Graphite is a special polycrystalline material. Graphite crystal is a hexagonal ring grid structure composed of carbon precursor
Multilayer stack (Fig. L-2). In the crystal structure of graphite, the layer spacing between the basal planes is relatively large, located at
The carbon atoms on the adjacent base plane are bonded by van der Waals force, the bonding force between atoms is weak, and the interlayer spacing is o.3354nm,
The bond energy between layers is only 5.4kj/toolt7, s, 91, so the shear strength of graphite crystal along the base plane is poor, which is easy to
Interlayer cleavage occurs: the carbon atoms located in the same basic plane are oriented at an angle of 1200 to each other in the plane
The adjacent carbon atoms are covalently bonded to form a hexagonal lattice plane with graphite characteristics, and the C-C bond length is 0.141
The average bond energy of C-C bond is 627kj / mol. Therefore, the crystal structure of graphite has significant anisotropy.

Figure 1.2 graphite crystal structure: (a) schematic diagram of ideal structure: (b) hexagonal ring structure of graphite crystal [71

Fig．1-2 Graphite Crystal structure：(a)Ideal structure； (b)Hexagonal loop structure