The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Stuart James Rowen - One of the best experts on this subject based on the ideXlab platform.
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stainless steel as a bipolar Plate Material for solid polymer fuel cells
Journal of Power Sources, 2000Co-Authors: D P Davies, Paul Leonard Adcock, Mark Christopher Turpin, Stuart James RowenAbstract:Stainless steel bipolar Plates for the Solid Polymer Fuel Cell (SPFC) offer many advantages over conventional graphitic Materials. These include relative low cost, high strength, ease of manufacture and as they can be shaped into thin sheets, significant improvement in the power/volume ratio. However, interfacial ohmic losses across the metallic bipolar Plate and the Membrane Electrode Assembly (MEA), reduce the overall power output from a SPFC. Despite a large range of commercially available alloys, 316 stainless steel has traditionally been the alloy of choice for bipolar Plates. A number of alternative grades of stainless steel have been evaluated in terms of the electrical resistance of their surface oxide film. This showed that ohmic losses exhibited in fuel cell performance varied depending on the elemental composition of the stainless steel alloy. Three stainless steel alloys, 310, 316 and 904L, were chosen as candidate bipolar Plate Materials. Increased polarisation was observed in the order 904L<310<316. This was maintained throughout an ongoing endurance test, where these cells have been run for over 3000 h without significant performance degradation. This difference in polarisation behaviour was attributed to variation in thickness of the oxide film. Analysis has shown no deleterious effect on the surface of the bipolar Plate and no evidence of corrosion.
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Stainless steel as a bipolar Plate Material for solid polymer fuel cells
Journal of Power Sources, 2000Co-Authors: D P Davies, Paul Leonard Adcock, M. Turpin, Stuart James RowenAbstract:Stainless steel bipolar Plates for the Solid Polymer Fuel Cell (SPFC) offer many advantages over conventional graphitic Materials. These include relative low cost, high strength, ease of manufacture and as they can be shaped into thin sheets, significant improvement in the power/volume ratio. However, interfacial ohmic losses across the metallic bipolar Plate and the Membrane Electrode Assembly (MEA), reduce the overall power output from a SPFC. Despite a large range of commercially available alloys, 316 stainless steel has traditionally been the alloy of choice for bipolar Plates. A number of alternative grades of stainless steel have been evaluated in terms of the electrical resistance of their surface oxide film. This showed that ohmic losses exhibited in fuel cell performance varied depending on the elemental composition of the stainless steel alloy. Three stainless steel alloys, 310, 316 and 904L, were chosen as candidate bipolar Plate Materials. Increased polarisation was observed in the order 904L
John A Turner - One of the best experts on this subject based on the ideXlab platform.
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Characterization and performance of UNS S63019 (21-4N) as bipolar Plate Material in a simulated polymer electrolyte membrane fuel cell environment
Journal of Power Sources, 2011Co-Authors: Andrew G. Howell, Heli Wang, Scott W. Cowley, John A TurnerAbstract:The austenitic stainless steel UNS S63019 was evaluated regarding its potential as bipolar Plate Material in a polymer electrolyte membrane fuel cell (PEMFC) environment. Segregated grains of niobium carbide (NbCx) were identified in polished cross-sections of the alloy, offering a possible pathway for enhanced electrical conductivity through the passive surface oxide. Additionally, the alloy was tested for corrosion resistance in a simulated PEMFC environment. It was considered that perhaps the elevated nitrogen concentration in the alloy would provide some benefit for corrosion resistance. Results for interfacial contact resistance (ICR) testing of the air-formed surface film on UNS S63019 showed decreased electrical conductivity as compared to UNS S30400. Niobium carbide particles did not improve film conductivity due to a non-conductive niobium oxide layer that formed on the surface. Corrosion resistance of the alloy was also poor as compared with UNS S30400, demonstrating that elevated nitrogen concentration in the alloy was not adequate in itself to enhance corrosion resistance. Poor corrosion resistance was attributed primarily to high carbon content in the alloy which combined with a significant amount of chromium to form carbides.
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investigation of a duplex stainless steel as polymer electrolyte membrane fuel cell bipolar Plate Material
Journal of The Electrochemical Society, 2005Co-Authors: Heli Wang, Glen Teeter, John A TurnerAbstract:Duplex 2205 stainless steel was investigated in a simulated polymer electrolyte membrane fuel cell (PEMFC) environment; stable passive films formed quickly under these conditions. The interfacial contact resistance (ICR) values for 2205 steel with the air-formed film were identical to those for 349 and lower than those for AISI446 steel. The ICR values for the passive film formed in a simulated PEMFC anode environment were lower than those for the passive film formed in the cathode environment, but both were higher than those for air-formed film. X-ray photoelectron spectroscopy analysis revealed that the passive films were mainly Cr 2 O 3 while the air-formed film was composed of Fe-oxides and Cr 2 O 3 . An estimate of the thickness of the surface films was made.
