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1
Kulovaná, Eva. "Vliv rozpouštědla na deformační chování hydrogelů." Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2021. http://www.nusl.cz/ntk/nusl-437980.
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The thesis deals with molecular dynamic simulation of the influence of water on the deformation of hydrogels. Hydrogels are model materials formed from macromolecular networks solvated with water. It was found that water can form bridges between macromolecules that take the form of temporary ionic crosslinks. These bridges affect the behavior of the network during deformation. Water bridges are water molecules that have a limited radius of motion in the space between two macromolecules. The concentration of the water bridges was regulated by a partial charge on the macromolecular chain in the organic network. Bridges are a type of interaction that is relatively strong but significantly delocalized. It is not possible to dissociate the water bridge, after dissociation it will be re-created in another place in a short time. The influence of water bridges was compared with other types of network crosslinks, especially covalent and physical bonds. Covalent crosslinks are modeled as a simple binding interaction between two macromolecules. They are undissociable and are local throughout the simulation. Physical bonds are modeled as micelles, where hydrophobic groups form the core and hydrophilic groups form the micelle shell. Physical bonds have the nature of dissociable bonds that are local. Different types of crosslinks have different effects on deformation properties. The deformation of a network containing a combination of two types of crosslinks was simulated: (i) physically-covalent, (ii) ionically-covalent, and (iii) physically-ionic networks and (iv) ternary physically-covalent-ion networks. For individual and combined networks, the behavior depending on simple networks was verified. The number of water bridges was fundamentally affected by the primary structure of the chains. When the PEG chain was replaced with hydrophobic polyoxymethylene (POM) or polyoxytrimethylene (POTM), their solvation and mechanical behavior deteriorated.
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Klímová, Eliška. "Mechanické a transportní vlastnosti hybridních hydrogelových systémů." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2021. http://www.nusl.cz/ntk/nusl-444534.
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This master´s thesis deals with the study on mechanical and transport properties of hybrid hydrogel systems. Considering applications of hydrogels, especially in chemical industry, pharmacy, or eventually medical applications, for the study gellan and alginate-based hydrogels were selected. In order to compare individual characteristics physical and hybrid hydrogels were prepared. Gellan hydrogels were prepared in deionization aqua solution, calcium chloride dihydrate and tween 80 solution. Alginate hydrogels were prepared in calcium chloride dihydrate solution as well, and polyacrylamide with N,N´–methylenbisacrylamide. For the study of mechanical properties moisture analyser and rheology measurements were selected. Transport properties were studied using the diffusion experiments combined with UV-VIS spectroscopic detection. Concluding of this thesis is summarization of measured values, which provides comprehensive review of the problematics. It was discovered that the conveniently selected concentrations of structural components of hydrogel matrix and the additives can influence both the mechanical as well as the transport properties of studied hydrogels.
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Echalier, Cécile. "Conception de matériaux hybrides peptidiques biomimétiques." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT213.
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Nous avons imaginé et développé une méthode pour la préparation d’hydrogels par procédé sol-gel à partir de blocs hybrides (bio)organiques-inorganiques. Les blocs hybrides sont obtenus par introduction de groupements silylés, triéthoxysilanes ou hydroxydiméthylsilanes, sur des polymères synthétiques ou des molécules d’intérêt biologique telles que des peptides. Ces blocs hybrides peuvent être combinés dans des proportions choisies pour former des hydrogels multifonctionnels. Le procédé de gélification se déroule à 37°C à pH 7.4 dans un tampon physiologique. L’hydrolyse et la condensation des précurseurs silylés conduit à la formation d’un réseau tridimensionnel covalent dans lequel les entités organiques sont reliées par des liaisons siloxanes. Dans un premier temps, cette méthode a été appliquée à la synthèse d’hydrogels à base de PEG. Nous avons ensuite montré que ces hydrogels pouvaient être fonctionnalisés de façon covalente par des entités bioactives au cours de leur préparation. Des hydrogels possédant des propriétés antibactériennes ou favorisant l’adhésion cellulaire ont ainsi été préparés. Dans un deuxième temps, un peptide hybride inspiré du collagène naturel a été synthétisé et a permis l’obtention d’hydrogels qui présentent des propriétés de prolifération cellulaire similaires à celles observées sur des substrats de collagène naturel. La biocompatibilité du procédé sol-gel a été démontrée par l’encapsulation de cellules souches dans l’hydrogel au cours de sa formation. Enfin, l’impression 3D d’hydrogels hybrides a été réalisée. Ce travail de thèse met donc en lumière le potentiel de la chimie sol-gel pour la conception à façon de matériaux biomimétiques particulièrement prometteurs pour des applications en ingénierie tissulaire<br>We designed and developed a method for the preparation of hydrogels through the sol-gel process. It is based on (bio)organic-inorganic hybrid blocks obtained by functionalization of synthetic polymers or bioactive molecules, such as peptides, with silyl groups (triethoxysilanes or hydroxydimethylsilanes). These hybrid blocks can be combined in desired ratio and engaged in the sol-gel process to yield multifunctional hydrogels. Gelation proceeds at 37°C at pH 7.4 in a physiological buffer. Hydrolysis and condensation of silylated precursors result in a three-dimensional covalent network in which molecules are linked through siloxane bonds. First, this method was applied to the synthesis of PEG-based hydrogels. Then, we demonstrated that hydrogels could be covalently functionalized during their formation. Thus, hydrogels exhibiting antibacterial properties or promoting cell adhesion were obtained. Secondly, a hybrid peptide whose sequence was inspired from natural collagen was synthesized and used to prepare hydrogels that provided a cell-friendly environment comparable to natural collagen substrates. Stem cells could be encapsulated in these hydrogels with high viability. Finally, hybrid hydrogels were used as bio-inks to print 3D scaffolds. This PhD work highlights the potential of the sol-gel chemistry for the design of tailor-made biomimetic scaffolds that could be particularly promising for tissue engineering applications
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Cornwell, Daniel. "Hybrid and multi-component hydrogels." Thesis, University of York, 2016. http://etheses.whiterose.ac.uk/15426/.
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Low-molecular-weight gelators (LMWGs) form a network via non-covalent interactions to immobilise the surrounding bulk solvent and form a gel. Whilst such gels are highly responsive and dynamic, they are often mechanically weak. In order to enhance the mechanical strength of such networks, the LMWG network can be supplemented with a second network formed from stronger polymer gelators (PGs) to yield a multi-component, multi-functional material – a hybrid gel. By using this multi-functionality, hybrid gels were made that could demonstrate the following: a) robustness yet responsiveness, b) spatial control over the formation of one network in the presence of another, and c) temporal control over the formation of one network in the presence of another. For the first aim, a pH-responsive LMWG (1,3:2,4-dibenzylidene-D-sorbitol dicarboxylic acid, DBS-CO2H) was combined with the robust PG agarose. The assembly of DBS-CO2H in the presence and absence of agarose was investigated by NMR and CD spectroscopies, whilst materials properties were examined by rheology. DBS-CO2H was found to retain its pH-responsive character, as was demonstrated by cycling the pH within the gel – whilst the DBS-CO2H network could be switched “on” or “off”, the robust agarose network remained intact. Following this, DBS-CO2H was combined with the photo-inducible PG poly(ethylene glycol) dimethacrylate (PEGDM). Spectroscopic methods and electron microscopy showed that the kinetics and morphology of DBS-CO2H assembly were impacted by the presence of PEGDM. The application of a mask during photoirradiation allowed patterning of the PEGDM network to form a material with two distinct, spatially-resolved regions, defined as a “multidomain gel”, achieving the second aim. The different domains had different properties with regards to the diffusion and release of dyes. DBS-CO2H was then combined with another pH-responsive LMWG (1,3:2,4-dibenzylidene-D-sorbitol-dicarbonyl-glycine, DBS-Gly). The two gelators showed a good degree of kinetic self-sorting, their self-assembly being triggered at different pHs. It was possible to use two proton sources – the slow hydrolysis of glucono-δ-lactone, and the more rapid photoacid generator diphenyliodonium nitrate – to achieve a two-step process of network formation. As the second step was UV-initiated, photopatterned multi-component gels were produced; these materials were both spatially and temporally resolved, achieving the third aim. Finally, the combination of DBS-CO2H, DBS-Gly and PEGDM into a three-gelator, multi-component hybrid hydrogel was investigated.
