Siga este link para ver outros tipos de publicações sobre o tema: Solid electrode Interface.
Teses / dissertações sobre o tema "Solid electrode Interface"
Crie uma referência precisa em APA, MLA, Chicago, Harvard, e outros estilos
Veja os 50 melhores trabalhos (teses / dissertações) para estudos sobre o assunto "Solid electrode Interface".
Ao lado de cada fonte na lista de referências, há um botão "Adicionar à bibliografia". Clique e geraremos automaticamente a citação bibliográfica do trabalho escolhido no estilo de citação de que você precisa: APA, MLA, Harvard, Chicago, Vancouver, etc.
Você também pode baixar o texto completo da publicação científica em formato .pdf e ler o resumo do trabalho online se estiver presente nos metadados.
Veja as teses / dissertações das mais diversas áreas científicas e compile uma bibliografia correta.
1
Yada, Chihiro. "Studies on electrode/solid electrolyte interface of all-solid-state rechargeable lithium batteries". 京都大学 (Kyoto University), 2006. http://hdl.handle.net/2433/144024.
Texto completo da fonteResumo:
Kyoto University (京都大学)0048
新制・課程博士
博士(工学)
甲第12338号
工博第2667号
新制||工||1377(附属図書館)
24174
UT51-2006-J330
京都大学大学院工学研究科物質エネルギー化学専攻
(主査)教授 小久見 善八, 教授 江口 浩一, 教授 田中 功
学位規則第4条第1項該当
2
Foster, Simon Edward. "Routes to interfacial deposition of platinum microparticles in solid polymer fuel cells". Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/28053.
Texto completo da fonte
3
Yamate, Shigeki. "Studies on Effects of Solid Electrolyte Interface on Negative Electrode Properties for Lithium-ion Batteries". Kyoto University, 2017. http://hdl.handle.net/2433/225963.
Texto completo da fonte
4
Konno, Akio. "Novel Performance Enhancement Method by Mesoscale-Structure Control of Electrode-Electrolyte Interface in Solid Oxide Fuel Cells". 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/142566.
Texto completo da fonte
5
Obadero, Abayomi Samuel. "Intercalation dans les matériaux graphitiques". Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALY024.
Texto completo da fonteResumo:
Bien que l'humanité lutte contre le défi pressant des émissions de gaz à effet de serre, l'importance des solutions énergétiques durables devient de plus en plus évidente. Les batteries au lithium-ion, considérées comme une avenue prometteuse pour stockage d'énergie électrique, sont essentielles pour l'électronique intégrée, le transport électrique et la production irrégulière à partir de sources renouvelables telles que l'éolien, la géothermie et le solaire. Cependant, leur adoption généralisée dépend de deux facteurs critiques principaux tels que la non-disponibilité du lithium dans la croûte terrestre et sa difficulté d'extraction. De plus, batteries au lithium-ion doivent stocker plus d'énergie et se recharger rapidement. Peut-être que l'exigence de haute capacité des batteries au lithium-ion pourrait être satisfaite en étudiant composants clés du lithium-ion, en particulier les électrodes d'anode (négative) et cathode (positive). Dans ce cadre, l'étude des composés d'intercalation du graphite (GIC) émerge comme un domaine essentiel, offrant des perspectives pour améliorer capacité de l'électrode d'anode où le graphite est le matériau hôte, d'où le nom GIC.Essentiellement, le GIC, qui appartient aux matériaux stratifiés, implique l'insertion régulière d'atomes, d'ions ou de molécules invités entre les couches graphite. Dans le contexte du GIC, travaux théoriques et expérimentaux ont été réalisés dans le but de comprendre et de relever les défis des batteries au lithium-ion. Par exemple, chercheurs ont exploré l'utilisation d'autres métaux alcalins (AM) tels que le sodium (Na) et le potassium (K) en remplacement du lithium (Li). Cependant, premiers semblent avoir une capacité réduite, en particulier dans cas du sodium (Na), où le composé totalement sodié est connu pour ne pas former. De plus, alors que les matériaux entièrement lithiés du GIC-Li ont été bien étudiés et caractérisés, les phénomènes en régime de concentration diluée ou faible demeurent évasifs. De même que pour le lithium, peu ou pas d'informations sur le régime de concentration diluée sont connues pour le GIC-K. En fait, le potassium (K) a été signalé pour occuper les interstices du graphite de manière désordonnée sans aucune stœchiométrie établie entre le carbone et le potassium. De plus, dans ce régime, des questions telles que l'évolution de l'environnement local AM en fonction de concentration, la concentration en AM à laquelle le l'empilement de graphite pur (AB ou Bernal) passe à l'empilement totalement lithié (AA ou hexagonal) pendant la lithiation, le mécanisme qui entraîne l'intercalation, et bien d'autres questions restent ouvertes dans le domaine des composés d'intercalation du graphite de métal alcalin (AM-GIC).Par conséquent, dans ce mémoire de thèse, nous avons mené une étude numérique approfondie sur à la fois le GIC-Li et le GIC-K la phase dense aux phases diluées en utilisant le formalisme de la théorie de la fonctionnelle de la densité (DFT). L'objectif de ce travail est de comprendre l'intercalation des AM (Li, Na et K) dans le graphite avec un accent particulier sur le régime dilué. Bien que notre outil DFT ait révélé que peu de calculs pouvaient être effectués avec Na en raison de son coût computationnel élevé, nous nous sommes concentrés sur Li et K pour lesquels des comportements différents sont rapportés dans les expériences. Utilisant l'outil DFT, nous avons montré que l'interaction entre Li et K dans la galerie du graphite n'est pas simplement électrostatique comme on l'a supposé jusqu'à présent. De plus, dans le régime dilué, les AM déforment localement la feuille de graphite pour éviter une surcompression par les atomes de carbone. Cette déformation structurelle est différente dans le graphite AB et AA. Nous avons utilisé cette différence structurelle observée entre le graphite AB et AA pour étayer la transition de l'empilement AB à l'empilement AA lors de l'intercalation de Li sur base des calculs d'énergie totale de la DFTAs humanity grapples with the pressing challenge of greenhouse gas emissions, the significance of sustainable energy solutions becomes increasingly evident. Lithium-ion (Li-ion) batteries, hailed as a promising avenue for electricity energy storage,which is critical for embedded electronics, electric transportation, and irregular production from renewable sources such as wind, geothermal, solar. e.t.c. However, their widespread adoption hinges on two main critical factors such as the non-availability of Li in the Earth’s crust and its difficulty in extraction. Hence, its supply may lead to future conflicts. Apart from these, Li-ion batteries are required to store more energy, that is, have better capacity and also charge quickly. Perhaps, the high capacity requirement of Li-ion batteries could possibly be met by investigating into the key components of Li-ion, specifically the Anode (negative) and Cathode (positive) electrodes. These electrodes host the Li-ions that move in opposite direction to electric current during charge and discharge. Within this framework, the study of graphite intercalation compounds (GICs) emerges as a pivotal field, offering insights into enhancing the capacity of specifically the Anode electrode where graphite is the host material, hence the name GIC.Basically, GIC which belongs to layered materials, involves the regular insertion of guest atoms, ions, or molecule between the layers of graphite. In the context of GIC, both theoretical and experimental work have been carried out in a bid to understand and tackle the challenges faced with Li-ion batteries. For instance, researchers have tried to explore the use other Alkali Metals (AM) which are readily available such as Na, and K as substitutes for Li. However, the formers seems to have reduced capacity, particularly in the case Na, where fully Sodiated compound has been known not to form. Furthermore, while fully Lithiated materials of Li-GIC have been well studied and characterized, phenomena at dilute or low concentration regime remains elusive. Similar to the case of Li, little or no information about the dilute regime has been known for K-GIC. In fact, K has been reported to occupy graphite gallery in a disordered manner without any established stoichiometry between C and K. Furthermore in this regime, questions like (i) the local environment evolution of AM as a function of concentration, (ii) the AM content at which pristine graphite stacking (AB or Bernal) transit to the fully lithiated (AA or hexagonal) stacking during lithiation,(iii) the mechanism driving intercalation, and many more are still open questions in the field of Alkali Metal Graphite Intercalation Compound (AM-GIC).Therefore in this thesis manuscript, we conducted an extensive numerical study on both Li-GIC and K-GIC from the dense phase to dilute phases using the Density Functional Theory (DFT) formalism. The aim of this work is to understand the intercalation of AM (Li, Na, and K) into graphite with a particular emphasis on the dilute regime. Although with our DFT tool, we realized that not much calculations could be performed with Na due to its computational cost. Therefore, we focused on Li and K for which different behavior is reported in experiments. Hence pointing to different mechanisms at the atomic scale that we aim to capture with our approach. Using the DFT tool, we have shown that the interaction between Li and K in the graphite gallery is not merely electrostatic as assumed so far. Furthermore in the dilute regime, AM locally deforms the graphite sheet to avoid an over-compression by C atoms. This structural deformation is different in AB and AA graphite. We have used this observed structural difference between AB and AA graphite to substantiate the transition from AB to AA stacking during Li intercalation based on the total energy calculations from DFT
6
Tchakalov, Rossen. "Engineering and optimization of electrode/electrolyte interfaces to increase solid oxide fuel cell (SOFC) performances". Thesis, Université Paris sciences et lettres, 2021. http://www.theses.fr/2021UPSLM001.
