In nature, diamonds form deep in the earth over billions of years. This process requires an exceptionally high pressure and an atmosphere with temperatures exceeding 1,000.
Our international team has created two different types of diamonds at room temperature – and in a matter of minutes. For the first time diamonds have been successfully produced without the added heat of any laboratory.
Our findings are published in the journal Small.
Diamonds have more than one form
Carbon atoms can combine in many ways to form a variety of materials, including soft black graphite and hard transparent diamonds.
There are many well-known forms of carbon with a graphene-like bond, including graphene, the thinnest material ever measured. But did you know that there is more than one type of carbon-based material with a diamond-like bond?
In ordinary diamonds, the atoms are arranged in a solid crystalline structure. However, it is also possible to arrange these carbon atoms so that they have hexagonal crystal formation.
This different form of diamond is called Lonsdaleite, named after Kathleen Lonsdale, an Irish crystalgrapher and Fellow of the Royal Society, who studied the composition of carbon using X-rays.
The Crystal Structures of Cubic Diamond and Hexagon Lonsdalet have different arrangement of atoms. (Supply)
Lonsdaleite is of great interest, as it is estimated to be 58 percent harder than regular diamonds – already considered the hardest naturally occurring material on earth.
It was first found in nature, at the site of the Canyon Diablo meteorite crater in Arizona. A small amount of the substance is then synthesized in labs using high-pressure presses or explosives, heating and compressing the graphite.
Our research shows that using only high pressure, both labsdelite and regular diamonds form at room temperature in a lab setting.
Many ways to make diamonds
Diamonds have been synthesized in laboratories since 1954. Then, Tracy Hahn at General Electric created them using a process that mimics the natural conditions inside the Earth’s crust, which will add metal catalysts to accelerate the growth process.
The result was like a high-pressure, high-temperature diamond found in nature, but often smaller and less perfect. These are still manufactured, primarily for industrial applications.
Another major method of diamond making is through a chemical-gas process that uses small diamonds as “seeds” to grow large diamonds. A temperature of about 800 Tempe is required. While growth is fairly slow, these diamonds are grown large and relatively defect-free.
Nature has provided clues to other ways to make diamonds, including during the violent effects of meteorites on Earth, as well as the processes of high-speed asteroid collisions in our solar system – what we call “extraterrestrial diamonds.”
Scientists are trying to figure out exactly how impact or the outside world creates diamonds. There is some evidence that in addition to high temperatures and pressures, sliding forces (also known as “shear” forces) can play an important role in stimulating their formation.
The projectile affected by the shear forces is pushed in one direction at the top and in the opposite direction at the bottom.
One example is pushing a deck of cards to the top left and to the bottom right. This will force the deck to slide and spread the cards. Therefore, the shear force is also called “sliding force”.
In ‘shear’ forces, one object is pushed in one direction in one direction and in the opposite direction to the other. (Sharayanan / Wikimedia Cons)
Making diamonds at room temperature
For our work, we designed an experiment in which to promote the formation of diamonds, a small chip of carbon like graphite was subjected to both extreme shear force and high pressure.
Unlike previous work on this front, no additional heating was applied to the carbon sample during compression. Using advanced electron microscopy – a technique used to obtain very high-resolution images – it was found that both regular diamond and lonsdelite were found in the resulting sample.
In an arrangement never seen before, the diamond’s thin “river” (about 200 times smaller than human hair) was surrounded by a “sea” of loneliness.
This electron microscope image shows the ‘river’ of diamonds in the ‘sea’ of Lonsdaleite. (Supply)
The configuration of the structure is reminiscent of “shear bending” seen in other materials, in which a narrow area experiences intense, local stress. This suggests that shear forces were key to the formation of these diamonds at room temperature.
Crispy nuts
The ability to make diamonds at room temperature, in a matter of minutes, opens up numerous production possibilities.
In particular, making linseedlight “harder than diamond” in this way is exciting news for industries where extremely hard materials are needed. For example, diamonds are used to coat drill bits and blades to extend the service life of these tools.
The next challenge for us is to reduce the pressure required to form a diamond.
In our research, the lowest pressure at room temperature where diamonds are formed was found to be 80 gigapascals. This is the equivalent of 640 African elephants on top of a ballet shoe!
If both diamonds and lonsdelite can be made at low pressure, we can make them more, faster and cheaper.
Jodi Bradby, Professor of Physics at RMIT University and Australian National University.
This article is republished from the talk under the Creative Commons license. Read the original article.
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