The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
Scott A Barnett - One of the best experts on this subject based on the ideXlab platform.
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Stable, Low Polarization Resistance Solid Oxide Fuel Cell Anodes: La1–xSrxCr1–xFexO3-δ (x = 0.2–0.67)
Chemistry of Materials, 2014Co-Authors: Daniel E. Fowler, Scott A Barnett, Jacob M. Haag, Claire Boland, David M. Bierschenk, Kenneth R. PoeppelmeierAbstract:The perovskite series, La1–xSrxCr1–xFexO3-δ (x = 0.2, 0.3, 0.4, 0.5, 0.67, LSCrFe), was synthesized and examined as both single phase and LSCrFe–Gd0.1Ce0.9O2-β (GDC) composite solid oxide fuel cell anodes in full cells with La0.9Sr0.1Ga0.8Mg0.2O3-e/La0.4Ce0.6O2 bilayer electrolytes. Each anode demonstrated marked improvement in Polarization Resistance compared to prior studies on Fe-free La1–xSrxCrO3-δ-based anodes and in stability compared to studies on more Fe-rich compositions. Higher Fe content anodes yielded lower Polarization Resistances, with the x = 0.67 anodes obtaining Resistances of 0.275 Ω·cm2 for LSCrFe and 0.333 Ω·cm2 for LSCrFe-GDC in humidified H2 at 800 °C. The lower Polarization Resistance with increasing Fe content can be attributed to oxygen loss, which introduces significant ionic conductivity into these perovskites. Substitution of an intermediate amount of Fe and Sr into the perovskites can thus optimize anode performance.
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stable low Polarization Resistance solid oxide fuel cell anodes la1 xsrxcr1 xfexo3 δ x 0 2 0 67
Chemistry of Materials, 2014Co-Authors: Daniel E. Fowler, Scott A Barnett, Jacob M. Haag, Claire Boland, David M. Bierschenk, Kenneth R. PoeppelmeierAbstract:The perovskite series, La1–xSrxCr1–xFexO3-δ (x = 0.2, 0.3, 0.4, 0.5, 0.67, LSCrFe), was synthesized and examined as both single phase and LSCrFe–Gd0.1Ce0.9O2-β (GDC) composite solid oxide fuel cell anodes in full cells with La0.9Sr0.1Ga0.8Mg0.2O3-e/La0.4Ce0.6O2 bilayer electrolytes. Each anode demonstrated marked improvement in Polarization Resistance compared to prior studies on Fe-free La1–xSrxCrO3-δ-based anodes and in stability compared to studies on more Fe-rich compositions. Higher Fe content anodes yielded lower Polarization Resistances, with the x = 0.67 anodes obtaining Resistances of 0.275 Ω·cm2 for LSCrFe and 0.333 Ω·cm2 for LSCrFe-GDC in humidified H2 at 800 °C. The lower Polarization Resistance with increasing Fe content can be attributed to oxygen loss, which introduces significant ionic conductivity into these perovskites. Substitution of an intermediate amount of Fe and Sr into the perovskites can thus optimize anode performance.
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impact of pore microstructure evolution on Polarization Resistance of ni yttria stabilized zirconia fuel cell anodes
Journal of Power Sources, 2011Co-Authors: Scott J Cronin, James R. Wilson, Scott A BarnettAbstract:Abstract Temperature induced degradation in Solid Oxide Fuel Cell (SOFC) Ni-YSZ anodes was studied using both impedance spectroscopy and three-dimensional tomography via Focused Ion Beam–Scanning Electron Microscopy. A 100 h anneal at 1100 °C caused a 90% increase in cell Polarization Resistance, which correlated with the observed factor of ∼2 reduction in the electrochemically active three-phase boundary (TPB) density. The TPB decrease was caused by a significant decrease in pore percolation, and a reduction in pore interfacial area due to pores becoming larger and more equiaxed. The anneal caused no measurable change in average Ni particle size; Ni coarsening was apparently highly constrained in these anodes due to the relatively large YSZ volume fraction and low pore volume.
