Shock waves from asteroids colliding with Earth create materials with an array of complex carbon structures, which can be used to develop future engineering applications, according to an international study led by UCL and Hungarian scientists.
Posted today in Proceedings of the National Academy of SciencesThe team of researchers found that diamonds that were formed during a high-energy shock wave from an asteroid impact about 50,000 years ago have unique and exceptional properties, due to the high short-term temperatures and extreme pressure.
The researchers say these structures can be targeted for advanced mechanical and electronic applications, giving us the ability to design materials that are not only extremely tough but also malleable with tunable electronic properties.
For this study, scientists from the United Kingdom, United States, Hungary, Italy and France used detailed crystallographic and spectroscopic examinations of the latest minerals from the Canyon Diablo iron meteorite first discovered in 1891 in the Arizona desert.
Named after pioneering British crystallologist Professor Dame Kathleen Lonsdale, the first female professor at UCLA, Lonsdalite was previously thought to consist of pure hexagonal diamond, distinguishing it from classic cubic diamond. However, the team found that it is actually composed of nanostructured diamonds and graphene-like interlayers (where two metals grow into a crystal together) called diaphites. The team also identified stacking faults, or “errors,” in the sequence of repeating patterns of layers of atoms.
Lead author Dr. Peter Nemeth (Institute of Geospatial and Geochemical Research, RCAES) said: “By learning about the different types of growth between graphene and diamond structures, we can come closer to understanding the pressure and temperature conditions that occur during asteroid collisions.”
The team found that the distance between graphene layers is unusual due to the unique environments of carbon atoms that occur at the interface between diamond and graphene. They also showed that the diaphragm structure is responsible for a previously unexplained spectroscopy advantage.
Study co-author Professor Chris Howard (UCL Physics & Astronomy) said: “This is very exciting as we can now detect diaphragm structures in diamond using a simple spectroscopic technique without the need for costly and painstaking electron microscopy.”
According to the scientists, the structural units and complexity reported in the lonsdaleite samples can occur in a wide variety of other carbonaceous materials resulting from shocks and static pressure or by deposition from the vapor phase.
Study co-author Professor Christoph Salzmann (UCL Chemistry), said, “Through the controlled growth of the layer structures, it should be possible to design materials that are both extremely rigid and flexible, as well as modifiable electronic properties from conductor to insulator.
“This discovery has opened the door to new carbon materials with exciting mechanical and electronic properties that may lead to new applications ranging from abrasives and electronics to nanomedicine and laser technology.”
In addition to drawing attention to the exceptional mechanical and electronic properties of the reported carbon structures, the scientists also challenge the current simplified structural view of the mineral referred to as lonsdaleite.
The researchers also express their gratitude to the late co-author Professor Paul Macmillan, who was Sir William Ramsay’s Head of Chemistry at UCLA, for uniting the team, his tireless enthusiasm for this work and his enduring contributions to the field of diamond research.
Methods for assembling a stable diamane under high pressure
Shock-formed carbon materials with sp3– and sp2interconnected nanostructured modules, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2203672119
Presented by University College London
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