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Letteratura scientifica selezionata sul tema "Cathode interaction"

Autore: Grafiati

Pubblicato: 3 maggio 2025

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Articoli di riviste sul tema "Cathode interaction"

Cayla, FranÇois, Pierre Freton e Jean-Jacques Gonzalez. "Arc/Cathode Interaction Model". IEEE Transactions on Plasma Science 36, n. 4 (agosto 2008): 1944–54. http://dx.doi.org/10.1109/tps.2008.927378.

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Emelyanov, O., A. Plotnikov e E. Feklistov. "Positive corona streamer interaction with metalized dielectric: Possible mechanism of cathode destruction". Physics of Plasmas 29, n. 6 (giugno 2022): 064501. http://dx.doi.org/10.1063/5.0093203.

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This paper examines the effect of pulsed positive point-to-plane corona discharge in millimeter air gaps on the surface of a metalized dielectric. A footprint method was applied to reveal the streamer–surface interaction with Al and Zn thin films (20–50 nm) as a sensitive indicator. A thin metal film-dielectric substrate system was destructed at relatively low typical average currents of 20–50 μA during exposure times of 2–200 s. Destruction occurred in local zones with a size of several μm2 per one discharge pulse, which is substantially lower than the conventional streamer size of several tens of micrometers. An offered model of electro-thermal heating of the cathode layer shows that the dielectric surface temperature can achieve 1000 K and more during the single current pulse of submicrosecond duration. The indicated mechanism is possibly responsible for the effects of the discharge plasma interaction with low heat conductivity cathodes, including biological objects. Intensive heating of the cathode layer should be considered when modeling the streamer–cathode interaction.

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Sharma, Vinit, Manoj K. Mahapatra, Sridevi Krishnan, Zachary Thatcher, Bryan D. Huey, P. Singh e R. Ramprasad. "Effects of moisture on (La, A)MnO3 (A = Ca, Sr, and Ba) solid oxide fuel cell cathodes: a first-principles and experimental study". Journal of Materials Chemistry A 4, n. 15 (2016): 5605–15. http://dx.doi.org/10.1039/c6ta00603e.

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In solid oxide fuel cells (SOFCs), cathode degradation in the presence of moisture is a major concern at higher temperatures. We provide a comprehensive picture of the interaction between moisture and (La, A)MnO₃ based SOFC cathodes.

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Anfinogentov, Vasilij, e Aleksandr Hramov. "Investigation of oscillations of electron beam with virtual cathode in vircator and virtod". Izvestiya VUZ. Applied Nonlinear Dynamics 7, n. 2-3 (1999): 33–55. http://dx.doi.org/10.18500/0869-6632-1999-7-2-33-55.

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Nonlinear dynamics of the electron beam with virtual cathode in the vacuum drift tube is investigated with the aid of nmumerical simulation. Deterministic nature of the complex virtual cathode oscillations is demonstrated. It is proved, that one of the mechanisms of the chaotic dynamics origin is connected with nonlinear interaction between forming structures in the eleciron beam (virtual cathodes). Inner structures in the beam are analyzed by the orthogonal decomposition by Karunen — Loeve method and the wavelet transform method. Effect of external delay feedback (virtod scheme) processes of structures formation in the electron beam with virtual cathode is analyzed, and it is shown, that feedback delay time variation allows controllmg charactenstlcs of high power microwave generation in vircator systems.

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Yang, Zhenzhen, Hongna Li, Na Li, Muhammad Fahad Sardar, Tingting Song, Hong Zhu, Xuan Xing e Changxiong Zhu. "Dynamics of a Bacterial Community in the Anode and Cathode of Microbial Fuel Cells under Sulfadiazine Pressure". International Journal of Environmental Research and Public Health 19, n. 10 (20 maggio 2022): 6253. http://dx.doi.org/10.3390/ijerph19106253.

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Microbial fuel cells (MFCs) could achieve the removal of antibiotics and generate power in the meantime, a process in which the bacterial community structure played a key role. Previous work has mainly focused on microbes in the anode, while their role in the cathode was seldomly mentioned. Thus, this study explored the bacterial community of both electrodes in MFCs under sulfadiazine (SDZ) pressure. The results showed that the addition of SDZ had a limited effect on the electrochemical performance, and the maximum output voltage was kept at 0.55 V. As the most abundant phylum, Proteobacteria played an important role in both the anode and cathode. Among them, Geobacter (40.30%) worked for power generation, while Xanthobacter (11.11%), Bradyrhizobium (9.04%), and Achromobacter (7.30%) functioned in SDZ removal. Actinobacteria mainly clustered in the cathode, in which Microbacterium (9.85%) was responsible for SDZ removal. Bacteroidetes, associated with the degradation of SDZ, showed no significant difference between the anode and cathode. Cathodic and part of anodic bacteria could remove SDZ efficiently in MFCs through synergistic interactions and produce metabolites for exoelectrogenic bacteria. The potential hosts of antibiotic resistance genes (ARGs) presented mainly at the anode, while cathodic bacteria might be responsible for ARGs reduction. This work elucidated the role of microorganisms and their synergistic interaction in MFCs and provided a reference to generate power and remove antibiotics using MFCs.

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Biswas, Saheli, Aniruddha P. Kulkarni, Aaron Seeber, Mark Greaves, Sarbjit Giddey e Sankar Bhattacharya. "Evaluation of novel ZnO–Ag cathode for CO2 electroreduction in solid oxide electrolyser". Journal of Solid State Electrochemistry 26, n. 3 (21 gennaio 2022): 695–707. http://dx.doi.org/10.1007/s10008-021-05103-9.

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AbstractCO2 and steam/CO2 electroreduction to CO and methane in solid oxide electrolytic cells (SOEC) has gained major attention in the past few years. This work evaluates, for the very first time, the performance of two different ZnO–Ag cathodes: one where ZnO nanopowder was mixed with Ag powder for preparing the cathode ink (ZnOmix–Ag cathode) and the other one where Ag cathode was infiltrated with a zinc nitrate solution (ZnOinf –Ag cathode). ZnOmix–Ag cathode had a better distribution of ZnO particles throughout the cathode, resulting in almost double CO generation while electrolysing both dry CO2 and H2/CO2 (4:1 v/v). A maximum overall CO2 conversion of 48% (in H2/CO2) at 1.7 V and 700 °C clearly indicated that as low as 5 wt% zinc loading is capable of CO2 electroreduction. It was further revealed that for ZnOinf –Ag cathode, most of CO generation took place through RWGS reaction, but for ZnOmix–Ag cathode, it was the synergistic effect of both RWGS reaction and CO2 electrolysis. Although ZnOinf –Ag cathode produced trace amount of methane at higher voltages, with ZnOmix–Ag cathode, there was absolutely no methane. This seems to be due to strong electronic interaction between Zn and Ag that might have suppressed the catalytic activity of the cathode towards methanation.

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Odrobina, Igor, e Mirko Černák. "Numerical simulation of streamer–cathode interaction". Journal of Applied Physics 78, n. 6 (15 settembre 1995): 3635–42. http://dx.doi.org/10.1063/1.359940.

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Anfinogentov, Vasilij. "Chaotic oscillation in the electron beam with virtual cathode". Izvestiya VUZ. Applied Nonlinear Dynamics 2, n. 3 (3 marzo 1994): 69–83. https://doi.org/10.18500/0869-6632-1994-2-5-69-83.

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Nonlinear oscillations of the electron beam with virtual cathode in the Pierce diode are studied by numerical simulation (PIC method). Different dynamical states including chaotic oscillations of the electron beam are recognized. Quantatively (correlation dimension and greatest Lapunov exponent) and qualitatively (autocorrelation function and unstable periodic orbits) characteristics of chaotic oscillations are obtained. Physical processes in the diode are investigated and it was shown that the second region reflecting the electrons may appear in the beam. This region was called the secondary virtual cathode. It was discovered that one mechanism of beam chaotic behavior appearence was connected with the nonlinear interaction between the virtual cathodes.

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Pereira, Rhyz, Anthony Ruffino, Stefan Masiuk, Neal A. Cardoza, Hussein Badr, Michel W. Barsoum, Jonathan Spanier e Vibha Kalra. "In-Operando Raman Study on the Use of 2D and Suboxide Titanium Host Materials for Lithium-Sulfur Batteries". ECS Meeting Abstracts MA2023-01, n. 1 (28 agosto 2023): 388. http://dx.doi.org/10.1149/ma2023-011388mtgabs.

