Study of the growth parameters of multiwalled carbon nanotubes

In this work, the effects of various parameters on the growth of multiwalled carbon nanotubes (MWCNTs) with Fe, Ni, and vermiculite catalysts were investigated in detail and a comparative analysis was carried out in terms of the quality and yield at different growth temperatures. Interestingly, the morphology of MWCNT arrays and their lengths prepared by vermiculite catalysts with the increase in temperature is reported. Moreover, the results indicated that MWCNTs had a narrow diameter distribution, few defects, and high graphitization degree at the optimal growth temperature, and most MWCNTs were defective below the optimum temperature. However, the high growth temperature promoted the agglomeration of catalyst particles, which in return increased the tube diameters of MWCNTs. The higher degree of graphitization in this work may have been caused by the thick diameters of MWCNTs. In addition, the apparent activation energies required for the preparation of MWCNTs using Fe, Ni, and vermiculite catalysts were calculated and that of the Ni catalyst was the lowest. Based on hydrodynamics and heat transfer, it is reported for the first time that the quality and yield of MWCNTs varied significantly with different placement locations. The carbon production was also predicted for different positions, and the optimal growth location was confirmed.