An in-depth study of concentration gradients in thermally-interdiffused polymer – fullerene photovoltaic devices, with a focus on thickness and heat treatments, is presented in this thesis. Device performance is improved from the bilayer by the creation of a concentration gradient of the donor and acceptor materials throughout the active layer of the device. Concentration gradients are expected to improve device performance by optimizing the charge transfer, transport and collection processes. This is achieved through heat-induced interdiffusion of the two materials at temperatures above the glass transition temperature of the polymer. Investigation of the poly(3-octylthiophene) (P3OT) – C₆₀ system show a three-fold improvement in the external quantum efficiencies (EQE) as compared with bilayer devices. Auger spectroscopy, combined with argon-ion beam milling, serves to record the concentration depth profile and identify concentration gradients in the device through detection of the sulfur in the P3OT backbone. Concentration gradients are optimized to yield the best devices through a thickness variation study conducted on the P3OT – C₆₀ system for fixed thermal interdiffusion conditions at 118 °C for 5 minutes. An optimum thickness of 40 to 60 nm is obtained for the two materials that yields the ideal morphology of a concentration gradient as recorded by Auger spectroscopy. For such devices, the concentration gradient is seen to extend through the device, ending in a thin layer of pure material at each electrode. A monochromatic power conversion efficiency of 2.05% is obtained for 5.3 mW/cm²⁺ illumination at 470 nm. A brief study is also presented to optimize the concentration gradient profile through variations of the thermal parameters. The dependence of the concentration gradient on the interdiffusion time and temperature is investigated. The merits of heat treatment on the crystallinity of P3OT and the overall device performance are also discussed. It is shown in some case that devices with annealed P3OT layers show almost twice the EQE as non-annealed P3OT layer devices. Potential alternatives for C₆₀ in interdiffused devices with P3OT have been presented. [6,6]-phenyl C₆₁-butyric acid methyl ester (PCBM), a well-investigated acceptor for blend devices, is studied as an acceptor in concentration gradient devices. A method for spin-coating uniform bilayers of P3OT and PCBM, without solution damage to either layer, is presented. A thermal variation study of the interdiffusion conditions on this system indicated higher interdiffusion temperatures and times are preferred for P3OT – PCBM systems. For interdiffusion at 150 °C for ten minutes, EQE values approaching 35 % at 500 nm are obtained. Auger spectroscopy studies on this system yielded the same conclusions about the concentration gradient device morphology that gives optimum device output. 1:1 and 1:2 blends of P3OT – PCBM are also studied. The influence of various thermal treatments on these devices is described. The endohedral fullerene Sc₃N@C₈₀ is introduced as a new acceptor material. The endohedral fullerene consists of Sc₃N cluster enclosed in a C₈₀ cage. An order of magnitude increase is seen in device performance upon sublimation of these molecules on a P3OT layer confirming its effectiveness as an acceptor. Preliminary studies done on this system indicated the need for greater thermal treatment to produce optimum concentration gradients. An in depth study for varying temperatures and times is presented. The best device performance was seen for interdiffusion at 160 °C for 25 minutes. The endohedral fullerene devices also show a long-term deterioration and so best result are presented from a set of devices fabricated within the same time period. The study of these three donor-acceptor systems confirms that the conclusions on the thickness dependence and device performance study conducted for the P3OT – C₆₀ system extend to other acceptors. A model of EQE for varying thicknesses based on absorption in the interdiffused concentration gradient regions is also presented. This model effectively highlights the influence of P3OT layer thickness on the trends observed in the EQE. It did not, however, reproduce the experimental thickness variation results for varying C₆₀ thicknesses. Incorporation of the effects of the electric field intensity distribution is expected to correct for this. Suggestions have been given on how this might be achieved. / Ph. D.

