CAREER: Novel Conductive Oxide Coatings on Metallic Inteconnect for Intermediate Temperature SOFC Application

本项目旨在解决中温固体氧化物燃料电池（SOFC）应用中金属互连相关的关键问题。随着目前将SOFC工作温度降低到500-800℃的趋势，铁素体钢因其低成本和易于制造而被推广为中温SOFC互连的候选材料。然而，在长期堆叠操作下，由于表面氧化层的形成和铬从互连向其他电池组件的迁移而增加的接触电阻对这些原本有前途的材料构成了严重的问题。本文研究了一种新的导电尖晶石相作为潜在的涂层，以减轻铁素体钢的电流限制。通过对取代尖晶石相缺陷结构和电导率的系统研究，评价取代尖晶石相的导电机理。将通过溶胶-凝胶工艺在铁素体钢上制备具有优化成分的尖晶石涂层。另一个目标是探索合金设计，开发新一代铁素体合金，能够在适当的热处理后形成所需的尖晶石层。该研究还旨在通过使学生熟悉大块材料和薄膜/涂层的加工和表征来加强本科/研究生课程。尖晶石相具有广泛的导电性，从绝缘/半导体到类金属/超导。本研究将结合热重分析、电导率和塞贝克系数测量、中子散射、同步加速器x射线散射以及相关的建模工作等多种技术和方法，深入研究尖晶石相的缺陷结构和传导机制。所开发的方法将直接适用于许多其他重要的导电陶瓷。除了SOFC互连应用之外，所开发的溶胶-凝胶尖晶石涂层和新一代铁素体合金也可以在其他苛刻的恶劣环境中得到广泛应用。该综合教育活动旨在通过每年组织为期一周的夏季材料夏令营，向田纳西州上坎伯兰地区的高中生和教师展示拟议的燃料电池研究活动和田纳西理工大学（TTU）和国家实验室最先进的材料研究设施。

This project aims at addressing the critical issues related to metallic interconnects for intermediate-temperature solid oxide fuel cell (SOFC) application. With the current trends in reducing the SOFC operation temperatures to the range of 500-800 degrees C, ferritic steels are promoted as the candidate materials for the intermediate-temperature SOFC interconnect due to their low cost and ease of manufacture. However, under long-term stack operation, the increase of contact resistance due to the formation of surface oxide layer(s) and Cr migration to other cell components from the interconnects pose serious issues for these otherwise promising materials. Novel conductive spinel phases are investigated in this proposal as potential coatings to mitigate the current limitations of ferritic steels. Electrical conduction mechanism in substituted spinel phases will be assessed through systematic study of defect structure and electrical conductivity in these oxides. Spinel coatings with optimized composition will be fabricated, via sol-gel processing to form the coatings on commercial ferritic steels. Another objective is to explore alloy design to develop new-generation ferritic alloys capable of forming the desired spinel layer upon proper thermal treatment. The research is also directed to enhance the undergraduate/graduate curricula by familiarizing the students with processing and characterization of both bulk materials and thin films/coatings. Spinel phases exhibit a wide range of electrical conductivity, ranging from insulating/semiconducting to metal-like/superconducting. This research will provide insights into defect structure and conduction mechanism in spinel phases, by combining various techniques and approaches, such as thermogravimetric analysis, electrical conductivity and Seebeck coefficient measurements, neutron scattering, synchrotron X-ray scattering, and the associated modeling efforts. The methodology developed will be directly applicable to a number of other important electron-conducting ceramics. In addition to the intended SOFC interconnect application, the developed sol-gel spinel coatings and new-generation ferritic alloys may also find wide applications in other demanding, hostile environments. The integrated educational activities will be aimed at exposing the high school students and teachers in the Upper-Cumberland region of Tennessee by organizing a weeklong summer materials camp each year, to the proposed fuel cell research activities and state-of-the-art material research facilities at Tennessee Technological University (TTU) and national laboratories.