Academic literature on the topic 'Cathodic polarisation'
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Journal articles on the topic "Cathodic polarisation"
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Arjmand, Farzin, and Annemie Adriaens. "Effect of cathodic polarisation on the corrosion behaviour of 316L stainless steel under static and dynamic conditions." Corrosion Reviews 33, no. 5 (September 1, 2015): 249–61. http://dx.doi.org/10.1515/corrrev-2015-0023.
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AbstractThe role of cathodic polarisation on the corrosion of 316L stainless steel was investigated under static and dynamic conditions. The results reveal that the applied flow regime during the cathodic polarisation process has a direct effect on the corrosion behaviour of steel. The cathodic polarisation of steel under static conditions increases the oxygen reduction rate and shifts the corrosion potential towards nobler potentials. Under dynamic conditions, depending on the regime of the applied fluid flow during cathodic and anodic polarisation, the oxygen reduction rate can increase, causing the corrosion potential of the cathodically polarised steel to shift towards more positive direction. On the contrary, the oxygen reduction rate can decrease and the corrosion potential of the cathodically polarised steel shifts towards more negative potentials.
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Leach, J. S. Llewelyn, B. R. Pearson, and A. Rahmat. "Cathodic Polarisation in Aqueous Solutions." Key Engineering Materials 20-28 (January 1991): 563–69. http://dx.doi.org/10.4028/www.scientific.net/kem.20-28.563.
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Shubina Helbert, Varvara, Andrei Nazarov, Flavien Vucko, Nicolas Larché, and Dominique Thierry. "Effect of Cathodic Polarisation Switch-Off on the Passivity and Stability to Crevice Corrosion of AISI 304L Stainless Steel." Materials 14, no. 11 (May 28, 2021): 2921. http://dx.doi.org/10.3390/ma14112921.
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The effects of cathodic polarisation switch-off on the passivation of AISI 304L stainless steel in air and its crevice corrosion susceptibility in 3.5 wt.% NaCl aqueous electrolyte were investigated. Scanning Kelvin probe (SKP) data showed that the oxide film is significantly destabilised and the rate of steel passivation in air is slowed down. Thermal desorption analysis (TDA) highlighted that hydrogen absorption is proportional to the applied cathodic current density. A special crevice corrosion set-up was designed to realise simultaneous reproducible monitoring of potential and galvanic current to study the impact of prior cathodic polarisation on crevice corrosion onset.
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Cox, B., Yin-Mei Wong, and C. W. F. Quon. "Cathodic polarisation of corroding Zircaloy-4." Journal of Nuclear Materials 223, no. 3 (June 1995): 321–26. http://dx.doi.org/10.1016/0022-3115(95)00045-3.
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Rathod, Nikita, Peter Slater, George Sergi, Gamini Seveviratne, and David Simpson. "A fresh look at depolarisation criteria for cathodic protection of steel reinforcement in concrete." MATEC Web of Conferences 289 (2019): 03011. http://dx.doi.org/10.1051/matecconf/201928903011.
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Criteria for the successful application of cathodic protection (CP) for steel reinforced concrete have been fixed for decades and form part of ISO EN12696. The most used criterion is the achievement of 100 mV depolarization over a period not exceeding 24 hours after discontinuation of the applied current. Although more empirical than theoretically based, the criterion has served the CP industry well. It does, however, exclude any systems that may not always achieve that level of depolarization but have been shown to offer adequate protection, and so there is a need to explore ways of assessing depolarisation data more effectively. On a fundamental level, non-linear polarisation, as described by the Butler Volmer equation, relates corrosion rate to polarisation for a given applied current density and shows that at low current densities, estimated corrosion rates can be shown to be still insignificant at less than 100 mV polarisations. This paper explores the use of non-linear polarisation as an additional supportive criterion based on the measured 24-hour depolarisation level for a known applied current density and tests its applicability in the laboratory and in the field. It speculates that a reducing apparent corrosion current density trend in combination with a depolarised potential moving in a more noble direction is likely to be a suitable alternative criterion, where 100 mV depolarisation is not achieved.
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Simonet, Jacques. "The Platinised Platinum Interface Under Cathodic Polarisation." Platinum Metals Review 50, no. 4 (October 1, 2006): 180–93. http://dx.doi.org/10.1595/147106706x152703.
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Fanigliulo, A., and B. Bozzini. "Damage to gold surfaces induced by cathodic polarisation." Corrosion Engineering, Science and Technology 38, no. 3 (September 2003): 228–34. http://dx.doi.org/10.1179/147842203770226979.
