Magnetorheological properties of a kerosene-based ferrofluid with magnetite particles hydrophobized in the absence of the dispersion medium

A kerosene-based ferrofluid sample was prepared by a method in which the magnetite nanoparticles were stabilized by hydrophobization in the absence of the dispersion medium. This method ensures formation of aggregates that in the presence of a static magnetic field transform into large drop-like particle agglomerations, which disappear when the field vanishes. The Brownian relaxation measurements and the magneto-optical microscopy image demonstrate that the obtained sample exhibits magnetic field induced particle agglomerations. The magnetorheological investigations (i.e. the viscosity curves at different values of the static magnetic field, H, between (0–520) kA/m, the magnetoviscous effect, the temperature dependence of viscosity, the apparent viscosity dependence on Mason number and the thixotropic analysis) demonstrate that the ferrofluids with drop-like particle aggregation induced by the magnetic field exhibit significant magnetorheological effect, recommending them in electro-mechanical devices that operates at micrometric or sub-micrometric scale, where magnetorheological fluids cannot be used. •A kerosene-based ferrofluid with magnetite particles was prepared.•Particles are stabilized by hydrophobization in the absence of dispersion medium.•Magneto-optical measurements show aggregates occurrence in magnetic field.•In the absence of the magnetic field, the ferrofluid has quasi-newtonian behavior.•In the presence of the magnetic field, pseudoplastic behaviour is observed.