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Bellosta, von Colbe José M. "Hydrogen storage in light metal hybrides." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=97890365X.
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Zarzar, Lauren Dell. "Dynamic Hybrid Materials: Hydrogel Actuators and Catalytic Microsystems." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:10867.
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Dynamic materials which can sense changes in their surroundings and subsequently respond or adapt by autonomously altering their functionality, surface chemistry, transparency, color, wetting behavior, adhesiveness, shape, etc. are primed to be integral components of future "smart" technologies. However, such systems can be quite complex and often require intricate coordination between both chemical and mechanical inputs/outputs as well as the combination of multiple materials working cooperatively to achieve the proper functionality. It is critical to not only understand the fundamental behaviors of existing dynamic chemo-mechanical systems, but also to apply that knowledge and explore new avenues for design of novel materials platforms which could provide a basis for future adaptive technologies. Part 1 explores the use of environmentally-sensitive hydrogels, either alone or within arrays of high-aspect-ratio nano/microstructures, as chemo-mechanical actuators. Chapters 1 through 7 describe a bio-inspired approach to the design of hybrid actuating surfaces in which the volume-changing hydrogel acts as the “muscle” that reversibly actuates the microstructured "bone". In particular, the different actuation mechanisms arising from variations in how the hydrogel is integrated into the structure array, how chemical signals can be used to manipulate actuation parameters, and finally how such a system may be used for applications ranging from adaptive optics to manipulation of chemical reactions are described. Chapter 8 discusses the use of responsive hydrogel scaffolds as a means to mechanically compress cells and direct differentiation. Part II explores dynamic microsystems involving the integration of catalytic sites within intricately structured 3D microenvironments. Specifically, we explore a generalizable and straightforward route to fabricate microscale patterns of nanocrystalline platinum and palladium using multiphoton lithography. The catalytic, electrical, and electrochemical properties are characterized, and we demonstrate high resolution integration of catalysts within 3D-defined microenvironments to generate directed particle and fluid transport.<br>Chemistry and Chemical Biology
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Abdallah, Ibrahim. "Event-driven hybrid bond graph : Application : hybrid renewable energy system for hydrogen production and storage." Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10104/document.
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Ce travail de thèse constitue une contribution à la modélisation et au diagnostic des systèmes multi-domaines à commutation (hybrides). Il est appliqué à la supervision des systèmes multi-sources d’énergie propre où l’hydrogène est utilisé comme moyen de stockage. Un tel système associe des composantes énergétiques de nature différente et fait l’objet de commutations produites par la connexion et déconnexion d’un ou plusieurs composants. Ces commutations génèrent différents modes de fonctionnement et sont liées à l’intermittence des sources primaires, aux capacités de stockage et à la disponibilité opérationnelle des ressources matérielles qui constituent le système. La présence de ces commutations engendre une dynamique variable qui est classiquement difficile à exprimer mathématiquement sans exploiter tous les modes. Ces difficultés de modélisation se propagent pour affecter toutes les tâches dépendantes du modèle comme le diagnostic et la gestion de modes de fonctionnement. Pour résoudre ces problématiques, un nouvel outil, Bond Graph Hybride piloté par événements, a été développé. Entièrement graphique, ce formalisme permet une modélisation interdisciplinaire globale du système. En séparant la dynamique continue gérée par le Bond Graph Hybride des états discrets modélisés par un automate intégré, l’approche proposée simplifie la gestion des modes de fonctionnement. Le modèle issu de cette méthodologie est également bien adapté au diagnostic robuste, réalisable sans recourir aux équations analytiques. Associée au diagnostic robuste, cette gestion des modes permet l’implémentation de stratégies de reconfiguration et de protection en présence de défaillances<br>This research work constitutes a general contribution towards a simpler modelling and diagnosis of the multidisciplinary hybrid systems. Hybrid renewable energy systems where hydrogen is used to store the surplus of the power fits perfectly under this description. Such system gathers different energetic components that are needed to be connected or disconnected according to different operating conditions. These different switching configurations generate different operating modes and depend on the intermittency of the primary sources, the storage capacities and the operational availability of the different hardwares that constitute the system. The switching behaviour engenders a variable dynamic which is hard to be expressed mathematically without investigating all the operating modes. This modelling difficulty is transmitted to affect all the model-based tasks such as the diagnosis and the operating mode management. To solve this problematic, a new modelling tool, called event-driven hybrid bond graph, is developed. Entirely graphic, this formalism allows a multidisciplinary global modelling for all the operating modes at once. By separating the continuous dynamic driven by the bond graph, from the discrete states handled by an integrated automaton, this approach simplifies the management of the operating modes. The model issued using this methodology is also well-adapted to perform a robust diagnosis which is achievable without referring back to the analytical description of the model. The operating mode management, when associated with the on-line diagnosis, allows the implementation of reconfiguration strategies and protection protocols when faults are detected
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Benge, Kathryn Ruth. "Hybrid Solid-State Hydrogen Storage Materials." The University of Waikato, 2008. http://hdl.handle.net/10289/2320.
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This thesis investigates the chemistry of ammonia borane (NH3BH3) relevant to the development of hydrogen storage systems for vehicular applications. Because of its high hydrogen content and low molecular weight ammonia borane has the potential to meet stringent gravimetric hydrogen storage targets of gt;9 wt%. Two of the three moles of H2 in ammonia borane can be released under relatively mild conditions, with the highest gravimetric yield obtained in the solid-state. However, ammonia borane does not deliver sufficient H2 at practical temperatures and the products formed upon H2 loss are not amenable to regeneration back to the parent compound. The literature synthesis of ammonia borane was modified to facilitate large scale synthesis, and the deuterated analogues ND3BH3 and NH3BD3 were prepared for the purpose of mechanistic studies. The effect of lithium amide on the kinetics of dehydrogenation of ammonia borane was assessed by means of solid-state reaction in a series of specific molar ratios. Upon mixing lithium amide and ammonia borane, an exothermic reaction ensued resulting in the formation of a weakly bound adduct with an H2N...BH3-NH3 environment. Thermal decomposition at or above temperatures of 50eg;C of this phase was shown to liberate gt;9 wt% H2. The mechanism of hydrogen evolution was investigated by means of reacting lithium amide and deuterated ammonia borane isotopologues, followed by analysis of the isotopic composition of evolved gaseous products by mass spectrometry. From these results, an intermolecular multi-step reaction mechanism was proposed, with the rates of the first stage strongly dependent on the concentration of lithium amide present. Compounds exhibiting a BN3 environment (identified by means of solid-state sup1;sup1;B NMR spectroscopy) were formed during the first stage, and subsequently cross link to form a non-volatile solid. Further heating of this non-volatile solid phase ultimately resulted in the formation of crystalline Li3BN2 - identified by means of powder X-ray diffractometry. This compound has been identified as a potential hydrogen storage material due to its lightweight and theoretically high hydrogen content. It may also be amenable to hydrogen re-absorption. The LiNH2/CH3NH2BH3 system was also investigated. Thermal decomposition occurred through the same mechanism described for the LiNH2/NH3BH3 system to theoretically evolve gt;8 wt% hydrogen. The gases evolved on thermal decomposition were predominantly H2 with traces of methane detected by mass spectrometry.
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Montheil, Titouan. "Conception d’hydrogels hybrides pour la préparation de géloses synthétiques." Thesis, Montpellier, 2020. http://www.theses.fr/2020MONTS012.
