Effect of cathode contacting on anode supported cell performances and degradation

The contact geometry effect on anode-supported cells (ASC) has been evaluated comparing the use of platinum meshes and Crofer 22 APU bipolar plates as current collectors. Additionally, the application of a La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) paste between the electrode and the current collector allowed estimating the beneficial effect of the contacting layer enhancing the current distribution at the cathode side. Cells have been electrically loaded for 100 hours to investigate the polarization effects on their performances by means of current-voltage curves and electrochemical impedance spectroscopy. Post-experiment analyses have been carried out to support the electrochemical observation

Interaction between crofer 22 APU current collector and LSCF cathode contacting layer under cell operation

In this work the oxidation of Crofer 22 APU and its interaction with La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) applied as contacting layer have been investigated in air at 750\ub0C under a current load of 0.5 Acm-2 with the aim to reproduce as close as possible the interconnect interface in real operating conditions. The effects of such interaction and of the pre-oxidation treatment have been studied by means of ASR measurement and post-experiment characterizations. The behavior of such samples has been compared with the results on a working Crofer 22 APU bipolar plate tested as cathode current collector of an anode-supported cell reproducing the stack cathode compartment conditions

Aging of materials at inlet and outlet fuel manifolds in a SOFC stack

Analyses performed on a stack operated for more than 4000h at 750\ub0C at high fuel utilization (80%) revealed significant differences in aging behaviour of stack components when comparing fuel inlet and fuel outlet areas. Two samples were cut from the fuel inlet and outlet manifolds of the operated SOFC stack. The glass-ceramic sealing material and the interconnect alloy were exposed to a dual atmosphere (external air and internal fuel stream). The fuel composition was dry H2/N2 (60:40 vol. %) at the inlet and H2O/H2/N2 (48:12:40 vol. %) at the outlet. The stack was operated in co-flow configuration, with a large excess of air. It was found that the interfaces between the seal and the alloy were significantly affected by the difference in fuel composition. The sealant exposed to the outgoing air was significantly polluted by chromium generated in the stack and transported by the air stream. These investigations therefore reveal that the long-term evolution of the sealing and of the metallic support depends on the local conditions in the stack, as well as on additional interactions with other degradation phenomena

Socio-environmental impacts of non-native and transplanted aquatic mollusc species in South America: What do we really know?

The impacts of biological invasions remain poorly known for some habitats, regions and taxa. To date, there has been no comprehensive effort to review and synthesize the impacts of invasive mollusc species in South America. In this paper, we provide a synoptic view on what is known on documented socio-ecological impacts of aquatic no-native mollusc species (NNMS) and transplanted mollusc species (TMS) from South America. An expert group involving malacologists and taxonomists from different countries, the “South America Alien Molluscs Specialists” (eMIAS), shared and summarized the scientific literature, databases, and published and unpublished information on confirmed impacts of NNMS and TMS in South America. Three broad categories, non-mutually exclusive were used as a framework: “Environmental/Biodiversity impacts”, “Economic and social effects”, and “Human health impacts”. Some 21 NNMS and seven TMS have documented impacts on at least one of those three categories. We encourage targeting the less known areas of research, such as economic valuation of human health (and veterinary) impacts attributable to NNMS or TMS and expand our knowledge of environmental impacts for the species listed in this study.Fil: Carranza, Alvar. Universidad de la República; Uruguay. Museo Nacional de Historia Natural Uruguay; UruguayFil: Agudo Padrón, Ignacio. Projeto “avulsos Malacológicos”; BrasilFil: Collado, Gonzalo A.. Universidad del Bio Bio; Chile. Sociedad Malacológica Chile; ChileFil: Damborenea, Maria Cristina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Zoología Invertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Fabres, Alejandra. Sociedad Malacológica Chile; Chile. Universidad Católica de Maule; ChileFil: Gutierrez Gregoric, Diego Eduardo. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Zoología Invertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Lodeiros, Cesar. Universidad Técnica de Manabí; Ecuador. Universidad de Oriente; VenezuelaFil: Ludwig, Sandra. Universidade Federal de Minas Gerais; BrasilFil: Pastorino, Roberto Santiago Guido. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Penchaszadeh, Pablo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Salvador, Rodrigo B.. Museum of New Zealand Te Papa Tongarewa,; Nueva Zelanda. The Artic University of Norway; NoruegaFil: Spotorno, Paula. Universidade Federal do Rio Grande; BrasilFil: Thiengo, Silvana. Fundación Oswaldo Cruz; BrasilFil: Vidigal, Teofania Heloisa Dutra Amorim. Universidade Federal de Minas Gerais; BrasilFil: Darrigran, Gustavo Alberto. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División de Zoología Invertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin

