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A Phenomenological Kinetic Model has been developed that includes all the relevant steps involved in CNT growth by CCVD,that is, carbon source decomposition, nanoparticle surface carburization, carbon diffusion, nucleation, CNT growth, and growth termination by catalyst deactivation or by the effect of steric hindrance.Here we emphasize the importance of using a proper kinetic description of all the stages, in particular the initial carburization-nucleation and the growth cessation. We have discussed the different mechanisms proposed to explain the critical step of carburization-nucleation and have used an autocatalytic kinetic model to describe it. The two parameters involved in this autocatalytic equation allow a very good fit of the initial induction period usually observed during the growth of CNTs. In addition, rigorous formulations of the main causes of CNT growth cessation (catalyst deactivation by several causes and steric hindrance) have been proposed. The developed model is a versatile tool of potentially general application. In this paper, we have applied it to fit data obtained in our lab, and also to super growth of VA-SWNT experimental data published in the literature. In all cases the values obtained for the kinetic parameters have realistic physical meaning in good agreement with the mechanism of CNT formation.

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The question of how the texture and structure of carbon nanofilaments (CNTs) are determined during growth is addressed via their preparation using the vapour phase method over Ni-Cu-Mg-Al catalysts. The CNTs formed and the related catalyst particles were investigated by high resolution transmission electron microscopy, electron diffraction, and X-ray energy dispersive spectroscopy. The nanofilament features were found to directly relate to the catalyst particle size and morphologies, which in turn depend on both the Ni/Cu ratio in the Ni-Cu alloy that forms the catalyst particles and the route by which they were prepared. The extent and orientation of graphenes within the carbon nanofilaments were found to be controlled by the extent of the related catalyst crystal faces and the angle value between the latter. It is proposed that energetics of graphenes, basically involving the ratio of the edge over the core carbon atoms, the energetic cost of heterocycles (pentagon), and that of the stress induced by the strain at graphene bending sites, determine whether the carbon nanofilaments would actually grow as nanotubes (i.e., hollow) with the dual ''herringbone-bamboo'' texture, or as nanofibres (i.e., not hollow) with either the ''herringbone'' texture or the platelet texture. Only the latter allowed the genuine graphite (3D periodicity) structure to develop, while the other nanofilament types could merely adopt the turbostratic structure. Meanwhile, it was demonstrated that the herringbone nanotubes and nanofibres here prepared are of ''cup-stack'' rather than ''single helix'' type.

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