Aerosol-assisted chemical vapour deposition synthesis of multi-wall carbon nanotubes: II. An analytical study

We report the study of different aspects of the aerosol-assisted chemical vapour deposition (ACVD) method for the optimised synthesis of multi-wall carbon nanotubes (MWCNTs). Fifteen hydrocarbons (alkanes, benzene derivatives, and cyclohexane derivatives) were used in conjunction with catalyst concentrations of 1–15 wt.% in order to investigate their effect on morphology, residual catalyst content, diameter distribution, defect density and oxidation resistance of MWCNTs. The conversion yield of the precursors was measured and their thermocatalytic cracking behaviour was studied in situ using an integrated mass spectrometer. We believe that each hydrocarbon interacts differently with the catalyst and follows a characteristic cracking route involving the creation of certain intermediate hydrocarbon fragments which are responsible for the formation of MWCNTs with different properties. We show that the properties of MWCNTs can be tuned by altering the composition of the precursor and that the synthesis rate and the precursor conversion yield can be improved by 60% and 80%, respectively, compared to the commonly used carbon sources such as toluene or xylene. Moreover, while maintaining MWCNT sample quality, i.e. MWCNTs have similar or fewer defects densities and higher oxidation resistance, the amount of residual catalyst particles in the MWCNT samples could also be reduced by ca. 50%.