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investigation of a duplex stainless steel as polymer electrolyte membrane fuel cell bipolar Plate Material
Journal of The Electrochemical Society, 2005Co-Authors: Heli Wang, Glen Teeter, John A TurnerAbstract:Duplex 2205 stainless steel was investigated in a simulated polymer electrolyte membrane fuel cell (PEMFC) environment; stable passive films formed quickly under these conditions. The interfacial contact resistance (ICR) values for 2205 steel with the air-formed film were identical to those for 349 and lower than those for AISI446 steel. The ICR values for the passive film formed in a simulated PEMFC anode environment were lower than those for the passive film formed in the cathode environment, but both were higher than those for air-formed film. X-ray photoelectron spectroscopy analysis revealed that the passive films were mainly Cr 2 O 3 while the air-formed film was composed of Fe-oxides and Cr 2 O 3 . An estimate of the thickness of the surface films was made.
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ferritic stainless steels as bipolar Plate Material for polymer electrolyte membrane fuel cells
Journal of Power Sources, 2004Co-Authors: Heli Wang, John A TurnerAbstract:Abstract Both interfacial contact resistance (ICR) measurements and electrochemical corrosion techniques were applied to ferritic stainless steels in a solution simulating the environment of a bipolar Plate in a polymer electrolyte membrane fuel cell (PEMFC). Stainless steel samples of AISI434, AISI436, AISI441, AISI444, and AISI446 were studied, and the results suggest that AISI446 could be considered as a candidate bipolar Plate Material. In both polymer electrolyte membrane fuel cell anode and cathode environments, AISI446 steel underwent passivation and the passive films were very stable. An increase in the ICR between the steel and the carbon backing Material due to the passive film formation was noted. The thickness of the passive film on AISI446 was estimated to be 2.6 nm for the film formed at −0.1 V in the simulated PEMFC anode environment and 3.0 nm for the film formed at 0.6 V in the simulated PEMFC cathode environment. Further improvement in the ICR will require some modification of the passive film, which is dominated by chromium oxide.
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stainless steel as bipolar Plate Material for polymer electrolyte membrane fuel cells
Journal of Power Sources, 2003Co-Authors: Heli Wang, Mary Ann Sweikart, John A TurnerAbstract:Abstract Due to their low cost, high strength, ease of machining and shaping into thin sheets, as well as their corrosion resistance, stainless steels are considered to be good candidates for bipolar Plate Materials for the polymer electrolyte membrane fuel cell (PEMFC). We have tested several stainless steels in simulated PEMFC environments for application as bipolar Plates. The results showed that the chromium content in the steel alloys has an important influence on the anodic behavior. The interfacial contact resistance of the carbon paper/stainless steel interface has been evaluated. Both tests show that 349™ is the best candidate for this application. When 349™ stainless steel was polarized in simulated PEMFC environments, it was found that stable passive films formed within 30 min. The interfacial contact resistance between the carbon paper and stainless steel increased due to the formation of the passive film. However, as soon as a stable passive film is formed, the interfacial contact resistance stabilized.
Junichi Kimura - One of the best experts on this subject based on the ideXlab platform.
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evidence for recycled Plate Material in pacific upper mantle unrelated to plumes
Geochimica et Cosmochimica Acta, 2009Co-Authors: Shiki Machida, Naoto Hirano, Junichi KimuraAbstract:Abstract We report Sr, Nd, and Pb isotopic data of young alkaline basalt lava from a new type of volcano (petit-spot) on the northwestern Pacific Plate. Petit-spot lavas show Dupal, or extremely EM-1-like, Sr–Nd–Pb isotopic compositions. The data cannot be explained by contamination of pelagic sediment, in spite of the prediction on the basis of geological observation. We thus consider that the geochemistry of petit-spot lava indicates the existence of recycled fertile Plate Materials, not only the Dupal isotopic signature, in the northern hemisphere Pacific upper mantle unrelated to one or more active plumes. In consideration of published experimental results for fertile Plate Materials, selective melting of recycled Material is a process critical in generating petit-spot lava. Moreover, the small volume of the volcano and low degree of melting in the mantle source needed to form strongly alkalic lavas suggest that petit-spot volcanism is originated from small-scale heterogeneities of recycled Material. This idea consistently explains the geochemistry and noble gas isotopic composition of petit-spot lava, and also suggests small-scale heterogeneity widespread in the upper mantle of the Pacific Ocean. Together with a revised view of upper mantle heterogeneity, we propose that gross upper mantle composition is controlled by abundances and scales of regions of recycled Material that correspond to differences in the relative position to the Pangea supercontinent, suggesting the link to the tectonic origin of the global scale heterogeneity.
