Dresden 2009 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 12: POSTERS Magnetic Soft Matter

CPP 12.2: Poster

Tuesday, March 24, 2009, 14:00–16:30, P3

Experiments on dynamics of transients in magnetic colloids — •Dmitry Borin and Stefan Odenbach — Technische Universität Dresden, Institute of Fluid Mechanics, Chair of Magnetofluiddynamics, 01062 Dresden, Germany

The detailed understanding of the internal physical nature of slow relaxation phenomena in disordered materials is still not reached. Therefore the study of relaxation phenomena in magnetic suspensions of single-domain Brownian nanoparticles (ferrofluids) is highly interesting for the general theory of dynamical phenomena in complex and soft systems. As it is known from previous studies, some ferrofluids show a long time reaction to a stepwise change of shear stress at constant magnetic field strength, as well as to a stepwise change of magnetic field strength at constant shear rate. The goal of this work was to shed some light on this temporal behavior. We performed experiments on magnetite based ferrofluids with a small particle-particle interaction parameter, as well as on cobalt based ferrofluids, containing particles which are large enough to form chain-like structures. The obtained results are compared with measurements performed on magnetorheologial suspensions consisting of non Brownian particles. This comparison enables a study of the fundamental role of the Brownian effects for the macroscopic rheological properties of such suspensions.