Au cours des dernières décennies, les technologies membranaires ont largement contribué à l’amélioration des procédés de séparation à l’échelle industrielle grâce à de nombreux avantages, tels que la sélectivité de la séparation élevée, la possibilité de travailler avec des composés thermolabiles et la faible demande en énergie, ainsi que la possibilité de combiner les technologies membranaires avec d'autres procédés de séparation. Le procédé de pervaporation est une technique de séparation membranaire importante utilisée pour séparer les mélanges liquides binaires ou multicomposants, y compris les solvants à point d’ébullition proche, les mélanges azéotropes et les isomères. Il s’agit du transfert sélectif de matière à travers une membrane dense. Au cours de cette opération, le perméat sous forme vapeur est condensé sur une paroi froide, mais, contrairement à la distillation, seule une faible partie de la charge subit ce changement d’état. Les membranes utilisées dans la pervaporation doivent posséder une forte sélectivité, une stabilité chimique et une résistance mécanique à haute température élevées. La sélectivité et les propriétés de transport de la membrane déterminent l'efficacité globale du processus de séparation. La caractérisation approfondie des membranes est cruciale pour bien comprendre l’influence de la structure de la membrane et des conditions de préparation de la membrane sur les caractéristiques d’équilibre, de séparation et de transport des membranes étudiées, en vue de développer de nouveaux matériaux polymères efficaces. Les nombreuses recherches ont également été menées sur le développement des membranes avec de liquides ioniques (LIs) afin de personnaliser les propriétés de séparation des membranes utilisées dans la séparation des liquides par pervaporation, la séparation des gaz et la séparation des ions métalliques ainsi que les membranes conductrices dans les piles à combustible. Les LIs sont caractérisés par une bonne stabilité thermique, une conductivité ionique élevée, une pression de vapeur négligeable et un point de fusion assez bas. En raison de leurs nombreuses propriétés uniques, les membranes polymères contenant des LIs possèdent une large gamme d'avantages, comme de meilleures propriétés de séparation que les membranes polymères classiques. Ce fait est lié à une diffusion moléculaire beaucoup plus élevée dans un liquide ionique que dans des polymères. Par conséquent, l'utilisation de membranes à base de polymères et LIs dans les processus de séparation permettrait une sélectivité de séparation élevée et des flux plus importants. La structure et les propriétés physicochimiques des LIs peuvent être ciblées en fonction de l’application afin d'obtenir un matériau polymère approprié. En revanche, même si l’application de membranes hybrides à base de polymères et LIs suscite un intérêt croissant, leur utilisation dans les procédés de séparation reste limitée en raison des pertes de LI non lié. Cette thèse de doctorat en co-tutelle est réalisée entre la Faculté de Chimie de l'Université Nicolaus Copernicus (NCU) à Toruń (Pologne) et le Laboratoire Polymères, Biopolymères, Surfaces UMR 6270 CNRS de l’Université de Rouen Normandie (France). L’objectif principal de la thèse est d’élaborer de nouvelles membranes denses à base de poly (alcool vinylique) (PVA) et d’acétate-propionate de cellulose (CAP) et de divers LIs réactifs et polymérisables ceci afin d’obtenir un système polymère-liquide ionique dans lequel le LI est stabilisé par liaison covalente avec les chaînes macromoléculaires du polymère. L'étude des propriétés physicochimiques et d'équilibre des membranes a été effectuée ainsi que l’analyse de leurs propriétés de transport. De plus, les membranes sélectionnées ont été testées dans un processus de pervaporation en contact avec le mélange eau-propane-2-ol. / In the last decades, membrane separation has played an important role in many industrial processes thanks to its versatility, low energy consumption, high performances of membranes, as well as a possibility of combining membrane technologies with other separation processes. Membrane technologies gave a great contribution to the improvement of separation processes in the industrial scale thanks to a number of advantages, such as the high selectivity of the separation, the opportunity to work with thermolabile compounds, and low energy demand. Pervaporation process is an important membrane separation technique used to separate binary or multicomponent liquid mixtures including close boiling solvents, azeotrope mixtures, and isomers. During pervaporation, feed components are in the direct contact with one side of the lyophilic membrane, while the selected components are preferentially transported across the membrane to the permeate side. Membranes used in pervaporation must be characterized by high selectivity, chemical stability, and mechanical strength at high temperatures. Selectivity and transport properties of the membrane determine the overall efficiency of the separation process. The comprehensive characterization of membranes is the crucial approach and can lead to broaden the knowledge about the influence of the membrane structure and membrane preparation conditions on the equilibrium, separation, and transport characteristics of the studied membranes, in order to develop new polymer materials with the expected efficiency of the separation process. Research has been also focused on the development of the membranes filled with ILs in order to tailor the separation properties of the developed membranes used in liquid separation by pervaporation, gas separation, and separation of metal ions as well as the conducting barriers in fuel cells. ILs are characterized by good thermal stability, high ionic conductivity, negligible vapor pressure, and low melting point. Due to their numerous unique properties, polymer membranes containing ILs (polymer-ILs) possess wide range of advantages, like better separation properties than the classical polymer membranes. This fact is related with much higher molecular diffusion in ionic liquid than in polymers. Therefore, the use of polymer-ILs in separation processes would result in superior separation behavior and higher fluxes. Morphology and physicochemical properties of ILs can be “tailored” depending on the separated system in order to obtain a suitable polymer material for a given separation process without preparation of a chemically new membrane. Even though there is a growing interest in the application of polymer membranes filled with ILs, the polymer-ILs based separation processes are limited due to the losses of the unbound ionic liquid in the course of the exploitation. The PhD is realized in the frame of "co-tutelle" system between the Faculty of Chemistry at the Nicolaus Copernicus University (NCU) in Toruń, Poland (Membranes and Membrane Separation Processes Research Group) and the University of Rouen Normandy, France (Barrier Polymer Materials and Membranes (MPBM) Research Group of the Laboratory of Polymers, Biopolymers, Surfaces (PBS)). The main aim of the present PhD thesis is to elaborate novel dense membranes based on poly(vinyl alcohol) (PVA) and cellulose acetate propionate (CAP) filled with various reactive and polymerizable ILs in order to obtain the polymer-ionic liquid system in which ionic liquids are linked inside the polymer structure. The investigation of physicochemical characteristics and study of the equilibrium, barrier, and transport properties of the obtained membranes was carried out. Furthermore, the selected membranes were tested in pervaporation process in contact with water-propan-2-ol mixture, water and gas permeation measurements.

