Fabrication And Property Investigations Of Dual Layer Coatings On Metallic Interconnectsfor Solid Oxide Fuel Cell

Solid oxide fuel cells(SOFCs) are highly efficient power generation systems, which have attracted significant attention due to their fuel flexibility and environmental advantages. Oxidation resistant metallic alloys have advantages of easy fabrication, low material cost, significantly better mechanical properties and higher electrical and thermal conductivity. Gradually, oxidation resistant metallic alloys are used as interconnect materials instead of conventional doped lanthanum chromite ceramics(LaCrO3).However, the evaporation of volatile Cr species is a serious problem associated with these chromia-forming alloys, which leads to a rapid cathode performance degradation. Therefore, dual layer coatings, made of spinel and perovskite layers have been investigated in order to improve the overall oxidation resistance of the metallic interconnect and its electrical contact to the cathode. Perovskite oxides such as La0.6Sr0.4CoO3(LSC), La0.6Sr0.4Fe0.8Co0.2O3(LSCF), La0.6Sr0.4Cu0.9Fe0.1O3(LSCuF) and Sm0.5Sr0.5CoO3(SSC) are the most promising candidates in consideration of the conductivity, coefficient of thermal expansion, sintering behavior, and tendency to react with cathode materials. These perovskite oxide stypically require sintering at high temperature(>1100°C). However, the excessive sintering temperature will cause serious oxidation of the metallic interconnect. In order to avoid the excessive oxidation, it needs a new preparation process for the preparation of the cathode contact layer.In the present work, we propose a different approach for deposition of dual layer coatings on stainless steel interconnect. Cobalt layer is deposited by electroplating on commercial SUS430 stainless steel. For liquid phase sintering method, La0.6Sr0.4Co O3-δfor cathode contact layer is then applied by screen printing and sintered at 900°C in air, Co3O4 is used as sintering additives to improve sintering behavior of the contact layer. Dual layer coatings Co3O4 and La0.6Sr0.4CoO3-δare formed by subsequent oxidation at 800 ℃ in air. For In-situ phase formation method, composite La0.6Sr0.4CoO3-δprecursors-Ce0.8Gd0.2O2-δ for cathode contact layer is applied by screen printing. The dual layer coatings are sintered at 1100°C in Ar atmosphere, in order to not only achieve good bonding and adhesion, but also reduce oxidation damage to SUS430 ferritic stainless steel substrate. The phases of Co3O4 and La0.6Sr0.4CoO3-δ are in-situ formed by subsequent oxidation at 800°C in air. The interconnect with dual layer coatings exhibits a reduced ASR of about 23mΩcm2 as compared to uncoated one with ASR of 64mΩcm2 after isothermal oxidation at 800°C for 200 h.The dual layer coatings effectively improve the oxidation resistance and electrical properties of SUS430 steel substrate.