Research of Magnetic Fluid’s Magnetization Mechanism by Deformation of Droplet in Magnetic Field

Abstract

An important feature of magnetic fluids is the topological instability of their volumes which have a free surface in the magnetic fields (the phenomenon of loss of their integrity under certain conditions). Such drop splitting is of scientific interest, as well as of practical interest. Understanding the mechanism of this phenomenon will allow eliminating or controlling these effects, which is important for many sensitive devices. The authors' investigations were aimed at solving the problem of describing the splitting of a droplet of magnetic fluid, which lie on a horizontal solid partially wettable rubber substrate, in a magnetic field of a permanent magnet and an experimental determination of the type of dependence of the change in the height of a magnetic fluid's droplet in magnetic field.

In Ukraine, the research of magnetic fluids is carried out by a number of scientific organizations, such as Institute for Nuclear Research, V. I. Vernadsky Institute of General and Inorganic Chemistry, Taras Shevchenko National University of Kyiv etc.

The main reason for the drop extension in the magnetic field is the reorientation of the magnetic domains within it. The magnetization of the liquid begins to increase. This makes a pressure along the axes in the drop, which causes the droplet to stretch and then split. 

The experiment was carried out with three magnetic fluids with different components. The process of splitting under the experimental conditions is observed only for one which composition was unknown. It took an X-ray and carried out a qualitative phase analysis. Particles of the most probable size from 5,8 ± 1,0 nm to 8,7 ± 1,0 nm were obtained.

An experiment was performed to determine the dependence of the geometric parameters of the droplet of magnetic fluid in the magnetic field. The magnitude of the field and the height of the drop were measured. The experiment was carried out until the maximum value of the installation field was reached. The obtained dependence can characterize the hysteresis-free magnetization curve of the magnetic fluid. Approximation was carried out on the basis of arctangent functions.

The conditions for the rupture of a magnetic fluid droplet on a solid rubber partially non-wettable substrate in a magnetic field are investigated. Several magnetic fluids of different composition are considered. An optimal physico-mathematical model of the process is proposed. Experimental dependences of the discontinuity of a semibounded droplet of magnetic fluids in magnetic field, corresponding to the model taken, are obtained. The analysis is carried out within the framework of this model. In the chosen direction, the authors continue their research.