Electric surface properties of fractal aggregates - rotational and translational electrokinetics

Fractal aggregates from gamma-Al2O3 obtained by flame hydrolysis with diffe rent hydrodynamic radius are studied by electric light scattering (rotation al) and electrophoresis (translational) electrokinetics. The nonequilibrium , electric surface properties of the aggregates characterized by their elec tric polarizability are studied. The electric polarizability depends linear ly on the aggregates dimensions and decreases with indifferent electrolyte concentration increase tending to a constant value. The aggregate structure (the existence of "inner" counterions in the pore space) could be supposed as responsible for an "internal" electric polarizability, relaxing in the kHz region. The electrophoretic mobilities do not depend on the kappa a-par ameter (kappa(-1)=thickness of diffuse double layer, a = radius of initial spherical gamma-Al2O3 particles). (C) 1999 Elsevier Science B.V. All rights reserved.