Ionic liquids are molten salts with melting points below 100 °C and they consist entirely of cations and anions. The development of ionic liquids, especially air and water stable types, has attracted extensive attention since they have outstanding physical properties. Part I of the study focused on the pre-electrolysis process performed to remove impurities from the ionic liquid, 1-butyl-1-methyl-pyrrolidinium bis(tri-fluoromethylsulfonyl)imide, ([BMP]Tf2N). Part II investigated the electroreduction of TaF5 and NbF5 from room temperature ionic liquid at 100 °C at a wide range of potentials and different time durations for the purpose of determining the optimal conditions for the electrodeposition of tantalum. The study was carried out using potentiostatic polarization for the pre-electrolysis treatments and electrodeposition and cyclic voltammetry to study the behaviour of the liquid at various stages. Potentiostatic depositions were complemented by scanning electron microscopy (SEM)/energy-dispersive x-ray analysis (EDX), x-ray photoelectron spectroscopy (XPS) and x-ray diffraction (XRD) for characterization of the electrodeposits.

Ionic liquids are molten salts with melting points below 100 °C and they consist entirely of cations and anions. The development of ionic liquids, especially air and water stable types, has attracted extensive attention since they have outstanding physical properties. Part I of the study focused on the pre-electrolysis process performed to remove impurities from the ionic liquid, 1-butyl-1-methyl-pyrrolidinium bis(tri-fluoromethylsulfonyl)imide, ([BMP]Tf2N). Part II investigated the electroreduction of TaF5 and NbF5 from room temperature ionic liquid at 100 °C at a wide range of potentials and different time durations for the purpose of determining the optimal conditions for the electrodeposition of tantalum. The study was carried out using potentiostatic polarization for the pre-electrolysis treatments and electrodeposition and cyclic voltammetry to study the behaviour of the liquid at various stages. Potentiostatic depositions were complemented by scanning electron microscopy (SEM)/energy-dispersive x-ray analysis (EDX), x-ray photoelectron spectroscopy (XPS) and x-ray diffraction (XRD) for characterization of the electrodeposits.

Les systèmes Cu /Ni-P/Au sont utilisés comme contacts électriques car ils présentent une conductivité électrique élevée, alliée à un bon comportement mécanique et une résistance à la corrosion. Le Cu possède une conductivité électrique unique qui en a fait le métal le plus utilisé en électronique. Cependant, sa faible résistance à la corrosion nécessite l’application de revêtements protecteurs. Les sous couches de Ni (généralement Ni-P) permettent essentiellement d’éviter la diffusion entre Cu et Au. Enfin, la couche de finition en Au est utilisée pour garantir la durée de vie des contacts électriques. Pour des raisons économiques, ce film de faible épaisseur est poreux, entrainant ainsi un couplage galvanique entre l’Au et le Ni au détriment du nickel. Ainsi ce travail est dédié à l’identification et la mise en œuvre des stratégies visant à améliorer la durée de vie des contacts électriques et plus globalement des modules électroniques.Lors de cette thèse, nous avons développé 3 stratégies : (1) améliorer les propriétés de la couche barrière de Ni, (2) remplacer l’or par un métal moins onéreux, (3) sceller les pores de la couche d’Au les propriétés du film barrière Ni-P améliorées notamment par des additifs tels que la glycine. Sn a également imposé un effet similaire. D’autres couches de finition nobles NiAg et NiPd ont été étudiées. Bien que des films hautement adhésifs aient été formés par potentiel pulsé, ces films poreux n'offraient pas un comportement correct à la corrosion. Enfin, il a été découvert que les pores de la couche de finition en Au peuvent être efficacement scellés par électrodéposition de poly méthacrylate de méthyle / Cu/Ni(Ni-P)/Au systems are used as electrical contacts due to their combination of electrical conductivity, corrosion resistance, and mechanical behavior. Cu has a unique electrical conductivity that made it the most used metal in electronics. However, protective coatings must be applied on Cu due to its poor corrosion resistance. Au films are used to secure a proper lifetime of electrical contacts. Ni films are essential to avoid the diffusion of Cu into Au. Electrodeposition is the method of choice to form these multi-layer systems. The Au top-coat is notably thin and hence porous. The corrosive media penetrate through these pores, hence electrical contacts are suffering from a galvanic coupling. This work is dedicated to identify and test the strategies to enhance the lifetime of electrical contacts and electronic modules. Three strategies were detected, (1) improve the properties of the Ni barrier layer, (2) replacing the Au film with a thicker but cheaper alternative metal, and (3) seal the pores of Au top-coat using a post-treatment process. It was found out that the properties of the Ni-P barrier film can be notably improved by additives such as glycine. Sn also found to be highly advantageous for forming NiSn barrier coatings. NiAg and NiPd noble top-coats were investigated as alternatives to Au thin films. Although highly adhesive films were formed using the pulse deposition, the films were porous and thus did not offer a proper corrosion behavior. And finally, a cathodic electropolymerization was employed as a post-treatment method. It was found out that the pores of Au top-coat can be effectively sealed by the electrodeposition of polymethyl methacrylate