Texto completo da fonteResumo:
Dans ce travail, nous avons établi un protocole de fabrication industrielle pour réaliser des cellules de piles à combustible avec interfaces électrode/électrolyte architecturées, ou planes. Nous avons démontré que pour deux types d'échantillons, différents par les matériaux, la microstructure, le nombre de couches et l'emplacement de l'architecture, l'architecture de l'interface électrode/électrolyte entraîne une augmentation très significative des performances. Les mesures de polarisation et l'EIS sont utilisées pour étudier les performances électrochimiques des cellules, ainsi que pour comparer les cellules architecturées et les cellules planes. Nous isolons l'influence de l'architecture sur les spectres d'impédance globaux en utilisant une méthode de comparaison innovante basée sur l'étude des écarts relatifs des parties de résistance dépendantes de la fréquence. Ainsi, l'architecture a une influence favorable sur les performances électrochimiques en améliorant les capacités catalytiques des électrodes ainsi que le transfert de charges (et en particulier le transfert d'ions) dans la cellule. L'architecture induit une augmentation de 60 % de la densité de puissance maximale pour les cellules de Type I et de 75 % pour les cellules de Type IIIn this work, we have established an industrial fabrication protocol for single fuel cells with either architectured or planar electrode/electrolyte interfaces. We have demonstrated that in two types of samples, differing in materials, microstructure, number of layers, and architecture location, the architecturation of the electrode/electrolyte interface results in a highly significant performance increase. Polarization measurements and EIS are used to study the electrochemical performances of the cells, to compare the architectured and planar ones. We isolate the influence of the architecturation on global impedance spectra by using an innovative comparison method based on the study of the relative gaps of the frequency-dependent resistance parts. Thus, the architecturation has a strongly favorable influence on the electrochemical performances by enhancing the catalytic capabilities of the electrodes as well as the charge transfer (and in particular the ion transfer) within the cell. The architecturation induces a 60 % increase of the maximum power density for the Type I cells and 75% for the Type II cells
7
Feng, Shi. "Elucidation of hydrogen oxidation kinetics on metal/proton conductor interface". Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/48941.
Texto completo da fonteResumo:
High temperature proton conducting perovskite oxides are very attractive materials for applications in electrochemical devices, such as solid oxide fuel cells (SOFCs) and hydrogen permeation membranes. A better understanding of the hydrogen oxidation mechanism over the metal/proton conductor interface, is critical for rational design to further enhance the performances of the applications. However, kinetic studies focused on the metal/proton system are limited, compared with the intensively studied metal/oxygen ion conductor system, e.g., Ni/YSZ (yttrium stabilized zirconia, Zr₁-ₓYₓO₂-δ). This work presents an elementary kinetic model developed to assess reaction pathway of hydrogen oxidation/reduction on metal/proton conductor interface. Individual rate expressions and overall hydrogen partial pressure dependencies of current density and polarization resistance were derived in different rate limiting cases. The model is testified by tailored experiments on Pt/BaZr₀.₁Ce₀.₇Y₀.₁Yb₀.₁O₃-δ (BZCYYb) interface using pattern electrodes. Comparison of electrochemical testing and the theoretical predictions indicates the dissociation of hydrogen is the rate-limiting step (RLS), instead of charge transfer, displaying behavior different from metal/oxygen ion conductor interfaces. The kinetic model presented in this thesis is validated by high quantitative agreement with experiments under various conditions. The discovery not only contributes to the fundamental understanding of the hydrogen oxidation kinetics over metal/proton conductors, but provides insights for rational design of hydrogen oxidation catalysts in a variety of electrochemical systems.
8
Guille, Emilie. "Approche coupl´ee exp´erience/th´eorie des interfaces ´electrode/´electrolyte dans les microbatteries au lithium : application au syst`eme LixPOyNz/Si". Thesis, Pau, 2014. http://www.theses.fr/2014PAUU3045/document.
Texto completo da fonteResumo:
Afin de pallier les problèmes de sécurité posés par l'emploi d'électrolytes liquides, des batteries incorporant des électrolytes solides ont été envisagées, conduisant à des dispositifs « tout solide » de type microbatterie au lithium. Dans le cas de ces systèmes, des études concernant les phénomènes aux interfaces restent à développer, afin de comprendre les processus limitants qui se déroulent à l'échelle atomique, similairement à la formation de la SEI (« Solid Electrolyte Interface »), bien connue dans le cas de l'utilisation d'électrolytes liquides. Dans ce type de problématiques, l'apport des méthodes de la chimie calculatoire, de part leur aspect prédictif et explicatif, est incontestable. Le présent travail de thèse, en prenant pour objet d'étude l'électrolyte solide LixPOyNz, se place dans ces problématiques, en proposant l'étude fondamentale de modèles d'interfaces électrode/électrolyte. L'électrolyte considéré étant un matériau amorphe, le premier verrou à lever consiste en la recherche d'un modèle de ce système, apte à simuler les propriétés électroniques de l'électrolyte réel, constituées par des données XPS cibles. Les calculs menés, visant à la modélisation des spectres XPS, ont permis tout à la fois de proposer un modèle de l'électrolyte et de mettre en lumière l'existence d'une coordinence des atomes d'azote non considérée jusqu'alors dans l'interprétation expérimentale des données XPS. La possible existence d'atomes d'azote monovalents au sein de l'électrolyte semble confirmée par des calculs vibrationnels, thermodynamiques et cinétiques complémentaires, tandis que ce résultat permet de réviser la vision communément admise de la structuration de l'électrolyte LixPOyNz et de la diffusion des ions Li+ au sein de celui-ci. Enfin, ce modèle structural de l'électrolyte a été employé à la simulation d'une interface électrode/électrolyte (LixPOyNz/Si). Une considération particulière a notamment été apportée à l'étude de l'adsorption du modèle à la surface et de la diffusion des ions lithium au sein de l'interfaceIn order to overcome the safety issues induced by the use of liquid electrolytes, Li-ion batteries involving solid electrolytes have been considered, leading to an ‘all-solid’ kind of devices, commonly called microbatteries. For such devices, studies on the limiting processes that take place at electrode/electrolyte interfaces need to be done, to understand the electrochemical phenomenons likely to occur at the atomic scale, similarly to the well-known SEI formation. In this goal, methods of computational chemistry can provide both explanatory and predictive breakthroughs. The present work takes part in those issues by intending a study of electrode/electrolyte interfaces, considering LixPOyNz as the solid electrolyte material. Owing to the amorphous structuration of this system, the first barrier to break consists in the search for a suitable model, able to reproduce its real XPS electronic properties. Modelling of XPS spectra has both lead to propose a model of the electrolyte and highlight the possible existence of a new coordinence for nitrogen atoms, up to now unconsidered experimentally. Complementary calculations of Raman spectra, thermodynamic and kinetic data tend to evidence this coordinence, leading to a refinement of the commonly considered diffusion scheme. Finally, this structural model has been used to simulate an electrode/electrolyte interface (LixPOyNz/Si), with the particular aim of studying its adsorption on the electrode and the Li-ion diffusion through the interface
9
Ciosek, Högström Katarzyna. "The Complex Nature of the Electrode/Electrolyte Interfaces in Li-ion Batteries : Towards Understanding the Role of Electrolytes and Additives Using Photoelectron Spectroscopy". Doctoral thesis, Uppsala universitet, Strukturkemi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-219336.
Texto completo da fonteResumo:
The stability of electrode/electrolyte interfaces in Li-ion batteries is crucial to the performance, lifetime and safety of the entire battery system. In this work, interface processes have been studied in LiFePO4/graphite Li-ion battery cells. The first part has focused on improving photoelectron spectroscopy (PES) methodology for making post-mortem battery analyses. Exposure of cycled electrodes to air was shown to influence the surface chemistry of the graphite. A combination of synchrotron and in-house PES has facilitated non-destructive interface depth profiling from the outermost surfaces into the electrode bulk. A better understanding of the chemistry taking place at the anode and cathode interfaces has been achieved. The solid electrolyte interphase (SEI) on a graphite anode was found to be thicker and more inhomogeneous than films formed on cathodes. Dynamic changes in the SEI on cycling and accumulation of lithium close to the carbon surface have been observed. Two electrolyte additives have also been studied: a film-forming additive propargyl methanesulfonate (PMS) and a flame retardant triphenyl phosphate (TPP). A detailed study was made at ambient and elevated temperature (21 and 60 °C) of interface aging for anodes and cathodes cycled with and without the PMS additive. PMS improved cell capacity retention at both temperatures. Higher SEI stability, relatively constant thickness and lower loss of cyclable lithium are suggested as the main reasons for better cell performance. PMS was also shown to influence the chemical composition on the cathode surface. The TPP flame retardant was shown to be unsuitable for high power applications. Low TPP concentrations had only a minor impact on electrolyte flammability, while larger amounts led to a significant increase in cell polarization. TPP was also shown to influence the interface chemistry at both electrodes. Although the additives studied here may not be the final solution for improved lifetime and safety of commercial batteries, increased understanding has been achieved of the degradation mechanisms in Li-ion cells. A better understanding of interface processes is of vital importance for the future development of safer and more reliable Li-ion batteries.
10
Dussart, Thibaut. "Batterie lithium tout solide : augmentation de la densité de courant critique et procédé innovant de fabrication". Electronic Thesis or Diss., Sorbonne université, 2021. http://www.theses.fr/2021SORUS396.
