|Huge slabs of pyrolytic graphite.|
These massive slabs of pure pyrolytic graphic must have cost someone (Martin-Marietta according to the label) a pretty penny ($200 each in 1990, according to the seller). Pyrolytic graphic is the same as regular graphite (sheets of hexagonally bonded carbon atoms), but in pyrolytic graphite the sheets are all arranged in the same direction, in a flat pancake. In normal graphite there are zones of order like that, but as a whole the orientation of the sheets is random, making ordinary graphite an isotropic material. Pyrolytic graphite on the other hand has a definite directionality to it, with, for example, widely different diamagnetism in the direction of the sheets v.s. perpendicular to them. It can also be cleaved into thinner and thinner layers like slate or mica.
Contributor: Theodore Gray
Acquired: 21 November, 2003