Compounds metal-graphite

The alkah metal—graphite compounds formed by graphite absorption of the fused metals Na, K, Rb, and Cs, represent a special type of metal—carbon compound (6). These intercalation compounds having formulas MCg are brown MC are gray and MC q are strongly graphitic. 

Issi, J. -P., Transport properties of metal chloride acceptor graphite intercalation compounds. In Graphite Intercalation Compounds,... 

Cj(K prepared — the first alkali metal-graphite intercalation compound. 

Figure 8.16 Layer-plane sequence along the c-axis for graphite in various stage I -5 of alkali-metal graphite intercalation compounds. Comparison with Fig. 8.15 shows that the horizontal planes are being viewed diagonally across the figure. /,. is the interlayer repeat distance along the c-axis.

Alkali-metal graphites are extremely reactive in air and may explode with water. In general, reactivity decreases with ease of ionization of M in the sequence Li > Na > K > Rb > Cs. Under controlled conditions H2O or ROH produce only H2, MOH and graphite, unlike the alkali-metal carbides M2C2 (p. 297) which produce hydrocarbons such as acetylene. In an important new reaction CgK has been found to react smoothly with transition metal salts in tetrahydrofuran at room temperature to give the corresponding transition metal lamellar compounds ... 

Thermodynamic information has been obtained in different stages of graphite bisulfate (A5). The results have been interpreted in terms of a model previously applied to alkali-metal-graphite compounds. Part of... 

A great deal of excitement has been generated by the assertion that some intercalation compounds of graphite possess a conductivity greater than that of copper (VIO, F13, Til). Much of this work was based upon earlier researches by Ubbelohde, who found that the a-axis conductivity of the semi-metal graphite increases, and develops a me-... 

The intercalation compounds of lithium with graphite are very different in their behavior from intercalation compounds with oxides or halcogenides. Intercalation processes in the former compounds occur in the potential region from 0 to 0.4 V vs. the potential of the lithium electrode. Thus, the thermodynamic activity of lithium in these compounds is close to that for metallic lithium. For this reason, lithium intercalation compounds of graphite can be used as negative electrodes in batteries rather than the difficultly of handling metallic lithium, which is difficult to handle. 

Alkali-metal-graphite compounds Williams, N. E., private comm., 1968... 

X-Ray studies confirm that platinum crystallites exist on carbon supports at least down to a metal content of about 0.03% (2). On the other hand, it has been claimed that nickel crystallites do not exist in nickel/carbon catalysts (50). This requires verification, but it does draw attention to the fact that carbon is not inert toward many metals which can form carbides or intercalation compounds with graphite. In general, it is only with the noble group VIII metals that one can feel reasonably confident that a substantial amount of the metal will be retained on the carbon surface in its elemental form. Judging from Moss s (35) electron micrographs of a reduced 5% platinum charcoal catalyst, the platinum crystallites appear to be at least as finely dispersed on charcoal as on silica or alumina, or possibly more so, but both platinum and palladium (51) supported on carbon appear to be very sensitive to sintering. 

Both of the potassium and polybromide intercalation compounds are good conductors of electricity. In the potassium inlercalam. the electrons in the conduction band can carry the current directly, as in a metal. In the compounds of graphite with polybromide. holes in the valence band conduct by the mechanism discussed previously for semiconductors (Chapter 7). 

The synthesis of metal graphite compounds is carried out by the reduction of layer graphite compounds and metal chlorides by using different reducing agents such as, for instance, solutions of aromatic anion radicals in THF, metallic sodium in liquid ammonia, complex boron and aluminum hydrides, and vapor or liquid potassium. As a result, the complex compounds containing one (Sn, Co, Mn, Cr, Mo, W, Pd) and two (Fe-Mo, Fe-W, or Mo W) metals were synthesized. 

Alstrom, P. 1986. Electronic properties of first-stage heavy alkali metal graphite intercalation compounds. Synth. Metals 15 311-322. 

Saito, M. and A. Oshiyama. 1986. Self-consistent band structures of first-stage alkali-metal graphite intercalation compounds. J. Phys. Soc. Jpn. 55 4341-4348. 

Gunasekara, N., T. Takahashi, F. Maeda, T. Sagawa, and H. Suematsu. 1988. Angle-resolved ultraviolet photoemission study of first stage alkali-metal graphite intercalation compounds. Z. Phys. B 70 349-355. 

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