Texto completo da fonteResumo:
Le premier axe de cette étude a porté sur l’augmentation de la densité de courant critique atteignable dans des cellules symétriques par la modification des certains paramètres comme la microstructure, l’interface avec le lithium ou encore la pression exercée. Nous avons montré qu’une pression exercée sur les cellules, même faible, modifie l’interface entre l’électrolyte solide et le lithium même dans le cas d’électrolyte à base d’oxyde ; une amélioration de l’ASR est observée lorsque la pression est augmentée. Une ASR aussi faible que 5 Ω.cm2 a été obtenue et une densité de courant critique de 350 µA.cm-2 a ainsi été atteinte. Le deuxième axe de ce travail a porté sur l’étude, la mise en place et l’optimisation d’un procédé de frittage permettant une densification à basse température (120 °C) : le frittage à froid. Les processus de dissolution/précipitation sont rendus possible par l’ajout d’une phase liquide qui s’évapore en partie lors du frittage et par l’application d’une pression de plusieurs centaines de MPa. Nous avons montré que l’électrolyte solide LLZO peut être densifié en ajoutant du DMF comme phase liquide. La conductivité mesurée sur l’électrolyte peut être améliorée par l’ajout d’environ 4% en masse d’un mélange polymère/sel de lithium. Ainsi, une conductivité de 2,2 × 10-4 S.cm-1 peut être obtenue à 25°C. Ensuite nous avons montré qu’une température aussi faible que 120°C permet de co-fritter le LLZO et un matériau d’électrode sans la formation de phase secondaireThe first axis of this study focused on the increase in the critical current density achievable in symmetrical cells by modifying certain parameters such as the microstructure, the interface with lithium, or the pressure evaluated. We have shown that even a low pressure on the cells modifies the interface between the solid electrolyte and lithium even in the case of an oxide-based electrolyte; an improvement in ASR is observed when the pressure is increased. An ASR as low as 5 Ω.cm2 has been obtained and a critical current density of 350 µA.cm-2 has thus been achieved. The second axis of this work focused on the study, implementation, and optimization of a sintering process allowing densification at low temperature (120 °C): the cold sintering process. The dissolution/precipitation processes are made possible by the addition of a liquid phase that partly evaporates during sintering and by the application of a pressure of several hundred MPa. We have shown that LLZO solid electrolyte can be densified by adding DMF as the liquid phase. The conductivity measured on the electrolyte can be improved by adding about 4% by weight of a polymer/lithium salt mixture. Thus, a conductivity of 2.2 × 10-4 S.cm-1 can be obtained at 25 ° C. Then we showed that a temperature as low as 120 ° C allows LLZO and an electrode material to co-sinter without the formation of a secondary phase
11
Hu, Qichao. "Electrode-Electrolyte Interfaces in Solid Polymer Lithium Batteries". Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10187.
Texto completo da fonteResumo:
This thesis studies the performance of solid polymer lithium batteries from room temperature to elevated temperatures using mainly electrochemical techniques, with emphasis on the bulk properties of the polymer electrolyte and the electrode-electrolyte interfaces. Its contributions include: 1) Demonstrated the relationship between polymer segmental motion and ionic conductivity indeed has a Vogel-Tammann-Fulcher (VTF) dependence, and improved the conductivity of the graft copolymer electrolyte (GCE) by almost an order of magnitude by changing the ion-conducting block from poly(oxyethylene) methacrylate (POEM) to a block with a lower glass transition temperature \((T_g)\) poly(oxyethylene) acrylate (POEA). 2) Identified the rate-limiting step in the battery occurs at the cathode-electrolyte interface using both full cell and symmetric cell electrochemical impedance spectroscopy (EIS), improved the battery rate capability by using the GCE as both the electrolyte and the cathode binder to reduce the resistance at the cathode-electrolyte interface, and used TEM and SEM to visualize the polymer-particle interface (full cells with \(LiFePO_4\) as the cathode active material and lithium metal as the anode were assembled and tested). 3) Applied the solid polymer battery to oil and gas drilling application, performed high temperature (up to 210°C) cycling (both isothermal and thermal cycling), and demonstrated for the first time, current exchange between a solid polymer electrolyte and a liquid lithium metal. Both the cell open-circuit-voltage (OCV) and the overall GCE mass remained stable up to 200°C, suggesting that the GCE is electrochemically and gravimetrically stable at high temperatures. Used full cell EIS to study the behavior of the various battery parameters as a function of cycling and temperature. 4) Identified the thermal instability of the cell was due to the reactivity of lithium metal and its passivation film at high temperatures, and used Li/GCE/Li symmetric cell EIS to study the thermal stability of the anode-electrolyte interface, which was responsible for the fast capacity fade observed at high temperatures. 5) Proposed a new electrolyte material and a new battery design called polymer ionic liquid (PIL) battery that can dramatically improve the safety, energy density, and rate capability of rechargeable lithium batteries.Engineering and Applied Sciences
12
Boulenouar-Mohamedi, Fatma Zohra. "Étude de l'oxydation anodique de l'hydrogène à l'interface métal/zircone stabilisée à haute température (métal=platine, nickel, cuivre)". Grenoble INPG, 1995. http://www.theses.fr/1995INPG0055.
Texto completo da fonteResumo:
Ce travail s'inscrit dans le cadre de recherches conduites sur les piles a combustible fonctionnant a haute temperature et mettant en jeu un electrolyte solide conducteur par ions oxydes (zircone stabilisee a l'oxyde d'yttrium: ysz). L'objet de cette recherche est de preciser les influences respectives des pressions partielles d'hydrogene et d'eau dans la polarisation anodique de l'interface metal/ysz, le metal etant: le platine, le nickel ou le cuivre. A l'equilibre, l'etude a montre l'interet de differencier les roles respectifs de l'hydrogene et de la vapeur d'eau et de ne pas traiter les resultats uniquement en terme de pression partielle d'oxygene. Des circuits equivalents rendant compte des reponses de l'electrode sont proposes. Par ailleurs, les resultats obtenus sous polarisation ont montre l'effet electrocatalytique de la vapeur d'eau sur la reaction d'oxydation anodique de l'hydrogene
13
Pan, Jie. "UNDERSTANDING ELECTRICAL CONDUCTION IN LITHIUM ION BATTERIES THROUGH MULTI-SCALE MODELING". UKnowledge, 2016. http://uknowledge.uky.edu/cme_etds/62.
Texto completo da fonteResumo:
Silicon (Si) has been considered as a promising negative electrode material for lithium ion batteries (LIBs) because of its high theoretical capacity, low discharge voltage, and low cost. However, the utilization of Si electrode has been hampered by problems such as slow ionic transport, large stress/strain generation, and unstable solid electrolyte interphase (SEI). These problems severely influence the performance and cycle life of Si electrodes. In general, ionic conduction determines the rate performance of the electrode, while electron leakage through the SEI causes electrolyte decomposition and, thus, causes capacity loss. The goal of this thesis research is to design Si electrodes with high current efficiency and durability through a fundamental understanding of the ionic and electronic conduction in Si and its SEI.
Multi-scale physical and chemical processes occur in the electrode during charging and discharging. This thesis, thus, focuses on multi-scale modeling, including developing new methods, to help understand these coupled physical and chemical processes. For example, we developed a new method based on ab initio molecular dynamics to study the effects of stress/strain on Li ion transport in amorphous lithiated Si electrodes. This method not only quantitatively shows the effect of stress on ionic transport in amorphous materials, but also uncovers the underlying atomistic mechanisms. However, the origin of ionic conduction in the inorganic components in SEI is different from that in the amorphous Si electrode. To tackle this problem, we developed a model by separating the problem into two scales: 1) atomistic scale: defect physics and transport in individual SEI components with consideration of the environment, e.g., LiF in equilibrium with Si electrode; 2) mesoscopic scale: defect distribution near the heterogeneous interface based on a space charge model. In addition, to help design better artificial SEI, we further demonstrated a theoretical design of multicomponent SEIs by utilizing the synergetic effect found in the natural SEI. We show that the electrical conduction can be optimized by varying the grain size and volume fraction of two phases in the artificial multicomponent SEI.
14
Grosselin, Nadège. "Mise au point d'une technique voltampérométrique pour la caractérisation de particules individuelles conductrices de quelques dizaines de microns : application à l'étude de l'adsorption des ions argent et mercure ainsi que du thymol sur la pyrite". Nancy 1, 1998. http://www.theses.fr/1998NAN10142.
Texto completo da fonteResumo:
Au cours de ce travail, une nouvelle technique ultramicroélectrochimique pour la caractérisation des grains individuels conducteurs de quelques dizaines de microns à été mise au point. Elle permet, en particulier, la détection d'espèces solubles formées à l'électrode sans devoir imposer des vitesses de balayage extrémement élevées comme c'est le cas avec les ultramicroélectrodes conventionnelles (10 MV/S suffisent). Les études sans ajout d'électrolyte support sont aussi possibles. La comparaison des voltampérogrammes de AG#2SE avec ceux obtenus par les méthodes classiques a mis en évidence qu'il est possible de caractériser des grains du minéral sans interférence contrairement aux pates de carbone. La technique a ensuite été utilisée parallélement à des méthodes spectroscopiques pour l'étude de l'adsorption de AG#+ et de HG#2#+ sur la pyrite FES#2 (pulpes à 0,5% en poids). Il s'avère que les spéciations de l'argent et du mercure à la surface de FES#2 dépendent fortement de la concentration des ions métalliques en solution. Dans le cas où l'argent est à faible concentration, seul AG#2S se forme. Quand la concentration est plus forte, de l'argent métallique est aussi présent. De même, selon la concentration en mercure, une ou deux espèces de stabilité différente se fixent à la surface de la pyrite. La quantité maximale de mercure s'adsorbant sur le minéral (3,5 10#-#5 MOL/G) est vingt fois moins importante que celle d'argent (6,6 10#-#4 MOL/G). Quand de la pyrite est conditionnée simultanément avec les ions AG#+ et HG#2#+, seul le mercure est adsorbé à sa surface. Il libère en solution l'argent si ce dernier était préalablement fixe sur le minéral. La quantité de mercure alors adsorbée atteint 3,2 10#-#4 MOL/G. Enfin, l'action du thymol sur la pyrite a été envisagée dans le but d'inhiber l'oxydation chimique du minéral. Les mesures électrochimiques ont montré que c'est le produit d'oxydation du thymol, et non lui-même, qui s'adsorbe sur la pyrite et limite son oxydation
15
Armand, Dominique. "Etude du rôle des structures cristallines intrinsèque et induite du platine sur l'électrosorption de l'hydrogène et de l'oxygène en milieu acide". Paris 6, 1986. http://www.theses.fr/1986PA066073.
