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Desenvolvimento de materiais híbridos baseados em poliimida / Development of hybrid materials based on polyimideFábio Augusto de Souza Ferreira 10 July 2014 (has links)
Nesse trabalho são discutidos os resultados a respeito de materiais híbridos baseados na poliimida, PI, obtida por reações de policondensação entre a diamina 4,4\'-Oxidianilina (ODA) e o dianidrido 4,4\'-Oxidiftálico (ODPA), seguida de imidização térmica. O estudo foca na influência do tempo de tratamento (1, 15 e 60 min) e na temperatura de decomposição térmica (500°C) sobre as propriedades da PI. Os experimentos foram realizados sob fluxo de Argônio e os materiais obtidos apresentam características intermediárias entre PI e materiais carbonáceos. Dados de Nanoindentação (NI) revelaram aumento de até 50% de dureza para os filmes tratados por 60 min. ODPA e ODA serviu ainda de base para a preparação do revestimento híbrido contendo ORMOSIL gerado in situ por catálise ácida via processo sol-gel a partir do (3-aminopropil)trietóxissilano (APTES) e Tetraetil Ortossilicato (TEOS). O revestimento obtido é homogêneo e tem boa interação com o substrato (aço inoxidável 316L). A polarização potenciodinâmica revelou uma proteção elevada tanto em solução de NaCl 3,5% em massa quanto em H2SO4 0,5 mol L-1, em relação ao aço sem revestimento, com densidade de corrente da ordem de 10-9 A cm-2, na faixa de -700 a 500 mV vs Ag/AgCl. Por fim, filmes híbridos baseados em ODPA, ODA, APTES e TEOS, adicionados de Ácido Fosfotungstico (HPW) foram preparados e avaliados por Espectroscopia na região do Infravermelho com Transformada de Fourier e Ressonância Magnética Nuclear de Silício e Fósforo (29Si e 31P MAS NMR) que confirmaram a formação da PI e da rede ORMOSIL, bem como revelam que a estrutura do HPW permaneceu intacta após o processo de síntese. Mapeamentos realizados por Micro-fluorescência de Raios X assistida por Luz Síncrotron (μ-XRF) mostram uma boa dispersão da fase inorgânica (ORMOSIL e HPW) na orgânica (POO), e todos os materiais são termicamente estáveis até aproximadamente 500°C, de acordo com as curvas obtidas por Termogravimetria (TGA). Outras técnicas de caracterização também foram usadas para uma investigação mais detalhada dos materiais. / In this thesis are presented the results and considerations related to several hybrid materials derived from the polyimide, PI, obtained by polycondensation reactions between 4,4\'-Oxydianiline (ODA) and 4,4\'-Oxydiphthalic (ODA), followed by thermal imidization. The study focuses on the effect of thermal treatment time (1, 15 and 60 min) and the temperature of beginning of thermal decomposition (773 K) on the properties of PI. The experiments were performed under Argon flow, and the materials presented intermingled properties of PI and carbonaceous materials. The hardness, evaluated by Nanoindentation (NI), reached an increase of 50% for POO films treated for 60 min. POO was also used for the preparation of the hybrid coating containing ORMOSIL obtained in situ by acid catalysis via sol-gel process from (3-aminopropyl)triethoxysilane (APTES) and Tetraethyl Orthosilicate (TEOS). The coating is homogeneous and present a good interaction with the substrate (316L stainless steel). Data of potendynamic polarization revealed a high protection both under NaCl 3.5 wt% and H2SO4 0.5 mol L-1 solutions related to the neat substrate, with current density of order 10-9 A cm-2, in range potential of -700 to 500 mV vs Ag/AgCl. Finally, hybrid films were prepared based on ODPA, ODA, APTES and TEOS, in addition to Phosphotungstic Acid (HPW). The characteristics of all materials were evaluated by Fourier Transform Infrared Spectroscopy in Middle and Near Infrared region (FTMIR and FTNIR), and Magic Angle Spinning-Nuclear Magnetic Resonance of Silicon 29 and Phosphorus 31 (29Si and 31P MAS NMR) which confirmed the ORMOSIL network formation, as well as revealed that the HPW structure remained intact after the synthesis process. Mapping performed by Assisted Synchrotron Light X-ray Micro Fluorescence (μ-XRF) the good dispersion of the inorganic phase (ORMOSIL and HPW) in the organic phase (POO). All materials are thermally stable up to 773 K, according to Thermogravimetric Analysis (TGA). Other techniques of characterization were also used to further investigation of the materials.
