Multi-walled Carbon Nanotubes In Solvents Research Articles

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.

Polyurethane hybrid membranes with confined mass transfer channels: The effect of functionalized multi-walled carbon nanotubes on permeation properties

Aiming to prepare pervaporation membranes with confined mass transfer channels, multi-walled carbon nanotubes (MWCNTs) with and without functionalization were incorporated into polyurethane (PU) polymer matrices. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD), Fourier-transform infrared (FTIR), and Raman spectroscopy were employed to explore the effect of functionalization on the morphologies of MWCNTs. The changes in the morphologies of the resulting PU hybrid membrane were then characterized by SEM, TEM, and XRD. Swelling-sorption and pervaporation experiments of benzene and cyclohexane were employed to evaluate the separation performances of various hybrid membranes. The results showed that the introduction of many oxygenated functional groups onto the MWCNT surfaces through functionalization not only efficiently inhibited the MWCNT aggregation but also improved the distributions of the MWCNTs in solvents and polymer materials. Due to the 1D tube structures of the MWCNTs with conjugated π bonds, the addition of well-distributed MWCNTs into the hybrid membranes not only increased the benzene sorption abilities of the membranes but also enhanced the benzene diffusion selectivities due to the strong driving force for the molecules in the confined mass transfer channels. A higher content of well-distributed MWCNTs in the membrane yielded a higher separation performance for benzene. Additionally, increasing the operating temperature in the pervaporation experiments accelerated the molecular motion and weakened the affinity between the benzene molecules and the walls of the MWCNTs, increasing the permeation fluxes of the membranes while decreasing the benzene separation factors.

Effect of surfactant functionalization of multi-walled carbon nanotubes on mechanical, electrical and thermal properties of epoxy nanocomposites

The present paper compares the mechanical, electrical and thermal properties of epoxy nanocomposites (prepared by solution blending method) by adding four different multi-walled carbon nanotubes (MWCNTs), which are pristine, cationic, anionic and non-ionic surfactant functionalized MWCNTs, respectively. This investigation focused on the effects of dispersion of MWCNTs on the physical properties. Systematical characterization on the dispersion of MWCNTs in different solvents were did via UV-Vis spectrophotometer. The Hansen solubility parameters (HSPs) and dispersion of MWCNTs in solvent and epoxy were both changed after surfactants introduced especially for the non-ionic surfactant. Finally, mechanical, fracture toughness, electrical and thermal properties of epoxy composites were found can be improved because of good dispersion of MWCNTs (especially non-ionic surfactant).

Functionalization of multi-walled carbon nanotubes (MWCNTs) with nitrogen plasma for photovoltaic device application

Abstract Multi-walled carbon nanotubes (MWCNTs) placed under nitrogen (N 2 ) and argon (Ar) microwave plasma in order to functionalize covalently their side walls with nitrogen containing groups. X-ray photoelectron spectroscopy (XPS) study shows surface modification of the MWCNTs with imine, amine, nitride and amide groups grafted on the side walls. Due to the functional groups, homogenous distribution of MWCNTs in solvent could be obtained. For photovoltaic device fabrication MWCNTs film was casted over n-Si wafer and poly(3-octylthiophene) solution was infiltered. Devices with functionalized MWCNTs show short circuit current density ( J sc ), open circuit voltage ( V oc ), fill factor (FF) and power conversion efficiency ( η ) as 1.8 mA/cm 2 , 0.20 V, 24% and 0.086%, respectively. In the composite film functionalized MWCNTs facilitate photo induced charge separation and efficient holes transportation, suppressing recombination of photo generated charges.