Carbon-sulfur composites

The surface area of the material thus prepared decreases from 65 to 8.9 m g.  

The composite prepared by thermal treatment delivers a high initial discharge capacity of 935 mAh g , and this is maintained at 500 mAh g after 50 cycles. 

The improvement in initial discharge capacity and cydeabiUty is due to the confinement of polysulfides in the nanopores of AB [47]. 

Carbon blacks, such as SP and AB, have relatively low surface areas of 60-70 g which hmits the dispersion of sulfur. Other carbon materials 

Coating sulfur onto the surface of different carbon materials improves the dispersion of sulfur on the composite materials. The S-coated-MWCNTs are prepared through capillarity behavior between liquid sulfur and MWCNTs. With a low surface tension of 61 mN m, hquid sulfur wets and fills carbon nanotubes 

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Other, innovative approaches to the making of a carbon/sulfur composite structure have been put forward. Of these, we can cite the use of a me soporous carbon stmcture (alignment of carbon tubes) which offers a high volume of pores, good electronic conductivity and the possibility of confining the active material in channels left free between the tubes (Figure 9.7). 

Figure 9.7. Diagram of the principle ofpreparation of the carbon/sulfur composite ...

Wang D-W, Zeng Q, Zhou G, Yin L, Li F, Cheng H-M, Gentle IR, Lu GQM (2013) Carbon-sulfur composites for Li-S batteries status and prospects. J Mater Chem A 1 9382-9394... 

A catalyst that can prevent polysulfide anions from precipitating as solids would be highly desirable. While a catalyst still remains to be discovered, several approaches, common in catalysis, have been employed to improve the cycling performance of lithium-sulfur batteries. For example, new electrolytes [18-21], protective films [22], solubiHzed sulfides [23], and new cathodes [24] have been developed. However, the performance results have either not been reported or have been found to be inadequate for practical applications. For example, a disordered mesoporous carbon-sulfur composite in conjunction with ionic liquid electrolytes has been fabricated. This system achieves high initial capacity that deteriorates rapidly [20]. 

Figure 23.1 Carbon-sulfur composite (top) and Li charging-discharging (bottom) [25].

Improvement of qrcleability is also observed on the carbon sulfur composite prepared by sputtering method [57]. 

N. Jayaprakash, J. Shen, S.S. Moganty, A. Corona and L.A. Archer, Porous hollow carbon sulfur composites for high-power lithium-sulfur batteries, Angew. Chem. Int. Ed. 50, 2011,5904-5908. 

Incompletely Characterized Carbon Sulfides. A poorly characterized black soHd, known as carsul, occurs as a residue ia sulfur distillation or as a precipitate ia molten Frasch sulfur (12,13). Although this material may approach the composition of a carbon sulfide, it is more likely also to contain some chemically bound hydrogen and possibly other elements. Carbon—sulfur surface compounds of the formula C S, where xis greater than 4,... 

Schoeninger, M.J. and DeNiro, M.J. 1984 Nitrogen and carbon isotopic composition of bone collagen from marine and terrestrial animals. Geochimica et Cosmochimica Acta 48 625-639. Schuette, S. A., Hegsted, M., Zemel, B. and Linkswiler, H.M. 1981 Renal acid, urinary cyclic AMP, and hydroxyproline excretion as affected by level of protein, sulfur amino acids and phosphorus intake. Journal of Nutrition 111 2106-2116. 

The equations for the isotope pairs 2H/1H, 13C/12C, and 34S/32S parallel the relations for 180/160, except that the reference species for carbon and sulfur are CO2 and H2S, rather than solvent water. Carbon and sulfur compositions are many times reported with respect to the PDB (Pee Dee belemnite) and CDT (Canyon Diablo troilite) standards, instead of SMOW. It makes little difference which standard we choose in applying these equations, however, as long as we carry a single standard for each element through the calculation. 

Macias, E.S. Radcliff, C.D. Lewis, C.W. Sawaki, C.R., Proton-Induced y-ray Analysis of Atmospheric Aerosols for Carbon, Nitrogen, and Sulfur Composition, Anal. Chem., 1978, 5, 1120. 

Carbon-, nitrogen-, and sulfur-containing species account for most of the mass of aerosol particles. In spite of years of effort by many investigators, the exact chemical forms of carbon, sulfur, and nitrogen in these particles are not known nor are the formation mechanisms of these species known with certainty. There are many reasons for this situation, including the complexity of the system and the dependence of the apparent chemical composition on the analytical methods used. For example, wet chemical analyses of sulfur and nitrogen species report only ions in solution. These ions, however, may be originally water soluble (e.g., sulfate and ammonium from ammonium sulfate), or they may be ionic products of hydrolyzable species such as amides (1). Of course, insoluble species will not be detected by wet chemical techniques. 

Figure 10.12. A. Carbon isotopic composition of major groups of higher plants and autotrophic microorganisms compared with oxidized carbon (CO2, HCO3, CC>32 )- The triangles are mean values. (After Holser et al 1988 Schidlowski, 1988). B. Sulfur isotopic composition of bacteriogenic sulfide in modern marine anaerobic sediments (open bars, 1-6) and in the Permian Kupferschiefer (black bar, 7) compared with oxidized sulfate of modem (1-6) and Permian seawater (+11 %o). The black triangles are mean values. (After Holser et al., 1988.)...

Pimenov NG, Neretin LN (2006) Composition and activities of microbial communities involved in carbon, sulfur, nitrogen and manganese cycling in the oxic/anoxic interface of the Black Sea. In Neretin LN (ed) Past and present water column anoxia. NATO Sciences Series. Springer, Dordrecht, p 501... 

Work on potential pollution sources requires a thorough knowledge of the composition of potential pollutants. Maximum parameters should be measured on every industrial effluent that leaves a factory and the fluid that is formed in each landfill. The parameters to be measured include temperature, pH, major dissolved ions, trace elements (mainly metals and metal compounds), organic compounds, and isotopic compositions of hydrogen, oxygen, carbon, sulfur, and nitrogen. To perform such analyses, special laboratories have to be contacted. In certain cases the main product may serve as the label, and in other cases the labels are supplied by accompanying compounds, which in themselves may not be poisonous. 

Figure 6 Volatile/refractory element ratio-ratio plots for chondrites and the silicate Earth. The correlations for carbonaceous chondrites can be used to define the composition of the Earth, the Rb/Sr ratio of which is well known, because the strontium isotopic composition of the BSE represents the time-integrated Rb/Sr. The BSE inventories of volatile siderophile elements carbon, sulfur, and lead are depleted by more than one order of magnitude because of core formation. The values for Theia are time-integrated compositions, assuming time-integrated Rb/Sr deduced from the strontium isotopic composition of the Moon (Figure 8) can be used to calculate other chemical compositions from the correlations in carbonaceous chondrites (Halliday and Porcelli, 2001). Other data are from Newsom (1995).

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