The polymer gels especially hydrogels have a very special structure and useful features such as unusual volume phase transition, compatibility with biological systems, and sensitivity to environmental stimuli (temperature, pH value, electric field, light and more), which lead to many potential applications in physical and biochemical fields. This research includes: (1) the theoretical and experimental studies of polymer gels on swelling kinetics, spinodal decomposition, and solution convection in gel matrix; (2) applications of polymer gels in wound dressing, tissue-simulating optical phantom and gel display. The kinetics of gel swelling has been theoretically analyzed by considering coupled motions of both solvent and polymer network. Analytical solutions of the solvent and the network movement are derived from collective diffusion equations for a long cylindrical and a large disk gel. Kinetics of spinodal decomposition of N-isopropylacrylamide (NIPA) polymer gel is investigated using turbidity and ultrasonic techniques. By probing movement of domains, a possible time-dependent gel structure in the spinodal decomposition region is presented. Theoretical studies of solution convection in gel matrix have been done and more analysis on dimensionless parameters is provided. To enhance the drug uptake and release capacity of silicone rubber (SR), NIPA hydrogel particles have been incorporated into a SR membrane. This SR/NIPA composite gel has promising attributes for wound dressing and other uses. Tissue-simulating optical phantom has been synthesized and studied using NIPA solution trapped inside a hydrogel. Polymer gels with engineered surface patterns were implemented. NIPA gel deposited on the surface of an acrylamide gel can be used as responsive gel display. A dynamically measurement technique of local shear modulus and swelling ratio of gel is presented based on an engineered periodic surface pattern as square array.

Ce travail de thèse vise à modéliser et simuler la séparation de phase d’un système polymère solvant afin de comprendre, prédire et maitriser la dynamique de formation de membranes poreuses. L’équation phénoménologique proposée de Cahn-Hilliard, couplée à un champ de vitesse (Modèle H dans la classification de Hohenberg et Halperin) sera utilisée pour décrire l’inversion de phase induite par un changement de température (procédé TIPS), le système PMMA/cyclohexanol étant pris comme système de référence.Dans un premier temps, nous nous sommes attachés à étudier de façon systématique l’influence du terme de mobilité sur la dynamique de séparation de phase, sans couplage avec l’hydrodynamique en 2D. Un analyse des lois de croissance des structures formées a été réalisée via une analyse des images par transformée de Fourier et une analyse spécifique des patterns a été effectuée via l’analyse originale des descripteurs de Minkowski. Dans une seconde partie de la thèse, nous avons étudié le couplage entre la séparation de phase et l’hydrodynamique, en 2D et 3D. Enfin, nous avons intégré dans une dernière partie le couplage entre la séparation de phase, l’hydrodynamique et les phénomènes de transferts de matière aux interfaces induits notamment par l’évaporation du solvant au cours de la formation d’une membrane. / The thesis aimed at modeling and simulating the phase separation dynamics of a polymeric system (polymer/solvent or polymer/solvent/non-solvent) for better understanding and controlling the formation mechanisms of porous polymeric membranes. The equation of Cahn and Hilliard (1956)[1] was used and coupled to a hydrodynamic model (H model in the classification of Hohenberg et Halperin (1977)[2]) to simulate the phase inversion in closed system.In a first stage, hydrodynamics was not coupled to Cahn-Hilliard equation and the work focused on the mobility term in the Cahn-Hilliard equation and its influence on the phase separation dynamics (pattern evolution, growth law of the characteristic structures). The patterns were analyzed by Fourier transform and an original analysis was also performed using the Minkowski descriptors.In a second part of the thesis, we coupled the Cahn-Hilliard equations with Navier-Stokes equations and the influence of this coupling on the membrane formation dynamics was investigated.Then, in order to simulate the membrane formation in a context closer to reality, transfer phenomena were simulated at the upper interface of the domain to describe solvent evaporation during demixing process.Finally, the simulations were extended to ternary systems (polymer/solvent/non-solvent) systems since most of industrial polymer membranes involve are prepared from ternary system, with NIPS process (Non-solvent Induced Phase Separation) or dry casting process (differential evaporation between solvent and non-solvent).