Les pièces situées dans des zones chaudes/tièdes (300-400°C) de l'avion sont actuellement en titane (mât moteur) ou en composite à matrice époxy (plenum). Comment pourrait-on diminuer la masse de ces pièces tout en évitant leur dégradation à hautes températures de fonctionnement ? Le projet TACT (Technologie pour Aérostructures composites Tièdes), porté par Nimitech Innovation® (Groupe LAUAK), propose une solution innovante consistant à mettre en oeuvre par voie RTM des pièces structurales tièdes à base de renfort en fibres de carbone (FC) et de matrice Cyanate ester (CE). Le choix de la matrice thermodurcissable CE est justifié par son caractère thermostable, c'est-à-dire sa capacité d'opérer en continu à de hautes températures de fonctionnement (avec une température de transition vitreuse Tg>300°C). Par ailleurs, elle possède la facilité de mise en oeuvre des époxydes du fait qu'elle s'adapte généralement bien aux paramètres du procédé RTM. Toutefois, l'exothermie élevée de la matrice CE lors de la réticulation implique un gradient de température dans la pièce composite et peut ainsi engendrer des problèmes de surchauffe. Les travaux scientifiques menés dans le cadre de cette thèse se focalisent sur la problématique de surchauffe de la résine pendant le processus de polymérisation très exothermique dans le moule RTM. L'objectif serait ainsi de maîtriser le cycle de cuisson du composite afin d'éviter tout problème d'emballement ou de dégradation pendant la réticulation de la matrice. Dès lors, la thèse s'organise de la manière suivante : dans un premier temps, le comportement thermocinétique de la matrice CE (pure et catalysée) est analysé pendant l'étape de réticulation, et ceci dans l'optique de contribuer à l'optimisation de cycle de cuisson lors de la mise en oeuvre du composite FC/CE par procédé RTM. Ensuite, les propriétés thermiques (capacité calorifique, conductivité, diffusivité) en fonction du degré d'avancement de la résine CE sont menés afin d'évaluer le gradient thermique régi par l'équation de la chaleur permettant de maîtriser la cuisson de la résine dans l'épaisseur. Par ailleurs, la vitrification de la matrice CE est étudiée par le suivi de la température de transition vitreuse Tg en fonction de la température et du taux d'avancement à l'aide de différents techniques de mesure (DSC, DMA, TMA). Enfin, une modélisation de la vitrification à l'aide du modèle Di-Benedetto permettra l'estimation de la température de la transition vitreuse Tg ∞ pour le réseau tridimentionnel entièrement réticulé. / Aeronautical parts which operate in high temperature area (300-400°C) are currently made of titanium (aircraft pylon) or composite materials based on epoxy matrix (plenum). In which extent the weight of these pieces could be reduced as well as avoiding their degradation when operating at these working temperature ranges? TACT project (Technologie pour Aérostructures composites Tièdes), overseen by Nimitech Innovation® (Groupe LAUAK), suggests an innovative solution based on the development of high performance composites parts reinforced by carbon fibers (CF) and cyanate ester matrix (CE) through RTM process. The CE resin belongs to the class of high-performance thermosetting polymers and is mainly chosen in this project due to its thermal stability when operating at high temperatures (with a glass transition Tg>300°C), as well as epoxy-like processability. However, the cross-linking reaction exhibits highly exothermic process, resulting in non-linear increase in internal temperature, which may cause a temperature overshoot. The scientific work carried out within this thesis focuses on the problem of overheating of the resin during the highly exothermic polymerization process in the RTM mold. The objective would thus be to control the curing cycle of the composite in order to avoid problems of runaway or degradation during the crosslinking of the matrix. Hence, the thesis is organized as follows: firstly, thermokinetic behavior of CE resin is analyzed during the crosslinking process in order to optimize the curing cycle. Secondly, thermal properties (heat capacity, conductivity, diffusivity) are identified as a function of the conversion degree in order to evaluate the thermal gradient covered by the heat equation making it possible to control the curing along the thickness of the composite. Moreover, the vitrification of the cyanate ester matrix is studied by monitoring the glass transition temperature Tg as a function of the temperature and conversion degree using different methods (DSC, DMA, TMA). Finally, Di-Benedetto model, a vitrification model, is chosen in order to identify the glass transition temperature Tg∞ of a full crosslinked resin.

