| Summary: | 碩士 === 國立成功大學 === 材料科學及工程學系 === 102 === Since oxide layer composed of Cr2O3 and MnCr2O4 with high resistance formed on surface of interconnect Crofer 22 H at SOFC operating temperature, it is necessary to deposit highly conductive oxide layer to reduce the oxidation rate of substrate. In this study, dense and well adherent coating were applied through air plasma-spraying on Crofer 22 H The result shows that the oxidation of Crofer 22 H at 800℃ was significantly suppressed. The coating materials used were La0.8Sr0.2MnO3(LSM) and Mn1.5Co1.5O4(MCO) due to their high conductivity and good oxidation resistance respectively. Mixtures of these two oxides with molar ratio 7:3, 1:1 and 3:7 were deposited on substrate as well in order to obtain desired the oxidation resistance property of MCO and high conductivity of LSM.
The oxidation rate of Crofer 22 H were effectively suppressed by LSM and MCO coating that the thickness of oxide were reduced from 4m of unprotected Crofer 22 H to 2m and 1m of protected sample, respectively. The crystal structure of MCO coating layer transformed from rock-salt to spinel that was followed by conductivity increment of 104 S/cm and volume expansion during annealing. The resistance ASR(Area-Specific-Resistance) for unprotected Crofer 22 H, LSM-coated, MCO-coated, composite coating MCO:LSM=7:3, 1:1 and 3:7 was 11.8, 9.8, 4.2, 6.4, 1.6 and 1.1(mΩcm2), respectively. The results indicated that the composite coating MCO:LSM=3:7 showed the lowest resistance from the attribution of high conductivity of LSM and good oxidation resistance of MCO.
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