Lattice graphite

Fig. XVII-18. Contours of constant adsorption energy for a krypton atom over the basal plane of graphite. The carbon atoms are at the centers of the dotted triangular regions. The rhombuses show the unit cells for the graphite lattice and for the commensurate adatom lattice. (From Ref. 8. Reprinted with permission from American Chemical Society, copyright 1993.)...

It is noted in Sections XVII-10 and 11 that phase transformations may occur, especially in the case of simple gases on uniform surfaces. Such transformations show up in q plots, as illustrated in Fig. XVU-22 for Kr adsorbed on a graphitized carbon black. The two plots are obtained from data just below and just above the limit of stability of a solid phase that is in registry with the graphite lattice [131]. 

Graphitization. Graphitization is an electrical heat treatment of the product to ca 3000°C. The purpose of this step is to cause the carbon atoms in the petroleum coke filler and pitch coke binder to orient into the graphite lattice configuration. This ordering process produces graphite with intermetaHic properties that make it useful in many appHcations. 

Of the chlorine fluorides, only the monofluoride does not intercalate in the neat state. It does, however, intercalate in the presence of HF (S15), BF3, or PFj (S16). Chlorine trifluoride intercalates into graphite with simultaneous fluorination of the graphite lattice (Si5), releasing... 

Figure 4. Depiction of lithium intercalated into the carbon/graphite lattice.

Synthetic graphite flakes, obtained from Timrex Inc., whose morphology has been characterized by a high level of crevices in the facets perpendicular to the basal planes, through which lithium ions are inserted into the graphite lattice (edge planes). 

Figure 7.12 Images at atomic resolution of graphite obtained with scanning tunneling (left) and atomic force microscopy (middle). The graphite lattice contains two types of sites A-sites with a carbon atom neighbor in the second layer and B-sites without a neighbor in the next layer. STM detects the B-sites, whereas the A-sites show up better in AFM. (STM image courtesy of TopoMetrix AFM image courtesy of M.W.G.M. Verhoeven, Eindhoven).

Fig. 10.7 Chirality vector and folding scheme for semiconducting and metallic nanotube (a). Zig-zag, armchair, and chiral nanotubes by rolling-up of the graphite lattice (b) (Reprinted from Terrones 2003. With permission from Annual Reviews)... 

Fig. 5.10. Schematic drawing of graphite lattice structure. After Singer (1989).

The graphite lattice may show stacking faults or defects within the sheets, and, possibly, bending of the sheets (Fig. 2.25). Omission of a carbon atom (voids), or inclusions of noncarbon elements or molecules, disrupts the orderly configuration and inhibits crystallization of carbon as graphite. These impurities act as sites of local strain that directly influence crystallite size, distribution, and orientation within a sample, and in turn affect the physical and chemical characteristics of the material, especially its strength. 

Studies of intercalates have also been reported in recent years. In their EXAFS investigation of Btj in graphite, Heald Stern (1978) have found that while the intercalate retains its molecular structure, the Br-Br distance increases so as to match the periodicity of the graphite lattice. In the series of pseudo-stoichiometric alkali... 

This minimum is responsible for the diamond and graphite lattices with = 109° and 120° respectively having the smallest and second smallest values of the normalized fourth moment, and hence the shape parameter, s, in Fig. 8.7. This is reflected in the bimodal behaviour of their densities of states in Fig. 8.4 with a gap opening up for the case of the diamond cubic or hexagonal lattices. Hence, the diamond structure will be the most stable structure for half-full bands because it displays the most bimodal behaviour, whereas the dimer will be the most stable structure for nearly-full bands because it has the largest s value and hence the most unimodal behaviour of all the sp-valent lattices in Fig, 8.7, We expected to stabilize the graphitic structure as we move outwards from the half-full occupancy because this... 

Our basic example is the graphite lattice sheet, i.e. the 3-valent tiling 6, 3 of the plane by 6-gons. At every vertex of this tiling, we can substitute a 0-elementary (5, 3)-polycycles, either Ei or C3. If we substitute only Ei, we obtain a ( 5, 12, 3)-plane that is 12R0. In order to obtain a ( 5, 13, 3)-plane, we need to substitute a part of the E, by some C3, such that every 6-gon is incident... 

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