Fármacos pouco solúveis em água são um dos maiores desafios encontrados em formulação de comprimidos, uma vez que, se não adequadamente formulados, podem apresentar problemas de dissolução e de biodisponibilidade. O presente trabalho teve como objetivo produzir comprimidos de glibenclamida 5 mg (hipoglicemiante oral pouco solúvel) utilizando diferentes processos visando a melhoria da dissolução do fármaco e comparar a liberação in vitro (perfil de dissolução) das formulações entre si, bem como em relação ao medicamento referência no Brasil, Daonil®. Foram obtidas 19 formulações por compressão direta empregando dispersão sólida, complexação com ciclodextrina ou micronização do fármaco. Os comprimidos foram analisados quanto ao aspecto, peso médio, dureza, friabilidade, teor e eficiência de dissolução. Os resultados indicaram que, dentre os processos estudados, a utilização de complexos glibenclamida-β-ciclodextrina e glibenclamida micronizada, promoveram uma melhora da dissolução do fármaco. O superdesintegrante Explocel® promoveu significativa melhoria no perfil de dissolução em todas as formulações em que estava presente. A utilização do complexo glibenclamida-β-ciclodextrina com o Explocel® apresentou perfil de dissolução estatisticamente semelhante ao Daonil®, além de atender aos demais requisitos físico-químicos. / Slightly soluble drugs are one of the largest challenges found in tablet formulation, once, if not appropriately formulated, they can present dissolution and bioavailability problems. The present work had as objective to produce 5 mg glibenclamide (practically insoluble hipoglicemic drug) tablets using different processes which aim at enhancing drug dissolution and to compare the in vitro release (dissolution profile) of these formulations with each other as well as with the reference medicine in Brazil, Daonil®. 19 diferent formulations were obtained through direct compression using solid dispersion, cyclodextrin complexion or micronization of the drug. The tablets were also analyzed in relation to aspect, medium weight, hardness, friability, assay and dissolution eficiency. The results indicated that, among the studied processes, an enhancement of the dissolution rate of the drug have arisen from the use of the glibenclamide-β-cyclodextrin complex and the micronized glibenclamide. The disintegrant Explocel® promoted enhancement in the dissolution rate in all the formulations in which it was present. The use of the glibenclamide-β-cyclodextrin complex with Explocel® have presented the best dissolution profile, statistically similar to Daonil®, besides accomplishing the other physico-chemical requirements.

Malgré un large éventail d'applications de la gélatine et en dépit de son utilisation très ancienne, sa composition et sa structure ne sont pas encore entièrement connues et comprises. La gélatine est obtenue à partir de tissus animaux (peaux ou os) et est le résultat de l'hydrolyse partielle du collagène. La production de gélatine la plus abondante est celle de peau de porc qui représentait 46% de la production totale en 2007. Parmi les nombreuses applications, la gélatine de peau de porc est utilisée comme ingrédient principal des gélules dures pour l'industrie pharmaceutique. Une propriété importante de ces gélules est qu'elles fondent dans l'eau à une température au-dessus de 30° C et libèrent facilement les médicaments qu’elles contiennent dans le tube digestif. Les gélules dures doivent répondre à des spécifications de dissolution strictes tout au long de leur durée de conservation d'environ cinq ans. Ainsi, un test de dissolution dans l'eau est appliqué à la gélatine artificiellement vieillie dans des conditions de température et d'humidité élevées. Bien qu'avant le vieillissement le taux de dissolution de la gélatine corresponde toujours aux besoins de l'industrie pharmaceutique, une grande variabilité du taux de dissolution est observée après vieillissement. De plus, cette variabilité de dissolution dépend de l'origine de production de la gélatine. Dans ce contexte, un premier objectif était de comprendre les mécanismes sous-jacents impliqués dans la variabilité de la qualité de dissolution de la gélatine de peau de porc. Un deuxième objectif était d'identifier d'éventuels "marqueurs" de la dissolution de la gélatine afin de prédire son comportement au cours du vieillissement. Trois différents sites de production ont été choisis: deux en Europe et un aux USA. Au cours du vieillissement, la formation de cross-links a été mise en évidence et parmi ces cross-links, la dityrosine a été identifiée comme marqueur du vieillissement. En outre, les taux d'amines et d'aldéhydes ont diminué. Etant donné que ces deux fonctions sont connues pour réagir ensemble; ce résultat suggère qu'elles pourraient former d'autres cross-links au cours du vieillissement. Le processus d'oxydation dans la gélatine a été clairement démontré. De plus, la quantité de triple-hélices et leur stabilité au chauffage ont diminué alors que la quantité de conformation aléatoire et, probablement, de boucles-β augmente. Les résultats ont mis en évidence que l'origine de production affecte la composition chimique de la