Graphitic carbon fibers structure

Affected by multiple scattering are, in particular, porous materials with high electron density (e.g., graphite, carbon fibers). The multiple scattering of isotropic two-phase materials is treated by Luzatti [81] based on the Fourier transform theory. Perret and Ruland [31,82] generalize his theory and describe how to quantify the effect. For the simple structural model of Debye and Bueche [17], Ruland and Tompa [83] compute the effect of the inevitable multiple scattering on determined structural parameters of the studied material. 

Koyama T, Endo M. Structure and properties of graphitized carbon fiber. Jpn J Appl Phys 1974 13 1933-1939. 

Table 4 compares the mechanical properties of various organic fibers, graphite/carbon fibers, ceramic fibers, and glass fibers, and lists commercially important applications. One major application of organic fibers, such as Spectra and aramid fibers, is in ballistic In contrast, graphite, ceramic fibers, and glass fibers are primarily used in structural applications. One of the reasons that organic fibers find little... 

Pyrolytic graphite is different from another standpoint although produced in bulk form, its main use is in the form of coatings, deposited on substrates such as molded graphite, carbon fibers, or porous carbon-carbon structures. As such, it is part of a composite structure and is not as readily identifiable as other forms of carbon. It is similar in this respect to CVD diamond and diamond-like carbon (DLC) described in Chs. 13 and 14. 

Several varieties of fuel cells use an electron-conducting porous DM as an interface between the catalyst layer and the current collectors. This DM is not shown in Figure 2.9, since it is not a universal feature of all fuel cells. For example, PEFCs use a carbon-based porous media for this purpose, as shown in Figure 2.14. Either a woven carbon cloth or a carbon fiber structure bonded with a graphitized thermoset resin is typically used for this purpose. Alkaline fuel cells also use a similar porous media to aid electron conduction between the porous electrodes and current collectors. 

The properties of mesophase pitch-based carbon fibers can vary significantly with fiber texture. Inspection of the cross-section of a circular mesophase fiber usually shows that the graphitic structure converges toward the center of the fiber. This radial texture develops when flow is fully developed during extrusion through the spinnerette. Endo [48] has shown that this texture of mesophase pitch-based carbon fibers is a direct reflection of their underlying molecular structure. 

Since PAN-based carbon fibers tend to be fibrillar in texture, they are unable to develop any extended graphitic structure. Hence, the modulus of a PAN-based fiber is considerably less than the theoretical value (a limit which is nearly achieved by mesophase fibers), as shown in Fig. 9. On the other hand, most commercial PAN-based fibers exhibit higher tensile strengths than mesophase-based fibers. This can be attributed to the fact that the tensile strength of a brittle material is eontrolled by struetural flaws [58]. Their extended graphitic structure makes mesophase fibers more prone to this type of flaw. The impure nature of the pitch preciusor also contributes to their lower strengths. 

Key Words—Carbon nanotubes, vapor-grown carbon fibers, high-resolution transmission electron microscope, graphite structure, nanotube growth mechanism, toroidal network. 

The direct linking of carbon nanotubes to graphite and the continuity in synthesis, structure and properties between carbon nanotubes and vapor grown carbon fibers is reviewed by the present leaders of this area, Professor M. Endo, H. Kroto, and co-workers. Further insight into the growth mechanism is presented in the article by Colbert and Smalley. New synthesis methods leading to enhanced production... 

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