Superconducting Niobium Coatings Deposited on Spherical Substrates in Molten Salts

Abstract

Abstract:The interaction of substrates from ceramics, beryllium, and carbopyroceram with the electrolyte for the electrodeposition of niobium coatings was investigated. The corrosion resistance of spherical ceramic and beryllium samples with the protective molybdenum films obtained by magnetron sputtering was studied. The exfoliation of molybdenum film from ceramics and beryllium samples was observed after the experiments due to the interaction of substrates with the melt. It was found that the carbopyroceram did not corrode in the niobium containing melt and this material was chosen as the substrate for the electrodeposition of superconducting niobium coatings. The influence of the oxide ions on the electrochemical behavior of niobium complexes in the NaCl-KCl-NaF-K 2 NbF 7 melt was studied. A special form of the cathode was constructed for the electrodeposition of niobium coatings on spherically shaped substrates. Electrodeposition of the niobium coatings on spheres 10 mm in diameter manufactured from carbopyroceram was carried out at 750 • C with the cathodic current density of 5 × 10 −3 -2 × 10 −2 A·cm −2 and the electrolysis time of 8-12 h. Influence of the cathodic current density on the microstructure of niobium coatings was studied. The roughness, nonsphericity, and superconductive properties of niobium coatings were determined.

Electrolytic superconducting niobium coatings for a cryogyroscope rotor: creation and properties

“…The electrodeposition of niobium coatings on spheres was carried out at a temperature of 1023 К. The cathodic current density during electrolysis varied in the range 5•10 -3 -2•10 -2 A•cm -2 , the rotation speed of the stirrer in all experiments did not change and was chosen equal to 35 rpm [3]. The electrolysis time was 8-12 h.…”

Titanium Oxide Coatings Deposited on MnZn Ferrite by a Molten Salt Reaction

“…On the other hand, a molten salt reaction is a method that uses one or more salts with a low melting point as a reaction medium to form thin films on the surface of materials through a disproportionation reaction [18][19][20]. The molten salt reaction method has several unique characteristics-for instance, there are no special requirements for the surface roughness of the substrate material-and the bonding between the film and the substrate is firm [21].…”

Influence of the Second Coordination Sphere on the Roughness of Niobium and Tantalum Coatings Obtained in Chloride-Fluoride Melts

“…8,9 A promising method for the production of niobium and tantalum coatings is electrodeposition from molten salts. [10][11][12][13][14][15][16][17] In study, 18 on the base of criteria: possibilities of obtaining and controlling the process parameters, and technological and cost indices, the promising of the method for obtaining coatings from molten salts has been confirmed.…”

“…Electrodeposition of niobium and tantalum coatings using molten salts has the following advantages in comparison to other methods 15,16 : electrolysis using pulse and reverse current provides the possibility to easily control the deposit structure, thickness, porosity, degree of roughness, texture of coatings, and grain size (up to nanosized values); electrodeposition parameters determined on laboratory installations can be scaled to large ones using geometric similarity, kinematic similarity, thermal similarity, current/potential similarity 19,20 and adjusted to processes using substrates of complex shapes with control of the thickness, grain size, and composition of coatings;…”