Other Carbon Materials

Apart from being a popular filler for elastomeric materials, soot is an excellent black pigment. Several properties make it downright ideal for printing purposes it is light-fast and insoluble in almost any common solvent as well as it exhibits low particle size and great color depth and strength. Yet more than 90% of the 

Owing to their chemical, thermal, and mechanical resistance, carbon fibers are an ideal material for highly durable composites. Compared to steel, they are four times Ughter at similar strength, which in addition is preserved up to temperatures of more than 2000 °C. Certain threads, ribbons, and fabrics are made from pure carbon fibers, as well as there are carbon-reinforced plastics which are employed to manufacture, for example, components of aircrafts or cars, sporting devices, implants, or filters for dusts and aerosols. 

Activated carbon is a versatile adsorbent, for example, to decolorize sugar or to free spirit from fusel oil. Gases may be purified and toxic substances may be removed from breathing air (apphcation in gas masks) same as flue gases are desulfurized using activated carbon. 

Glassy carbon is chemically very inert even at elevated temperatures because there is virtually no porosity at aU and its structure does not allow for intercalation. 

It is only attacked by oxygen and oxidizing melts at more than 600 °C. Accordingly, it is employed in ultratrace analysis (no memory effects in crucibles of glassy carbon) and in the semiconductor industry. 

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Carbon nanotubes are unique materials with specific properties [42]. There is a considerable application potential for using nanotubes in the biomedical field. However, when such materials are considered for application in biomedical implants, transport of medicines and vaccines or as biosensors, their biocompatibility needs to be established. Other carbon materials show remarkable long-term biocompatibility and biological action for use as medical devices. Preliminary data on biocompatibility of nanotubes and other novel nanostructured materials demonstrate that we have to pay attention to their possible adverse effects when then-biomedical applications are considered. 

A number of other carbon materials have been used for electrochemical detection [6] however, at this point none of these appear to have a clear advantage over the electrodes described earlier. Nevertheless, these alternative materials certainly do work and there is little doubt that we will continue to see additional entries as the search for the ideal electrode continues. The chapter on carbon electrodes by McCreery and Kneten (Chap. 10) is a good place to review the fundamental issues. 

Moreover, it has been remarked that it is necessary to use more than one adsorbate for a correct characterization of the narrow porosity. Thus, in the case of CMSs and other carbon materials (i.e., highly activated carbons) with narrow micropores, N2 at 77 K is not a suitable adsorbate due to diffusion problems. Other adsorptives and conditions, like C02 at 273 or 298 K, avoid such problems. From all of these, it can be concluded that for a suitable characterization of the porosity of carbon materials by physical adsorption, the use of more than one adsorbate and the application of several theories and methods to the adsorption-desorption isotherms are recommended. 

Our preliminary tests show that the proposed model, probably, are applicable to field emission cathodes based on different carbon materials not only carbon nanotubes. However in order to define the applicability area of the proposed model it is necessary to carry out auxiliary investigations with other carbon materials. 

Pyrolysis can be performed for many different reactors. The prodnct distribntion varies markedly between the different reactor types and the reaction conditions, snch as temper-atnre, bed materials or catalyst. The aim of the pyrolysis is the redaction of wastes for landfilling and the prodnction of fnels. Especially fuel oil with a high calorific value is an interesting product. Char can be used as a fuel, but is also seen as a precursor for other carboneous materials such as activated carbon. The best way to obtain these products is decarboxylation of the polymer. In this way carbon oxide-rich gas is produced. 

SWCNTs, DWCNTs, or MWCNTs with very small inner-tube diameters show another size-dependent Raman feature in the low-frequency range referred to as radial breathing modes (RBMs) [35, 39, 40]. The RBMs are considered as a clear indicator for the presence of CNTs, since this Raman feature is unique to CNTs and is not observed for other carbon materials. As suggested by the name, the RBM is a bond-stretching, out-of-plane mode, where all carbon atoms vibrate simultaneously in the radial direction. The RBM frequencies are between 100 and 400 cm and were found to be inversely proportional to the tube diameter [41 3]. In case of DWCNTs and small-diameter MWCNTs, RBM frequencies higher than 200 cm are ascribed to inner tubes while lower frequencies can be associated with both, inner and outer tubes [44, 45]. SWCNTs typically exhibit... 

The Raman characterization of different carbon nanomaterials in inert (Ar) atmosphere reveals a strong influence of the laser power (energy density) on the Raman spectra [59]. In general, an increase in the laser power leads to a decrease in the Raman frequency. For example, when using the most common excitation source in Raman spectroscopy - the 514-nm line of an Ar-ion laser - the G Band in the Raman spectrum of carbon onions (Fig. 12.22a) shifts from 1,594 cm (0.1 mW) down to 1,565 cm (0.7 mW). The downshift is related to an increase in the sample temperature and has been measured for other carbon materials including graphite and CNTs. 