La valorisation des co-produits riches en matières organiques et inorganiques comme additifs dans des formulations à base d’argile peut améliorer à la fois les performances mécaniques et thermiques des produits de terre cuite, de même que le bilan énergétique des procédés de fabrication de ces matériaux. Cette étude a porté sur l’incorporation de combustibles solides de récupération (CSR) dans un mélange de fabrication des produits de terre cuite pour le génie civil en étroite collaboration avec l’entreprise TERREAL dans le cadre du projet LabCom RESPECTc financé par l’ANR.Premièrement, deux CSR ont été sélectionnés et utilisés comme additifs pour améliorer les produits issus des deux gisements de mélange argileux nommés ML et MC de chez TERREAL. L’influence de la nature, du taux d’incorporation des CSR, de la granulométrie des CSR et de la nature de la matrice argileuse sur les propriétés physico-chimiques, mécaniques et thermiques des mélanges argileux/CSR a été étudiée entre 30°C et 1100°C. Dans tous les cas, l’ajout de CSR a permis d’améliorer le caractère isolant des produits de terre cuite, en diminuant leur conductivité thermique. L’ajout de CSR a aussi permis d’améliorer les propriétés mécaniques des produits, en fonction du type et du taux de CSR ajouté, du taux et de la nature (forme, taille et distribution) de la porosité créée. L’étude a démontré que les interactions entre les minéraux argileux et les éléments inorganiques des CSR avaient un impact important sur les propriétés mécaniques et thermiques. Les résultats ont montré que l’ajout de 4% en masse du CSR15-1 contenant un taux de cendres de 65,7% en masse a conduit à une augmentation de la résistance mécanique du matériau à base de la matrice argileuse ML de l’ordre de 32%. Ensuite, un modèle cinétique du frittage basé sur les variations dimensionnelles des matériaux entre 650°C et 1000°C a été développé à partir de l’analyse thermomécanique (ATM) des mélanges (avec ou sans CSR). L’objectif a été de mieux comprendre les mécanismes du frittage mis en jeu. Le modèle développé a montré une bonne adéquation avec les données expérimentales. Les résultats ont montré que l’étape du frittage thermique de ces mélanges se fait en présence d’une phase liquide et que l’ajout de CSR a permis d’accélérer la densification des matériaux. Cela a conduit à une diminution de la température usuelle de cuisson des produits de terre cuite permettant ainsi un gain énergétique non négligeable. Finalement, une étude environnementale a été réalisée lors de la cuisson des mélanges argileux/CSR. Cette étude a particulièrement été focalisée sur la contribution de CSR au bilan énergétique et à l’impact des émissions des gaz critiques tels que le CO2, le CO et l’HCl. Les résultats ont montré que les émissions de CO2 et de CO lors de la cuisson des mélanges argileux/CSR ont augmenté en raison de la décomposition thermique de la matière organique des CSR et que moins de 50% en masse du chlore a été transformé en HCl (18-31 ppm). Le bilan énergétique effectué a montré que l’ajout de CSR au sein des matrices argileuses ML ou MC compense une part non négligeable du gaz naturel usuellement utilisé comme combustible au cours de la cuisson de ces matériaux. Cela s’est traduit par une économie d’énergie thermique et une réduction des émissions de CO2 provenant de la décarbonatation de la matrice argileuse. / The valorization of co-products rich in organic and inorganic materials as additives in formulations based on clay matrix can improve both the mechanical and thermal performances of ceramic materials as well as the energy balance of the manufacturing processes of these products. This study focused on the incorporation of Solid Recovered Fuels (SRF) into the clay ceramics for civil engineering in close collaboration with TERREAL as part of the ANR funded LabCom RESPECTc project. Firstly, two SRF were selected and used as additives to improve the properties of ceramic materials from to clay mixture deposits named ML and MC from TERREAL. The influence of the nature, the amount of SRF, the grain size of SRF and the nature of clay matrix on the physico-chemical, mechanical and thermal properties of the clay/SRF mixtures were studied between 30°C and 1100°C. In all cases, the addition of SRF into the clay mixture (ML or MC) has enhanced the insulating nature of the ceramic materials by reducing their thermal conductivity. The addition of SRF has also improved the mechanical properties of the ceramic materials, depending on the nature and the amount of SRF added, the rate and the nature (shape, size and distribution) of the porosity created. The study demonstrated that interactions between clay minerals and inorganic elements of SRF have a significant effect on mechanical and thermal properties. The results showed that the addition of 4 wt.% of SRF15-1 containing an ash content of 65.7 wt.% into clay matrix ML led to increase the mechanical strength of the material based on the clay matrix ML of the order of 32%. Then, a kinetic model of thermal sintering based on the dimensional variations of ceramic materials between 650°C and 1000°C was developed from thermomechanical analysis (TMA) of the clay mixtures (with or without SRF). The main objective is to better understand the mechanism of the thermal sintering involved. The model developed showed a good adequacy with the experimental data. The results showed that the thermal sintering step of these mixtures is carried out by the presence of a liquid phase and that the addition of SRF has accelerated the densification of ceramic materials. This has led to decrease the usual firing temperature of ceramic materials, allowing a significant energy savings. Finally, an environmental assessment was carried out during the firing of clay/SRF mixtures. This study was particularly focused on the contribution of SRF to the energy balance and impact of critical gas emissions such as CO2, CO and HCl. The results showed that CO2 and CO emissions during firing of clay/SRF mixtures increased due to the thermal decomposition of the organic matter of SRF and that less than 50 wt.% of chlorine was converted to HCl (18-31 ppm). The energy balance showed that the addition of SRF into the ML matrix compensates for a significant part of the natural gas usually used as fuel during firing of these ceramic materials. This was reflected by a thermal energy saving and reduction of CO2 emissions from the decarbonatation of the clay matrix.

