Graphite compounds

Metal-graphite intercalation compounds are best known with alkali elements. Since intercalation of the alkaline-earth metals is possible only in liquid ammonia those phases all contain NH3. The same is true for A1 and Ln (La, Ce, Sm, Eu). 

Metal-graphite intercalation compounds, n = stage, number of graphite layers per metal layer. 4 = chemical identity period along the hexagonal axis 

Introduction of the metal layers leads, for all stages, to the same increase AIciM) in the distance between adjacent carbon planes  

Therefore, the identity period along the hexagonal axis can easily be calculated, or in turn the stage can be determined from the experimental c value  

Experimental results are in agreement with the assumption that formation of these compounds involves an electron transfer from the alkali to the host graphite lattice. The anomalously high diamagnetism of pure graphite changes into Pauli 

Alkali metals and alkaline-earth metals in liquid ammonia may also penetrate the graphite structure. Recently, for example, such compounds 

An important question concerning these compounds is, What factors govern the ratio of carbon to interstitial species in these compounds . No simple answer to this is at present available. 

As with the hydrides (Chap. 2), the carbides are divided into three classes—the covalent, the saltlike, and the metallic (or interstitial). The volatile covalent carbides (for example, CC14, (CN)2, CH4, and CS2) are discussed elsewhere of the nonvolatile covalent carbides, silicon carbide (carborundum, SiC), is by far the most important. Although there are three known crystal forms of this compound, we may, for simplification, imagine it as a diamond structure in which every alternate carbon atom is replaced by a silicon atom. Thus it is not surprising that this compound is almost as hard and chemically inert as is diamond itself. 

Almost all of the saltlike carbides contain the feC linkage and therefore may be called acetylides. The commercially important calcium carbide, CaC2, prepared by the high-temperature reaction of calcium oxide and carbon is typical of this class. When this compound is added to water, the strongly basic carbide ion, removes the hydrogen ions 

The other alkaline earth metals form carbides of this type, as do the alkali metals, the coinage metals, certain of the rare earths, and various other metals (Zn, Cd, and U). 

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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. 

G. R. Henning, "Properties of Graphite Compounds," Proceedings of the Second Conference on Carbon, University of Buffalo, Buffalo, N.Y., 1956. 

Twenty years ago, Walter Riidorff wrote a review for this series entitled "Graphite Intercalation Compounds Oil). It was one of four definitive articles to come out in 1959 and 1960 (HI, Cl, Ul), a period of intense activity in graphite research. We have now again reached the "fever pitch, with not only the appearance of several new articles El, H2, Wl) but also the convening of the first international conference dedicated exclusively to graphite compounds (H3). In the following, we shall concentrate on work performed between 1974 and the present. 

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 number of general, synthetic techniques have been developed for preparing graphite compounds. 

Graphite compounds have been described as catalysts for ammonia synthesis from nitrogen and hydrogen (14, Pll), for Fischer-Tropsch chemistry M13, R14), for paraffin isomerization iR15), and for Friedel-Crafts chemistry (07). 

Figure 123. PCM-graphite compound produced from mixing PCM with expanded graphite...

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

Graphite compounds, 12 777-778 Graphite crystal lattice, 17 46 Graphite crystals, 12 714, 776 Graphite-diamond equilibrium line, 8 531-532... 

Avdeev VV, Zharikov OV, Nalimova VA, Pal nichenko AV, Semenenko KN (1986) Superconductivity of the layered potassium-graphite compounds CgK and C4K. Pis ma Zh Eksp Teor Fiz 43 376—378... 

In recent years a set of interesting compounds known as graphitic compounds have been developed. In these compounds different atoms have been fitted in between the layers of carbon atoms to produce a substance with a greater electrical conductivity than pure graphite. Graphite is also used as a component in certain sports equipment, such as tennis and squash rackets. 

The first cyclotrisilene 48 is synthesized by the reduction of dibromochlorosilane 90 with potassium graphite. Compound 48 is isolated as air-sensitive dark red crystals in 65% yield 24... 

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. 

Ohana, I., D. Vaknin, H. Selig, Y. Yacoby, and D. Davidov. 1987. Charge transfer in stage-1 OsF6- and MoF6-intercalated graphite compounds. Phys. Rev. B 35 4522-4525. 

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