Pour comprendre les mécanismes microscopiques du renforcement dans les nanocomposites, nous avons mis en œuvre un système nanocomposite modèle composé de nanoparticules de silice incorporées dans une matrice du copolymère PMMA/PBuA. La formation des échantillons se fait par évaporation du solvant -l'eau- du système colloïdal mixte latex et silice. La structure de la charge peut être contrôlée par le pH et la fraction volumique de la silice. La combinaison de diffusion de neutrons aux petits angles et microscopie électronique à transmission nous a permis d'établir un diagramme de phases du nombre d'agrégation de la silice. Les tests mécaniques en traction uni-axiale sur des nanocomposites de structure définie nous ont donné accès à la relation entre la structure des charges et la rhéologie. L'augmentation du nombre d'agrégation moyen augmente le renforcement du module de Young, et mène à une rupture précoce des films. Un optimum entre fort renforcement et grande déformation avant rupture peut être trouvé en s'intéressant à l'énergie de rupture. Lorsque l'on s'intéresse à la structure des chaînes dans les nanocomposites, il faut créer le contraste moyen nul pour la silice en introduisant des chaînes deutériées D. Nous avons pu suivre l'interdiffusion des chaînes H et D durant le recuit dans deux systèmes. Pour suivre la dissolution des billes de latex dans le polymère fondu, nous avons mis en place une modélisation des données structurales. La présence de la silice limite la mobilité des chaînes dans les nanocomposites. / To improve the understanding of the reinforcement effect in nanocomposites, we have set up a model system made of a latex matrix (PMMA-PBuA copolymer) with incorporated nanosilica beads. The nanocomposite films are made by evaporating the aqueous solvent of mixture of silica/latex colloidal solutions. The structure of the network is well controlled by the pH and volume fraction of silica. We have established a phase diagram of the aggregation number of the silica by small angle neutron scattering and scanning electron microscopy. The rheological properties of silica-latex nanocomposites have been tested by uni-axial stress-strain isotherms and correlated to the silica structure. The increase of the average aggregation number reinforces the Young modulus and decreases the elongation at the breaking point. An optimum has been found by determining the energy needed until rupture. We have studied the chain structure in the nanocomposites by creatin g zero-average contrast conditions for the silica, using mixtures of D- and H-latex. The interdiffusion of the H and D chains during the annealing could be measured in two systems and intermediate structure modelled. The presence of the nanosilica particles reduces the mobility of the polymer chains.

L’objet de ce travail est la description de la dynamique de diffusion dans les polymères à l’approche de la transition vitreuse et notamment les processus de relaxation hors équilibre. Nous développons, pour les mélanges compressibles de polymères et polymère-solvant, un modèle thermodynamique qui permet de calculer les forces thermodynamiques dans des situations hors d’équilibre (formalisme général d’Onsager). La dynamique correspondante repose sur l’existence d’hétérogénéités dynamiques près de Tg dues aux fluctuations de concentration (modèle de Long et Lequeux). Nous avons développé deux méthodes. La première est basée sur une équation de Fokker-Planck décrivant, à l’échelle des hétérogénéités (quelques nm), la distribution des fluctuations de concentration de polymère et de solvant. Après l’étude des mécanismes de relaxation à cette échelle, nous étudions l’échelle macroscopique, pour rendre compte de la pénétration du solvant dans un matériau vitreux ou du séchage d’un mélange polymère-solvant près de Tg. La deuxième méthode consiste en la simulation de ces mécanismes de relaxation par une description spatiale. Celle-ci est basée sur une discrétisation de l’espace, chaque site pouvant échanger du solvant ou des monomères selon une dynamique décrite par des équations de Langevin non-linéaires couplées. Cette dernière méthode est plus générale mais plus coûteuse en temps de calculs. Nous montrons que les résultats obtenus des deux façons sont cohérents. Il s’agit de la première méthode permettant de décrire microscopiquement et quantitativement la diffusion de solvant près et en dessous de la transition vitreuse / The aim of this work is to describe the diffusion dynamics in polymers close to the glass transition (relaxation processes at non equilibrium states). A thermodynamic model for polymer-polymer and polymer-solvent blends is developed. It is able to compute the thermodynamic forces existing at non equilibrium for the mentioned blends (Onsagers formalism). The correspondent dynamic are based upon the existence of thermodynamic heterogeneities close to Tg due to concentration's fluctuations (Long-Lequeux model). Two methods were developed. The first is