Dispersion of Carbon Nanotubes in Liquids

Production processes for carbon nanotubes often produce mixtures of solid morphologies that are mechanically entangled or that self-associate into aggregates. Entangled or aggregated nanoparticles often need to be dispersed into fluid suspensions in order to develop materials that have unique mechanical characteristics or transport properties. This paper reviews the effects of milling, ultrasonication, high shear flow, elongational flow, functionalization, and surfactant and dispersant systems on morphology of carbon nanotubes and their interactions in the fluid phase. Multiwalled carbon nanotubes (MWNTs) have been used as an example model system for experimental work because they have been available in engineering-scale quantities and can be dispersed reproducibly in a variety of solvents and polymers. Their size scales, 30–50 nm in average diameter and 5–50 microns in length, permit MWNT dispersions to be investigated using transmission electron microscopy, scanning electron microscopy, and in some cases, light microscopy.