Force analysis and distribution evolution of Fe3O4 nanoparticles in magnetic fluids

Abstract

The effective utilization of magnetic nanoparticles in ferromagnetic fluids relies on their distribution and properties, which can be influenced by their arrangement at both micro and macro scales. In this paper, we present a dynamic model to analyze the motion and forces of nanoparticles in magnetic fluids, aiming to describe their distribution evolution under magnetic and flow fields. Finite element simulations using COMSOL software are employed, and a dimensionless ordering coefficient is proposed to quantitatively evaluate the status of nanoparticle distribution. The results indicate that reducing fluid viscosity, increasing magnetic field strength, and increasing magnetic particle radius can facilitate the attainment of an optimal ordered state for nanoparticles in magnetic fluids. However, prolonged exposure to a magnetic field can lead to particle agglomeration, hindering the effective manipulation of nanoparticles. To mitigate rapid agglomeration, we employ an intermittent magnetic field exposure strategy during the curing process of a magnetic slurry consisting of PVDF, DMF, and Fe3O4 nanoparticles. The tests reveal that with increasing magnetic field exposure time, the increase rate of the ordering coefficient initially progresses slowly, then gradually accelerates, and eventually reaches equilibrium. This approach successfully addresses the rapid agglomeration of magnetic particles observed in the simulation results. Consequently, precise control over the nanoparticle radius, magnetic field strength, and carrier fluid viscosity allows for meticulous regulation of the ordered distribution state of magnetic particles. This breakthrough has significant potential in expanding the application and research opportunities of magnetic materials.