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

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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.