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Assemblage colloïdal pour l'élaboration de matériaux hybrides polysaccharide-silice. Interactions, interfaces et textures. / Colloïdal assembly for the synthesis of polysaccharide-silica hybrid materials. Interactions, interfaces and textures.Cardoso, Laura 02 October 2015 (has links)
L'objectif principal de ce travail de thèse est l'étude de la formation de matériaux hybrides polysaccharides – oxydes métalliques par assemblage colloïdal. Il concerne à la fois la compréhension des mécanismes et l'obtention de nouveaux matériaux et textures. Pour ce faire, nous avons étudié dans un premier temps les suspensions formées par les précurseurs colloïdaux (nano-bâtonnets de chitine, oligomères siloxane). Grâce à la détermination des diagrammes de phases, nous avons montré que ces co-suspensions dans l'éthanol présentent, comme en milieu aqueux, des propriétés d'auto-assemblage conduisant à la formation de mésophases nématiques chirales. Par ailleurs, l'étude rhéologique de ces fluides complexes a montré une forte influence des proportions relatives des deux précurseurs sur la viscosité, mettant en évidence le rôle déterminant des interactions entre colloïdes. Au-delà, la caractérisation par microscopie électronique nous a permis de confirmer la formation de colloïdes hybrides au sein des co-suspensions. Dans un deuxième temps, nous avons élaboré de nouveaux matériaux composites soit en modifiant le précurseur polysaccharide (cellulose vs. chitine), soit en introduisant de nouveaux précurseurs de phases inorganiques (Al2O3, TiO2, ZnS). La caractérisation de ces matériaux nous a permis d'évaluer le rôle de la chimie de surface, de la nature et de la taille des précurseurs sur les interactions colloïdales et les propriétés texturales finales. Enfin, nous avons étudié l'effet des procédés de mise en forme – microsphères par atomisation-séchage, fibres par électro-filage, films minces – et de l'application de champs externes – champ électrique, cisaillement – sur les caractéristiques des matériaux. A partir de ces nouveaux résultats, nous proposons un mécanisme de formation qui permet d'envisager la synthèse de matériaux fonctionnels dont les propriétés seraient ajustées selon les applications visées (catalyse, propriétés mécaniques…). / The major aim of this PhD thesis has been to study the formation of polysaccharides metal oxides hybrid materials through colloidal assembly. It concerns both the understanding of the mechanisms and the obtention of new materials and textures. To that purpose, we first studied suspensions of the colloidal precursors (chitin nanorods and siloxane oligomers). By mapping out the phase diagrams, we demonstrated that co-suspensions in ethanol exhibit self-assembly properties, similar to those obtained with chitin in aqueous medium, leading to the formation of chiral nematic mesophases. Besides, the rheological study of these complex fluids showed a great influence of the relative proportions of the precursors upon viscosity, hence revealing the major role played by colloidal interactions. Moreover, electron microscopy observations allowed us to confirm the formation of hybrid nanorods colloids made of chitin and silica within the co-suspensions. Then, we elaborated new composite materials either by changing the polysaccharide precursor (cellulose vs. chitin) or by introducing new precursors of inorganic phases (Al2O3, TiO2, ZnS). The characterization of these materials allowed us to estimate the impact of precursors' characteristics (surface chemistry, nature and size) on colloidal interactions and final textural properties. Lastly, we investigated the influence of the materials morphology and processing method – microspheres by spray-drying, fibers by electrospinning, thin films – and application of external fields – electric field, shearing – on the obtained materials characteristics. Based on these new results, we propose a mechanism of formation which enables us to envision the synthesis of functional materials with properties adjusted to intended applications (catalysis, mechanical properties…).