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While Lithium-Sulfur (Li-S) batteries have promised high capacities and low-cost material inputs, their potential has yet to be realized due to inherent issues with sulfur cathodes. In particular the polysulfide shuttle effect and sulfur’s intrinsic insulating properties stand in the way of a commercial battery, the demands of which include high sulfur loading and high cycling stability. Engineering the sulfur cathode, via the use of promising new materials has been an avenue of research pursued in the hopes of mitigating the shuttle effect via polysulfide entrapment and introducing more conductive materials. Of particular interest have been titanium oxide based materials which have shown polysulfide adsorption capabilities. However, the most common titanium oxide, anatase titanium (IV) oxide (TiO2) acts as an insulator, limiting its use in high sulfur loading batteries. Therefore, the use of more conductive titanium oxide materials is an attractive avenue of research. A previously reported freestanding titanium suboxide (TiO) carbon nanofiber cathode demonstrated excellent capacities (~790 mAh/g, ~2 mg/cm2). A rare lepidocrocite phase has also been observed via Raman spectroscopy in a newly discovered titanium carbide derived titanium oxide nanofilament (1D-NF). This material demonstrates properties that makes it attractive as a sulfur host material, having a high surface area of ~1700 m2/g, improved polysulfide reduction kinetics via the formation of polythionates, and polysulfide-cathode host interactions. The inclusion of these nanofilaments in sulfur cathodes yields capacities of ~800 mAh/g with ~1 mg/cm2 sulfur loading. The proposed mechanism via which these titanium oxide based materials function has never been investigated in-operando, and herein we conduct an in-operando Raman study to understand the behavior of these materials. Principally we will investigate the Eg band whose vibration can be moderated by the interaction of terminal sulfur atoms acting as Lewis bases and titanium atoms acting as Lewis acids, due to their vacant valance electrons. This interaction has been observed via postmortem XPS. The use of in-operando Raman allows us to uniquely observe transient behavior of the host material as well as the impact of crystal structure on polysulfide host interactions.

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Anfinogentov, Vasilij, e Aleksandr Hramov. "Influence of distributed feedback on chaotic virtual cathode oscillation". Izvestiya VUZ. Applied Nonlinear Dynamics 6, n. 1 (1998): 93–107. http://dx.doi.org/10.18500/0869-6632-1998-6-1-93-107.

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Complex dynamics of clectron beam with virtual cathode and distributed feedback is considered with the aid of numerical simulation. Characteristics of virtual cathode complex dynamics is investigated. For the system with connection through electron beam formation of the different types of autostructures is considered. It is proved, that complications of virtual cathode oscillation are connected with an increase of interaction between structures. For е system with connection through clectromagnetic fields (vircator — BWO) structures formation processes are investigated. It is demonstrated, that second structurc suppression by the interaction of virtual cathode with backwave fields makes possiblc controlling of output radiation characteristics.

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Più fonti

Tesi sul tema "Cathode interaction"

Nielsen, Torbjörn. "Electric arc-contact interaction in high current gasblast circuit breakers". Licentiate thesis, KTH, Mechanics, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1275.

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Cayla, François. "Modélisation de l'interaction entre un arc électrique et une cathode". Toulouse 3, 2008. http://www.theses.fr/2008TOU30033.

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Ce travail est relatif à l'étude et à la mise en place d'un modèle décrivant l'interaction entre un plasma thermique d'argon à la pression atmosphérique et une cathode en tungstène. Après une étude bibliographique sur les différents modèles décrivant la zone d'interaction, la théorie proposée par Benilov a été retenue comme base de nos développements. Dans une seconde partie, le modèle d'interaction arc/cathode est amélioré notamment par la prise en compte de l'émission secondaire. Le modèle est ensuite confronté et validé par des résultats expérimentaux issus de la littérature. Notre objectif était de coupler ce modèle d'interaction à une modélisation plus globale représentant aussi bien le passage du courant dans la cathode, la zone d'interaction (gaine et pré-gaine) que la colonne du plasma. Nous exposons les différents paramètres d'entrée possibles et justifions le choix de la densité de courant. Dans une dernière partie, le modèle d'interaction développé est couplé à un modèle bidimensionnel (2D) de plasma thermique en écoulement. Le passage du courant entre la cathode et le plasma est assuré grâce à une estimation de la conductivité électrique à deux températures dans la pré-gaine. L'influence de paramètres physiques (valeurs du coefficient d'émission secondaire, du travail de sortie,. . . ) et géométriques sur les grandeurs caractéristiques de la décharge (tension cathodique, champ de température dans le plasma,. . . ) dans une configuration d'arc libre avec une cathode cylindrique a pu être étudiée
This work deals on the study and the development of a model describing the interaction between argon thermal plasma and a tungsten cathode. A bibliographical study of the different models describing the interaction region is performed leading to the theory proposed by Benilov as base of our developments. In a second part, the arc/cathode interaction model has been realized taking into account secondary emission phenomenon. Then the model has been compared and validated by experimental results found in the literature. The final aim of this study was to couple the developed interaction model to a more global modeling describing the electrical conduction in the cathode bulk, the interaction region (sheath and pre-sheath) and the plasma column. We expose the rule of different possibilities for the input parameters and we justify the choice of the current density as main entry. In a last part, the interaction model has been coupled to a two dimensional coordinate system model of thermal plasma flow. The current continuity between cathode and plasma has been assumed using an estimation of the two temperature electrical conductivity in the pre-sheath. The influence of physical parameters (values of the secondary emission coefficient, work function. . . ) and geometrical ones on the characteristics of the discharge (cathode drop voltage, plasma temperature field. . . ) in a free burning arc configuration using cylindrical cathode has been realized showing the good ability and behavior of the model to a global thermal plasma description

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Monnoyer, Arthur. "Etude et optimisation du transfert d'énergie au sein d'une torche à plasma de forte puissance à cathode creuse". Electronic Thesis or Diss., Université de Toulouse (2023-....), 2024. http://www.theses.fr/2024TLSES258.

