2.10 - Graphite: Properties and Characteristics

Abstract

Graphite is a truly unique material. Its structure, from the nano- to the millimeter scale, gives it remarkable properties, which facilitate numerous and diverse applications. Graphite bond anisotropy, with strong in-plane covalent bonds and weak van der Waals type bonding between the planes, gives graphite its unique combination of properties. Easy shear of the crystal, facilitated by weak interplanar bonds, allows graphite to be used as a dry lubricant and is responsible for the substance’s name! The word ‘graphite’ is derived from the Greek ‘to write’ because of graphite’s ability to mark writing surfaces. Moreover, synthetic graphite contains porosity spanning many orders of magnitude in size within its structure. The thermal closure of these pores profoundly affects the properties, for example, graphite strength increases with temperatures in excess of 2200°C. Consequently, graphite is utilized in many high-temperature applications. The basic physical properties of graphite are reviewed here. Graphite applications include the following: metallurgical, aluminum, and steel production, single crystal silicon production, and metal casting; electric motor brushes and commutators; mechanical seals, bearings, and bushings; and nuclear applications (see Chapter 4.10, Radiation Effects in Graphite). Here, we discuss the structure, manufacture, and properties of graphite.