Structure of carbon material

Chapter 11 reports the use of carbon materials in the fast growing consumer eleetronies applieation of lithium-ion batteries. The principles of operation of a lithium-ion battery and the mechanism of Li insertion are reviewed. The influence of the structure of carbon materials on anode performance is described. An extensive study of the behavior of various carbons as anodes in Li-ion batteries is reported. Carbons used in commereial Li-ion batteries are briefly reviewed. 

Until recently, synthesis of nanostructured carbon materials was usually based on very harsh conditions such as electric arc discharge techniques [1], chemical vapor deposition [2], or catalytic pyrolysis of organic compounds [3]. In addition (excluding activated carbons), only little research has been done to synthesize and recognize the structure of carbon materials based on natural resources. This is somewhat hard to understand, as carbon structure synthesis has been practiced from the beginning of civilization on the base of biomass, with the petrochemical age only being a late deviation. A refined approach towards advanced carbon synthesis based on renewable resources would be significant, as the final products provide an important perspective for modern material systems and devices. 

Abstract Synthesis of carbon adsorbents with controlled pore size and surface chemistry adapted for application in medicine and health protection was explored. Conjugated polymers were used as carbon precursors. These polymers with conjugated double bonds C = C have high thermal stability. Formation of sp carbon structures occurs via condensation and aromatization of macromolecules. The structure of carbon materials obtained is related to the structure of the original conjugated polymer, thus the porous structure of carbon adsorbents could be controlled by variation of the conjugated polymer precursor. 

High catalytic activity of catalysts in reactions of reception of cyclohehexane and ethylbenzene dehydrogenation simultaneously with expensive active metal economy, high mechanical durability, and an opportunity of regeneration of the catalyst are achieved due to creation of optimum structure of carbonized material already on the synthesis stage. 

Abstract The discrete variational (DV)-Xa method was used to analyze the high-resolution soft X-ray absorption spectra (XAS) in the C /Cregion of sputtered amorphous carbon films and carbon black to elucidate their local structures. The measured XAS of amorphous carbon and carbon black were compared with those of reference compounds, and the fine structure in the XAS can be assigned by the calculated density of states of the reference compounds. Such a comparative analysis in the measured XAS and the calculated density of states of these carbon materials with reference compounds, which have been known their local or molecular structures, is a valid approach for elucidating the complex local structures of carbon materials. 

We have recently found that some fine structures can be commonly observed in the C K edge X-ray absorption spectra (XAS) of various sputtered amorphous carbon (a-C) films [5,6] and carbon black (CB) [7], To clarify the spectroscopic fine structures from the local-structure and chemical-state point of view, we have compared the XAS of a-C and CB with those of reference compounds, and estimated the local structures of a-C and CB from the spectroscopic analysis using the DV-Xa method. The present paper describes one of the approaches in determining the local structure of carbon materials using the soft X-ray spectroscopy as well as the DV-Xa method. 

Although the complex local structure of carbon materials cannot be easily or completely elucidated by conventional analysis methods, the high-resolution soft X-ray absorption spectroscopy and spectral analysis using the DV-Xa method are promising tools to analyze the local structure. In addition, comparative analysis of carbon materials with reference compounds that have been known their local and molecular structures is a valid approach for elucidating the local structure. 

Raman scattering is a sensitive probe for the structure of carbon materials.Raman spectra of pyrolyzed PAN-MCM show two distinct peaks, the Raman-allowed E2g graphitic peak at 1580 cm l (G), and the D band at - 1360 cm (associated with small domain sizes). Empirical correlations between peak intensity ratios (and band widths) and graphitic domain sizes were used to estimate the average domain size in the PAN-MCM samples, and it was foxmd... 

Carbon atoms crystallize in several forms. Graphite and diamond are well known carbon polymorphs. Fullerenes, which were discovered in the 1980 s, have also been well characterized. Carbon materials show a variety of different physical and chemical properties. Because of this the electronic structure of carbon materials has been investigated using a number of different experimental techniques, for example, XPS, UPS and XANES. Theoretical studies of carbon materials have been also performed. However, experimentally observed spectra are not always consistent with theoretical predictions. Recently, in order to understand the various kinds of observed electronic spectra, DV-Xa calculations have been performed on a small cluster model. [1] In the present paper, we report results of DV-Xa calculations performed on the carbon materials graphite, alkali graphite intercalation compounds (GIC), fullerene, and fluorinated fullerenes. 

The pore structure of carbon materials, particularly of activated carbons, is usually characterized by using physical adsorption of various gases. Nitrogen adsorption at the liquid nitrogen temperature, 77 K, has been used most often. There have been published many reviews and books on pore structure determination by nitrogen gas adsorption [3,4,20,21], and a special issue of the journal Carbon was devoted to this topic focused on carbon materials [22],... 

Recently, various novel techniques have been developed to control the pore structure of carbon materials. Since the pore structure is governed by nanotexture of carbon materials, its control has to be done during carbonization. In the following novel techniques, pore structure was established through the control of the carbonization process without any activation process. 

We carried out comparative studies of the effect of the porous structure of carbon materials on electrochemical electrode characteristics using various carbide carbons (CCs). Main structural characteristics for CCs based on silicon carbide are presented in Table 27.3 and those for titanium carbide are in Table 27.4. Specific surface areas were calculated on the basis of the nitrogen adsorption data with calculation using the DFT technique. This method is used to measure micropores and mesopores, but not macropores. 

R624 K. Gotoh, Analysis of Inner-Pore Structure of Carbon Materials Using Li and Xe NMR , Tamo, 2011, 246, 11. 

The effect of crystal structure of activated carbon on methanation. As mentioned above, the initial methanation temperature of activated carbon derived from coal is more than 500°C and above 600°C for graphite. Although low purity of activated carbon derived from coal, they have strong resist-methanation ability, which indicates the effect of micro-crystal structure on methanation is very significant. The main reason of methanation of activated carbon is the unsaturated dangling bonds of edge carbon atoms, which is confirmed from the crystal structure of carbon materials (Fig. 6.70). ... 

The essence of the method [6] consists in coordination interaction of functional groups of polymer and compounds of 3d-metals as a result of grinding of metal-containing and polymer phases. Further, the composition obtained undergoes thermolysis following the temperature mode set with the help of thermo gravimetric and differential thermal analyzes. At the same time, we observe the polymer carbonization, partial or complete reduction of metal compounds and structuring of carbon material in the form of nanostmctures with different shapes and sizes. 

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