Effect of Multi-Walled Carbon Nanotubes' Aspect Ratio and Purity on the Surface Morphology and Electrical Properties of Composite Nanofibers

Hypothesis: Electrospinning of nanoparticles/polymer solutions offers the potential to achieve novel composite nanofibers in a variety of high performance applications. In this respect, the aspect ratio and purity of multi-walled carbon nanotubes (MWCNTs) were examined to study the morphological and electrical properties of the electrospun composite nanofibers. In the first step, MWCNTs samples were characterized using scanning electron microscopy (SEM) and Raman spectroscopy. Next, nanocomposite solutions containing MWCNTs were prepared by physical dispersion method in presence of a non-ionic surfactant. Finally, the prepared composite solutions were loaded to a glass syringe and connected to a DC power supply device. The electrospinning was performed by applying a high voltage of 15kV between the needle and the rotating collector. Findings: It is generally accepted that a combination of G-band intensity and G/D ratio is useful to evaluate the purity and crystallinity of MWCNTs. The morphological properties of the electrospun composite nanofibers showed their high dependency on carbon nanotubes dimensions, so that at higher aspect ratios the morphological properties generally improved. The morphological analysis of the composite nanofibers revealed that the deformation of the nanofibers increased with increasing MWCNTs diameter. Very smooth surfaces of the composite electrospun nanofibers even with 1 wt% MWCNT concentration were successfully achieved because of the high stability of MWCNT dispersions. The composite nanofibers with higher purity and aspect ratio presented better electrical conductivity. The electrical conductivity of electrospun composite nanofibers could be adjusted from ~10–8 S/cm (insulator) to ~10–3 S/cm (conductor) by different aspect ratios and purities of MWCNTs. MWCNTs with high aspect ratio and high purity offer a promising way to develop electrospun composite nanofibers with improved morphological and electrical properties.