Magnetic colloids were formulated by dispersion of magnetic oxide spheres in water. Their rheological behavior was investigated for a wide range of particle diameters covering in detail the magnetic single-multidomain transition and therefore spanning the gap between ferrofluids and conventional magnetorheological fluids. The magnetoviscous effect (i.e., the ratio between the viscosity increment under field and the viscosity value in the absence of field) was found to reach a maximum for a critical particle size in the single-multidomain transition region. The observations were explained in terms of magnetization changes with particle size. The results obtained are applicable to any magnetic material (not only iron oxides) and therefore constitute a new route to enhance the magnetorheological effect. For very small particle sizes (in the superparamagnetic region), thermal motion plays a crucial role and the dimensionless viscosity scales with the Peclet number as expected for Brownian Hard Spheres. For larger particle sizes and , the dimensionless viscosity scales with the Mason number and closely follows the structural viscosity model under the mean magnetization approximation.
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Rheological behavior of magnetic colloids in the borderline between ferrofluids and magnetorheological fluids
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July 2019
Research Article|
July 01 2019
Rheological behavior of magnetic colloids in the borderline between ferrofluids and magnetorheological fluids
Keshvad Shahrivar
;
Keshvad Shahrivar
1
Biocolloid and Fluid Physics Group and Excellence Research Unit “Modeling Nature” (MNat), Department of Applied Physics, Faculty of Sciences, University of Granada
, C/Fuentenueva s/n, 18071 Granada, Spain
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Jose R. Morillas
;
Jose R. Morillas
1
Biocolloid and Fluid Physics Group and Excellence Research Unit “Modeling Nature” (MNat), Department of Applied Physics, Faculty of Sciences, University of Granada
, C/Fuentenueva s/n, 18071 Granada, Spain
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Yurena Luengo;
Yurena Luengo
2
Department of Energy, Environment and Health, Institute of Material Science of Madrid (ICMM-CSIC)
, Madrid, Spain
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Helena Gavilan;
Helena Gavilan
2
Department of Energy, Environment and Health, Institute of Material Science of Madrid (ICMM-CSIC)
, Madrid, Spain
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Puerto Morales
;
Puerto Morales
2
Department of Energy, Environment and Health, Institute of Material Science of Madrid (ICMM-CSIC)
, Madrid, Spain
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Claas Bierwisch
;
Claas Bierwisch
3
Fraunhofer IWM
, Wöhlerstraße 11, 79108 Freiburg, Germany
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Juan de Vicente
Juan de Vicente
a)
1
Biocolloid and Fluid Physics Group and Excellence Research Unit “Modeling Nature” (MNat), Department of Applied Physics, Faculty of Sciences, University of Granada
, C/Fuentenueva s/n, 18071 Granada, Spain
a)Author to whom correspondence should be addressed; electronic mail: jvicente@ugr.es
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a)Author to whom correspondence should be addressed; electronic mail: jvicente@ugr.es
J. Rheol. 63, 547–558 (2019)
Article history
Received:
February 22 2019
Accepted:
April 22 2019
Citation
Keshvad Shahrivar, Jose R. Morillas, Yurena Luengo, Helena Gavilan, Puerto Morales, Claas Bierwisch, Juan de Vicente; Rheological behavior of magnetic colloids in the borderline between ferrofluids and magnetorheological fluids. J. Rheol. 1 July 2019; 63 (4): 547–558. https://doi.org/10.1122/1.5093628
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