Nanomaterial Rivals Hardness of Diamond
January 18, 2013
By JOHN MATSON | SCIENTIFIC AMERICAN | JANUARY 18, 2012
It’s only a matter of time before a movie villain pulling off the crime of the century needs a cutting tool that is harder than anything else on Earth. Perhaps it’s a burglary that involves cutting into a case made of diamond—which, as we have all learned from countless heist films, is itself hard enough to cut glass. Or maybe it’s a devious scheme predicated on boring a hole into the depths of the planet with the world’s hardest drill bit.
Whatever the plot details, scientifically minded scriptwriters would do well to turn their attention to cubic boron nitride, a material that in many ways resembles diamond. Boron nitride can be compressed into a superhard, transparent form—but unlike diamond and many other materials known for their extreme hardness, it is based not on carbon but on a latticework of boron and nitrogen atoms. Computer simulations have indicated that a rare crystalline form of boron nitride would resist indentation even better than diamond if it could be synthesized into large samples, and laboratory experiments have shown that more attainable forms of the stuff already approach the hardness of diamond.
Now a new set of experiments on a nanostructured form of boron nitride have yielded even greater measures of hardness than before. The new material exceeds that of some forms of diamond, according to the authors of a study reporting the findings in the January 17 issue of Nature. (Scientific American is part of Nature Publishing Group.) But quantifying the properties of superhard materials is a tricky business, and at least one leading researcher remains unconvinced that the study’s authors have found anything new.