[pt] No desenvolvimento de materiais resistentes ao choque térmico, os materiais com expansão térmica negativa ou próxima a zero têm sido de vital importância nos últimos anos. A família de cerâmicas A2M3O12 (A = cátion trivalente, M = cátion hexavalente) apresenta características promissoras para evitar a ruptura por choque térmico, devido às suas propriedades diferenciadas de expansão térmica. Contudo, mudanças na rede cristalina causadas por defeitos pontuais podem gerar alterações neste material. A cerâmica Al2W3O12 pode conter defeitos como vacâncias de oxigênio, que afetam suas propriedades ópticas, térmicas e outras propriedades. O propósito deste trabalho é estudar a influência das vacâncias de oxigênio sobre as propriedades da cerâmica Al2W3O12, bem como, a importância da temperatura e da atmosfera sobre a geração de vacâncias de oxigênio. A fase Al2W3O12 foi exposto a duas atmosferas (H2 e Ar) sob temperaturas controladas de 300 graus C, 400 graus C e 500 graus C com o proposito de gerar vacâncias de oxigênio. A cerâmica obtida desta forma foi caracterizada por técnicas de difração de pó de raios-X (DPRX), espectroscopia por refletância de difusão (DRS), espectroscopia de ressonância paramagnética eletrônica (EPR), espectroscopia Raman, espectroscopia de fotoelétrons de raios-X (XPS) e teste de condutividade térmica. A influência das vacâncias de oxigênio no coeficiente de expansão térmica e na condutividade térmica nas amostras calcinadas em atmosferas não-oxidantes foi demonstrada. As amostras calcinadas a 500 graus C revelaram uma alta absorção do espectro ultravioleta e visível em relação às amostras calcinadas em 300 graus C e 400 graus C. Além disso, foram constatados diferentes estados reduzidos de valência do W (tais como W5+ e W4+) através da tecnica de XPS a fim de compensar vacâncias de oxigênio que foram confirmadas pela analise de EPR e Raman. / [en] In the development of materials resistant to thermal shock, materials with negative or near zero thermal expansion have been of vital importance in recent years. The A2M3O12 family of ceramics (A = trivalent cation, M = hexavalent cation) has promising characteristics to avoid thermal shock rupture, due to its atypical thermal expansion properties. Within this family is the Al2W3O12 ceramic, which has unique thermal properties and this allows its use in conditions of thermal shock. However, changes in the crystal lattice caused by point defects can generate alterations in this material. Al2W3O12 ceramic can contain defects such as oxygen vacancies, which affect optical, thermal and other properties. The goal of this study is to study the influence of oxygen vacancies on the properties of Al2W3O12 ceramics, as well as the importance of temperature and atmosphere in the generation of oxygen vacancies. The Al2W3O12 phase was exposed to two atmospheres (H2 and Ar) at controlled temperatures: 300 degrees C, 400 degrees C and 500 degrees C to generate oxygen vacancies. The ceramic obtained was characterized by X-ray power diffraction (XRPD), diffusion reflectance spectroscopy (DRS), electron paramagnetic resonance spectroscopy (EPR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and thermal conductivity test. The influence of oxygen vacancies on the coefficient of thermal expansion and thermal conductivity in calcined samples in non-oxidizing atmospheres was demonstrated. Samples calcined at 500 degrees C revealed high absorption of the ultraviolet and visible spectra compared to the samples calcined 300 degrees C and 400 degrees C. In addition, different states of reduced valence of W were found (such as W5+ and W4+), through the XPS technique, in order to compensate of oxygen vacancies, that were confirmed by EPR and Raman analysis.

Tesis por compendio / [ES] El principal objetivo de la presente tesis doctoral se ha centrado en la obtención, desarrollo y optimización de formulaciones de poliamida de origen renovable con aditivos que mejoren las propiedades mecánicas, morfológicas, térmicas, termomecánicas y de comportamiento frente al fuego. En una primera fase se ha trabajado con mezclas de poliamida con un origen parcial biológico obtenido de la reacción del ácido dicarboxílico del aceite de ricino con la 1,6-hexametilendiamina (HMDA) derivada del petróleo mediante policondensación. De esta manera se obtiene una BioPA 610 con un contenido bio entre el 60-63% en peso. Esta PA610 se combinó con nanotubos de Halloysita (HNTs) en diferentes cargas para evaluar su efecto en la matriz y sus propiedades. Se obtuvo un gran aumento de rigidez con la incorporación de carga en la matriz polimérica además de un ligero aumento de la dureza. Las propiedades morfológicas muestran una buena dispersión de los nanotubos en el material. En cuanto a las propiedades térmicas los HTNs no suponen una gran variación de las características con respecto al polímero base. Los resultados termomecánicos muestran un gran aumento en el módulo de almacenamiento. Por otro lado, se estudiaron las propiedades de comportamiento frente al fuego de las mezclas de PA610 y HNTs mediante las técnicas del cono calorimétrico, índice límite de oxígeno (LOI), opacidad y toxicidad de los gases producidos, poder calorífico de combustión y ensayo UL-94. De los resultados obtenidos se aprecia una buena reducción del calor liberado con el aumento de carga de HNTs, una ligera disminución en el valor del LOI. En cuanto a la opacidad del humo desprendido, la presencia de HNTs no afecta demasiado en la liberación del humo, pero sí se obtiene una buena reducción del CO2 desprendido durante la combustión del material. El poder calorífico muestra una disminución de hasta 10 MJ/Kg con respecto a la PA610 sin aditivo. Por último, el ensayo de UL-94 no supone variación de resultados en las diferentes muestras analizadas. En una última fase se trabajó con grafito expandido (EGr) combinado dentro de la matriz polimérica de poliamida 1010 de origen biológico obtenida 100% de fuentes renovables. En esta fase se incorporaron cargas de EGr entre 2,5% y 10% en peso. Se estudiaron propiedades mecánicas, térmicas y termomecánicas, así como el análisis del color, morfología, hidrofobia, captación de agua y su comportamiento frente al fuego. Mecánicamente se apreció una gran mejora en la rigidez del material. En las propiedades térmicas se mejoró el grado de cristalinidad del material. El análisis termomecánico mostró un aumento en el módulo (E) y en el módulo de almacenamiento (E'). El estudio de la hidrofobia y la captación de agua dio como resultado una reducción en la absorción de agua y un aumento de la hidrofobicidad del material. Por último, en cuanto a las propiedades del material frente al fuego, se consiguió reducir en gran medida la liberación de calor emitido. El valor del índice límite de oxígeno se reduce ligeramente y el ensayo de la UL-94 muestra una mejora de V-2 a V-1 en la clasificación del compuesto con la incorporación de EGr frente al polímero sin aditivar. / [CA] El principal objectiu de la present tesi doctoral s'ha centrat en l'obtenció, el desenvolupament i l'optimització de formulacions de poliamida d'origen renovable amb additius que millorin les propietats mecàniques, morfològiques, tèrmiques, termomecàniques i de comportament davant del foc. En una primera fase s'ha treballat amb barreges de poliamida amb un origen parcial biològic obtingut de la reacció de l'àcid dicarboxílic de l'oli de ricí amb la 1,6-hexametilendiamina (HMDA) derivada del petroli mitjançant policondensació. D¿aquesta manera s'obté una BioPA 610 amb un contingut bio entre el 60-63% en pes. Aquesta PA610 es va combinar amb nanotubs de Halloysita (HNTs) en diferents càrregues per avaluar el seu efecte a la matriu i les seues propietats. Es va obtenir un gran augment de rigidesa amb la incorporació de càrrega a la matriu polimèrica a més d'un lleuger augment de la duresa. Les propietats morfològiques mostren una bona dispersió dels nanotubs al material. Quant a les propietats tèrmiques, els HTNs no suposen una gran variació de les característiques respecte al polímer