Graphite hexagonal

Carbon blacks are synthetic materials which essentially contain carbon as the main element. The structure of carbon black is similar to graphite (hexagonal rings of carbon forming large sheets), but its structure is tridimensional and less ordered. The layers of carbon blacks are parallel to each other but not arranged in order, usually forming concentric inner layers (turbostratic structure). Some typical properties are density 1.7-1.9 g/cm pH of water suspension 2-8 primary particle size 14-250 nm oil absorption 50-300 g/100 g specific surface area 7-560 m /g. 

Molybdenum disulhde (M0S2), graphite, hexagonal boron nitride, and boric acid are examples of lamella materials commonly applied as solid lubricants. The self-lubricating nature of the materials results from the lamella crystalline structure that can shear easily to provide low friction. Some of these materials used to be added to oils and greases in powder forms to enhance their lubricity. Attention has been shifted in recent years to the production and use of nanosize particles of M0S2, WS2, and graphite to be dispersed in liquid lubricants, which yields substantial decreases in friction and wear. 

Carbon nanotubes are rolled up tubes of carbon made up of a graphitic hexagonal structure. They can either be open or capped at the end by carbon pentagons which give all Fullerenes their closed curvature. 

Cubic BN is usually manufactured at about 5 GPa and 1500°C from a mixture of graphitic hexagonal BN and a catalyst solvent such as lithium or magnesium nitride. Many other catalyst solvent systems have been found and most of them involve a nitride-forming element. As pressure and temperature increase, the catalyst requirements relax as with carbon. 

Figure 5. An STM image of a HOPG surface immersed in water. The graphite hexagonal lattice is clearly distinguished. Reprinted with permission from Ref. 58, Copyright (1986) AAAS.

Figure 63. Schematic picture of the incommensurate pinwheel phase of CO on graphite found in the LEED experiments below about 35 K at 1.13 monolayers this plot is very similar to the projection of the molecules onto the (111) plane of bulk a-CO. The actual orientation of the molecules is not known and the leftmost pin molecule is arbitrarily centered in a graphite hexagon. (Adapted from Fig. 7 of Ref. 389.)...

Energy minimizations of clusters with three to six molecules show that ( X v3)/ 30° registered structures are preferred [17]. A single molecule is not located with its center of mass on top of the center of a graphite hexagon. Instead it is displaced in the direction of the saddle point so that the overall charge density of the molecule illustrated in Fig. b is more centered. 

Secondary bonding is also important in many ceramics. The most familiar properties of graphite, hexagonal-BN, and clay minerals are determined by the presence of weak secondary bonds. 

Figure 20 shows the martensitic transformation, by compression in the c-direction and in-plane buckling, of two crystalline forms of graphite. Hexagonal graphite,... 

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