Cyclic voltammetry experiments were performed to compare the electrodeposition characteristics of bismuth on ruthenium. Two types of electrodes were used for comparison: a Ru shot electrode (polycrystalline) and a thin film of radio-frequency sputtered Ru on a Ti/Si(100) support. Experiments were performed in 1mM Bi(NO3)3/0.5M H2SO4 with switching potentials between -0.25 and 0.55V (vs. KCl sat. Ag/AgCl) and a 20mV/s scan rate. Grazing incidence x-ray diffraction (GIXRD) determined the freshly prepared thin film electrode was hexagonally close-packed. After thermally oxidizing at 600°C for 20 minutes, the thin film adopts the tetragonal structure consistent with RuO2. a hydrated oxide film (RuOx?(H2O)y) was made by holding 1.3V on the surface of the film in H2SO4 for 60 seconds and was determined to be amorphous. Underpotential deposition of Bi was observed on the metallic surfaces and the electrochemically oxidized surface; it was not observed on the thermal oxide.

This work demonstrates the deposition of molybdenum in a deep eutectic solvent for the first time, and explores the processes needed for electrorefining of molybdenum. The electrochemical and transport behavior of chloride-coordinated molybdenum in ethaline was initially studied to determine if deposition was possible. Cyclic voltammetry was used to show that MoCl5 added to ethaline exhibits quasi-reversible behavior. Both the measured transfer coefficient and the precipitation of MoCl3 suggest that the reduction of MoCl5 in ethaline is a two-electron transfer reaction where the oxidation state of molybdenum in the product is Mo(III). No deposit was formed with the use of MoCl5 alone and the presence of a shuttling reaction may be partly responsible for the lack of a deposit. However, the deposition of molybdenum was accomplished in ethaline at 80 °C by altering the speciation of the metal complex with the introduction of fluoride ions. A change in coordinating ligands in the presence of fluoride was evidenced by a change in the electrochemical behavior of the Mo species, as determined with cyclic voltammetry. Chronoamperometry was then used to produce Mo deposits on nickel substrate in the presence of fluoride ion. The deposits were imaged with SEM and the presence of Mo was confirmed with EDX. In order to study the effect of the newly introduced fluoride ion on the anodic dissolution of molybdenum in ethaline, linear sweep voltammetry was used. In addition, a chloride-free electrolyte composed of 1M KF in ethylene glycol was used to anodically dissolve Mo at a faradaic efficiency of 63%. The ability of Mo to be anodically dissolved in the presence of fluoride showed the addition of fluoride enables Mo deposition without significantly hindering the anodic dissolution of Mo. Thus, both dissolution and deposition of molybdenum are possible in a deep eutectic solvent, opening the way for possible development of a Mo electrorefining process.

The purpose of this study is to investigate the varying conditions in types of solutions, concentrations of solutions, hydrogen-ion concentration, current densities and potentials in the electro deposition of nickel.

Des études expérimentales et théoriques du mécanisme d'électrodéposition de différents revêtements à base de cobalt : le cobalt métallique, les alliages binaires Co-Ni, Co-Cu et l'alliage ternaire Co-Ni-Cu sont menés.Les propriétés de ces films dépendent fortement des paramètres expérimentaux tels que le pH de l'électrolyte, la nature du substrat, etc.. Un champ magnétique jusqu'à 12T est superposé parallèlement à la surface de l'électrode de travail. La convection forcée induite dans l'électrolyte modifie les conditions hydrodynamiques et par conséquent, influe sur la structure et la morphologie des films obtenus. Par ailleurs, la cinétique des processus et la croissance des cristaux sont améliorées dans des conditions magnéto électrochimique. Les microstructures obtenues suite au procédé électrochimique en présence d'un champ magnétique sont caractérisées par différentes propriétés magnétiques trouvant un intérêt potentiel en tant que matériaux magnétiques doux et / ou dur. Dans le cadre du projet ANR COMAGNET, les matériaux subissent ensuite un traitement thermique en présence d'un champ magnétique, des phénomènes de recristallisation et interdiffusion sont mis en évidence induisant des modifications des propriétés magnétiques.Enfin, des calculs de l'énergie d'adsorption de l'atome d'hydrogène et de l'ion H+ sur différentes faces cristallographiques du cobalt sont menés par modélisation DFT (Théorie de la Fonctionnelle de la Densité). Ces résultats, mis en relation avec l'étude expérimentale, montrent le lien entre la formation de certaines structures cristallographiques et l'évolution simultanée de l'hydrogène à la surface de l'électrode pendant l'électrolyse. / The present work is focused on the experimental and theoretical studies of the electrodeposition mechanism of Co-based films, including single Co, binary Co-Ni, Co-Cu and ternary Co-Ni-Cu alloy films. The modeling and structure-properties relationship by a multi-scale approach is investigated.The preliminary study involves determination and optimization of the electrodeposition parameters in order to obtain nanocrystalline films with satisfied surface quality and promising magnetic properties. It is shown that the electrolytic pH, to-be-deposited type of substrate and deposition time are of high importance in the fabrication of nanoscale materials. Among them, the electrolytic pH is the one, which has the greatest effect on the structure formation. The film growth as well as its quality can be strongly affected by a superimposition of an external magnetic field. The electrodeposition process was carried out under parallel to the electrode surface magnetic fields with magnets strength up to 12T. The results reveal that the induced forced convection in the electrolyte changes the hydrodynamic conditions and thus, affects the structure and morphology of the obtained films. Furthermore, the process kinetics and crystal growth are enhanced under magnetic electrodeposition conditions.Microstructure formed by the electrochemical processing is characterized by some significant magnetic properties, which may result in soft and/or hard magnetic materials, depending on their application approach. Additionally, the microstructure of films has been improved by the magnetic annealing treatment. Thus, the recrystallization and interdiffusion phenomena are observed, and modification of the magnetic properties is induced.Considering the electrodeposition process carried out in aqueous solutions the secondary process, which is the hydrogen evolution reaction (HER), needs to be taken into account. The theoretical study based on the tools of quantum mechanics (QM) and density functional theory (DFT) is used to determine the adsorption energies of hydrogen. In this work, the calculation results are related with the experimental study and may explain the structure formation assisted by the simultaneous evolution of hydrogen at the electrode surface.

