Ferrofluids: Magnetically Controllable Fluids and Their Applications

Abstract

The appearance of field and shear dependent changes of viscosity in ferrofluids opens possibilities for future applications e.g. in damping technologies. To enhance the effects, it is necessary to understand the observed magnitudes of magnetoviscosity in commercial ferrofluids from a microscopic point of view. Starting from experimental results, it is described how the magnetoviscous effects can be explained by chain formation of a small fraction of large particles in the fluid. With a dedicated experiment ferrofluids are separated into fractions with high and low amount of such particles. The rheological characterization of the fractions prove the aforementioned model. Furthermore it leads to additional information concerning viscoelasticity of the suspensions in a magnetic field.