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evidence for recycled Plate Material in pacific upper mantle unrelated to plumes
Geochimica et Cosmochimica Acta, 2009Co-Authors: Shiki Machida, Naoto Hirano, Junichi KimuraAbstract:Abstract We report Sr, Nd, and Pb isotopic data of young alkaline basalt lava from a new type of volcano (petit-spot) on the northwestern Pacific Plate. Petit-spot lavas show Dupal, or extremely EM-1-like, Sr–Nd–Pb isotopic compositions. The data cannot be explained by contamination of pelagic sediment, in spite of the prediction on the basis of geological observation. We thus consider that the geochemistry of petit-spot lava indicates the existence of recycled fertile Plate Materials, not only the Dupal isotopic signature, in the northern hemisphere Pacific upper mantle unrelated to one or more active plumes. In consideration of published experimental results for fertile Plate Materials, selective melting of recycled Material is a process critical in generating petit-spot lava. Moreover, the small volume of the volcano and low degree of melting in the mantle source needed to form strongly alkalic lavas suggest that petit-spot volcanism is originated from small-scale heterogeneities of recycled Material. This idea consistently explains the geochemistry and noble gas isotopic composition of petit-spot lava, and also suggests small-scale heterogeneity widespread in the upper mantle of the Pacific Ocean. Together with a revised view of upper mantle heterogeneity, we propose that gross upper mantle composition is controlled by abundances and scales of regions of recycled Material that correspond to differences in the relative position to the Pangea supercontinent, suggesting the link to the tectonic origin of the global scale heterogeneity.
D P Davies - One of the best experts on this subject based on the ideXlab platform.
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stainless steel as a bipolar Plate Material for solid polymer fuel cells
Journal of Power Sources, 2000Co-Authors: D P Davies, Paul Leonard Adcock, Mark Christopher Turpin, Stuart James RowenAbstract:Stainless steel bipolar Plates for the Solid Polymer Fuel Cell (SPFC) offer many advantages over conventional graphitic Materials. These include relative low cost, high strength, ease of manufacture and as they can be shaped into thin sheets, significant improvement in the power/volume ratio. However, interfacial ohmic losses across the metallic bipolar Plate and the Membrane Electrode Assembly (MEA), reduce the overall power output from a SPFC. Despite a large range of commercially available alloys, 316 stainless steel has traditionally been the alloy of choice for bipolar Plates. A number of alternative grades of stainless steel have been evaluated in terms of the electrical resistance of their surface oxide film. This showed that ohmic losses exhibited in fuel cell performance varied depending on the elemental composition of the stainless steel alloy. Three stainless steel alloys, 310, 316 and 904L, were chosen as candidate bipolar Plate Materials. Increased polarisation was observed in the order 904L<310<316. This was maintained throughout an ongoing endurance test, where these cells have been run for over 3000 h without significant performance degradation. This difference in polarisation behaviour was attributed to variation in thickness of the oxide film. Analysis has shown no deleterious effect on the surface of the bipolar Plate and no evidence of corrosion.
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Stainless steel as a bipolar Plate Material for solid polymer fuel cells
Journal of Power Sources, 2000Co-Authors: D P Davies, Paul Leonard Adcock, M. Turpin, Stuart James RowenAbstract:Stainless steel bipolar Plates for the Solid Polymer Fuel Cell (SPFC) offer many advantages over conventional graphitic Materials. These include relative low cost, high strength, ease of manufacture and as they can be shaped into thin sheets, significant improvement in the power/volume ratio. However, interfacial ohmic losses across the metallic bipolar Plate and the Membrane Electrode Assembly (MEA), reduce the overall power output from a SPFC. Despite a large range of commercially available alloys, 316 stainless steel has traditionally been the alloy of choice for bipolar Plates. A number of alternative grades of stainless steel have been evaluated in terms of the electrical resistance of their surface oxide film. This showed that ohmic losses exhibited in fuel cell performance varied depending on the elemental composition of the stainless steel alloy. Three stainless steel alloys, 310, 316 and 904L, were chosen as candidate bipolar Plate Materials. Increased polarisation was observed in the order 904L
Renato Zenobi - One of the best experts on this subject based on the ideXlab platform.
