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Ce travail vise à améliorer la description à l'échelle du nanomètre des sols argileux expansifs en utilisant la théorie de la fonctionnelle de densité (DFT). L’eau n’est plus considérée comme un solvant continu mais comme un fluide de molécules polaires individuelles. L'objectif est de reproduire les résultats issus de l'expérience ou de la modélisation numérique tels que la présence de couches d'eau discrètes dans l'espace interfolaire ou la variation de la pression de disjonction avec la distance interfolaire dans le régime de gonflement cristallin. Différents phénomènes physiques de complexité croissante sont successivement étudiés. La taille finie des molécules d'eau est tout d'abord prise en compte en modélisant l'eau comme un fluide de sphères dures traité par la théorie fondamentale de la mesure. La nature polaire du solvant est ensuite implicitement considérée en utilisant un potentiel intermoléculaire de Lennard-Jones pour reproduire les différents types d'interactions de Van der Waals. La nature dipolaire de l'eau est ensuite explicitement modélisée par un fluide dipolaire de sphères dures. Ces deux derniers modèles utilisent une approche perturbative de la théorie de la fonctionnelle de densité dans laquelle les effets de corrélation entre les molécules du fluide sont incorporés. Les ions sont finalement ajoutés afin de compléter la description de la double couche électrique. En vue d'une application au génie civil, l'expression améliorée de la pression de disjonction à l'échelle nanométrique est incluse dans une forme modifiée du principe de Terzaghi appliqué aux argiles expansives non-saturées récemment développée dans notre groupe afin de simuler numériquement le comportement hydro-mécanique des argiles gonflantes lors d’essais d'infiltration d’eau / This work aims at improving the nanoscale description of expansive clayey soils using the Density Functional Theory (DFT). Water is no longer considered as a continuous solvent but as a fluid of individual polar molecules in order to recover existing experimental and modeling results such as the presence of discrete water layers in the interplatelet space or the variation of the disjoining pressure with the interplatelet distance at low hydration level. Different physical phenomena of increasing complexity are successively considered. The finite size of the water molecules is firstly taken into account by modeling water as a Hard Sphere fluid using the Fundamental Measure Theory. The polar nature of the water solvent is then implicitly taken into account through a Lennard-Jones potential averaging the different types of Van der Waals interactions. Next the polar nature of the solvent is explicitly modelized by considering water as a Dipolar Hard Sphere fluid. These two fluid models are studied in the framework of the Density Functional Perturbation Theory in which correlation effects between the fluid molecules are incorporated. Ions are finally added in order to complete the Electrical Double Layer description at the nanoscale. With the objective of an application to civil engineering, the improved expression of the disjoining pressure at the nanoscale is included in a modified form of Terzaghi's effective stress principle for unsaturated expansive clays recently developed by our group in order to numerically simulate the hydro-mechanical behavior of expansive clays during water uptake

L’objectif de cette thèse est la conception de biocapteurs capables de détecter la présence de séquences d’ADN sans utilisation de marqueurs chimiques ou de traitement préalable de l’échantillon. Le principe de mesure utilise la spectroscopie d’impédance pour la détection du changement provoqué par la présence de la séquence ADN sur le biocapteur. Notre étude s’appuie sur des simulations analytiques et numériques pour définir les dimensions des capteurs adaptés aux mesures en basse fréquence ainsi que le développement d’un modèle de circuit équivalent qui prend en considération les effets d'interfaces. La fabrication du capteur a été réalisée en plusieurs étapes. Dans un premier temps, la conception et la fabrication en salles blanches ont été optimisées pour des structures interdigitées avec différentes géométries et différents types de substrat (Verre, Si, SiO2). Après la validation du modèle, par des mesures sur des solutions de conductivité étalon et sur plusieurs concentrations d’ADN, l’analyse des résultats nous a conduits à proposer une nouvelle structure à électrodes concentriques mieux adaptée aux mesures d’impédance en basses fréquences pour des milieux liquides. Deux prototypes de