Original scientific paper

Scaling between Viscosity and Hydrodynamic / Magnetic Forces in Magnetic Fluids

Modesto T. López-López ; Department of Applied Physics, Campus de Fuentenueva s/n, Faculty of Sciences, University of Granada, Granada, Spain
Juan D. G. Durán ; Department of Applied Physics, Campus de Fuentenueva s/n, Faculty of Sciences, University of Granada, Granada, Spain
Angel V. Delgado ; Department of Applied Physics, Campus de Fuentenueva s/n, Faculty of Sciences, University of Granada, Granada, Spain
Fernando González-Caballero ; Department of Applied Physics, Campus de Fuentenueva s/n, Faculty of Sciences, University of Granada, Granada, Spain

Abstract

The aim of this work is the investigation of the magnetorheological behavior, under both simple
steady- and oscillatory-shear flow regimes, of fluids composed by micron-sized iron particles
(average diameter 930 ± 330 nm) dispersed in silicone oil. Magnetic fields ranging from 279
A/m (0.35 mT) to 1727 A/m (2.17 mT) were applied to the suspensions. The effect of silica
nanoparticles as stabilizer of the suspensions has also been considered. The study has been
made by the scaling between the viscosity of the suspension and the ratio of hydrodynamic to
magnetic forces acting on the dispersed particles, given by the dimensionless Mason number
(Mn), and interpreted in terms of the chainlike model taken from the theory of Martin and Anderson
(J. Chem. Phys. 104 (1996) 4814-4827). The model is quite well accomplished for iron
suspensions of different (20 % and 30 %) volume fraction without any stabilizing agent. The
presence of added silica nanoparticles in the suspension hinders the formation of regular iron
structures induced by the magnetic field, especially at the lowest applied magnetic fields. Thus
the model becomes not applicable to these cases. Viscometry has been shown to be more adequate
than oscillometry for scaling the viscous properties of magnetorheological suspensions
with microscopic interparticle forces in terms of Mn number.

Keywords

magnetic colloids; viscosity; magnetorheology

Hrčak ID:

18668

URI

https://hrcak.srce.hr/18668

Publication date:

30.11.2007.

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