Texto completo da fonteResumo:
L'influence de la structure cristalline superficielle du platine sur le processus d'électrosorption de l'hydrogène a été étudiée dans différents électrolytes sur les 3 orientations de base avec mise en évidence d'états d'adsorption de l'hydrogène situes à des potentiels exceptionnellement élevés, sur les surfaces à marches (511), (310), (211), (331) et sur un monocristal sphérique. Parallèlement l'effet de l'électrosorption d'oxygène sur la structure de toutes ces surfaces a été étudié en utilisant H2 comme une espèce sonde sensible à la surface cristalline superficielle.
16
Elahi, A. "Plasma electrochemistry : electron transfer at the solid/gas interface". Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1427871/.
Texto completo da fonteResumo:
The ability to control redox reactions at the solid/gas interface is demonstrated for the first time, by considering gaseous flame plasma as an electrolyte. An innovative method to perform potentio-dynamic experiments in a liquid-free electrochemical system using flame plasma is described. This novel approach can help apply the well-established foundations of electrochemistry developed almost exclusively in liquids, to the new context of gas plasma. There are limited examples using plasmas as media to study redox reactions but no examples of voltammetry in the gas phase at true solid/gas interfaces. Successful electrochemical measurements are illustrated by doping the flame plasma with both inorganic and organic species, and recording distinct faradaic peaks at defined potentials in cyclic voltammograms. The sensitivity of the system is highlighted by the ability to distinguish between several amino acids, pinpointing specific functional groups. The most significant innovation responsible for these measurements is the development of a reference electrode able to function at temperatures over 1300 K. Extensive assessment of several materials has enabled the development and optimisation of a reference electrode, allowing an extension of the potential window to 10 V; an unprecedented value in electrochemistry. After careful experimentation and appropriate control experiments, the features observed are confirmed as specific reduction processes at the solid/gas interface. Undoubtedly, and perhaps expectedly, there are significant departures from the analogous process in condensed phases. The physical origin of these electrochemical signals is discussed and a framework of interpretation upon which a full mechanistic understanding can be based is provided. The scope of commercial and academic impact is extensive. Liquid-free electrochemistry presents access to a plethora of redox reactions, which lie outside potential limits defined by liquids. The prospect of new redox chemistries will enable new technological applications such as electrodeposition and electroanalysis, which have significant economic and environmental benefits.
17
Walls, Michael Gerard. "Electron energy-loss spectroscopy of surfaces and interfaces". Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254503.
Texto completo da fonte
18
Ren, Hao. "First principles simulations of electron transport at the molecule-solid interface". Doctoral thesis, KTH, Teoretisk kemi (stängd 20110512), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-12870.
Texto completo da fonteResumo:
In this thesis I concentrate on the description of electron transport properties of microscopic objects, including molecular junctions and nano junctions, in particular, inelastic electron tunneling in surface-adsorbate systems are examined with more contemplations. Boosted by the rapid advance in experimental techniques at the microscopic scale, various electric experiments and measurements sprung up in the last decade. Electric devices, such as transistors, switches, wires, etc. are expected to be integrated into circuit and performing like traditional semiconductor integrated circuit (IC). On the other hand, detailed information about transport properties also provides new physical observable quantities to characterize the systems. For molecular electronics, which is in the state of growing up, its further applications demands more thorough understanding of the underlying mechanism, for instance, the effects of molecular configuration and conformation, inter- or intra-molecular interactions, molecular-substrate interactions, and so on. Inelastic electron tunneling spectroscopy (IETS), which reflects vibration features of the system, is also a finger print property, and can thus be employed to afford the responsibility of single molecular identification with the help of other experimental techniques and theoretical simulations.There are two parts of work presented in this thesis, the first one is devoted to the calculation of electron transport properties of molecular or nano junctions: we have designed a negative differential resistance (NDR) device based on graphene nanoribbons (GNRs), where the latter is a star material in scientific committee since its birth;The transport properties of DNA base-pair junctions are also examined by theoretical calculation, relevant experimental results on DNA sequencing have been explained and detailed issues are suggested.The second part focused on the simulation of scanning tunneling microscope mediated IETS (STM-IETS). We have implemented a numerical scheme to calculate the inelastic tunneling intensity based on Tersoff-Hamann approximation and finite difference method, benchmark results agree well with experimental and previous theoretical ones; Two applications of single molecular chemical identification are also presented following benchmarking.QC20100630
19
Kiely, C. J. "An electron microscopy study of some metal-semiconductor interfaces". Thesis, University of Bristol, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375011.
Texto completo da fonte
20
Liu, Ying. "Fabrication of Nanostructured Electrodes and Interfaces Using Combustion CVD". Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7937.
Texto completo da fonteResumo:
Reducing fabrication and operation costs while maintaining high performance is a major consideration for the design of a new generation of solid-state ionic devices such as fuel cells, batteries, and sensors. The objective of this research is to fabricate nanostructured materials for energy storage and conversion, particularly porous electrodes with nanostructured features for solid oxide fuel cells (SOFCs) and high surface area films for gas sensing using a combustion CVD process.
This research started with the evaluation of the most important deposition parameters: deposition temperature, deposition time, precursor concentration, and substrate. With the optimum deposition parameters, highly porous and nanostructured electrodes for low-temperature SOFCs have been then fabricated. Further, nanostructured and functionally graded La0.8Sr0.2MnO2-La0.8SrCoO3-Gd0.1Ce0.9O2 composite cathodes were fabricated on YSZ electrolyte supports. Extremely low interfacial polarization resistances (i.e. 0.43 Wcm2 at 700¡ãC) and high power densities (i.e. 481 mW/cm2 at 800¡ãC) were generated at operating temperature range of 600¡ãC-850¡ãC.
The original combustion CVD process is modified to directly employ solid ceramic powder instead of clear solution for fabrication of porous electrodes for solid oxide fuel cells. Solid particles of SOFC electrode materials suspended in an organic solvent were burned in a combustion flame, depositing a porous cathode on an anode supported electrolyte.
Combustion CVD was also employed to fabricate highly porous and nanostructured SnO2 thin film gas sensors with Pt interdigitated electrodes. The as-prepared SnO2 gas sensors were tested for ethanol vapor sensing behavior in the temperature range of 200-500¡ãC and showed excellent sensitivity, selectivity, and speed of response.
Moreover, several novel nanostructures were synthesized using a combustion CVD process, including SnO2 nanotubes with square-shaped or rectangular cross sections, well-aligned ZnO nanorods, and two-dimensional ZnO flakes. Solid-state gas sensors based on single piece of these nanostructures demonstrated superior gas sensing performances. These size-tunable nanostructures could be the building blocks of or a template for fabrication of functional devices.
In summary, this research has developed new ways for fabrication of high-performance solid-state ionic devices and has helped generating fundamental understanding of the correlation between processing conditions, microstructure, and properties of the synthesized structures.
21
Hirayama, Tsukasa, Takeharu Kato, Syunta Mizuno e Takayoshi Tanji. "Electron Holography of Hetero-Interfaces in Solid Oxide Fuel Cells". Cambridge University Press, 2009. http://hdl.handle.net/2237/14326.
Texto completo da fonte
22
Walsh, Caroline Annabelle. "Modelling and interpretation of electron energy-loss spectra from interfaces". Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316804.
Texto completo da fonte
23
Tanji, Takayoshi, Hiroshi Moritomo, Tetsuo Shimura, Takeharu Kato e Tsukasa Hirayama. "Electron Holography of a Hetero-Interface in a Solid Oxide Fuel Cell". Cambridge University Press, 2007. http://hdl.handle.net/2237/10298.
Texto completo da fonte
24
Pengpad, Atip. "Electron spectroscopy of surfaces and interfaces for novel solid state photovoltaic cells". Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/electron-spectroscopy-of-surfaces-and-interfaces-for-novel-solid-state-photovoltaic-cells(d4b15a1d-085c-497b-8b60-6b49987e6d12).html.
Texto completo da fonteResumo:
Novel photovoltaic cells receive considerable attention from researchers as evidenced by high numbers of published articles. Different types of materials are currently being examined in order to reduce the cost and improve the efficiency of solar cells. Essentially, solar cells are constructed by placing layers of light absorber between electron and hole transport materials. Electricity generation by solar cells involves multiple processes. These processes require an understanding of the physical properties of the surfaces and interfaces of the materials. In this thesis, materials for novel photovoltaic cells are studied by X ray photoelectron spectroscopy (XPS), a surface and interface characterisation technique. The materials studied in this thesis are colloidal quantum dots (CQDs) of the core/shell systems CdTe/CdSe and PbS/CdS, and CQDs that have been surface passivated using Cl- (CdTe/Cl) and CdS (CdTe/CdSe/CdS and PbS/CdS). Moreover, CsSnI3, a perovskite material, is also studied in both bulk and thin film form. CQDs can be used as light absorbers in solar cells while CsSnI3 can be employed as the hole transport material. The role of the core shell structure and surface passivation treatment is to improve or maintain charge transport as well as acting as a protective layer to the CQDs. Depth profiling synchrotron radiation XPS is used to determine these structures. In the CdTe/CdSe samples, the elemental ratio between Se (shell) and Te (core) increases with decreasing sampling depth, demonstrating the presence of a CdSe shell located at the surface of the CQDs. The shell thicknesses of the core-shell systems are estimated from XPS and show that the addition of the third thin shell (of CdS) protects the CQD during ligand exchange. Cl- passivation is shown to reduce the energy the valence band maximum and the energy gap of CdTe CQDs. This is associated with the passivation of midgap trap states due to the removal of dangling bonds at the surface of CQDs. Surface passivation is shown to improve the stability of CQDs to air exposure. This is indicated by a significant reduction of the surface oxide species in the passivated PbS/CdS samples. In the unpassivated core-only PbS samples, however, oxidation rapidly occurs which affects the electronic states required for charge transport in solar cells. XPS studies of CsSnI3 show that this material is reactive to air exposure. Surface preparation techniques are performed to remove the contamination layer and reveal the physical properties of the perovskite itself. This is confirmed by the elemental ratios from XPS. The metallic character of CsSnI3 is also observed in the valence band spectra as evidenced by the appearance of the Fermi edge.
