title: Isopycnic Focusing Study of the Transient State in the Settling of Colloidal Particles
abstract: Various effective field forces can generate the concentrating flux of the colloidal particles. Centrifugal field forces were used in this work to study the kinetics of the transport phenomena and the effect of interparticle interactions of the model silica suspension. Isopycnic focusing of the colored density marker beads was used to visualize the evolution and final quasi-equilibrium shape of the density gradient formed in silica suspension. Many operational parameters and experimental conditions (thickness of the liquid layer in measuring cells, intensity of the centrifugal forces, average concentration of the silica particles, and geometrical shape of the measuring cells) were tested to evidence their influence on the concentration and density gradient formation. The main objective was to apprehend the processes governing isoperichoric focusing in thin layers under model static conditions which is necessary for the optimization of isoperichoric focusing field-flow fractionation dynamic experiments carried out under conditions of hydrodynamical flow as an active factor of the separation by focusing effect. The experimental results were compared with the hypothetical model of noninteracting particles to demonstrate the effect of the actual interparticle interactions.
authors.affiliation: Pole Sciences et Technologie, Universite de La Rochelle, Avenue Marillac, La Rochelle, Cedex 01, 17042, France
authors.initials: J
authors.lastname: Janca
authors.initials: M
authors.lastname: Spirkova