base. Els resultats termomecànics mostren un gran augment en el mòdul d'emmagatzematge. D'altra banda, es van estudiar les propietats de comportament davant del foc de les barreges de PA610 i HNTs mitjançant les tècniques del con calorimètric, índex límit d'oxigen (LOI), opacitat i toxicitat dels gasos produïts, poder calorífic de combustió i assaig UL-94. Dels resultats obtinguts s'aprecia una bona reducció de la calor alliberada amb l'augment de càrrega de HNTs, una lleugera disminució al valor del LOI. Quant a l'opacitat del fum desprès, la presència de HNTs no afecta gaire en l'alliberament del fum, però sí que s'obté una bona reducció del CO2 desprès durant la combustió del material. El poder calorífic mostra una disminució de fins a 10 MJ/Kg respecte de la PA610 sense additiu. Finalment, l'assaig d'UL-94 no suposa variació de resultats a les diferents mostres analitzades. En una darrera fase es va treballar amb grafit expandit (EGr) combinat dins de la matriu polimèrica de poliamida 1010 d'origen biològic obtinguda 100% de fonts renovables. En aquesta fase es van incorporar càrregues d'EGr entre el 2,5% i el 10% en pes. Es van estudiar propietats mecàniques, tèrmiques i termomecàniques, així com l'anàlisi del color, la morfologia, la hidrofòbia, la captació d'aigua i el seu comportament davant del foc. Mecànicament es va apreciar una gran millora en la rigidesa del material. A les propietats tèrmiques es va millorar el grau de cristal·linitat del material. L'anàlisi termomecànica va mostrar un augment al mòdul (E) i al mòdul d'emmagatzematge (E'). L'estudi de la hidrofòbia i la captació d'aigua va donar com a resultat una reducció de l'absorció d'aigua i un augment de la hidrofobicitat del material. Finalment, quant a les propietats del material davant del foc, es va aconseguir reduir en gran mesura l'alliberament de calor emesa. El valor de l'índex límit d'oxigen es redueix lleugerament i l'assaig de la UL-94 mostra una millora de V-2 a V-1 a la classificació del compost amb la incorporació d'EGr davant del polímer sense additivar. / [EN] The main objective of this doctoral thesis has focused on obtaining, developing and optimizing polyamide formulations of renewable origin with additives that improve the mechanical, morphological, thermal, thermomechanical and fire behavior properties. In a first phase, has been carried out an experimental with polyamide mixtures with a partial biological origin obtained from the reaction of the dicarboxylic acid of castor oil with 1,6-hexamethylenediamine (HMDA) derived from petroleum by means of polycondensation. In this way, a BioPA 610 with a bio content between 60-63% by weight is obtained. This PA610 was combined with Halloysite nanotubes (HNTs) at different loadings to evaluate its effect on the matrix and its properties. A large increase in stiffness was obtained with the incorporation of filler in the polymeric matrix in addition to a slight increase in hardness. The morphological properties show a good dispersion of the nanotubes in the material. Regarding the thermal properties, the HTNs do not imply a great variation of the characteristics with respect to the base polymer. The thermomechanical results show a large increase in the storage modulus. On the other hand, the fire behavior properties of the mixtures of PA610 and HNTs were studied using the calorimetric cone techniques, limit oxygen index (LOI), opacity and toxicity of the gases produced, calorific value of combustion and UL-94 test. From the results obtained, a good reduction of the heat released with the increase in the load of HNTs, a slight decrease in the value of the LOI, can be seen. Regarding the opacity of the smoke released, the presence of HNTs does not affect the release of smoke too much, but a good reduction of the CO2 released during the combustion of the material is obtained. The calorific power shows a decrease of up to 10 MJ/Kg with respect to PA610 without additive. Lastly, the UL-94 test does not assume any variation in results in the different samples analysed. In a final phase, expanded graphite (EGr) combined within the polyamide 1010 polymeric matrix of biological origin obtained 100% from renewable sources was worked on. In this phase, EGr loads between 2.5% and 10% by weight were incorporated. Mechanical, thermal and thermomechanical properties were studied, as well as the analysis of color, morphology, hydrophobicity, water uptake and its behavior against fire. Mechanically, a great improvement in the rigidity of the material was appreciated. In the thermal properties, the degree of crystallinity of the material was improved. The thermomechanical analysis showed an increase in the modulus (E) and in the storage modulus (E'). The study of hydrophobicity and water uptake resulted in a reduction in water absorption and an increase in the hydrophobicity of the material. Finally, regarding the properties of the material against fire, it was possible to greatly reduce the release of emitted heat. The value of the oxygen limit index is slightly reduced and the UL-94 test shows an improvement from V-2 to V-1 in the classification of the compound with the incorporation of EGr compared to the polymer without additives. / This research was funded by the Ministry of Science, Innovation, and Universities (MICIU) project numbers MAT2017-84909-C2-2-R and AGL2015- 63855-C2-1-R. Project funded with grant number PID2020-116496RB-C22 funded by the Ministry of Science and Innovation MCIN/AEI/10.13039/501100011033 and grant number AICO/2021/025 funded by Generalitat Valenciana. AITEX wants to thank CDTI (Centro para el Desarrollo Tecnológico Industrial) within the framework of grants for Technological Centres of Excellence “Cervera” (CER- 20211013). The author would like to thank the INTERREG SUDOE NABITEX project (SOE2/P1/P0524) for allowing him to participate in it as part of his training. / Marset Gimeno, D. (2022). Desarrollo y optimización de formulaciones de poliamida de origen renovable con comportamiento ignífugo [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/185134 / Compendio

The Cone Calorimeter has been used widely for various purposes as a bench - scale apparatus. Originally the retainer frame (edge frame) was designed to reduce unrepresentative edge burning of specimens. In general, the frame has been used in most Cone tests without enough understanding of its effect. It is very important to have one - dimensional (1D) conditions in order to estimate thermal properties of materials. It has been implicitly assumed that the heat conduction in the Cone Calorimeter is 1D using the current specimen preparation. However, the assumption has not been corroborated explicitly to date. The first objective of this study was to evaluate the heat transfer behavior of a Cone specimen by examining its three - dimensional (3D) heat conduction. It is essential to understand the role of wall lining materials when they are exposed to a fire from an ignition source. Full - scale test methods permit an assessment of the performance of a wall lining material. Fire growth models have been developed due to the costly expense associated with full - scale testing. The models require heat flux maps from the ignition burner flame as input data. Work to date was impeded by a lack of detailed spatial characterization of the heat flux maps due to the use of limited instrumentation. To increase the power of fire modeling, accurate and detailed heat flux maps from the ignition burner are essential. High level spatial resolution for surface temperature can be provided from an infrared camera. The second objective of this study was to develop a heat flux mapping procedure for a room test burner flame to a wall configuration with surface temperature information taken from an infrared camera. A prototype experiment is performed using the ISO 9705 test burner to demonstrate the developed heat flux mapping procedure. The results of the experiment allow the heat flux and spatial resolutions of the method to be determined and compared to the methods currently available.

