Abstract
Low-temperature solid oxide fuel cells permit the possibility of metallic interconnects over conventional ceramic interconnects. Among various metallic interconnects, the ferritic interconnects are the most promising. However, chromium poisoning in them adversely affects their performance. To resolve this issue, various coatings and pretreatment methods have been studied. Herein, this article encloses the coating of CuFe2O4 spinel over two prominent ferritic interconnects (Crofer 22 APU and SUS 430). The CuFe2O4 spinel layer coating has been developed by the dip-coating of both samples in CuFe2O4 slurry, followed by heat treatment at 800 °C in a reducing environment (5% hydrogen and 95% nitrogen). Additionally, both samples were annealed to further enhance their spinel coating structure. The morphological and crystallinity analysis confirmed that the spinel coating formed multiple layers of protection while annealing further reduced the thickness and improved the densities. Moreover, the area-specific resistance (ASR) and weight gain rate (WGR) of both samples before and after annealing was calculated using mathematical modeling, which matches with the experimental data. It has been noted that CuFe2O4 spinel coating improved the ASR and WGR of both samples which were further improved after annealing. This research reveals that the CuFe2O4 spinel is the promising protective layer for ferritic interconnects and annealing is the better processing technique for achieving the preferred properties.
Highlights
Limited reserves of fossil fuels and increasing demand for clean energy have increased the need for alternative sources of power
Modern technology of Solid Oxide Fuel Cell (SOFC) allows for the use of metallic interconnects instead of ceramics because metals have better electrical conduction at low temperatures, a compatible value of Co-efficient of Thermal Expansion (CTE), structural stability and high density [5,6,7,8,9,10,11,12,13,14]
Crofer 22 APU and SUS 430 are metallic interconnects of SOFC which were coated by a spinel layer of CuFe2 O4 for oxidation resistance
Summary
Limited reserves of fossil fuels and increasing demand for clean energy have increased the need for alternative sources of power. SUS 430 is commercial ferritic steel, which shows comparable results against operational hours of SOFC [15,25,26] It has recently come under research as a future metallic interconnect. Despite the high performances of these alloys, interconnects require further reduction in oxidation [27,28], which raises the concept of external coating It includes multiple compositions of spinel layers such as coatings of cobalt (Co), manganese (Mn), copper (Cu) and different reactive materials. Shujiang Geng et al thermally grew CuFe2 O4 spinel over Crofer 22 APU by magnetron sputtering method They found that the double layers were formed over steel substrate. Annealing will improve crystallinity and lattice structure of the spinel, which will assist in densification and reduction in porosity of the spinel layer
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