Do you remember when Superman crushed a lump of coal with his hands and turned it into a diamond?
There were two problems that people were quick to point out at the time.
Firstly, the diamond was perfectly shaped.
Secondly, Superman didn’t use his heat ray in the diamond-making process. And heat, about 1900 degrees Celsius, was thought to be required when making diamonds in the laboratory – until now.
Researchers from the Australian National University and RMIT University have created diamonds in “mere minutes, without heat – by mimicking the force of an asteroid collision”.
Natural diamonds are usually formed over billions of years, about 150 kilometres deep in the Earth where there are high pressures and temperatures above 1000 degrees.
Professor Jodie Bradby, from Electronic Materials Engineering in the ANU Research School of Physics, is one of the lead researchers. She said the breakthrough “shows that Superman may have had a similar trick up his sleeve”.
An international team, led by the Australian universities, made two types of diamonds: “The kind found on an engagement ring and another type of diamond called Lonsdaleite, which is found in nature at the site of meteorite impacts such as Canyon Diablo in the US.”
Lonsdaleite, named after the crystallographer Dame Kathleen Lonsdale, the first woman elected as a Fellow to the Royal Society, has a different crystal structure to regular diamond.
It is predicted to be 58 per cent harder – and is “considered the hardest naturally occurring material on Earth”.
According to a statement from the researchers, tiny amounts of Lonsdaleite have been synthesised in labs by heating and compressing graphite, using either a high-pressure press or explosives.
“Lonsdaleite has the potential to be used for cutting through ultra-solid materials on mining sites,” Professor Bradby said.
“Creating more of this rare but super useful diamond is the long-term aim of this work.”
In what’s being described as “unexpected discovery” both Lonsdaleite and regular diamond have been formed at normal room temperatures by just applying high pressures – “equivalent to 640 African elephants on the tip of a ballet shoe.”
Professor Bradby said the discovery was made by altering how pressure was applied.
“The twist in the story is how we apply the pressure. As well as very high pressures, we allow the carbon to also experience something called ‘shear’ – which is like a twisting or sliding force. We think this allows the carbon atoms to move into place and form Lonsdaleite and regular diamond.”
Co-lead researcher RMIT Professor Dougal McCulloch used new, advanced electron microscopy techniques to capture solid and intact slices from the experimental samples to create snapshots of how the two types of diamonds formed.
“Our pictures showed that the regular diamonds only form in the middle of these Lonsdaleite veins,” Professor McCulloch said.
“Seeing these little rivers of Lonsdaleite and regular diamond for the first time was just amazing and really helps us understand how they might form.”
As the researchers explain in a piece at The Conversation, diamonds have been synthesised in laboratories since as far back as 1954.
Then, Howard Tracy Hall at General Electric created them using a process that mimicked the natural conditions within the Earth’s crust, adding metallic catalysts to speed up the growth process.
The result was high-pressure, high-temperature diamonds similar to those found in nature, but often smaller and less perfect. These are still manufactured today, mainly for industrial applications.
“Nature has provided hints of other ways to form diamond, including during the violent impact of meteorites on Earth, as well as in processes such as high-speed asteroid collisions in our solar system – creating what we call ‘extraterrestrial diamonds’,” the researchers write.
The team, which included University of Sydney and Oak Ridge National Laboratory in the US, published the research findings in the journal Small.