gélatine. Par exemple, la quantité de cross-links formés, comme la dityrosine, dans les gélatines fraîches et vieillies, différait selon l'origine de production. Nous avons également pu souligner que l'environnement physico-chimique de l'arginine permettait de distinguer l'origine de production de la gélatine. En ce qui concerne la dissolution de la gélatine, celles présentant des taux de dissolution non conformes avaient plus de phase amorphe après vieillissement que les gélatines conformes. L'implication des lipides dans la diminution de la dissolution de la gélatine a également été mise en évidence. La haute teneur en fer était également liée à la diminution de la dissolution mais seulement dans un site de production, ce qui suggère que la variabilité de dissolution a probablement des causes multifactorielles et dépendantes de l'origine de production.Avec le dichroïsme circulaire, nous avons pu discriminer les gélatines conformes des non-conformes avant même le vieillissement de ces gélatines. Cependant, l'interprétation des résultats reste très difficile en raison du manque d'information dans la littérature. Un tel résultat est important pour prédire le comportement de la gélatine avant le vieillissement. De manière générale, nos résultats ont mis en évidence qu’il serait pertinent de contrôler et de réduire le niveau d'oxydation et la teneur en lipides de la gélatine pour diminuer sa variabilité de dissolution. (...) / Despite a wide range of applications of gelatin and despite its very former use, gelatin composition and structure remains not fully known and understood. It is derived from animal tissue (skins or bones) and is the result of partial hydrolysis of collagen. The most abundant gelatin production, which is the focus of the present work, is pig skin gelatin which represented 46% of total production in 2007. Among numerous applications, gelatin is used as the main ingredient of the hard capsules for the pharmaceutical industry. An important property of hard capsules is that they melt in water at a temperature above 30°C and easily release drugs in the human digestive tract. Hard capsules have to meet strict dissolution specifications all along a shelf life of about five years. Thus, a dissolution test in water is applied to the gelatin constituting the hard capsules, after being artificially aged under high temperature and humidity conditions. While before aging the dissolution rate of gelatin always fit with requirement of pharmaceutical industry, a high variability in dissolution rate is observed after aging. Moreover, this dissolution variability was shown depending on the gelatin origin of production. In this context, a first objective of this work was to understand the underlying mechanisms involved in the variability of the dissolution quality of pig skin gelatin. A second objective was to identify possible “markers” of gelatin dissolution in order to predict the behaviour of gelatin through aging. Three different sites of production were chosen: two in Europe and one in USA. Cross-links formation was evidenced during aging, and among them, dityrosine was expressly identified as a marker of aging. In addition the levels of amines and aldehydes were decreased. Given that these two functions could react together; this result suggests that they could form other cross-links. Oxidation process in gelatin was clearly demonstrated. Furthermore, the quantity of triple-helices and their stability to heating decreased while the quantity of random coil and, probably, β-turns conformations increased. The results highlighted that origin of production impacts the chemical composition of gelatin. For instance, the extent of cross-link formation, such as dityrosine, in both fresh and aged gelatins, differed according to the origin of production. It was also pointed out that the physico-chemical environment of arginine allowed the distinction of production origin of gelatin. Regarding the gelatin dissolution, those showing non-compliant dissolution rates exhibited higher content of amorphous phase after aging than compliant ones. The implication of lipids in the decrease of gelatin dissolution rate was also evidenced. The decrease in dissolution was linked to the iron content only in one production site supporting the fact that dissolution variability has probably multifactorial causes, depending on the origin of production. The compliant and non-compliant dissolution rates were discriminate even before aging of gelatins by circular dichroism. However, the results interpretation remains quite difficult due to lack of literature information.Such a result is of importance in a view of predicting the behavior of gelatin before aging. To display a general overview, our results highlighted that, in order to reduce variability in the dissolution of gelatin, controlling and reducing the oxidation level and the lipid content will be relevant levers. To study the structural conformation thoroughgoing small angles neutrons would be an interesting tool. To complete the characterization of gelatin composition, quantifying and profiling lipids and sugars would be useful to better understand the gelatin oxidative instability.

