Study of the magnetorheology of aqueous suspensions of extremely bimodal magnetite particles |
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Authors: | J L Viota J D G Durán A V Delgado |
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Institution: | (1) Department of Physics, University of Jaén, 23071 Jaén, Spain;(2) Department of Applied Physics, School of Sciences, University of Granada, 18071 Granada, Spain |
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Abstract: | In this paper we describe the magnetorheological behavior of aqueous suspensions consisting of magnetite particles of two
size populations, in the micrometer and nanometer scale, respectively. Previous works on the magnetorheology of oil-based
fluids demonstrated that the addition of nanoparticles has a very significant effect on the intensity of the magnetorheological
effect. The present contribution confirms such results in the case of aqueous fluids, based on the dependence of the yield
stress and the viscosity of the bimodal suspensions on both the composition of the mixtures and the magnetic field strength.
It is demonstrated that for a given concentration of micrometer particles, increasing the amount of nanometer magnetite provokes
a clear enhancement in the yield stress for all the magnetic fields applied. This is proposed to be due to the formation of
heterogeneous aggregates that improve the stability of the suspensions and ease the building of well-arranged field-induced
structures. The behavior of both the yield stress and the post-yield viscosity agrees better with the predictions of standard
chain models when the relative proportion of both types of particles confers optimum stability to the bimodal dispersions. |
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Keywords: | PACS" target="_blank">PACS 47 57 Qk Rheological aspects 83 80 Gv Electro- and magnetorheological fluids 83 80 Hj Suspensions dispersions pastes slurries colloids |
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