taille micrométriques, l’un à électrode interdigitée et l’autre à électrode concentrique ont été développés pour une étude comparative / The objective of this thesis is the conception of a biosensor able to detect the presence of DNA sequences without any use of chemical markers or a prior treatment of the samples. The measurements are performed using impedance spectroscopy technique to detect the changes caused by the presence of DNA sequences on the biosensor. Our study is based on analytic and numeric simulations, which allows us to define the dimensions of the sensors adapted to low frequency measurements and to propose an equivalent circuit model taking into account the effects of the electrical double layer. The sensor was manufactured in several steps. Initially, clean room design and manufacturing were optimized for interdigitated structures with different geometries and substrate types (Glass, Si, SiO2). The data analysis of the measurement on standard conductivity and on several DNA concentrations using interdigitated electrode biosensor, allows us to propose a new design with concentric electrodes which is more adapted to low frequency impedance measurement according to a comparative study between interdigitated and concentric electrodes

The classical theory of colloids and surface science has universally been applied in modeling and calculations involving solid-liquid interfaces encountered in natural and engineered environments. However, several discrepancies between the observed behavior of charged solid-liquid interfaces and predictions by classical theory have been reported in the past decades. The hypothesis that the mean-field, pseudo-one-component approximation adopted within the framework of the classical theory is responsible for the differences observed is tested in this work via the application of modeling and experimental techniques at a molecular level. Silica and silicon nitride are selected as model charged solid surfaces, and mixtures of symmetric and asymmetric indifferent and non-indifferent electrolytes are used as liquid phases. Canonical Monte Carlo simulations (CMC) of the electrical double layer (EDL) structure of a discretely charged planar silica surface, embedded in solutions of indifferent electrolytes, reveal the presence of a size exclusion effect that is enhanced at larger values of surface charge densities. That effect translates into an unexpected behavior of the interaction forces between a charged planar surface and a spherical particle. CMC simulations of the electrostatic interactions and calculations of the EDL force between a spherical particle and a planar surface, similarly charged, reveal the presence of two attractive force components: a depletion effect almost at contact and a long-range attractive force of electrostatic origin due to ion-ion correlation effects. Those two-force components result from the consideration of discreteness of charge in the interaction of solid-liquid interfaces, and they contradict the classical theory predictions of electrostatic repulsive interaction between similarly charged surfaces. Direct interaction force measurements between a charged planar surface and a colloidal particle, performed by atomic force microscopy (AFM), reveal that, when indifferent and non-indifferent electrolytes are present in solution, surface charge modification occurs in addition to the effects on the EDL behavior reported for indifferent electrolytes. Non-uniformity and even heterogeneity of surface charge are detected due to the action of non-indifferent, asymmetric electrolytes. The phenomena observed explain the differences between the classical theory predictions and the experimental observations reported in the open literature, validating the hypothesis of this work.

This work deals with the preparation of liquid electrolytes from different types of aprotic solvents with the aim of their application as electrolytes in electrochemical supercapacitors. Different sorts of aprotic solvents have been chosen, in which the following forms of salts were used: LiBF4, LiClO4,LiPF6. In the next part of the work, the properties of these solvents were measured and the best electrolyte, according to the biggest possible capacity of the system, was chosen. In the theoretical part of this work, the physical principle of supercapacitors and their propeties are described. It deals with electrolytes, their division and with the properties that are appropriate for supercapacitors. The experimental part of the work describes the process of preparation of the samples of electrodes, electrolytes and the techniques of measuring their capacities.