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Des hydrogels hybrides ont été développés comme alternative aux hydrogels d’agar utilisés en microbiologie. Notre stratégie repose sur la fonctionnalisation de polymères avec des groupements triéthoxysilanes, puis leurs mises en jeu dans le procédé sol-gel afin de fabriquer un hydrogel hybride organique-inorganique. Ce procédé est bio-orthogonal et biocompatible. Il se déroule en milieu aqueux, à pH physiologique et température ambiante. Dans une première partie, nous avons développé des hydrogels à base de PEG bisilylé. Nous avons montré que l’incorporation de PEG monosilylé permettait un relâchement du réseau de l’hydrogel. Dans une seconde partie, nous avons développé des hydrogels à base d’hydroxypropyl méthyl cellulose (HPMC). L’optimisation de la silylation de ce composé a été réalisée. L’étude de la composition de l’hydrogel (masse molaire de l’HPMC, concentration, taux de silylation) a été étudiée et a permis la préparation d’hydrogels aux propriétés similaires aux références commerciales d’agar. Nous avons ensuite étendu notre étude aux hydrogels hybrides à base d’autres polysaccharides. Le chitosan, la dextrine, la pectine et l’acide hyaluronique ont ainsi été silylés et des hydrogels hybrides ont été préparés à partir de ces précurseurs. Les hydrogels de dextrine silylée se sont révélés les plus prometteurs pour une application à la microbiologie. La composition a été optimisée et les tests microbiologiques ont validé ce composé comme une alternative à l’agar.Nous avons montré que les hydrogels synthétiques obtenus par le procédé sol-gel constituaient une alternative solide aux hydrogels d’agar. La maitrise des différents paramètres (ex : silylation, mise en forme, composition) permet d’adapter leurs propriétés<br>Hybrid hydrogels have been developed as an alternative to agar hydrogels used in microbiology. Our strategy is based on the functionalization of polymers with triethoxysilane groups, and then their use in the sol-gel process to produce an organic-inorganic hybrid hydrogels. This process is bio-orthogonal and biocompatible. It takes place in aqueous medium, at physiological pH and ambient temperature. In a first part, we developed hydrogels based on bisilylated PEG. We have shown that the incorporation of monosilylated PEG allowed a loosening of the hydrogel network. In a second part, we developed hydrogels based on hydroxypropyl methyl cellulose (HPMC). Silylation of HPMC silylation has been optimised. The study of hydrogel composition (HPMC molecular weight, concentration, silylation rate) allowed the production of hydrogels with properties similar to the agar commercial references. We then extended our study to hybrid hydrogels made from others polysaccharides. Chitosan, dextrin, pectin and hyaluronic acid were thus silylated and hybrid hydrogels were prepared from these precursors. Silylated dextrin hydrogels proved to be highly suitable for microbiology applicationWe showed that synthetics hydrogels obtained by sol-gel process constituted a solid alternative to agar hydrogels. The control of the various parameters (e.g. silylation, shaping, composition) makes it possible to prepare hydrogels with tunable properties
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Baumann, Bernhard Harry [Verfasser]. "Synthese und Charakterisierung hybrider Hydrogele für die Geweberekonstruktion / Bernhard Harry Baumann." Ulm : Universität Ulm, 2018. http://d-nb.info/1166757315/34.
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Eksteen, Zaskia-Hillet. "Hybrid hydrogels based on RAFT mediated poly(N-vinyl pyrrolidone)." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/4822.
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Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2009.<br>Thesis submitted in partial fulfilment for the degree of
Master of Science (polymer science)
at
Stellenbosch University<br>ENGLISH ABSTRACT: The goal of this study was to synthesize hybrid hydrogels via a chemical crosslinking mechanism through use of chain end functional poly(N-vinyl pyrrolidone)(PVP) with
various topologies. The crosslinking chemistries should be benign in nature i.e. at physiological pH ranges and at 37 °C. The degradation products should be biologically tolerable and renal clearance should be possible (< 30 000 g/mol PVP0. PVP of various topologies, controlled molar mass and quantitative chain end
functionality was obtained via Reversible Addition Fragmentation chain Transfer
(RAFT) mediated polymerization (PDI = 1.1- 1.4).
The synthesized polymers were chain end functionalized to introduce thiol or
aldehyde moieties. Thiol chain ends were obtained through post polymerization modification of xanthate functional PVP with either aminolysis or reduction. The aldehyde moiety was obtained by post polymerization modification of xanthate end
functional PVP with sequential hydrolysis and thermolysis. Thiol functional four arm star PVP was reacted with acrylate difunctional
poly(ethylene glycol) (DIAC PEG) crosslinker under standard Michael addition conditions. In order to obtain thioether crosslinked hydrogels from tetra functional star PVP molecules it was found that a minimum thiol functionalization of 30% and a molar ratio of acrylate:thiol of 1:1.1 is required. The Schiff base reaction was used to synthesize imine or secondary amine (after
reduction) crosslinks with the lysine residues on either lysozyme or bovine serum albumin (BSA) or the primary amines of bis-(2-amino ethyl)amine). Hydrogels were obtained from aldehyde functionalized PVP molecules with a fraction of functional aldehyde chain ends of 0.88 for difunctional molecules and 0.50 for tetra functional star PVP molecules with lysozyme or BSA crosslinkers. The reaction rate was
favoured by lowered pH (<6.0) and an optimum molar ratio of amine : aldehyde of 1:0.8.
Hydrogels were analyzed by equilibrium swelling calculations to determine the molar mass between crosslinks and the estimated pore size. In both crosslinking systems the properties of the formed hydrogels were seen to be affected by molar ratio used and by the topology of the crosslinking agent. PVP BSA and PVP PEG hydrogels were tested for 24 h and 48 h cell viability by using
H9C2 myoblast cells. A concentration range of 0.25 x 10(2) to 0.01 g/mL was studied. Cell mortality was tested by Trypan blue staining and results were verified with MTT assay. A very low cell death precentage (<37%)was observed. Cells even appeared to experience a stimulatory effect after 48 h of exposure at low concentrations of
PVP PEG hydrogel treatments. The properties of the formed hydrogel could be tuned by the molar mass ratios of PVP and crosslinker. The functionality of the crosslinker directly affects the molar mass between crosslinks and thus indirectly the degradation profile. It was concluded that PVP molecules with various topologies, well-defined molar masses and chain end functionality could be obtained via RAFT mediated polymerization. Obtained polymers were successfully modified and crosslinked to
obtain hydrogels with stoichiometrically tuneable properties i.e. initial swelling ratio,
degradation time, molar mass between crosslinks. The hydrogels had very positive cell viability results that would definitely justify further research into these materials as “tissue-mimetic” materials.<br>AFRIKAANSE OPSOMMING: Die doel van die studie is om poli(N-viniel pirollidoon) (PVP) gebaseerde hibried hidrogelle te sintetiseer deur middel van kovalente kruisbindings met toepaslike
kruisverbinder molekules. Die chemiese reaksies betrokke in die vorming van hierdie kovalente kruisbindings moet gematig van aard wees, by fisiologiese pH en by 37 °C plaasvind. Die degradasieprodukte van die hibried-hidrogel moet biologies verdraagsaam en ook uitskeibaar deur die endokrinologiese sisteem wees. PVP van verskillende topologieë, beheerde molêre massa en kwantitatiewe kettingendfunksionaliteit is berei deur ‘n omkeerbare addisie-fragmentasiekettingoordrag (OAFO)-beheerde polimerisasieproses (PDI = 1.1-1.4).