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Preparation of well-defined Ir(I)-NHC based catalytic material for the hydrogenation of functional olefins / Élaboration des matériaux hybrides pour hydrogénation catalytiqueRomanenko, Iuliia 30 November 2015 (has links)
La réaction d'hydrogénation des alcènes est une réaction clé dans de nombreux procédés industriels permettant la production de produits de commodité et de spécialité. D’importants efforts de recherche ont donc été réalisés pour développer des systèmes catalytiques de plus en plus productifs et sélectifs. Parmi les nombreux catalyseurs homogènes et hétérogènes développés à ce jour, les complexes organométalliques d’Iridium(I), très prometteurs, ont été préparés depuis la découverte du catalyseur de Crabtree, [Ir(COD)(py)(PCy3)]BF4, pour répondre à des problèmes de sélectivité dans l'hydrogénation asymétrique ou celle d’oléfines tétrasubstituées fortement encombrées en conditions homogènes. Cependant, l'utilisation industrielle de ce complexe organométallique d’Ir (I) est limité par sa décomposition rapide en solution, qui conduit à la formation de complexes polynucléaires (hydrures pontés d'Iridium) très stables et inactifs en catalyse. Le but de ce travail de thèse a été de développer des matériaux catalytiques contenant des complexes Ir(NHC) isolés à la surface d’une silice contenant des fonctionnalités imidazolium parfaitement distribuées le long de ses canaux poreux. L'isolement des unités Ir(I) sur le support de silice devrait permettre d’empêcher les processus bimoléculaires de désactivation et faciliter la récupération du catalyseur. La préparation des matériaux catalytiques cible se fait grâce a la transformation des unités imidazolium contenues dans le matériau de départ en carbenes d’argent N-hétérocycliques, qui sont ensuite transmétallés en carbènes d’iridium avec le complexe [Ir(COD)Cl]2. Les matériaux obtenus ont été caractérisés par diverses techniques, notamment une technique de RMN très avancée : la RMN de l’état solide utilisant la polarisation nucléaire dynamique. Ceci a permis de mieux comprendre la structure moléculaire des sites de surface iridiés. Les performances catalytiques des complexes Ir-NHC supportés ont été testées dans réaction d’hydrogénation des alcènes et comparées à celles de leurs homologues homogènes. Divers substrats oléfiniques et différentes conditions de réaction ont été testées. Les résultats montrent que le catalyseur supporté est beaucoup plus stable et 50 fois plus actif en terme de vitesse et de productivité. Cette approche a été étendue au développement de catalyseurs d’iridium supportés sur polymère. Le support choisi a été un polyéthylene téléchélique contenant des fonctionnalités iodées terminales. Le solide obtenu après incorporation de l’iridium a été caractérisé par RMN et spectrométrie de masse (MALDITOF). Les performances catalytique de ce nouveau système ont été elles aussi comparées a celles de complexes homologues en solution / Alkene hydrogenation is a key in many bulk and fine chemicals production processes. Major efforts were therefore directed towards the preparation of ever more productive and selective catalysts. Among the large number of homogeneous and heterogeneous catalysts, promising Iridium (I) organometallic complexes were prepared since the discovery of the well-known Crabtree’s catalyst, [Ir(COD)(py)(PCy3)]BF4, to address selectivity issues in homogeneous asymmetric hydrogenation or hydrogenation of highly hindered tetrasubstituted olefins. However, the industrial use of Ir organometallic complexes as catalysts is limited by their fast decomposition leading to the formation of highly stable and inactive polynuclear iridium hydridebridged complexes. The goal of this PhD project was to elaborate supported Ir(I)-NHC catalytic material to prevent such bimolecular deactivation processes. The targeted supported Ir complexes were based on hybrid organic-inorganic material containing regularly distributed imidazolium units along the pore-channels of the silica framework. Beside the Ir-site isolation on the silica support, this catalytic system was also expected to ease catalyst recovery at the end of the hydrogenation. The preparation of the final systems relies on the preparation of supported silver carbenes first, and further transmetallation with an Ir-precursor, namely [Ir(COD)Cl]2. The materials were characterized by several techniques as for example advanced solid state NMR using Dynamic Nuclear Polarization to gain insight into the molecular structure of the Ir surface sites. Catalytic performances of the supported Ir-NHC complexes were tested in alkene hydrogenation and compared to those of homogeneous homologues. Several different substrates and reaction conditions were tested. The results showed that the supported catalyst was much more stable and 50 times more active in term of rate and productivity. A polymer supported Ir-complex was also elaborated using a telechelic polyethylene iodide as support. The polymeric materials were fully characterized by NMR and MALDI-TOF experiments and their catalytic performances were compared to those of molecular analogues and those of silica supported systems