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Ces travaux, menés en collaboration avec la société Europlasma, sont consacrés à l'étude et à la prédiction de quelques phénomènes au sein des torches à plasma thermique de forte puissance (300 kW à 1 MW) à cathode creuse. Outre la géométrie particulière de la cathode, cette technologie de torche est composée d'une chambre d'injection en vortex du gaz plasmagène et d'une bobine créant un champ magnétique extérieur permettant de déplacer le pied d'arc cathodique par force de Laplace, afin de réduire l'érosion de cette électrode. Dans un premier temps, nous mettons en place un modèle fluide à l'équilibre thermodynamique local permettant la description de la dynamique de l'arc au sein de la torche. Ce modèle prenant en compte la turbulence par un modèle de type k-epsilon Realizable, permet de prédire le positionnement axial du pied d'arc cathodique et sa vitesse de rotation. Afin de nous affranchir de la description des phénomènes de claquage ayant lieu au sein de l'anode, un modèle d'anode poreuse est utilisé. Cette approche permet une première caractérisation du jet de plasma en sortie de torche. Les approches de la littérature consistant à tronquer la géométrie en entrée d'anode pour caractériser les phénomènes dans l'électrode amont sont comparées avec notre modèle utilisant la géométrie complète. Un bon accord est obtenu en termes de la trajectoire du pied d'arc cathodique ce qui justifie ces approches. Une étude paramétrique est alors menée sur la géométrie tronquée. En particulier, l'influence du gaz plasmagène et de diverses configurations magnétiques de la bobine de champ sur la trajectoire du pied d'arc cathodique sont étudiées. L'usure des électrodes, et notamment de la cathode, est un problème majeur lors de l'utilisation de ce type de torche. Ainsi, en parallèle de l'étude de la dynamique de l'arc, nous avons cherché à caractériser les phénomènes conduisant à cette usure. Dans un premier temps, le champ de température au sein du matériau est caractérisé grâce à un modèle analytique. Cette étude nécessite de connaître les caractéristiques du dépôt de puissance sur la surface cathodique par le pied d'arc (puissance totale et rayon de la tâche d'accrochage). Ces caractéristiques sont obtenues à l'aide de diverses mesures expérimentales de la littérature. Le champ de température calculé dépend aussi de la vitesse de rotation du pied d'arc (qui peut être déterminée avec le modèle fluide) et du refroidissement mis en place. Ce calcul prédit que la température maximale atteinte dans le matériau ne dépasse pas la température de fusion, en contradiction avec l'existence expérimentale de l'usure. Ce résultat provient d'une description insuffisante de la zone d'interaction arc-cathode qui doit prendre en compte la présence de micro-spots cathodiques. Une part importante de ces travaux est donc dédiée à l'étude théorique de cette interaction, prenant en compte les déviations à l'état d'équilibre thermodynamique local, la physique de la gaine cathodique et la vaporisation du matériau. En nous basant sur les travaux de M.S. Benilov, nous proposons un modèle de spot cathodique sur une cathode non-réfractaire. Cette étude permet de lever la contradiction précédente et donne de bons ordres de grandeur du taux d'usure observé expérimentalement
This work, carried out in collaboration with the company Europlasma, is devoted to the study and prediction of some phenomena within high-power well-type cathode thermal plasma torches (300 kW to 1 MW). In addition to the particular geometry of the cathode, this torch technology is composed of a vortex injection chamber for the plasma gas and a coil creating an external magnetic field making it possible to move the cathode arc foot by Laplace force, in order to reduce the erosion of this electrode. First, we set up a fluid model with local thermodynamic equilibrium allowing the description of the dynamics of the arc within the torch. This model, taking into account turbulence using a k-epsilon Realizable type model, makes it possible to predict the axial positioning of the cathode arc base and its rotation speed. In order to free ourselves from the description of the breakdown phenomena taking place within the anode, a porous anode model is used. This approach allows a first characterization of the plasma jet at the torch exit. Literature approaches consisting of truncating the geometry at the anode inlet to characterize the phenomena in the upstream electrode are compared with our model using the complete geometry. A good agreement is obtained in terms of the trajectory of the cathode arc foot which justifies these approaches. A parametric study is then carried out on the truncated geometry. In particular, the influence of plasma gas and various magnetic configurations of the field coil on the trajectory of the cathode arc foot are studied. Erosion of the electrodes, and particularly the cathode, is a major issue when using this type of torch. Thus, in parallel with the study of the dynamics of the arc, we sought to characterize the phenomena leading to this erosion. First, the temperature field within the material is characterized using an analytical model. This study requires knowing the characteristics of the power deposition on the cathode surface by the arc foot (total power and radius of the arc foot). These characteristics are obtained using various experimental measurements from the literature. The calculated temperature field also depends on the rotation speed of the arc foot (which may be determined using the fluid model) and the electrode cooling. This calculation predicts that the maximum temperature reached in the material does not exceed the melting temperature, in contradiction with the experimental existence of erosion. This result comes from an insufficient description of the arc-cathode interaction zone which must take into account the presence of cathode micro-spots. A significant part of this work is therefore dedicated to the theoretical study of this interaction, taking into account deviations from the state of local thermodynamic equilibrium, the physics of the cathode sheath and the vaporization of the material. Based on the work of M.S. Benilov, we propose a model of a cathode spot on a non-refractory cathode. As a result, the previous contradiction disappears and the orders of magnitude of the calculated erosion rates are in good agreement with the experiment

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Le, Ludec Jean-Pierre. "Instrumentation et traitement du signal pour la caractérisation thermique et mécanique d'un four de tirage Czochralski sous champ magnétique : application à la croissance de GaAs". Grenoble 1, 1989. http://www.theses.fr/1989GRE10141.

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Une approche systematique de l'evolution des caracteristiques courant-tension et pression-tension, completee par une etude par spectroscopie d'emission et par la mesure de la densite electronique, nous a conduits a une interpretation fine de la decharge en cathode creuse de titane sous plasma d'argon. Une tension minimale de decharge fonction d'une pression optimale et d'un courant optimal de decharge, est mise en evidence, ces deux derniers parametres evoluant de facon proportionnelle. Nous montrons que l'efficacite maximale d'excitation et d'ionisation des electrons se produit a des pressions inversement proportionnelles aux classes d'energie electronique considerees. Nous mettons egalement en evidence une modification des caracteristiques de la decharge etroitement liee aux phases cristallographiques alpha et beta du titane. Ce phenomene semble etre associe a une variation du travail de sortie du titane a la transition de phase

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Pagaud, Francis. "Control and stability of magnetised plasma columns : plasma-cathode interactions and helicon plasma operation". Electronic Thesis or Diss., Lyon, École normale supérieure, 2024. http://www.theses.fr/2024ENSL0016.

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Le transport, les ondes et les instabilités sont des problématiques courantes des plasmas magnétisés, à l’origine de problèmes fondamentaux et de limites opératoires pour les plasmas de fusion, les accélérateurs de particules à plasma ou la propulsion plasma. Le contrôle des propriétés du plasma est souhaitable mais complexe. Ce doctorat vise à utiliser une cathode émissive comme nouveau paramètre de contrôle et à comprendre la stabilité du plasma hélicon. Le dispositif expérimental est une enceinte à vide cylindrique de 80 cm de long et 20 cm de diamètre, connecté à un tube source en verre de 11 cm de diamètre. L’argon est injecté en continu à 0,13 Pa et ionisé par une antenne radio-fréquence inductive de 1 kW enroulée autour du tube source. Un champ magnétique de 170 G à 340 G garantit une faible magnétisation. Une cathode chaude injecte un fort courant thermionique à l’autre extrémité de la colonne de plasma. Les mesures optiques de température de la cathode ont révélé un profil fortement inhomogène dû aux interactions plasma-cathode, et fut reproduit numériquement avec succès par un modèle thermique détaillé. Le régime opératoire prédit est en excellent accord avec les expériences. L’influence expérimentale de l’injection d’électrons sur les propriétés plasmas, et plus particulièrement le potentiel plasma, a été couplée à une approche analytique basée sur un modèle de plasma magnétisé. Un accord qualitatif entre les prédictions théoriques et le contrôle effectif du potentiel plasma a été trouvé. La perspective de l’utilisation d’une cathode émissive comme nouveau paramètre de contrôle ouvre la possibilité d’un réglage fin de la dynamique globale du plasma, ainsi que la mitigation du transport et des instabilités au sein du plasma. Des améliorations sont discutées en vue d’une prédiction quantitative accrue. Enfin, une source de plasma hélicon haute densité a été implémentée afin d’atteindre des taux d’ionisation importants et un couplage antenne-plasma optimal. Ce nouveau système a été caractérisé à l’aide de sondes et d’imagerie rapide. Des signatures typiques des plasmas hélicons ont été retrouvées telles que des transitions de mode E-H-W, une rupture de symétrie liée au champ magnétique et la propagation d’ondes whistler m = +1. En outre, des oscillations basse-fréquence telles que des oscillations H-W et W-W, et des instabilités coexistantes de Rayleigh-Taylor et Kelvin-Helmholtz ont été identifiées. Une forte instabilité multi-échelles à 1080 G a été également brièvement explorée. L’identification des mécanismes d’instabilité via le calcul des taux de croissance, la décomposition 2D-FT et POD ont permis de comprendre les mécanismes physiques à l’oeuvre
Radial transport, azimuthal waves and instabilities are common features in magnetised plasmas, causing major challenges for plasma propulsion, plasma wakefield particle acceleration or fusion devices. Plasma properties control is desirable yet complex. This PhD thesis follows two goals, one being the use of an emissive cathode as a new parameter control and the other being the fundamental understanding of the helicon plasma operational stability. Firstly, the role of the injection of electrons inside a magnetised plasma column has been studied experimentally and numerically. The experimental set-up is a 80 cm long and 20 cm diameter vacuum vessel connected to a 11 cm wide glass tube. The argon gas at a base pressure of 0.13 Pa is ionised by a 3-turns inductive radio-frequency antenna supplied at 1 kW. Magnetic field ranging from 170 G to 340 G, ensures a weak magnetisation of the plasma. A large tungsten hot cathode was placed at the end of the plasma column to inject an important thermionic current. Electrical and optical measurements of the cathode temperature revealed a highly inhomogeneous cathode temperature profile due to plasma–cathode interactions. A detailed thermal modelling solved numerically accurately reproduces the heterogeneous rise in temperature witnessed experimentally. The operating regime was predicted in excellent agreement with experimental results.The fine understanding of the emissive cathode behaviour in presence of a surrounding magnetised plasma permitted to explore its influence on the plasma properties, and especially the plasma potential. An analytical approach based on a two-fluids plasma model and anisotropic electrical conductivities, predicting plasma potential control and plasma rotation regulation as a function of thermionic emission, has been applied and compared to a wide experimental dataset of plasma properties. The works presented confront the role of cross-field ion transport to experimental radial plasma potential scans with a semi-quantitative agreement, highlighting a new major application of emissive cathodes.Finally, a state-of-the-art helicon plasma source has been implemented to produce higher ionization rates. This new system required a complete characterisation of plasma properties through electrostatic probes and high-speed camera imaging. It reproduced well-known helicon plasma features such as E-H-W mode transitions, bistability and hysteresis, chirality emerging from the external magnetic field direction and the propagation of m = +1 whistler waves. Besides, it displayed complex behaviours such as H-W and W-W oscillations, or coexisting low-frequency Kelvin-Helmholtz and Rayleigh-Taylor instabilities. A strong multiscale core instability at 1080 G was also briefly investigated. Wave-mode identification based on theoretical growth rates, 2DFT modal decomposition and POD has been conducted, unravelling the physical mechanisms at stake

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Zhao, Teng. "Development of new cathodic interlayers with nano-architectures for lithium-sulfur batteries". Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/275684.