25
Bennett, Raffeal A. "Characterization of the Solid-Electrolyte Interface on Sn Film Electrodes by Electrochemical Quartz Crystal Microbalance". The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1399048324.
Texto completo da fonte
26
Chhor, Sarine. "Etude et modélisation de l'interface graphite/électrolyte dans les batteries lithium-ion". Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI067/document.
Texto completo da fonteResumo:
Cette thèse se positionne dans le domaine des batteries lithium-ion. Elle a pourobjectif de mieux comprendre le fonctionnement de l’électrode négative de graphiteen étudiant le processus de formation du film de passivation, couramment appeléSEI (Solid Electrolyte Interface) créé à l’interface avec l’électrolyte. Ce travail nousa conduit à proposer des modèles pouvant expliquer comment se forme la SEI et àidentifier les phénomènes qui entrent en jeu dans le fonctionnement de la batterie.La SEI résulte de la réaction entre l’électrode de graphite, les ions lithium et les moléculesorganiques de l’électrolyte qui survient lors du premier processus d’insertion.Elle est principalement composée des produits de décomposition de l’électrolyte etles ions lithium consommés ne sont plus échangeables. Elle est donc responsable dela capacité irréversible observée lors du premier cycle de formation, correspondantà la différence de capacité entre le processus d’insertion et le processus de désinsertion.Il est donc essentiel de mieux comprendre les paramètres qui l’influencentpour pouvoir ainsi la contrôler et limiter la perte irréversible de capacité. Les performancesen capacité de l’élément lithium-ion sont directement liées à cette valeurde capacité irréversible, elle doit être limitée afin de maximiser la quantité d’ionslithium échangée entre l’électrode négative et l’électrode positive. La stabilité dela SEI conditionne ensuite le comportement en cyclage de l’électrode au cours dutemps.Dans ce mémoire de thèse, nous avons choisi de caractériser le comportement del’électrode de graphite en faisant varier la nature de l’électrolyte et la taille desparticules de graphite tout en restant le plus proche possible du fonctionnementd’une vraie batterie. Au travers des techniques de caractérisations électrochimiques(cyclage galvanostatique, spectroscopie d’impédance) associées à des techniques decaractérisation de surface (spectroscopie de photoélectrons X, microscopie électroniqueà balayage), les résultats obtenus ont permis de proposer un nouveau modèlede formation de la SEI.Pour l’électrolyte, nous avons choisi de ne regarder que l’effet du solvant (le carbonatede propylène) et de l’additif (le carbonate de vinylène). Ces deux composésentrent dans la composition des électrolytes utilisés dans les éléments lithium-ioncommerciaux. Pour l’électrode de graphite, le choix des particules s’avère primordialpuisque chaque type de particules possède une chimie de surface spécifique (plans223basaux ou plans prismatiques) susceptible de réagir différemment vis-à-vis de l’électrolyte.Deux particules de graphite, de taille et de morphologie différentes, ont étéétudiées. Elles sont utilisées séparément en tant que matière active dans les électrodesnégatives des batteries lithium-ion. Notre spécificité est d’avoir préparé desélectrodes constituées par un mélange de ces deux particules et de les avoir ensuitecaractérisées en formation. L’application de conditions de fonctionnement différentescomme le régime de cyclage et la température d’essai ont mis en évidence les valeursidéales conduisant à minimiser la dégradation de l’électrolyte et à optimiser laqualité du film.Nous avons abouti, au travers de l’ensemble des méthodes de caractérisations misesen oeuvre, à une meilleure compréhension des mécanismes de formation du film depassivation permettant ainsi d’améliorer cette étape essentielle à la pérennité desperformances de l’électrode dans le temps. Ce travail a donc un réel impact auniveau industriel. Le modèle de formation proposé apporte un éclairage nouveau auprocessus de formation et peut permettre également d’aider en amont à la fabricationdes particules de graphiteThis work relates to the lithium ion battery field. The purpose of this study is tobetter understand the behavior of graphite electrodes by focusing on the formationof a passive layer named Solid Electolyte Interface (SEI) which is formed at thegraphite/electrolyte interface. This work has led us to put forward models whichcan explain the SEI formation and identify the reactions which take place in alithium ion battery.The SEI results from reactions between graphite electrode, lithium ions and organicmolecules from the electrolyte during the first charge of the lithium ion battery. It ismainly composed of decomposition products from the electrolyte. Consumed lithiumions can no longer be used in the next cycle. The SEI is therefore responsible for theirreversible capacity during the first formation cycle which is the charge loss betweenthe intercalation process and the deintercalation process. It is necessary to betterunderstand the impact of the formation conditions and other parameters in orderto control and limit the irreversible charge loss. Lithium ion battery performancesdepend on this irreversible capacity, this value has to be reduced in order to maximizethe amount of exchanged lithium ions between negative and positive electrodes. TheSEI stability will determine the electrode behavior upon cycling.In this thesis, we chose to study the graphite behavior by testing several electrolytecompositions and graphite particle sizes in electrochemical cells similar to areal battery. Electrochemical techniques (galvanostatic cycling and electrochemicalimpedance spectroscopy) and surface analyses (X-ray photoelectron spectroscopy,scanning electron microscopy) will be combined. These results helped us to developa new model of the SEI formation.For the electrolyte, we chose to study the effect of the solvent (propylene carbonate)and the additive (vinylene carbonate). Both components are commonly used inthe electrolyte for commercial lithium ion batteries. For the graphite electrode, thechoice of graphite particles is essential because each graphite family has its ownsurface chemistry (basal and prismatic surfaces) which can react in many wayswith the electrolyte. Two graphite particles, with specific sizes and morphologiesare studied. They are separately used as active materials for negative electrodes inlithium ion batteries. Our unique approach is to prepare graphite electrodes basedon a mix of both particles with various compositions and then test the electrode225performances. After testing several formation conditions such as the cycling rateand the temperature, we found the ideal formation conditions for minimizing theelectrolyte decomposition and optimizing the film quality.Finally, based on all the characterization methods, we came to a better understandingof the film formation process. In this way, we have improved this essentialpreliminary step which can now lead to more durable cycling performances overtime. This study can have a major impact on the industrial level. The formationmodel cast a new light on the formation process and can therefore help to makeefficient graphite electrodes
27
Veal, Timothy David. "High resolution electron energy loss spectroscopy of narrow gap III V semiconductor surfaces and interfaces". Thesis, University of Warwick, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252483.
Texto completo da fonte
28
Swamy, Tushar. "Electro-chemo-mechanical instabilities at interfaces in al-solid-state lithium-ion batteries". Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/118732.
Texto completo da fonteResumo:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 107-115).
Inorganic solid-state electrolytes (SSEs) could replace flammable liquid electrolytes and improve the safety of Li-ion batteries. Furthermore, these SSEs could enable metal anodes, providing a significant improvement in cell-level energy density compared to the state-of-the-art. Recent improvements in the ionic conductivity of ceramic SSEs have invigorated commercial interest, prompting investigations into SSE/electrode interfacial properties. However, these investigations have revealed several challenges preventing the widespread adoption of all-solid-state Li-ion batteries. SSEs experience Li dendrite propagation and short circuit above a critical current density, similar to liquid electrolytes. While the pathways for Li penetration through a ceramic SSE such as grain boundaries and surface pores have been identified, the Li penetration mechanism is unclear. In addition, most SSEs experience detrimental redox reactions at the Li anode and 4 V cathode interface. The interfacial redox behavior of inorganic SSEs isn't well understood and requires further investigation. This thesis investigates the Li penetration mechanism into sulfide-based amorphous and polycrystalline SSEs, and garnet oxide-based single-crystal and polycrystalline SSEs. It also investigates the electrochemical redox behavior of sulfide-based SSEs. Experimental results show that Li can penetrate into single crystal SSEs devoid of grain boundaries and surface pores. Above a critical current density, the mechanical stress at a critically-sized Li-filled flaw tip at the SSE surface can breach the SSE fracture stress to initiate and propagate a crack through which Li penetrates the SSE, until a short circuit occurs. An electrochemo- mechanical model based on the Griffith theory of brittle ceramic fracture was developed, which relates the SSE fracture stress to SSE fracture toughness and surface flaw size. Experimental determination of the fracture toughness of sulfide-based SSEs revealed that these SSEs are compliant yet significantly more brittle than oxide-based SSEs. In addition, a cyclic-voltammetry based technique was developed to show that a sulfide-based SSE electrochemically decomposes to produce a redox-active interphase at the SSE/electrode interface. This is unlike in case of liquid electrolytes which decompose into an electrochemically irreversible interphase.
by Tushar Swamy.
Ph. D.
29
Lauret, Hervé. "Propriétés électriques et électrochimiques de manganites de lanthane dopées comme matériau de cathode pour pile à combustible à oxyde électrolyte solide". Grenoble INPG, 1994. http://www.theses.fr/1994INPG0053.
