Electric-field-induced structuring and rheological properties of kaolinite and halloysite

Electric-field-induced structuring of kaolinite and halloysite particles was studied in respect to their electrorheological (ER) response in silicone oil and in paraffin dispersions. The structural and morphological properties of both clay minerals were studied by XRD, FTIR, SEM, TEM and TGA techniques. The dipolar arrangement induced under application of an electric field was investigated by 2D-WAXS and optical microscopy techniques. The ER response of the samples was measured by both the shear rate controlled method and bifurcation tests. Kaolinite particle dispersions were found to have an improved ER response relative to dispersions of halloysite particles. Finally, the electric currents of these ER fluids were measured and the results revealed differences in the current-magnitude between halloysite- and kaolinite-based silicone oil dispersions.