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Synthèse de fluorures hybrides à porosité variable : applications dans le domaine de l'énergie / Synthesis of hybrid fluorides with tunable porosity : applications in the energy fieldPereira Pimenta, Vanessa 18 September 2015 (has links)
Ce travail a concerné la synthèse hydro-solvothermale et la caractérisation de nouveaux fluorures hybrides à porosité variable, dans l’objectif à terme de tester ces matériaux poreux en stockage ou purification de gaz. En première partie, l’aminotétrazole a été utilisé comme ligand organique et a permis de mettre en évidence douze nouveaux fluorures hybrides, dont six sont de type MOF. Plusieurs paramètres de synthèse ont été identifiés comme cruciaux dans la condensation d'édifices ouverts. C’est, en particulier, la température, la composition du milieu ainsi que la nature des cations métalliques (Zn2+/Fe3+, Fe2+/Fe3+ et Zn2+ seul) et du solvant. Les porosités estimées de ces MOF atteignent 25% en volume bien que la taille de l’aminotétrazole soit réduite. En seconde partie, des ligands plus étendus à noyaux tétrazoliques multiples ont été choisis afin de parvenir à augmenter la dimension des cavités des MOFs. Ces molécules, non commercialisées, ont été synthétisées dans un premier temps puis impliquées dans l’élaboration de nouveaux hybrides. Alors que la molécule H3btt à 3 noyaux tétrazole n’a pas abouti à des résultats, H2bdt a conduit à de nouvelles architectures fluorées en présence de Zn et/ou Fe. Deux d’entre elles, [Hdma]∙(FeIIF(bdt)) et FeIIF(Hbdt), présentent des porosités remarquables de 40 et 60% qui s’approchent de celles des matériaux de référence. / This work focuses on the hydro-solvothermal synthesis and the characterization of new hybrid fluorides with tunable porosity, with the aim of testing new porous materials for gas storage and purification. In the first part, the aminotetrazole was used as organic linker and twelve new hybrid fluorides were evidenced, six phases belong to MOFs class. Several parameters were identified as crucial for the condensation of open frameworks, in particular, the temperature, the medium composition as well as the nature of metallic cations (Zn2+/Fe3+, Fe2+/Fe3+ or only Zn2+) and of the solvent. The porosity of these MOFs reaches 25% of volume, in spite of the small size of the aminotetrazole molecule. In the second part, polytetrazoles linkers with extended size were chosen, in order to increase the size of MOFs cavities. Non-commercial molecules were prepared and applied to the elaboration of new hybrids. While H3btt with 3 tetrazole cycles did not provide any expected result, H2bdt led to new fluorinated architectures in the presence of Zn and/or Fe. Two phases, [Hdma]∙(FeIIF(bdt)) and FeIIF(Hbdt), exhibit remarkable porosities of 40 and 60%, values.
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MANGANESE-BASED THIN FILM CATHODES FOR ADVANCED LITHIUM ION BATTERYZhimin Qi (8070293) 14 January 2021 (has links)
<p>Lithium ion batteries have been regarded as one of the most promising and intriguing
energy storage devices in modern society since 1990s. A lithium ion battery
contains three main components, cathode, anode, and electrolyte, and the
performance of battery depends on each component and the compatibility between
them. Electrolyte acts as a lithium ions conduction medium and two electrodes
contribute mainly to the electrochemical performance. Generally, cathode is the
limiting factor in terms of capacity and cell potential, which attracts significant
research interests in this field.Different
from conventional slurry thick film cathodes with additional electrochemically
inactive additives, binder-free thin film cathode has become a promising
candidate for advanced high-performance lithium ion batteries towards applications
such as all-solid-state battery, portable electronics, and microelectronics.
