William Atkins
Sunday, 08 March 2009 21:48
Science -
Biology
Page 1 of 3
According to research by U.S. and Chinese researchers, the world’s hardest material is no longer diamond or nanomaterials. Lonsdaleite has taken over the top hardness spot here on Earth, and wertzite boron nitride is the second hardest material known on Earth. Even though both are very hard, they are also very hard to find in nature.
The February 6, 2009 article “
Harder than Diamond: Superior Indentation Strength of Wurtzite BN and Lonsdaleite” highlights the work performed by Zicheng Pan and Hong Sun (Shanghai Jiano Tong University, Shanghai, China), and Yi Zhang and Changfeng Chen (University of Nevada, Las Vegas, U.S.A.).
The article appears in the journal
Physical Review Letters (volume 102, 055503 (2009) [4 pages]), a journal of the American Institute of Physics (AIP).
They state in the abstract to their paper,
“Recent indentation experiments indicate that wurtzite BN (w-BN) exhibits surprisingly high hardness that rivals that of diamond.”
They performed their experiment in this way:
“Here we unveil a novel two-stage shear deformation mechanism responsible for this unexpected result."
"We show by first-principles calculations that large normal compressive pressures under indenters can compel w-BN into a stronger structure through a volume-conserving bond-flipping structural phase transformation during indentation which produces significant enhancement in its strength, propelling it above diamond's.”
In other words, the Chinese and American researchers probed w-BN to see how its atoms responded to the prodding of the finely tipped instrument. They found that w-BN withstood the prodding better than diamond.
Page two continues with more on w-BN, and even more on an even harder material, longdaleite.