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Balčiūnaitė, Aldona, Kush K. Upadhyay, Kristina Radinović, Diogo M. F. Santos, M. F. Montemor, and Biljana Šljukić. "Steps towards highly-efficient water splitting and oxygen reduction using nanostructured β-Ni(OH)2." RSC Advances 12, no. 16 (2022): 10020–28. http://dx.doi.org/10.1039/d2ra00914e.
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β-Ni(OH)2 nanoplatelets produced via a hydrothermal method exhibit good performance as trifunctional electrocatalysts for the ORR, OER, and HER in alkaline media along with excellent stability under cathodic/anodic polarisation conditions.
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Mjwana, Phumlani, Philippe Refait, Babatunde A. Obadele, Marc Jeannin, and Peter Olubambi. "Electrochemical Study of Calcareous Deposit Formation in Simulated Soil Solution under Cathodic Protection." Key Engineering Materials 821 (September 2019): 307–12. http://dx.doi.org/10.4028/www.scientific.net/kem.821.307.
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Cathodic protection induces the formation of a calcareous layer has been shown to improve metal protection against corrosion by reducing the oxygen diffusion on the metal surface. The present study focuses on the electrochemical scaling induced by the application of cathodic polarisation. A combination of non-invasive in-situ electrochemical techniques and electrochemical impedance spectroscopy was used. Metal/electrolyte interface behaviour was studied using voltammetry to determine the controlling anodic and cathodic reactions. One-week long experiments were conducted. Applied potential –1.2 VSCE was shown to enable the formation of CaCO3 allotropes calcite and aragonite, and brucite due to increased interfacial pH which resulted in the formation of hydrogen at the electrode surface. Time constants from bode plots for applied potential –1.2 VSCE also illustrated the inhomogeneity of the calcareous layer. Modelling of polarisation curves illustrated a “passivation” phenomenon which resulted from formation of hydroxyl cations. This was further validated by bode plots with the added information on the diffusion reaction process. High frequency behaviour showed a steady increase in the electrolyte resistance which may be attributed to the formation of the calcareous layer. Evidence of the initial Mg-gel porous layer, which precedes the formation of brucite, was found.
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Cheruvathur, Sini Varghese, Joby Thomas Kakkassery, Vinod Raphael Palayoor, Binsi M. Paulson, and Ragi Kooliyat. "Electrochemically Synthesized Poly(2-Aminobenzenesulphonic Acid) – An Efficient Protection for Carbon Steel Corrosion." Oriental Journal of Chemistry 35, no. 2 (April 24, 2019): 678–83. http://dx.doi.org/10.13005/ojc/350223.
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The corrosion protection efficacy of electrochemically synthesized poly(2-aminobenzenesulphonic acid) (P2ABSA) on carbon steel in 1.0 M HCl was investigated by electrochemical impedance spectroscopy, Tafel polarisation, scanning electron microscopy (SEM) and FT-IR spectral studies. The polymeric coating was prepared on the steel surface using cyclic voltammetry. Investigations established that P2ABSA effectively prevent the metal dissolution in HCl medium. Polarisation studies revealed that this polymer hinder both anodic and cathodic process of corrosion appreciably. The structures of the chemically and electrochemically synthesised polymers were compared using IR spectroscopy. Morphology of the steel surface confirmed the intact response of P2ABSA on steel surface treated with HCl.
Dissertations / Theses on the topic "Cathodic polarisation"
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Zadi, Daza Louis. "Mécanismes physico-chimiques impliqués dans la formation et l’évolution à l’abandon d’un matériau sédimentaire innovant généré en milieu marin par polarisation cathodique." Electronic Thesis or Diss., La Rochelle, 2022. http://www.theses.fr/2022LAROS028.