Quaternary cubic (TixCr1 − xAl~ 0.60)1 N1 coatings with 0 &lt; x &lt; 0.33 have been grown using reactive cathodic arc evaporation. When adding Ti the hardness was retained after annealing up to 1100 °C which is a dramatic improvement compared to CrAlN coatings. The coatings showed an age hardening process caused by spinodal decomposition into coherent TiCr- and Al-rich cubic TiCrAlN domains and the formation of hexagonal AlN precipitates and cubic TiCrN domains in the vicinity of the grain boundaries. The improved hardness was attributed to the stabilization of the cubic structure suppressing the formation and growth of hexagonal AlN. Furthermore, the presence of Ti atoms generated incoherent nanometer-sized crystallites within the hexagonal AlN precipitates disrupting the hexagonal lattice during the coarsening process. The addition of Ti promoted the formation of a TiO2 layer over Al2O3 resulting in a lower oxidation resistance. However, by tuning the composition it is possible to design coatings to have both good oxidation resistance and good high temperature mechanical stability. / <p>Funding Agencies|SSF project Designed multicomponent coatings, MultiFilms||</p>

In this work, we investigate the relation between the diffusion behavior of Ti1-xAlxN at elevated temperatures and the microstructure. Thinfilm samples are synthesized by reactive co-sputtering with two cathodes. One cathode equipped with Ti target is connected to a highpower impulse magnetron sputtering (HiPIMS) power supply, and the other cathode equipped with Al target is operated with a directcurrent power source. The spinodal decomposition of cubic metastable Ti1-xAlxN controlled by thermally activated diffusion is observe fordiffusion behavior. Various HiPIMS pulsing frequencies are used to achieve different microstructure, while altered power applied to Altarget is used to change the Al content in films. In the phase composition analysis achieved by GI-XRD, the right-shift of (111) film peakalong with increasing Al-power is observed. A saturation of the right-shift and h-AlN peaks are also observed at certain Al-power. Thechemical composition determined by ERDA shows trends of reducing Al solubility limit in metastable phase and O contamination upondecreasing the pulsing frequency. More N deficiency is found in samples deposited with higher frequency. In the 500 Hz and 250 Hzsamples deposited into similar composition and thickness, no apparent difference of the microstructure is observed from the SEM crosssectionalimages. From HT-XRD, we observe higher intensity of TiO2 and h-AlN peaks in 500 Hz sample at elevated temperature ascompared with 250 Hz one. From the reduction of O contamination, denser Ti1-xAlxN films are able to be deposited with lower HiPIMSpulsing frequency. In addition, the higher intensity observed in HT-XRD patterns indicates that the 500 Hz sample is more open todiffusion and therefore allows the new formed phases to grow in larger grains.

Les aciers martensitique inoxydables à durcissement structural sont un des matériaux constitutifs des mats réacteurs d'avion. Cette pièce est soumise aussi bien à des contraintes mécaniques qu'à des contraintes thermiques. Cette dernière engendre le vieillissement de ces aciers, du fait de la présence d'une lacune de miscibilité dans le diagramme Fe-Cr. Deux mécanismes sont possibles dans cette lacune de miscibilité, la précipitation d'une phase riche en chrome α' ou une démixtion suivant un mécanisme de décomposition spinodale. Cette thématique est l'objet du projet PREVISIA financé par l'ANR, dont cette thèse fait partie. Des vieillissements ont été effectués sur l'acier 15 5 PH jusqu'à 15 000 h afin d'étudier la cinétique de vieillissement par décomposition spinodale et son effet sur les propriétés mécaniques de l'alliage en traction, résilience et ténacité. Le vieillissement de l'acier engendre ainsi un durcissement et une fragilisation de l'alliage. De plus, des analyses microstructurales ont permis de mettre en lumière les différents stades de vieillissement, qui correspondent aussi bien à la décomposition spinodale qu'à un complément de phase durcissante. La dureté permet aussi bien de suivre le niveau de vieillissement de l'acier que de déterminer les différentes phases de durcissement. L'effet d'une contrainte appliquée tout au long du vieillissement sur la cinétique de vieillissement a été étudié. Une contrainte de type traction semble ainsi augmenter pour des contraintes élevées le durcissement induit par le complément de précipitation de la phase durcissante, mais aussi accélérer le vieillissement sur les temps de vieillissement plus longs. Une analyse multi échelle est ainsi proposée afin d'expliquer ces différents résultats. / Precipitation hardened martensitic stainless steels are constitutive of aircraft pylons. During there lifetime , these parts are subjected to mechanical loading and work in temperature. This last induces embrittlement of the steels, because of the miscibility gap in the Fe-Cr phase diagram. Two mechanisms are possible to lead to the demixing of the matrix, either precipitation of α', a chromium rich phase, or spinodal decomposition mechanism. This phenomena is the topic of the project PREVISIA, funded by the ANR, this work is part of. Long term agings have been performed on 15 5 PH stainless steel up to 15 000 hours in order to study the aging kinetic and its effect on the mechanical properties in tensile, resilience and toughness. An embrittlement of the alloy is observed. Furthermore, microstructural analyses have been conducted and lead to the definition of different stages of long term aging corresponding to spinodal decomposition and complementary precipitation of hardening phase. Hardness tests is a usefull tool in order to follow the aging and to detect the different stages of aging. The effect of a stress applied during the long term aging has been studied. A tensile stress seems to have an influence on the complementary precipitation of the hardening phase and to increase the rate of hardening. A multi-scale analysise is proposed in order to explain all these results.

