Carbon as graphite

FIGURE 1.61 The Croup 14/IV elements. From left to right carbon (as graphite), silicon, germanium, tin, and lead. 

As an example of Hess s law, let s consider the oxidation of carbon as graphite, denoted C(gr), to carbon dioxide ... 

Because amorphous carbon as graphite heats up strongly under MW irradiation [4], its use as a sensitizer has been widely reported [5-10] (Sect. 7.1). Recently, MW-as-sisted esterification of carboxylic acids with alcohols was performed on activated carbon in good yields (71-96%) [98]. For our part, when charcoal powder was used as a support, we had difficulty in desorbing the reaction products [15]. Even with a continuous extractor, the desorption was never quantitative. The desorption of reaction products from graphite powder is much easier than from amorphous carbon powder. 

Carbon, as graphite, has strong electrical conductivity properties. It is an important component in electrodes used in a variety of devices, including flashhght cells (batteries). Amorphous carbon has some superconduction capabilities. 

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. 

The direct reaction of carbon as graphite or activated carbon [221, 222] with NO in the presence of excess oxygen is a high-temperature process operating with full NO conversion only at about 875 K. The parallel course of the activation curve for NO removal and for oxidation is taken as indication [224] that oxygen etches active sites into the carbon which decompose NO. 

Table 31. Enthalpy and energy of formation of explosive and propellant components and their number of atoms per kg. Reference Temperature 298.15 K = 25 °C = 77 °F reference state of carbon as graphite. 

Rubber Company Handbook (Weast, 1987) is one of the more commonly available sources. More complete sources, including some with data for a range of temperatures, are listed in the references at the end of the chapter. Note that many tabulations still represent these energy functions in calories and that it may be necessary to make the conversion to Joules (1 cal = 4.1840J). Because of the definition of the energy of formation, elements in their standard state (carbon as graphite, chlorine as CI2 gas at one bar, bromine as Br2 liquid, etc.) have free energies and enthalpies of formation equal to zero. If needed, the absolute entropies of substances (from which AS may be evaluated) are also available in standard sources. 

Note that while carbon (as graphite) is a high energy fuel, it often seems not to be. This may be because carbon does not melt (like metals) before combusting. 

Figure 7.16 Nonmetals are diverse in their appearances. Shown here are (clockwise from left) carbon as graphite sulfur, white phosphorus (stored under water), and iodine. 

Data from [137] [375] for carbon as graphite. Data from [425] for carbon as whisker... 

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