Corrosion-Resistance for ZTA-Cr_2O_3 Sintered Bodies in Molten Fluoride Salts

[出版社版]rights: 社団法人日本セラミックス協会 rights: 本文データは学協会の許諾に基づきCiNiiから複製したものである relation: IsVersionOf: http://ci.nii.ac.jp/naid/110002313730/The stability of tetragonal ZrO_2 in ZTA-Cr_2O_3 sintered bodies fabricated by an impregnation method was investigated in NaF, KF, Na_2SiF_6 and K_2SiF_6 at 900°and 1000℃. ZTA-Cr_2O_3 having relative density above 99%, flexural strength of about 450 MPa and hardness of about 1600 kg/mm^2 at R. T. was used for the corrosion test. ZTA-Cr_2O_3 exhibited higher corrosion-resistance in carbonate and sulfate salts than in fluoride salts. The corrosion-resistance of ZTA-Cr_2O_3 in molten fluoride salts increased with an increase in the addition of ZrO_2 to Al_2O_3. ZTA-Cr_2O_3 formed a reaction layer (on the sintered body) in molten fluoride salts. The reaction layer formed in KF consisted of K_3AlF_6 and Al_2O_3-Cr_2O_3 solid solution, and protected the t-ZrO_2 phase beneath the reaction layer. The stability of t-ZrO_2 phase was dependent on the thickness of the reaction layer. Three mol% Y_2O_3-ZTA-Cr_2O_3 was superior to the other ZTA with respect to the corrosion-resistance in molten fluoride salts