Solid to liquid transition of inverse ferrofluids under shear

R. Saldivar-Guerrero^{1, 3} - R. Richter¹ - I. Rehberg¹ - N. Aksel² - L. Heymann² - O. S. Rodriguez-Fernández³

¹ Experimentalphysik V, Universität Bayreuth, D-95440 Bayreuth, Germany
² Lehrstuhl für Technische Mechanik und Strömungsmechanik, Universität Bayreuth, D-95440 Bayreuth, Germany
³ Centro de Investigación en Química aplicada, 25100 Saltillo, Coahuila México

Abstract
By dispersing microsized monodisperse polystyrene particles in a ferrofluid, an ideal magneto-rheological model fluid is created. Due to the dipolar interactions of the particles, the hybrid fluid shows solid-like behavior under the shear, i.e., one has to overcome an apparent yield stress before flow sets in. We compare this quantity with theoretical predictions for different magnetic fields and volume fractions of nonmagnetic particles. Figs 3, Refs 6.