Recent findings of multiferroicity and magnetoelectric effects in rare earth manganites have fuelled research in this class of materials. These multiferroics can be structurally divided into two classes – orthorhombic and hexagonal. Especially attractive are TbMnO3, HoMnO3 and DyMnO3. Since the ionic radius of Dy is at the boundary that separates the orthorhombic and hexagonal RMnO3, DyMnO3 can be synthesized in both the structures using different synthesis conditions. In this thesis, DyMnO3 single crystals (both hexagonal and orthorhombic) prepared using optical floating zone furnace are studied through structural, magnetic and thermal properties. The influence of rare earth ion on the magnetic phase transitions is revealed in magnetisation, ac susceptibility and specific heat studies. Moreover, doping RMnO3 (small R) with alkaline earth ions creates an arena to test the interesting physics of spin-glass-like phenomena in manganites that arises due to quenched disorder. In this regard, 50% strontium diluted DyMnO3 could be an ideal system to study the effects of quenched disorder and structural/magnetic inhomogeneities that govern the magnetic phases in manganites. Structural phase-coexistence and ensuing anomalous magnetism in Pr–based manganite Pr0.6Sr0.4MnO3 are also presented in this thesis. Details of how the thesis is organized into eight chapters and a brief summary of each chapter follows: Chapter 1 is an introduction to the physics of manganites which progresses into multiferroics and eventually discusses the spin-glass-like effects arising due to size mismatch. A discussion on the phase-coexistence and its effect on physical properties are also presented. Eventually, the scope of the thesis is outlined in the last section. Chapter 2 outlines the basic experimental methods employed in this thesis work. Chapter 3 describes the details of crystal growth by optical floating zone method. DyMnO3 crystals in both hexagonal and orthorhombic structures are grown by employing the ambience of argon and air respectively. The crystals in the two crystallographic variants are characterized by X ray diffraction, Energy dispersive X ray analysis and Inductively coupled plasma atomic emission spectroscopy. The crystal structures are refined using Rietveld method with FULLPROF code and found to be P63cm for hexagonal and Pnma for orthorhombic DyMnO3. Details of crystal growth of Dy1−xSrxMnO3 are also presented. The change in ambience has no effect in the crystal structure of this doped manganite. A comparison of the growth of undoped and doped systems is given. In a later section, the crystal growth and structure refinement of Pr0.6Sr0.4MnO3 are discussed and the optimized growth parameters are tabulated for various manganite systems grown in the present work. Chapter 4 deals with the magnetic and thermal characterization of hexagonal and orthorhombic DyMnO3 single crystals. Magnetic measurements reveal the importance of rare earth magnetism in these compounds. The antiferromagnetic transition to a stacked triangular antiferromagnet is discernible from the specific heat studies of hexagonal DyMnO3, which is masked in the bulk magnetisation measurements. Various magnetic transitions pertaining to the antiferromagnetic sinusoidal – spiral – incommensurate magnet, are evident in the magnetisation and specific heat of orthorhombic DyMnO3 which belongs to the class of non-collinear magnets. Chapter 5 deals with basic investigations on the spin-glass-like state in Dy0.5Sr0.5MnO3. Preliminary dc magnetisation shows indication of spin-glass state as a split in field-cooled and zero-field-cooled magnetisation cycles. Further, the failure of scaling of M(T) with H/T indicates the absence of superparamagnetism in Dy0.5Sr0.5MnO3. The dynamic susceptibility and its analysis using the theory of critical slowing down yield exponents pertaining to the spin-glasses. However, a four-order magnitude change is observed in the characteristic spin-flip time. This leads to the assumption that in Dy0.5Sr0.5MnO3 the spin entities are not atomic spins as in canonical spin-glasses but clusters of spins. The specific heat is analysed for signatures of spin-glass state and is found that a linear term in temperature is essential in fitting the observed data. The crystalline electric fields of Dy ion is also analysed attempting multiple Schottky-levels instead of two. Chapter 6 concerns with the aging experiments performed in the spin-glass-like state in Dy0.5Sr0.5MnO3. Striking aging and chaos effects are observed through these measurements. However, owing to the clusters of spins present, deviations from the typical time-dependent behavior seen in canonical spin-glass materials are anticipated in Dy0.5Sr0.5MnO3. In fact, the relaxation measurements indicate that the glassy magnetic properties are due to a cooperative and frustrated dynamics in a heterogeneous or clustered magnetic state. In particular, the microscopic spin flip time obtained from dynamical scaling near the spin-glass transition temperature is four orders of magnitude larger than microscopic times found in atomic spin-glasses. Magnetic viscosity, deduced from the waiting time dependence of the zero field cooled magnetisation, exhibits a peak at a