Well stimulation is the treatment remedy when oil/gas productivity decreases to unacceptable economical limits. Well stimulation can be carried out through either "Matrix Acidizing" or fracturing with both "Hydraulic Fracturing" and "Acid Fracturing" techniques. "Matrix Acidizing" and "Acid Fracturing" applications involve injecting an acid to react with the formation and dissolve some of the minerals present and recover or increase the permeability. The permeability enhancement is achieved by creating conductive channels "wormholes" in case of "Matrix Acidizing" or creating uneven etching pattern in case of "Acid Fracturing" treatments. In both cases, and to design a treatment successfully, it is necessary to determine the distance that the live acid will be able to penetrate inside the formation, which in turn, determines the volume of the acid needed to carry out the treatment. This distance can be obtained through lab experiments, if formation cores are available, or estimated by modeling the treatment. The successful model will depend on several chemical and physical processes that take place including: the acid transport to the surface of the rock, the speed of the reaction of the acid with the rock, which is often referred to as "Reaction Rate", and the acid leak-off. The parameters describing these processes such as acid diffusion coefficient and reaction kinetics have to be determined experimentally to ensure accurate and reliable modeling. Hydrochloric acid and simple organic acids such as acetic and citric acids have been used extensively for stimulation treatments. The diffusion and reaction kinetics of these acids, in a straight form, were investigated thoroughly in literature. However, solely these acids are used in a simple form in the field. Acid systems such as gelled, crosslinked gelled, surfactant-based, foam-based, or emulsified acids are used to either retard the reaction rate or to enhance acid diversion. Literature review shows that additional work is needed to understand the reaction and report the diffusion and kinetics of these systems with carbonate. In addition, a new chelating agent (GLDA) was recently introduced as a stand-alone stimulating fluid. The kinetics and the mass transfer properties of this acid were not studied before. Therefore, the objective of this work is to study the reaction of different acid systems with calcite and dolomite and report the mass transport and kinetic data experimentally. Lactic acid, a chelating agent (GLDA), and in-situ gelled HCl-formic acids were investigated in this study. In some cases, rheology measurements and core flood experiments were conducted. The data were combined with the reaction study to understand the behavior of these acids and examine their efficiency if injected in the formation.

Poorly water-soluble and insoluble chemical agents are routinely investigated in the pharmaceutical industry for pharmacological activity, but many of these are never commercialized due to inadequate dissolution and subsequent low oral bioavailability following oral administration. The bioavailability of many hydrophobic active pharmaceutical ingredients (APIs) can be increased by enhancing their aqueous dissolution. Spray-Freezing into Liquid (SFL) is a novel particle engineering technology that has been demonstrated in the following studies to significantly enhance the dissolution of insoluble APIs. The ultimate goal throughout the studies was to produce micronized SFL powders where the inherently insoluble API would be completely dissolved in aqueous dissolution media within a minimal amount of time (less than ca. 10 minutes). The SFL particle engineering technology is a novel process that was developed, investigated and optimized in order to broaden its applications in pharmaceutical drug delivery systems. Micronized SFL powders were compared head-to-head with powders produced from milling, co-grinding with excipients and slow freezing of liquids containing dissolved API and excipients followed by lyophilization. To strengthen the applicability of the SFL particle engineering technology, studies were conducted where micronized SFL powders were exposed to various stability storage conditions, and characterized to determine the influences of the exposure conditions and time on the physicochemical properties of the powder containing the API. The utility of the SFL process was further enhanced by developing an atmospheric freeze-drying (ATMFD) technique to obtain dry micronized SFL powders. Micronized SFL powders dried by ATMFD were compared to micronized SFL powders dried by vacuum-freeze drying to determine any changes in physicochemical properties or dissolution profiles as a function of the drying technique utilized. The usefulness of the SFL particle engineering technology was broadened when it was found that highly concentrated emulsions could be processed by SFL to produce micronized powders that rapidly wetted and dissolved in dissolution media. Micronized SFL powders produced from emulsion were investigated and compared to slowly frozen agglomerates from emulsion and a micronized SFL powder from solution. As a result of the following studies, the enabling examples using the SFL platform were designed to illustrate applications of the SFL technology as a tool to enhance the aqueous dissolution of poorly water-soluble and insoluble APIs. Therefore, it was demonstrated that this novel particle engineering technology is a feasible method that may be used in the pharmaceutical industry to solve the ever-present solubility and dissolution problems associated with poorly water-soluble or insoluble APIs, or chemical agents being investigated for pharmacological activity as future APIs / text