Xantaat-kettingend-PVP is aangepas na thiol of aldehied kettingendfunksies. Thiolendfunksies
is verkry deur middel van ‘n aminolisasie-reaksie. Xantaat kettingend-PVP is stapsgewys gemodifiseer deur hidroliese en verhittingstappe om die aldehied ketting-endfunksionaliteit te bekom. Thiol ketting-endfunksionele vier-armige ster-PVP is kovalent gebind aan difunksionele poly(etileen glikol) deur middel van die Michael-addisiereaksie. PVP PEG hidrogelle het slegs gevorm met vier-armige ster-PVP molekules wat oor ‘n minimum van 30 % thiol-funksionaliteit beskik het en ‘n optimale molêre massa
verhouding van 1:1.1 vir ankrilaat to thiol.
Die Schiff-basisreaksie is gebruik om hidrogel te sintetiseer wat met imiene of amiene (na redusering) kovalente bindings gekruisbind is. In hierdie sisteme het hidrogel slegs gevorm as die aldehied-PVP molekules oor ‘n fraksie funksionele
kettingend-waarde van 0.88 vir dialdehied-PVP molekules en 0.5 vir vier armige ster-PVP molekules beskik het. Die reaksie snelheid van die Schiff-basis kovalente bindings is bevoordeel deur die pH te verlaag (≤ 6.0) en ‘n gunstige molêre massa verhouding van 1:0.8 vir die
nukleofiel teen oor die akseptor molekule is waargeneem. Ewewigswel berekeninge is gebruik om die molêre massa tussen kruisbindings en die
gemiddelde benaderde porieë binne die drie-dimensionele interne struktuur van die
hydrogel te bepaal. Die seltoksisiteit van PVP-BSA en PVP-PEG hidrogelle is oor 24 h en 48 h in die teenwoordigheid van H9c2 mioblast-selle getoets. Die hydrogel behandelings is
uitgevoer in ‘n konsentrasie reeks van 0.25 x
10(2) tot 0.01 g/mL. Selmortaliteit is getoets deur ‘n Trypan-blou verkleuringstudie. Hierdie resultate is ondersteun deur MTT sel-lewensvatbaarheidstoetse. ‘n Lae selmortaliteit (≤ 37 %) is waargeneem en, opspraakwekkend, het van die selle na 48 h verhoogde vitaliteit getoon in die teenwoordigheid van lae konsentrasies PVP-PEG hidrogelle. Dit is bevind dat hidrogel eienskappe deur stoichiometriese molêre massa
verhoudings asook die keuse in die topologie van kruisverbinder beïnvloed word. Hierdie eienskappe het ‘n direkte effek op die degradasieprofiel van die gevormde hidrogel.
Samevattend dus is PVP molekules met ‘n variasie van topologieë, spesifieke molêre massas en kettingfunksionalitete deur middel van OAFO-gemedieerde polimerisasies gesintetiseer. Xantaatkettingendfunksionele PVP-molekules kon suksesvol omgeskakel word na die kettingendfunksionaliteit van ons keuse om ‘n hibriedhidrogel met stoichiometries-manupileerbare eienskappe te sintetiseer. Die positiewe sel-lewensvatbaarbheidstudie resultate staaf verdere ondersoeke in hierdie PVPgebaseerde
hibried hidrogelmateriaal as ‘n weefsel nabootsingsmateriaal.
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Scheler, Thomas Herbert. "Transition-metal-hydrogen systems at extreme conditions." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7611.
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The application of extreme conditions offers a general route for the synthesis of materials under equilibrium conditions. By finely tuning the thermodynamic variables of pressure and temperature one can manipulate matter on an atomic scale, creating novel compounds or changing the properties of existing materials. In particular, the study of hydrogen and hydrogen compounds has attracted the attention of researchers in the past. Although hydrogen readily reacts with many elements at ambient conditions, there is a significant “hydride gap” covering the d-metals between the Cr-group and Cu-group elements. At elevated pressures however, the chemical potential of hydrogen rises steeply. At sufficient pressures, hydrogen overcomes the dissociation barrier at the metal surface and atomic hydrogen diffuses into the metal, usually occupying interstitial sites in the host matrix. These interstitial hydrogen alloys can exhibit interesting physical properties, such as modified crystalline structures, different compressibility, altered microstructure (nanocrystallinity), hydrogen mediated superconductivity or potential hydrogen storage capabilities. Furthermore, theory predicts that hydrogen confined in a host matrix might undergo the elusive transition to a metallic groundstate at considerably lower pressures than pure hydrogen. Most d-metals have been found to exhibit hydride phases at extended conditions of pressure and temperature. However, besides rhenium, the 6th row metals between tungsten and gold, as well as silver, have not or only very recently been found to form bulk hydrides. In the course of this PhD-thesis, several of the missing metalhydrides were successfully synthesized in the diamond anvil cell and characterized by in-situ x-ray diffraction using synchrotron radiation.
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Bourgeteau, Tiphaine. "Development of hybrid photocathodes for solar hydrogen production." Palaiseau, Ecole polytechnique, 2015. https://tel.archives-ouvertes.fr/tel-01215429v1/document.
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L’utilisation des énergies renouvelables, qui sont intermittentes, à l’égal des énergies fossiles (échelle du TW) doit passer par leur conversion et stockage en un vecteur transportable. L’hydrogène semble le vecteur énergétique idéal qui peut être produit à partir de l’eau et de l’énergie solaire. Ce carburant peut ainsi être stocké, transporté puis utilisé à la demande en le combinant avec l’oxygène dans une pile à combustible. Les cellules photo-électrochimiques (PEC) utilisées pour la conversion ne sont actuellement pas rentables car les matériaux majoritairement utilisés pour leur fabrication, tels que le platine et les semiconducteurs cristallins, sont rares ou chers. Le point clé est de trouver des matériaux qui soient disponibles en grande quantité et facilement mis en forme. Ce travail de thèse concerne le développement d’une photocathode sans matériau rare pour la photoproduction de H2 via la réduction des protons à partir de l’énergie solaire et de l’eau. Pour cela, une cellule solaire à hétérojonction polymère-fullerène (P3HT:PCBM) a été couplée directement à un catalyseur sans métal précieux, MoS3. La cellule solaire absorbe les photons, et les électrons photogénérés sont ensuite acheminés jusqu’au catalyseur qui les utilise pour produire l’hydrogène. Après avoir étudié chacun des matériaux (cellule solaire et catalyseur) séparément et vérifié le bon alignement des niveaux énergétiques, les premiers assemblages ont été faits par des procédés en solution. Les méthodes de dépôt ont dû être adaptées en fonction de la nature des matériaux. Ainsi, le spin-coating et le spray ont été utilisés respectivement pour déposer la partie photovoltaïque et le catalyseur. Les caractérisations photo-électrochimiques mises en place ont permis de mettre en évidence la présence d’un photo-courant (100 µA cm–2) correspondant à la production d’hydrogène, qui a été analysé par chromatographie en phase gazeuse. Ces résultats ont permis de montrer la viabilité des photocathodes hybrides sans matériau noble. Afin d’augmenter les performances des photocathodes, de nouvelles configurations ont été conçues. Dans un premier temps des matériaux d’interface entre la couche mince photovoltaïque et le catalyseur ont été étudié (couche extractrice d’électrons, CEE) pour améliorer la collection des électrons photogénérés par le catalyseur. Parmi les métaux étudiés, l’aluminium protégé par le titane a permis d’atteindre des photocourants de 10 mA cm–2. Cependant la présence de l’aluminium induisait une instabilité en milieu aqueux, aussi des oxydes (TiOx) et des matériaux organiques (fullerène C60 et graphène) ont été envisagés. Le TiOx n’a permis qu’une légère amélioration par rapport aux photocathodes sans CEE, tandis que le C60 a permis d’atteindre 5 mA cm–2 mais avec une stabilité moindre par rapport aux CEE métalliques. L’origine de l’amélioration des performances a été attribuée à l’isolement de la jonction photovoltaïque par rapport à l’électrolyte. Dans une deuxième approche, la couche extractrice de trous (CET) située entre l’électrode transparente et le P3HT:PCBM a été remplacée par des oxydes amorphes (oxyde de graphène (GO), MoOx, NiOx). Ce changement a permis la réalisation de photocathodes performantes et stables pendant plusieurs heures, avec des températures de dépôt ne dépassant pas 150 °C dans le cas du MoOx et du GO. L’augmentation des performances semblant aller de pair avec l’augmentation du travail de sortie de la CET, il a été suggéré que la différence des niveaux de Fermi de la CET et de l’électrolyte avait un impact sur la capacité de la photocathode à séparer les charges et les utiliser pour la photocatalyse. Les photocathodes avec MoOx (matériau testé avec le plus grand travail de sortie) ont les meilleurs rendements (plusieurs mA cm–2 et un photovoltage de 0. 