Viscoelasticity of mono- and polydisperse inverse ferrofluids

Abstract

We report on measurements of a magnetorheological model fluid created by dispersing nonmagnetic microparticles of polystyrene in a commercial ferrofluid. The linear viscoelastic properties as a function of magnetic field strength, particle size, and particle size distribution are studied by oscillatory measurements. We compare the results with a magnetostatic theory proposed by De Gans et al. [Phys. Rev. E 60, 4518 (1999)] for the case of gap spanning chains of particles. We observe these chain structures via a long distance microscope. For monodisperse particles we find good agreement of the measured storage modulus with theory, even for an extended range, where the linear magnetization law is no longer strictly valid. Moreover we compare for the first time results for mono- and polydisperse particles. For the latter, we observe an enhanced storage modulus in the linear regime of the magnetization.

Magnetorheological Fluids Based on Ionic Liquids

“…2E), which consequently lead to significant changes in the viscous behavior of the fluid. [15,41] In Figure 3D and E it can be seen that the maximum shear stresses and viscosity values are reached with a magnetic field of 282 kA m -1 ; as the saturation of the sample was already reached, the use of higher intensities (321 kA m -1 ) does not have a significant effect on the rheological properties. Note that the investigated MRFs show a plastic or Bingham-type behavior in the presence of a magnetic field (Fig.…”

“…When a magnetic field is applied to MRFs, the interactions between their magnetic particles become much stronger, so that complex structures in the form of thick chains of magnetic particles develop. [15,41] To investigate this phenomenon for the systems of interest to this report, a dilute dispersion of magnetic particles in IL 8 (MRF12 in Table 1) was subjected to magnetization measurements and optical microscopy (a low concentration of particles in the fluids allows for a better observation of the dispersions). In the case of magnetization measurements, the diamagnetism of the sample holder was observed because of the low concentration of magnetic particles in the sample, as shown in Figure 2A.…”

The Field-Dependent Rheological Properties of Magnetorheological Fluids Featuring Plate-Like Iron Particles

“…It is expected that the formation of less compact anisotropy in iron particles creates weak sedimentation and good redispersibility. Even though some research works on the rheological properties and applications (De Vicente et al, 2010;Shah et al, 2013Shah et al, , 2014aPhu et al, 2014;Upadhyay et al, 2014) of the plate-like iron particles based MR fluids have been undertaken, a solid work on the field-dependent rheological properties under various conditions is considerably rare.…”

Microcapillary flow behavior of magnetic nanofluids in the presence of plate shaped bentonite particles

“…de Gans et al [16] have also dispersed monodispersed silica spheres in an organic ferrofluid known as inverse ferrofluid and studied linear viscoelastic behavior as a function of frequency, magnetic field, and silica volume fraction with a specially designed magnetorheometer. Saldivar-Guerrero et al [19] studied the viscoelasticity of mono-and polydisperse inverse ferrofluid. They used polystyrene particles and observed an enhanced storage modulus in the linear regime of magnetization for the polydispersed nonmagnetic particles dispersed in a commercial ferrofluid.…”