In the production of base metals by smelting of sulphide ore concentrates, large amounts of iron are rejected with iron silicate slags. These slags contain Ni, Cu and Co in concentrations up to several percent units. Extraction of the entrapped base metals using high pressure oxidative acid leaching (HPOXAL) was investigated in this work. Crystalline slags containing fayalite (Fe2SiO4), magnetite (Fe3O4), silica (SiO2) and matte (MeSn<1) were found to be highly amenable to leaching at 250°C, 90 psi (6.2 bar) O2 partial pressure and 70 g/L initial H2SO4. Extractions of Ni, Co and Cu exceeded 90% within 15-20 min and arrived at 95-97% after 45 min. The residues of leaching were identified as aggregates of crystalline hematite (Fe2O3) and amorphous silica. Dissolution of fayalite and magnetite was shown to be acid driven. Since HPOXAL operates with substoichiometric additions of sulphuric acid (10-20% of the stoichiometric requirement), acid regeneration facilitated by iron oxidation and hydrolysis is crucial to high rates of leaching. Low acidities (<10 g/L) were shown to cause precipitation of ferrous sulphate, slowing acid regeneration and slag dissolution. Elevated acidities (>70 g/L) result in excessive concentrations of Fe(III) in the leach solution, complicating downstream processing. The use of pyrrhotite tailings, an environmentally hazardous waste, as a substitute of sulphuric acid in slag leaching was investigated. Oxidative co-leaching of pyrrhotite tailings with naturally cooled converter slag at 250°C, 90 psi (6.2 bar) O2, 68 g/L equivalent H2SO4 was shown to have kinetics comparable to adding sulphuric acid with final extractions reaching 95-97% in 45 min. Granulation of slag melt can produce an amorphous solid solution of SiO2 and metal oxides. Amorphous slag is not amenable to HPOXAL due to the formation of a passive layer of silica. Leaching of amorphous slag at low temperatures was shown to proceed nearly to completion. The difference in the leachability of amorphous slag at high and low temperatures is explained in terms of the rate of silicic acid re-polymerization leading to closure of pores in the leached layer.

In the production of base metals by smelting of sulphide ore concentrates, large amounts of iron are rejected with iron silicate slags. These slags contain Ni, Cu and Co in concentrations up to several percent units. Extraction of the entrapped base metals using high pressure oxidative acid leaching (HPOXAL) was investigated in this work. Crystalline slags containing fayalite (Fe2SiO4), magnetite (Fe3O4), silica (SiO2) and matte (MeSn<1) were found to be highly amenable to leaching at 250°C, 90 psi (6.2 bar) O2 partial pressure and 70 g/L initial H2SO4. Extractions of Ni, Co and Cu exceeded 90% within 15-20 min and arrived at 95-97% after 45 min. The residues of leaching were identified as aggregates of crystalline hematite (Fe2O3) and amorphous silica. Dissolution of fayalite and magnetite was shown to be acid driven. Since HPOXAL operates with substoichiometric additions of sulphuric acid (10-20% of the stoichiometric requirement), acid regeneration facilitated by iron oxidation and hydrolysis is crucial to high rates of leaching. Low acidities (<10 g/L) were shown to cause precipitation of ferrous sulphate, slowing acid regeneration and slag dissolution. Elevated acidities (>70 g/L) result in excessive concentrations of Fe(III) in the leach solution, complicating downstream processing. The use of pyrrhotite tailings, an environmentally hazardous waste, as a substitute of sulphuric acid in slag leaching was investigated. Oxidative co-leaching of pyrrhotite tailings with naturally cooled converter slag at 250°C, 90 psi (6.2 bar) O2, 68 g/L equivalent H2SO4 was shown to have kinetics comparable to adding sulphuric acid with final extractions reaching 95-97% in 45 min. Granulation of slag melt can produce an amorphous solid solution of SiO2 and metal oxides. Amorphous slag is not amenable to HPOXAL due to the formation of a passive layer of silica. Leaching of amorphous slag at low temperatures was shown to proceed nearly to completion. The difference in the leachability of amorphous slag at high and low temperatures is explained in terms of the rate of silicic acid re-polymerization leading to closure of pores in the leached layer.

