High Temperature Electrochemical Synthesis Of Functional Materials In Molten Salts

Abstract:

Extreme conditions of articles exploitation cause utilization of expensive refractory metals and alloys ensuring their adequate performance. The problem can be approached by depositing coatings on the surface of units and mechanisms, i.e. creating composite materials. In this case, the substrate material provides the strength and electric characteristics while the coatings realize the necessary surface properties. Nowadays coatings are mostly produced by CVD, PVD methods, plasma and detonation spraying. Electrochemical synthesis from molten salts offers considerable advantages over other methods. For example, electrochemical methods such as pulse plating and reversed plating provide a unique means of controlling the structure and phase composition, the thickness of the coatings, the grain size (down to the nano scale), the porosity, the smoothness, and the texture of the layer. Other advantages are: (i) a relatively low synthesis temperature (700-850°С); (ii) the parameters of electrochemical deposition can be easily adapted in scaling-up synthesis; (iii) the method can be applied to all kinds of substrates with a complicated geometry for obtaining of uniform coatings with respect to thickness, grain size and composition of the layer; (iv) high purity of resulting coatings even with low-grade initial reactants; (v) the production costs are much lower comparing to other methods. This study presents our findings in the area resulting in the production of functional materials of different application:1. Heat-resistant material: from hafnium and niobium-hafnium alloy on borosiliconizing graphite with the temperature of exploitation up to 1700-2000°С.2. Composite material MoSi2-MoB4 for protection of molybdenum from oxidation in an air-water mixture at temperature 500-700°С.3. A new generation of highly active and stable catalysts based on nanostructured Mo2C coatings for the water-gas shift reaction.4. Material for hydrogen storage on the base of V-Ti alloys.5. Glass-ceramic shells for hot isostatic pressing with titanium and niobium barrier coatings.

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