Aspects Concerning the Fabrication of Magnetorheological Fluids Containing High Magnetization FeCo Nanoparticles

M Mounir Bou-Ali,Maite Insausti,Izaskun Gil De Muro,Ainara Gómez,Virginia Vadillo,Joanes Berasategi,Jon Gutiérrez

doi:10.3390/fluids6030132

Abstract

Recently, our collaborative work in the fabrication of a magnetorheological fluid (MRF) containing high magnetization FeCo nanoparticles (NPs, fabricated in our laboratories using the chemical reduction technique; MS = 212 Am2/kg) as magnetic fillers have resulted in a new MRF with superior performance up to 616.7 kA/m. The MRF had a yield stress value of 2729 Pa and good reversibility after a demagnetization process. This value competes with the best ones reported in the most recent literature. Nevertheless, the fabrication process of this type of fluid is not an easy task since there is a strong trend to the aggregation of the FeCo NPs due to the strong magnetic dipolar interaction among them. Thus, now we present the analysis of some aspects concerning the fabrication process of our FeCo NPs containing MRF, mainly the type of surfactant used to cover those NPs (oleic acid or aluminium stearate) and its concentration, and the procedure followed (mechanical and/or ultrasound stirring) to achieve a good dispersion of those magnetic fillers within the fluid.

Highlights

The magnetorheological fluid is composed of magnetic particles dispersed within a liquid carrier
Under no applied magnetic field, no magnetic interaction appears among the magnetic fillers and the observed MR behaviour is Newtonian-type, corresponding to a suspension of non-interacting particles
In all cases, we observed that under application of an external magnetic field, our fabricated MR fluids showed a non-Newtonian [16,19]

Summary

Introduction

Magnetorheological (MR) fluids are widely known as “intelligent” fluids due to their ability to exhibit reversible rheological behaviour that can be controlled by the application of an external magnetic field. That is, they are a new class of materials whose performance can be adapted to variable working conditions [1,2,3]. The fluid suffers a very fast transition from a liquid to an almost solid-state, and finite stress (the so-called yield stress) is needed to break the chain-like structures constructed by the magnetic fillers

Methods

Results

Conclusion