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Croatica Chemica Acta, Vol.80 No.3-4 November 2007. -

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.

magnetic colloids; viscosity; magnetorheology

Autor: Modesto T. López-López - ; Department of Applied Physics, Campus de Fuentenueva s-n, Faculty of Sciences, University of Granada



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