Harder Than A Diamond

A 2-millimeter chunk of nanotwinned cubic boron nitride. Photo: Courtesy of Yongjun Tian

Scientists claim their nanotwinned cubic boron nitride is:

How do you design industrial tools that can top the most heavy-duty diamond-tipped devices? Easy: you create a new material that’s even harder than diamond.
Yes, it’s an oft-misstated “fact”: Diamond is the hardest material in the world. That title has been contested for some time now, and a paper published this month in Nature offers yet another contender.
“Ultrahard nanotwinned cubic boron nitride,” describes how researchers from the University of Chicago, the University of New Mexico, Yanshan University, Jilin University, and Hebei University of Technology compressed a form of boron nitride particles to an ultrahard version.
The transparent nuggets that resulted rivaled — and even exceeded — diamond in their hardness, according to tests run by the researchers. With a Vickers score of 108 GPa, it surpasses synthetic diamond (100 GPa) and more than doubles the hardness of commercial forms of cubic boron nitride.
The secret is in the nanostructure. Yongjun Tian and the other researchers started with onion-like boron nitride particles shaped a bit like a flaky rose — or, as Tian describes them, like Matryoshka dolls. When they compressed them at 1,800 Celsius and 15 GPa (around 68,000 times the pressure in a car tire), the crystals reorganized and formed in a nanotwinned structure.

Wow, stuff like that makes me feel even dumber than normal.