Dispersion stability of multi-walled carbon nanotubes in refrigerant with addition of surfactant

In order to apply surfactant for improving the stability of multi-walled carbon nanotubes (MWCNTs) nanorefrigerant in refrigeration system, the effects of surfactant type, ultrasonication time, surfactant concentration, initial MWCNT concentration and MWCNT structure on the dispersion stability of MWCNTs in refrigerant with surfactant are investigated in the present study. In the experiments, R141b was selected as host refrigerant for the preparation of nanorefrigerant, UV-vis spectrophotometer method was used to quantitatively evaluate the dispersion stability of MWCNTs, and Fourier transform infrared spectroscopy (FTIR) as well as dynamic light scattering (DLS) analysis were performed to understand the dispersion stability mechanism. The experimental results show that the good dispersion stability of MWCNTs is obtained with addition of sodium dodecylbenzene sulfonate (SDBS) as a surfactant, and the increase of ultrasonication time improves the dispersion stability. The relative concentration increases with the increase of SDBS concentration and then decreases, while increases with the decrease of initial MWCNT concentration at the optimal SDBS concentration. It is also found that the decrease of MWCNT length or outer diameter leads to the increase of relative concentration.