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Issues with the dissolution and diffusion of polysulfides in liquid organic electrolytes hinder the advance of lithium–sulfur (Li-S) batteries for next generation energy storage. To trap and re-utilize the polysulfides, brush-like, zinc oxide (ZnO) nanowires based interlayers were prepared ex-situ using a wet chemistry method and were coupled with a sulfur/multi-walled carbon nanotube (S/MWCNT) composite cathode. The cell with this configuration showed a good cycle life at a high current rate ascribed to (a) a strong interaction between the polysulfides and ZnO nanowires grown on conductive substrates; (b) fast electron transfer and (c) an optimized ion diffusion path from a well-organized nanoarchitecture. A praline-like flexible interlayer consisting of titanium oxide (TiO2) nanoparticles and carbon (C) nanofiber was further prepared in-situ using an electrospinning method, which allows the chemical adsorption of polysulfides throughout a robust conductive film. A significant enhancement in cycle stability and rate capability was achieved by incorporating this interlayer with a composite cathode of S/MWCNT. These results herald a new approach to building functional interlayers by integrating metal oxides with conductive frameworks. The derivatives of the TiO2/C interlayer was synthesized by changing the precursor concentration and carbonization temperature. Finally, a dual-interlayer was fabricated by simply coating titanium nitride (TiN) nanoparticles onto an electro-spun carbon nanofiber mat, which was then sandwiched with a sulfur/assembled Ketjen Black (KB) composite cathode with an ultra-high sulfur loading. The conductive polar TiN nanoparticles not only have a strong chemical affinity to polysulfides through a specific sulfur-nitrogen bond but also improve the reaction kinetics of the cell by catalyzing the conversion of the long-chain polysulfides to lithium sulfide. Besides, carbon nanofiber mat ensures mechanical robustness to TiN layer and acts as a physical barrier to block polysulfides diffusion. The incorporation of dual interlayers with sulfur cathodes offers a commercially feasible approach to improving the performance of Li-S batteries.

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Kaufmann, Helena Teresa da Costa. "Advanced modeling of plasma-cathode interaction in vaccum and unipolar arcs". Doctoral thesis, 2019. http://hdl.handle.net/10400.13/2302.

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Este trabalho Ø dedicado modelaªo da interacªo plasma-cÆtodo em descargas de arco em vÆcuo e em descargas de arco unipolares. Pela primeira vez foi desenvolvido um modelo numØrico detalhado de manchas catdicas solitÆrias em descargas de arco em vÆcuo. O modelo leva em conta todos os mecanismosrelevantesdosfenmenosfsicosdemanchascatdicas: obombardeamento dasuperfciedocÆtodoporiıesprovenientesdeumplasma prØ-existente; avaporizaªo do material do cÆtodo na mancha, a ionizaªo deste material vaporizado e a interacªo do plasma produzido com o cÆtodo; desenvolvimento do efeito de Joule no interior do cÆtodo; fusªo do material do cÆtodo e movimento do metal fundido sob o efeito da pressªo exercida pelo plasma e da fora de Lorentz; a deformaªo da superfcie fundida do cÆtodo; a formaªo de crateras e jactos de metal fundido; a ejecªo de gotas. Os resultados da modelaªo permitem identicar as diferentes fases da vida de uma mancha solitÆria. A emissªo de electrıes da superfcie do cÆtodo e o transporte de calor por convecªo sªo os mecanismos dominantes de arrefecimento na mancha catdica, limitando deste modo a temperatura mÆxima possvel no cÆtodo. A formaªo de crateras na superfcie do cÆtodo ocorre sem explosıes, seguida da formaªo de um jacto de metal fundido e da ejecªo de uma gota. Os resultados da modelaªo sªo concordantes com estimativas efectuadas para diferentes mecanismos de erosªo do cÆtodo, com base nos dados experimentais relativos erosªo em cÆtodos de cobre de descargas de arco em vÆcuo. A fase inicial de uma descarga de arco unipolar em condiıes relevantes para a fusªo nuclear em reactores tokamak foi investigada no mbito do modelo detalhado de manchas catdicas solitÆrias em descargas de arco em vÆcuo. Mais concretamente, a interacªo de um uxo intenso de energia com uma placa de tungstØnio imersa num plasma de hØlio e a correspondente transferŒncia de corrente foi estudada em condiıes baseadas em experiŒncias laboratoriais. Uma vez que o arco Ø de natureza unipolar, a transferŒncia de corrente fora da mancha Ø tida em consideraªo no modelo utilizado e a variaªo da diferena de potencial entre o plasma e a placa Ø avaliada a partir da condiªo de corrente total nula transferida para a placa a cada instante. Os resultados da modelaªo revelam a formaªo de uma cratera, mas sem a formaªo de um jacto de metal fundido ou a ejecªo de uma gota. A modelaªo Ø realizada para diferentes condiıes e demonstra-se que Ø necessÆrio ter em consideraªo a limitaªo da corrente terminica de electrıes pela banha de carga de espao.
This work is dedicated to modeling of the plasma-cathode interaction in vacuum and in unipolar arcs. A detailed numerical model of individual cathode spots in vaccum arcs has been developed for the rst time. The model takes into account all the relevant mechanisms of the physics of cathode spots: the bombardment of the cathode surface by ions coming from a pre-existing plasma cloud; vaporization of the cathode material in the spot, its ionization, and the interaction of the produced plasma with the cathode; Joule heat generation in the cathode body; melting of the cathode and motion of the molten metal under the e⁄ect of the plasma pressure and the Lorentz force; the change in shape of the molten cathode surface; the formation of craters and liquid-metal jets; the detachment of droplets. The simulation results allow the identication of the di⁄erent phases of life of an individual spot. Electron emission cooling and convective heat transfer are dominant mechanisms of cooling in the spot, limiting the maximum temperature of the cathode. Craters are formed on the surface without explosions, followed by the the formation of a liquid-metal jet and the ejection of a droplet. The modeling results conform to estimates of di⁄erent mechanisms of cathode erosion derived from the experimental data on the net and ion erosion of copper cathodes in vacuum arcs. The initial stage of unipolar arcing in fusion-relevant conditions was investigated in the framework of the detailed model of cathode spots in vacuum arcs. In particular, the interaction of an intense heat ux with and current transfer to a tungsten metal plate immersed in a helium background plasma is studied in conditions based on experiments. Since the arc is unipolar, the model is supplemented with an account of current transfer outside the arc attachment and the potential di⁄erence between the plasma and the plate is evaluated from the condition of the net current transferred to the plate being zero at each moment. The simulation results reveal the formation of a crater, but no jet formation or droplet detachment. Simulations are performed for di⁄erent sets of conditions, and it is found that in order for the developed model to be applicable to real experimental situations, space-charge limited thermionic electron emission must be considered.

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Almeida, Pedro Jorge Gomes Camacho de. "Investigation of modes of current transfer to cathodes of glow and arc discharges". Doctoral thesis, 2011. http://hdl.handle.net/10400.13/1471.