based on a Fokker-Planck equation which describes, at the heterogeneity scale (i.e. nanometric scale), the distribution of fluctuations of polymer and solvent. Following the study on the relaxation mechanism in the nanometric scale, a microscopic scale was then considered, in order to take in account either the solvent penetration within a glassy material or the drying of a polymer-solvent blend close to Tg. The second method consists in the simulation of the mentionned relaxation mechanisms using a spatial approach. This approach is based on a special discretization, each site being able to exchange solvent molecules or monomers according to the dynamics described by coupled non-linear Langevin equations. This second method is a more general approach. However the calculations related to it are more time-consuming. The results obtained by both methods are in good agreement. This is the very first method able to describe microscopically and quantitatively the solvents diffusion close to or below Tg

In der vorliegenden Arbeit wurden drei unabhängige Problemfelder moderner biophysikalischer und materialwissenschaftlicher Forschung untersucht: Diffusion in binären Legierungen, der Umbauprozess in trabekulärem Knochen und die Voraussage mechanischer Eigenschaften, insbesonders der Biegesteifigkeit, selbstorganisierender, amphiphiler Membrane. Für alle drei Problemfelder wurden Gittermodelle gewählt, um ausgesuchte Fragestellungen zu untersuchen. Für den Fall der Diffusion in Legierungen war dies, inwieweit sich der Diffusionprozess, der sich auf atomarer Ebene als diskrete Platztäusche zwischen Atomen und Leerstellen manifestiert, auf einer größeren, makroskopischen, Ebene mit Hilfe einer kontinuumstheoretischen Theorie beschreiben lässt. Im Fall der Beschreibung des Umbauprozesses in in trabekulärem Knochen wurde die die spongiöse Architektur des Knochens auf ein Gitter abgebildet und mittels einer vereinfachten mechanischen Beschreibung die lokale Belastung in jedem Knochenelement bestimmt. Die zeitliche Entwicklung des Systems wurde mittels eines stochastischen Umbaugesetzes gesteuert, das die Wahrscheinlichkeit für Knochenan- bzw. -abbau als Funktion der lokalen Volumenänderung vorgab. Es wurde gezeigt, dass ein nicht-lineares Umbaugesetz bessere Übereinstimmung mit experimentellen Ergebnissen zeigt, als ein rein lineares. Weiters wurde das Krankheitsbild der Osteoporose untersucht und es konnte eine Unterscheidung zwischen einem normalen Alterungsprozess der Knochenstruktur und einer krankhaften Veränderung gezogen werden. Um die mechanischen Eigenschaften selbstorganisierender Membrane zu bestimmen, wurden linear elastische Federkräfte zwischen benachbarten Molekülen angenommen. Die volle elastische Matrix und daraus die gewünschten Eigenschaften wurden für unterschiedliche Zusammensetzungen der Membrane bestimmt. Es wurde gezeigt, dass die Biegesteifigkeit solcher Membrane in einem begrenzten Konzentrationsbereich um mehrere Größenordnungen variieren kann. / This thesis presents the results of investigations on three independent research topics of modern biophysical and materials science research: substitutional diffusion in binary alloys, the remodelling process in trabecular bone and the prediction of mechanical properties of self assembling, amphiphilic bilayers. The basic description of all three projects is based on lattice models, a highly successful class of models that are used in several fields of modern physics to describe physical processes. For the diffusional process in alloys, which on a microscopic scale manifests in a discrete site exchange between one atom and a neighbouring vacancy, it was investigated how this microscopic description can be reconciled with a macroscopic continuum model. For the investigations on remodelling of trabecular bone, the architecture of bone was mapped onto a lattice and the local mechanical state of each element was determined by a simplified mechanical model. A stochastic description was chosen to model the time evolution of the system, relating the probability of bone formation and resorption, respectively, to the local volume changes of the bone elements. It was shown that a non-linear remodelling law is a better candidate to describe the remodelling process in real bone than a linear one. Furthermore, applying the model to osteoporosis - a wide spread bone disease - it was shown that in the features attributed to osteoporosis one has to distinguish between normal ageing of bone''s architecture and additional changes that stem from pathological alterations in the regulatory system. A simple concept was introduced to model the mechanical properties of self-assembled membranes. The molecules forming the membrane are assumed to occupy a triangular lattice, nearest neighbours are connected by linear elastic springs. It was shown that the bending rigidity exhibits a pronounced concentration dependence, varying over orders of magnitude in a narrow concentration regime.

