It was learned from Yanshan University that the research team led by Prof. Tian Yongjun of Yanshan University cooperated with Professor Ma Yuming of Jilin University and Professor Wang Yanbin of the University of Chicago. After the synthesis of extremely hard nanocrystalline cubic boron nitride in 2013, it made another breakthrough under high temperature and high pressure. A nano-twisted structure diamond block having twice the hardness of natural diamond was successfully synthesized. The research was published in the June 12, 2014 issue of Nature.
Since its discovery more than 2,700 years ago, natural diamond has been recognized as the hardest material in nature. In 1955, the United States General Electric Company successfully synthesized synthetic diamond single crystals in the laboratory using high temperature and high pressure technology, which opened a new chapter in the application of diamond industry and became a milestone in the research of superhard materials. From then on, it synthesized a new harder than natural diamond. Materials have become a common dream of the scientific community and industry. But after years of hard work, scientists began to be disappointed with the realization of this dream.
So far, nano-twisted structure diamonds have not been obtained by high-pressure phase transition of carbon precursors such as graphite, amorphous carbon, and glassy carbon. To this end, Professor Tian Yongjun's research team and its collaborators began to study the phase transition process of onion carbon under high temperature and high pressure. At lower temperatures, onion carbon also forms a monoclinic diamond while forming a nano-twisted cubic diamond. In the article they named it "M-diamond". At higher temperatures, onion carbon is converted into a single-phase nano-twisted structure diamond with an average thickness of twin crystals as small as 5 nm. This nano twinned diamond has unprecedented hardness and stability: Vickers hardness is about twice that of natural diamond, and the initial oxidation temperature in air is more than 200 degrees Celsius higher than natural diamond.
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