The Research Of Aqueous Magnetorheological Fluid's Stability

A magnetorheological material comprising an aqueous carrier fluid, magnetic-responsive particles having average diameters of 5.mu.m. obtain the widespreadattention on magnetorheological polishing because its unique merit. The fluids typicallyinclude ferromagnetic or paramagnetic particles dispersed in a carrier fluid. Theparticles become organized into chains of particles within the fluids, the particle chainsincrease the apparent viscosity of the fluid. The particles return to an unorganized statewhen the magnetic field is removed, which lowers the viscosity of the fluid. Thesemixtures tend to reunite and settle as a function of time with the settling rate generallyincreasing as the temperature increases. The reason why the paritiles tend to reunite isthe specific surface area is large of the magnetic-responsive particles; one of the reasonswhy the particles tend to settle is the large difference in density between the water andthe metal magnetorheological activity of the material due to non-uniform particledistribution. It requires a relatively high shear force to re-suspend the particles afterreunited and settled. This general character problem need urgently. But the systemicresearch in this aspect are infrequent in internal. This expectation of present paper is tosolve the contradiction of disperser stability by the time, settling stability with theviscosity of system, by adding the surface active agent (dispersing agent), thixotropicagent and the nano particles et al.This article bases in the aqueous magnetorheological fluid's basic research. Thefirst, research function of the surface active agent (dispersing agent) to the system'sstability after analysised the disperse mechanism of the aqueous magnetorheologicalfluid. In the research, surveyed the electrophoretic mobility and the Zeta electricpotential of the suspended phase pellet to analyzed the electric charge of adsorbingsurface and the electrostatic repulsion between pellets. The dispersible stability ofsystem is indirect checked by studying the evolution with time of the normalized opticalabsorbance of dilute suspensions for different compositions of the aqueous dispersionmedia. Take the electric double layer theory as the foundation, theoretically analyzed the surface active agent (dispersing agent) can be increase the surface electric potentialof pellets in the aqueous magnetorheological fluid, At the same time, the stericrepulsion increase between the pellets, the hindrance of reunite increase. Theexperiment indicated the polyacrylic acid could form the good adsorption in thecarbonyl powdered iron surface, Obviously enhanced the pellet surface the electricpotential strength, thus enhanced the dispersible stability of aqueous magneto-rheological fluid.The second, studied the mechanism of the bentonite's anti-settling stable action inaqueous magnetorheological fluid, and has conducted the research to the influence ofeach of factor to the bentonite's. The research indicated the bentonite in the aqueousmagnetorheological fluid is extremely sensitive to the environment, the surface activeagent, the chemical compound, the pH value all can through the change montmorillonitepellet superficial electric properties, thus destroys the three-dimensional networkstructures which they form and affect to its thixotropic. The experiment indicated thatthe bentonite can effective enhance the aqueous magnetorheological fluid's anti-settlingability.The third, studied the approach of preparation nanometer Fe₃O₄ pellet in chemicalmethod. Nanometer Fe₃O₄ have many unique characteristics, it can enhance theanti-reunite ability, the anti-settling ability and the mechanics capability of the aqueousmagnetorheological fluids. The present paper summarized the predecessor studies,determined through chemistry co-precipitation method preparation nanometer Fe₃O₄powder is feasible, and checked the nanometer pellet's physical property and chemicalproperty.Finally in the experimental foundation former, prepared the magnetorheologicalfluid with adding the surface active agent, the thixotropic agent, the nano particles. Andthe disperser ability, the anti-settling ability, mechanics performance of the sample hasinvestigated. The result indicated, prepares the aqueous magnetorheological fluid in thisway can obtain the good dispersible ability performance, the anti-sealing performance,The fluids exhibit a yields tress of 50kPa under am agnetic field of 5000Gs.