Phone: þ7 383 326 9510, Fax: þ7 383 330 8056Curved graphene fragments can be considered as building blocks of carbon nanotubes. Thus, the size of graphene fragments may be considered as one of the most important characteristics of their structural disorder. In this paper, we have performed a comparative Raman study of CVD multi-walled carbon nanotubes (MWCNTs) and graphene flakes deposited on MWCNTs. Raman data have been considered in combination with HRTEM characterization of nanotubes. The basic attention has been paid to the behavior of D (disorder-induced), G (tangential mode), and 2D (two-phonon scattering) bands in Raman spectra in order to use them for MWCNT characterization. A ratio of intensities of 2D and D bands (I 2D /I D ) demonstrates almost a linear dependence on the mean diameter of MWCNTs produced with two different types of catalysts (see abstract figure). It should be mentioned that each type of catalyst provides the linear dependence with its own specific slope. The graphene fragments have been proposed to form a mosaic structure of nanotube walls. I 2D /I D ratio depends on the amount of graphene flakes deposited on nanotube surface via ethylene decomposition.A dependence of intensity ratio I 2D /I D on the diameter of nanotubes produced with different types of catalysts.A Raman spectroscopy has obvious advantages because it provides an express and nondestructive control of structural and electronic characteristics of carbon materials. Graphite, diamond, graphene, nanotubes, fullerenes in form of monocrystals, polycrystalline films, and powders show their own features in Raman spectra and, thus, can be identified with this technique [4][5][6][7][8][9][10][11][12]. The graphene fragments can be considered as building blocks of sp 2 -carbon materials. The size of graphene fragments may be considered

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The formation of active component of Fe-Mo and Co-Mo catalysts for carbon nanotube growth with variable Mo content is studied with in situ XRD, XPS, and STEM&EDX. The activation of bimetallic Fe-Mo catalysts under the growth conditions leads to the formation of Fe-Mo alloy particles in contrast to Co-containing catalysts in which active alloy incorporates only a small portion of Mo (<2-3 at.%). The stable carbide formation for these systems is not detected. The effect of Mo content in Fe-Mo and Co-Mo catalysts on the properties of MWCNTs is additionally investigated using the Raman spectroscopy in combination with measurements of the temperature dependence of conductivity. It is shown that MWCNT defectiveness depends on the active component composition for both Fe-Mo and Co-Mo catalysts. The current carrier concentration for the MWCNTs grown on Fe-Mo catalysts slightly increases with the Mo content. The opposite effect is observed for the tubes grown on Co-Mo catalysts, showing a decrease in the current carrier concentration with the increase of Mo concentration.

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