Carbon materials characteristics

Carbonization Process Precursors Carbon Materials Characteristics... 

Figure 56. Charge-dicharge characteristics of some carbon material electrodes (1st cycle current density 0.2 mA crrT2...

Table 2. Characteristics of the silica templates and the corresponding carbon materials a unit cell parameter Sbet- specific surface area Vp total pore volume (at P/Po=0.95) Pore size determined according to the BJH method - Maximum value of the BJH pore size distribution peak calculated from the adsorption branch of the N2 isotherm.

At the electrochemical performance level, these novel natural graphite-based materials surpass mesophase carbon s characteristics as related to cell/battery safety performance, low irreversible capacity loss, and good rate capability even at high current densities. 

The characteristics of a carbon material used as active reagent of the negative electrode (anode) of a Lithium-Ion cell considerably influence the power characteristics of the cell as a whole. Thus, the major parameters are the values of specific capacity per unit weight and volume, and also the... 

Carbon-14 labeled materials, basic building blocks of, 21 273 Carbonaceous fiber, 13 383-385 Carbonaceous limestone, 15 27 Carbonaceous materials, characteristics of, 12 762... 

Modifying the surface characteristics to enhance the charge storage. There is a broad protocol to modify the surface characteristics of carbon materials, especially the nanostructured carbon materials, to have excellent adsorption/desorp-tion behavior ... 

With rapid development of zeotypic materials and mesoporous solids and their application in heterogeneous catalysis, HRTEM shows its advantages in distinguishing the ultrastructural features [40, 41], Carbon materials are used as support in catalytic reactions due to some of their specific characteristics and many publications report the TEM investigations on various forms of carbon related materials [42-48],... 

Raman microspectroscopy [3] allows the observation of the transformation of a polyene structure to a carbon one. The formation of conjugate polyene units under the conditions of chemical dehydrochlorination of the polymer was confirmed by the presence of characteristic narrow peaks at 1,107 and 1,490 cm in the Raman spectra. The products obtained by thermal treatment at elevated temperatures are highly disordered sp -carbon materials, in which the porous structure has developed upon subsequent gasification (Fig. 4.3). 

Table 2 shows that SC-155(G40.60) and C-l55(G20.20), which have comparable values of specific surface area, have very different CO conversion values. Both materials were produced under different gelling and drying conditions, and as a consequence the C-155 precursor (SC-I55/G20.20) was different in pore size distribution than the SC-I55(G40.60), but that difference has not sense when silica was eliminated for to produce C-155, having the last one other new characteristics then the observed differences in CO conversion are mainly attributed or to the higher value of specific pore volume of C-155, or because some of the metallic iron were on silica surface of the SC-155 diminishing its catalytic activity, but not attributed to the different gelling and drying conditions. CON material, in spite of its low specific surface area and its low specific pore volume is a fully carbon material like C-155 is, then its lower performance in CO conversion is attributed to the specific surface and pore characteristics. 

In Table 2.1, the carbonization processes are classified on the basis of the intermediate phases of the precursor used [42], and the representative carbon materials formed are listed with their characteristics. 

In this chapter, the structures and textures of carbons at different scales are explained. The carbon materials are classified into four families, diamond, graphite, fullerene, and carbyne on the basis of hybridized sp3, flat sp2, curved sp2, and sp orbitals used, respectively. Each family has its own characteristic diversity in structure and also in the possibility of accepting foreign species. The formation of these carbon materials from organic precursors (carbonization) is shortly described by dividing the process into three phases (gas, solid, and liquid), based on the intermediate phases formed during carbonization. The importance of nanotexture, mainly due to the preferred orientation of the anisotropic BSU in the graphite family, i.e., planar, axial, point, and random orientation schemes, is particularly emphasized. 

Leis, J., Arulepp, M., and Perkson, A. Method to modify the pore characteristics of porous carbon and porous carbon materials produced by this method. European Patent WO/2004/094307, 2004. 

Janes, A., Permann, L., Arulepp, M., and Lust, E. Electrochemical characteristics of nanoporous carbide-derived carbon materials in non-aqueous electrolyte solutions. Electrochem. Commun. 6, 2004 313-318. 

As it can be seen in Figure 4.3, the characteristic curve for N2 superimposes over that for C02 up to a value of (A/p)2 lower than about 400 (kJ/mol)2, confirming what was previously explained. From this value, a large downward deviation is observed in the N2 characteristic curve. This behavior has been observed with other microporous carbon materials and, in fact, it is a common problematic feature of the characteristic curves for N2 adsorption in microporous carbons and hence, a limitation of its use in such low relative pressures (i.e., from 10-3 to 10-7) [10,11,17], This downward deviation... 

The authors have applied this approach to low- and high-pressure C02 adsorption isotherms (using the fugacity instead of pressure) for determining the PSD of several carbon materials, including CMSs [10]. The obtained PSD confirmed the characteristics of these CMSs. Other examples of application of this method are included in Section 4.2.3.5. 

How much Conway appears to be out of touch with carbon (electrochemistry research is confirmed by his discussion of a 1972 paper by Thrower, presumably published in J Electroanal Chem anyone familiar with Peter Thrower s expertise—and that means any serious carbon researcher—knows that such a paper cannot (and does not ) exist. Finally, in the light of recent proposals regarding the edge chemistry of carbon surfaces [6], Conway s conclusion that [m]any porous or powder[ed] carbon materials have dangling surface bonds which are associated with free-radical behavior should also be viewed with caution (see Figure 5.4). Therefore, perhaps the most (and only ) reliable take-home message from this review is that much basic research of a substantive kind is required to relate the electrochemical behavior of various preparations more quantitatively to... (5) the surface chemistry of carbon preparations and their shelf-life stability, cycle life, and self-discharge characteristics. ... 

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