Structural and rheological study of magnetic fluids using molecular dynamics

Taixiang Liu¹ - Rui Gu¹ - Xinglong Gong¹ - Shouhu Xuan¹ - Hengan Wu¹ - Zhong Zhang²

¹ CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, 230027, China
² National Center for Nanoscience and Technology, Beijing 100080, China

Abstract
In this study, molecular dynamics simulations based on a magnetic dipole theory were developed to study microstructural evolution, rheological properties and potential energies of magnetic fluids (MF) under steady shear or compression. In general, the magnetic interaction dipole forces drive the nanoparticles to form firstly a chain-like and then a column-like structure under an externally applied magnetic field. The potential energies are time-dependent and the static yield stresses increase with the growth of magnetic field strength. Under the steady shear, the one-dimensional chain or column structures would transform into lamellar patterns. The shear stresses were theoretically predicted and they agreed well with experimental results. Under compression, when magnetic fluids were compressed along the magnetic field, simulation results show that the materials exhibit enhanced yield stresses and the work of compressive loading is absorbed mostly by the repulsive potential energy. Figs 11, Refs 14.