Abstract. The synthesis, sorting and organization of carbon nanotubes are major challenges toward future applications. This chapter reviews recent advances in these topics, addressing both the bulk production and processing of carbon nanotubes, and their organization into ordered structures, such as fibers, and aligned arrays on surfaces. The bulk synthetic methods are reviewed with emphasis on the current advances toward mass production and selective synthesis. New approaches for the sorting of carbon nanotubes by structure and properties are described in the context of the specific physical or chemical interactions at play, and referring to the characterization methods described in the contribution by Jorio et al. Recent advances in the organization of carbon nanotubes into fibers are reviewed, including methods based on spinning from solution, from dry forests, and directly from the gas phase during growth. The organization of carbon nanotubes on surfaces, as a critical prerequisite toward future applications in nanoelectronics, is reviewed with particular emphasis given to the synthesis of both vertically and horizontally aligned arrays. Vertically aligned growth has been recently boosted by the development of highly efficient catalytic processes. Horizontally aligned growth on surfaces can yield a whole new array of carbon-nanotube patterns, with interesting physical properties and potential applications. Different mechanisms of horizontally aligned growth include field-and flow-directed growth, as well as recently developed methods of surface-directed growth on single-crystal substrates by epitaxial approaches. The proposed mechanisms pertinent to each technique are discussed throughout this review, as well as their potential applications and critical aspects toward future progress.

Vorsicht Stufe! Einwandige Kohlenstoff‐Nanoröhren wachsen entlang den Stufen benachbarter α‐Al2O3‐Oberflächen und ergeben ausgerichtete Anordnungen von nanometerbreiten Drähten auf einem dielektrischen Material. Die Nanoröhren (siehe Bild im Hintergrund) geben die Eigenschaften der Oberfläche wieder, z. B. Stufen, Facetten und Knicke (siehe Modell). Richtung und Morphologie der Stufen können durch den Fehlschnitt des Kristalls gesteuert werden.

Owing to their mechanically tunable electronic properties, carbon nanotubes (CNTs) have been widely studied as potential components for nanoelectromechanical systems (NEMS); however, the mechanical properties of multiwall CNTs are often limited by the weak shear interactions between the graphitic layers. Boron nitride nanotubes (BNNTs) exhibit a strong interlayer mechanical coupling, but their high electrical resistance limits their use as electromechanical transducers. Can the outstanding mechanical properties of BNNTs be combined with the electromechanical properties of CNTs in one hybrid structure? Here, we report the first experimental study of boron carbonitride nanotube (BCNNT) mechanics and electromechanics. We found that the hybrid BCNNTs are up to five times torsionally stiffer and stronger than CNTs, thereby retaining to a large extent the ultrahigh torsional stiffness of BNNTs. At the same time, we show that the electrical response of BCNNTs to torsion is 1 to 2 orders of magnitude higher than that of CNTs. These results demonstrate that BCNNTs could be especially attractive building blocks for NEMS.

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In this work we present preliminary results from molecular dynamics simulations for carbon nanotubes serpentine dynamics formation. These S-like nanostructures consist of a series of parallel and straight nanotube segments connected by alternating U-turn shaped curves. Nanotube serpentines were experimentally synthesized and reported in recent years, but up to now no atomistic simulations have been carried out to address the dynamics of formation of these structures. We have carried out fully atomistic molecular dynamics simulations in the framework of classical mechanics with a standard molecular force field. Multi-million atoms structures formed by stepped substrates with a carbon nanotube (about 1 micron in length) placed on top of them have been considered in our simulations. A force is applied to the upper part of the tube during a short period of time and then turned off and the system set free to evolve in time. Our results showed that these conditions are sufficient to form robust serpentines and validate the general features of the ‘falling spaghetti mechanism’ previously proposed to explain their formation.