However, these electrodes generally require modifications to improve the
performance due to intrinsically slow kinetics of cathode materials. </p>
<p>In
this thesis work, pulsed laser deposition has been applied to design thin film
cathode electrodes with advanced nanostructures and improved electrochemical
performance. Both single-phase nanostructure designs and multi-phase
nanocomposite designs are explored. In terms of materials, the thesis focuses
on manganese based layered oxides because of their high electrochemical performance.
In Chapter 3 of the nanocomposite cathode work, well dispersed Au nanoparticles were introduced into highly
textured LiNi<sub>0.5</sub>Mn<sub>0.3</sub>Co<sub>0.2</sub>O<sub>2 </sub>(NMC532)
matrix to act as localized current collectors and decrease the charge transfer resistance.
To further develop this design, in Chapter 4, tilted Au pillars were incorporated
into Li<sub>2</sub>MnO<sub>3</sub> with more effective conductive Au
distribution using simple one-step oblique angle pulsed laser deposition. In
Chapter 5, the same methodology was also applied to grow 3D Li<sub>2</sub>MnO<sub>3</sub>
with tilted and isolated columnar morphology, which largely increase the lithium
ion intercalation and the resulted rate capability. Finally, in Chapter 6, direct
cathode integration of NMC532 was attempted on glass substrates for potential
industrial applications. </p>
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Processing and Characterization of Nanocellulose Composites: The Leap from Poly(lactic acid) to Polyamide 6Caitlyn Michelle Clarkson (8774828) 02 May 2020 (has links)
This disseration covers the processing and characterization of nanocellulose polymer composites. In this disseration, two fiber spinning methods were developed to create high stiffness nanocomposite fibers from renewably-sourced materials and the properties of these nanocomposites were evaluated. Additionally, bulk nanocomposites were created and some of the properties of these materials, for different types of nanoparticles, are also discussed. Evaluation of nanocellulose as a nucleation agent in poly(lactic acid) is also presented for very small concentrations of nanocelluloses in a plasticized polymer.
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Ordered Structures from Nanoparticles/Block Copolymer Hybrids: Ex-situ Approaches toward Binary and Ternary NanocompositesHorechyy, Andriy 01 July 2011 (has links)
Within the field of modern technology, nanomatrials, such as nanoparticles (NP), nanorods (NR), quantum dots (QD) etc. are, probably, the most prominent and promising candidates for current and future technological applications. The interest in nanomaterials arise not only form the continuous tendency towards dimensions minimisation of electronic devices, but also due to the fact, that new and, often, unique properties are acquired by the matter at the length scale between 1 and 100 nm.
The ability to organize nanoparticles into ordered arrays extends the range of useful NP-based systems that can be fabricated and the diversity of functionalities they can serve. However, in order to successfully exploit nanoparticle assemblies in technological applications and to ensure efficient scale-up, a high level of direction and control is required.
Recently, block copolymers (BCP) have attracted much attention as a powerful and very promising tool for creation of nanoscale ordered structures owing to their self-assembling properties. In addition, these systems offer the possibility to fabricate nanostructured composite materials via incorporation of certain nanoadditives (i.e. NPs). The concept is that by selective inclusion of the nanoparticles into one of the blocks of a self-assembling copolymer, the nanoparticles are forced into a defined spatial arrangement determined by the phase morphology of the block copolymer.
In present work self-assembling phenomena of block copolymers was exploited to fabricate binary (NP/BCP) and ternary (NP1/NP2/BCP) composites, filled with pre-synthesized nanoparticles of various nature. Polystyrene-block-polyvinylpyridine block copolymers (PS-b-PVP) of various composition and molecular weight were used for fabrication of nanocomposites.
The first part of the thesis focuses on fabrication of functional BCP-based composites containing magnetic nanoparticles (MNP), selectively assembled within one of the blocks of BCP matrix. Magnetic nanoparticles (MNPs) were selected among others since, as for today, there is the least number of successful results reported in literature on their selective incorporation into one of the phases of a BCP matrix. From the application point of view fabrication of periodic arrays of “magnetic domains” with periodicity on nanometer scale is also of interest for potential use in high-density magnetic data storage devices.