La corrosion des aciers dans les ouvrages en béton armé due aux chlorures est l’une des principales causes de dégradation des constructions notamment en façade maritime. La prédiction de la durée de vie des constructions vis-à-vis de cette pathologie, nécessite la compréhension des principaux mécanismes liés au transfert de chlorures surtout dans les matériaux insaturés (soumis au marnage ou au brouillard salin). Pour améliorer les travaux qui existent dans la littérature sur le sujet, les principaux objectifs de cette thèse sont : la caractérisation expérimentale du phénomène de double couche électrique (DCE) et l’étude de son influence sur le transfert ionique, l’étude des effets de la température et de l’hystérésis (sorption-désorption) sur le profil de chlorures, l’étude du couplage entre corrosion des aciers et transfert des chlorures. Pour atteindre ces objectifs, le travail est divisé en quatre parties. La première est consacrée à l’approche théorique du problème pour établir les équations permettant de décrire le couplage entre transferts ionique et hygrothermique dans les matériaux insaturés. La prise en compte de la DCE est également explicitée. La deuxième partie est expérimentale, elle est réalisée sur des éco-bétons fabriqués à base de laitier et de cendres volantes. Elle consiste à quantifier les paramètres d’entrée du modèle identifiés lors de la première partie. Il s’agit : de la porosité, de la perméabilité aux gaz, du coefficient de diffusion d’ions chlorures, de la distribution porale, des isothermes d’interactions chimiques et des isothermes de sorption-désorption et du potentiel Zeta caractérisant la DCE. Dans la troisième partie, les équations de transfert traduisant le modèle sont résolues numériquement. L’étude de sensibilité du modèle vis à vis de la DCE, de la température, de la perméabilité à l’eau est réalisée. Une confrontation des résultats du modèle (profil de chlorures) avec des résultats expérimentaux obtenus en situation de marnage a permis de montrer l’intérêt de considérer l’hystérésis des courbes de sorption-désorption. Quant à l’effet de la DCE il se manifeste pour potentiel Zeta dépassant 25mV. La dernière partie concerne l’étude du couplage entre transfert de chlorures et corrosion des aciers. Les estimations de la durée d’incubation, de la perte de section d’acier, les temps requis pour l’apparition des premières fissures et l’éclatement du béton d’enrobage ont été réalisées. Nous avons montré que l’utilisation de la loi de Fick peut sous-estimer ces grandeurs. / The corrosion of steels in the reinforced concrete structures caused by chlorides is one of the main causes of degradation of the constructions in particular in maritime facade. The prediction of the service life of the constructions towards this pathology requires the understanding of the main mechanisms relating to the chlorides transport especially in the unsaturated materials submitted to the tide or to the salt spray. To improve the works of the literature, the main objectives should be accomplished are : to study the experimental characterization of the electrical double layer (EDL) and to study its influence on the ionic transport ; to research on the temperature effect and the hysteresis effect on the chloride profile ; to examine chloride transfer coupled with corrosion of reinforcement. To reach these objectives, the work is divided into four parts. The first one is dedicated to the theoretical approach of the problem to establish the equations allowing describing the coupling between ionic and hydrothermal transfer to the unsaturated materials. The consideration of the EDL is also clarified. The second part is experiment. It is realized on eco-concretes made on base of slag and fly ash. It consists in quantifying the inputs of the model identified during the first part such as: porosity, gas permeability, chloride diffusion coefficients, pore size distribution, chemical interactions, isotherms of sorption-desorption and the Zeta potential characterizing the EDL. In the third part, the transfer equations translating to the model are numerically resolved. The study of model sensibility according to EDL, the temperature, the water permeability is performed. A comparison between the numerical results (chloride profile) obtained with the model with experimental ones obtained in the case of tidal zone allowed shows the interest to consider the hysteresis effects. Also, it is shown that the EDL effect is significant beyond Zeta potential of 25mV. The last part concerns the study of the coupling between chloride transfer and corrosion of steels. The estimations of the duration of incubation, the loss of section of steel, the times required to cover cracking were examined. The result showed that the use of the law of Fick can underestimate these parameters.