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Effect of composition of (La0.8Sr0.2MnO3–Y2O3-stabilized ZrO2) cathodes: Correlating three-dimensional microstructure and Polarization Resistance
Journal of Power Sources, 2010Co-Authors: James R. Wilson, J. Scott Cronin, Anh T. Duong, Sherri Rukes, Hsun Yi Chen, Katsuyo Thornton, Daniel R. Mumm, Scott A BarnettAbstract:Abstract Composite La 0.8 Sr 0.2 MnO 3 (LSM)–Y 2 O 3 -stabilized ZrO 2 (YSZ) cathodes with compositions ranging from 30:70 to 70:30 wt.% LSM:YSZ were studied both electrochemically and microstructurally. Polarization Resistance was lowest for the 50 wt.% YSZ composition, and increased symmetrically as the composition deviated from this value. Serial-sectioning using focused ion beam-scanning electron microscopy was implemented to reconstruct the three-dimensional cathode microstructure. Various averaged structural parameters were determined versus composition, including phase volume fractions, surface area densities, total triple-phase boundary (TPB) densities, interfacial curvatures, phase tortuosities, and the levels of phase connectivity. Typically >90% of the pore and YSZ networks were found to be intra-connected to the surrounding phase, but the LSM networks showed lower connected fractions, as low as 37.5% for a LSM weight fraction of 30%. The composition dependences of the total TPB density and electrochemically-active TPB density ( i.e. , TPB's on three fully intra-connected phases) were shown to agree reasonably well with simple “sphere-packing” structural models. An electrochemical model that accounted for the linear-specific Resistance of TPB's, phase intra-connectivity, and oxygen ion transport in the YSZ as influenced by its tortuosity, was found to provide reasonable agreement with the measured Polarization Resistance versus composition.
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effect of composition of la0 8sr0 2mno3 y2o3 stabilized zro2 cathodes correlating three dimensional microstructure and Polarization Resistance
Journal of Power Sources, 2010Co-Authors: James R. Wilson, Anh T. Duong, Sherri Rukes, Hsun Yi Chen, Katsuyo Thornton, Daniel R. Mumm, Scott J Cronin, Scott A BarnettAbstract:Abstract Composite La 0.8 Sr 0.2 MnO 3 (LSM)–Y 2 O 3 -stabilized ZrO 2 (YSZ) cathodes with compositions ranging from 30:70 to 70:30 wt.% LSM:YSZ were studied both electrochemically and microstructurally. Polarization Resistance was lowest for the 50 wt.% YSZ composition, and increased symmetrically as the composition deviated from this value. Serial-sectioning using focused ion beam-scanning electron microscopy was implemented to reconstruct the three-dimensional cathode microstructure. Various averaged structural parameters were determined versus composition, including phase volume fractions, surface area densities, total triple-phase boundary (TPB) densities, interfacial curvatures, phase tortuosities, and the levels of phase connectivity. Typically >90% of the pore and YSZ networks were found to be intra-connected to the surrounding phase, but the LSM networks showed lower connected fractions, as low as 37.5% for a LSM weight fraction of 30%. The composition dependences of the total TPB density and electrochemically-active TPB density ( i.e. , TPB's on three fully intra-connected phases) were shown to agree reasonably well with simple “sphere-packing” structural models. An electrochemical model that accounted for the linear-specific Resistance of TPB's, phase intra-connectivity, and oxygen ion transport in the YSZ as influenced by its tortuosity, was found to provide reasonable agreement with the measured Polarization Resistance versus composition.
Kenneth R. Poeppelmeier - One of the best experts on this subject based on the ideXlab platform.
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Stable, Low Polarization Resistance Solid Oxide Fuel Cell Anodes: La1–xSrxCr1–xFexO3-δ (x = 0.2–0.67)
Chemistry of Materials, 2014Co-Authors: Daniel E. Fowler, Scott A Barnett, Jacob M. Haag, Claire Boland, David M. Bierschenk, Kenneth R. PoeppelmeierAbstract:The perovskite series, La1–xSrxCr1–xFexO3-δ (x = 0.2, 0.3, 0.4, 0.5, 0.67, LSCrFe), was synthesized and examined as both single phase and LSCrFe–Gd0.1Ce0.9O2-β (GDC) composite solid oxide fuel cell anodes in full cells with La0.9Sr0.1Ga0.8Mg0.2O3-e/La0.4Ce0.6O2 bilayer electrolytes. Each anode demonstrated marked improvement in Polarization Resistance compared to prior studies on Fe-free La1–xSrxCrO3-δ-based anodes and in stability compared to studies on more Fe-rich compositions. Higher Fe content anodes yielded lower Polarization Resistances, with the x = 0.67 anodes obtaining Resistances of 0.275 Ω·cm2 for LSCrFe and 0.333 Ω·cm2 for LSCrFe-GDC in humidified H2 at 800 °C. The lower Polarization Resistance with increasing Fe content can be attributed to oxygen loss, which introduces significant ionic conductivity into these perovskites. Substitution of an intermediate amount of Fe and Sr into the perovskites can thus optimize anode performance.