En France, les déchets de Haute Activité à Vie Longue (HAVL) issus du retraitement du combustible nucléaire usé sont confinés à l’échelle atomique dans un verre borosilicaté appelé le verre R7T7. Lors de son élaboration à haute température, des cristaux incorporant les radionucléides se forment de manière transitoire sous différentes conditions dans le liquide avant d’être dissouts. Jusqu’à présent, de nombreuses études se sont portées sur la cristallisation de ces phases mais leur dissolution n’a pas fait l’objet d’étude approfondie. L’objectif de cette thèse est de décrire les cinétiques et les mécanismes de la dissolution des cristaux dans le liquide borosilicaté.Dans ce but, la dissolution de silicates de terres rares de structure apatite, type Ca2TR8(SiO4)6O2, est étudiée en conditions isothermes dans trois compositions borosilicatées différentes en système fermé. Afin de suivre l’évolution des fractions cristallines au cours du temps, une méthodologie basée sur l’acquisition de mosaïques d’images MEB associée à du traitement d’images a été optimisée. En compléments, des profils chimiques aux interfaces cristaux/verre sont également réalisés par microsonde électronique.Le modèle Johnson-Mehl-Avrami-Kolmogorov (JMAK), habituellement employé pour décrire la cristallisation dans les verres, est appliqué avec succès aux fractions cristallines mesurées au cours de la dissolution. L’application de ce modèle pour différentes températures de traitement thermique valide son efficacité à décrire les cinétiques de dissolution des silicates de terres rares dans des systèmes borosilicatés en régime statique. Son application est également étendue à des systèmes plus complexes présentant simultanément plusieurs phases cristallines de nature autre que les silicates de terres rares. De plus, ce modèle permet d’accéder au mécanisme contrôlant la dissolution des cristaux dans les liquides borosilicatés (dans les systèmes étudiés, la diffusion), à l’énergie d’activation de leur dissolution ainsi qu’aux constantes de dissolution et aux durées caractéristiques de la dissolution pour chaque température. / In France, High-Level radioactive Wastes (HLW) coming from nuclear spent fuel treatment are confined at the atomic scale in an homogeneous sodium-borosilicate glass called the R7T7 glass. At different stages of the melting process performed at high temperature, crystallized phases which incorporate the radionuclides are temporarily formed before their dissolution. The formation conditions of these crystals have already been studied but, to date, few studies on their dissolution in nuclear glass melt have been performed. The objective of this thesis is the description of the kinetics and mechanisms of the crystals dissolution in the borosilicate melt.This study focuses on the dissolution of rare earth silicates with an apatite structure (Ca2Nd8(SiO4)6O2 type) in three borosilicate melt compositions. Experiments are conducted in isothermal mode and in closed system. The crystalline fractions are followed according to time thanks to the acquisition of SEM images mosaics coupled with image analysis. In addition, chemical profiles at the crystal/melt interfaces are acquired by microprobe.The Johnson-Mehl-Avrami-Kolmogorov (JMAK) model, usually applied to describe the crystallization in melt, is successfully applied to the crystalline fractions measured during the dissolution process. The application of this model for different temperatures of thermal treatment validates its effectiveness to describe the dissolution kinetics of rare earth silicates in borosilicate systems in static mode. Its application is furthermore extended to the crystals dissolution in more complex systems where different types of crystals are simultaneously present. This model allows to determine the mechanism limiting the crystals dissolution in borosilicate melts, i.e. the diffusion in the studied systems, the activation energy of the dissolution as well as the constants of dissolution and the characteristic durations of dissolution for each considered temperature.

