Thickness graphite flakes

Figure 10. Schematic model showing the influence of the thickness of a graphite flake on the extent of co-intercalation of solvent molecules in the internal van der Waals gaps of graphite, (a) Thick graphite flakes (b) thin graphite flakes. Prepared with data from Ref. [169].

As an alternative to the use of acids, sequestering agents have been employed to dissolve the corrosion products without attacking the parent metal. The most effective formulations are based on the derivative of ethylene diamine-tetra acetic acid (EDTA). Lead artefacts from the Mary Rose were cleaned in a 10% solution of this compound. The use of EDTA is not recommended for cast iron as the graphite flakes embedded within the corrosion products are also dissolved. As with the use of acids, the shape of the artefact is altered if the corrosion layers are very thick and it is also difficult to wash out all the solutions from cracks, crevices and pores in the artefact after cleaning. 

In residue compounds prepared from lamellar compounds based on artificial polycrystalline graphite, 1/3 of the original intercalant may be retained depending on particle size and crystallinity of the material. Lamellar compounds prepared from large crystals decompose only slowly, not just because of longer diffusion pathways in the interlayer gap but because the amount of retained intercalant also increases with the thickness of the graphite flakes °. 

As mentioned above, employment of MWCNT for field emitter will be one of the most important applications of MWCNT. For this purpose, MWCNT is prepared by the chemical purification process [30,38], in which graphite debris and nanoparticles are removed by oxidation with the aid of CuCl2 intercalation [38]. Purified MWCNT is obtained in the form of black and thin "mat" (a flake with thickness of ca. a few hundreds of [im). Figure 7 shows a typical transmission electron microscope (TEM) picture of MWCNT with an open end, which reveals that a cap is etched off and the central cavity is exposed. 

Graphite is widely distributed throughout the world though much of it is of little economic importance. Large crystals or flake occur in metamorphosed sedimentary silicate rocks such as quartz, mica schists and gneisses crystal size varies from <1 mm up to about 6 mm (average 4mm) and the deposits form lenses up to 30 m thick stretching several... 

Quantitative predictions of the effects of fillers on the properties of the final product are difficult to make, considering that they also depend on the method of manufacture, which controls the dispersion and orientation of the filler and its distribution in the final part. Short-fiber- and flake-filled thermoplastics are usually anisotropic products with variable aspect ratio distribution and orientation varying across the thickness of a molded part. The situation becomes more complex if one considers anisotropy, not only in the macroscopic composite but also in the matrix (as a result of molecular orientation) and in the filler itself (e.g., graphite and aramid fibers and mica fiakes have directional properties). Thus, thermoplastic composites are not always amenable to rigorous analytical treatments, in contrast to continuous thermoset composites, which usually have controlled macrostructures and reinforcement orientation [8, 17]. 

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