Poor settling of solids increases land requirement for tailings containment and imposes severe constraints on the water balance. Consequent to these considerations, the alternating current electrocoagulation (AC/EC) technique emerged as a candidate for enhancing the settling behaviour of suspensions in the mineral, coal and oil sands industries. Hence, a fundamental study of AC/EC was undertaken with aluminum electrodes. Ground silica (d50 = 20 m), which formed a stable suspension, served as the model tailings solid at 5.0 wt % in water. The AC/EC process consisted of two developmental stages: coagulation, marked by pH decrease in the silica suspension; and floc growth, characterized by pH increase from the minimum (i.e., the end of coagulation). AC/EC enhanced the initial settling rate of silica by over three orders of magnitude, and exhibited remarkable flexibility by virtue of the wide range of process parameters that could be optimized. For example, AC/EC can be operated in either the indirect or direct mode. The settling behaviour of bentonite (estimated d50 < 1 m) was more enhanced by indirect AC/EC, while that of silica benefited more from direct AC/EC. Any condition that increased aluminum dosage (e.g., current, retention time), increased the initial settling rate of silica. Over the feed water pH range of 3.0 to 9.1, AC/EC was effective in enhancing the settling behaviour of silica. AC/EC was also effective over a wide range of temperatures (23 to 85C). High electrical energy demand by AC/EC was observed throughout this study. Its optimization was beyond the scope of this work. Dilution of a sample of Syncrude mature fine tailings (MFT) to 4.6 wt % solids sustained a stable suspension. Settling occurred after AC/EC treatment, a crystal-clear supernatant resulted and bitumen was recovered as froth. Entrained solids were easily spray-washed from the froth with water. The settling behaviour of a Luscar Sterco fine coal tailings sample was not augmented by AC/EC, possibly due to contamination by the companys own electrocoagulation operation. After having been stored dry for more than a year, electrocoagulated silica was an effective coagulant for as-received silica and Syncrude MFT. / Chemical Engineering

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Electrochemical capacitors or supercapacitors or ultracapacitors are potential energy storage devices that could help bringing major advances in future energy storage applications. Unlike batteries that store energy in chemical reactants capable of generating charge, electrochemical capacitors store energy directly through charge separation. Most electrochemical capacitors rely on carbon-based structures utilizing electrical double-layer capacitance effect. By contrast, a pseudocapacitor relies on charge stored due to fast faradaic charge-transfer processes with surface atoms. A combination of faradaic and non-faradaic components would generate hybrid electrochemical capacitors or hybrid ultracapacitors that attain high capacitance for pulse power and sustained energy. This thesis comprises studies pertaining to design, development and applications R&D on substrate-integrated lead-carbon hybrid ultracapacitors. The thesis comprises ten chapters. Chapter 1 is a brief introduction on essentials of electrochemical capacitors explaining their operating principles, classification and applications. Chapter 2 describes studies on materials for electrical double-layer capacitors. Activated carbons are the most common materials for electrical double-layer capacitors. Various activated carbon samples are screened as suitable materials for electrical double-layer capacitor followed by their optimization under varying experimental conditions to form the negative plate in the substrate-integrated lead-carbon hybrid ultracapacitor. Chapter 3 deals with the studies on design and development of 2 V substrate-integrated lead-carbon hybrid ultracapacitors with flooded, absorbent-glass-mat and silica-gel sulfuric acid electrolyte configurations. Lead-carbon hybrid ultracapacitors comprise substrate-integrated lead dioxide sheets as positive plates and high surface-area-carbon-coated graphite-sheets as negative plates. Operating principle for 2 V lead-carbon hybrid ultracapacitors is explained and optimization of their operating conditions along with their electrochemical performance is studied. Chapter 4 is a study on the integration of 2 V substrate-integrated lead-carbon hybrid ultracapacitors to 12 V devices. 12 V substrate-integrated lead-carbon hybrid ultracapacitors with flooded, absorbent-glass-mat and silica gel sulfuric acid electrolyte are developed by connecting six 2 V cells in series. These hybrid ultracapacitors exhibit high power-density values and excellent cycle-life. The problem of uneven performance among the six 2 V cells in the 12 V hybrid ultracapacitors is addressed and resolved by applying voltage-management cell-balancing circuitry. Chapter 5 details the studies on kilo-Farad range 12 V substrate-integrated lead-carbon hybrid ultracapacitors. The hybrid ultracapacitors are performance tested through a standard protocol. Thermal runaway in these hybrid ultracapacitors at high load currents is studied by thermal imaging. Studies on performance comparison between 12 V lead-carbon hybrid ultracapacitors with