Manufacture of diamonds in minutes at room temperature

An international team of scientists have challenged nature to make diamonds in minutes in a room-temperature laboratory – a process that normally requires billions of years, enormous amounts of pressure, and extremely high temperatures.

The team, led by The Australian National University (ANU) and RMIT University, made two types of diamonds: the type 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 United States.

One of the leading researchers, ANU’s Professor Jodie Bradby, said their breakthrough shows Superman may have had a similar trick up his sleeve when he grinded coal into diamond, without using his beam of heat.

“Natural diamonds typically form over billions of years, about 150 kilometers deep in the Earth, where pressures and temperatures are high above 1,000 degrees. CelsiusSaid Professor Bradby of the ANU Research School of Physics.

The team, including former ANU doctoral student Tom Shiell now at the Carnegie Institution for Science, had previously created Lonsdaleite in the lab only at elevated temperatures.

This unexpected new finding shows that Lonsdaleite and regular diamond can also form at normal room temperatures by simply applying high pressure – equivalent to 640 African elephants on the tip of a ballet shoe.

“The turn of the story is how we apply pressure. In addition to very high pressures, we also allow the carbon to undergo something called “shear” – which is like a twisting or sliding force. We believe this allows the carbon atoms to fall into place and form Lonsdaleite and regular diamond, ”Professor Bradby said.

Co-principal investigator Professor Dougal McCulloch and his team at RMIT used advanced electron microscopy techniques to capture solid, intact slices from the experimental samples to create snapshots of the formation of the two types of diamonds.

“Our photos have shown that ordinary diamonds only form in the middle of these Lonsdaleite veins using this new method developed by our interagency team,” said Professor McCulloch.

“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.”

Lonsdaleite, named after crystallographer Dame Kathleen Lonsdale, the first woman elected to the Royal Society, has a different crystal structure than ordinary diamond. It is predicted that it will be 58% more difficult.

“Lonsdaleite has the potential to be used to cut ultra-strong materials at mine sites,” said Professor Bradby.

“Creating more of this rare but super useful diamond is the long term goal of this work.”

Ms. Xingshuo Huang is an ANU PhD student working in Professor Bradby’s lab.

“Being able to make two types of diamonds at room temperature was exciting to do for the first time in our lab,” Ms. Huang said.

The team, which involved the University of Sydney and the Oak Ridge National Laboratory in the United States, published the research results in the journal Small.

Reference: “Investigation of Room Temperature Formation of the Ultra – Hard Nanocarbons Diamond and Lonsdaleite” by Dougal G. McCulloch, Sherman Wong, Thomas B. Shiell, Bianca Haberl, Brenton A. Cook, Xingshuo Huang, Reinhard Boehler, David R. McKenzie and Jodie E. Bradby, November 4, 2020, Small.
DOI: 10.1002 / smll.202004695