Texto completo da fonteResumo:
Ce travail consiste en l'etude de materiaux de cathode pour les piles a combustible haute temperature. Ces materiaux ont pour formule generale la1-xsrxmno3 et (la1-yyy)0,5sr0,5mno3. Dans un premier chapitre nous faisons le point sur l'etat des recherches sur les piles a combustible a oxyde electrolyte solide et leurs constituants. Le deuxieme chapitre presente la synthese des echantillons ainsi que les differents dispositifs de mesures. Le chapitre trois est consacre a la caracterisation physique et electrique des echantillons. Nous avons montre en particulier que le dopage a l'yttrium diminuait le coefficient de dilatation thermique des manganites de lanthane. Pour les echantillons exempts d'yttrium une conductivite maximale est obtenue pour x=0,55. Une etude sur la reaction de reduction de l'oxygene a l'interface la1-xsrxmno3/y2o3-zro2 est menee dans le chapitre quatre. Nous confirmons l'apparition d'un effet electrocatalytique specifique a ce materiau d'electrode. Nous apportons une contribution complementaire a la comprehension du processus d'electrode: l'echantillon qui presente la plus grande activite electrocatalytique est celui qui a la plus forte conductivite electrique. Aux faibles polarisations cathodiques, superieures a -150 mv/air, nous prouvons que l'etape limitante a lieu le long du contact triple. Aux plus fortes polarisations cathodiques nous emettons l'hypothese d'une extension progressive de la reaction sur une zone annulaire autour du perimetre de contact entre le materiau de cathode et l'electrolyte. Enfin, la surface du materiau d'electrode exposee au gaz n'est pas limitante
30
Azizan, Mustapha. "Contribution à l'étude de l'interaction métaux réfractaires (W, Mo, Nb, Ta) - Si(111)(7x7) : [thèse en partie soutenue sur un ensemble de travaux]". Grenoble 1, 1987. http://www.theses.fr/1987GRE10064.
Texto completo da fonte
31
Guillet, Stéphane. "Etude des propriétés électroniques des interfaces Ag/Si(100) et Cu/Si(100)". Grenoble 1, 1993. http://www.theses.fr/1993GRE10065.
Texto completo da fonteResumo:
Les premiers stades de la formation des interfaces ag/si(100) et cu/si(100) a temperature ambiante ont ete etudies in situ par reflectivite differentielle (1. 5 ev-5. 0 ev) associee a des techniques classiques de surface: photoemission uv (ups), spectroscopie auger (aes) et diffraction d'electrons lents (del). Pour des depots plus importants (quelques dizaines a quelques centaines d'angstroms), des etudes ex situ de la reflectivite dans l'infra-rouge (0. 025 ev-1 ev) et de la conductivite electrique (entre 4k et 300k) sont egalement presentees. Un reflectometre differentiel, construit pour ces etudes et permettant de mesurer des variations du facteur de reflexion induites par des fractions de monocouche, est decrit en detail. La reflectivite differentielle est particulierement bien adaptee a l'observation des electrons de la bande de conduction du metal, difficiles a observer en photoemission. Ainsi, dans le cas du cuivre, nous avons observe d'importantes modifications de la reflectivite au niveau du bord d'absorption du cuivre indiquant la formation d'un siliciure. Cette information s'est revelee complementaire des resultats obtenus en photoemission et en spectroscopie auger, a savoir le deplacement en energie de la bande d du cuivre et le dedoublement de la raie auger lvv du silicium. Les etudes de resistivite et de reflectivite montrent pour certains depots de cuivre ou d'argent une certaine discontinuite entre les grains metalliques, meme pour des epaisseurs de plusieurs centaines d'angstroms. Ces resultats ont pu etre decrits par un modele de maxwell-garnett
32
Agel, Eric. "Electrode à air électrolyte solide polymère alcalin pour piles à combustible et générateur métal-air". Paris 7, 2002. http://www.theses.fr/2002PA077002.
Texto completo da fonte
33
So, Biu 1959. "THE METHODOLOGY AND IMPLEMENTATION OF RELAXATION METHOD TO INVESTIGATE ELECTRO-THERMAL INTERACTIONS IN SOLID-STATE INTEGRATED CIRCUITS". Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276384.
Texto completo da fonte
34
Lakhdari, Hacène. "Etude par technique spectroscopique de capacite transitoire des defauts a l'interface semiconducteur-isolant". Paris 6, 1988. http://www.theses.fr/1988PA066341.
Texto completo da fonteResumo:
Explication du comportement inhabituel de certaines structures mos en dlts (non-saturation du spectre dlts pour un remplissage total de la densite d'etats d'interface) par une interaction par effet tunnel entre les porteurs libres du semiconducteur et les defauts des premieres couches d'oxyde (etats lents). Etude de la degradation des interfaces si-sio::(2) sous injection d'electrons chauds en comparant la cinetique de creation des etats lents et rapides. Etude des defauts induits par plasma ionique reactif
35
Ganser, Markus [Verfasser], e M. [Akademischer Betreuer] Kamlah. "On the Electro-Chemo-Mechanical Coupling in Solid State Batteries and its Impact on Morphological Interface Stability / Markus Ganser ; Betreuer: M. Kamlah". Karlsruhe : KIT Scientific Publishing, 2021. http://d-nb.info/1228537348/34.
Texto completo da fonte
36
Galparsoro, Larraza Oihana. "Phonon and electron excitations in diatom abstraction from metallic surfaces". Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0417/document.
Texto completo da fonteResumo:
La rationalisation des processus chimiques élémentaires aux surfacesest d'intérêt primordial pour de nombreux phénomènes naturels ou d'intérêttechnologique. D'un point de vue fondamental, la façon dont l'énergie, concomitanteà toute réaction chimique, est distribuée parmi les degrés de liberté des moléculesformées et/ou transférée à la surface est loin d'être systématisée. Dans ce travail,des simulations, reposant sur la méthode des trajectoires quasi-classiques (QCT),sont réalisées pour examiner cette problématique lors de recombinaisons demolécules d'hydrogène (H2) et d'azote (N2) résultant de l'abstraction d'atomesadsorbés via collision par un atome provenant de la phase gazeuse sur des surfacesde Tungstène - W(100) et W(110) - à taux de couverture non nul. Ces processussont ici étudiés pour leur intérêt en physique des interactions plasma-paroi. Dessurfaces d'énergie potentielle, construites à partir de calculs de structure électroniquebasés sur la théorie de la fonctionnelle densité (DFT), sont utilisées pour simuler,dans le cadre de la mécanique classique - incluant les corrections semi-classiquespertinentes - les processus ultrarapides dit de "Eley-Rideal" et par "atomes-chauds"(sub-picoseconde). La mise en place de modèle effectifs, pour tenir compte de ladissipation de l'énergie aux phonons de la surface et aux excitations électroniques(paires électron-trou), permet de rationaliser la dynamique non-adiabatique del'abstraction atomique aux surfaces métalliquesThe rationalization of elementary processes at surfaces is of prime importance for numerous natural and technological areas. From a fundamental pointof view, the way the energy concomitant to any chemical reaction is distributed among the desorbing molecules degrees-of-freedom and the surface is far frombeing fully pictured. In this work, quasiclassical molecular dynamics (QCT)simulations have been carried out to investigate this issue for the recombination ofH2 and N2 resulting from atomic adsorbate abstraction by atom scattering off theW(100) and W(110) covered surfaces, these processes being of relevance inplasma-wall interactions. Potential energy surfaces, built from density functional(DFT) theory calculations, have been used to simulate, within the framework ofclassical dynamics (including semi-classical corrections), the subpicosecond Eley-Rideal and Hot-Atom processes. The implementation of effective models to accountfor energy dissipation to surface phonons and electron-hole pair excitations, have allowed to rationalize the non-adidabatic dynamics of atom abstraction at metalsurfaces
37
Barbier, Eric. "Epitaxie par la methode des organometalliques d'heterostructures gaas/gaalas a application en hyperfrequence". Orléans, 1987. http://www.theses.fr/1987ORLE2003.
Texto completo da fonteResumo:
Croissance reproductible de materiaux de haute purete qui se caracterisent dans le cas de gaas par une concentration en impuretes residuelles voisine de e14 porteurs par cm**(3), une mobilite electronique a 77k superieur a 110. 000 cm**( non2)v. S et dans le cas du gaalas par un niveau de dopage residuel de e15 porteurs par cm**(3) pour une teneur en aluminium de 25%. La caracterisation des interfaces par microscopie demontrent la croissance reproductibles d'heterojonctions aux transitions de l'ordre de la monocouche
38
Sar, Jaroslaw. "Interfaces et durabilité d'électrodes avancées pour l'énergie : IT-SOFC et SOEC Coral Microstructure of Graded CGO/LSCF Oxygen Electrode by Electrostatic Spray Deposition for Energy (IT-SOFC, SOEC) Electrochemical properties of graded and homogeneous Ce0.9Gd0.1O2-δ-La0.6Sr0.4Co0.2Fe0.8O3-δ composite electrodes for intermediate-temperature solid oxide fuel cells Three dimensional analysis of Ce0.9Gd0.1O1.95–La0.6Sr0.4Co0.2Fe0.8O3−δ oxygen electrode for solid oxide cells Mechanical behavior of Ce0.9Gd0.1O1.95-La0.6Sr0.4Co0.2Fe0.8O3−δ oxygen electrode with a coral microstructure for solid oxide fuel cell and solid oxide electrolyzer cell Durability test on coral Ce0.9Gd0.1O2-δ-La0.6Sr0.4Co0.2Fe0.8O3-δ with La0.6Sr0.4Co0.2Fe0.8O3-δ current collector working in SOFC and SOEC modes". Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI106.
