Abstract
Commercially grown, multi-walled carbon nanotubes (MWNTs), available in kilogramme quantities from three commercial suppliers have been characterised using a number of analytical techniques. The catalysts used in the growth of the MWNTs are identified by energy dispersive X-ray spectroscopy (EDX) and different growth mechanisms are postulated to explain the various structures present in the MWNT stock in its as-supplied form. A tightening of the agglomerate structures during purification and functionalisation is shown using scanning electron microscopy (SEM) and confirmed more qualitatively using pore-size distributions obtained using the Brunauer–Emmett–Teller (BET) method and non-local density functional theory (NLDFT) calculations. Differences in thermal stability are shown using thermogravimetric analysis (TGA) and are related back to the residual catalysts present. X-ray photoelectron spectroscopy (XPS) is used to confirm functionalisation of certain grades and Raman spectroscopy is used to investigate the level of defects present.