Carbon Nanotube Growth by Catalytic Chemical Vapor Deposition: A Phenomenological Kinetic Model

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.