6 V), et présentent une plus grande stabilité par rapport aux photocathodes ayant une CTE métallique<br>One of the challenges of the 21st century is to produce clean and inexpensive energy at the TW scale to face the increasing energy demand and the global climate change. Because renewable energies are intermittent, they must be converted and stored in order to use them at the same scale of fossil energies. Hydrogen appears to be an ideal energy carrier when it is produced from water and sunlight. This fuel can be stored, transported and use on-demand by its combination with oxygen, for example in a fuel cell. Photo-electrochemical (PEC) cells able to carry out the photo-electrolysis of water are not yet cost-effective, because most of the materials used for their fabrication are rare or expensive (platinum, crystalline semiconductors). Producing hydrogen in a PEC cell at industrial scale depends on the finding of readily-available and easily-processed materials. In this thesis, the development of a noble-metal free hydrogen-evolving photocathode was undertaken, to reduce protons from light and acidic water. The photo-converting unit was based organic semiconductors organized in a polymer-fullerene bulk-heterojunction layer (P3HT:PCBM) coupled to amorphous molybdenum sulfide (MoS3) as a catalyst. In the device, the P3HT:PCBM layer absorbs the photons and the photogenerated electrons are then transported to the interface with the catalyst, which uses the electrons to produce hydrogen. After studying each material (catalyst and solar cell) separately and checking the alignment of their energy levels, the first assemblies were made by solution processes. The deposition methods were adapted depending on the nature of the materials. Spin-coating and spray were used for the deposition of the light-harvesting unit and the catalyst, respectively. With the photo-electrochemical characterization setup, a photocurrent of up to 100 µA cm–2 was obtained, corresponding to production of hydrogen, as analyzed by gas chromatography. These first results proved the viability of the concept of this hybrid noble-metal free photocathode. In order to improve the photocathode performance, new configurations were designed. Firstly, interfacial materials placed between P3HT:PCBM and MoS3 (electron-extracting layer, EEL) were studied to improve charge collection by the catalyst. Among studied materials, photocathodes with titanium-protected aluminum reached up to 10 mA cm–2 of photocurrent. The presence of aluminum induced instability in aqueous media, so that oxides (TiOx) and organic materials (C60 fullerene and graphene) were considered. TiOx brought only a slight improvement compared to photocathodes without EELs, while C60 allowed to reach 5 mA cm–2 but with a lower stability compared to metallic EELs. The origin of the increased performances with EELs was attributed to the burying of the photovoltaic junction, removing the influence of the electrolyte. Secondly, the material between the transparent electrode and the photovoltaic part, i. E. The hole-extracting layer (HEL), was replaced by amorphous oxides (graphene oxide (GO), MoOx, NiOx). It led to the fabrication of performant photocathodes, stables for several hours, by process temperatures below 150 °C in the case of MoOx and GO. The increase of the performance seemed to be related to the increase of the HEL work function, leading to the suggestion that the Fermi level difference between the HEL and the electrolyte has an impact on the capacity of the photocathode to separate the charges and use them for photocatalysis. The most performant photocathodes (several mA cm–2 and 0. 6 V of photovoltage) were the one with MoOx, i. E. The material with the largest work function, and had a much better stability than the photocathodes with metallic EELs
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Clarke, David. "'Smart' self-assembled β-sheet poly (γ-glutamic acid) hybrid hydrogels". Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/24728.
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Hybrid materials have been found to be possessed with unique and novel properties, by superimposing the advantages of each component to provide material properties far superior to the individual constituents alone. These types of material are used throughout the field of bioengineering, and can facilitate biological interactions on both a molecular and cellular level, responding to biological and mechanical queues. With these inherent unique properties these materials provide novel platforms to help repair, replace and regenerate body tissues and function. This thesis explores the synthesis of new 'smart' hybrid hydrogels and their properties. Through the conjugation of self-assembling β-sheet peptide sequences to a naturally occurring poly (γ-glutamic acid) polymer backbone, peptide-polymer hybrid hydrogels were formed. These hybrid hydrogels were attributed with robust and tunable mechanical properties. Through the reassembly of the physical β-sheet crosslinks the hydrogels can respond to their mechanical environment, exhibiting 'self-healing' capabilities and a resistance to cyclic strain. Also, being composed entirely of natural peptide bonds they have excellent biocompatibility and are a promising platform for future tissue engineering scaffolds and biomedical applications. These hybrid hydrogels were further functionalised to detect for the activity of enzymatic biomarkers. A simple assay based on Förster resonance energy transfer was incorporated in to the hydrogel platform through the immobilisation of quantum dots modified with peptide substrates. The activity of matrix metalloproteinase-7 was targeted specifically, a marker for inflammation and immunity. This hydrogel sensing platform provides a basis for the in vivo sensing of enzymes and also, the potential to be used as a powerful tool to investigate biological processes in vitro.
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Marpu, Sreekar B. "Biocompatible Hybrid Nanomaterials Involving Polymers and Hydrogels Interfaced with Phosphorescent Complexes and Toxin-Free Metallic Nanoparticles for Biomedical Applications." Thesis, University of North Texas, 2011. https://digital.library.unt.edu/ark:/67531/metadc84243/.
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The major topics discussed are all relevant to interfacing brightly phosphorescent and non-luminescent coinage metal complexes of [Ag(I) and Au(I)] with biopolymers and thermoresponsive gels for making hybrid nanomaterials with an explanation on syntheses, characterization and their significance in biomedical fields. Experimental results and ongoing work on determining outreaching consequences of these hybrid nanomaterials for various biomedical applications like cancer therapy, bio-imaging and antibacterial abilities are described. In vitro and in vivo studies have been performed on majority of the discussed hybrid nanomaterials and determined that the cytotoxicity or antibacterial activity are comparatively superior when compared to analogues in literature. Consequential differences are noticed in photoluminescence enhancement from hybrid phosphorescent hydrogels, phosphorescent complex ability to physically crosslink, Au(I) sulfides tendency to form NIR (near-infrared) absorbing AuNPs compared to any similar work in literature. Syntheses of these hybrid nanomaterials has been thoroughly investigated and it is determined that either metallic nanoparticles syntheses or syntheses of phosphorescent hydrogels can be carried in single step without involving any hazardous reducing agents or crosslinkers or stabilizers that are commonly employed during multiple step syntheses protocols for syntheses of similar materials in literature. These astounding results that have been discovered within studies of hybrid nanomaterials are an asset to applications ranging from materials development to health science and will have striking effect on environmental and green chemistry approaches.
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Fiorini, Federica. "Soft hybrid materials for cell growth and proliferation." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAF027/document.