For this purpose, ferrite-type MNP (Fe3O4, CoFe2O4) having apparent affinity toward polyvinylpyridine (PVP) phase were prepared using simple one-pot synthesis. Highly selective nanoparticles segregation into PVP domains of BCP was achieved owing to the presence of sparse stabilizing organic shell on the nanoparticles surface. Importantly, as-prepared MNPs did not require any additional surface modification step to acquire affinity towards PVP phase. Appropriate selection of annealing conditions allowed to produce patterns of nearly perfect degree of lateral order over relatively large surface large area (more than 4 sq µm).
The second task of present work was fabrication of ternary NP1/NP2/BCP hybrid composites with two different types of nanoparticles being selectively localized in different microdomains of phase segregated block copolymer matrix. So far as only few studies have been reported on developing of approaches toward ternary composites, creation of alternative and straight forward routes toward such systems is still a challenge.
In the frame of this part of present work, silver nanoparticles (AgNPs) covered with polystyrene shell were prepared, with the purpose to be incorporated into polystarene phase of phase separated PS-b-PVP block copolymer matrix.
Two different approaches were tested to achieve desired three-component system. First, supposed simple blending of block copolymer and two kinds of nanoparticles having specific affinity toward different blocks of BCP in common solvent. After preparation of MNP/AgNP/BCP composite thin film and subsequent solvent vapour annealing, different domains of microphase segregated PS-b-PVP BCP were filled with different type of nanoparticles.
Alternatively, step-wise approach for nanoparticles incorporation was developed and implemented for successful selective nanoparticles incorporation. For this purpose polystyrene stabilized AgNPs (i.e. NP1) were initially mixed with PS-b-PVP BCP to produce composite thin films having nanoparticles selectively located within PS microdomains, while citrate-stabilized second type nanoparticles (i.e NP2) were deposited from their aqueous solutions into PVP domains of AgNP/PS-b-PVP composites.
By partition of nanoparticles incorporation procedure into two distinct steps it was also possible to increase effective loading of each type of NPs into BCP matrix.
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Development of new carbon hybrid materials for Li+ and Na+ ion batteries applications / Développement de nouveaux matériaux carbonés hybrides pour des applications dans les batteries Li+ et Na+ ionPana, Cristina 09 February 2018 (has links)
Au cours des dernières années, de nombreuses recherches se sont concentrées sur les batteries afin de satisfaire leur demande croissante pour de nombreuses applications. Les matériaux hybrides métal/carbone ont fait l'objet d'une grande attention en tant qu'anodes pour les batteries ioniques Li et Na en raison de leur capacité plus élevée par rapport aux anodes graphite/carbone dur. Cependant, l'expansion de la taille des NPs métalliques et la forte capacité irréversible pendant le 1ercycle sont les principaux inconvénients à surmonter et représentent l'objectif principal de cette thèse. Trois types d'hybrides ont été étudiés (C@Sn et C@SiO2pour les LIBs, et C@Sb pour les NIBs) et des voies de synthèse originales ont été développées qui ont permis d'obtenir des matériaux avec des NPs petites et homogènes distribuées dans le réseau de carbone. Plusieurs paramètres expérimentaux ont été optimisés, conduisant à une vaste palette de matériaux avec des porosités, des structures et des granulométries différentes. La température et la charge de particules se sont avérées être les principaux paramètres affectant la porosité et la taille des particules ainsi que les performances électrochimiques. L'augmentation de la température et de la charge de NPs ont conduit à une porosité plus faible qui a permis de diminuer la capacité irréversible et d'améliorer la capacité réversible. En même temps, le cycle à long terme a été affecté négativement en raison de la formation de particules non confinées et agglomérées. Un compromis entre la charge de carbone/porosité/structure a été déterminé pour chaque système et les mécanismes électrochimiques traités sur la base d'analyses post-mortem. / During the last years a lot of research has been focused on batteries to satisfy their increasing demand for a broad application. Metal-based/carbon hybrid materials received great attention as anodes for Li and Na ion batteries due to their higher capacity compared to graphite/hard carbons anodes. However, the metal particle size expansion and the high irreversible capacity during cycling are the main inconvenients to be overcome and represent the main goal of this thesis. Three type of hybrids were studied(C@Sn and C@SiO2for LIBs, and C@Sb for NIBs) and original synthesis pathways were developed which allowed to obtain materials with small and homogeneous distributed particles in the carbon network. Several experimental parameters were tuned leading to a large pallet of materials exhibiting different porosities, structures and particle size/distribution. The temperature and the particle loading were found to be the main parameters affecting the porosity and the particle size and further the electrochemical performances. The increase of both temperature and particle loading lead to smaller porosity which successfully allowed to diminish the irreversible capacity and to improve the reversible capacity. In the same time, the long-term cycling was negatively affected due to the formation of un-confined and agglomerated particles. The extent of particle agglomeration and consequently of capacity fading was found to depend on the type of metal and synthesis route. A compromise between the carbon loading/porosity/structure was determined for each system and the electrochemical mechanisms addressed based on post-mortem analyses.