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stable low Polarization Resistance solid oxide fuel cell anodes la1 xsrxcr1 xfexo3 δ x 0 2 0 67
Chemistry of Materials, 2014Co-Authors: Daniel E. Fowler, Scott A Barnett, Jacob M. Haag, Claire Boland, David M. Bierschenk, Kenneth R. PoeppelmeierAbstract:The perovskite series, La1–xSrxCr1–xFexO3-δ (x = 0.2, 0.3, 0.4, 0.5, 0.67, LSCrFe), was synthesized and examined as both single phase and LSCrFe–Gd0.1Ce0.9O2-β (GDC) composite solid oxide fuel cell anodes in full cells with La0.9Sr0.1Ga0.8Mg0.2O3-e/La0.4Ce0.6O2 bilayer electrolytes. Each anode demonstrated marked improvement in Polarization Resistance compared to prior studies on Fe-free La1–xSrxCrO3-δ-based anodes and in stability compared to studies on more Fe-rich compositions. Higher Fe content anodes yielded lower Polarization Resistances, with the x = 0.67 anodes obtaining Resistances of 0.275 Ω·cm2 for LSCrFe and 0.333 Ω·cm2 for LSCrFe-GDC in humidified H2 at 800 °C. The lower Polarization Resistance with increasing Fe content can be attributed to oxygen loss, which introduces significant ionic conductivity into these perovskites. Substitution of an intermediate amount of Fe and Sr into the perovskites can thus optimize anode performance.
R P Nogueira - One of the best experts on this subject based on the ideXlab platform.
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revisiting the astm c876 standard for corrosion of reinforcing steel on the correlation between corrosion potential and Polarization Resistance during the curing of different cement mortars
Electrochemistry Communications, 2018Co-Authors: Guilherme Yuuki Koga, Blandine Albert, R P NogueiraAbstract:Abstract This paper presents a probabilistic analysis of almost 700 potential and Polarization Resistance measurements of reinforcing steel embedded in 15 types of mortars of different nature and chloride contamination levels exposed to controlled conditions of temperature and relative humidity. Besides indicating that the ASTM C876 standard can be a robust and reliable commissioning tool for strategic assets in terms of effectiveness of reinforcing steel passivation, results show that the Polarization Resistance values follow different probability density functions at different potential levels, which means they do correspond to distinct interfacial processes.
Radhakrishna G Pillai - One of the best experts on this subject based on the ideXlab platform.
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Investigation on the Polarization Resistance of steel embedded in highly resistive cementitious systems – An attempt and challenges
Electrochimica Acta, 2019Co-Authors: Sripriya Rengaraju, Lakshman Neelakantan, Radhakrishna G PillaiAbstract:Abstract Concretes with fly ash, slag, limestone calcined clay, etc. exhibiting high resistivity are being used to enhance the chloride Resistance of structures – to achieve durability. Prior to use, the engineers need to determine the chloride threshold (Clth) of such highly resistive steel cementitious (S-C) systems (a key parameter to estimate service life). Most Clth tests involve repeated measurements of Polarization Resistance (Rp) and detection of corrosion initiation of steel embedded in hardened cementitious system (a sol-gel structure with partially filled pores). The high resistivity of such systems should be considered while interpreting the electrochemical response to determine Rp. This paper experimentally evaluates the suitability of LPR and EIS techniques for assessing Rp of steel embedded in highly resistive systems. Experiments were conducted with lollipop type specimens (steel reinforcement embedded in mortar cylinders). The following three types of mortar having various resistivities were prepared: (i) ordinary portland cement (OPC), (ii) OPC + fly ash, and (iii) limestone calcined clay cement. Experimental observations on how the following three factors affect the electrochemical response in highly resistive S-C systems are provided: (i) resistivity of concrete covering the embedded steel, (ii) electrode configuration, and (iii) electrochemical test parameters. It was found that electrochemical impedance spectroscopy (EIS) can detect corrosion initiation in highly resistive systems at earlier stages than the linear Polarization Resistance (LPR) technique. Also, the guidelines on how to use EIS technique to determine the Rp of steel embedded in highly resistive S-C systems are provided.
