Graphite two-dimensional infinite sheets

The major use for graphite nowadays is for carbon fibers (to reinforce composites) produced either from pitch or from polymers such as polyacrylonitrile. Graphitization of these materials is performed stepwise by oxidation at 250° for losing much of the hydrogen, followed by carbonization in the absence of oxygen at 800°, and then by graphitization at 1400°-2500°. 

According to the stacking of graphene sheets, two forms of graphite are known, namely hexagonal (ABAB... type) and rhombohedral (ABCABC... type). 

Since graphite is the thermodynamically favored allotropic form of elemental carbon (by 0.2 kcal/ mol relative to diamond), one can gradually convert diamond into graphite on heating at 1000° at normal pressure in the absence of air (cf. also item 4.2 below). 

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