Chinese Scientists Synthesize Pure Hexagonal Diamond Harder Than Natural Diamond
Researchers in China have successfully created pure hexagonal diamond, demonstrating its superior hardness and thermal stability compared to natural cubic diamond.
Chinese researchers have successfully synthesized pure hexagonal diamond, also known as lonsdaleite, a rare form of diamond previously found only in meteorites. This achievement confirms the material's existence and reveals its superior hardness and thermal stability compared to natural cubic diamond.
The team, led by physicist Chongxin Shan from Zhengzhou University, subjected highly oriented graphite to extreme conditions—20 gigapascals of pressure and temperatures between 1,300 and 1,900 degrees Celsius. This process produced millimeter-sized samples of pure hexagonal diamond. Structural analyses using X-ray diffraction and atomic-resolution electron microscopy confirmed the material's purity and unique hexagonal lattice.
Mechanical testing indicated that hexagonal diamond exhibits a Vickers hardness of approximately 114 gigapascals, slightly surpassing the 110 gigapascals typical of natural cubic diamonds. Additionally, hexagonal diamond demonstrated higher shear modulus and notable thermal stability, suggesting potential applications in cutting tools, thermal management materials, and quantum sensing.
This breakthrough addresses longstanding debates regarding the existence and properties of hexagonal diamond, paving the way for future research and practical applications of this ultra-hard material.