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investigation on the Polarization Resistance of steel embedded in highly resistive cementitious systems an attempt and challenges
Electrochimica Acta, 2019Co-Authors: Sripriya Rengaraju, Lakshman Neelakantan, Radhakrishna G PillaiAbstract:Abstract Concretes with fly ash, slag, limestone calcined clay, etc. exhibiting high resistivity are being used to enhance the chloride Resistance of structures – to achieve durability. Prior to use, the engineers need to determine the chloride threshold (Clth) of such highly resistive steel cementitious (S-C) systems (a key parameter to estimate service life). Most Clth tests involve repeated measurements of Polarization Resistance (Rp) and detection of corrosion initiation of steel embedded in hardened cementitious system (a sol-gel structure with partially filled pores). The high resistivity of such systems should be considered while interpreting the electrochemical response to determine Rp. This paper experimentally evaluates the suitability of LPR and EIS techniques for assessing Rp of steel embedded in highly resistive systems. Experiments were conducted with lollipop type specimens (steel reinforcement embedded in mortar cylinders). The following three types of mortar having various resistivities were prepared: (i) ordinary portland cement (OPC), (ii) OPC + fly ash, and (iii) limestone calcined clay cement. Experimental observations on how the following three factors affect the electrochemical response in highly resistive S-C systems are provided: (i) resistivity of concrete covering the embedded steel, (ii) electrode configuration, and (iii) electrochemical test parameters. It was found that electrochemical impedance spectroscopy (EIS) can detect corrosion initiation in highly resistive systems at earlier stages than the linear Polarization Resistance (LPR) technique. Also, the guidelines on how to use EIS technique to determine the Rp of steel embedded in highly resistive S-C systems are provided.
Jeffry Stevenson - One of the best experts on this subject based on the ideXlab platform.
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New insights in the Polarization Resistance of anode-supported solid oxide fuel cells with La0.6Sr0.4Co0.2Fe0.8O3 cathodes
Journal of Power Sources, 2011Co-Authors: Zigui Lu, Jared Templeton, John Hardy, Jeffry StevensonAbstract:In this study, the Polarization Resistance of anode-supported solid oxide fuel cells (SOFC) with La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) cathodes was investigated by I–V sweep and electrochemical impedance spectroscopy under a series of operating voltages and cathode environments (i.e. stagnant air, flowing air, and flowing oxygen) at temperatures from 550 °C to 750 °C. In flowing oxygen, the Polarization Resistance of the fuel cell decreased considerably with the applied current density. A linear relationship was observed between the ohmic-free over-potential and the logarithm of the current density of the fuel cell at all the measuring temperatures. In stagnant or flowing air, an arc related to the molecular oxygen diffusion through the majority species (molecular nitrogen) present in the pores of the cathode was identified at high temperatures and high current densities. The magnitude of this arc increased linearly with the applied current density due to the decreased oxygen partial pressure at the interface of the cathode and the electrolyte. It is found that the performance of the fuel cell in air is mainly determined by the oxygen diffusion process. Elimination of this process by flowing pure oxygen to the cathode improved the cell performance significantly. At 750 °C, for a fuel cell with a laser-deposited Sm0.2Ce0.8O1.9 (SDC) interlayer, an extraordinarily high power density of 2.6 W cm−2 at 0.7 V was achieved in flowing oxygen, as a result of reduced ohmic and Polarization Resistance of the fuel cell, which were 0.06 Ω cm2 and 0.03 Ω cm2, respectively. The results indicate that microstructural optimization of the LSCF cathode or adoption of a new cell design which can mitigate the oxygen diffusion limitation in the cathode might enhance cell performance significantly.
