Magnetorheology of dimorphic magnetorheological fluids based on nanofibers

Abstract

We report a systematic experimental investigation on the use of nanofibers to enhance the magnetorheological (MR) effect in conventional (microsphere-based) MR fluids formulated in polyalphaolefin oil/1-octanol. Two kinds of nanofibers are employed that have very similar morphology but very different magnetic properties. On the one hand we use non-magnetic goethite nanofibers. On the other hand we employ magnetic chromium dioxide nanofibers. For appropriate concentrations the on-state relative yield stress increases up to 80% when incorporating the nanofibers in the formulation. A similar yield stress enhancement is found for both nanofibers investigated (magnetic and non-magnetic) suggesting that the main factor behind this MR enhancement is the particle shape anisotropy. The relative yield stresses obtained by partial substitution of carbonyl iron particles with nanofibers are significantly larger than those measured in previous works on MR fluids formulated by partial substitution with non-magnetic micronsized spherical particles. We also demonstrate that these dimorphic MR fluids also exhibit remarkably larger long-term sedimentation stability while keeping the same penetration and redispersibility characteristics.

Iron–sepiolite magnetorheological fluids with improved performances

“…This work is focused on the characterization and magnetorheological study of the MRF [13] and Bombard et al [14] because the sepiolite fibers seem not to be present in the gaps between iron particles in the aggregates.…”

“…The static yield stress is governed by static gap-spanning particles structures. Thus, the enhancement of the static yield stress increment is unlikely to be attributed to strengthening of the iron particle structures by incorporation of clay particles, as suggested by Lopez-Lopez et al[13] or by an enhanced solid friction between iron particles and sepiolite rods, as suggested by Bombard et al[14] because (a) sepiolite particles introduced in the gaps between iron particles would increase these gaps and decrease the magnetic forces between iron particles; (b) the presence of sepiolite on the surface of iron particles within the aggregates would imply a considerable change in the MRF magnetic susceptibility (as explained in detail in Sec. III-A) that is not the case in our experiments [Fig.…”

“…% iron particles in kerosene to decrease the sedimentation [13]. As non-magnetic (or rather weakly antiferromagnetic) goethite fiber-like particles to improve the MR effect varying the total concentration of both species up to 45vol% [14]. This composition allowed obtaining a better sedimentation stability thanks to a viscoplastic behavior of the fiber network and a yield stress enhancement by a factor of two-to-three as compared to the suspensions without addition of fibers.…”

Two-Dimensional rGO-MoS2 Hybrid Additives for High-Performance Magnetorheological Fluid

“…Bombard et al . 5 also recently reported the effect of using non-magnetic goethite nano-fiber particles as additives in the MRF. In addition, they noted that the shape of the particles plays a major role in the enhancement of the performance as compared to its magnetic properties.…”

“…Moreover, the size of the additives in micro and nano levels has shown a remarkable effect on the properties as well. Submicron iron micro wires 10 and nano-sized non-magnetic 5 and superparamagnetic 11 additives have displayed significant improvements. In short, the literature review reveals that depending on the nature of a particular additive, there might be a trade-off between the MRF properties; thus, a thorough investigation is still required in order to comprehensively understand the effects of non-magnetic and magnetic additives on the MRF properties.…”