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Multifunctional layered simple hydroxides : structural investigations, functionalization and properties / Hydroxydes simples lamellaires multifonctionnels : investigations structurales, fonctionnalisations et propriétésEvrard, Quentin 12 December 2017 (has links)
Le but de cette thèse est l’obtention de matériaux multiferroïques par l’insertion de molécules organiques dans une matrice magnétique d’hydroxide simple lamellaire. Durant cette thèse a été démontré la faisabilité de la fonctionnalisation d’hydroxides simples lamellaires de cuivre et de cobalt par des molécules possédant des fonctions d’accroche acide phosphonique. Le développement des techniques de pré-fonctionnalisation a permis de fonctionnaliser ces hydroxides simple lamellaire par une variété importantes de molécules (fluorènes, benzènes, thiophènes et complexes de métaux de transition) afin d’apporter une propriété additionnelle au magnétisme de l’hydroxyde. Les premières mesures ont permis de mettre en évidence un couplage entre temperature d’ordre magnétique et anomalie diélectrique. La complexité de la mesure des propriétés diélectriques avec ces échantillons (sur poudre pastillées à froid) ont mis en lumière la nécessité d’obtenir des tailles de cristallites plus importantes. Des efforts sur la taille des cristallites ont donc été effectués et ont permis d’obtenir des monocristaux d’hydroxy- dodecylsulfate de cuivre. / The main goal of this thesis is to obtain multiferroic materials via the intercalation of organic molecules in a magnetic inorganic matrix made of layered simple hydroxide. The possibility to use phosphonic acid as grafting moiety for the functionalization of layered simple hydroxides has been demonstrated during this thesis. Pre-functionalization techniques has allowed the functionalization of layered simple hydroxides of copper and cobalt with a wide variety of molecules (fluorenes, benzenes, thiophenes or transition- metal complexes) to bring an additional property to the magnetic properties of the layered hydroxide. The first measurements revealed a coupling between magnetic ordering temperature and dielectric anomaly. The dielectric properties measurements proved to be difficult with the samples (on cold-pressed pellets) and shown the usefulness of developing new methods to improve the cristallite size. To that end, new syntheses procedures led to the obtention of mono crystals of copper-hydroxidodecylsulfonate allowing to get additional structural informations.
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The Effects of Fiber Orientation State of Extrusion Deposition Additive Manufactured Fiber-Filled Thermoplastic PolymersPasita Pibulchinda (9012281) 25 June 2020 (has links)
<p>Extrusion
Deposition Additive Manufacturing (EDAM) is a process in which fiber-filled
thermoplastic polymers are mixed and melted in an extruder and deposited onto a
build plate in a layer-by-layer basis. Anisotropy caused by flow-induced
orientation of discontinuous fibers along with the non-isothermal cooling
process gives rise to internal stresses in printed parts which results in part
deformation. The deformation and residual stresses can be abated by modifying
the fiber orientation in the extrudate to best suit the print geometry. To that
end, the focus of this research is on understanding the effect of fiber
orientation state and fiber properties on effective properties of the printed
bead and the final deformation of a part. The properties of three different
orientation tensors of glass fiber-filled polyamide and carbon fiber-filled
polyamide were experimentally and virtually characterized via micromechanics. A
thermo-mechanical simulation framework developed in ABAQUS© was used to
understand the effects of the varying fiber orientation tensor and fiber
properties on the final deformation of printed parts. In particular, a
medium-size geometry that is prone to high deformation was simulated and
compared among the three orientation tensors and two material systems. This
serves to be a good preliminary study to understand microscopic properties induced
deformations in EDAM.</p>
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