Fabrication and characterization of ceramic-iron joint coating for electrical insulation

For the realization of liquid metal blanket systems, fabrication of a ceramic-metal multi-layer coating has been proposed to obtain both electrical insulation for the mitigation of magneto-hydrodynamic pressure drop and compatibility with liquid metals. The corrosion protection layer using a metal foil needs to be joined to the ceramic coating to ensure integrity in the flowing environment. Besides, the ceramic coating should be as thin as possible in terms of thermal conduction. In this study, we fabricated ceramic-iron joint coatings using iron foils and thin ceramic coatings by hot pressing. Three kinds of the ceramic coating with different crystallization states were used for joining to compare adhesion to the ceramic coating. The coating before and after joining fulfilled the requirements for electric insulation. The joint coating showed a sufficient adhesion strength to withstand the stress by liquid metal flow due to formation of an iron oxide layer between the iron foil and the ceramic coating. Although the thermal conductivity of the joint coating slightly decreased due to the heat resistance of the interface between the iron foil and the ceramic coating, the joint coating is a promising functional coating for liquid metal blanket systems.