材料期刊网

通过溶胶--凝胶提拉法在SUS 430合金表面施加LaCoO₃钙钛矿导电涂层, 并研究其对固体氧化物燃料电池(SOFC)金属连接体SUS 430合金中温氧化行为的影响. 利用X射线衍射(XRD)、扫描电子显微镜(SEM)以及能谱仪(EDS)对施加涂层合金的氧化物相结构与微观形貌进行表征, 并采用“4点法”测量施加涂层合金表面氧化膜的面比电阻(ASR).750 ℃空气中的循环氧化结果表明, 施加LaCoO₃涂层合金的氧化动力学曲线遵循抛物线规律,氧化速率常数K为4.18×10^-15 g²/(cm⁴•s),比与未施加涂层合金降低了1---2个数量级;LaCoO₃涂层有效地抑制了Cr₂O₃相的形成, 减缓了MnCr₂O₄尖晶石的生长. 最终使得SUS 430合金的氧化抗力和氧化后的导电性得到增强.

Low costly ferritic stainless steels, especially the Cr₂O₃–forming alloys, are promising interconnect materials for solid oxide fuel cells (SOFCs) due to their thermal expansion compatibility with other cell components. However, the oxidation resistance of commercial ferritic stainless steels in the operating temperature range of 600—800 ℃ is not adequate, forming relatively thick, poorly conducting oxide scale on the surface of the stainless steel interconnect and decreasing the cell performance. Surface modification is necessary to improve the oxidation behavior and electrical property. The present study investigates the effect of a LaCoO₃ protective coating by the sol–gel process on the intermediate temperature oxidation behavior of SUS 430 alloy, which is frequently considered as the interconnect material for SOFCs. X–ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize the phase structure, surface morphology and composition of the coating and the oxide scale. The "4–probe" method was employed to determine the area specific resistance (ASR) of the surface oxides. Long–term thermally cyclic oxidation at 750 ℃in air has shown that the oxidation kinetics obeys the parabolic rule with a rate constant of K=4.18×10−15 g²/(cm⁴·s), which is 1—2 orders of magnitude lower than that of the uncoated alloy, the LaCoO₃ protective coating effectively suppresses the formation of Cr₂O₃ and slows down the growth of MnCr₂O₄ spinel. As a result, the oxidation resistance and electrical conductivity of the coated SUS 430 alloy are significantly enhanced, resulting in an ASR at 750 ℃of only 3.13 m·cm² after oxidation at 750 ℃ for 850 h in air and an extrapolated ASR of 21.5 m·cm² for 4×10⁴ h oxidation.