• Wed. Sep 28th, 2022

Get hard on the machine parts

ByRandall B. Phelps

Sep 12, 2022

Strange diamonds from an ancient dwarf planet in our solar system could lead to the production of ultra-hard machine parts, say scientists.

A team of researchers, including those from Australia’s national science agency, CSIRO, have confirmed the existence of lonsdaleite in ureilite meteorites from the mantle of the dwarf planet.

Lonsdaleite is a rare hexagonal shaped diamond that is believed to be much stronger and harder than its more typical cubic cousin.

The research conducted by Monash University, in collaboration with CSIRO, RMIT University, the Australian Synchrotron and the University of Plymouth, was published today in the Proceedings of the National Academy of Sciences (PNAS).

The study provides clear evidence for the formation of lonsdaleite in nature, offering clues to synthetic production that could make machine parts more durable.

CSIRO scientist Colin MacRae said the discovery could have huge implications for industries like mining.

“If something that’s harder than diamond can be made easily, that’s something the industry would want to know,” MacRae said.

Lonsdaleite is named for the pioneering British crystallographer Dame Kathleen Lonsdale, although its existence has been a controversial subject.

This study, using a range of cutting-edge scientific techniques on the largest sample of ureleite meteorites to date, provides clear evidence of its existence.

At CSIRO, an electron probe microanalyzer (EPMA) was used to rapidly map the relative distribution of graphite, diamond, and lonsdaleite in the samples.

This flagship instrument, combined with RMIT University’s high-resolution transmission electron microscopy (TEM), has identified the largest lonsdaleite crystallites to date, down to one micron.

CSIRO’s Dr Nick Wilson said this collaboration of technology and expertise allowed the team to confidently confirm lonsdaleitis.

“Individually, each of these techniques gives us a good idea of ​​what this material is, but taken together it really is the gold standard,” Dr. Wilson said.

The study, which was led by geologist Professor Andy Tomkins of Monash University, reveals a new process in which lonsdaleite is created, replacing graphite crystals in the dwarf planet’s mantle facilitated by super-hot fluid when he cools down and decompresses.

“We propose that the lonsdaleite in the meteorites formed from supercritical fluid at high temperature and moderate pressures, almost perfectly preserving the textures of pre-existing graphite,” Prof Tomkins said.

“Later, the lonsdaleite was partially replaced by diamond as the environment cooled and the pressure decreased,” he said.

Usually containing large abundances of diamonds, ureilite meteorites are arguably the only large suite of samples available from the mantle of a dwarf planet.

The parent asteroid was catastrophically disrupted by a giant impact while the mantle was still very hot, creating the ideal conditions for the growth of lonsdaleite and then diamond as pressure and temperature decreased in an environment rich in fluids and minerals. gas.