One of the most important applications of uranium-series methods of age determination has been the dating of fossil corals and other carbonate materials. In contrast to deep-sea sediments, which accumulate excess h and Pa that decay over time, carbonates accumulate uranium by co-precipitation from seawater that is essentially free of °Th and Pa. The radioactive ingrowth of °Th and Pa over time toward secular equilibrium with and is the basis of the two methods. 

B. Specific Properties of Active Carbon in Relation to Other Carbon Materials... 

Figure 14.6 Comparison of -heptane adsorption energy distribution ciu-ves determined on C o and other carbon materials. (Reprinted from Ref. [47] with permission from Elsevier.)...

For a qualitative determination of the mesopore size distribution, mathematical models have to be used. Of these, the Barrett, Joyner, Halenda (BJH) method [30] is widely used for OMCs [14, 31, 32] and other carbon materials. However, for OMCs this model has some important shortcomings. As already mentioned above, the OMC mesopores might be as narrow as 2 nm. For such mesopores, the BJH method seriously underestimates the pore width [33]. Thus, improved data treatment methods have been proposed [33, 34]. As an example, the mesopore size distributions for an OMC of the CMK-1 type calculated with... 

The situation is different for other carbon materials such as activated carbons. During activation of the precursor, partial oxidation of the carbon proceeds from the external surface of the carbon particle to the interior. Thus, the portion of the activated carbon particle close to the external surface is more severely activated than the interior and chemistry of the external and internal surface is most likely to be different. Before surface spectroscopy and gas adsorption data of OMCs are compared, the surface spectroscopic analysis of the carbon materials is reviewed very briefly. 

From their first measurement and theoretical discussion on, the Raman spectra of carbon nanotubes provided valuable information on the shape and composition of the structure. They can also serve to prove the existence or nonexistence of nanotubes in a sample, which is assessed, among others, by considering a distinct Raman band. It is called radial breathing mode (RBM) band and corresponds to a synchronous radial vibration of all carbon atoms in perpendicular to the tube s axis. This band is the characteristic of the nanotube stracture, and for the time being, nothing Hke this has ever been observed for any other carbon material studied. 

For other carbon materials, and especially for the activated carbons, it has been known for long that they are serviceable supports for heterogeneous catalysts. Counting among the reasons for this is their large specific surface. Carbon nanotubes are suitable catalyst supports as well. Apart from a better control over... 

Besides the direct generation of nanodiamond in a detonation, the required pressure can also be achieved by the achon of an external shock wave. Usually, the latter is induced by an explosion too and compresses the carbon material that is enclosed in a kind of capsule. A catalyst Hke, for example, copper, iron, aluminum, nickel, or cobalt is frequently employed in this process. It has already been mentioned in the introduction that nanoscale diamond particles had been prepared quite early by the conversion of other carbon materials in a shock wave. Soon after this discovery, researchers of the DuPont Corp. developed a method also based on shock action that yields very small diamond particles. These are processed by subsequent sintering to give utterly durable cutting and poHshing tools. 

Carbon-supported catalysts have been studied extensively in the hydrogenation of carbon oxides (CO and CO2) to yield methane and hydrocarbons. Different phases (e.g., metals, metal alloys, carbides) have been prepared by a variety of techniques and precursors. Also, although the early studies used activated carbons as support, more recent studies analyze the possibilities of other carbon materials, such as nanofibers and nanotubes. 

The carbonization of pure organic compounds such as carbazole, phenazine, acridine (for formulas, see Figure 7.2) has also been studied under 7.5 Mbar argon pressure [23], Volatile compounds such as benzene, pyridine, pyrazine, quinoline, and phenazine have been calcined at 1073 K in sealed quartz glass tubes [24], Bent carbon nanotubes and coils with a nitrogen content of about 1% were formed when pyridine, 5-methylpyrimidine, or i-triazine (see Figure 7.2) were decomposed on small catalytic cobalt particles at 1123 or 1373 K [25], Carbon nanotubes with about 2% N were produced in excellent yield and free of other carbon materials by pyrolysis of pyridine vapor at 1373 K in an argon stream with admixed iron pentacarbonyl, [Fe(CO)s] [26], In another study, pyrrole vapor has been catalytically decomposed on nickel sheets at 1073 K [27],... 

Chemical vapor deposition (CVD) has been used to obtain deposits of nitrogen-containing carbon on the surface of other carbon materials. A helium stream with an added aromatic compound such as benzene [28] or pyridine... 

The composition of a typical cathode of alkaline Mn02-Zn cells falls in the following range 80-85 % Mn02 (EMD), 8-15 % graphite flake and other carbon material, 10-15 % KOH solution (7-9 M), 0.3-4 % binder and/or other additives. The blended mix is molded into a steel can under high pressure to form a sleeve. The increase of capacity of alkaline Mn02-Zn cells... 

The ROP technique has also been extended to functionalize other carbon materials such as C60, carbon black and carbon fibers. ... 

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