A new and acid-exclusive method for dispersing carbon multi-walled nanotubes in aqueous suspensions

Carbon multi-walled nanotubes (MWNTs) can be easily dispersed in water using a new and effective method herewith by pretreatment with H2O2 followed by dispersing with ammonium polyacrylic acid. The structure morphology and surface chemistry of H2O2-treated MWNTs were characterized, respectively, by transmission electron microscopy and Fourier transform-infrared spectroscopy, and the results were compared with MWNTs treated with a mixture of concentrated HNO3 and H2SO4 acids in a 3:1 volume ratio. It was found that the MWNTs with H2O2-treatment had fewer microstructure defects than those treated with concentrated acids. The dispersion stability of as-prepared aqueous suspensions was analyzed by rheology and settling experiments. The aqueous suspension prepared by the new method has neutral pH and high dispersion stability, but that prepared from the acid-treated MWNTs was acidic with pH 2–3 although their dispersion stability was also good. Besides, the dispersed suspension from the new method stayed highly fluid without becoming coagulated or gelled at solid contents up to 5 wt.%.