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This work is dedicated to modelling of di⁄erent modes of current transfer to cathodes of glow discharges and to experimental investigation of formation of transient spots on thermionic arc cathodes. Multiple steady-state solutions in the theory of DC glow discharge have been found for the rst time. The modelling was performed in the framework of the basic model of glow discharges and also in the framework of a more detailed model. The basic model comprises equations of conservation of a single ion species and the electrons, transport equations for the ions and the electrons written in the local approximation, and the Poisson equation. The detailed model takes into account atomic and molecular ions, atomic excited states, excimers, and non-locality of electron transport and kinetic coe¢ cients. These multiple solutions describe modes with a normal spot as well as modes with patterns of several spots similar to those observed in experiments with microdischarges in xenon. It is shown that modes with more than one spot can, in principle, occur not only in xenon but also in other plasma-producing gases. Formation of transient spots on thermionic cathodes was studied in experiments with COST529 standard HID lamps. There is a generally good agreement between experiment and results of numerical modelling. A possibility of prevention of appearance of transient spots by means of a brief reduction of the arc current shortly after the initial current increase is proposed and justied. It is shown that the main mechanism of blackening of burners of HID lamps that accompanies appearance of transient cathode spots is evaporation of the cathode material and not sputtering.
Este trabalho Ø dedicado modelaªo de diferentes modos de transferŒncia de corrente aos cÆtodos de descargas luminescentes e investigaªo experimental da formaªo de manchas transitrias em cÆtodos terminicos de descargas de arco. Mœltiplas soluıes estacionÆrias existentes na teoria da descarga luminescente foram calculadas numericamente pela primeira vez. A modelaªo foi realizada no mbito do modelo bÆsico da descarga luminescente e no mbito de um modelo detalhado. O modelo bÆsico contØm equaıes de conservaªo de uma espØcie inica e dos electrıes, equaıes de transporte dos iıes e electrıes escritas na aproximaªo local e a equaªo de Poisson. O modelo detalhado leva em conta iıes atmicos e moleculares, estados excitados dos Ætomos, dmeros excitados e nªo-localidade dos coecientes de transporte e cinØticos dos electrıes. As mœltiplas soluıes descrevem modos com uma mancha normal e modos com padrıes de vÆrias manchas semelhantes aos observados nas experiŒncias com micro-descargas em xØnon. Demonstra-se que modos com mais que uma mancha podem, em princpio, ocorrer em descargas noutros gases que nªo o xØnon. A formaªo de manchas transitrias em cÆtodos terminicos foi estudada em experiŒncias com lmpadas HID padrªo, COST-529. Existe uma concordncia genØricamente boa entre os resultados experimentais e da modelaªo numØrica. Uma possibilidade de prevenªo do aparecimento de manchas transitrias atravØs da breve reduªo da corrente da descarga logo aps um salto na corrente Ø proposta e justicada. Demonstra-se que o principal mecanismo de escurecimento das lmpadas HID que acompanha a formaªo de manchas catdicas Ø a evaporaªo do material do cÆtodo.

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Capece, Angela Maria. "Plasma-Surface Interactions in Hollow Cathode Discharges for Electric Propulsion". Thesis, 2012. https://thesis.library.caltech.edu/7108/4/Capece_Thesis_ChapterBib.pdf.

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Electric thrusters generate high exhaust velocities and can achieve specific impulses in excess of 1000 s. The low thrust generation and high specific impulse make electric propulsion ideal for interplanetary missions, spacecraft station keeping, and orbit raising maneuvers. Consequently, these devices have been used on a variety of space missions including Deep Space 1, Dawn, and hundreds of commercial spacecraft in Earth orbit. In order to provide the required total impulses, thruster burn time can often exceed 10,000 hours, making thruster lifetime essential.

One of the main life-limiting components on ion engines is the hollow cathode, which serves as the electron source for ionization of the xenon propellant gas. Reactive contaminants such as oxygen can modify the cathode surface morphology and degrade the electron emission properties. Hollow cathodes that operate with reactive impurities in the propellant will experience higher operating temperatures, which increase evaporation of the emission materials and reduce cathode life. A deeper understanding of the mechanisms initiating cathode failure will improve thruster operation, increase lifetime, and ultimately reduce cost.

A significant amount of work has been done previously to understand the effects of oxygen poisoning on vacuum cathodes; however, the xenon plasma adds complexity, and its role during cathode poisoning is not completely understood. The work presented here represents the first attempt at understanding how oxygen impurities in the xenon discharge plasma alter the emitter surface and affect operation of a 4:1:1 BaO-CaO-Al₂O₃ hollow cathode.

A combination of experimentation and modeling was used to investigate how oxygen impurities in the discharge plasma alter the emitter surface and reduce the electron emission capability. The experimental effort involved operating a 4:1:1 hollow cathode at various conditions with oxygen impurities in the xenon flow. Since direct measurements of the emitter surface state cannot be obtained because of the cathode geometry and high particles fluxes, measurements of the emitter temperature using a two-color pyrometer were used to determine the oxygen surface coverage and characterize the rate processes that occur during poisoning.

A model describing the material transport in the plasma discharge was developed and is used to predict the barium and oxygen fluxes to the emitter surface during cathode operation by solving the species continuity and momentum equations. The dominant ionization process for molecular oxygen in the plasma gas is resonant charge exchange with xenon ions. Barium is effectively recycled in the plasma; however, BaO and O₂ are not. The model shows that the oxygen flux to the surface is not diffusion limited.

Experimental results indicate that the oxygen poisoning rate is slow and that the oxygen poisoning coverage on the emitter surface is less than 3%. A time-dependent model of the reaction kinetics of oxygen and barium at the tungsten surface was developed using the experimental results.

The experiments and kinetics model indicate that the dominant processes at the emitter surface are dissociative adsorption of O₂, sputtering of the O₂ precursor, and desorption of O. Ion sputtering of the weakly bound O₂ precursor state limits the poisoning rate and yields low oxygen coverage. Removal of chemisorbed atomic oxygen is dominated by thermal processes. Based on the low oxygen coverage and long poisoning transients, plasma cathodes appear to be able to withstand higher oxygen concentrations than vacuum cathodes.

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Guerrero, Vela Pedro Pablo. "Plasma Surface Interactions in LaB₆ Hollow Cathodes with Internal Xe Gas Discharge". Thesis, 2019. https://thesis.library.caltech.edu/11673/39/Guerrero_Pablo_2019.pdf.

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The ultimate goals of space vehicles are to move faster, further, and more reliably in the space environment. Electric propulsion (EP) has proven to be a necessary technology in the exploration of our solar system ever since its working principle was empirically tested in space in 1964. Thanks to the high exhaust velocities of ionized propellant gases, EP enables efficient utilization of the limited supply of propellant aboard spacecrafts. This technology has opened the possibility of long distance autonomous space missions.

EP devices require electron sources to ionize the propellant gas and to neutralize charges that are leaving the spacecraft. In modern EP thrusters, this is achieved by the use of hollow cathodes -- complex devices that employ low work function materials to emit electrons. Hollow cathodes using polycrystalline LaB₆ inserts are attractive candidates for long duration EP based space missions. However, the physics behind LaB₆ hollow cathode operation has not been studied in detail, which limits the possibility of their optimization. This work presents an integrated experimental and computational approach to investigate LaB₆ hollow cathode thermal behaviour and the interplay between LaB₆ insert surface chemistry and xenon plasma.

Our investigation of the thermal behaviour of LaB₆ cathodes led to the unexpected discovery of a thermal transient when a new insert is first used. Specifically, we observed that the cathode temperature decreases by approximately 300 degrees over 50 hours before reaching steady state. This finding suggests a beneficial dynamic evolution of the cathode's chemical state when it interacts with its own plasma. This evolution is intrinsic to cathode operation and can only be precisely understood when the multiphysic nature of the cathode is self-consistently simulated. Thus, we built a numerical platform capable of combining the plasma, thermal and chemical behavior of a discharging hollow cathode. Simulations incorporating different neutralization models, inelastic ion-surface interaction and heterogeneous chemical evolution led to two major conclusions. First, simulations predicted a significant reduction of the LaB₆ work function (0.42~eV) compared to previously reported baseline values, which is of paramount importance for EP thruster efficiency and operational lifetimes. Second, simulations suggested that the interaction between xenon low energy ions (< 50 eV) and the LaB₆ surface occurs following a two step neutralization mechanism. The predicted work function reduction was experimentally confirmed by photoemission spectroscopy. Furthermore, using a combination of crystallographic analysis, scanning electron microscopy and profilometry, we demonstrated that work function reduction is caused by the creation of a crystallographic texture at the LaB₆ surface upon interaction with Xe plasma. In addition, we postulated the existence of a work function enhancing mechanism of secondary importance, which can be explained by forced cationic termination of plasma exposed crystals.