A hetero-bimetallic alkoxide CrAl3(OiPr)12 was synthesised through metathesis of achromium(III)chloride THF complex (CrCl3 . 3 THF) and 3 KAl(OiPr)4.It was used as a single sourceprecursor to make oxide powders and films with 1:3 chromium/aluminium compositionthrough sol-gel synthesis. The final materials obtained and heat-treated samples of these wasstudied with thermogravimetric analysis (TG), X-ray diffraction (XRD) and IR spectroscopy. Itwas found that the as synthesised material was amorphous and elementally homogeneousand could be described as hydrated (oxo)-hydroxide with some loosely bonded carbonate,but no organics remaining. Above 600 oC crystallisation starts and eventually splits into twocorundum structured phases starting around 800 oC. At 1400  oC, the phases had joined backtogether in accordance with the Cr-Al-O phase diagram. Scanning Transmission ElectronMicroscopy with Electron Dispersive X-ray (STEM-EDX) tomography showed that the powderswere homogenous up to 800 oC, while after heating to 1000 oC showed chromiumenrichment in some crystals. Gracing Incidence X-ray diffraction (GI-XRD) on spin-coated filmsshowed that epitaxial growth might be achieved based on -Al2O3 (0001) substrate. The results show that the synthesis of the precursor and subsequent oxides was successful andyielded highly homogeneous gels that could be converted into oxide at ca. 600 oC andsubsequently be phase separated through spinodal decomposition at 1000 oC. The next stepwould be to try the precursor in the industrially used chemical vapour deposition (CVD)method.

No description available.

Steepest-entropy-ascent quantum thermodynamics (SEAQT) is a mathematical and theoretical framework for intrinsic quantum thermodynamics (IQT), a unified theory of quantum mechanics and thermodynamics. In the theoretical framework, entropy is viewed as a measure of energy load sharing among available energy eigenlevels, and a unique relaxation path of a system from an initial non-equilibrium state to a stable equilibrium is determined from the greatest entropy generation viewpoint. The SEAQT modeling has seen a great development recently. However, the applications have mainly focused on gas phases, where a simple energy eigenstructure (a set of energy eigenlevels) can be constructed from appropriate quantum models by assuming that gas-particles behave independently. The focus of this research is to extend the applicability to solid phases, where interactions between constituent particles play a definitive role in their properties so that an energy eigenstructure becomes quite complicated and intractable from quantum models. To cope with the problem, a highly simplified energy eigenstructure (so-called ``pseudo-eigenstructure") of a condensed matter is constructed using a reduced-order method, where quantum models are replaced by typical solid-state models. The details of the approach are given and the method is applied to make kinetic predictions in various solid-state phenomena: the thermal expansion of silver, the magnetization of iron, and the continuous/discontinuous phase separation and ordering in binary alloys where a pseudo-eigenstructure is constructed using atomic/spin coupled oscillators or a mean-field approximation. In each application, the reliability of the approach is confirmed and the time-evolution processes are tracked from different initial states under varying conditions (including interactions with a heat reservoir and external magnetic field) using the SEAQT equation of motion derived for each specific application. Specifically, the SEAQT framework with a pseudo-eigenstructure successfully predicts: (i) lattice relaxations in any temperature range while accounting explicitly for anharmonic effects, (ii) low-temperature spin relaxations with fundamental descriptions of non-equilibrium temperature and magnetic field strength, and (iii) continuous and discontinuous mechanisms as well as concurrent ordering and phase separation mechanisms during the decomposition of solid-solutions. / Ph. D. / Many engineering materials have physical and chemical properties that change with time. The tendency of materials to change is quantified by the field of thermodynamics. The first and second laws of thermodynamics establish conditions under which a material has no tendency to change; these conditions are called equilibrium states. When a material is not in an equilibrium state, it is able to change spontaneously. Classical thermodynamics reliably identifies whether a material is susceptible to change, but it is incapable of predicting how change will take place or how fast it will occur. These are kinetic questions that fall outside the purview of thermodynamics. A relatively new theoretical treatment developed by Hatsopoulos, Gyftopoulos, Beretta and others over the past forty years extends classical thermodynamics into the kinetic realm. This framework, called steepest-entropy-ascent quantum thermodynamics (SEAQT), combines the tools of thermodynamics with quantum mechanics through a postulated equation of motion. Solving the equation of motion provides a kinetic description of the path a material will take as it changes from a non-equilibrium state to stable equilibrium. To date, the SEAQT framework has been applied primarily to systems of gases. In this dissertation, solid-state models are employed to extend the SEAQT approach to solid materials. The SEAQT framework is used to predict the thermal expansion of silver, the magnetization of iron, and the kinetics of atomic clustering and ordering in binary solid-solutions as a function of time or temperature. The model makes it possible to predict a unique kinetic path from any arbitrary, non-equilibrium, initial state to a stable equilibrium state. In each application, the approach is tested against experimental data. In addition to reproducing the qualitative kinetic trends in the cases considered, the SEAQT framework shows promise for modeling the behavior of materials far from equilibrium.

