Regulation of dispersion of carbon nanotubes in binary water+1-Cyclohexyl-2-pyrrolidone mixtures

Abstract

The microstructure and electrical conductivity of suspensions of multi-walled carbon nanotubes (MWCNTs) in binary water+1-Cyclohexyl-2-pyrrolidone (CHP) liquid mixtures were studied in the temperature interval of 253–318K, in the heating and cooling cycles. The concentration of MWCNTs was varied in the interval between 0 and 1wt% and the content of water in a binary mixture X=[water]/([CHP]+[water]) was varied within 0–1.0. The experimental data have shown that dispersing quality of MWCNTs in a mixture of good (CHP) and bad (water) solvents may be finely regulated by adjustment of composition of the CHP+water mixtures. The aggregation ability of MWCNTs in dependence on X was discussed. The surface of MWCNT clusters was highly tortuous, its fractal dimension df increased with increase of X, approaching ≈1.9 at X→1. It was concluded that the surface tension is not suitable characteristic for prediction of dispersion ability in the mixture of good and bad solvents. The electrical conductivity data evidenced the presence of a fuzzy-type percolation with multiple thresholds in the systems under investigation. This behavior was explained by formation of different percolation networks in dependence of MWCNT concentration.