The Properties of MRFs Based on Carbonyl Iron Particles Modified by Nano-Sized Silica and Phosphate Coating Layer

摘要

Magnetorheological fluids (MRFs) are smart functional materials generally fabricated by magnetic particles and base oil, and the modification of magnetic particles is a common way to improve the performances of MRFs. The main purpose of this work is to investigate the influences on comprehensive performances including magnetorheological property, tribological property and sedimentation of MRFs by specific particle modification. The static shear tests show that MRFs based on modified particles have higher shear stresses without magnetic field, but display lower shear stresses under high shear rates in the presence of magnetic field. However, once the external magnetic field applied, structures formed by bare particles are relatively easier to recover by magnetostatic forces which lead to higher shear stresses. As for dynamic shear tests, modification of particles gives raise to storage modulus especially within the linear viscoelastic range when magnetic field applied, it probably proves that modified particles form stronger structures. The tribological tests reveal that the friction coefficients and wear scar diameters of MRFs based on modified particles display considerable decreases; it is evident that modification of magnetic particles improves the tribological properties of MRFs because of the lubricant effects of coating layers. Moreover, magnetic field can release the friction and wear of MRFs effectively. The sedimentation ratio of MRFs shows MRFs based on modified particles display much better colloidal stability.