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Le travail de recherche consiste à développer des hydrogels pour la prolifération et la migration cellulaires in vitro et in vivo en trois dimensions (3D). Des hydrogels à base de polyamidoamines avec d'intéressantes propriétés physicochimiques et une remarquable biocompatibilité ont été développés pour différentes applications biomédicales. Un hydrogel avec des sondes luminescentes d’iridium(III) incorporés de manière covalente, a été conçue comme plate-forme 3D de culture cellulaire, pour la visualisation directe des cellules vivantes en temps réel, et a démontré être un puissant outil de bioimagerie in vitro. En outre, un hydrogel nanocomposite, capable d'induire la chimiotaxie des cellules souches, a été développé et testé in vivo, en confirmant son potentiel en tant qu’implant pour l’ingénierie tissulaire. Finalement, un hydrogel injectable et biodégradable a été réalisé comme un nouvel agent pour la dissection sous-muqueuse endoscopique des lésions néoplasiques digestives<br>The research work focuses on the development of hydrogels to investigate three-dimensional (3D) cell proliferation and migration in vitro and in vivo. Polyamidoamines-based hydrogels with interesting physicochemical properties and high biocompatibility have been developed for different biomedical applications. An hydrogel with covalently incorporated iridium(III) fluorescent probes, has been conceived as a 3D cell culture platform for the direct visualization of living cells in real-time, demonstrating to be a powerful tool for in vitro bio-imaging. Moreover, a nanocomposite hydrogel, able to induce chemotaxis of stem cells, was developed andtested in vivo, confirming its potential as a tissue engineering implant. Finally, an injectable biodegradable nanocomposite hydrogel was realized as a novel agent for endoscopic submucosal dissection of large neoplastic lesions of the gastro-intestinal tract
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Valot, Laurine. "Development of multifonctional hybrid hydrogels for mesenchymal stem cell-based cartilage repair." Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS074.
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Nous avons développé des hydrogels hybrides pour l’encapsulation de cellules souches mésenchymateuses dans la perspective de réparation du cartilage. Notre stratégie repose sur la fonctionnalisation de biopolymères et de molécules actives avec des groupements triéthoxysilanes afin de préparer des hydrogels par un procédé sol-gel. Ce procédé bio-orthogonal, se déroule dans l’eau, à pH physiologique et 37 °C. Dans un premier temps, nous avons mis au point un système de catalyseurs sol-gel biocompatible et étudié les paramètres influençant la cinétique de gélification. Dans un second temps, des peptides hybrides silylés de différentes tailles mimant la séquence du collagène ont été synthétisés. Des hydrogels ont été développés à partir de ces nouveaux blocs biomimétiques. La composition de ces hydrogels a été optimisée afin d’obtenir la meilleur viabilité cellulaire et différentiation chondrocytaire possible après encapsulation. Les propriétés mécaniques de ces hydrogels ont été étudiées révélant un fort impact de la composition. Enfin, ces hydrogels ont été imprimés en 3D par extrusion, et des compositions spécifiques combinant différant biopolymères, ont été développées pour faciliter ce procédé. Au travers des différents exemples d’hydrogels préparés, l’intérêt et la versatilité du procédé sol-gel pour la préparation de matériaux biologiquement actifs a été démontrée, et permet d’envisager de nombreuses applications dans le domaine de la santé<br>We developed hybrid hydrogels for mesenchymal stem cells embedding, which could be of interest for cartilage repair. Our strategy is based on the functionalization of bioactive molecules and biopolymer with triethoxysilane moieties to prepare hydrogels by a sol-gel process. This bio-orthogonal process take place in water, at physiological pH and 37 °C. First, we searched for a biocompatible catalysis method and we studied the reaction parameters influencing the gelation time. Then, collagen-like peptides of various sizes have been synthesised and silylated to prepare biomimetic hydrogels. The composition of these hydrogels has been improved to reach the best cellular viability and chondrocyte differentiation after embedding. The resulting mechanical properties were also studied. Finally, theses hydrogels have been 3D-printed by extrusion and new compositions have been developed to reach a better accuracy. Through the numerous hydrogel compositions we developed, the potential and versatility of sol-gel process for hydrogel preparation was demonstrated, paving the way to many applications in health sciences
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Gačanin, Jasmina [Verfasser]. "Design and Synthesis of Multifunctional Hybrid Hydrogels for Medicinal Applications / Jasmina Gačanin." Ulm : Universität Ulm, 2021. http://d-nb.info/123552843X/34.
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Le, Gulluche Anne-Charlotte. "Hybrid hydrogels as model nanocomposites : reinforcement mechanisms by analogy with filled rubbers." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1107/document.
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Les hydrogels sont des matériaux intrinsèquement mous, fragiles et élastiques, majoritairement composes d'eau. Leur capacité unique à interagir avec leur environnement se traduit par une grande variation de leur volume initial et en font l'objet d'applications variées dans de nombreux domaines tels que le secteur biomédical, l'industrie agro-alimentaire et cosmétique. Plus récemment, des hydrogels ont été développés pour des secteurs de pointe comme la robotique ou l'ingénierie tissulaire, permettant d'élargir le spectre d'utilisation de la matière molle en tant que matériau structurel. De ce fait, la conception d'hydrogels mécaniquement performants représente un enjeu majeur au développement futur de ces applications.L'élaboration de matériaux nanocomposites incorporant des nanocharges à un réseau organique réticule de façon covalente s'est avérée une stratégie de renfort efficace. Le renforcement dépend alors des interactions existantes entre le polymère et les charges ainsi que de l'état de dispersion des nanoparticules au sein du réseau. Des hydrogels hybrides, à base de poly(N-alkylacrylamides) et de nanoparticules de silice ont ainsi été mis au point, démontrant une amélioration significative des propriétés mécaniques (déformation à la rupture, capacités d'autoréparation). Ce phénomène est attribué à l'adsorption réversible du polymère à la surface des nanoparticules. Si les propriétés viscoélastiques de ces composés ont été largement étudiées, peu de travaux ont été effectués sur la caractérisation et la quantification des interactions à l'interface solide/liquide. De même, le comportement au delà du domaine linéaire ne reste que peu étudié à ce jour. La première partie de ces travaux a été dédiée à la synthèse de chaines linéaires de poly- (acrylamide) (PAAm) et poly(N,N-dimethylacrylamide) (PDMA) ainsi qu'à l'étude de leurs capacités d'adsorption sur la silice tout en contrôlant la chimie de surface des nanoparticules. Cela a permis de mettre en évidence le peu d'affinité du PAAm envers la surface de silice, justifiant ainsi son emploi en tant que monomère « inerte ». En second lieu, il s'est agi de moduler les interactions entre le polymère et la silice au sein des hydrogels hybrides en substituant le polymère interagissant avec l'adsorbat (PDMA) par un polymère peu apte à s'adsorber sur la silice (PAAm). La structure de ces composés ainsi que leur comportement mécanique ont été explorés avec un intérêt marqué pour le domaine non linéaire. Le rôle de l'adsorption dans le renfort mécanique a ainsi été confirmé et plus précisément l'importance des groupements silanols à la surface de la silice. La contribution de l'état d'agrégation des nanoparticules sur la structure et les propriétés mécaniques ont ensuite été étudiés. Le comportement non-linéaire aux grandes déformations des hydrogels synthétisés a notamment été investigué par des expériences de rhéologie aux grandes amplitude de cisaillement (LAOS), permettant une caractérisation plus poussée des mécanismes de renfort, par analogie avec les élastomères chargés<br>Hydrogels are soft and elastic solid materials mainly composed of water. Owing to their ability to interact with their environment through drastic volume change, hydrogels already find a wide range of applications, as superabsorbants, in pharmaceutics as drug delivery systems and more recently, as sensors and actuators, widening even more the possible use of soft materials as structural or load-bearing materials. Hence, providing gels with high mechanical performances is of major importance to meet these demanding applications. Efficient toughening can be achieved by combining inorganic and organic materials linked by physical and/or chemical interactions. In such nanocomposite materials, the reinforcement depends on the interactions between the polymer and the filler and of the dispersion state of the fillers, allowing to reach the full extent of reinforcement. Hybrid hydrogels based on poly(N-alkylacrylamide) and nanosilica demonstrating great mechanical reinforcement at large strain as well as self-healing capabilities were designed by Hourdet and Marcellan . The drastic improvement of the mechanical behavior is attributed to the reversible adsorption of the polymer onto silica surface. Viscoelastic properties of such hybrids gels have been extensively studied but few studies were carried out to understand and quantify the interactions at the solid/liquid interface. Likewise, the behavior beyond viscoelastic regime of such materials remains scarcely investigated. A first part of this study focused on the synthesis and the adsorption behavior of linear polymer chains of polyacrylamides, more precisely poly(acrylamide) (PAAm), poly(N,N-dimethylacrylamide) (PDMA) onto silica nanoparticles with controlled surface chemistry. It evidenced the non-interacting behavior of PAAm towards silica surface, justifying its choice as a non-interacting polymer. A second part dealt with the modulation of particle/polymer interactions in hybrid gels either by substituting the interacting monomer (DMA) with a non-interacting one (AAm) or by tuning the surface chemistry of the nanoparticles. Then, the study of their structure and mechanical properties was conducted with a special focus on the non-linear behavior. The role of polymer adsorption for gel reinforcement was evidenced and more specifically the importance of the silanol groups at the silica surface for PDMA/silica interactions. The contribution of the dispersion state of silica on the structure and the mechanical response of hydrogels was then addressed and the non-linear domain of the resulting hydrogels was investigated using Large Amplitude Oscillatory Shear experiments. The impact of the chosen monomer and of the dispersion state of the fillers was investigated at large strain, allowing a more precise analysis of the reinforcement mechanisms, by analogy with filled elastomers
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Mahaweero, Thanatdej. "Extraction of Heavy Metals from Aqueous Solutions using Chitosan/Montmorillonite Hybrid Hydrogels." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1365160267.