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Ce travail de thèse porte sur un matériau (le Geocorail) formé par polarisation cathodique d’un treillis en acier disposé au sein d’un milieu sédimentaire marin. L’application de ce procédé est dédiée au renforcement des ouvrages côtiers dans la lutte contre le recul du trait de côte. L’objectif de cette étude est d’apporter des réponses relatives à l’influence des paramètres du procédé sur les propriétés physico-chimiques de ce matériau ainsi que l’évolution de celui-ci en condition d’abandon, c’est-à-dire lorsque la polarisation est arrêtée. Cette étude a été réalisée à travers une démarche expérimentale couplée avec des modèles numériques. Ces travaux ont été réalisés sur un matériau modèle formé en laboratoire et ont permis de mettre en évidence l’anisotropie de diffusion au sein de ce matériau dont l’épaisseur, la porosité et la masse volumique sont essentiellement contrôlées par la densité de courant et la durée de la polarisation. Ces deux derniers paramètres favorisent la formation de liant, constitué de brucite (Mg(OH)2) et d’aragonite (CaCO3), servant à l’agglomération du sédiment en place. La géométrie de ce sédiment est en outre un facteur primordial pour l’optimisation des propriétés du matériau. En ce qui concerne sa stabilité chimique en l’absence de polarisation, les analyses expérimentales et les modèles numériques ont révélé que l’aragonite se substitue à la brucite avec un rendement massique relativement faible, probablement lié à la forte diffusivité des matériaux analysés. La faible variation de la porosité et de la masse volumique (inférieur à 5% en 18 mois) rassure cependant de la stabilité du Geocorail dont les propriétés pourraient même s’améliorer avec le temps. Enfin, des modèles numériques de croissance et d’évolution de ce matériau à l’abandon ont été élaborés. Des voies d’amélioration ont également été proposées pour une meilleure prédiction de ces propriétés, voire la prédiction des propriétés mécaniquesThis PhD work focused on the study of a material (Geocorail) formed by cathodic polarization applied in a marine sedimentary environment and used for the reinforcement of coastal structures in the fight against coastline recession. The objective of this study is to provide answers relative to the influence of the process parameters on the physico-chemical properties of this material as well as the evolution of the material under abandonment conditions, i.e. when the polarization is stopped. This was achieved through an experimental approach coupled with numerical models. This work was carried out on a laboratory material and its diffusion anisotropy within this material, the thickness, porosity and density of which are essentially controlled by the applied current density and the polarization time. These two parameters promote the formation of a binder, consisting of brucite (Mg(OH)2) and aragonite (CaCO3), which serves to agglomerate the sediments in place. The geometry of this sediment is also a key factor in optimizing the properties of this material. With regard to its chemical stability in the absence of polarization, experimental analyses and numerical models revealed that brucite substitutes for aragonite with a relatively low mass yield, probably linked to the high diffusivity of the studied materials. The small variation in porosity and density (less than 5% in 18 months) however ensures the stability of the Geocorail, whose properties could even improve with time. Finally, numerical models of the growth and evolution in abandon condition were developed. Some ways of improvement were also proposed for a better prediction of these properties, and even for the mechanical characterization using numerical methods
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Vincent, Julia. "Biocalcification bactérienne couplée à la polarisation cathodique en milieu marin afin de consolider les ouvrages du littoral." Electronic Thesis or Diss., La Rochelle, 2022. http://www.theses.fr/2022LAROS030.
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Les bactéries marines biocalcifiantes induisent la précipitation du carbonate de calcium pouvant conduire à la formation de concrétions rocheuses. Des minéraux peuvent également précipiter et former des dépôts calcomagnésiens à la surface d’un métal placé sous polarisation cathodique dans l’eau de mer. Ce dépôt minéral, qu’il résulte d’un processus biologique ou électrochimique, peut faire office de ciment entre les sédiments conduisant à des structures résistantes qui pourraient être utilisées pour lutter contre l’érosion des côtes et protéger les ouvrages du littoral. L’objectif de ces travaux de thèse a donc été d’identifier des bactéries marines biocalcifiantes et d’évaluer leur potentiel biotechnologique dans la bioprécipitation de minéraux pour la formation d’agglomérats calcomagnésiens associés ou non à la polarisation cathodique. Nous avons montré pour la première fois que le dépôt calcomagnésien, formé électrochimiquement en milieu naturel, peut être colonisé par une grande diversité de microorganismes incluant des bactéries capables d’induire la précipitation du CaCO3. Nous avons pu isoler 14 souches bactériennes biocalcifiantes appartenant aux genres Pseudoalteromonas, Virgibacillus, Pseudidiomarina, Epibacterium, Planococcus et Bhargavaea. Aucune bactérie de ces 4 derniers genres n’avait auparavant été décrite comme biocalcifiante. A l’aide d’un nouveau dispositif expérimental, 10 des 14 bactéries biocalcifiantes ont formé des agglomérats sablo-calcaires en un mois grâce à leur métabolisme (uréase, anhydrase carbonique ou autres). La mise au point d’un autre montage expérimental associant polarisation cathodique et bactéries a permis de montrer qu’une densité de courant de -670 μA.cm-2 n’influence ni leur croissance ni leur production de CaCO3. Ces bactéries présentent donc un fort potentiel pour être utilisées en association avec la polarisation cathodique pour renforcer les digues et retarder l'érosion côtièreBiocalcifying marine bacteria induce the precipitation of calcium carbonate which can lead to the formation of rock concretions. Minerals can also precipitate and form calcareous deposits on the surface of a metal placed under cathodic polarisation in seawater. This mineral deposit, whether it results from a biological or electrochemical process, can act as a cement between the sediments leading to resistant structures that could be used to fight against coastal erosion and protect coastal structures. The objective of this work was therefore to identify biocalcifying marine bacteria and to evaluate their biotechnological potential in the bioprecipitation of minerals for the formation of calcareous agglomerates associated or not with cathodic polarisation. We showed for the first time that the calcareous deposit, formed electrochemically in a natural environment, can be colonised by a wide variety of microorganisms, including bacteria able to induce CaCO3 precipitation. We were able to isolate 14 biocalcifying bacterial strains belonging to the genera Pseudoalteromonas, Virgibacillus, Pseudidiomarina, Epibacterium, Planococcus and Bhargavaea. None bacterium of these latter 4 genera had previously been described as biocalcifying. Using a new experimental device, 10 of the 14 biocalcifying bacteria formed sand-calcareous agglomerates in one month thanks to their metabolism (urease, carbonic anhydrase or others). The development of another experimental setup associating cathodic polarisation and bacteria made it possible to show that a current density of -670 μA.cm-2 influenced neither their growth nor their production of CaCO3. These bacteria therefore have great potential to be used in combination with cathodic polarisation to strengthen dikes and delay coastal erosion
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Poloni, Alexandre. "Étude de la sensibilité à la fragilisation par l’hydrogène de deux alliages de titane, le T40 et le TA6V ELI, sous polarisation cathodique en eau de mer par une approche locale de la rupture." Thesis, La Rochelle, 2020. http://www.theses.fr/2020LAROS003.
