The aim of this work was to prepare a dimorphic magnetorheological (MR) fluid for which sedimentation stability, oxidation and chemical stability are enhanced in comparison with common MR fluids, while at the same time preserving the MR effect at its fullest practical level. A dimorphic MR fluid exhibiting these properties was prepared in two steps. The first step involved the partial substitution of carbonyl iron (CI) spherical microparticles with Fe rod-like particles synthesized via a surfactant-controlled solvothermal method. This improved sedimentation stability in comparison with the application of CI particles alone. In the second step both spherical CI and Fe rod-like particles were coated with a polysiloxane layer through the hydrolysis-condensation polymerization of tetraethylorthosilicate. This ensured better oxidation and chemical stability balance with an acceptable decrease in the MR effect. This effect is still markedly better than that based on Fe_3O_4 particles.
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