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Evidence for laser-induced redox reactions in matrix-assisted laser desorption/ionization between cationizing agents and target Plate Material: a study with polystyrene and trifluoroacetate salts
International Journal of Mass Spectrometry, 2017Co-Authors: Guido P. Zeegers, Robert F. Steinhoff, Steffen M. Weidner, Renato ZenobiAbstract:Abstract Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is often applied to assess the dispersity and the end groups of synthetic polymers through the addition of cationizing agents. Here we address how these cation adducts are formed using polystyrene (PS) as a model polymer. We analyzed PS by MALDI-MS with a 2-[(2E)-3-(4-tert-butylphenyl)-2-methylprop-2-enylidene]malononitrile (DCTB) as the matrix and a range of trifluoroacetate (TFA) salts as cationizing agents on a range of different target Plate Materials (copper, 1.4301 stainless steel, aluminum, Inconel 625, Ti90/Al6/V4 and chromium-, gold- and silver-Plated stainless steel). It was found that on a stainless steel substrate the metal cations Al+, Li+, Na+, Cu+ and Ag+ formed polystyrene adducts, whereas K+, Cs+, Ba2+, Cr3+, Pd2+, In3+, or their lower oxidation states, did not. For the copper and silver substrates, PS and DCTB adduct formation with cations liberated from these target Plate Materials was observed upon addition of a cationizing agent, which indicates the occurrence of redox reactions between the added TFA salts and the target Plate Material. Judging from their standard electrode potentials, these redox reactions would not normally occur, i.e., they require an additional energy input, strongly suggesting that the observed redox reactions are laser-induced. Furthermore, copper granules were found to successfully sequester PS from a tetrahydrofuran (THF) solution, consistent with the view complex formation with the copper target Plate can take place prior to the MALDI-MS measurement.
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Target Plate Material Influence on Fullerene-C_60 Laser Desorption/Ionization Efficiency
Journal of The American Society for Mass Spectrometry, 2016Co-Authors: Guido P. Zeegers, Barbara F. Günthardt, Renato ZenobiAbstract:Systematic laser desorption/ionization (LDI) experiments of fullerene-C_60 on a wide range of target Plate Materials were conducted to gain insight into the initial ion formation in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. The positive and negative ion signal intensities of precursor, fragment, and cluster ions were monitored, varying both the laser fluence (0–3.53 Jcm^−2) and the ion extraction delay time (0–950 ns). The resulting species-specific ion signal intensities are an indication for the ionization mechanisms that contribute to LDI and the time frames in which they operate, providing insight in the (MA)LDI primary ionization. An increasing electrical resistivity of the target Plate Material increases the fullerene-C_60 precursor and fragment anion signal intensity. Inconel 625 and Ti90/Al6/V4, both highly electrically resistive, provide the highest anion signal intensities, exceeding the cation signal intensity by a factor ~1.4 for the latter. We present a mechanism based on transient electrical field strength reduction to explain this trend. Fullerene-C_60 cluster anion formation is negligible, which could be due to the high extraction potential. Cluster cations, however, are readily formed, although for high laser fluences, the preferred channel is formation of precursor and fragment cations. Ion signal intensity depends greatly on the choice of substrate Material, and careful substrate selection could, therefore, allow for more sensitive (MA)LDI measurements. Graphical Abstract ᅟ
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Target Plate Material Influence on Fullerene-C60 Laser Desorption/Ionization Efficiency.
Journal of the American Society for Mass Spectrometry, 2016Co-Authors: Guido P. Zeegers, Barbara F. Günthardt, Renato ZenobiAbstract:Systematic laser desorption/ionization (LDI) experiments of fullerene-C60 on a wide range of target Plate Materials were conducted to gain insight into the initial ion formation in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. The positive and negative ion signal intensities of precursor, fragment, and cluster ions were monitored, varying both the laser fluence (0–3.53 Jcm−2) and the ion extraction delay time (0–950 ns). The resulting species-specific ion signal intensities are an indication for the ionization mechanisms that contribute to LDI and the time frames in which they operate, providing insight in the (MA)LDI primary ionization. An increasing electrical resistivity of the target Plate Material increases the fullerene-C60 precursor and fragment anion signal intensity. Inconel 625 and Ti90/Al6/V4, both highly electrically resistive, provide the highest anion signal intensities, exceeding the cation signal intensity by a factor ~1.4 for the latter. We present a mechanism based on transient electrical field strength reduction to explain this trend. Fullerene-C60 cluster anion formation is negligible, which could be due to the high extraction potential. Cluster cations, however, are readily formed, although for high laser fluences, the preferred channel is formation of precursor and fragment cations. Ion signal intensity depends greatly on the choice of substrate Material, and careful substrate selection could, therefore, allow for more sensitive (MA)LDI measurements.