Chinese Researchers Claim Strongest Evidence Yet for Synthesis of 'Hexagonal Diamond'

Summary

Researchers at Zhengzhou University in China have reported what experts are calling the most convincing evidence to date for the laboratory synthesis of hexagonal diamond, a rare and potentially harder variant of conventional diamond. The team, led by physicist Chongxin Shan, used high-pressure and high-temperature techniques to transform graphite into millimeter-sized samples of the elusive material, which has been the subject of decades of debate in the scientific community.

Hexagonal diamond, also known as lonsdaleite, differs from conventional cubic diamond in its atomic structure. While both forms consist entirely of carbon atoms arranged in tetrahedra, hexagonal diamond's pattern repeats every two layers instead of three, creating shorter and stronger bonds between layers. Theoretical predictions suggest this structural difference could make hexagonal diamond more than 50% harder than cubic diamond, which is already considered the hardest mineral on Earth.

The breakthrough comes after years of disputed claims about hexagonal diamond's existence and synthesis. Previous attempts to identify the material have been plagued by difficulties in distinguishing it from highly defective cubic diamond using X-ray diffraction techniques. However, the Chinese team's work shows crucial telltale diffraction peaks that conclusively demonstrate the hexagonal structure, according to Oliver Tschauner, a crystallographer at the University of Nevada, Las Vegas, who peer-reviewed the research.

The successful synthesis opens potential applications in cutting tools, thermal management materials, and quantum sensing. Tests showed the hexagonal diamond samples were stiffer, more resistant to oxidation, and slightly harder than cubic diamond. The material was created by subjecting highly oriented pyrolytic graphite to 20 gigapascals of pressure at temperatures between 1,300-1,900°C using tungsten carbide anvils.

• The synthesized material demonstrates superior properties including greater stiffness, oxidation resistance, and hardness compared to conventional diamond
• Potential applications span cutting tools, thermal management, and quantum sensing technologies

Editorial Opinion

This research represents a significant milestone in materials science, potentially ending a half-century debate about hexagonal diamond's existence and synthesis. If the findings hold up to further scrutiny and the synthesis process can be scaled economically, hexagonal diamond could revolutionize industries requiring ultra-hard materials. However, the real test will be whether other laboratories can reproduce these results and whether the material's theoretical advantages translate into practical applications that justify what will likely be a complex and expensive manufacturing process.