substrate-integrated and conventional pasted-positive plates are presented in Chapter 6. For substrate-integrated-positive plate lead-carbon hybrid ultracapacitors, capacitance and energy-density values are lower but power-density values are higher than pasted-positive plate configuration due to their shorter response-time. Accordingly, internal resistance values are lower for substrate-integrated lead-carbon hybrid ultracapacitors. Both types of lead-carbon hybrid ultracapacitors exhibit similar faradaic efficiency and cycle-life in excess of 100,000 pulse charge/discharge cycles with only a nominal loss in their capacitance values. Chapter 7 is a study on the design and development of low-cost substrate-integrated lead-carbon hybrid ultracapacitors using poly-aniline organic metal. The hybrid ultracapacitor employs flexible exfoliated graphite sheets as negative plate current-collectors, which are coated with a thin layer of poly-aniline to provide good adhesivity to activated carbon layer and good substrate-conductivity. These ultracapacitors are estimated to cost about 4 US$/Wh as compared to 20-30 US$/Wh for presently available commercial ultracapacitors. In Chapter 8, an application R&D study on the suitability of a substrate-integrated lead-carbon hybrid ultracapacitor bank in powering medical gadgets is described. A practical application that provides 30 W power back-up to medical gadgets for use in grid-power-deficient rural areas is presented. Chapter 9 is another application R&D study in realizing a photovoltaic stand-alone lighting system using substrate-integrated lead-carbon hybrid ultracapacitors. At present, harnessing solar electricity generated through photovoltaic cells with lead-acid batteries remains the most compelling option. But lead-acid batteries have encountered problems in photovoltaic installations, mainly due to their premature failure. To circumvent this problem, substrate-integrated lead-carbon hybrid ultracapacitors are developed for solar energy storage for a lighting application. The last Chapter of the thesis comprises field studies on substrate-integrated lead-carbon hybrid ultracapacitors. In the study, hybrid ultracapacitors are installed for lighting applications for field tests. Grid-power chargers and mechanical dynamos are introduced as fast-charging tools for hybrid ultracapacitors. It is hoped that the studies presented in this thesis would constitute a worthwhile contribution to science and technology of electrochemical capacitors. Considering the technology need, availability, safety and cost, substrate-integrated lead-carbon hybrid ultracapacitors are set to play a seminal role in future energy storage and management.

A l'interface solide-liquide, des réactions physicochimiques conduisent à polariser l'interface et à former la double couche électrique (DCE). La circulation du liquide transporte une partie des charges électriques de la DCE et conduit au phénomène d'électrisation par écoulement. Dans les transformateurs de puissance, constitués, entre autres, d'huile minérale et de carton d'isolement, le phénomène d'électrisation est suspecté d'être à l'origine de certaines défaillances et accidents. Dans cette problématique de risque, de nombreuses études ont été menées et ont permis de mettre en évidence l'influence de paramètres significatifs : nature des matériaux, humidité des matériaux, géométrie et vitesse de l'écoulement, température. Peu d'études se sont concentrées sur l'influence du champ électrique, en particulier les champs continus (DC). Même si le champ électrique généré dans les équipements de puissance est principalement alternatif (AC), il n'en est pas moins vrai que des champs électriques continus (DC) résiduels peuvent être présents, en particulier dans les dispositifs H.V.D.C (High Voltage Direct Current). L'objet du travail s'inscrit dans ce contexte et a pour but, dans une approche à la fois expérimentale et numérique, d'apporter des éléments de réponse sur le développement et le transport des charges de la double couche électrique sous contrainte de champ électrique externe. / At the solid-liquid interface, physicochemical reactions lead to the polarization of the interface and to the formation of an electrical double layer (EDL). The process of flow electrification is due to the convection of part of the electrical charges located in the EDL. In power transformers within which mineral oil and pressboard are commonly used for cooling and electrical insulation, a flow electrification phenomenon is suspected to be responsible of failures. In this hazard assessment problematic, many studies have been made and allowed identifying the influence of significant parameters: nature of materials, moisture level of materials, flow geometry and velocity, temperature. Few studies have focused on the influence of the electric filed, particularly the continuous electric fields (DC). Even though the electric field generated within power transformers is mainly alternating (AC), it is nonetheless true that residual DC electric fields may be detected (e.g. High Voltage Direct Current appartus). This present work fits in this context and aims at providing, both through an experimental and numerical approach, some answers on the development and the transport of charges from the electrical double layer under external electric field stresses.