Particle size distribution as key parameter for the flow behavior of ferrofluids

Abstract

One of the most promising properties of ferrofluids is the possibility to significantly influence their flow behavior by moderate magnetic fields. An exact understanding of the origin and mechanism of this effect is essential in order to develop future applications in the field of magnetoviscosity. In particular, the influence of the small fraction of larger particles, which can show strong, magnetic field induced interparticle interactions, is in the focus of our interest. Theoretical calculations show that the interaction between larger particles is strong enough to form chain-like structures, which in turn dominate the flow behavior. To investigate this effect more deeply, we change — by a magnetic separation process in a controlled, measurable way — the volume fraction mainly of these larger particles. Thereafter the separated fluid fractions and the original fluid are investigated in magnetization and rheological measurements, which are compared with theoretical calculations.