Study On Dispersion Behavior Of Biphasic Particles In Magnetorheological Fluid By Electromagnetism

Magnetorheological finishing (MRF) is a deterministic ultra-precision method for producing complex optics. The magnetorheological finishing fluid (MRFF) is one of the key technologies of MRF and it affects directly the surface quality of optics. Because of the design theory and characterization techniques about characterizing agglomeration-dispersion behaviors of the binary particles in MRFF are not comprehensive, which directly restricts the effective use of MRFF. In this thesis, a multi-scale characteration method is established based on the interactions between particles, which offer theoretical support and characterization methods to design and characterize MRFF.The major interactions between the particles, i.e. van der Waals attraction, electrical double layer (EDL) and steric repulsion were analyzed, repectively. Based on the extended DLVO theory, a physical model of the interaction between the biphasic particles was developed. The EDL interaction has been identified as the most important factor and the surface potential ratio between two dissimilar particles with like charge plays an important role in controlling the change of EDL interaction. It was found that at higher potential ratio ratios, the EDL interaction becomes attractive when the surface separation falls within a certain range. The difference in surface potentials between the biphasic particles has been found to be critical for determining the state of dispersion or heterocoagulation in concentrated MRFF systems.The behavior of MRFF dispersion of particles was investigated. First, it was found that for single-phase polishing powder particle suspension can be characterized by a comprehensive approach Zeta potential, rheological properties and particle size distribution, which was the core of the analysis to analyze Zeta potential; Secondly, electroacoustic theory and measurement of the ESA offers an alternative method for determining the electrokinetic properties of particles in suspensions. By improving the ESA method can be characterized well the state of biphasic particles dispersed.Finally, the influence of magnetic field for behavior of MRFF was also analyzed. Micro level, it was found that only when the actual contact radius of heterocoagulation at the interface is less than the critical radius, the impact force caused by the magnetic field at the interface makes it possible to separate the heterocoagulation. Macro level, it is found that although heterocoagulation has some impact on overall rheological performance of MRFF but under the magnetic field this impact is trival.