Diamonds form during asteroid impacts have unique properties

It could be used for advancing future engineering applications.


Diamonds can indeed be formed in a big asteroid impact. The asteroid impact carries such high levels of energy—more than 20 gigapascals, sending a shock wave through the rock and turning the graphite into diamond.

Such diamonds, formed during asteroid collision around 50,000 years ago, have unique and exceptional properties, suggesting a new study. These structures can offer an idea to design ultra-hard and malleable materials with tunable electronic properties.

Scientists from the UK, US, Hungary, Italy, and France employed cutting-edge spectroscopic and crystallographic analyses to examine the mineral lonsdaleite from the Canyon Diablo iron meteorite, which was discovered in the Arizona desert in 1891. Lonsdaleite was previously thought to consist of pure hexagonal diamond, distinguishing it from the classic cubic diamond.

However, the team found that it comprises nanostructured diamond and graphene-like intergrowths (where two minerals in a crystal grow together) called diaphites. The team also discovered stacking flaws, or “errors,” in the repeating patterns of the atoms’ layers.

The distance between the graphene layers is unusual due to the unique environments of carbon atoms occurring at the interface between diamond and graphene. They also demonstrated that the graphite structure is responsible for a previously unexplained spectroscopic feature.

Lead author Dr. Péter Németh (Institute for Geological and Geochemical Research, RCAES) said: “Through the recognition of the various intergrowth types between graphene and diamond structures, we can get closer to understanding the pressure-temperature conditions that occur during asteroid impacts.”

Study co-author Professor Chris Howard (UCL Physics & Astronomy) said: “This is very exciting since we can now detect graphite structures in diamond using a simple spectroscopic technique without the need for expensive and laborious electron microscopy.”

According to the scientists, the structural units and the complexity reported in the lonsdaleite samples can occur in a wide range of other carbonaceous materials produced by shock and static compression or by deposition from the vapor phase.  

Study co-author Professor Christoph Salzmann (UCL Chemistry) said“Through the controlled layer growth of structures, it should be possible to design materials that are both ultra-hard and also ductile, as well as have adjustable electronic properties from a conductor to an insulator.”

“The discovery has opened the door to new carbon materials with exciting mechanical and electronic properties that may result in new applications ranging from abrasives and electronics to nanomedicine and laser technology.”

The study is published in the Proceedings of the National Academy of Sciences.


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