Diamonds Are a Physicist's Best Friend
Hunting for novel forms of carbon, scientists have unexpectedly discovered a new way to make an old form--diamonds. Although nobody is going to pop the question with these microscopic creations, the new process promises cheaper and purer diamonds for industrial use than those made by current techniques. And the finding suggests that carbon behaves differently at super high temperatures than theorists had thought.
Mass-produced diamonds are used in, among other things, cutting tools, microelectronics, and optics. One production method, developed in the 1960s, recreates the high-pressure conditions that form natural diamonds deep in the earth--a costly and dangerous process. A low-pressure method, developed in the 1980s, forms a thin diamond film by shooting a current through carbon and hydrogen gases, but the results are impure.
A team led by theoretical physicist J.-C. Charlier of the Université Catholique de Louvain in Belgium isn't in the diamond business--they're in the buckyball and nanotube business. They create the geodesic dome-shaped carbon balls and hollow carbon tubes by shooting a current through graphite electrodes in a vacuum. Jacking up the current to five times the normal amperage one day, postdoc A. V. Palnichenko found that instead of some kin of buckyballs or nanotubes, a diamond grit consisting of hundreds of 10-micrometer-wide diamonds and a smattering of larger, 100-micrometer-wide ones had landed on the metal surface below, they report in the 11 November Nature.
According to Charlier, the diamonds form at a rate 1000 times faster than observed for carbon vapor deposition. No one expected to create diamonds under these conditions, says Massachusetts Institute of Technology physicist Mildred Dresselhaus. "The paper will attract a lot of attention," she says. Because of the findings, notes Dresselhaus, physicists may have to rethink the textbook phase diagrams that map out how carbon should behave at different temperatures and pressures. The team is now attempting to discharge the electrodes longer to make larger diamonds, but don't look for them in your jewelry store any time soon.