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Les objectifs de cette étude sont de comprendre les mécanismes de pénétration de l’hydrogène dans le titane sous polarisation cathodique en milieu marin et d’en évaluer les risques afin de donner un certain nombre de recommandations pour l’ingénieur. Les alliages T40 monophasé α et TA6V ELI biphasé α/β ont été choisis afin d’interroger l’influence de chacune des phases (α et β) et de leur distribution sur les phénomènes de fragilisation par l’hydrogène. Pour différents potentiels cathodiques, les cinétiques d’absorption de l’hydrogène dans différents milieux et particulièrement en eau de mer artificielle ont été étudiées. Elles sont très comparables entre les deux types d’alliages bien que les mécanismes mis en jeu et les concentrations en hydrogène atteintes pour chacun soient différents. La localisation des hydrures influencée par la structure métallographique des alliages est questionnée. Celle-ci conditionne les évolutions des propriétés mécaniques étudiées au travers d’essais de traction pour différentes orientations de sollicitation, teneurs en hydrogène et rayons d’entaille. La modélisation par éléments finis de chacun des essais permet d’accéder à des critères locaux d’endommagement et de rupture (contrainte hydrostatique versus déformation plastique équivalente). L’ensemble des travaux nous a permis de proposer des abaques reliant les évolutions des propriétés mécaniques à la concentration en hydrogène. D’autre part, une comparaison des résultats des expériences en laboratoire avec ceux des essais par couplage galvanique avec des anodes sacrificielles en eau de mer naturelle nous a permis de valider un seuil de potentiel de couplage galvanique maximal utilisable de -1,1 V/ECS en eau de mer, dans le cadre des conditions d’étudeThis study aims at understanding the hydrogen absorption mechanisms in titanium under cathodic polarization in seawater and then to provide risk assessments for engineers. The single-phase T40 and the two-phase TA6V ELI alloys were employed to study the influence of α and β phases as well as their distribution on the hydrogen embrittlement mechanisms. Hydrogen absorption kinetics were studied for several cathodic potentials in artificial seawater, while other electrolytes were used to validate some hypothesis. These kinetics are observed to be similar between the two alloys despite the differences in the absorption mechanisms and the hydrogen concentration at saturation. Then, this work investigates the role of the metallographic structure on the localisation of hydrides. The evolutions of the mechanical properties were studied by tensile tests on various orientations of solicitation, hydrogen concentrations and notches. As a result, these properties are observed to depend on the hydrogen concentration and the hydrides location. Models by finite elements were also used to determine local mechanical criterions of internal damage and fracture in term of hydrostatic stress and equivalent plastic strain. It allowed us to establish an abacus linking the evolutions of the mechanical properties to the hydrogen concentration. Moreover, this work also results in the determination of a maximum threshold of the cathodic potential at -1,1 V/SCE by comparing the laboratory results with those of on-site galvanic coupling by sacrificial anodes in natural seawater
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Kirk, Thomas. "The polarisation of Protestants and Roman Catholics in rural northern Ireland : a case study of Glenravel Ward, County Antrim, 1956 to 1988." Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359055.
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Boehm, Émmanuelle. "Les nickelates A2MO4+ð, nouveaux matériaux de cathode pour piles à combustible SOFC moyenne température." Bordeaux 1, 2002. http://www.theses.fr/2002BOR1A001.
