Changes of viscosity in stevensite aqueous dispersions with application of an electric field of the order of a few V/mm

A change in the viscosity of a deionized stevensite aqueous dispersion under an electric field of the order of a few V/mm was recently discovered. The dispersion shows a reversible change of viscosity with the application and removal of an AC electric field. Regarding the mechanism of the reversible viscosity change, it can be considered that the by applying an electric field, the stevensite forms some flocs and a weak network structure, which leads to the increased viscosity, while it returns to a well-dispersed state and its original viscosity by removing the electric field. The viscosity response of the stevensite dispersion for an AC electric field was faster than that of the hectorite dispersion in the same measuring condition. It is speculated that the quick viscosity change would be related to the unique charge distribution on the stevensite, which is known to form a finer network structure than hectorite, beyond a critical concentration of salt. This finding offers great potential for controlling the dispersion state and sedimentation/floatation velocity, by an electric field, of various colloidal particles dispersed in the clay mineral dispersions.