Rospotniuk V. Magnetohydrodynamic effects at magnetoelectrolysis in heterogeneous magnetic fields in the presence of clusters in electrolytes

The problem of the influence of an inhomogeneous magnetic field on electrochemical reactions occurring on the surface of metal electrodes in electrolytes is solved in this thesis. Also the quantitative explanations of the effects of anisotropic etching and deposition, magnetohydrodynamic mixing of solutions, liquid-liquid phase separation, etc. are given in the work. The concept of magnions as nano- and micro-size effectively paramagnetic components of an electrolyte, which have a magnetic moment of 5-6 orders of magnitude larger than the magnetic moment of a single paramagnetic ion is introduced for the modelling of these effects. It was established that the magnetic capturing of magnions is the physical reason of anisotropy of the observed effects. The theoretical model of MHD stirring is based on a system of equations of magnetic hydrodynamics of a weakly conducting fluid and convective diffusion which take into account the presence of magnions in the solution. These equations are supplemented by the boundary conditions that involve the electromotive force of the concentration circle and the supply of magnions by electrochemical reactions under the action of gradient magnetic forces. The equation of the hydrostatic equilibrium of magnetic, osmotic, gravitational, centrifugal and Laplace pressures is used to simulate the phase separation of the electrolyte. By comparing theoretical results with experimental data, the characteristic size of magnions, their magnetic moment and charge are estimated. Also, the magnetophoretic potential associated with the motion of magnions under the action of gradient magnetic force was calculated on the basis of the equations of thermodynamics of nonequilibrium systems and Onzager's relations. The developed approaches allow controlling the shape and size of the metal sediments and etching figures, as well as the rate of electrochemical reactions occurring at different regions of the electrode surface. They are used in the modelling of electrochemical sensors, microfluidic devices and the simulation of the effect of biogenic magnetic nanoparticles on transport processes and biochemical reactions in living organism cells.