A simple model of the high-frequency dynamic mobility in concentrated suspensions

• Autores: Ahualli, Silvia; Delgado, Angel V.; Grosse, Constantino
• Año de publicación: 2006
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Dynamic mobility; Electroacoustic methods; Hydrodynamic interactions; Concentrated dispersions
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

Because electroacoustic techniques are gaining interest in many fields of colloid science, a number of theories dealing with the phenomenon of electrophoresis in high-frequency (on the order of the MHz) electric fields have been developed. In the present work we propose a straightforward derivation of a simple formula for the dynamic mobility of colloidal particles in mildly concentrated systems. Starting with a simple expression for the electrophoretic mobility in dilute suspensions, given as a function of the zeta potential and of the dipole coefficient, we introduce successive corrections related to: i) the back flow of fluid induced by the electrophoretic motion of  the particles; ii) the electrostatic interactions among particles; iii) the difference between the macroscopic and the external electric fields; iv) the difference between the zero-momentum and the laboratory reference frames. Considering furthermore that the frequency dependence of the dipole coefficient is due to the Maxwell-Wagner-O’Konski double-layer relaxation, we obtain a mobility expression that compares well with other (semi)analytical models and (in proper conditions) with numerical cell-model calculations. However, its main merit is that it allows to understand, to a large extent, the physical origin of the frequency and volume fraction dependences of the dynamic mobility.
Fil: Ahualli, Silvia. Universidad de Granada; España
Fil: Delgado, Angel V.. Universidad de Granada; España
Fil: Grosse, Constantino. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina