| STRUCTURE |
Carbon under pressure characterized The form that graphite takes when compressed at ambient temperatures has long puzzled researchers. The substance's physical properties suggest something akin to diamond, but unlike various forms of diamond, when the so-called cold-compressed graphite returns to ambient pressure, it reverts to conventional graphite. A team led by University of Chicago graduate student Wendy L. Mao now has identified the material's elusive structure using inelastic X-ray scattering spectroscopy [Science, 302, 425 (2003)]. The researchers report that at 17 gigapascals of pressure, half of the C2C -bonds in graphite break and form -bonds with carbon atoms that are directly above or below one another in adjacent layers of graphite. The transient material is superhard and able to scratch diamond, as evidenced by cracks the material left in the diamond anvils of Mao's sample gasket. The researchers speculate that this reversible change in hardness could have intriguing applications as a pressure-dependent structural component. |
|
Want more information ? Interested in the hidden information ? Click here and do your request. |