A haute température, l’interdiffusion entre un superalliage et son revêtement protecteur (ß-NiAl ou ß- NiPtAl) dégrade à la fois la protection contre l’oxydation, par modification de la composition chimique du revêtement, et la microstructure du superalliage (3ième et 4ième générations) par formation de Zones de Réaction Secondaires (SRZ). Le but de cette étude a donc été (1) de développer des barrières de diffusion (BD) constituées d’une dense précipitation de phases a-W après traitement sous vide (BD simple) ou chromisation en phase vapeur (BD enrichie en chrome) (2) de mettre au point une méthode pour en étudier l’efficacité. Des mesures de concentration chimique (à partir de cartographies spectrales EDS), couplées à des ajustements des comportements en oxydation cyclique en utilisant le modèle « p-kp », et le développement d’un modèle « p-kp-ß » ont permis de montrer l’efficacité de la BD selon sa composition et la durée de vieillissement. Pour des longues durées de vieillissement, l’efficacité de la BD se réduit par la dissolution des précipités d’a-W dans les phases y’ et y formées à cause de la dégradation des propriétés protectrices du revêtement ß NiPtAl (augmentation de l’écaillage de l’oxyde formé et de la cinétique d’oxydation). Plusieurs causes probables de cette dégradation ont pu être déterminées, soit dues aux procédés (pollution au soufre) soit liées à la mise en place de la BD : augmentation de la transformation martensitique, enrichissement en tungstène et présence de précipités d’alpha chrome. Enfin, il a été montré que si l’initiation des SRZ est modifiée par l’ajout de la BD, leur cinétique de propagation ne l’est pas et est essentiellement dépendante de la composition de l’alliage. Un modèle de propagation des SRZ décrivant les évolutions chimiques locales de part et d’autres de l’interface « SRZ / superalliage » a été proposé. L’ajout de chrome à la BD permet d’inhiber la formation des SRZ, une couche riche en phases TCP remplace alors la SRZ. / At high temperature, interdiffusion between a superalloy and its protective coating (ß-NiAl or ß- NiPtAl) degrades the oxidation protection by modifying the chemical composition of the coating. It also degrades the 3rd et 4th generation superalloy microstructure due to the formation of Secondary Reaction Zones (SRZ). As a consequence, the aim of this study was (1) to develop diffusion barriers (DB) composed of a dense precipitation of a-W phases after a thermal treatment under vacuum (simple DB) or a vapour phase chromisation (Cr enriched DB), (2) to develop a method for quantifying the DB efficiency. Chemical concentration measurements (with EDS spectral maps) coupled with the « p-kp » modelling of the cyclic oxidation kinetics, and the development of the model « p-kp-ß » have permitted to study DB efficiency as a function of its composition and its high temperature ageing. For long ageing duration, the efficiency of the DB is reduced. Indeed, it is shown that the DB degrades the protection character of the ß-NiPtAl by increasing the oxide scale spallation and of its growth kinetic. This, in turns, accelerates the ß to y’ and y phases transformation and then increases the a-W precipitates dissolution. Some likely causes of this degradation have been determined, either due to the process (sulphur pollution) or intrinsic of the DB addition (increase of the martensitic transformation, enrichment in tungsten and a-Cr formation in the coating). Finally, it has been proved that DB addition modifies the SRZ initiation but not their propagation kinetic, which only depends on the superalloy local composition. A SRZ propagation model which describes local chemical evolutions on both sides of the « SRZ / superalloy » interface was proposed. The addition of chromium to the DB permits to inhibit the SRZ formation. In this case, a layer rich in TCP platelets replaces the SRZ.

Le soudage par électrofusion est la technique majoritairement utilisée pour assembler les tubes et les accessoires en polyéthylène utilisés sur le réseau gazier. Ses très bons résultats initiaux ont été ternis ces dernières années par un certain nombre de dysfonctionnements relevés tant sur le terrain qu'en laboratoire. Ils se traduisent par des soudures de qualité médiocre du fait de la présence de zones de très faible cohésion. L'objectif de ce travail est de développer des outils experts tant expérimentaux que numériques permettant d'optimiser les conditions de soudage par électrofusion. L'originalité de notre étude a été de développer un modèle éléments finis tridimensionnel prenant en compte les différents mécanismes et phénomènes physiques sous-jacents, responsables de la formation de la soudure. Le modèle permet de calculer le taux de transformation de la matière, de prendre en compte les enthalpies de fusion et de cristallisation, de calculer le taux d'interdiffusion des macromolécules à l'interface entre les différents corps à souder pour finalement prédire la qualité de la soudure en fonction des conditions de chauffage imposées. Pour valider le modèle numérique, tout en facilitant l'accès aux grandeurs expérimentales, nous avons conçu et réalisé un dispositif expérimental se présentant sous la forme d'une géométrie relativement simple et plane mais respectant les caractéristiques d'un accessoire réel. La confrontation entre résultats numériques et expérimentaux a permis de démontrer les capacités du modèle numérique à reproduire fidèlement la réalité. Les différents outils ont alors été utilisés pour étudier l'influence des conditions de soudage sur la soudure et pour étudier le soudage de géométries plus complexes telles que celles rencontrées dans les pièces industrielles. / The Electrofusion welding process is widely used to join polyethylene components in gas distribution networks. Even trusty as a technique, the field feedback points out some divergences whose influence on the long term performance of the weld. One of the well-known consequences of these divergences is the “sticking” (aka “cold weld”) that is the result of an uncompleted or even inexistent interdiffusion of the macromolecules of the materials to join. Most numerical simulations are two-dimensional whereas the process is usually three-dimensional both in terms of heat transfer and mechanical aspects. The main objective of the work was to develop a 3D finite element model and to validate it by comparing to a real situation the temperature evolution and the thermally affected areas in a simple planar welding geometry with the same dimensional characteristics as a real fitting chosen to make easier the instrumentation. The numerical model takes into account the fitting parameters such as polyethylene thermal and mechanical properties (i.e. melting and crystallization kinetics, phase transition, thermal expansion) and the electrical and geometrical settings. It computes a criterion based on the macromolecular interdiffusion theory able to determine whether a good welding occurred or not at the end of the welding cycle. The computed results (temperature, melted and cold areas and fracture surfaces) were compared with experimental data and gave very good agreement in terms of temperature, liquid phase fraction distribution and fracture surfaces. Finally the numerical model and the experimental process were used to study the influence of welding conditions on the weld itself and to study the welding of complex geometries such as the industrial fittings.

