Scientists Synthesize Pure Hexagonal Diamonds Harder Than Natural Diamonds
Researchers have successfully created pure hexagonal diamonds, demonstrating hardness exceeding that of natural diamonds, and resolving longstanding debates about the mineral lonsdaleite.
Researchers have successfully synthesized pure hexagonal diamonds, known as lonsdaleite, which exhibit hardness surpassing that of natural diamonds. This achievement resolves longstanding debates regarding the existence and properties of lonsdaleite.
The team, led by Shoulong Lai at the Henan Key Laboratory of Diamond Materials and Devices, employed high-pressure and high-temperature conditions to transform graphite into millimeter-sized hexagonal diamonds. The process involved compressing highly oriented pyrolytic graphite at approximately 20 gigapascals and heating it between 1,300°C and 1,900°C. This method facilitated the realignment of carbon atoms into a hexagonal structure.
To confirm the crystal structure, the researchers utilized synchrotron X-ray diffraction and atomic-resolution scanning transmission electron microscopy. These analyses verified the hexagonal arrangement of carbon atoms, distinguishing the synthesized material from cubic diamonds.
Mechanical testing revealed that the hexagonal diamonds possess a Vickers hardness of approximately 114 gigapascals, slightly exceeding the typical 110 gigapascals of natural diamonds. Additionally, the material demonstrated high thermal stability, withstanding oxidation at temperatures above 1,121 kelvin.
The successful synthesis of pure hexagonal diamonds opens new avenues for industrial applications, including the development of advanced cutting tools, abrasives, and high-performance electronic components. The findings were published in the journal Nature.