We all know that diamonds are the toughest substance in existence. Meanwhile, a group of researchers at the Yanshan University in China, led by Quan Huang and Yongjun Tian, has developed synthetic diamonds that are harder than the natural diamonds. This means they are more resistant to breaking, deformation, and other external impacts than any other diamond known to man, be it natural or man-made diamonds.
In order to create these diamonds, the researchers made use of minute particles of carbon, which have a structure similar to that of onions, and elevated them to high temperatures and pressure. As a result, they received a diamond with a unique structure. This diamond had properties that were resistant to intense pressure. Furthermore, it also gave them the capability to withstand more temperature before they oxidized and produced either carbon dioxide or carbon monoxide. This entailed losing of most of its unique properties as well.
Gem-quality diamonds are single crystals and are quite hard. However, artificial diamonds that are used in tools are even harder. The reason behind this is that these are polycrystalline diamonds or diamond aggregates that are a few micrometers or nanometers long. It gains its resistance power from its grain structure, which acts like a boundary with small walls to properly keep the diamond chunks in position. As the size of these domains decreases, the strength of these diamonds increase.
This is the principle applied by the research team in China. They used the onion-like nanoparticles to synthesized diamonds that had the dimensions of a few nanometers. In addition, they were mirror images of each other. Such structures are known as “nanotwinned” crystals. Note that such diamonds are stronger than the normal diamonds by a factor of two.
The research team experimented by bringing down pyramid shaped diamond piece with an enormous amount of force to test the diamond’s hardness. They eventually made a small indentation on the synthesized diamond when the pressure reached around 200 gigapascals (GPa). This is equivalent to 1.9 million atmospheres of pressure. Remember, that a normal diamond would have been crushed by the application of about half the amount of that pressure.
The team also conducted tests on the limit of temperature that the diamond could take before getting oxidized. While ordinary diamonds oxidized at around 1418 and 1481 degrees Fahrenheit, the nanotwinned diamonds did not oxidize until it reached the limit of 1796 or 1932 Fahrenheit.