Texto completo da fonteResumo:
Interfaces et durabilité des électrodes de pointe pour l'énergie (PAC et EHT)L'objectif de cette thèse concerne l'élaboration, par atomisation électrostatique, d'une électrode à oxygène à architecture innovante, basée sur un composite Ce0.9Gd0.1O1.95 (CGO) - La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) possédant un gradient de composition ou une composition homogène. Cette électrode a été déposée sur un substrat de zircone yttriée (YSZ = 8 % mol. Y2O3-ZrO2) sur laquelle, a été intercalée au préalable une couche barrière mince et dense de CGO. Cette électrode possède une microstructure innovante, à porosité élevée permettant d'obtenir une grande surface active qui devrait conduire à l'amélioration des performances électrochimiques. Le comportement électrique de l'électrode a été étudié par spectroscopie d'impédance en fonction de la température et sous air. Une description microstructurale détaillée a été effectuée à l'aide d'un modèle de reconstruction 3D obtenu par -MEB équipé d'une sonde ionique focalisée et par nanotomographie X. Ces propriétés microstructurales ont été reliées aux propriétés électriques. Les propriétés mécaniques et tribologiques de cette électrode composite ont été déterminées par des tests du scotch et ultra-microindentation. Finalement, des tests de durabilité ont été effectués sur une électrode de grande taille possédant une surface active de 45 cm2 jusqu'à 800 h à environ 770°C, dans une cellule complète de configurations PAC et fonctionnant respectivement sous H2 et un mélange H2/H2OInterfaces and durability of advanced electrodes for energy (IT-SOFC and SOEC)The objective of this PhD thesis is to fabricate advanced oxygen electrode based on Ce0.9Gd0.1O1.95 (CGO) and La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) with graded and homogeneous composition onto yttria-stabilized zirconia (YSZ = 8 mol. % Y2O3-doped ZrO2) electrolyte using electrostatic spray deposition. A thin and dense layer of CGO was inserted between LSCF and YSZ to serve as a barrier diffusion layer. The novel microstructure with high porosity and large surface area is expected to improve the electrochemical performances. The electrical behavior of the electrode was investigated by impedance spectroscopy versus temperature in air. A detailed microstructural description was performed by 3D reconstructed model from FIB-SEM and X-ray nanotomography and related to electrical properties. The mechanical analysis was performed by scratch and ultramicroindentation tests. Finally, durability tests were performed on the electrode with 45 cm2 oxygen active area, up to 800 h at around 770°C, in full cell SOFC and SOEC configurations operating respectively in H2 and H2/ H2O mixture
39
Ruterana, Pierre. "Structure des interfaces, etude par microscopie electronique en transmission, application : materiaux semiconduteurs iii-v et multicouches pour optiques dans le domaine des rayons x mous". Caen, 1987. http://www.theses.fr/1987CAEN2032.
Texto completo da fonteResumo:
Nous avons surtout utilise le mode "haute resolution" sur un microscope a 200kv. La resolution obtenue etait de 2. 4 a. La technique de peparation d'echantillons que nous avons mise au point pour l'etude du procede de passivation (si::(3)n::(4)/gaas) nous a permis de caracteriser dans de tres bonnes conditions les multicouches pour rayons x mous et les heterostructures de croissance epitaxiale. Ce travail fut un suivi des procedes en conjugaison avec d'autres techniques de caracterisation. La comparaison des resultats de ces diverses techniques nous a permis d'apprehender la chimie et la physique des interfaces dans les materiaux etudies
40
Tizei, Luiz Henrique Galvão. "Homogeneidade química, interfaces e defeitos estruturais em nanofios de semicondutores III-V". [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277621.
Texto completo da fonteResumo:
Orientador: Daniel Mário UgarteTese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
Made available in DSpace on 2018-08-17T20:15:26Z (GMT). No. of bitstreams: 1 Tizei_LuizHenriqueGalvao_D.pdf: 12237887 bytes, checksum: e97ac7041ecfd4c30088cf9b43d9849a (MD5) Previous issue date: 2011
Resumo: O desenvolvimento de novos materias tem grande interesse devido à ocorrência de novos fenômenos e propriedades, as quais podem ser usadas em futuras aplicações tecnológicas. Em particular, nas últimas décadas, esforços imensos foram realizados buscando compreender nanomateriais e os efeitos da redução de tamanho e de dimensão. Entre os diferentes avanços alcançados, podemos citar o desenvolvimento significativo de nanofios semicondutores (estruturas quasi-unidimensionais) com dezenas ou centenas de nanometros de espessura e milhares de nanometros de comprimento. O método mais utilizado para o crescimento de nanofios é o método catalítico chamado VLS (Vapor-Líquido-Sólido), no qual uma nanopartícula metálica serve como sorvedouro preferencial de átomos de um vapor e, também, como posição para a formação de um sólido (nanofio). O VLS foi proposto por Wagner e Ellis nos anos 60. Em nossos trabalhos, nos concentramos no estudo de nanofios de semicondutores III-V crescidos em um reator de Epitaxia de Feixe Químico (CBE) catalisados por nanopartículas de Au. Mais especificamente, estudamos nanofios de InP, InAs, InGaP, InAsP e heteroestruturas InP/InAs/InP. Como a qualidade de interfaces e homogeneidade química do material crescido, influenciam diretamente as propriedades ópticas e elétricas de nanofios, nossa pesquisa nos levou a avaliar os limites da aplicação de diversas técnicas de microscopia eletrônica de transmissão aplicadas: TEM (Microscopia Eletrônica de Transmissão), STEM (Microscopia Eletrônica de Transmissão em Varredura), HRTEM (Microscopia Eletrônica de Transmissão de Alta Resolução), EDS (Espectroscopia de Raios-X Dispersados em Energia) e EELS (Espectroscopia de Perda de Energia de Elétrons). Como consequência, determinamos os limites de detecção de variações químicas e de medidas de larguras de interfaces das diferentes técnicas. Em particular, devido às limitações impostas pelo dano por radiação no material, propusemos o uso de deslocamentos químicos de plasmons (EELS) para a caracterização química de nanoestruturas de semicondutores III-V. Desenvolvemos uma metodologia para a análise de seções transversais de nanofios de InAsP. Os experimentos realizados indicam a diferença entre os semicondutores produzidos por crescimento axial (catalítico) e por radial (bidimensional). Além disso, a análise química detalhada de heteroestruturas InP/InAs/InP levou a detecção de concentrações inesperados de As no segmento final de InP. Interpretamos esta observação como uma indicação de que As difunde através da nanopartícula catalisadora durante o crescimento, demonstrando uma rota de incorporação de elementos do grupo V em nanofios crescidos pelo método VLS. Finalmente, estudamos os efeitos de defeitos estruturais extendidos, como discordâncias na morfologia e distorções estruturais de nanofios. Neste sentido, observamos a torção de Eshelby em nanofios de InP contendo discordâncias em parafuso únicas. Nossos resultados mostram que as taxas de torção medida são muito maiores (até 100%) do que o previsto pela teoria elástica macroscópica. Isto mostra as mudanças significativas nas propriedades mecânicas e estruturais em nanoestruturas e ilustra o papel importante de estudos detalhados de microscopia eletrônica para a análise de deformações em nanoestruturas
Abstract: The development of new materials has great interest due to the possibility of finding new phenomena and properties, which can be used in technological applications. In particular, in the last decades, huge efforts have been made in order to understand nanomaterials and, the effects of size and dimensionality reduction. Among different advances, it is worth noting the significant development of semiconductor nanowires (quasi-one dimensional structures) with tens or hundreds of nanometers in diameter and thousands of nanometers in length. The catalytic method VLS (Vapor-Liquid-Solid) is the most used approach for nanowire preparation, in which a metal nanoparticle serves as a preferential sink for atoms from a vapor and, also, as the position for the solid nucleation; this method was proposed by Wagner and Ellis in the 60s. In our work, we have focused on the study of III-V semiconductor nanowires grown by Chemical Beam Epitaxy (CBE) catalyzed by Au nanoparticles. Specifically, we have studied different III-V nanowires (InP, InAs, InGaP and InAsP), as ell as, some heterostructured wires (InP/InAs/InP). As the quality of interfaces and the chemical homogeneity of materials directly influence the optical and electrical properties of nanowires, our research have led us to assess the limit of applicability of several characterization techniques based on transmission electron microscopy: TEM (Transmission Electron Microscopy), STEM (Scanning Transmission Electron Microscopy), HRTEM (High Resolution Transmission Electron Microscopy), EDS (Energy Dispersed X-Ray Spectroscopy) and EELS (Electron Energy Loss Spectroscopy). As a consequence, we have determined the detection limit for the measurement of chemical composition variations and interface widths. In particular, due to the limitations imposed by radiation damage on III-V nanowires, we have proposed the use of Plasmon chemical shifts (EELS) to the chemical characterization of III-V nanostructures. We have analyzed the cross sections of InAsP nanowires and we have been able to reveal a difference between the semiconductors materials produced by the axial (catalytic) and radial (bidimensional) growth. Through the detailed chemical analysis of InP/InAs/InP heterostructures we have detected an unexpected concentration of As in the last InP segment of the heterostructure. We have interpreted this result as an indication that As diffuses through the catalytic nanoparticle during growth. This demonstrates an incorporation route for group V atoms in nanowires grown by VLS. Finally, we have studied the effects of extended structural defects, like dislocations, in the morphology and structural distortions of nanowires. In this sense, we have observed the Eshelby twist in InP nanowires containing a single screw dislocation. Our results show that measured twist rates are much larger (up to 100%) than the predictions from the elasticity theory. This shows the significant change of mechanical and structural properties in nanoscale and, illustrates the important role of a careful electron microscopy studies to analyze deformations in nanostructures
Doutorado
Física da Matéria Condensada
Doutor em Ciências
41
Goble, Nicholas James. "ELECTRONIC TRANSPORT AT SEMICONDUCTOR AND PEROVSKITE OXIDE INTERFACES". Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1454002713.
Texto completo da fonte
42
Yang, Xiangwen, Zhixing Lin, Jingxu Zheng, Yingjuan Huang, Bin Chen, Yiyong Mai e Xinliang Feng. "Facile template-free synthesis of vertically aligned polypyrrole nanosheets on nickel foams for flexible all-solid-state asymmetric supercapacitors". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-224947.
