铁素体合金表面复合尖晶石涂层的研究进展

Composite Spinel Protective Coating for Ferritic Stainless Steel:a Review

固体氧化物燃料电池(SOFC)因具有清洁、高效等优点而得到了世界各国的广泛研究。连接体是研究SOFC的关键组件之一,近年来研究最多的SOFC连接体材料是铁素体不锈钢,其在实际的生产应用中具有导热性好、热膨胀系数匹配性好等优点。但“阴极铬中毒”、高温导电性和抗氧化性差等问题又限制了这一材料的应用,常见的解决办法是在表面制备保护涂层,如活性元素氧化物涂层、稀土钙钛矿涂层、复合尖晶石涂层等,其中复合尖晶石涂层被普遍认为是最具应用前景的SOFC连接体涂层。关于复合尖晶石涂层的性能及优化研究主要集中在成分、制备工艺和连接体三个方面。在成分方面,对比研究电导率、热膨胀系数、面比电阻和氧化速率常数等参数发现,Cu-Mn尖晶石涂层的电导率最高,而Co-Mn尖晶石的综合性能最好。还可以通过在尖晶石晶体中掺杂铜、铁来提高涂层的电导率,在涂层中掺杂活性元素及其氧化物来降低面比电阻、提高涂层的高温抗氧化性。在制备工艺方面,电泳沉积、磁控溅射等方法所制备的涂层均匀致密,能很好地黏附在基体表面,涂层性能优越。在连接体方面,凹面少、表面平整的连接体所制备的涂层性能更加稳定。本文详尽地归纳了近年来关于SOFC连接体的复合尖晶石保护涂层的研究,从成分、制备工艺和连接体三个方面讨论了涂层的优化方法,并指明了研究趋势,可以为推动金属连接体的工业化应用提供指导。

Solid oxide fuel cells(SOFC) have been widely studied in recent years because they can efficiently use fossil fuels and also collect gas andwaste heat. The interconnect is one of the key components of the SOFC,which directly affects the long-term stability of the stack. At present,the ferritic stainless steel is one of the most important interconnect materials,which has advantages of high thermal conductivity,suitable coefficient of thermal expansion,and so on. However,its applications are still limited by several problems such as cathode Cr poisoning,poor electrical conductivity and insufficient oxidation resistance at high temperature. The normal solution is to prepare protective coatings on the surface of the ferritic stainless steel,such as reactive element oxides(REOs) coatings,rare earth perovskite coatings,composite spinel coatings,etc.Composite spinel coatings are generally considered to be the most promising SOFC interconnect coatings. The research and performance optimization of composite spinel coatings mainly focus on the composition,preparation technology and interconnect. In terms of composition,it is found that Cu-Mn spinel coating has the highest electrical conductivity,while Co-Mn spinel has the best comprehensive performance considering the electrical conductivity,coefficient of thermal expansion(CTE),area specific resistance(ASR),oxidation rate constant(K) and other parameters. At the same time,the electrical conductivity of coatings can be improved by the doping of copper or iron,while the electrical resistance can be reduced and the high-temperature oxidation resistance can be improved by the doping of REOs. In terms of preparation technology,the coatings prepared by electrophoretic deposition,magnetron sputtering and other methods,have superior performance which are uniform and dense and adhere well to the surface of the substrate. In terms of the metallic interconnect,the performance of coatings is more stable,when the interconnect has less concave and flatter surface.In this paper,the recent works on composite spinel protective coatings for SOFC metallic interconnects are summarized in detail. The optimization methods of coatings are discussed in terms of composition,preparation technology and metallic interconnect,and the direction of the development is predicted. This work can provide guidance for promoting the industrial application of metallic interconnects.