La technologie de piles à combustible PEM (Proton Exchange Membrane) voit encore sa commercialisation limitée du fait de son coût élevé. L'un des éléments les plus coûteux est le catalyseur, constitué de platine, métal noble, représentant 25 % du coût global. L'étude mise en place dans le cadre de cette thèse s'oriente vers l'amélioration de l'utilisation de cet élément. La voie de nanostructuration s'avère d'un intérêt majeur afin de maintenir des tailles de structure proposant des propriétés électrocatalytiques intéressantes. De plus, l'élaboration électrochimique de catalyseurs présente l'avantage majeur de remplir l'une des conditions nécessaires en pile à combustible : le contact électronique. La réunion des deux précédents points nous a permis de mettre en place un procédé d'élaboration électrochimique de nanostructures, ensuite charactérisées par méthodes électrochimiques et physiques afin d'évaluer et de comprendre leurs propriétés catalytiques. / A key point for the Proton Exchange Membrane Fuel Cell (PEMFC) improvement and commercialization is the enhancement of mass specific electroactivity of platinum to reduce the cost (about 25% of the overall cost). The study set up as part of this thesis is directed towards improving the use of this element. Nanostructuration is of major interest to maintain the size structure offering interesting electrocatalytic properties. In addition, the development of electrochemical catalysts has the major advantage of satisfying the necessary conditions in fuel cell: the electronic contact. We propose an innovative process to elaborate a metal nanowires array on microporous substrate which allows gas diffusion by a simple electrodeposition method. As-made structures had been physically and electrochemically characterized to evaluate and understand their electrocatalytic activity.

No description available.

Projections of the World Energy Council indicate a significant increase in global energy consumption in the medium and long term due to a growing world population and rising prosperity whilst global fossil fuel reserves are in decline. Eighty percent of the world’s energy consumption is generated from fossil fuels and this is unlikely to change in the short and medium term inevitably leading to energy shortfalls. The CO2-less energy of nuclear fuel shows strong potential to meet the future energy demands. However economic, politic and environmental requirements mean that the nuclear industry must adapt its current technology and present fuel usage. A pyroelectrochemical reprocessing system utilising liquid cathode technology could provide an efficient and secure reprocessing cycle essential for reduction in volume and toxicity of nuclear waste and extension of natural nuclear resources. The electrochemistry of aqueous copper(II) and zinc(II) chloride was studied upon a liquid mercury cathode using cyclic voltammetry. Bulk deposition of the Cu upon the liquid mercury cathode was studied using both amperometry and Electrochemical Impedance Spectroscopy. The surface deposits formed by copper deposition upon the mercury liquid cathode were analysed using x-ray powder diffraction and determined to be the rare naturally occurring mineral Belendorffite, Cu7Hg6. Electrochemical diagnostics for surface deposition upon the mercury liquid cathode surface were investigated as a potential analogue system for high temperature liquid cathode systems. Bulk deposition investigation of lanthanum upon the high temperature bismuth system demonstrated transfer of EIS diagnostics for surface growth, with the system demonstrating a similarity to the zinc-mercury ambient system. An electrochemical technique for purifying LiCl/KCl molten salt using an electrolysis technique was demonstrated. The electrochemical cleaning method forgoes the standard chemical treatments that can leave contaminants within the treated salt and results in a cleaner less oxidising molten salt eutectic.