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Please use this identifier to cite or link to this item: http://hdl.handle.net/10481/38669

Title: Inverse magnetorheological fluids
Authors: Rodríguez-Arco, Laura
López-López, Modesto T.
Zubarev, Andrey
Gdula, Karolina
García López-Durán, Juan de Dios
Issue Date: Jun-2014
Abstract: We report a new kind of field-responsive fluids consisting of suspensions of diamagnetic (DM) and ferromagnetic (FM) microparticles in ferrofluids. We designate them as inverse magnetorheological (IMR) fluids for analogy with inverse ferrofluids (IFFs). Observations on the particle self-assembly in IMR fluids upon magnetic field application showed that DM and FM microparticles were assembled into alternating chains oriented along the field direction. We explain such assembly on the basis of the dipolar interaction energy between particles. We also present results on the rheological properties of IMR fluids and, for comparison, of IFFs and bidispersed magnetorheological (MR) fluids. Interestingly, we found that upon magnetic field, the rheological properties of IMR fluids were enhanced with respect to bidispersed MR fluids with the same FM particle concentration, by an amount greater than the sum of the isolated contribution of DM particles. Furthermore, the field-induced yield stress was moderately increased when up to 30 % of the total FM particle content was replaced with DM particles. Beyond this point, the dependence of the yield stress on the DM content was non-monotonic, as expected for FM concentrations decreasing to zero. We explain these synergistic results by two separate phenomena: the formation of exclusion areas for FM particles due to the perturbation of the magnetic field by DM particles, and the dipole-dipole interaction between DM and FM particles, which enhances the field-induced structures. Based on this second phenomenon, we present a theoretical model for the yield stress that semi-quantitatively predicts the experimental results.
Sponsorship: Projects 12-01-00132, 13-02-91052, 13-01-96047, 14-08-00283 (Russian Fund of Fundamental Investigations), 2.1267.2011 (Ministry of Education of Russian Federation), the Act 211 (Government of the Russian Federation № 02.A03.21.0006). The University of Granada (Acción Integrada con Rusia; Plan Propio 2011). L. Rodríguez-Arco acknowledges financial support by Secretaría de Estado de Educación, Formación Profesional y Universidades (MECD, Spain) through its FPU program.
Publisher: Royal Society of Chemistry
Keywords: Magnetorheological fluids
URI: http://hdl.handle.net/10481/38669
ISSN: 1477-683X
Rights : Creative Commons Attribution-NonCommercial-NoDerivs 3.0 License
Citation: Rodríguez-Arco, L.; et al. Inverse magnetorheological fluids. Soft Matter, 10: 6256-6265 (2014). [http://hdl.handle.net/10481/38669]
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