There is potential for improving creep properties of stainless steels by reinforcing them with tungsten (W) wires. Past studies have shown that a detrimental factor that impairs the mechanical properties of tungsten wire reinforced superalloy composites is the formation of brittle intermetallic phases due to the interaction between W wire and constituents of the alloy matrices. Formation and growth of the intermetallic phases strongly depends on the matrix chemistry and for the retention of creep strength, matrix compositions that do not form intermetallic phases with tungsten are desirable for fabricating W wire reinforced composites for high temperature applications. This research investigated the formation and growth of reaction phases in W wire reinforced 316L (W/316L) stainless steel and HP alloy steel (W/HP) that were fabricated by casting method. Additionally, the effect of composition on the evolution and kinetics of reaction phases was studied in some W wire reinforced experimental alloys based on Fe-Ni-Cr only (W/Fe-Ni-Cr). The fabricated composites were diffusion annealed in the temperature range 1000-1200°C for 25-500 hours. Microstructure and chemistry of the reaction phases in the as-cast and diffusion annealed composites were studied using scanning electron microscopy, energy dispersive spectroscopy and electron backscattered diffraction techniques. Growth kinetics of the reaction layers and average effective interdiffusion coefficients in the layers were determined for the composites. Results showed that an intermetallic phase isostructural with µ-phase formed in the as-cast W/316L and W/Fe-Ni-Cr composites with 1 and 2 Fe:Ni matrix ratios. In W/HP a phase M12C with crystal structure similar to η-carbide was formed. These phases developed and formed brittle reaction layers around the W wires during diffusion annealing. A parabolic relationship between the µ-phase and η-carbide growth and diffusion annealing time indicated that the growth of reaction layers was diffusion controlled. In the W/Fe-Ni-Cr composites, formation of intermetallic phases did not occur in the matrices with 0.5Fe:Ni ratio, instead some isolated tungsten particles were observed in the matrix adjacent to the wires after diffusion annealing. In W/Fe-Ni-Cr composites with 1 and 2 Fe:Ni matrix ratio, the growth of µ-phase reaction layers during annealing was observed to be dependent on the matrix composition. It was found that with an increase in the Ni content in the matrix, growth of µ-phase reaction layer decreased. The study presented in this thesis gives first-hand information on phase formation and growth kinetics of the reaction layers in W/316L and W/HP composites. It revealed that the interaction of W with 316L and HP alloy matrices leads to formation of cracked intermetallic and carbide reaction layers which are not desirable in the composites designed for high temperature applications. It has also been shown in this study that in W/Fe-Ni-Cr composites, intermetallic phase formation can be suppressed by increasing Ni content in the matrix. In the composite with high Ni contents in the matrix (0.5Fe:Ni ratio) intermetallic phases do not form even after diffusion annealing at 1200°C. This intermetallic free W/Fe-Ni-Cr composite can further be studied for its creep strength.