temperature T<Tsg. Waiting time experiments prove that the dynamics is collective and that the observed memory effects are not due to superparamagnetism of separate magnetic entities. Chapter 7 discusses the Electron paramagnetic resonance (EPR) studies on single crystals of DyMnO3 in hexagonal as well as orthorhombic structures. The interesting effect of strontium dilution on the frustrated antiferromagnetism of DyMnO3 is also probed using EPR. The lineshapes are fitted to broad Lorentzian in the case of pure DyMnO3 and to modified Dysonian in the case of Dy0.5Sr0.5MnO3. The linewidth, integrated intensity and geff derived from the signals are analysed as a function of temperature. The EPR results corroborate well with the magnetisation measurements. The study clearly reveals the signature of frustrated magnetism in pure DyMnO3 systems. It is found that antiferromagnetic correlations in these systems persist even above the transition. Moreover, a spinglass-like behaviour in Dy0.5Sr0.5MnO3 is indicated by a step-like feature in the EPR signals at low fields. Chapter 8 deals with the magnetic and electrical properties of Pr0.6Sr0.4MnO3 single crystals. This crystal undergoes two prominent phase transitions – a paramagnetic to ferromagnetic at Tc~300 K and a structural transition at Tstr ~ 64 K. These phase transitions are evident in the static magnetisation as well as in frequency-dependent susceptibility. In these measurements, the structural transition is associated with a sizeable hysteresis typical of a first-order transition. The M–H curves below Tc show clear indication of anomalous magnetism at low temperatures: the virgin curve lies outside the subsequent magnetisation loops. These observations are explained by assuming structural coexistence of a high–temperature orthorhombic and a low–temperature monoclinic ferromagnetic phases. The nature of static magnetisation data is analysed in the critical region. Modified Arrott’s plots yielded perfect straight lines with the isotherm at ~ 300 K passing through the origin. The exponent values thus should be very close to those expected for the universality class of Heisenberg ferromagnets. The temperature dependence of resistivity also shows critical nature with an exponent belonging to the Heisenberg class. The thesis concludes with a chapter on General conclusions and future scope on these systems.

Chalcogenide glasses have attracted considerable attention due to their infrared transparency, low phonon energy, and high non linear optical properties. They have been explored as promising candidate for optical memories, gratings, switching devices etc. Because of their low phonon energy and high refractive indices, now a days these are used for high efficiency fibre amplifiers. Nevertheless, the availability of amorphous semiconductors in the form of high quality multilayers provides potential applications in the field of micro and optoelectronics. Among amorphous multilayers, chalcogenide multilayers are attractive because of the prominent photoinduced effects. Studies in chalcogenide amorphous multilayer have been directed towards two phenomena. One is photoinduced interdiffusion in short period multilayer systems which finds potential applications in holographic recording and fabrication of phase gratings . The other is photo darkening or photobleaching which is also known in thick films. These multilayers exhibit prominent photoinduced effects, similar to those exhibited by uniform thin films. In spite of its practical usefulness, the mechanism of photoinduced interdiffusion is not properly understood. Since most structural transformations are related to atomic diffusion, understanding of the structural transformation must be based on the diffusion process. The main aim of this thesis is to study the photoinduced diffusion in Sb/As2S3 multilayered films and (As2S3)1-xSbx thin films. In literature, there are reports about the photoinduced interdiffusion in Se/As2S3 and Bi/As2S3 multilayered films, but the mechanisms of photoinduced interdiffusion of these elements are not very clear. Raman scattering and infrared spectroscopy techniques have been used to study the photoinduced interdiffusion in Se/As2S3 and Bi/As2S3 multilayered films by Malyovanik et al. (M. Malyovanik, M. Shiplyak, V. Cheresnya, T. Remeta, S. Ivan, and A. Kikineshi, J. Optoelectron. Adv. Mater. 5, 397 (2003). But many questions remain unanswered. The characteristic spectra of components in the multilayer and those of the diffused layer were rather similar. In the present thesis, photoinduced interdiffusion in Sb/As2S3 multilayered samples are studied by Fourier Transform Infrared spectroscopy (FTIR) at room and low temperature and X-ray photoelectron spectroscopy (XPS). The photoinduced effects in (As2S3)1-xSbx thin films are studied by FTIR, XPS and Raman Spectroscopy. The detailed information about the distribution of electronic states in the absorption edge, localized states and the new bonds formed between the components due to photoinduced interdiffusion elucidated from the above studies will give more insight into the mechanism and kinetics of photoinduced interdiffusion. The thesis consists of seven chapters. References are given at the end of each chapter.

