As everyone knows, diamond, or more specifically, diamond, is the hardest natural substance. However, there is an even stronger king above it: hexagonal diamond, also known as lonsdaleite.
Researchers from Zhengzhou University, Nanjing University, and other teams have synthesized millimeter-sized pure-phase hexagonal diamond in the laboratory for the first time, ending a debate that has puzzled the scientific community for over 60 years.
The unique hexagonal crystal symmetry of hexagonal diamond alters the way the material resists stress, making it more effective at resisting shear failure.
Theoretical predictions show that under extreme stress conditions, hexagonal diamond can be more than 50% harder than conventional diamond.
Hexagonal diamond was predicted to exist as early as 1962 and was first discovered in a meteorite in 1967. However, for many years, natural hexagonal diamond existed only as nanoscale particles embedded in meteorites.
This time, Chinese scientists, starting with high-purity, structurally regular pyrolytic graphite, conducted an atomic-scale "origami" experiment under ultra-high pressure equivalent to 200,000 standard atmospheres and a high temperature of approximately 1300 degrees Celsius. They successfully induced the carbon atom layers in the graphite to slide and recombine in a specific manner, ultimately constructing millimeter-sized hexagonal diamond crystals.
This marks the first time humanity has mastered the ability to synthesize this mysterious material on a macroscopic scale.
Test results show that the synthesized hexagonal diamond not only surpasses traditional diamond in hardness but also exhibits superior shear resistance and oxidation resistance.
It holds promise for developing entirely new cutting tools, more efficient heat dissipation materials, or applications in cutting-edge fields such as quantum sensing.