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En vue du développement des piles à combustible à électrolyte oxyde solide (SOFC), l'une des priorités actuelles est d'abaisser leur température de fonctionnement de 900 - 1000ʿC jusqu'à 650 - 700ʿC. Néanmoins, à ces températures, des problèmes surgissent et notamment l'accroissement des chutes ohmiques et surtensions au niveau des divers composants. Concernant la cathode, il semble indispensable d'améliorer sinon de trouver de nouveaux matériaux permettant une meilleure cinétique de réduction de l'oxygène à plus basse température. Dans ce contexte, une nouvelle famille de composés conducteurs mixtes (c'est-à-dire à la fois conducteurs électroniques et ioniques) a été recherchée et étudiée. Ceux-ci, formulés A2MO4+d (A = La, Pr, Nd, Ca et M = Ni, Cu), sont sur-stœchiométriques en oxygène. Après avoir été préparés et caractérisés d'un point de vue cristallographique et physico-chimique, leurs propriétés de transport et leurs propriétés électrocatalytiques ont été déterminées. Des mesures de résistance de polarisation ont été réalisées sur des demi-piles symétriques par impédance complexe (afin de se rapprocher de l'application), et la réactivité des matériaux avec les électrolytes classiques a été étudiée. L'ensemble des résultats obtenus a montré que cette famille de matériaux est prometteuse pour l'application cathode de pile à combustible SOFC.
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Boehm, Émmanuelle. "Les nickelates A2MO4+ð, nouveaux matériaux de cathode pour piles à combustible SOFC moyenne température." Bordeaux 1, 2002. http://www.theses.fr/2002BOR12561.
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En vue du développement des piles à combustible à électrolyte oxyde solide (SOFC), l'une des priorités actuelles est d'abaisser leur température de fonctionnement de 900 - 1000ʿC jusqu'à 650 - 700ʿC. Néanmoins, à ces températures, des problèmes surgissent et notamment l'accroissement des chutes ohmiques et surtensions au niveau des divers composants. Concernant la cathode, il semble indispensable d'améliorer sinon de trouver de nouveaux matériaux permettant une meilleure cinétique de réduction de l'oxygène à plus basse température. Dans ce contexte, une nouvelle famille de composés conducteurs mixtes (c'est-à-dire à la fois conducteurs électroniques et ioniques) a été recherchée et étudiée. Ceux-ci, formulés A2MO4+d (A = La, Pr, Nd, Ca et M = Ni, Cu), sont sur-stœchiométriques en oxygène. Après avoir été préparés et caractérisés d'un point de vue cristallographique et physico-chimique, leurs propriétés de transport et leurs propriétés électrocatalytiques ont été déterminées. Des mesures de résistance de polarisation ont été réalisées sur des demi-piles symétriques par impédance complexe (afin de se rapprocher de l'application), et la réactivité des matériaux avec les électrolytes classiques a été étudiée. L'ensemble des résultats obtenus a montré que cette famille de matériaux est prometteuse pour l'application cathode de pile à combustible SOFC.
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Marie, Bruno. "Étude d'une décharge en cathode creuse avec grilles de polarisation : influence sur l'énergie des électrons, application au contrôle des couleurs d'un laser helium-cadmium trichrome fonctionnant en pulvérisation cathodique." Paris 11, 1986. http://www.theses.fr/1986PA112343.
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Étude d'une décharge en cathode creuse dans laquelle deux grilles concentriques sont introduites. La présence des grilles a pour but d'entraver la décharge et de la faire fonctionner à une tension plus élevée que dans les cathodes creuses classiques. Cette décharge peut être traitée comme la superposition de plusieurs décharges qui s'influencent fortement. Application au cas d'un laser hélium-cadmium trichrome dans lequel la production de vapeur métallique est assurée par pulvérisation cathodique
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Marié, Bruno. "Etude d'une décharge en cathode creuse avec grilles de polarisation influence sur l'énergie des électrons, application au contrôle des couleurs d'un laser helium-cadmium trichrome fonctionnant en pulvérisation cathodique." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb37599455m.
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Dailly, Julian. "Synthèse et caractérisation de nouveaux matériaux de cathode pour piles à combustible à conduction protonique PCFC (Protonic Ceramic Fuel Cell)." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2008. http://tel.archives-ouvertes.fr/tel-00416109.
