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Optical velocity measurements of electrolytic boundary layer flows influenced by magnetic fields

König, J.; Neumann, M.; Mühlenhoff, S.; Tschulik, K.; Albrecht, T.; Eckert, K.; Uhlemann, M.; Weier, T.; Büttner, L.; Czarske, J.

Magnetic fields are applied to electrically conducting fluids, in order to influence electrochemical processes by leveraging the magnetohydrodynamic effect. Various phenomena, e.g. on electrodeposited metal layers, were observed, which can be attributed to forced convections. To provide information about acting forces, the laser Doppler velocity profile sensor was applied to measure the transition layer of a Lorentz force influenced backward-facing step and the velocity boundary layer during copper-deposition. With this sensor, the electrolyte convection is revealed within < 500 μm of an electrode with a spatial resolution down to 15 μm. The interaction of buoyant, Lorentz and magnetic field gradient force is studied by measuring the velocities down to 10 μm in front of the cathode. It is shown that complex electrolyte convection is induced inside the concentration boundary layer, which varies not only in time but also in its structure, depending on the present forces and their temporal influence. At inhomogeneous magnetic field configurations, the magnetic field gradient force dominates the velocity boundary layer at steady state and transports electrolyte toward regions of high magnetic gradients, where maximum deposit thicknesses are found. In this way, the measurements confirm the predicted influence of the magnetic field gradient force on the structuring of copper-deposits.

Keywords: Laser Doppler Velocity Profile Sensor; Particle Image Velocimetry; backward facing step; copper deposition

Permalink: https://www.hzdr.de/publications/Publ-18091
Publ.-Id: 18091