Nanotube bundles

Early transport measurements on individual multi-wall nanotubes [187] were carried out on nanotubes with too large an outer diameter to be sensitive to ID quantum effects. Furthermore, contributions from the inner constituent shells which may not make electrical contact with the current source complicate the interpretation of the transport results, and in some cases the measurements were not made at low enough temperatures to be sensitive to 1D effects. Early transport measurements on multiple ropes (arrays) of single-wall armchair carbon nanotubes [188], addressed general issues such as the temperature dependence of the resistivity of nanotube bundles, each containing many single-wall nanotubes with a distribution of diameters d/ and chiral angles 6. Their results confirmed the theoretical prediction that many of the individual nanotubes are metallic. 

No superconductivity has yet been found in carbon nanotubes or nanotube arrays. Despite the prediction that ID electronic systems cannot support supercon-ductivity[33,34], it is not clear that such theories are applicable to carbon nanotubes, which are tubular with a hollow core and have several unit cells around the circumference. Doping of nanotube bundles by the insertion of alkali metal dopants between the tubules could lead to superconductivity. The doping of individual tubules may provide another possible approach to superconductivity for carbon nanotube systems. 

Fig. 1. Scanning electron micrograph of the soot taken from the chamber wall the threads are nanotube bundles.

Yano, T, Inouye, Y. and Kawata, S. (2006) Nanoscale uniaxial pressure effect of a carbon nanotube bundle on tip-enhanced near-field Raman spectra. Nano Lett., 6, 1269-1273. 

An important route to solubilization of carbon nanotubes is to functionalize their surface to form groups that are more soluble in the desired solvent environment. It has been shown that acid treatment of nanotube bundles, particularly with HC1 or HNO3 at elevated temperatures, opens up the aggregate structure, reduces nanotube length, and facilitates dispersion (An et al., 2004 Kordas et al., 2006). Nitric acid treatment oxidizes the nanotubes at the defect sites of the outer graphene sheet, especially at the open ends (Hirsch, 2002 Alvaro et al., 2004), and creates carbonyl, carboxyl, and hydroxyl groups, which aid in their solubility in polar solvents. 

U.D. Venkateswaran, A.M. Rao, E. Richter, M. Menon, A. Rinzler, R.E. Smalley, P.C. Eklund, Probing the single-wall carbon nanotube bundle Raman scattering under high pressure. Phys. Rev. B 59, 10928-10934 (1999). 

Weber SE, Talapatra S, Joumet C, Zambano A, and Migone AD (2000) Determination of the binding energy of methane on single-walled carbon nanotube bundles. Phys. Rev. B. 61 19. 

Fig. 3.2 Electron microscopy image of a carbon nanotubes bundle [8], Adapted with permission from [8], 2005, American Chemical Society.

J. S. Kim, S. J. Cho, K. S. Jeong, Y. C. Choi, M. S. Jeong, Improved electrical conductivity of very long multi-walled carbon nanotube bundle/poly (methyl methacrylate) composites, Carbon, vol. 49, pp. 2127-2133, 2011. 

Henrard, L., Hernandez, E., Bernier, R, and Rubio, A. 1999. van der Waals interaction in nanotube bundles Consequences on vibrational modes. Phys. Rev. B 60 R8521-24. 

Govindaraj A, Satishkumar BC, Nath M, Rao CNR (2000) Metal Nanowires and Intercalated Metal Layers in Single-Walled Carbon Nanotube Bundles. Chem Mater 12 202-205... 

M. W. Cole, V. H. Crespi, G. Stan, J. M. Hartman, S. Moroni and M. Boninsegni, Anisotropic Condensation of Helium in Nanotubes Bundles, Priv. Communication, 1999. 

The distribution of molecular hydrogen throughout a SWNT lattice as a funtion of the nanotube diameter/chirality. The ratio of endohedral (within the nanotube)/exohedral H2 population in the lattice is largely determined by the energetics associated with adsorption in these sites. To answer this question, careful examination of various H2 population distributions in the nanotube bundle is required. 

Figure 12-4 displays the H2 density distribution obtained over the course of a simulation for the 1.51 wt. % and 6.5 wt. % H2 loadings. These distributions were obtained by determining the locations of the centers of mass of each H2 molecule at every MD step. In both cases, the calculated MD trajectories show that H2 molecules quickly diffuse around the exterior of the nanotube bundle. The adsorption process is highly dynamic on the exterior walls of the bundle. While molecules at the... 

Fig. 18 SEM images of aligned-nanotube bundles obtained by the pyrolysis of ferrocene (from Rao et al. " ).

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