Carbide-derived carbon synthesis

Novel, inexpensive synthesis routes for producing materials with precisely controlled nanotexture must be developed to improve the performance of batteries and electrochemical capacitors, as well as to enable new electrochemical applications of carbons. Two alternatives, carbide-derived carbon (CDC) and templated carbon, have shown a promise to offer the requisite control necessary to push device performance to the next level and will be explored in this chapter. 

Yushin, G., Hoffman, E., Nikitin, A., Ye, H., Barsoum, M.W., and Gogotsi, Y. Synthesis of nanoporous carbide-derived carbon by chlorination of titanium silicon carbide. Carbon 43, 2005 2075-2082. 

Janes, A. Synthesis and characterization of nanoporous carbide-derived carbon by chlorination of vanadium carbide. Carbon 45, 2007 2717-2722. 

Wang, H.L. and Gao, Q.M. Synthesis, characterization and energy-related applications of carbide-derived carbons obtained by the chlorination of boron carbide. Carbon Al, 820-828, 2009. 

Erdemir, A. et al. Synthesis and ttibology of carbide-derived carbon films. International Journal of Applied Ceramic Technology 3, 236-244, 2006. 

It has been previously shown that selective etching of carbides is an attractive technique for the synthesis of various carbon structures. Carbon produced by extraction of metals from carbides is called carbide-derived... 

Finally, cobalt carbide-carbonyl clusters have recently been isolated through a two-step synthesis. First of all, the well-known Co3(CO)9CCl is prepared from Co2(CO)8 and CCh, and then the hexanuclear carbide dianion [Co6(CO)i5C]2- is obtained in good yields (9) by further reaction with Xa[(, o(CO)4] in diisopropylether [see Eqs. (18) and (19)]. Further redox condensation between [Oo6(CO)i5C]2-and Co4(CO)i2 [see Eq. (11)] gives the square antiprismatic octanuclear cluster [Cdo8(Cdt )i8 C]2- (13). Both these carbide derivatives, as well as all of the other cobalt high nuclearity clusters, are sensitive to air and react with carbon monoxide at atmospheric pressure. 

Dash RK, Yushin G, Gogotsi Y et al (2005) Synthesis, structure and porosity analysis of microporous and mesoporous carbon derived from zirconium carbide. Micropor Mesopor Mater 86(l-3) 50-57... 

Although a great variety of chlorinated hydrocarbons of the lower carbon numbers had been well known and produced in small quantities for many years, the large scale manufacture and use of such compounds other than chloroform and carbon tetrachloride is a fairly recent development. And although synthesis, particularly of the two-carbon derivatives, has in great measure depended on acetylene from calcium carbide, more and more reliance has been placed on petroleum raw materials in this field in the last few years. 

The thermodynamics of the above-elucidated SiC/C and SijN Si composites are determined by the decomposition of silicon carbide and silicon nitride, respectively, into their elements. The chemistry of ternary Si-C-N composites is more complex. If producing Si-C-N ceramics for applications at elevated temperature, reactions between carbon and silicon nitride have to be considered. Figure 18.2, which exhibits a ternary phase diagram valid up to 1484°C (1 bar N2) displays the situation. The only stable crystalline phases under these conditions are silicon carbide and silicon nitride. Ceramics with compositions in the three-phase field SiC/Si3N4/N are unknown (this is a consequence of the thermal instability of C-N bonds). Although composites within the three-phase field SiC/Si3N4/Si are thermodynamically stable even above 1500°C, such materials are rare. The reasons are difficulties in the synthesis of the required precursors and silicon melting above 1414°C. The latter aspect is of relevance, since liquid silicon dramatically worsens the mechanical properties of the derived ceramics. 

Carbon forms play important roles as intermediates, catalyst additives and deactivating species in Fischer-Tropsch synthesis on iron catalysts. Deactivation may be due to poisoning or fouling of the surface by atomic carbidic carbon, graphitic carbon, inactive carbides or vermicular forms of carbon, all of which derive from carbidic carbon atoms formed during CO dissociation (ref. 5). While this part of the study did not focus on the carbon species responsible for deactivation, some important observations can be made to this end. 

Here Z is a Ni surface site. The equation they derive is complex but can be simplified (see Table 4) for full-scale application. These workers point out that the same equation can be derived from a mechanism involving surface carbon as an intermediate similar to carbide theories for Fischer-Tropsch synthesis. In that case steps (b) and (c) in the above equation would be replaced by (b ) and (c ). 

Ethylene from cracking of the alkane gas mixtures or the naphtha fraction can be directly polymerized or converted into useful monomers. (Alternatively, the ethane fraction in natural gas can also be converted to ethylene for that purpose). These include ethylene oxide (which in turn can be used to make ethylene glycol), vinyl acetate, and vinyl chloride. The same is true of the propylene fi action, which can be converted into vinyl chloride and to ethyl benzene (used to make styrene). The catalytic reformate has a high aromatic fi action, usually referred to as BTX because it is rich in benzene, toluene, and xylene, that provides key raw materials for the synthesis of aromatic polymers. These include p-xylene for polyesters, o-xylene for phthalic anhydride, and benzene for the manufacture of styrene and polystyrene. When coal is used as the feedstock, it can be converted into water gas (carbon monoxide and hydrogen), which can in turn be used as a raw material in monomer synthesis. Alternatively, acetylene derived from the coal via the carbide route can also be used to synthesize the monomers. Commonly used feedstock and a simplified diagram of the possible conversion routes to the common plastics are shown in Figure 2.1. 

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