The Dependence of the Rotational Effect in Magnetic Fluids on the Parameters of Magnetic Field

Purpose. The dynamics of the rotation of liquid masses, the study of the equilibrium shapes of rotating liquids and  their nonequilibrium states have traditionally attracted the researchers’ attention. The key problem of this work is  the experimental study of the rotational effect in magnetic fluids. A macroscopic capsule filled with magnetic fluid acquires a rotational moment because of spatial orientation of magnetite nanoparticles under the action of an external rotating magnetic field. The magnitude of this effect depends on many parameters. We discuss how it depends on the frequency and amplitude of the external rotating magnetic field, as well as on the concentration and viscosity of the magnetic fluid.

Methods. Our research object is magnetic fluids APG 942 and APG 2135, produced at the Ferrotec Corporation (Japan), and their derivants obtained by mixing with dodecane and durazin. Magnetic nanoparticles are from magnetite, dispersion medium is synthetic hydrocarbon oil.

The experimental data were obtained using a torsion pendulum in a rotating magnetic field. A spherical capsule was filled with the samples and suspended on a thin elastic thread. A webcam placed under the capsule registered the angle of its rotation relative to the equilibrium position. Taking into account the elastic coefficient of the thread, we plotted the dependences of the rotational moment of the sample on the parameters of the external rotating magnetic field.

Results. The result of our experimental research is the dependences of the rotational effect in a magnetic fluid on the amplitude and frequency of the external magnetic field. The influence of the concentration, magnetic characteristics and viscosity of magnetic fluid samples on the rotational effect is also discussed. We suggest the aggregation model of the rotational effect, which describes the experimental data from the point of view of the formation and destruction of aggregates and clusters of magnetic nanoparticles.

Conclusion. The research results allow analyzing the structure of magnetic dispersed systems. It can be used in the development of devices based on the action of alternating magnetic fields on a magnetic fluid.

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