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Chinese researchers have succeeded in synthesizing the hundred-micron-scale hexagonal diamond, a material primarily found in meteorites, which is harder than the ordinary diamond found on Earth.
The study, published on Wednesday in the journal Nature, promises to redefine the limits of superhard materials, according to the researchers.
The Earth diamond owes its reputation as the king of hardness to its carbon atoms arranged in a tetrahedral lattice, making it extremely hard and wear-resistant.
However, this structure has a weakness -- certain planes can easily slip and shift when force is applied, thereby limiting its strength. As a consequence, scientists have turned their attention to another type of super diamond with a more exquisite structure and superior properties, namely the hexagonal diamond.
Chinese researchers involved in the published study innovatively proposed a method for transforming graphite into a hexagonal diamond. Under controllable high-temperature, high-pressure and quasi-hydrostatic conditions, they compressed and heated graphite single crystals to ultimately obtain a high-purity hexagonal diamond.
Previous attempts to synthesize a hexagonal diamond were largely unsuccessful due to extremely stringent formation requirements. Under high-temperature and high-pressure conditions, the end result tends to be the formation of a cubic diamond and not a hexagonal diamond.
The successful synthesis of a high-purity hexagonal diamond by the Chinese research team is attributed to their choice of high-purity natural graphite single crystals, as well as their use of high-pressure in-situ X-ray observation to monitor changes in samples, said Yang Liuxiang, one of the authors of the paper and a researcher at the Beijing-based Center for High-Pressure Science & Technology Advanced Research.
This study lays a methodological foundation for future research on diamond-like materials, according to Ho-kwang Mao, a scientist in high-pressure science and a foreign member of the Chinese Academy of Sciences.
This synthesized hexagonal diamond is expected to pave new pathways for the development of superhard materials and high-end electronic devices, Mao added.
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