Magnetorheology of Carbonyl Iron Dispersions in 1-Alkyl-3-methylimidazolium Ionic Liquids

Abstract

In this work, a range of ionic liquids (IL), all based in 1-alkyl-3-methylimidazolium, [EMIM] + and [BMIM] + cations, with different anions: [NTf 2 ] -, [CF 3 SO 3 ] -, [SCN] -, [BF 4 ] -, [PF 6 ] -and [CH 3 COO] -were used as carrier fluids to prepare magnetorheological (MR) fluids with 30 vol% of carbonyl iron powder (CIP), grade EW (BASF SE), without additives. IL-MR fluids were characterized in the presence of magnetic fields with conventional steady shear stress ramps, constant shear rate magnetosweeps and strain amplitude oscillatory shear tests. In the absence of magnetic fields, samples were subjected to temperature sweep (from +80 to -20°C), settling and redispersibility tests. We conclude that, under large enough magnetic field strengths, above 10 kA/m, there is not a significant effect of the IL employed, in terms of MR effect or MR performance, both in steady shear as well as oscillatory shear. On the other hand, for long shelf-life, without applied magnetic field at rest, [EMIM] + [CF 3 SO 3 ] -, [BMIM] + [SCN] -and [BMIM] + [CH 3 COO] -are not good candidates as carrier fluids for MR fluids, since they are very difficult to redisperse because of existing specific chemical interactions with the particle surface. In terms of settling stability, [BMIM + ][PF 6 ] -and [BMIM] + [CH 3 COO] -presented slower settling rates, because of their higher viscosities, however the sedimentation curves collapse when normalized by the viscosity of the IL. Overall, the presence of fluorinated anions, such as [NTf 2 ] -, [BF 4 ] -and [PF 6 ] -facilitates redispersibility as demonstrated by penetration tests.

The Role of Volume Fraction and Additives on the Rheology of Suspensions of Micron Sized Iron Particles

“…/H The second point we need to take into account is that, in the plate-plate configuration, the yield stress provided by the software is overestimated by a factor of 4/3 Laun et al, 2010). The data collected in different publications (Kordonski and Golini, 1999;Chin et al, 2001;Lim et al, 2004;Jang et al, 2005;Cheng et al, 2009;Ierardi and Bombard, 2009;Laun et al, 2010;Kim et al, 2012;Bombard et al, 2015;Esmaeilnezhad et al, 2017;Dong et al, 2018;Plachy et al, 2018) are reported in Table S1 and plotted in Figure 1B (blue diamonds). There is a considerable scatter of the data, but it appears clearly that the affine model with the calculation of forces through FEM (red curve), provides the best prediction compared to both Equation (6) and Equation (7).…”

Improved Magnetorheological Properties by Using Ionic Liquid as Carrier Liquid of Magnetorheological Fluids

“…The traditional method of using surfactants to change the interface will complicate the composition of the rheological fluid, and cannot distinguish its influencing factors and effects well. Although ionic liquids have been used as carrier fluids for MRF (Guerrero-Sanchez et al, 2007;Gómez-Ramírez et al, 2011;Jönkkäri et al, 2014;Bombard et al, 2015), few people have noticed that although its viscosity is similar to that of silicone oil, its surface tension is higher than that of silicone oil. This will bring different interface effects.…”

Investigation into a Conductive Composite Matrix Based on Magnetically Sensitive Flexible Sponges

“…Usually, a magnetic composite matrix is regarded as a two-phase conductive material, in which the magnetic particles play a considerable role in contributing to the conductivity. Over the past decades, numerous metals or alloys have been successfully developed. , Among them, soft micron carbonyl iron (CI) particles are highly desirable because of their high saturation magnetization and common availability. , On the application of a magnetic field, the micron CI particles distributed in the nonmagnetic matrix become polarized and gather in chain or cluster structures owing to dipole interactions. To meet the requirements of dispersion ability and MR properties, various modification methods have been successively performed including surface coatings, magnetic nanoparticles, and additive fillers. − In our previous study, bidisperse magnetic microspheres containing micron CI particles and Fe 3 O 4 nanoparticles wrapped in gelatin (GE) and multiwalled carbon nanotubes (MWCNTs) were prepared via a sol–gel method, which showed enhanced MR properties while maintaining the original dispersion stability of CI particles.…”

“…9,10 Among them, soft micron carbonyl iron (CI) particles are highly desirable because of their high saturation magnetization and common availability. 11,12 On the application of a magnetic field, the micron CI particles distributed in the nonmagnetic matrix become polarized and gather in chain or cluster structures owing to dipole interactions. To meet the requirements of dispersion ability and MR properties, various modification methods have been successively performed including surface coatings, magnetic nanoparticles, and additive fillers.…”