Chinese scientists have developed a new material for hardness super diamond single crystal
July 27 12:37:42, 2025
**Summary**
A groundbreaking discovery was made by Professor Tian Yongjun from the State Key Laboratory of Metastable Materials Science and Technology at Yanshan University, in collaboration with scientists from both China and abroad. Using advanced high-temperature and high-pressure techniques, they successfully synthesized a nano-twinned cubic boron nitride material that exhibits hardness exceeding that of diamond single crystals. The research was published on January 17, 2013, in the prestigious journal *Nature*.
The study was highlighted on the cover and featured in the table of contents of the issue, with original images of the synthetic samples and detailed descriptions of the material’s extraordinary properties. The paper vividly illustrated the extreme hardness of the new material, comparing it to both diamond and cubic boron nitride in a visually striking manner.
Since the mid-1950s, diamond and cubic boron nitride have been the two most well-known superhard materials, widely used in industrial applications. Diamond, with a Vickers hardness of 60–100 GPa, has long been considered the hardest natural material, but its low oxidation temperature (around 600°C) limits its use in processing iron-based materials. Cubic boron nitride, with a hardness of 30–43 GPa and higher thermal stability (up to 1100°C), is more suitable for steel processing but lacks the hardness and toughness of diamond.
To address these limitations, researchers have sought ways to enhance the performance of cubic boron nitride. Over the past decade, Professor Tian Yongjun has led extensive theoretical and experimental studies, supported by multiple national science funding programs. In 2003, he proposed a microscopic theory of covalent crystal hardness, enabling quantitative prediction of single-crystal hardness. In 2012, he extended this theory to polycrystalline materials, proposing a model that predicted ultra-fine nanostructures could make existing hard materials even harder and transform superhard materials into "extremely hard" ones.
Based on this theory, Tian and his team successfully synthesized a transparent nano-twinned cubic boron nitride material with an onion-like structure, achieving a hardness of 108 GPa—surpassing that of diamond. The twin thickness was only 3.8 nm, far below the traditionally believed threshold for hardening. Remarkably, the material not only maintained its hardness but continued to increase it as the microstructure became smaller. Additionally, the material showed improved toughness and oxidation resistance.
Further analysis revealed that the hardening mechanism of polycrystalline covalent materials involves not only the Hall-Petch effect but also a quantum confinement effect. This effect can compensate for softening caused by other mechanisms, allowing continuous hardening without degradation. These findings challenged traditional understanding and opened new pathways for developing high-performance superhard materials.
The breakthrough attracted widespread attention from global media, including German national radio, *Scientific American*, and *American Connection*. *Nature* highlighted the study in a press release titled “Excellent Super-Hard Materials,†noting that the new material could enable a wide range of industrial applications. Reporter Nathan Hurst of *American Connection* remarked, “Diamond is the hardest material in the world. That’s just a myth.â€
The American Society for Materials Research also emphasized the potential of the new material, stating that it could challenge diamond’s status as the hardest substance. With superior hardness, toughness, and stability, the material may even surpass diamond in practical applications. This discovery marks a significant step forward in the field of superhard materials and could revolutionize the global machining industry.