Texto completo da fonteResumo:
This paper reports a novel and remarkably facile approach towards vertically aligned nanosheets on three-dimensional (3D) Ni foams. Conducting polypyrrole (PPy) sheets were grown on Ni foam through the volatilization of the environmentally friendly solvent from an ethanol–water solution of pyrrole (Py), followed by the polymerization of the coated Py in ammonium persulfate (APS) solution. The PPy-decorated Ni foams and commercial activated carbon (AC) modified Ni foams were employed as the two electrodes for the assembly of flexible all-solid-state asymmetric supercapacitors. The sheet-like structure of PPy and the macroporous feature of the Ni foam, which render large electrode–electrolyte interfaces, resulted in good capacitive performance of the supercapacitors. Moreover, a high energy density of ca. 14 Wh kg−1 and a high power density of 6.2 kW kg−1 were achieved for the all-solid-state asymmetric supercapacitors due to the wide cell voltage window.
43
Baughman, Jessi Alan. "Solid-State NMR Characterization of the Structure and Morphology of Bulk Heterojunction Solar Cells". University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1343136219.
Texto completo da fonte
44
Yang, Xiangwen, Zhixing Lin, Jingxu Zheng, Yingjuan Huang, Bin Chen, Yiyong Mai e Xinliang Feng. "Facile template-free synthesis of vertically aligned polypyrrole nanosheets on nickel foams for flexible all-solid-state asymmetric supercapacitors". Royal Society of Chemistry, 2016. https://tud.qucosa.de/id/qucosa%3A30332.
Texto completo da fonteResumo:
This paper reports a novel and remarkably facile approach towards vertically aligned nanosheets on three-dimensional (3D) Ni foams. Conducting polypyrrole (PPy) sheets were grown on Ni foam through the volatilization of the environmentally friendly solvent from an ethanol–water solution of pyrrole (Py), followed by the polymerization of the coated Py in ammonium persulfate (APS) solution. The PPy-decorated Ni foams and commercial activated carbon (AC) modified Ni foams were employed as the two electrodes for the assembly of flexible all-solid-state asymmetric supercapacitors. The sheet-like structure of PPy and the macroporous feature of the Ni foam, which render large electrode–electrolyte interfaces, resulted in good capacitive performance of the supercapacitors. Moreover, a high energy density of ca. 14 Wh kg−1 and a high power density of 6.2 kW kg−1 were achieved for the all-solid-state asymmetric supercapacitors due to the wide cell voltage window.
45
Karlsson, Patrik. "Surface Science Studies of Metal Oxides Formed by Chemical Vapour Deposition on Silicon". Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7088.
Texto completo da fonte
46
Castro, Laurent. "Matériaux d’électrode positive à base de phosphates pour accumulateurs Li-ion et phénomènes aux interfaces : apport de la spectroscopie photoélectronique à rayonnement X (XPS)". Thesis, Pau, 2012. http://www.theses.fr/2012PAUU3046/document.
Texto completo da fonteResumo:
Ce travail de thèse est centré sur l’étude de matériaux LiMPO4 (M=Fe, Mn, Co) et de leur évolution en cyclage (processus rédox et interfaces électrode / électrolyte) dans des accumulateurs Li-ion. Il a été mené essentiellement sur la base d’analyses en spectroscopie photoélectronique à rayonnement X (XPS) couplées à des tests électrochimiques. Une oxydation de surface du phosphate LiFePO4 a été mise en évidence lors d’une exposition à l’air de ce matériau avec la formation d’impuretés de surface type Fe2O3. Au plan structure électronique, l’analyse des bandes de valence des matériaux LiMPO4 (M=Fe, Mn, Co) a notamment permis, pour LiFePO4, la visualisation de l’électron spin down du niveau Fe 3d amenant la première preuve expérimentale de la configuration électronique particulière (3d↑)5(3d↓)1 de Fe2+dans ce matériau. Ce travail a également contribué à mieux comprendre l’influence de la température de fonctionnement ainsi que de la nature de l’électrode négative sur les mécanismes de vieillissement des accumulateurs Li-ion. Pour les accumulateurs LiFePO4 // Graphite, la comparaison d’interfaces solide/électrolyte distribuées spatialement a montré que le vieillissement se caractérisant par la perte de lithium actif pouvait être mis en parallèle avec une hétérogénéité de fonctionnement de l’électrode positive. Enfin, l’extension des travaux aux matériaux prometteurs d’électrode positive Li(FeMn)PO4 a révélé que le potentiel de travail de fin de charge plus élevé pour le phosphate mixte, comparativement à LiFePO4, résultait dans une réactivité accrue vis-à-vis de l’électrolyte dont les conséquences ont été analyséesThis thesis is focused on the study of LiMPO4 (M = Fe, Mn, Co) materials and on their evolution upon cycling (redox process end electrodes / electrolyte interfaces) in lithium ion cells. It is based on X-Ray Photoelectron Spectroscopy (XPS) analyses coupled with electrochemical tests. During air exposure, a surface oxidation of phosphate LiFePO4 was observed that lead to the formation of surface impurities such as Fe2O3. Concerning electronic structure, the analysis of LiMPO4 (M=Fe, Mn, Co) materials valence spectra allowed for LiFePO4 the visualization of spin down Fe 3d electron which is the first experimental proof of the particular electronic configuration (3d↑)5(3d↓)1 of Fe2+ in this material. This work also allowed a better understanding of the effect of the working temperature as well as the nature of the negative electrode on Li-ion cells ageing mechanisms. For LiFePO4 // Graphite cell, the comparison of spatially distributed solid/electrolyte interfaces showed that ageing mechanisms, characterized by a loss of active lithium, could be associated with a heterogeneity of working of the positive electrode. In addition, the extension of these studies on new promising Li(FeMn)PO4 materials for positive electrode showed that higher working potential of mixed phosphate material compared to LiFePO4 material leads to a higher electrolyte reactivity which consequences were analysed
47
Kazeminezhad, Iraj. "Growth and characterization of Niâ†xCuâ†1â†-â†x alloy films, Niâ†xCuâ†1â†-â†x/Niâ†yCuâ†1â†-â†y multilayers, and nanowires". Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391185.
Texto completo da fonte
48
Kadri, Abdelaziz. "Etude electrochimique des processus de corrosion d'un alliage fe-36 ni sous des couches minces d'elecrolyte, a l'air libre ou en situation de confinement". Paris 6, 1986. http://www.theses.fr/1986PA066211.
Texto completo da fonteResumo:
Etude du mecanisme de corrosion localisee observee sur les alliages fe-36ni et intervenant lors de leur stockage par empilement de feuilles destinees a la fabrication de supports de circuits integres. Utilisation d'une cellule de simulation ou l'epaisseur de l'electrolyte est maintenue a une tres faible valeur (
49
Vystavel, Tomas. "Structure de joints de grains dans des bicristaux de molybdène et mouillage de ces joints par du nickel : étude expérimentale par microscopie électronique". Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE10091.
Texto completo da fonteResumo:
La structure de joints de grains de flexion d'axe 110 dans le molybdene et les phenomenes de mouillage de ces joints par le nickel, ont ete etudies. Nous avons utilise des bicristaux de caracteristiques cristallographiques bien definies qui correspondent a des energies de joint differentes et donc a des proprietes differentes. Trois types de bicristaux d'angle differents ont ete observes : les macles coherente et incoherente et un joint de coincidence particuliere (sigma = 11). Les observations experimentales ont ete faites principalement en microscopie electronique conventionnelle, a haute resolution et par spectroscopie de pertes d'energie des electrons. Pour chaque type de bicristal, la structure du reseau de dislocations secondaires a ete determinee par microscopie conventionnelle et par diffraction electronique et interpretee dans le cadre de la theorie de bollmann. Certaines de ces dislocations ont ete observees en haute resolution et leur champ de deformation elastique calcule. La structure a l'echelle atomique de chacun des bicristaux purs a ete determinee par haute resolution. Les resultats sont en tres bon accord avec ceux calcules par simulation numerique, notamment la structure des unites structurales qui composent les differents joints. Les translations rigides paralleles et perpendiculaires au plan de joint ont ete mesurees. Les experiences de mouillage par le nickel ont ete faites a deux temperatures (1350 et 1380 degres c). Selon l'energie du joint, il se forme soit des precipites isoles de phase mo-ni, soit une couche de mouillage tres mince (1nm) et continue le long du joint. La comparaison entre les differents bicristaux montre que le joint de faible energie ne presente pas de mouillage sauf au cur des dislocations secondaires, alors que le joint de forte energie est beaucoup plus fortement mouille. De plus, a la temperature de 1380 degres c, ce joint migre vers une position asymetrique.
50
Labdi, Yamina. "Caracterisation des structures n+in+ minces, a base de sillicium amorphe hydrogene par la methode des courants limites par charge d'espace : prise en compte des effets d'interface". Paris 7, 1988. http://www.theses.fr/1988PA077091.
Texto completo da fonteResumo:
Cette these est principalement consacree a l'etude experimentale et theorique des structures minces du type metal/n**(+)in**(+)/metal a base de silicium amorphe hydrogene. Dans un premier temps, nous nous affranchissons des problemes des resistances parasites dues a la presence des jonctions metal/n**(+), en etudiant ces jonctions de facon detaillee lorsque le metal utilise est de l'oxyde d'etain, du chrome ou de l'aluminium. Nous serons amenes a corriger de facon empirique et si necessaire, les caracteristiques j(v) mesurees afin que celles ci decrivent le comportement de la couche centrale intrinseque. Nous presentons ensuite une nouvelle modelisation du transport des electrons injectes dans de telles structures. Cette modelisation prend en compte la contribution des courants dus a la diffusion des electrons a la densite de courant totale, ce qui permet de tenir compte de facon explicite du comportement des bandes aux interfaces n**(+)/i. L'ensemble des resultats obtenus sur nos echantillons nous mene a conclure que dans le cas de nos mesures, il n'y a pas de signe d'augmentation de la densite d'etats pres des interfaces n**(+)/i. Ces interfaces ne sont pas du tout abrupts mais entierement decrits par la densite des electrons pieges au voisinage du niveau de fermi. Quelques resultats concernant l'alliage si-ge depose au sein de notre laboratoire sont presentes a la fin de ce travail