ABSTRACT
The anisotropy of the crystal structure of graphite also introduces important phenomena. For instance, in polycrystalline graphite, the crystallites can be aligned as in highly oriented pyrolytic graphite, or more-or-less randomly oriented as in some nuclear-grade materials. Apart from its scientific interest, the electrical conductivity of carbon-based materials is of great importance because of its industrial applications. Brushes for electrical motors are constructed of polycrystalline graphite because of a combination of electrical and lubricating characteristics. High-temperature applications include furnace cores and electrodes for metallurgical applications. The theoretical problem of the change of electronic structure as a graphite changes to a defective turbostratic carbon is unsolved, McClure and Ruvald showed that the energy bands near the Fermi level of ideal turbostratic graphite were essentially the same as those of a single sheet of graphite. Conduction processes in disordered materials are very different from those in crystalline, since the carriers can be localized by disorder.
