Solutal Bénard-Marangoni instability as a growth mechanism for single-walled carbon nanotubes

In the past few years, considerable progress has been achieved in understanding the growth mechanism of single-walled carbon nanotubes (C-SWNTs). Nevertheless, the nucleation of C-SWNTs still remains partially unexplained by these models. A study of the critical synthesis parameters in the plasma torch process and a review of existing growth mechanisms lead us to propose a new growth mechanism for bundles of C-SWNTs, based on the Bénard-Marangoni instability. It is shown that the conditions occurring at the surface of the catalyst nanoparticle (NP) during the growth of the C-SWNTs give rise to the solutal BMI, which in turn results in a pattern of hexagonal convection cells in the liquid layer on the surface of the NP. The vortex ring flow pattern within these cells is then responsible for the structured growth of the C-SWNT bundles. This model highlights the important parameters required to optimize the synthesis of C-SWNTs.