Challenges continue to exist in developing a comprehensive theory of diffusion in liquid metals, despite the advancement of several semi-empirical and theoretical models. One major difficulty in developing a theory is that experimental data are not available for many pure metals and binary metal systems, and when they do exist, data are often inaccurate. In addition to challenges with data quality, where deemed reliable, existing data are typically reported over limited temperature and concentration intervals. In this thesis research, interdiffusion data was obtained for the binary Al-Cu system using the solid wire long capillary technique (SWLC), and molecular dynamics (MD) simulation with a concentration-dependent embedded atom method (CD-EAM) interatomic potential. In the SWLC experiments the interdiffusion coefficient was determined at temperatures of 993 K, 1023 K, 1073 K, 1123 K, and 1193 K, over an Al-rich concentration range limited by the liquidus of the binary phase diagram at the given temperature. For liquid Al~100Cu~0 (tracer), Al80Cu20, and Al60Cu40, the interdiffusion coefficient is well described by the Arrhenius relationship D_AlCu=D_0*exp(-Q_0/RT) over the temperature range, with best fit parameter values of Q_0 = 20.85 ± 4.49 kJ/mol, D_0 = 8.21 (+5.4, -3.26) x 10^-8 m^2/s, Q_0 = 34.41 ± 3.71 kJ/mol, D_0 = 2.84 (+1.47, -0.97) x 10^-7 m^2/s, Q_0 = 38.74 ± 8.01 kJ/mol, D_0 = 4.03 (+5.89, -2.39) x 10^-7 m^2/s, respectively. For the MD simulations, a new Al-Cu CD-EAM interatomic potential was developed that is suitable for the study of diffusion phenomena in the liquid state. Self- and interdiffusion coefficients were determined over a temperature interval of 993-1493 K. Simulations are performed for liquid Al99.999Cu0.001 (tracer), Al80Cu20, and Al60Cu40, and interdiffusion is described by Q_0 = 22.81 ± 0.27 kJ/mol, D_0 = 1.04 (+0.03, -0.03) x 10^-7 m^2/s Q_0 = 30.15 ± 0.49 kJ/mol, D_0 = 1.78 (+0.08, -0.08) x 10^-7 m^2/s, Q_0 = 37.01 ± 1.48 kJ/mol, D_0 = 3.29 (+0.52, -0.45) x 10^-7 m^2/s, respectively. The calculated values of the interdiffusion coefficients from the MD simulation are in good agreement with those obtained using the SWLC technique, supporting the accuracy of these new experimental findings. / February 2017

Textured SnO2 films as TCO have been investigated to determine the effect of surface roughness on the performance of CdS/CdTe solar cells. Film roughness was controlled by varying the substrate temperature. Characterization of the SnO2 films has also carried out using AFM measurements. It was found that increase in substrate temperature results in increased roughness of the film. A series of cells were fabricated with different CdS thicknesses to determine the combined effect of SnO2 roughness and CdS thickness. As a part of fabrication process, cells were subjected to different post deposition treatments. It was observed that roughness seems to be critical when CdS remained in the final device is thin. The performance of CdS/CdTe devices fabricated was characterized using J-V and spectral response measurements. It was found that cells with initial CdS thickness of 1000 showed better performance than those with thicker CdS for the same roughness of SnO2. Conversion efficiency of 13.37% was achieved by increasing the SnO2 roughness and depositing thicker CdS initially.

Ce travail de thèse porte sur l'étude de l'interdiffusion et des contraintes dans des systèmes métalliques modèles en couplant la diffraction des rayons X connue pour sa très grande sensibilité aux variations de distances interréticulaires et la modélisation. Les systèmes modèles choisis sont des multicouches Cu/Ni et Mo/V épitaxiées sur MgO. Dans ces deux systèmes le coefficient de diffusion dépend fortement de la concentration ce qui doit donner lieu lors de l'interdiffusion à des profils de concentration très asymétriques. Pour étudier l'évolution des profils de concentration et de distance lors de la cinétique d'interdiffusion, un programme couplant cinétique d'interdiffusion et évolution des spectres de diffraction symétrique coplanaire a été mis en place avec succès. Il s'appuie sur le modèle de Martin (modèle d'Ising cinétique dans l'approximation de champ moyen) pour simuler l'interdiffusion et utilise la théorie cinématique pour calculer le diagramme de diffraction. De plus, il intègre une relation d'élasticité entre champs de déformation et champs de concentration en tenant compte de la cohérence des interfaces. Ce programme a permis d'établir l'existence d'une forte asymétrie de diffusion dans les systèmes Cu/Ni et Mo/V avec des paramètres contrôlant l'asymétrie d'interdiffusion similaires pour les différents échantillons étudiés. De plus ces paramètres sont très proches de ceux donnés par la littérature établies sur des systèmes non contraints. Ce constat indique que le fort état de déformation de ces multicouches n'affecte pas la cinétique d'interdiffusion.