There\u2019s more than one form of diamond<\/h2>\n
Carbon atoms can bond together in a number of ways to form different materials including soft black graphite and hard transparent diamond.<\/p>\n
There are many well-known forms of carbon with graphite-like bonding, including graphene<\/a>, the thinnest material ever measured. But did you know there\u2019s also more than one type of carbon-based material with diamond-like bonding?<\/p>\n In a normal diamond, atoms are arranged in a cubic crystalline structure. However, it\u2019s also possible to arrange these carbon atoms, so they have a hexagonal crystal structure.<\/p>\n [Read: Here\u2019s how to make your website more accessible<\/span><\/a>]<\/em><\/p>\n This different form of diamond is called Lonsdaleite, named after Irish crystallographer and Fellow of the Royal Society Kathleen Lonsdale<\/a>, who studied the structure of carbon using X-rays.<\/p>\n There is much interest in Lonsdaleite, since it\u2019s predicted to be 58% harder than regular diamond<\/a> \u2014 which is already considered the hardest naturally-occurring material on Earth.<\/p>\n It was first discovered<\/a> in nature, at the site of the Canyon Diablo meteorite crater in Arizona. Tiny amounts of the substance have since been synthesized in labs by heating and compressing graphite, using either a high-pressure press or explosives.<\/p>\n Our research shows both Lonsdaleite and regular diamond can be formed at room temperature in a lab setting, by just applying high pressures.<\/p>\n Diamonds have been synthesized in laboratories<\/a> since as far back as 1954. Then, Tracy Hall at General Electric created them using a process that mimicked the natural conditions within the Earth\u2019s crust, adding metallic catalysts to speed up the growth process.<\/p>\n 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.<\/p>\n The other major method of diamond manufacture is via a chemical-gas process which uses a small diamond as a \u201cseed\u201d to grow larger diamonds. Temperatures of about 800\u2103 are required. While growth is quite slow, these diamonds can be grown large and relatively defect-free.<\/p>\n Nature has provided hints of other ways to form a 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 \u2013 creating what we call \u201cextraterrestrial diamonds<\/a>.\u201d<\/p>\n Scientists have been trying to understand exactly how impact or extraterrestrial diamonds form. There is some evidence<\/a> that, in addition to high temperatures and pressures, sliding forces (also known as \u201cshear\u201d forces) could play an important role in triggering their formation.<\/p>\n An object being impacted by shear forces is pushed in one direction at the top and the opposite direction at the bottom.<\/p>\n An example would be pushing a deck of cards to the left at the top and to the right at the bottom. This would force the deck to slide and the cards to spread out. Hence, shear forces are also called \u201csliding\u201d forces.<\/p>\n For our work, we designed an experiment in which a small chip of graphite-like carbon was subjected to both extreme shear forces and high pressures, to encourage the formation of diamond.<\/p>\n Unlike most previous work on this front, no additional heating was applied to the carbon sample during compression. Using advanced electron microscopy \u2014 a technique used to capture very high-resolution images \u2014 the resulting sample was found to contain both regular diamond and Lonsdaleite.<\/p>\n In this never before seen arrangement, a thin \u201criver\u201d of diamond (about 200 times smaller than a human hair) was surrounded by a \u201csea\u201d of Lonsdaleite.<\/p>\n The structure\u2019s arrangement is reminiscent of \u201cshear banding\u201d observed in other materials, wherein a narrow area experiences intense, localized strain. This suggest shear forces were key to the formation of these diamonds at room temperature.<\/p>\n The ability to make diamonds at room temperature, in a matter of minutes, opens up numerous manufacturing possibilities.<\/p>\n Specifically, making the \u201charder than diamond\u201d Lonsdaleite this way is exciting news for industries where extremely hard materials are needed. For example, diamond is used to coat drill bits and blades to extend these tools\u2019 service life.<\/p>\n The next challenge for us is to lower the pressure required to form the diamonds.<\/p>\n In our research, the lowest pressure at room temperature where diamonds were observed to have formed was 80 gigapascals. This is the equivalent of 640 African elephants on the tip of one ballet shoe!<\/p>\n If both diamond and Lonsdaleite could be made at lower pressures, we could make more of it, quicker and cheaper.<\/p>\n This article is republished from The Conversation<\/a> by Dougal McCulloch<\/a>, Professor, RMIT University<\/a> and Jodie Bradby<\/a>, Professor of Physics, Australian National University<\/a> under a Creative Commons license. Read the original article<\/a>.<\/em><\/p>\n![](\"https:\/\/images.theconversation.com\/files\/370037\/original\/file-20201118-15-l798gn.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip\")
The many ways to make a diamond<\/h2>\n
![\"Diagram](\"https:\/\/images.theconversation.com\/files\/370218\/original\/file-20201119-20-1si5ko.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip\")
<\/a>Making diamonds at room temperature<\/h2>\n
![](\"https:\/\/images.theconversation.com\/files\/369996\/original\/file-20201118-17-60elab.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip\")
Tough nuts to crack<\/h2>\n