La réalisation de revêtements fins, solides et isolants dans le domaine ultrasonore,contenant de petites particules poreuses, représente le challenge de ces travaux. Plusieurs points sont déterminants pour arriver à cet objectif final. Tout d’abord, il faut trouver le matériau adéquat pour les particules poreuses, notre choix s’est porté sur un polymère mou, le PEG-DA. Une fois le matériau choisi, il faut déterminer une voie de synthèse pour en faire un matériau poreux, une technique par photopolymérisation UV etpar dissolution d’un porogène sacrificiel (CaCO3) a été utilisée. Ensuite, la microfluidiquenous a permis de réaliser des microparticules de ce polymère poreux de tailles contrôlées et monodisperses. La dernière étape consiste à disperser ces particules dans une matrice pour en faire un revêtement. Les mesures acoustiques ont montré une bonne atténuation du PEG-DA dans les ultrasons.Par ailleurs, ces travaux ont permis d’étudier la photopolymérisation frontale de milieux transparents et très diffusants, et de présenter une méthode à partir de simulations Monte-Carlo pour décrire les profils de conversion du polymère en fonction de l’intensité initiale et de l’épaisseur traversée. D’autres études se sont focalisées sur le séchage d’hydrogels de PEG-DA et sur la dissolution de CaCO3 à travers ces mêmes hydrogels. Un modèle physique décrivant la compétition entre cinétique de dissolution et diffusion de l’acide a été proposé. / The fabrication of thin, solid and insulating coatings containing small porous particles is the major challenge of these works. Several key points need to be raised to succeed. First, a good material for the particles has to be found, we chose a soft polymer, PEG-DA. Then, the choice of the synthesis routine to make porous polymers is crucial. A technique using UV photopolymerization and dissolution of sacrificial porogen (CaCO$_3$) will be used. Next, we will decide to make porous particles by microfluidics to obtain well controlled sizes and good monodispersity. The last step will be about the dispersion of those particles in a matrix to create coatings. Acoustics measurements will show the acoustic response of PEG-DA in ultrasounds. Moreover, this work will also permit us to study the frontal photopolymerization of transparent and scattering media and to present a method with Monte-Carlo simulations to describe conversion profiles of polymer as a function of intensity and path length. Other studies will present drying of PEG-DA hydrogels and dissolution of CaCO$_3$ through those hydrogels. A physical model will be proposed to describe the competition between kinetics and acid diffusion.

Ce travail de thèse porte sur l’étude de divers mécanismes de fragilisation d’un acier inoxydable supermartensitique 16Cr-4Ni à basse teneur en carbone (Virgo™38) utilisé pour la fabrication des compresseurs centrifuges produits par GE Oil&Gas.Il a été montré que la microstructure fine, polyphasée et morphologiquement très complexe de cet alliage était sensible aux conditions de traitement thermique. Notamment, la proportion et la répartition de l’austénite de réversion, la présence de carbure de chrome et la ségrégation intergranulaire d’éléments fragilisant tel que le phosphore ont été mis en évidence suite à plusieurs traitements thermiques. La ségrégation du phosphore aux joints de grain (SPJG) est l’un des mécanismes entrainant la fragilisation du Virgo™38 sous certaines conditions de traitement thermique.La présence d’austénite de réversion n’entraine pas seulement une amélioration de la ténacité de l’alliage mais également le piégeage de l’hydrogène dans cette phase. Etant donnée la grande instabilité mécanique de l’austénite, sa transformation sous contrainte provoque la libération de cet hydrogène piégé et ainsi une surconcentration locale en hydrogène. La fragilisation par hydrogène est le deuxième mécanisme entrainant la fragilisation du Virgo™38 étudié dans cette thèse.Les mécanismes mis en jeu lors de la formation de l’austénite de réversion conduisent à la répartition hétérogène des éléments d’alliage. L’une des conséquences de cette répartition hétérogène est la corrosion sélective de l’une ou l’autre des phases de l’alliage en fonction du pH de l’environnement et de la charge appliquée. La dissolution préférentielle est le dernier mécanisme abordé. / This PhD thesis is focused on the study of embrittlement mechanisms in a 16Cr-4Ni low carbon supermartensitic stainless steel (Virgo™38) used for the construction of rotating parts of centrifugal compressors produced by GE Oil&Gas.It is shown that the morphologically complex multiphase microstructure of this alloy is very sensitive to the heat treatment conditions. In particular, the fraction and repartition of retained austenite, the presence of chromium carbides and the phosphorous grain boundary segregation (PGBS) are evidenced consecutive to several heat treatments. PGBS is one of the mechanisms leading to brittle failure of Virgo™38 after specific heat treatments.The presence of retained austenite is not only beneficial for toughness but also leads to hydrogen trapping in this phase. Due to the mechanical instability of retained austenite, its transformation under applied stress leads to the release of trapped hydrogen into newly formed martensite and thus to a local overconcentration of hydrogen. Hydrogen embrittlement is the second mechanism studied in this report.Mechanisms involved during the formation of retained austenite lead to the heterogeneous repartition of alloying elements (partitioning). One of the consequences being the selective dissolution of one or the other phase of the alloy as a function of the pH of the environment and of the load applied. Preferential dissolution is the third mechanism studied.

