Influence of clay-based additive on sedimentation stability of magnetorheological fluid

Abstract

Sedimentation stability is one of the most important features of magnetorheological (MR) fluids. Clay-based additives are known for improving the stability of the MR fluids. This article describes the dependency of the clay-based additive concentration on the sedimentation stability and the rheological properties of MR fluids in non activated state (without magnetic field). The sedimentation was measured for two different base oil viscosities, two different carbonyl iron particle sizes, and additive concentration between 2 and 6 wt%. The measurements showed that the sedimentation rate exponentially decreases with the additive concentration, while the yield stress is rising. The measurements of rheological properties also showed the dependency of rheological properties of MR fluid with a clay-based additive on loading history. The influence of carrier fluid viscosity or particle size has a minor effect on the sedimentation in comparison with the clay-based additive. The addition of 6 wt% slows down the sedimentation by more than 3000 times compared to MR fluid without additives. The MR fluid with 4.85% of clay-based additive achieves slightly better sedimentation stability than commercial MR fluid LORD MRF122.

Physical Mechanisms of Magnetic Field Effects on the Dielectric Function of Hybrid Magnetorheological Suspensions

“…The decreased is a consequence of Fe microparticle sedimentation, which is an important phenomenon in the case of MRSs without additives. By adding additives such as clay additives [ 4 ], ferri-/ferromagnetic nanoparticles [ 27 ], carbon nanotubes [ 28 ], etc., a strong attenuation of the magnetic phase sedimentation in MRSs was reported.…”

“…These materials, together with magnetorheological suspensions (MRSs) and magnetorheological elastomers (MREs), belong to the class of active magnetic materials. Since the matrix is a liquid for MRSs [ 1 , 2 , 3 , 4 , 5 , 6 ] and silicone rubber for MREs, embedded with ferri-/ferromagnetic microparticles in both cases [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ], the matrix for hMRSs is a fabric of polymeric fibers doped with MRSs [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ]. The term “hybrid” refers to magnetically active materials made up of a fabric of polymeric fibers doped with MRSs [ 21 , 22 , 23 , 24 , 25 ].…”

“…When applying a magnetic field, the magnetizable phase from MRSs, MREs, and hMRSs orients along the magnetic field in aggregates with chain or column shapes. The strength of the chains depends on the magnetic properties of the magnetizable phase and the intensity of the external magnetic field [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ].…”

“…The chain formation when applying a magnetic field and its unraveling when the magnetic field is cancelled depend on the viscoelastic properties of the matrix where the magnetizable phase is dispersed, and the result is a delay in the settlement of physical properties [ 1 , 2 , 3 , 4 , 5 , 6 ]. For MRSs, this delay depends on the quantity of the magnetizable phase, the viscosity of the liquid matrix, and the additives used [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ].…”

“…The chain formation when applying a magnetic field and its unraveling when the magnetic field is cancelled depend on the viscoelastic properties of the matrix where the magnetizable phase is dispersed, and the result is a delay in the settlement of physical properties [ 1 , 2 , 3 , 4 , 5 , 6 ]. For MRSs, this delay depends on the quantity of the magnetizable phase, the viscosity of the liquid matrix, and the additives used [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. For MREs, the delay in stabilization of the response function to magnetic excitation depends on the type of silicone rubber and the polymerization speed of the mixture in the presence or absence of the external magnetic field [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ].…”