Application of the Differential Impedance Analysis (DIA) on the Microbiologically Induced Corrosion (MIC) of Bronze

In this work, the behavior of a binary Cu-Sn (12wt% Sn) alloy has been studied in presence and absence of bacteria in aqueous solution simulating stagnant fresh water. The corrosion processes have been investigated using the Electrochemical Impedance spectroscopy (EIS) technique. The application of the Differential Impedance Analysis (DIA) allowed identifying three processes attributed to the electrical double layer, electrical properties of the passive film and mass transfer processes at the metal/solution interface. Based on DIA structural analysis, equivalent circuit model was proposed and used for better parametric identification of the impedance data. The formation of a biofilm strongly influenced the passive layer behavior, promoting localized corrosion. Post-experiment characterization performed by Scanning electron microscopy (SEM) supported the electrochemical characterization

Combined experimental and modeling study of interaction between LSCF and CGO in SOFC cathodes

The development of a high-performance oxygen electrode for SOFCs in order to achieve high power density at a stack level is still challenging. It is important to emphasize the factors controlling the efficiency of the cathode. Over the intrinsic electro-catalytic activity of the cathode material itself toward the oxygen reduction, the microstructural parameters such as the porosity, the tortuosity or the particle size are of major importance in the definition of the electrochemical active surface area. In this paper we focus on the behavior of La0.6Sr0.4Co0.2Fe0.8O3-α (LSCF)-Ce1-xGdxO2-α (CGO) composite cathodes with different development and characterization of composite cathodes produced by suspension spraying and sintering, with or without further surface modification by infiltration either LSCF or CGO nano-particles. Different symmetrical cells were produced by varying the LSCF/CGO ratio with an active surface area of about 12.57 cm2. Cells were contacted with a fine platinum mesh without any contacting paste and electrochemical impedance spectra (EIS) were recorded in static ambient air in the frequency range 10 mHz – 100 kHz between 500 °C and 800 °C. The serial resistance (Rs) and the total polarization resistance (Rp) were both quantified. The developed kinetic model of oxygen reduction at LSCF/CGO cathode, which incorporates elementary heterogeneous chemistry and electrochemical charge-transfer processes at two different electrochemical double layers, transport in the porous composite electrode, as well as gas supply, is used to explain the non-intuitive interaction between LSCF and CGO phases. This allows a mechanistic interpretation of the origin of different chemical, electrochemical and transport phenomena occurring in composite cathodes

Investigation of a Metallic Interconnect Extracted from an SOFC Stack after 40,000 h of Operation

An in-depth investigation was performed on a metallic interconnect extracted from an SOFC stack operated for 40,000 h. The characterization was performed on the surface and the cross-section, paying attention to the evolution of the materials due to the interaction with the dual atmosphere of the stack under operating parameters. The interaction between materials (i.e., metal substrate, coatings and atmospheres) and stack components (i.e., current collectors and MIC) generated several modifications that affected the surface and, in some cases, the bulk of the interconnect. The careful metallographic preparation allowed for the performance of an intensive microscopical characterization of the cross-sections all along the interconnect profile, from the inlet to the outlet of the fuel stream. The formation of thermal grown oxides on both sides and their evolution were studied and described. The interconnect, after 40,000 h, was still suitable for operation, but the few bulk changes due to the diffusion of Ni and the TGO that formed at the fuel side suggest the introduction of fuel side coatings to increase the life expectations of the whole stack