ELECTRIC-FIELD INDUCED STRUCTURE IN DENSE SUSPENSIONS

This paper presents measurements of the structure of dense suspensions of colloidal spheres subject to electric fields. Scattering dichroism measurements, performed as a function of wavelength, probed the anisotropy in the pair distribution function of submicrometer silica spheres, following the application of electric fields. The results indicate that at lower concentrations, high aspect ratio fibrils are formed upon application of the electric fields. As the concentration is increased, branching of the fibrillar structure reduces the anisotropy of the suspension with a subsequent decrease of the measured dichroism. The time scales of structure formation and relaxation are also considered. The response time of the fluid decreases as the applied field is increased and as the particle volume fraction is decreased. The relaxation time increases with increasing particle size but is insensitive to concentration. © 1993 Academic Press, Inc.