Synthesis and magnetorheological characteristics of ribbon‐like, polypyrrole‐coated carbonyl iron suspensions under oscillatory shear

Abstract

One of the crucial problems of classical magnetorheological (MR) fluids is their high rate of sedimentation. This disadvantage may be substantially eliminated using core-shell particles. The aim of this study is to prepare spherical carbonyl iron (CI) particles coated with conducing polymer polypyrrole (PPy) with ribbon-like morphology. Scanning electron microscopy proved the formation of the ribbon-like layer onto CI particles while Fourier transform infrared spectroscopy confirmed the chemical structure of PPy. The magnetic properties observed via vibrating sample magnetometer showed decreased magnetization saturation of coreshell-structured particles due to the existence of non-magnetic surface layer. MR measurements performed under oscillatory shear flow as a function of the applied magnetic flux density, temperature, and particle concentration showed that core-shell particle-based MR suspension exhibits sufficient MR performance for practical applications. Moreover, the suspension stability is promoted significantly when core-shell particles are used as a dispersed phase.

Magnetorheology of Core–Shell Structured Carbonyl Iron/Polystyrene Foam Microparticles Suspension with Enhanced Stability

“…As shown in Figure 6b, the storage moduli of the three MR fluids exceeded their corresponding loss moduli (G′ > G″), which verified the dominant solid-like elastic properties of the MR fluids arose from the formation of the columnar chain-like structures upon exposure to magnetic field. 19 Both the storage modulus and loss modulus increase with the magnetic field strengths due to enhanced particles interaction. Strong magnetic polarization maintains those chain-like structures at a high shear rate.…”

Magnetorheology of core–shell typed dual-coated carbonyl iron particle fabricated by a sol–gel and self-assembly process

“…In the absence of an external magnetic field, the magnetizable particles are dispersed randomly in the medium and the MR fluid exhibits Newtonian-like fluid behavior depending on the particle concentration. On the other hand, when a magnetic field is applied, the dispersed particles build up chain-like structures in the field direction due to an induced magnetic dipole-dipole interactions [4].…”

Effect of surface treatment on magnetorheological characteristics of core-shell structured soft magnetic carbonyl iron particles

“…Overall, applying a polymer coating to magnetic particles is a common and effective strategy. A variety of polymer-coated CI particles, including CI/polystyrene, CI/polypyrrole, and CI/polyaniline, have been made to decrease the sedimentation rate by reducing the density of CI particles [22][23][24][25].…”