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Le développement de piles à combustibles capables de fonctionner à des températures intermédiaires de l'ordre de 400-600°C présente un grand intérêt tant du point de vue du vieillissement des matériaux que des différents éléments du système complet. Une des technologies envisagées est basée sur l'utilisation d'électrolyte céramique possédant une conduction protonique élevée (Protonic Ceramic Fuel Cell PCFC). A ce jour, un des problèmes principaux concerne les fortes surtensions observées au niveau de la cathode lors du passage d'un courant.Dans ce cadre, le but de nos recherche a été de concevoir de nouveaux matériaux de cathode pour pile PCFC présentant de bonnes propriétés de conduction mixte ionique et électronique ainsi qu'une activité catalytique élevée vis-à-vis de la réaction de réduction de l'oxygène, entre 400 et 600°C. Plusieurs matériaux à conduction mixte ont été synthétisés à l'ICMCB, notamment des perovskites et des oxydes de structure de type Ruddlesden-Popper (en particulier les oxydes A2MO4+). Des analyses thermogravimétriques ont été réalisées pour étudier la stabilité de ces phases sous air humide, ainsi qu'une éventuelle insertion d'eau dans la structure. Des demi-cellules symétriques ont été élaborées pour les caractérisations éléctrochimiques par spectroscopie d'impédance complexe et voltampérométrie (mesures de résistances spécifiques de surface, courbes de polarisation cathodique).
Les caractérisations physico-chimiques et électrochimiques ont permit de sélectionner les meilleurs composés et ont conduit à la réalisation de la première monocellule PCFC utilisant le matériau de cathode Pr2NiO4+. Des densités de puissance de 100 mW/cm² ont été mesurées pour une température de fonctionnement de 600°C.
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Boehm, Emmanuelle. "Les nickelates A2MO4+ð, nouveaux matériaux de cathode pour piles à combustible SOFC moyenne température." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2002. http://tel.archives-ouvertes.fr/tel-00640152.
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En vue du développement des piles à combustible à électrolyte oxyde solide (SOFC), l'une des priorités actuelles est d'abaisser leur température de fonctionnement de 900 - 1000ʿC jusqu'à 650 - 700ʿC. Néanmoins, à ces températures, des problèmes surgissent et notamment l'accroissement des chutes ohmiques et surtensions au niveau des divers composants. Concernant la cathode, il semble indispensable d'améliorer sinon de trouver de nouveaux matériaux permettant une meilleure cinétique de réduction de l'oxygène à plus basse température. Dans ce contexte, une nouvelle famille de composés conducteurs mixtes (c'est-à-dire à la fois conducteurs électroniques et ioniques) a été recherchée et étudiée. Ceux-ci, formulés A2MO4+d (A = La, Pr, Nd, Ca et M = Ni, Cu), sont sur-stœchiométriques en oxygène. Après avoir été préparés et caractérisés d'un point de vue cristallographique et physico-chimique, leurs propriétés de transport et leurs propriétés électrocatalytiques ont été déterminées. Des mesures de résistance de polarisation ont été réalisées sur des demi-piles symétriques par impédance complexe (afin de se rapprocher de l'application), et la réactivité des matériaux avec les électrolytes classiques a été étudiée. L'ensemble des résultats obtenus a montré que cette famille de matériaux est prometteuse pour l'application cathode de pile à combustible SOFC.
Books on the topic "Cathodic polarisation"
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Varis, Päivi. Corrosion fatigue of titanium in sea water under cathodic polarisation. Espoo [Finland]: Technical Research Centre of Finland, 1992.
Find full textBook chapters on the topic "Cathodic polarisation"
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Googan, Chris. "Current and polarisation." In Marine Corrosion and Cathodic Protection, 141–69. London: CRC Press, 2022. http://dx.doi.org/10.1201/9781003216070-7.
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Bsiesy, A. "Porous silicon luminescence under cathodic polarisation conditions." In Porous Silicon Science and Technology, 307–22. Berlin, Heidelberg: Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-662-03120-9_18.
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Wilson, Peter H. "Confessional polarisation? Protestant Union and Catholic League." In The Thirty Years War, 12–21. London: Macmillan Education UK, 2010. http://dx.doi.org/10.1007/978-1-137-06977-1_3.
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Kennedy, Liam. "Two Ulsters." In Ireland and Partition, 97–118. Liverpool University Press, 2021. http://dx.doi.org/10.3828/liverpool/9781949979879.003.0006.
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In a society riven by ethno-religious and ethno-national divisions, relative population numbers assume a vital significance. Northern Ireland exemplifies the politics of demography in extreme form. More than three decades ago the author published a short book, Two Ulsters, which advocated a more politically-sensitive repartition of Ireland along nationalist and unionist lines. The proposal was born of despair at the polarisation of Northern Irish society in the wake of the Hunger Strikes of the early 1980s and the continuing insurgency of the Provisional IRA. In this chapter he revisits the proposal, noting long-run partitionist tendencies within Irish society. A reconstructing of Catholic and Protestant numbers, and hence power balances at both regional and local level, forms the middle part of the study. The final section peers into possible futures for Northern Ireland by considering some alternative political scenarios, including the ‘end game’ of Irish unity. The conclusion reached is that ‘not unlike the weather most days in Ireland, the future seems far from settled’. Indeed, the future may well lie with those best adapted to living with constitutional uncertainty.
