Diamonds obtained by the new method have a hexagonal crystal structure instead of the usual cubic structure, with impressive hardness and thermal stability.
Natural diamonds have a maximum hardness of only about 110 GPa compared to the hardness of 155 GPa of newly synthesized diamonds.
ScienceAlert reported on March 3 that scientists have just synthesized diamonds that are harder than natural diamonds, through a new approach to the structure of this gemstone.
Diamond is known as the hardest natural material on earth, although there are synthetic forms that are even harder. Recently, a group of experts at several universities and research institutes in China found a new synthesis method.
The team placed graphite under extremely high pressure, before heating it to 1,527 degrees Celsius. The resulting diamond had a hexagonal crystal structure instead of the usual cubic structure.
Hexagonal diamonds first came to scientists' attention more than 50 years ago, after they were discovered at a meteorite impact site. The new research is the first solid evidence that this internal structure increases hardness.
According to the research team, natural and synthetic diamonds mainly have cubic crystal lattices, while hexagonal structures are rare and largely unexplored, due to the low purity and very small size of most samples obtained.
“The synthesis of hexagonal diamond is challenging and even its existence remains controversial,” according to the team.
The newly synthesized diamond has a hardness of 155 GPa, a unit of measurement of the pressure a material can withstand. Meanwhile, natural diamonds have a maximum hardness of about 110 GPa.
The thermal stability of the new diamond is also impressive. The researchers say the synthetic hexagonal diamond can withstand temperatures of up to 1,100 degrees Celsius, compared to 900 degrees Celsius for nanodiamonds commonly used in industrial applications. Natural diamonds can withstand higher temperatures, but only in a vacuum.
This isn't the first time scientists have managed to create hexagonal crystal diamonds in the lab. A previous project in 2016 created such diamonds from amorphous carbon, a material that doesn't have a fixed shape.
However, the research team has a new synthesis method that has been shown to be able to create superhard diamond materials in the laboratory.
“Our findings provide valuable insights into the transformation of graphite into diamond under high pressure and temperature, creating opportunities for the fabrication and applications of this unique material,” according to the team.
Source: https://thanhnien.vn/che-tao-duoc-kim-cuong-cung-hon-kim-cuong-tu-nhien-bang-phuong-phap-moi-185250303111931835.htm
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