonaceous materials through impact, static pressure, or vapor deposition, the scientists say.

Associate research professor Christoph Saltzman from the UCLA Department of Chemistry showed: “Through the controlled growth of layered structures, it should be possible to create materials that are both extremely rigid and flexible, as well as changeable electronic properties from conductor to insulator. “This discovery 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 called lonsdalite.

Source: phys.org.

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