Abstract
Investigations of rheological properties of ferrofluids have shown strong changes of the viscosity in magnetic fluids with an applied magnetic field. The change of the viscosity – the magnetoviscous effect – can theoretically be described with chain and structure formation under the influence of a magnetic field. Moreover, the formation of these structures leads to the appearance of viscoelastic effects or other non-Newtonian features like yield stress in ferrofluids with an applied magnetic field. With a shear rate controlled rheometer – as it as been used in former experiments – the yield stress could not be investigated directly. Therefore the results concerning a field dependent yield stress based on an extrapolation of shear controlled measurements. For the direct investigations of the yield stress, a dedicated stress controlled rheometer is required, allowing direct investigations of the magnitude and field dependence of this effect. In this work the design of the stress controlled rheometer with its main parameters has been described in detail. The rheological investigations with differently composed fluids show that the stress controlled rheometer enables direct measurements of even small yield stresses in ferrofluids as well as large effects like they are found in magnetorheological fluids (MRF).
REFERENCES
[1] Buschow KHJ: Handbook of Magnetic Materials, Elsevier-Verlag, Volume 16 (2006).Search in Google Scholar
[2] Odenbach S: Magnetoviscous Effects in Ferrofluids, Lecture Notes in Physics m71, Springer-Verlag, Berlin (2002).Search in Google Scholar
[3] Odenbach S: Magnetoviscous and viscoelastic effects in ferrofluids, International Journal of Modern Physics B 14 (2000) 1615.10.1142/S0217979200001692Search in Google Scholar
[4] Odenbach S and Stoerk H: Shear dependence of field-induced contributions to the viscosity of magnetic fluids at low shear rates, Journal of Magnetism and Magnetic Materials 183 (1998) 188.Search in Google Scholar
[5] Pop LM and Odenbach S: Investigation of the microscopic reason for the magnetoviscous effect in ferrofluids studied by small angle neutron scattering, Journal of Physics - Condensed Matter 18 (2006) 2785.10.1088/0953-8984/18/38/S17Search in Google Scholar
[6] Pop LM: Investigations of the microstructure of ferrofluids under the influence of a magnetic field and shear flow, Dissertation of Universität Bremen (2006).Search in Google Scholar
[7] Pop LM, Odenbach S, Wiedenmann A, Matoussevitch, Bönnemann H: Microstructure and rheology of ferrofluids, Journal of Magnetism and Magnetic Materials 289 (2005) 303.10.1016/j.jmmm.2004.11.086Search in Google Scholar
[8] Thurm S and Odenbach S: Magnetic separation of ferrofluids, Journal of Magnetism and Magnetic Materials 252 (2002) 247.10.1016/S0304-8853(02)00679-0Search in Google Scholar
[9] Thurm S and Odenbach S: The influence of magnetic separation on the magnetoviscous behavior of ferrofluids, Magnetohydrodynamics 3 (2001) 291.Search in Google Scholar
[10] Odenbach S, Rylewicz T, Heyen M: A rheometer dedicated for the investigation of viscoelastic effects in commercial magnetic fluids, Journal of Magnetism and Magnetic Materials 201 (1999) 155.Search in Google Scholar
[11] Odenbach S, Rylewicz T, Rath H: Investigation of the Weissenberg effect in suspensions of magnetic nanoparticles, Physics of Fluids 11 (1999) 2901.10.1063/1.870148Search in Google Scholar
[12] Tang X and Conrad H: Quasi-Static Measurements on a Magnetorheological Fluid, Journal of Rheology 40 (1996) 1167.Search in Google Scholar
[13] Bossis G, Mathis C, Mimouni Z, Paparoditis C: Magnetoviscosity of micronic suspensions, Europhysics Letters 11 (1990) 133.10.1209/0295-5075/11/2/007Search in Google Scholar
[14] Lemaire E, Bossis G, Volkova O: Deformation and rupture mechanisms of ER and MR fluids, International Journal of Modern Physics B 10 (1996) 3173.Search in Google Scholar
[15] Mou T, Flores GA, Liu J, Bibette J, Richard J: The Evolution of Field-Induced Structure of Confined Ferrofluid Emulsions, International Journal of Modern Physics B 8 (1994) 2779.Search in Google Scholar
[16] Volkova O, Bossis G, Guyot M, Bashtovoi V, Reks A: Magnetorheology of magnetic holes compared to magnetic particles, Journal of Rheology 44 (2000) 91.Search in Google Scholar
[17] Ginder JM, Davis LC, Elie LD: Rheology of magnetorheological fluids: models and measurements, Proceedings of the 5th International Conference on Electro-Rheological Fluids, Magneto-Rheological Suspensions and Associated Technology (1996).Search in Google Scholar
[18] Rosensweig RE: Ferrohydrodynamics, Cambridge University Press, Cambridge (1985).Search in Google Scholar
[19] www.femlab.de.Search in Google Scholar
[20] Bossis G, Lemaire E, Volkova O: Yield stress in magnetorheological and electrorheological fluids: a comparison between microscopic and macroscopic structural model, Journal of Rheology 41 (1997) 687.10.1122/1.550838Search in Google Scholar
[21] Lemaire E and Bossis G: Yield stress and wall effects in magnetic colloidal suspension, Journal of Physics D 24 (1991) 1473.Search in Google Scholar
[22] Bossis G and Lemaire E: Yield stresses in magnetic suspensions, Journal of Rheology 35 (1991) 1345.Search in Google Scholar
[23] Lemaire E, Bossis G, Grasselli Y: Yield stress and structuration of magnetorheological suspensions, Journal of Magnetism and Magnetic Materials 122 (1993) 51.10.1016/0304-8853(93)91037-8Search in Google Scholar
[24] Thurm S and Odenbach S: Particle size distribution as key parameter for the flow behavior of ferrofluids, Physics of Fluids 15 (2003) 1658.Search in Google Scholar
© 2008 Hamid Shahnazian et al., published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.
