Simultaneous effect of magnetic nanoparticles additive and noble metal coating on carbonyl iron-based magnetorheological fluid

Abstract

Magnetorheological (MR) fluid is an intelligent fluid that is strongly influenced by an external magnetic field. These fluids are prepared by introducing micron-sized magnetic particles such as carbonyl iron into nonaqueous fluids. The main challenge in those systems containing these fluids such as shock absorbents and abrasive fluids is the instability and sedimentation of magnetic particles in the base fluid. The main aim of the study is to provide stable carbonyl iron (CI)-based magnetorheological fluids with desired efficiency and as much yield stress. In this context, we synthesized Ni-Zn ferrite nanoparticles as additives via high-energy ball milling. This is followed by coating the pristine CI particles with silver via a green-assisted coprecipitation method, using honey as a reducing agent to convert AgNO3 to Ag nanoparticles. The as-produced samples were characterized by the means of XRD, FTIR, FESEM, and TEM. Four types of prepared MR fluids were a CI based, ferrite nanoparticles additive-CI-based MR, Ag-coated CI-based MR, and a combination of the second and third states in the presence of poly alpha olefin oil as the carrier liquid and oleic acid as surfactant agent. The results revealed that the density of the Ag-coated CI was reduced to almost half the density of pristine CI particles. Furthermore, the results of the rheology test on CI-based and CI/Ni Zn ferrite MRs showed an increase in yield stress from 38,000 Pa to 46,000 Pa due to the presence of nickel-zinc ferrite particles. However, magnetorheological fluids based on carbonyl iron particles coated with silver nanoparticles showed a decrease in yield stress (29,700 Pa) because the magnetic property of CI particles has decreased by coating. Magnetorheological fluid based on carbonyl iron particles coated with silver nanoparticles and additive of nickel-zinc ferrite nanoparticles had yield stress similar to magnetorheological fluid based on iron carbonyl particles (38,000 Pa) but with more stability from 55% to 70%.