Role of organic coating on carbonyl iron suspended particles in magnetorheological fluids

Abstract

Carbonyl iron ͑CI͒ has been widely used as a suspended particle in magnetorheological ͑MR͒ fluids. However, pristine CI-based MR fluids have several drawbacks, including severe sedimentation of the CI particles due to the large density difference with the carrier liquid, difficulties in redispersion after caking, abrasion of device surfaces during long-term operation, and rust of iron by oxidation. To overcome these shortcomings, we coated the CI particles with a poly͑vinyl butyral͒ ͑PVB͒ shell. CI and CI-PVB particles were suspended in mineral oil and their MR characteristics were examined via a rotational rheometer in a parallel plate geometry equipped with a magnetic field supplier. Yield stress and flow response ͑shear stress and shear viscosity͒ were investigated at magnetic field strengths ranging from 0 to 343 kA/ m. Although the MR properties, such as yield stress and shear viscosity of CI-PVB based MR fluids, changed slightly compared with those of the pristine CI based MR fluid, the dispersion qualities ͑e.g., sedimentation stability͒ were noticeably improved.

Fabrication of polyaniline coated iron oxide hybrid particles and their dual stimuli-response under electric and magnetic fields

“…At a zero magnetic field, the suspension behaved like a general fluid, which shows linearity between the shear stress and shear rate. On the other hand, it acted as a Bingham fluid [28] under an external magnetic field with a yield stress due to the formed particle cluster or chains by polarization forces [29]. The yield stresses increased from 30 to 437 Pa under magnetic field strengths from 86 to 342 kA/m.…”

Synthesis and corrosion study of zirconia-coated carbonyl iron particles

“…Carbonyl iron (CI) particles are key active ingredient in many of the magnetorheological (MR) fluids which have a range of applications [1]. Surface functionalization of CI particles becomes an increasingly important research area that addresses corrosion, sedimentation, and other technical challenges facing the improvement of the performance of existing MR fluids.…”

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“…This versatile characteristic makes MRP show a much higher magnetorheological effect than magnetorheological elastomer. 1 Except for novel performance in rheology, MRP can also overcome the headache particle sedimentation problem 5 of magnetorheological fluid.…”