Our results revealed the unexpected phenomenon of work function reduction upon plasma exposure of LaB₆. These findings suggest that LaB₆ hollow cathodes may outperform current technologies and become the component of choice in EP thrusters for future space missions.

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Libri sul tema "Cathode interaction"

J, Heberlein, e United States. National Aeronautics and Space Administration., a cura di. Arc-cathode interaction study: Final report for NASA contract NASA/NAG3-1332. Minneapolis, MN: High TemperatureLab, Dept. of Mechanical Engineering, University of Minnesota, 1992.

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Center, Lewis Research, a cura di. Investigation of beam-plasma interactions: Final report. Huntsville, Ala: University of Alabama in Huntsville, 1987.

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Center, Lewis Research, a cura di. Investigation of beam-plasma interactions: Final report. Huntsville, Ala: University of Alabama in Huntsville, 1987.

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Center, Lewis Research, a cura di. Investigation of beam-plasma interactions: Final report. Huntsville, Ala: University of Alabama in Huntsville, 1987.

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Estes, Robert D. Investigation of plasma contactors for use with orbiting wires [microform]: Semiannual report #2 for the period 1 July 1986 through 31 December 1986. Houston, Tex: National Aeronautics and Space Administration, Lyndon B. Johnson Space Center, 1987.

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Investigation of beam-plasma interactions: Final report. Huntsville, Ala: University of Alabama in Huntsville, 1987.

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Investigation of plasma contactors for use with orbiting wires: Final report for the period 1 January 1986 through 30 June 1987. Cambridge, Mass: Smithsonian Institution Astrophysical Observatory, 1987.

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Capitoli di libri sul tema "Cathode interaction"

Beilis, Isak. "Application of Cathode Spot Theory to Laser Metal Interaction and Laser Plasma Generation". In Plasma and Spot Phenomena in Electrical Arcs, 1027–66. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-44747-2_24.

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Oettinger, P. E., e I. Bursuc. "Emission Characteristics and Surface Phenomena of Laser Heated Thermionic Cathodes". In Laser Interaction and Related Plasma Phenomena, 307–14. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4615-7335-7_24.

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Moreno, C. M., G. Artola e J. M. Sanchez. "Interaction between Ti-6%Al-4%V Alloys and Hardmetals Coated by Cathodic-Arc Technology". In Functionally Graded Materials VIII, 353–58. Stafa: Trans Tech Publications Ltd., 2005. http://dx.doi.org/10.4028/0-87849-970-9.353.

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Hanlon, Robert T. "The Atom: discovery". In Block by Block: The Historical and Theoretical Foundations of Thermodynamics, 52–90. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198851547.003.0004.

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Many independent discoveries led to the discovery of the atom. Einstein’s explanation of Brownian motion provided proof that atoms exist. J.J. Thomson identified the cathode rays produced in Crookes‘ tube as electrons. Rutherford discovered that most atom mass is concentrated in a small central region. Bohr combined this with Planck’s quantized energy results from blackbody radiation studies to create the first physical model of the atom. Schrodinger, Heisenberg, and Born mathematically model the behavior of orbiting electrons, Heisenberg discovers uncertainty, Pauli defines exclusion, Dirac predicts spin, Chadwick discovers neutrons, and Fermi discovers weak interaction. Finally, Hahn, Meitner, and Strassmann discover nuclear fission, Yukawa discovers the strong interaction, the Stanford Linear Accelerator discovers the quark, and physicists capture the strong, weak, and electromagnetic fundamental interactions in the Standard Model.

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"Modelling interaction of metal halide plasmas with a thermionic cathode". In Light Sources 2004 Proceedings of the 10th International Symposium on the Science and Technology of Light Sources, 565–66. CRC Press, 2004. http://dx.doi.org/10.1201/9781482269178-207.

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Vempannan C., Kanish T. C., Thirumanikandan D. e Aswin B. "Electrochemical Micromachining Performance Optimization". In Advanced Manufacturing Techniques for Engineering and Engineered Materials, 20–41. IGI Global, 2022. http://dx.doi.org/10.4018/978-1-7998-9574-9.ch002.

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Micromachined components are finding application in a variety of fields such as medical, semiconductor, and aerospace. Electrochemical micromachining (ECMM) is a technology used to realize the micro components with enhanced features and functionality. This chapter reviews the impact of cathode profile on the machining rate and accuracy. An indigenous developed ECMM setup is used with special attachment of rotating electrode. The control parameters such as machining voltage, duty cycle, electrolyte temperature, and rotating RPM were considered on improving the output performance. The interaction between the input parameters and machining speed and overcut was studied. The input parameters considered are machining voltage, duty cycle, electrolyte concentration, and cathode tool rotation. There are various optimization processes considered to evaluate the working range of control factors for the machine on output performance. In this chapter, various multi-objective optimization techniques applied in optimization of ECMM process were reviewed.

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Yue, Jili, Chaoxiang Xie, Xingze Jia, Yixiao Li, Mengmeng Qian, Tinglu Song e Chunli Li. "Atomic Force Microscopy and its Applications in Secondary Batteries". In Advanced Characterization Technologies for Secondary Batteries, 75–96. BENTHAM SCIENCE PUBLISHERS, 2024. http://dx.doi.org/10.2174/9789815305425124010006.

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Atomic Force microscope (AFM) not only reveals the surface morphology of substances at the nanoscale and molecular level but also enables the measurement of extremely weak forces, which allows for the study of weak interactions between molecules. Moreover, the AFM possesses certain spatial resolution ability. As a valuable tool in secondary battery research, AFM could reveal the surface microscopic morphology of the electrode in real time through the interaction between atoms from the tip and the electrode surface. It offers nanoscale surface information of the electrode from both chemical and physical perspectives, thus establishing essential guidance for further modification of electrode materials and electrolytes. This chapter reviews the state-of-art application progress of AFM in the study of secondary batteries, including cathode materials, anode materials and solid electrolyte interface.

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Yildirim, Salih Taner. "Research on Strength, Alkali-Silica Reaction and Abrasion Resistance of Concrete with Cathode Ray Tube Glass Sand". In Sustainable Buildings - Interaction Between a Holistic Conceptual Act and Materials Properties. InTech, 2018. http://dx.doi.org/10.5772/intechopen.73873.

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Ceballos-Pérez, José, Luis Ordóñez-López e Juan Sierra-Grajeda. "Thermal analysis of a single-cell PEM-type fuel cell with a coil as flow field architecture and its impact on cathode water formation". In Innovative Applications in Sustainable Energy and Environment, 67–75. ECORFAN, 2024. https://doi.org/10.35429/h.2024.13.67.75.

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The thermal analysis of Proton Exchange Membrane Fuel Cells (PEMFC) is crucial for understanding how temperature impacts both electrochemical performance and water management, key aspects of their operation. This study focuses on evaluating the effect of thermal variations and tortuosity on liquid water formation in the cathode and its influence on overall efficiency. The thermal analysis considers the interaction between heat transfer, tortuosity due to porosity, and the presence of liquid water. To solve the governing equations of the system, the open-source software OpenFOAM, based on C++, is used with the Finite Volume Method (FVM). This approach allows for accurate modeling of thermal behavior and mass transport in the PEMFC. The study examines performance through polarization curves at three operational temperatures: 323, 328, and 333 K, combined with tortuosity values of 1.5 and 2.5. These variations help understand how tortuosity affects reactant and product transport, as well as water management and overall cell performance.

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WALTERS, J. R. "Cathodic-protection Interaction". In Corrosion, 10:129–10:135. Elsevier, 1994. http://dx.doi.org/10.1016/b978-0-08-052351-4.50086-8.

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Atti di convegni sul tema "Cathode interaction"

Ma, C., J. Li, Z. Duan, F. He e J. Ouyang. "Study on the interaction of pulsed micro-hollow cathode discharge plasma jet with target". In 2024 IEEE International Conference on Plasma Science (ICOPS), 1. IEEE, 2024. http://dx.doi.org/10.1109/icops58192.2024.10626486.

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Kramer, Patrick, Fritz Friedersdorf e Matthew Merrill. "Segmented Multi Electrode Sensor for Investigation of Environment-assisted Cracking under Dynamic Atmospheric Conditions". In CORROSION 2017, 1–11. NACE International, 2017. https://doi.org/10.5006/c2017-08946.

