Structure induced in suspensions by a magnetic field

Grasselli, Yan; Bossis, Georges; Lemaire, Élisabeth

doi:10.1051/jp2:1994127

Cited by 37 publications

(43 citation statements)

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“…We particularly mention the aggregation process and, on larger time scales, the phase separation which has been shown experimentally and studied both theoretically and numerically. [3][4][5][6][7][8] Furthermore the microscopic structure of the aggregates arising in ER fluids has been studied. [9][10][11][12][13] Electrostatic surface effects, which are assumed to be important for small aggregates, have been investigated and it has been shown that these surface effects depend strongly on the internal structure of the aggregates.…”

Section: Introductionmentioning

confidence: 99%

Static yield stresses and shear moduli in electrorheological fluids

Clercx

Bossis

1995

The Journal of Chemical Physics

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A previously introduced method to study many-body electrostatic interactions among spherical particles ͓H. J. H. Clercx and G. Bossis, Phys. Rev. E 48, 2721 ͑1993͔͒ has been used to study yield stresses and shear moduli for simple cubic ͑SC͒, simple hexagonal ͑SH͒, and body-centered tetragonal ͑BCT͒ structures, with polarizable spheres on the lattice sites, to gain insight in the electrostatic response of these structures to externally applied stresses. The shear modulus G and the static yield stress s have been calculated for several ratios of particle to fluid dielectric constant. It turned out that interchain interactions are very weak in SC and SH structures which is confirmed by the nearly linear dependence of G and s ͑even no weak maximum appears in these curves͒. The results reported for the BCT structure are rather unexpected, because both G and s suddenly decrease to zero at large volume fractions. We discuss the data for G and s and compare some of these results with data obtained by employing the dipolar approximation and the Laplacian relaxation technique to calculate the electrostatics. This comparison shows that in general a multipolar approach is indispensable in obtaining correct values for G and ; especially the dipolar approximation underestimates these quantities. As an example the strength of single vs double chains has been compared for both the dipolar approach and a multipolar calculation. In the dipolar approximation the double chain structure seems strongest. However, multipolar calculations show that the single chain structure is stronger than the double chain structure.

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Section: Introductionmentioning

confidence: 99%

Static yield stresses and shear moduli in electrorheological fluids

Clercx

Bossis

1995

The Journal of Chemical Physics

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“…The interaction between the particles impedes to a certain level of the shear stress without breaking and simultaneously increases the viscosity of the fluids [32]. In many cases, the effect of MRF is described by Bingham Plastic model [33].…”

Section: Rheology Of Mrfmentioning

confidence: 99%

Optimal Design Methodology of Magnetorheological Fluid Based Mechanisms

Nguyen¹,

Choi²

2012

Smart Actuation and Sensing Systems - Recent Advances and Future Challenges

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“…We shall use a theory previously developed to predict the size of the aggregates in the presence of a magnetic field (Grasselli et al 1994). Supposing a network of ellipsoidal aggregates aligned on the field direction, the magnetic energy per unit volume is given by:…”

Section: Theorymentioning

confidence: 99%

“…The quantity n r is a demagnetization factor expressing the decrease of the field induced by the presence of the other aggregates around the reference one and given by (Grasselli et al 1994): …”

Section: Theorymentioning

confidence: 99%

Synthesis and magnetorheology of suspensions of submicron-sized cobalt particles with tunable particle size

López–López¹,

Kuzhir²,

Meunier³

et al. 2010

J. Phys.: Condens. Matter

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. Synthesis and magnetorheology of suspensions of submicronsized cobalt particles with tunable particle size. Journal of Physics: Condensed Matter, IOP Publishing, 2010, 22, pp.324106 Abstract. Different samples of cobalt powder were synthesized. Particle size and shape were characterized by electron microscopy and light scattering. These measurements showed that the synthesized powders consisted of monodisperse spheres with average diameters ranging between 63 and 760 nm. These powders were used for the preparation of magnetorheological (MR) fluids by dispersing them in silicone oil. The MR properties of these MR fluids were investigated. It was found that particle size did not have much influence on the MR response of MR fluids, for average particle diameters larger than 100 nm. On the other hand, the MR response decreased appreciably when average particle diameter was diminished below 100 nm; a theory based on the change of the aggregates'shape with the size of the particles could explain these observations. IntroductionSuspensions of colloidal magnetic particles are complex fluids that exhibit magnetic field-dependent rheological (flow) properties. This feature is known as magnetorheological (MR) effect. According to the size of the dispersed particles, these suspensions can be divided in: (i) ferrofluids (FF), which are dispersions of ferro-or ferrimagnetic nanoparticles (approx. 10 nm in diameter) in a carrier liquid (Odenbach 2006); and (ii) MR fluids, which are dispersions of micron-sized particles of magnetizable materials in a carrier liquid (Bossis et al 2002). Upon magnetic field application, particles of FF and MR fluids experience attractive magnetostatic forces, which lead to the formation of particle structures aligned in the field direction. The formation of these structures, which strengthen the suspension and oppose to the flow, is the basic phenomenon underlying the MR effect. The formation of field-induced particle aggregates, i.e. the intensity of the MR effect, will depend on the ratio of the magnetic interaction energy to the thermal energy. For two magnetic dipoles this ratio is given by:

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Structure induced in suspensions by a magnetic field

Cited by 37 publications

References 0 publications

Static yield stresses and shear moduli in electrorheological fluids

Static yield stresses and shear moduli in electrorheological fluids

Optimal Design Methodology of Magnetorheological Fluid Based Mechanisms

Synthesis and magnetorheology of suspensions of submicron-sized cobalt particles with tunable particle size

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