Research published on Tuesday and led by Monash University could lead to the production of new ultra-hard diamonds with utility in industrial applications.
The team, made up of researchers from Monash University, CSIRO, RMIT University, the Australian Synchrotron and the University of Plymouth, have published their work in Proceedings of the National Academy of Sciences (PNAS.)
A CSIRO statement said the work confirmed the existence of lonsdaleite, a type of diamond that is hexagonal rather than cubic, in a sample of ureleite meteorites from an ancient dwarf planet.
Lead research professor Andy Tomkins, a geologist at Monash University, said the work showed a process that created lonsdaleite. In it, he replaced the graphite crystals in the planet’s mantle “easily with a superheated fluid as it cools and decompresses.”
Tomkins said the researchers “propose that the lonsdaleite in the meteorites formed from a supercritical fluid at high temperature and moderate pressures, almost perfectly preserving the textures of pre-existing graphite.”
“There is strong evidence that there is a newly discovered formation process for lonsdaleite and regular diamond, which is like a supercritical chemical vapor deposition process that took place in these space rocks, probably on the dwarf planet soon after of a catastrophic collision,” the professor added. Dougal McCulloch from RMIT.
“Chemical vapor deposition is one of the ways that people make diamonds in the lab, basically by growing them in a specialized chamber.”
An electron probe microanalyzer at CSIRO was used for the first time to “rapidly map the relative distribution of graphite, diamond and lonsdaleite” in samples.
Together with high-resolution transmission electron microscopy at RMIT University, it “helped identify the largest lonsdaleite crystallites to date, up to one micron”.
CSIRO said the two techniques and collaboration between experts helped confirm the presence of lonsdaleite, the “existence [of which] It has been a controversial issue.”
The organisation’s Colin MacRae said the implications could be huge for industrial use.
“If something that’s harder than diamond can be easily manufactured, that’s something the industry would like to know,” he said.
The team document can be accessed here.
Image: Tomkins (left) with RMIT University PhD scholar Alan Salek holding a sample of ureilite meteorite at the RMIT Microscopy and Microanalysis Facility. (Credit: RMIT University)