Preparation and rheological properties of low-temperature hydraulic oil-based magnetic nanofluids
It is worth studying how to strike a balance between the magnetorheological effect and sedimentation stability in magnetic nanofluids,and the use of larger nanoparticles has been identified as a promising solution.Fe3O4 magnetic particles with a size of approximately 25 nm were synthesized using a controlled chemical co-precipitation method,and their phase composition and magnetic properties were characterized.Magnetic nanofluids were prepared using myristic acid as surfactant and RP4350 aviation hydraulic oil as dispersed phase,which exhibited prolonged stability under strong magnetic fields,with applicable temperatures ranging from—35 ℃ to 95 ℃.The variations in magnetorheological properties with magnetic field strength and temperature were investigated.The results reveal that under the influence of low temperatures and strong magnetic fields,the magnetic nanofluids exhibited significantly higher yield stress,reaching a maximum of 0.16 kPa.Even after yielding,the samples displayed stronger magnetoviscous effect.Dynamic rheological characteristics of magnetic nanofluids were examined using amplitude sweep measurements.The increase in magnetic field strength and the decrease in temperature can effectively enhance the shear resistance of the nanomagnetic fluid,which leads to the elevation of the storage modulus.Furthermore,the linear viscoelastic(LVE)region and the crossover point of the storage modulus and loss modulus also shift towards higher strain amplitudes.These findings contribute to the research on magnetic nanofluids prepared with larger particles and provide guidance for their applications over a wider temperature range.
magnetic nanofluidssedimentation stabilitymagnetorheological effectviscoelasticitytemperature
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