The Phase Change Memories (PCM) based on chalcogenide glasses are being considered recently as a possible replacement for conventional Non Volatile Random Access Memories (NVRAM). The main advantages of chalcogenide phase change memories are their direct write/overwrite capability, lower voltages of operation, large write/erase cycles, easiness to integrate with logic, etc. The phase change random access memories work on the principle of memory switching exhibited by chalcogenide glasses during which a local structural change (between amorphous and crystalline states) occurs due to an applied electric field. The development of newer phase change materials for NVRAM applications is based on synthesizing newer glass compositions and investigating their electrical switching characteristics by applying current/voltage pulses of different waveforms. The thermal studies on chalcogenide glasses which provide information about thermal stability, glass forming ability, etc., are also important while selecting a chalcogenide glass for PCM applications. The present thesis work deals with electrical switching and thermal studies on certain silicon based ternary telluride glasses (As-Te-Si, Ge-Te-Si and Al-Te-Si). The effect of network topological thresholds on the composition dependence of switching voltages and thermal parameters such as glass transition temperature, specific heat capacity, non-reversing enthalpy, etc., of these glasses has been investigated. The first chapter of the thesis provides an introduction to various properties of chalcogenide glasses, including their applications in phase change memories. The fundamental aspects of amorphous solids such as glass formation, glass transition, etc., are presented. Further, the concepts of rigidity percolation and self organization in glassy networks and the influence of local structural effects on the properties of glassy chalcogenides are discussed. Also, a brief history of evolution of phase change memories is presented. The second chapter deals with the experimental techniques employed in this thesis work; for sample preparation and for electrical switching studies, Alternating Differential Scanning Calorimetry (ADSC), Raman spectroscopy, NMR spectroscopy, etc. The third chapter discusses the electrical switching and thermal studies on As30Te70-xSix (2 ≤ x ≤ 22) and As40Te60-xSix (2 ≤ x ≤ 17) glasses. The composition dependence of electrical switching voltage (VT) and thermal parameters such as glass transition temperature (Tg), crystallization temperature (Tc), thermal stability (Tc-Tg), etc., reveals the occurrence of extended rigidity percolation and chemical thresholds in As30Te70-xSix and As40Te60-xSix glasses. Chapter 4 presents the electrical switching and thermal studies on Ge15Te85-xSix glasses (2 ≤ x ≤ 12). These glasses have been found to exhibit memory type electrical switching. While Ge15Te85-xSix glasses with x ≤ 5 exhibit a normal electrical switching, an unstable behavior is seen in the I-V characteristics of Ge15Te85-xSix glasses with x > 5 during the transition to ON state. Further, the switching voltage (VT) and initial resistance (R) are found to increase with addition of Si, exhibiting a change in slope at the rigidity percolation threshold of the Ge15Te85-xSix system. The ADSC studies on these glasses indicate the presence of an extended stiffness transition and a thermally reversing window in Ge15Te85-xSix in the composition range of 2 ≤ x ≤ 6. The fifth chapter deals with electrical switching investigations, thermal and structural studies on Al15Te85-xSix glasses (2 ≤ x ≤ 12). These glasses have been found to exhibit two crystallization reactions (Tc1 and Tc2) for compositions with x < 8 and a single stage crystallization is seen for compositions above x = 8. Also, a trough is seen in the composition dependence of non-reversing enthalpy (ΔHNR), based on which it is proposed that there is a thermally reversing window in Al15Te85-xSix glasses in the composition range 4 ≤ x ≤ 8. Further, Al15Te85-xSix glasses are found to exhibit a threshold type electrical switching at ON state currents less than 2 mA. The start and the end of the thermally reversing window seen in the thermal studies are exemplified by a kink and saturation in the composition dependence of switching voltages respectively. 27Al Solid State NMR measurements reveal that in Al15Te85-xSix glasses, Al atoms reside in 4-fold as well as 6-fold coordinated environments. Unlike in Al-As-Te glasses, there is no correlation seen between the composition dependence of the fraction of 4-fold and 6-fold coordinated aluminum atoms and the switching behavior of Al-Te-Si samples. Chapter 6 provides a comparison of the properties of the three glassy systems studied (As-Te-Si, Ge-Te-Si and Al-Te-Si), made to identify the system better suited for phase change memory applications. It is found that the Ge-Te-Si glassy system has better electrical/thermal properties for phase change memory applications. The seventh chapter describes easily reversible SET-RESET processes in Ge15Te83Si2 glass which is a promising candidate for phase change memory applications. This sample exhibits memory switching at a comparatively low threshold electric field (Eth) of 7.3 kV/cm. The SET and RESET processes have been achieved with 1 mA triangular current pulse for the SET process and 1 mA rectangle pulse (of 10 msec width) for RESET operation respectively. Further, a self-resetting effect is seen in this material upon excitation with a saw-tooth/square pulse. About 6.5x104 SET-RESET cycles have been achieved without any damage to the device. In chapter 8, results of in-situ Raman scattering studies on the structural changes occurring during the SET and RESET processes in Ge15Te83Si2 sample, are presented. It is found that the degree of disorder in the glass is reduced from OFF to SET state. The local structure of the sample under RESET condition is similar to that in the OFF state. The Raman results are found to be consistent with the switching results which indicate that the Ge15Te83Si2 glass can be SET and RESET easily. Further, Electron Microscopic studies on switched samples indicate the formation of nanometer sized particles of cSiTe2. A summary of the results obtained and the scope for future work are included in the chapter 9 of the thesis.

Pulse tube cryocoolers (PTC) are a class of rugged and high-endurance refrigeration systems that operate without moving parts at their low temperature ends, and are capable of reaching temperatures down to and below 123 K. PTCs are particularly suitable for applications in space, guiding systems, cryosurgery, medicine preservation, superconducting electronics, magnetic resonance imaging, weather observation, and liquefaction of gases. Applications of these cryocoolers span across many industries including defense, aerospace, biomedical, energy, and high tech. Among the challenges facing the PTC research community is the improvement of system efficiency, which is a direct function of the regenerator component performance. A PTC implements the theory of oscillatory compression and expansion of the gas within a closed volume to achieve desired refrigeration. An important deficiency with respect to the state of art models dealing with PTCs is the limited understanding of the hydrodynamic and thermal transport parameters associated with periodic flow of a cryogenic fluid in micro-porous structures. In view of the above, the goals of this investigation include: 1) experimentally measuring and correlating the steady and periodic flow Darcy permeability and Forchheimer’s inertial hydrodynamic parameters for available rare-Earth ErPr regenerator filler; 2) employing a CFD-assisted methodology for the unambiguous quantification of the Darcy permeability and Forchheimer’s inertial hydrodynamic parameters, based on experimentally measured steady and periodic flow pressure drops in porous structures representing recently developed regenerator fillers; and 3) performing a direct numerical pore-level investigation for steady and periodic flows in a generic porous medium in order to elucidate the flow and transport processes, and quantify the solid-fluid hydrodynamic and heat transfer parameters. These hydrodynamic resistances parameters were found to be significantly different for steady and oscillatory flows.