Conference papers on the topic "Cathodic polarisation"
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Ferrari, Jean Vicente. "Discussion of Oxygen Threshold Level for Corrosion Management in Seawater Injection Systems." In SPE International Oilfield Corrosion Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/205041-ms.
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Abstract Generally, in water injection systems, oxygen levels starting from around eight ppm are deoxygenated to below 50 ppm, following international standards' guidelines. This work aims to discuss the impact of such a magnitude value of oxygen contamination on steel corrosion in seawater injection systems by analysing theoretical polarisation curves and results from published works with different approaches. Corrosion models consider mass-transfer controlled diffusion of oxygen to predict the maximum steel corrosion rate, which depends on the oxygen limiting current, which in turn is strongly influenced by flow velocity. The effect of free chlorine on corrosion in seawater injection systems has also been considered and included in an oxygen equivalent parameter. In such systems, where oxygen reduction is the key cathodic reaction, the corrosion process may be under cathodic activation control, independent of flow at higher velocities or when erosion-corrosion begins. In this work, theoretical polarisation curves were constructed by using published oxygen and chlorine cathodic limiting currents (iLc) on carbon steel and a noble metal electrode, respectively. Aerated (200 ppb and 9000 ppb of oxygen) and deaerated conditions (50 ppb of oxygen) and the presence of 300 ppb of chlorine were applied to the assumed exchange current densities (io). Neutral (pH 7) and acid (pH 4) conditions (considering the presence of CO2) were also assumed to be at room temperature and pressure. Since the corrosion rate in lower oxygen concentrations (ppb order of magnitude) may result in corrosion rates of the same order of magnitude than in higher oxygen concentrations (ppm order of magnitude) when comparing and analysing results from experimental, semi-empirical or mechanistic approaches, it is necessary to weigh up the effects of both steel surface (bare or scaled/corrosion products) and flow. At oxygen concentrations below 200 ppb and under acid conditions, the contribution of H+ reduction on corrosion rate starts to be higher than oxygen reduction, mainly in the absence of chlorine.
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Seiersten, Marion, Tor Gunnar Eggen, Liv Lunde, and Trond Rogne. "Hydrogen Absorption in Cathodically Polarized Titanium Alloys." In ASME 2002 21st International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2002. http://dx.doi.org/10.1115/omae2002-28580.
Full textAbstract:
Cathodic polarisation may cause hydrogen absorption and embrittlement of titanium alloys. There is no need to protect titanium in seawater, but polarisation is inevitable when titanium components are connected to steel that is cathodically protected. The risk of hydrogen embrittlement of risers and other heavily loaded components rouse a need to quantify the amount of hydrogen that titanium alloys may absorb as a function of alloy composition, polarisation potential, temperature, cold working and time. The test program included Ti-3Al-2.5V and Ti-6Al-4V alloys that are candidate materials for risers. The hydrogen uptake was measured over a 3 years period in natural seawater. The results show that titanium absorbs hydrogen when it is polarised to potentials less than −0.8V vs. Ag/AgCl in seawater, but the absorption rate decreased with time. The maximum hydrogen loading measured after three years exposure at −1.04 V vs. Ag/AgCl was 150 ppm. A calcareous deposit built up on all surfaces and limited the hydrogen evolution and thereby the hydrogen uptake. Ti-3Al-2.5V alloys picked up less hydrogen than Ti-6Al-4V alloys, and palladium or ruthenium enhanced hydrogen uptake to some extent. Welding or cold working did not influence hydrogen uptake of the alloys included in the tests. Temperature had little effect, and thermal gradients in the titanium materials had no measurable influence. The effect of hydrogen on the mechanical properties of the alloys was not studied in detail in these experiments, but most specimens were tensioned C-rings with permanent strain. Neither of these developed cracks or other signs of embrittlement during the tests.
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Bahrami, Amir, Anais Bourgeon, and Mohamad Cheaitani. "Effects of Strain Rate and Microstructure on Fracture Toughness of Duplex Stainless Steels Under Hydrogen Charging Conditions." In ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-49131.
