Interactions between Metallic Interconnects and Ceramic Electrodes in SOFC Operating Environments: Air Side

Abstract

Ferritic stainless steel (FSS) bipolar plates are widely used to interconnect individual cells in planar Solid Oxide Fuel Cell (SOFC) stacks. In this study, thin films of ceramic and cermet electrode materials, La 0.8 Sr 0.2 MnO 3 (LSM) for the cathode and Ni-Y 2 O 3 /ZrO 2 (Ni-YSZ) for the anode, were screen printed on Sanvik's Sanergy HT, a specialty FSS alloy (with and without Co or Co/Ce surface coatings). Samples were then placed in a test rig which allows simultaneous exposures to humidified (3% H 2 O) single (air/air) and dual atmospheres (air/H 2 ) at 800 • C for 100 hours. This research is focused on the FSS surface oxide layers and the phenomena governing materials interactions during realistic SOFC exposures that drive degradation. The surface oxide layer composition and morphology are heavily influenced by the dual atmosphere exposures and contact with electrode materials. For example, air-side surface oxide layers are generally thicker and contain more Fe than those formed in single-atmospheres, and surface oxide layer thickness and composition is altered in the presence of contacting electrodes in comparison with gas-only exposures. These and other recent data suggest that corrosion studies performed without relevant SOFC stack environments (e.g., air-only and without contacting electrodes) may not reveal all of the pertinent high-temperature behaviors.

Identifying the Origin of the Limiting Process in a Double Perovskite PrBa0.5Sr0.5Co1.5Fe0.5O5+δ Thin-Film Electrode for Solid Oxide Fuel Cells

“…21,23 Characterization techniques, such as energydispersive spectrometry (EDS) with high-resolution transmission electron microscopy, performed to study the composi-tional changes on the surface are likely to average compositions over a much greater penetration depth from the surface. 56 This was indeed the case when EDS performed by Choi et al did not show any compositional changes on the surface, compared to the bulk of the PBSCF electrode material. 14 Later, in an indirect manner, Pu and co-workers demonstrated the segregation of BaO on the surface of the PBSCF electrode.…”

“…As pointed by McIntosh, , Druce, and their co-workers, LEIS is certainly a better characterization technique for probing the segregation of cation species on the surface of the PBCO and GBCO double perovskite electrodes. X-ray photoelectron spectroscopy (XPS) measurements which average out over several atomic layers (around 5 nm) may also show the same segregation in the outermost surface layers. , However, the XPS spectra, generally, are indicative in nature and may not provide conclusive evidence in establishing surface cation segregation in double perovskites, specifically in case of overlapping peaks. , In this regard, experimental techniques following reactions with other elements may provide a direct evidence. , Characterization techniques, such as energy-dispersive spectrometry (EDS) with high-resolution transmission electron microscopy, performed to study the compositional changes on the surface are likely to average compositions over a much greater penetration depth from the surface . This was indeed the case when EDS performed by Choi et al did not show any compositional changes on the surface, compared to the bulk of the PBSCF electrode material .…”

The effect of Milling Time on Crystal size Sandvik Sanergy

“…Materials that have been used to develop interconnect materials in SOFC applications include Crofer 22 APU, Hitachi ZM6232, Hitachi ZM6232L, Allegheny Ludlum ATI E-Brite, Planse Ducrolloy Cr-5Fe-Y2O3 and sandvik sanergy. (Werner and Skilbred 2012), (Bash 2015), (Amendola et al 2012), (Alvarez et al 2011). Apart from sandvik sanergy (SS), these materials do not meet the requirements for a fuel cell system when operating at 700-850°C (Amendola et al 2012).…”

“…(Werner and Skilbred 2012), (Bash 2015), (Amendola et al 2012), (Alvarez et al 2011). Apart from sandvik sanergy (SS), these materials do not meet the requirements for a fuel cell system when operating at 700-850°C (Amendola et al 2012).…”