Fig. 15. A schematic model illustrating the concepts of basic structural unit, BSU, and local molccular ordering, LMO [e.g., 116].

The Oberlin group have elaborated the mechanism of graphitisation as shown in Fig. 16. Earlier work on graphitisation mechanisms has been reviewed on several occasions [117-119]. In stage 1, up to HTT - 1000 °C, the carbons contains flat BSU with a high degree of misorientation. Between 1000 and 1500 °C (stage 2) the BSU grow thicker and columnar arrays of BSU (like stacks of coins) develop with misoriented BSU trapped between them. In stage 3, between HTT — 1500 to 2000 °C the misorientation between the columns of BSU decreases, so that extensive, but distorted, carbon layer planes can form by coalescence of adjacent BSU. The final stage, above HIT = 2000 °C, involves the annealing out of defects within the distorted carbon layer planes, so that perfect flat carbon layer planes are produced that allow the formation and growth of graphite crystallites.

Fig. 16. The mcchanism of graphitisation (Reprinted from [116] by courtesy of Marcel Dckker Inc.
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