【作者】 华斌；

【导师】 李箭； 蒲健；

【作者基本信息】 华中科技大学 ， 纳米科学与技术， 2007， 硕士

【摘要】 以固体氧化物燃料电池（SOFC）金属连接体为应用背景,研究了SUS 430铁素体不锈钢和Haynes 230合金分别在模拟SOFC阴极气氛（空气）和阳极气氛（燃料气:H₂+H₂O）中高温氧化（650℃、750℃和850℃）分别长达500小时的高温氧化行为。利用氧化增重实验研究两种合金分别在不同气氛及等温温度下的氧化动力学,并利用X射线薄膜衍射技术、扫描电镜（SEM）及其附设的能谱（EDS）对合金表面氧化物的相组成与演化、氧化物的表面微观形貌及厚度、氧化物的成分进行表征分析。同时也通过溶胶-凝胶技术在SUS 430合金上施加LaCoO3导电涂层,研究了涂层对SUS 430合金作为SOFC金属连接体的影响,利用X射线衍射和扫描电镜研究涂层和氧化物膜的相结构及表面微观形貌。结果表明,两种合金的氧化动力学都呈现出阶段氧化特性,且每一阶段都遵循Wagner抛物线定律,并具有不同的抛物线氧化速率。合金表面都形成多层氧化物,多层氧化物的形成对应于不同的氧化动力学阶段,合金氧化物的生成主要受离子的扩散过程所控制,氧化产物主要为Cr2O3和MnCr2O4尖晶石。SUS 430合金在850℃阴极气氛下氧化时氧化膜产生氧化破裂甚至剥落。SUS 430在850℃阳极气氛下氧化时,FeO也成为主要的氧化产物,并有相当数量的Fe分布于其中。LaCoO3导电涂层降低了SUS 430金属连接体的氧化速率,使SUS 430在850℃阴极气氛下第二阶段的氧化速率降低了约一个数量级,有效地提高了其高温抗氧化能力。通过采取“四点法”对合金表面氧化物面比电阻（ASR）进行测试发现,氧化物在高温下都体现出半导体的电学特性,随着测量温度的升高其电阻降低。其中Haynes 230具有较高的导电性能,但SUS 430合金和Haynes 230合金的ASR均比同等条件阴极气氛下的大（尤其当氧化温度较高时）。通过对涂层合金表面氧化物电阻进行估算表明,LaCoO3导电涂层有效的提高了SUS 430合金的导电能力。更多还原

【Abstract】 In order to apply metallic interconnect for solid oxide fuel cell （SOFC）, the oxidation behaviors of Haynes 230 alloy and SUS 430 alloy at high temperature （650℃, 750℃and 850℃） for up to 500 hours have been investigated, simulating the environment of SOFC cathode atmosphere （air） and anode atmosphere （fuel gases: H₂+H₂O） respectively. The oxidation kinetics of the two alloys in different atmosphere and temperature has been investigated by the weight gain of oxidation. The oxidation behaviors of the samples such as phase constitution, phase evolvement, microstructure and thickness, and elements of the oxide scales which formed on the surface of the alloys were analyzed by the thin film X-ray diffraction （XRD）, scanning electron microscope （SEM） and energy dissipation spectroscopy （EDS） attachment. Further more, a LaCoO3 conducting coating synthesized by Sol-Gel method was applied on SUS 430 alloy, whose effect on the SUS 430 alloy as metallic interconnect in SOFC was investigated. The structure and surface morphology of coating and oxide film were characterized by XRD and SEM. The experimental results show that multi-stages oxidation kinetics was observed about the two alloys at various oxidation conditions, and each stage follows Wagner’s parabolic law with different parabolic oxidation rate constants. And a duplex oxide scale was found formed on the surface of alloys, corresponding to the various oxidation kinetics stages. Formations of oxides were mainly controlled by the diffusion of ions. Cr2O3 and MnCr2O4 spinel were the main oxidation products in all oxide scales. The oxide scale cracking and spallation from the substrate were observed when SUS 430 alloy oxidized in air at 850℃. FeO was also the main oxidation product with some dissolved Fe in the oxide scale when SUS 430 alloy oxidized in anode atmosphere at 850℃for up to 500 hours. The oxidation rate of SUS 430 metallic interconnect oxidized in air at 850℃between 200h and 500h by applied LaCoO3 conducting coating have been reduced approximately a magnitude. The LaCoO3 conducting coating was effective in protecting the metallic interconnect from oxidation. The area-specific resistance （ASR） of the oxide scales was measured by“four-probe”method. The results show a typical of semiconductor behavior, the resistance decrease gradually along with the rise of temperature. Haynes 230 have higher electric capability, but the ASR of SUS 430 alloy and Haynes 230 alloy oxidized in anode atmosphere are both higher than the ASR of the two alloys oxidized in air, especially oxidized in high temperature. By evaluating the resistance of the oxide which was applied the coating, showing that the LaCoO3 conducting coating was effective in improving the high temperature electric capability of SUS 430 alloy.更多还原