Nous réalisons des simulations numériques de décompositions spinodales en dessous de la température de transition vitreuse. Nous étudions l'influence de cette transition sur la séparation de phase liquide-gaz. Ces études ont été motivées pour expliquer un mécanisme de formation de gels à partir de systèmes colloïdaux ayant un potentiel d'attraction à courte portée (systèmes colloïdes/polymères non-adsorbant) mis en évidence lors de récentes expériences mais dont les raisons étaient floues. Nos résultats confirment que la structure des gels est induite par la décomposition spinodale, tandis que l'arrêt de la dynamique due à la transition vitreuse fige le système en une structure bicontinue et empêche la séparation de phase d'arriver à terme. Une étude complète (diagramme des phases, structure, distribution des longueurs, distribution des densités, longueurs caractéristiques, taille des clusters, mécanisme d'évolution) de ces systèmes en fonction du temps, de la température et de la densité est réalisée. / We realize a numerical study of spinodal decomposition under glass transition. We study the influence of glass transition on liquid-gaz phase separation. Our motivation was to explain a gel formation mecanisim of colloidal systems with short range interaction (colloid/non-adsorbing polymer system) shown in recent experiments. Their authors suggested a mecanisim taht we corroborate in this thesis. Our results confirm that gel structure is shaped by spinodal decomposition, and then glass transition slow dynamics until system get pinned in a bicontinuous structure in one hand, and avoid complete liquid-gas separation in other hand. A complete study (phase diagram, structure, length distributions, density distributions, typical lengths, cluster size, evolution mecanisim) of those systems is done in function of time, temperature and density.

<p>The sun provides us daily with large quantities of energy in the form of light. With the world’s increasing demand of electrical energy the prospect of converting this solar light into electricity is highly tempting. In the strive towards mass-production and low cost solar cells, new types of solar cells are being developed, e.g. solar cells completely based on organic molecules and polymers. These materials offer a promising potential of low cost and large scale manufacturing and have the additional advantage that they can be produced on flexible and light weight substrate which opens for new and innovating application areas, e.g. integration with paper or textiles, or as building materials. In polymer solar cells a combination of two materials are used, an electron donor and an electron acceptor. The three dimensional distribution of the donor and acceptor in the active layer of the device, i.e. the morphology, is known to have larger influence of the solar cell performance. For the optimal morphology there is a trade-off between sometimes conflicting criteria for the various steps of the energy conversion process. The dissociation of photogenerated excitons takes place at an interface between the donor and acceptor materials. Therefore an efficient generation of charges requires a large interface between the two components. However, for charge transport and collection at the electrodes, continuous pathways for the charges to the electrodes are required.</p><p>In this thesis, results from morphology studies by atomic force microscopy (AFM) and dynamic secondary ion mass spectrometry (SIMS) of spin-coated blend and bilayer thin films of polyfluorene co-polymers, especially poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5-(4´,7´-di-2-thienyl-2´,1´,3´-benzothiadiazole)] APFO-3, and the fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) are presented. It is shown that by varying the blend ratio, the spin.-coating solvent, and/or the substrate, different morphologies can be obtained, e.g. diffuse bilayer structures, spontaneously formed multilayer structures and homogeneous blends. The connection between these different morphologies and the performance of solar cells is also analysed. The results indicate that nano-scale engineering of the morphology in the active layer may be an important factor in the optimization of the performance of polymer solar cells.</p>