Influence of dispersion technique/time on dispersion stability, aspect ratio and morphology of multi-walled carbon nanotubes

Current interest in nanoscience and nanotechnology has motivated a remarkable research effort in carbon nanotubes (CNTs), which has addressed a variety of issues and produced several new findings. The uniform and stable dispersion of CNTs in solvents/nanocomposites is often a necessity for their effective use in advanced materials. In this study, the dispersion states of multiwalled carbon nanotubes (MWCNTs) in numerous solvents were analysed by UV-vis spectroscopy and visual observations (photographic images). Furthermore, the influence of sonication and ball milling time on the MWCNT morphology and dispersion was analysed through scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that the MWCNT was highly dispersible in DMF, isopropanol, chloroform and acetone, and the dispersion state of MWCNT in these solvents can be classified as dispersed. The obtained results indicate that the oxidation incorporates oxygen-containing groups on the surface of MWCNTs, which establish the electrostatic stability needed for long-period stable dispersion in solvents. Morphological investigation of MWCNTs shows less than 20 min of dispersion is insufficient to achieve untangled CNTs with good dispersion, while 20-60 min of dispersion demonstrates CNTs bonding, intersections, junctions and number of defects on MWCNTs due to high energy involved. Apart from this, significant MWCNT shortening has been observed for the dispersion period of 90 min-6 h. The investigation of the dispersibility of MWCNTs in different solvents and the effect of sonication and ball milling time on the MWCNT morphology and dispersion are important for enhancing the comprehensive understanding of its applications.