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Failures of ferritic-austenitic stainless steel due to hydrogen induced stress cracking (HISC) have been very costly and raised concerns regarding subsea system integrity, some of which remain unresolved. The susceptibility to HISC crack initiation shows a strong correlation with austenite spacing and tests performed on smooth samples have shown that coarse-grained microstructures, with large austenite spacing, such as in forgings, are more susceptible to HISC than fine grained structures, eg as in pipe [1]. In all reported failures, cracking has been independent of the presence of fabrication flaws, even though welds were typically present, and initiated at external stress concentrators, so the importance of flaws remains undetermined. There is no well established method for determining fracture toughness values applicable to flaws in duplex stainless steel in the presence of hydrogen and hence reliable data do not exist, leading to a lack of understanding of the criticality of flaws and whether fine austenite spacing provides any benefit in resistance to extension of flaws. This paper provides new data from fracture toughness tests conducted on duplex pipe and forging parent materials, to explore the effect of product type/ microstructure and strain rate on fracture toughness under active charging in seawater under cathodic polarisation. This is part of ongoing work aimed at the development of an engineering critical assessment (ECA) approach for assessing flaw tolerance under hydrogen charging conditions.
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Dodge, M. F., H. B. Dong, M. Milititsky, R. P. Barnett, and M. F. Gittos. "Environment-Induced Cracking in Weld Joints in Subsea Oil and Gas Systems: Part II." In ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/omae2013-10339.
Full textAbstract:
In subsea oil and gas systems, low-alloy steel (LAS) forgings need to be welded to leaner steels such as X and F-65. While the LAS needs to be post-weld heat treated (PWHT) to relieve stresses and temper the HAZ microstructure in order to avoid hydrogen cracking, the same heat cycle would, in general, result in the degradation of the properties of the leaner alloy. A buttering technique is, therefore, usually used so that the buttered LAS forging can be heat treated before the closure weld is carried out. In the case of clad components, nickel alloy filler materials such as Alloy 625 are commonly used for both buttering and closure welds. This is an issue for subsea structures protected from corrosion by cathodic polarisation (CP) using aluminium based anodes. Whilst CP has proven successful as a means of preventing corrosion of steel components within subsea structures, failures along the dissimilar metal interfaces have been observed. This is due to hydrogen evolution as a result of CP. To further our understanding on this issue, this paper focuses on the correlation between microstructures, obtained by changing material combinations and PWHT conditions, and the resistance to hydrogen assisted cracking. Slow strain rate single edge notched bend (SENB) tests were carried out on the interfaces between AISI alloy 8630 and Alloy 625 buttering, retrieved from subsea service and tested in 3.5% NaCl solution under an applied potential of −1100mVsce. Retrieved specimens were pre-charged with hydrogen and tested at 4°C and 80°C, approximately in-line with commissioning/shutdown and service temperatures, respectively. In addition to the retrieved specimens, a testing programme has been developed to explore the effect of PWHT time on the performance of 8630-Alloy 625 and F22-Alloy 625 interfaces. The microstructures most susceptible to hydrogen cracking in these systems have been assessed by examination of the SENB test specimens.
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Burheim, Odne S., Signe Kjelstrup, Jon G. Pharoah, Preben J. S. Vie, and Steffen Mo̸ller-Holst. "On the Measured PEMFC Anode and Cathode Reversible Heats." In ASME 2010 8th International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2010. http://dx.doi.org/10.1115/fuelcell2010-33035.
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A recently constructed 2D calorimeter was used to measure the work and the total heat production of a single PEM fuel cell that is operated on hydrogen and oxygen at 50 °C and 1 bar. The cells had different membranes and catalyst layers, but the same porous transport layer and micro-porous layer. In this paper the distribution of the reaction entropy between the anode and the cathode, also known as the Peltier heats, was determined. This was done by the use of the measured heat through the anode and the cathode polarisation plates, the measured cell resistance, the measured overpotential and a fuel cell thermal model. The results show that the reaction entropy is almost solely related to the cathode and that the Peltier heat of the anode is near zero.
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Vang, Jakob Rabjerg, So̸ren Juhl Andreasen, and So̸ren Knudsen Kær. "A Transient Fuel Cell Model to Simulate HTPEM Fuel Cell Impedance Spectra." In ASME 2011 9th International Conference on Fuel Cell Science, Engineering and Technology collocated with ASME 2011 5th International Conference on Energy Sustainability. ASMEDC, 2011. http://dx.doi.org/10.1115/fuelcell2011-54880.
Full textAbstract:
This paper presents a spatially resolved transient fuel cell model applied to the simulation of high temperature PEM fuel cell impedance spectra. The model is developed using a 2D finite volume method approach. The model is resolved along the channel and across the membrane. The model considers diffusion of cathode gas species in gas diffusion layers and catalyst layer, transport of protons in the membrane and the catalyst layers, and double layer capacitive effects in the catalyst layers. The model has been fitted simultaneously to a polarisation curve and to an impedance spectrum recorded in the laboratory. A simultaneous fit to both curves is not achieved. In order to investigate the effects of the fitting parameters on the simulation results, a parameter variation study is carried out. It is concluded that some of the fitting parameters assume values which are not realistic. In order to remedy this, phenomena neglected in this version of the model must be incorporated in future versions.