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Syed, Khurram Raza. "Electrochemical generation of hydrogen." Thesis, Brunel University, 2017. http://bura.brunel.ac.uk/handle/2438/13813.
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Global warming and the energy crisis are two of the greatest challenges on which mankind is currently focused. This has forced governments and other organisations to think how to protect the environment and how to reduce fuel costs. A variety of new and exciting technologies are being investigated to address the energy problem. Alternative energy sources such as solar power, fuel cells, wind power and tidal waves are active areas of commercial and scientific pursuit. A major area of current research is moving towards the hydrogen economy and hydrogen based energy systems. Hydrogen can be produced in many ways, most commonly by steam reforming of hydrocarbon (70% to 85% thermal efficiency) but the downside is that it releases carbon mono oxide (CO)), compared with commercial PEM electrolysers where performance has been reported to be 56 -73% at normal temperature pressure(NTP) with zero carbon emission. Electrochemical production of hydrogen has several advantages: (i) It gives pure hydrogen. (ii) It allows portability (e.g. Solar energy could be used to power the electrochemical cell). (iii) It can be produced on demand. The generation of Hydrogen via electrolysis has been the subject of many studies over the last two hundred years. However, there is still room for further work to improve both the efficiency of the process and methods of storage of the gas. The cleanest method at present is to produce hydrogen by electrolysis, and the main focus of this research is to design and develop such a green energy fuel cell for on-demand application. The aim of the work presented in this thesis was to further investigate the electrolysis method for hydrogen production. An Electrochemical fuel cell contains a minimum of two electrodes: the positively charged electrode called the anode where oxygen bubble will form, and the second negatively charged electrode called the cathode, where hydrogen bubbles will form during a chemical reaction caused by applying electrical current between these electrode. The project was initiated with the objective of finding a low cost solution for on-demand hydrogen generation. To establish a starting point, the first cell (cell-1) design was based on the work of Stephen Barrie Chambers (see chapter 3) to check the performance levels. The fabrication of the cell-1 design resulted in a mixture of hydrogen and oxygen in the same chamber, which means the cell-1 design, has a possible fire and explosion hazard. The device also has the drawback of lower performance of hydrogen production; columbic efficiency is between 40% to 46% at 1 amp to 3 amp current in 30% KOH alkaline solution. However, the advantage of reproducing Stephen’s innovation is that it allowed a quick and deep understanding of hydrogen generation. This thesis presents recent work on the fabrication of low cost electrolysis cells containing continuous flow alkaline (KOH, up to 30%) electrolyte using low cost electrodes (stainless steel 316) and membranes based on ultrahigh molecular weight polyethylene (UHMW PE) to produce hydrogen without the hazard of fire and explosion. In this research an On-Demand Hydrogen Generation cell-3 achieved a 95% hydrogen generation coulombic efficiency, which is about 49% efficiency improvement as compared to the stainless steel electrode, and was 22% better than the nano structured electrode. The typical cell voltage is 2.5 V at current flow ranging from 30 to 120 mA cm-2 in 30% KOH electrolyte. The achievement here of such high efficiencies paves the way for more research in the areas of space management, electrode surface structure and flow control (based on the application requirement). This invention can be used for aeronautic, marine and automotive application as well as in many other areas.
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Diaconu, Cristian V. "Hybrid density functional studies of hydrogen storage related molecular systems /." View online version; access limited to Brown University users, 2005. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3174594.
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Dhanasingh, Anandhan [Verfasser]. "sP (EO-stat-PO) - glycosaminoglycans (GAGs) hybrid-hydrogels for medical applications / Anandhan Dhanasingh." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2012. http://d-nb.info/1018709886/34.
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Shin, Hye Ji. "Micropatterned carbon nanotube embedded cell-laden gelatin methacrylate hybrid hydrogels for cardiac tissue." Thesis, Boston University, 2013. https://hdl.handle.net/2144/12222.
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Thesis (M.A.)--Boston University<br>Cardiovascular disease is the leading cause of mortality in the world. Cardiac tissue engineering promises to replace damaged organs and tissues with biologically compatible engineered substitutes. Micro- and nanotechnologies have proven to be effective to address current challenges in tissue engineering and regenerative medicine. A principle approach in tissue engineering is the integration of innovative biomaterials with micro- and nanofabrication techniques to generate constructs that recapitulate the in vivo cellular microenvironments.
In this study, highly organized three-dimensional (3D) cardiac tissue constructs in carbon nanotube (CNT) embedded gelatin methacrylate (GelMA) were generated using micropatterning techniques. Neonatal rat ventricular cardiomyocytes (NRVMs) and cardiac fibroblasts (CFs) were used as the primary cardiac cell types to be encapsulated in the three-dimensional tissue constructs. The resulting cardiac constructs in CNT-GelMA
hybrid hydrogels from various methods showed enhanced cell viability and higher spontaneous synchronous beating rates, compared to those in pristine GelMA hydrogels.
Further studies are necessary to determine the efficacy of micropatterned 3D cardiac tissue constructs in CNT-GelMA hybrid hydrogels for in vitro studies and therapeutic purposes.
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Clauzier, Stéphanie. "Etude de la solubilité de l’hydrogène dans des liquides confinés." Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10285/document.