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Abstract Environment-assisted cracking (EAC) of aluminum alloys in corrosive atmospheres is a significant maintenance and safety issue for aerospace and naval structures. EAC is influenced by the interaction of stress, environment, and alloy microstructure. Atmospheric environmental conditions and corrosion kinetics are dynamic due to diurnal cycles and changing operating conditions, where temperature, relative humidity, and surface contaminants interact to control thin film electrolyte properties. In the case of EAC and other localized corrosion processes, such as crevice corrosion, separation of the anode and cathode may occur due to variation of chemical composition, oxygen availability, and pH differences between the crack tip, mouth, and boldly exposed surfaces. Conventional electrochemical immersion testing is not well suited to study factors and interactions leading to EAC in corrosive atmospheres. The bulk electrolyte conditions for electrochemical immersion testing are vastly different than the thin film properties that are operative in atmospheric corrosion. For instance, the dynamic temporal and spatial variations and effects of cyclic relative humidity on the salt concentration, film thickness, and oxygen diffusion cannot be captured. Additionally, standard three electrode, immersion test cell measurements are not well suited to directly investigate the variation and distribution of cathodic and anodic currents that develop over a sample surface during EAC or crevice corrosion under atmospheric conditions. Thin film electrolyte electrochemical tests have been conducted using a segmented, multi electrode sensor with an artificial crevice to quantify the interaction of crack tip and crack mouth during cyclic atmospheric corrosion tests. These tests are compared to EAC measurements under similar conditions to inform a better understanding of the processes that are significant to EAC of aluminum alloys. Maximum crack velocities are observed when high cathodic current is measured at the tip of artificial crevices suggesting hydrogen embrittlement.

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Srinivasan, J., e R. G. Kelly. "Lab-Accelerated Simulation and Maximum Damage Size Estimation of Atmospheric Corrosion of Stainless Steel Compressor Blades Exposed to Marine Environments". In CORROSION 2015, 1–13. NACE International, 2015. https://doi.org/10.5006/c2015-05531.

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Abstract Stainless steel compressor blades coated with erosion-resistant coatings undergo abrasion during service, and on cooling, salt aerosol deliquescence leads to the formation of thin electrolyte films on the blade surface, resulting in a galvanic system in the vicinity of the damage due to the coating being usually nobler than the substrate. Corrosion resulting from this galvanic interaction is seen as pits, which can lead to fatigue cracks. This study focused on evaluating the localized corrosion damage observed on UNS S17400 stainless steel compressor blades removed from active service and developing an accelerated laboratory testing procedure that permits the rapid replication of similar damage. The accelerated exposure testing was effected by utilizing aggressive solution chemistry and ozone which acts as a surrogate for all oxidizers found in natural environments. Testing was initially carried out in a compact chamber in order to determine effective levels of these parameters in order to extend the experiments to modified standard lab-accelerated procedures in fog-exposure chambers. The ASTM G85 A2 acidified salt spray technique was modified to investigate the effects of cyclic corrosion testing on pristine samples and the nature and the extent of resulting corrosion morphology. Finally, the electrochemical separation of anode and cathode that results from the galvanic interaction was leveraged to extend a model to predict the maximum pit size that can develop on the stainless steel surface once the knowledge of the environmental conditions are known. The results from the model when compared to the pitting morphology are expected to help rationalize the pitting morphology observed on the blades removed from service as well as the samples tested under lab-accelerated conditions.

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Roy, Ajit K., Dennis L. Fleming e Beverly Y. Lum. "Galvanic Corrosion - Effect of Environmental and Experimental Variables". In CORROSION 1999, 1–8. NACE International, 1999. https://doi.org/10.5006/c1999-99465.

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Abstract Galvanic corrosion behavior of A 516 steel (UNS K01800) coupled to UNS N06022 and UNS R53400, respectively was evaluated in an acidic brine (pH ≈ 2.75) at 30°C, 60°C and 80°C using zero resistance ammeter method. A limited number of experiments were also performed in a neutral brine involving A 516 steel/UNS N06022 couple. The steady-state galvanic current and galvanic potential were measured as functions of anode-to-cathode (A/C) area ratio and electrode distance. Results indicate that the galvanic current was gradually reduced as the A/C area ratio was increased. No systematic trend on the effect of A/C area ratio on the galvanic potential was observed. Also, no significant effect of electrode distance on the galvanic current and galvanic potential was evident. In general, increased galvanic current was noticed with increasing temperature. The limited data obtained in the neutral brine indicate that the galvanic current was reduced in this environment, compared to that in the acidic brine. Optical microscopic examination was performed on all tested specimens to evaluate the extent of surface damage resulting from galvanic interaction. A 516 steel suffered from general corrosion and crevice corrosion in all environments tested. Very light crevice corrosion mark was observed with UNS N06022 and R53400 in the acidic brine at 60°C and 80°C. However, this mark appears to be a surface discoloration and no actual crevice was detected.

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Rajab, Ahmad Moustafa. "Cathodic Protection Design & Commissioning for Sheet Piles Using SACP Aluminum Anodes". In MECC 2023, 1–10. AMPP, 2023. https://doi.org/10.5006/mecc2023-19890.

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Abstract Cathodic protection can be applied to any metallic structure in contact with an electrolyte. In practice its main use is to protect steel structures buried in soil or immersed in water. The cathodic corrosion process is usually the polarization of all noble potential areas (cathodes) to the most active potential (anodes) on the metal surface and It cannot be used to prevent atmospheric corrosion. Structures commonly protected in offshore area are the exterior surfaces of pipelines, ships’ hulls, jetties, foundation piling, and steel sheet-piling and offshore platforms. One method cathodic protection may be achieved is by means of the sacrificial anodes systems which use the galvanic series of metals. Sacrificial anode systems have the advantage of being simple to install, independent of any source of electric power, suitable for localized protection, less liable to cause interaction on neighboring structures. The current density required to maintain the protection potential is very dependent on local conditions. Increased availability of oxygen at the surface of the metal will directly increase current density. Thus, current densities to structures in seawater are likely to vary continuously. The pH of the environment will also be important. The presence of coatings, marine fouling, and calcareous deposits will have a profound effect on current density. This paper will discuss the cathodic protection design, installation Procedures and commissioning of 2.4 Km of sheet piles with different lengths using 641 kg Aluminum anodes.

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Adey, Robert A., John Baynham e Robin Jacob. "Prediction of Interactions between FPSO and Subsea Cathodic Protection Systems". In CORROSION 2008, 1–10. NACE International, 2008. https://doi.org/10.5006/c2008-08546.

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Abstract Deepwater Oil & Gas developments consist of many more components designed to extract, transport and store the oil when compared with developments in shallower waters. Designing the cathodic protection [CP] systems to protect the individual components is problematic without an appreciation as to how CP systems fitted to the various components will interact with one another once the entire asset is commissioned. For a recent deep-water project, a computer modeling study was commissioned to provide information on the performance of the CP systems protecting each of the subsea structures and in particular the interaction currents flowing between them. The principal aim was to ensure that the impressed current CP (ICCP) system on the hull of the FPSO would be operated in such a manner as to reduce interaction with the sub sea sacrificial anode CP systems to the minimum possible throughout the operating life of the field and to develop an understanding of the probable behavior of CP systems on the key components (FPSO, Oil offloading lines & Buoy, Riser Structures, etc.) particularly in respect of sacrificial anode lives. In addition, a further aim was to provide a working tool for Operations that could be used to aid ICCP control beyond the design and construct phases, and to provide input to Risk Based Inspection and maintenance planning. The paper will describe the strategy and rationale behind the modeling studies and some of the lessons learned and the plans for validation and ongoing maintenance of the model as ROV and field data becomes available.

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Pynn, Calvin R., e Khalil Abed. "Compatibility & Interactions between Cathodic Protection and a Vapor Phase Corrosion Inhibitor". In CORROSION 2017, 1–9. NACE International, 2017. https://doi.org/10.5006/c2017-09232.

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Abstract The nature of the physical contact between the bottom plate of an above ground storage tank and the underlying foundation/soil varies considerably over the area of a tank bottom and from tank to tank. This may vary from direct electrolytic contact between the plate and moist underlying soil to void spaces between the plate and the soil due to floor buckling and/or soil settlement. Cathodic protection is a proven corrosion mitigation technique where the target metal surface is in contact with a conductive electrolyte such as moist soil, but it will not be effective in void spaces where there is no electrolyte contact with the tank floor. Consequently, there is increasing application of vapor phase corrosion inhibitor injection beneath tank bottoms to ensure corrosion is mitigated in the void spaces. The objective of this work was to evaluate the mutual compatibility and interactions between cathodic protection and a vapor phase corrosion inhibitor where applied together in a liquid-phase environment. The work comprised of laboratory experiments to quantitatively evaluate the effects of a particular amine carboxylate based inhibitor and cathodic protection, when applied individually and jointly on an oxygen concentration corrosion macro-cell in a salt water solution. The results indicate a beneficial synergistic effect between the particular inhibitor tested and cathodic protection, where the inhibitor enhances cathodic polarization to reduce cathodic protection current requirement, and cathodic protection reduction reaction appears to enhance the absorption & effectiveness of the inhibitor at the cathodic metal surface.

