Experimental investigation of stability and thermophysical properties of carbon nanotubes suspension in the presence of different surfactants

Abstract

Since carbon nanotubes (CNTs) are unstable in different polar solvents such as water, using surfactants can open a new gateway for solving the challenge by attaching non-covalent hydrophilic bonds. Here, the influence of different surfactants including gum arabic (GA), cetyl trimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) on stability and thermophysical properties of multi-walled carbon nanotubes (MWCNTs) in aqueous media is experimentally investigated. To reach this purpose, aqueous suspension of surfactant–MWCNT was synthesized in the ratios 0.5–1, 1–1 and 2–1. Zeta potential was used to determine stability of above-mentioned suspensions as a common method. Dynamic light scattering analysis was also employed to determine particles size distribution. The results indicated relative stability of suspensions in all ratios. It was also found that the minimum particle size was obtained in the presence of the ratio 1–1 of SDS and CTAB. Thermophysical properties of above-mentioned suspensions including viscosity, shear stress, electrical conductivity, surface tension and density were also studied at the range of 20–80 °C. The results indicated an increase in the electrical conductivity, density, viscosity, shear stress and a decrease in the surface tension (except in GA) of suspensions in all concentrations relative to pure water in constant temperature. As temperature increases, the electrical conductivity increases significantly, while the viscosity, shear stress, density and surface tension decreases more or less for all concentrations.