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KIMURA Hiroshi
Title Associate Professor
Department Department of Chemistry and Biomolecular Science
Course Materials Chemistry Course

Research fields

(1) The electrically induced viscosity change of a deionized hectorite aqueous dispersion under an alternating current (AC) electric field was investigated. The hectorite dispersion showed a reversible viscosity change when an AC electric field (< ca. 0.01 Hz) of the order of a few V/mm was applied and removed thereafter. Regarding the mechanism of reversible viscosity change, it can be considered that the hectorite clay of the dispersion are well dispersed as individual one or as small flocs without an electric field, and those form a three-dimensional network structure, which returns to the original dispersion state upon removal of the alternating electric field.　　　　　　 　 (2) The drying patterns of droplets of hectorite aqueous suspensions were studied. It was observed that the drying pattern was ring shaped in the absence of salt and mountain shaped in the presence of salt.　It is highly plausible that the house-of-cards network structure prevents the hectorite particles from moving toward the periphery of the droplet in the drying process. It was revealed that the dispersion state of the hectorite particle in the water dominates the drying pattern of the hectorite suspension.　 　(3) It was discovered that the sedimentation velocity of colloidal particles in water increased drastically when an electric field of the order of a few V/mmDC was applied. It is highly plausible that the particles gather each other and form some flocs, which leads to the increase in its sedimentation velocity.　

Fig1 Close-up pictures of aqueous colloidal suspension under an electric field

Research Keywords

Electrorheology Drying Dissipative Structure Dispersion State Control

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