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Futch, David B., Davie Peguero, Casey Whalen e Stephen Barnett. "Composite Repairs and Cathodic Protection". In CONFERENCE 2022, 1–9. AMPP, 2022. https://doi.org/10.5006/c2022-17825.

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Abstract Composite repairs have been extensively used over the past twenty-plus years as a high-integrity repair technology for high pressure transmissions pipelines. Numerous industry test programs have increased the knowledge related to repair techniques, repair design, and quality control of installations. However, little work has been performed related to the interactions of cathodic protection and composite repairs. This paper reviews several approaches for determining if cathodic shielding may occur under a composite repair. Preventing cathodic shielding can be considered in two different phases. First, the coating (or composite repair) must disbond or fail creating a local environment below the coating. Secondly, the coating (or composite repair) must allow for the permeation of cathodic current to the pipe surface providing the corrosion protection. Current industry standards, such as ASME PCC-2, can address the first aspect by examining the results of the cathodic disbondment tests and quantifying the level of disbondment. The second aspect can be addressed through an innovative and comprehensive test program that investigates several commercially available composite repair systems and their interactions with cathodic protection. Multiple test methods were utilized to prove there remains a low probability of shielding for composites of typical thickness and operating environment.

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Swain, Geoffrey W., Jeffrey R. Tabar, Frank Miceli e Eldon R. Muller. "The Interaction between Immersed and above Water Cathodic Protection Systems for Reinforced Concrete in Seawater". In CORROSION 1995, 1–13. NACE International, 1995. https://doi.org/10.5006/c1995-95506.

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Abstract The criteria for cathodic protection of reinforced concrete in the submerged and atmospheric zones are discussed with respect to the design of a cathodic protection system for a seawater aquarium. Potential mapping and polarization data are presented to demonstrate the extent of protection and interaction derived from each system.

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Battocchi, Dante, Nicholas Richter, Scott Hayes, Maocheng Yan, Dennis E. Tallman e Gordon Bierwagen. "Electrochemical Study of the Galvanic Interaction between the Mg Rich Primer and Its Al Substrate". In CORROSION 2010, 1–8. NACE International, 2010. https://doi.org/10.5006/c2010-10157.

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The cathodic properties of magnesium rich primers were investigated. An insulating layer was placed between the magnesium primer and aluminum alloy to create a barrier and separate the cathodic and sacrificial modes of protection. This was also done with a chromate rich primer. The open circuit potential (OCP) results show that the insulating layer stopped the cathodic protection of the substrate and only the sacrificial properties would be displayed. The non-insulated sample showed a mixed potential lower than the alloy between that of magnesium and the aluminum alloy. This indicates that there is cathodic protection of the metal substrate.[1] Electrochemical Impedance Spectroscopy (EIS) showed the insulated sample and the blank control to have similar properties. The non-insulated sample had lower impedance than the other samples because the metal pigments allowed for electrolyte penetration but had superior corrosion protection. The phase angle shows the insulated and blank controls to have the same mechanism while the non-insulated sample shows a different mechanism. The chromated samples, insulated and non-insulated, both had similar properties to each other which is expected due to the leaching of the chromates from the primer.

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Rapporti di organizzazioni sul tema "Cathode interaction"

Hack, Harvey P., e Dana C. Lynn. Interaction of Ship and Dock Cathodic Protection Systems Predicted from Potential Measurements of a Seawall at Panama City, Florida. Fort Belvoir, VA: Defense Technical Information Center, giugno 1995. http://dx.doi.org/10.21236/ada297027.

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Thompson e Lawson. L51692 Multiple Pipelines in Right-of-Way - Improved Pipe-To-Soil Potential Survey Methods. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), ottobre 1993. http://dx.doi.org/10.55274/r0010161.

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Pipe-to-soil potential measurements are the primary means for monitoring the effectiveness of cathodic protection systems. All criteria for cathodic protection employ, in one form or another, a potential measurement of the pipe with respect to a reference electrode. This research project was undertaken to determine what portion of a pipe is sampled by an above-ground potential measurement. One important area that has not yet been investigated is what portion of a pipe is sampled during a potential survey of a pipeline in a right-of-way containing multiple pipelines directly bonded to each other. The overall objective of this project was to improve the ability to interpret close interval on- and off-potential surveys in rights-of-way containing multiple pipelines. The project objective was accomplished by completing the following specific task oriented goals: (1) to expand the previously developed computer model to include multiple pipelines in the right-of-way, (2) to predict interaction effects between two pipelines in the same right-of-way, (3) to extend modeling activities to more complex pipeline situations by modeling specific case studies, and (4) to provide field verification of the modeling activities.

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Bongsebandhu-phubhakdi, Saknan, e Anan Srikiatkhachorn. On-media axon branching and adhesion investigation of neurons as stimulated by modulated potentials on micro-patterned gold substrate. Faculty of Medicine, Chulalongkorn University, 2016. https://doi.org/10.58837/chula.res.2016.22.

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The main focus of this research paper is on-media axon branching and adhesion investigation of neurons as stimulated by modulated potentials on micro-patterned gold substrate. Due to the prolonged and inefficient procedures of nerve repair, it is essential that we effectively incorporate different parameters and techniques as well as investigate cell-cell and cell-substrate interactions to explore new boundaries. This could lead to more operational options for nerve regeneration. Initially, the behavior of cell growth is first observed. 3T3 and Neuro2A cells are grown according to specific protocols allowing the observations of appropriate parameters needed to optimize the cells' development and proliferation. After thorough examination, the two cell subjects will be grown on patterned and non-patterned gold-coated substrates. Previously, "Cathode Arc Sputtering" and "Magnetron Sputtering" techniques are used to coat gold particles on polystyrene substrates and distributions of the thin films are then analyzed. Different patterning techniques, such as "Stencil Patterning" and "Microcontact Printing" are then applied to create a number of patterns on the substrates. Furthermore, 3D patterns will be induced by electrical potentials to generate magnetic fields near neurons. Various structured patterns as well as the overall shapes of the magnetic fields are speculated to have different effects on neural behaviors. Thus, cell-substrate adhesion interactions, manipulation of neuronal growth and proliferation using electrical potentials will be explored on pure gold substrates in this research. Specifically, the ambition of this research is to contribute to the development of neuron circuits that will allow more efficient procedures for nerve repair. This research's greatest hope is not only to provide current developments with extensive data for further improvements, but also to comprehend better the constraints restraining the breakthroughs of novel technologies.

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Ruschau e Tossey. L52209 Application of Repair Coatings to Wet Surfaces. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), giugno 2004. http://dx.doi.org/10.55274/r0010377.

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The field application of pipeline repair and rehabilitation coatings can be greatly dependent upon the ambient conditions on the day of the scheduled repair. In some cases, such as the application of FBE at girth welds, temporary shelters can be built over the girth weld area to protect pipe from the elements. However, for the majority of pipeline applications, coatings must be applied to a pipe surface that is not optimized for coating application. Specifically, pipelines which are in service during the repair coating operation will be at the temperature of the product flowing through them regardless of the ambient temperature. This poses a very large problem when the temperature of the pipeline is below the dew point of the ambient air, because condensation will occur continuously on the pipe surface. The objective of this work was to determine the performance implications of applying pipeline repair coatings to wet or damp surfaces. Six liquid repair coatings were applied to steel substrates with varying degrees of surface wetness. Three coatings were standard epoxies; three were specially formulated for wet surface tolerance. The coatings were tested for cathodic disbondment resistance, mechanical strength, and how each coating interacts with water during curing. FTIR and DSC analysis of each coating when mixed and cured in wet conditions (water added to the mix) showed no evidence of water interacting with the coating and changing the chemical structure or the chemical properties. Thus it was concluded that the wet surface tolerant coatings, while manufacturers may claim that they were formulated to absorb and accommodate water, in reality just have a better ability to displace water than standard repair coatings.

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