Trial Fabrication and Properties of Ceramic Coatings for Fusion Reactor

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In ceramic coating for fusion reactor liquid blankets, there are some important factors such as mass-production, compatibility with liquid metal and function as a tritium permeation barrier and an insulating barrier. In this study, we selected some candidate materials for ceramic coating, produced coatings experimentally from those materials, and investigated their characteristics so that we might establish the fabrication technique of ceramic coating for fusion reactor liquid blankets. The results are summarized as follows.(1) Material selection for ceramic coating : For Li17-Pb83, Al_2O_3, MgO, Y_2O_3 were nominated for candidate material based on thermochemical analysis and the corrosion test using bulk materials, and Al_2O_3 and Y_2O_3 were selected as the primary candidate materials because their electric insulation property was superior among them. For metallic lithium, on the other hand, no corrosion resistant oxides were found except Y_2O_3, and AlN was selected as a candidate … More material after nitrides were also examined.(2) Property change of ceramic coating materials in the fusion reactor environment : We measured electrical properties of the materials that were thus selected after corrosion test with the liquid metals. Y_2O_3 was reduced by lithium to become electrically conductive due to the formation of a nonstoichiometric compound. It was also concluded that the electrical resistivity of coatings may deteriorate due to radiation induced conduction under irradiation at high temperature.(3) Trial fabrication of ceramic coatings and assessment about their utility : Based on the results mentioned above, we prepared ceramic coatings of Al_2O_3, Y_2O_3, AIN by some methods and measured their properties. About the plasma spraying method, generation rate was enough high, but how you can remove inside pores is an important problem. About the dip coating method, how you can effectively nitrify the specimens is an important problem, in particular in case of AlN coating. In the sputtering method, it was concluded that the treatment of substrate is necessary.Finally, it was concluded that the most desirable method for coating at present is the dip coating method of Al_2O_3 for Li17-Pb83. For metallic lithium, on the other hand, it is AlN layer formation by sputtering or the CVD method Al layer formed by the dip coating method or sputtering. Less