La compréhension des mécanismes pilotant la cinétique d'évaporation d'une gouttelette sessile sur un substrat inerte a notablement progressé ces dernières années. Ainsi, l'influence de l'angle de contact de la goutte, de la conductivité thermique du solide, de sa rugosité, de la convection thermocapillaire à l'intérieur de la goutte, ou de la convection dans la vapeur environnante, sont maintenant bien compris. Parallèlement, la façon dont des dépôts de type ‘tâche de café' se forment pendant l'évaporation de fluides complexes (suspension colloïdale, sang …) a été étudiée en détail.Toutes ces études ont été réalisées avec des solides non-réactifs. Nous proposons ici d'étudier le comportement d'une goutte d'eau s'évaporant sur un substrat soluble. Dans cette configuration, trois phénomènes sont en interaction complexe : la dissolution/précipitation du substrat à l'interface solide-liquide, la diffusion/convection des espèces dissoutes dans la gouttelette, l'évaporation de l'eau à l'interface liquide-air. Nous avons travaillé avec des solides à dissolution rapide, des monocristaux de NaCl et KCl, à température et humidité contrôlées. Pour tester l'influence des instabilités thermo- et soluto-gravitationnelles, nous avons réalisé des expériences au sol et en micropesanteur, lors de plusieurs campagnes de vols paraboliques CNES.Nous avons observé que la dissolution induisait un ancrage de la ligne triple au tout début de l'évaporation, conduisant à une décroissance linéaire de l'angle de contact avec le temps. A la fin de l'évaporation, un dépôt périphérique apparaît. Cette configuration permet ainsi de faire apparaître des dépôts de type ‘tâche de café' à partir d'une goutte d'eau pure. Ces dépôts sont la preuve d'un écoulement radial de l'intérieur vers l'extérieur au sein de la goutte. L'observation de gouttes ensemencées de particules fluorescentes s'évaporant sur un monocristal de sel a permis de mettre en évidence des écoulements capillaires complexes au sein de celle-ci. La morphologie des dépôts périphériques est très variée, passant continument de la forme de parois inclinées à celle de demi-tore creux, lorsque le volume initial de la goutte ou la température varient / Recent progresses have led to a better understanding of the mechanisms driving the evaporation kinetics of a sessile droplet of simple liquid on an inert substrate. For instance, the influence of the contact angle of the droplet, of the thermal conductivity of the solid, of its roughness, of the thermocapillary convection inside the droplet, or of the convection in the vapor are now better understood. Besides, the way coffee-stain-like deposits form during the evaporation of complex fluids (colloidal suspension, blood …) has now been studied in detail.All these studies have been carried out with non-reacting solids. We propose here the investigation of the behavior of a water droplet evaporating on a soluble substrate. In this configuration, three phenomena are strongly interacting: dissolution/precipitation of the substrate at the solid-liquid interface, diffusion/convection of the dissolved species in the droplet, evaporation of water at the liquid-air interface. We have worked with fast-dissolving solids, NaCl and KCl single crystals, with controlled temperature and humidity. To test the influence of thermogravitational instabilities, experiments on the ground and in microgravity (parabolic flights) have been carried out.We have observed that the dissolution induces a pinning of the triple line at the early beginning of the evaporation, leading to a decrease of the contact angle linear in time. At the end of the evaporation, a peripheral deposit (coffee-ring-like) resulting from the salt migration and precipitation, is always present, proof of an outward flow inside the droplet. The observation of drops seeded with fluorescent particles evaporating on a dissolving solid (NaCl single crystal) has highlighted complex capillary flows inside the liquid. The shape of this ring-like deposit is very diversified and vary with the substrate temperature and the initial volume of the droplet