Carbon onions put on the pressure - layers of soft graphic used in diamond formation - Materials Science - Brief Article

Science News, August 31, 1996

A new technique of making diamonds out of soft graphite generates the huge pressures needed by simply letting carbon itself do the squeezing.

Florian Banhart and Pulickel M. Ajayan at the Max Planck Institute for Metal Research in Stuttgart, Germany, formed diamonds less than 50 nanometers in diameter in the cores of carbon onions, small particles consisting of multiple concentric layers of graphite. Heating the onions to about 700#161#C and bombarding them with an electron beam triggered atomic rearrangement in the carbon layers, causing them to contract, the researchers say. "In effect, the carbon onions act as nanoscopic pressure cells for diamond formation," they note in the Aug. 1 Nature.

At this point, it's unclear whether larger diamonds could be made this way, but the method provides scientists with a window into how graphite changes to diamond. Also, studies are under way to see if other materials can be slipped into the carbon onions and then squeezed, Banhart says.