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L’adsorption des gaz dans les solides micro/mésoporeux et la solubilisation des gazdans les liquides sont des phénomènes physiques très bien connus. En revanche, lasolubilisation des gaz dans un liquide confiné à l’intérieur d’un solide (système hybride) estun domaine très peu étudié, malgré des applications importantes, notamment dans l’extractiondu pétrole, les ciments ou encore les réacteurs catalytiques triphasiques. Nous avons montréexpérimentalement que la solubilité du CO2 et H2 augmente quand la taille de pores du solideest de l’ordre du nanomètre. Un des objectifs de cette thèse était d’optimiser le couple solidesolvant(système hybride) et les conditions de température et de pression pour augmenter lestockage de H2 pour les applications de stockages. Dans le système Aérogel/éthanol à 50 barset 0°C, la solubilité de H2 est 8,5 fois supérieure à la solubilité mesurée dans le liquide seul,représentant une masse de 6,2g d’hydrogène stocké par kg de solide. Le second objectif étaitde comprendre les paramètres clefs de ce phénomène apparent de « sursolubilité » dans lessystèmes hybrides. En comparant différents solides poreux (zeolithes, MOF, MCM, silice),nous avons montré le rôle majeur des propriétés d’interfaces. Les phénomènes desolubilisation ont été modélisés à l’échelle moléculaire par GCMC et validéesexpérimentalement. Il apparait que le mécanisme de sursolubilisation provient d’unestructuration en couche des molécules de solvants en interactions avec les parois dumésopore<br>The adsorption of gases in micro/mesoporous materials and solubility of gases inliquids are physical phenomena well known. On the other hand, solubility of gases in liquidsconfined inside a solid (hybrid system) has not been entensively studied, despite the importantapplications such systems can have in the areas of oil extraction, cement and triphasiccatalytic reactors. We have shown experimentally that the solubility of CO2 and H2 increaseswhen the size of the pores of the solid is in the nanometer range. One of the objectives of thisthesis was to optimize the couple a solid and a solvent into a hybrid system and the conditionsin which to increase the H2 storage capacity. In an aerogel/ethanol hydrid system at 50 barand 0 ° C, the solubility of H2 is 8.5 times greater than the solubility measured in the singleliquid, representing a mass of 6.2 g of hydrogen stored per kg of solid. The second objectivewas to understand this apparent phenomenon of oversolubility and the key parameters in thehybrid systems. By comparing different porous solids (zeolites, MOFs, MCM-41 and silica),we have shown the major role of the properties of interfaces. The phenomena of solubilsationwas modelled by GCMC and experimentally validated. It appears that the mechanism ofoversolubilisation comes from structuring the solvent molecules in interactions with the wallsof the mesopore layered
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Ciftci, Saït. "Use of functionalized hydrogels for rapid re-epithelialization of hybrid implants in tissue engineering." Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAE023.
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Dans le cadre du développement d’un larynx artificiel, les expérimentations sur l’animal et les essais cliniques ont mis en évidence un défaut de ré-épithélialisation de la face endoluminale de la prothèse. Cet épithélium respiratoire est absolument nécessaire pour obtenir un dispositif implantable totalement intégré dans le corps mais également pour la fonctionnalité d’un tel implant. Dans ce travail nous avons développé de nouveaux films d’hydrogels de collagène et d’acide hyaluronique interpénétrés et réticulés pour assurer une repousse épithéliale rapide. Ces films d’hydrogels optimisés ont une résistance suffisante à l’hydrolyse pour limiter leur dégradation précoce une fois implantés. Ils ont été fonctionnalisés par des facteurs de croissance et de différenciation cellulaire libérés de façon progressive avec un résultat objectivé sur la prolifération cellulaire. L’encapsulation de cellules immunitaire et l’utilisation de cytokines dans ces gels permettent également de moduler la réponse inflammatoire vers un processus de cicatrisation plutôt que de rejet<br>As part of the development of an artificial larynx, in vivo experiments and clinical trials have revealed a defect in re-epithelialization of the endoluminal side of the prosthesis. This respiratory epithelium is absolutely necessary to obtain an implantable device fully integrated into the body but also for the functionality of such an implant. In this work we have developed patches of interpenetrated and reticulated hydrogels based on collagen and hyaluronic acid to ensure rapid epithelial regrowth. These optimized hydrogel patches have sufficient resistance to hydrolysis to limit their early degradation once implanted. They have been functionalized by growth and cell differentiation factors that are released gradually with an objectified result on cell proliferation. Encapsulation of immune cells and the use of cytokines in these gels also modulate the inflammatory response towards a healing process rather than rejection
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Rodriguez, Ramon, and Pamplona David Sanchéz. "DYNAMIC MODELING OF HYBRID PV/THERMAL SOLAR SYSTEM FOR HYDROGEN PRODUCTION." Thesis, University of Gävle, University of Gävle, Department of Technology and Built Environment, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-3580.
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Jeličić, Aleksandra, Alwin Friedrich, Katarina Jeremić, Gerd Siekmeyer, and Andreas Taubert. "Polymer hydrogel/polybutadiene/iron oxide nanoparticle hybrid actuators for the characterization of NiTi implants." Universität Potsdam, 2009. http://opus.kobv.de/ubp/volltexte/2010/4858/.
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One of the main issues with the use of nickel titanium alloy (NiTi) implants in cardiovascular implants (stents) is that these devices must be of very high quality in order to avoid subsequent operations due to failing stents. For small stents with diameters below ca. 2 mm, however, stent characterization is not straightforward. One of the main problems is that there are virtually no methods to characterize the interior of the NiTi tubes used for fabrication of these tiny stents. The current paper reports on a robust hybrid actuator for the characterization of NiTi tubes prior to stent fabrication. The method is based on a polymer/hydrogel/magnetic nanoparticle hybrid material and allows for the determination of the inner diameter at virtually all places in the raw NiTi tubes. Knowledge of the inner structure of the raw NiTi tubes is crucial to avoid regions that are not hollow or regions that are likely to fail due to defects inside the raw tube. The actuator enables close contact of a magnetic polymer film with the inner NiTi tube surface. The magnetic signal can be detected from outside and be used for a direct mapping of the tube interior. As a result, it is possible to detect critical regions prior to expensive and slow stent fabrication processes.
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Habib, MD Ahasan. "Designing Bio-Ink for Extrusion Based Bio-Printing Process." Diss., North Dakota State University, 2019. https://hdl.handle.net/10365/32045.
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Tissue regeneration using in-vitro scaffold becomes a vital mean to mimic the in-vivo counterpart due to the insufficiency of animal models to predict the applicability of drug and other physiological behavior. Three-dimensional (3D) bio-printing is an emerging technology to reproduce living tissue through controlled allocation of biomaterial and cell. Due to its bio-compatibility, natural hydrogels are commonly considered as the scaffold material in bio-printing process. However, repeatable scaffold structure with good printability and shape fidelity is a challenge with hydrogel material due to weak bonding in polymer chain. Additionally, there are intrinsic limitations for bio-printing of hydrogels due to limited cell proliferation and colonization while cells are immobilized within hydrogels and don’t spread, stretch and migrate to generate new tissue. The goal of this research is to develop a bio-ink suitable for extrusion-based bio-printing process to construct 3D scaffold. In this research, a novel hybrid hydrogel, is designed and systematic quantitative characterization are conducted to validate its printability, shape fidelity and cell viability. The outcomes are measured and quantified which demonstrate the favorable printability and shape fidelity of our proposed material. The research focuses on factors associated with pre-printing, printing and post-printing behavior of bio-ink and their biology. With the proposed hybrid hydrogel, 2 cm tall acellular 3D scaffold is fabricated with proper shape fidelity. Cell viability of the proposed material are tested with multiple cell lines i.e. BxPC3, prostate stem cancer cell, HEK 293, and Porc1 cell and about 90% viability after 15-day incubation have been achieved. The designed hybrid hydrogel demonstrate excellent behavior as bio-ink for bio-printing process which can reproduce scaffold with proper printability, shape fidelity and higher cell survivability. Additionally, the outlined characterization techniques proposed here open-up a novel avenue for quantifiable bio-ink assessment framework in lieu of their qualitative evaluation.
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Zamboulis, Alexandra. "Silices hybrides pour l'organocatalyse asymétrique." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2010. http://www.theses.fr/2010ENCM0004.
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L'organocatalyse asymétrique est un domaine en plein développement. L'immobilisation de ce type de catalyseurs pourrait présenter de multiples avantages. Ces travaux de thèse s'intéressent à la préparation de silices hybrides organiques/inorganiques par voie sol-gel et aux applications de ces matériaux en organocatalyse asymétrique. La première partie du manuscrit est consacrée à une présentation bibliographique du sujet. Dans la deuxième partie, l'utilisation de la L-proline comme modèle est décrite. Des matériaux contenant un fragment L-proline ont été préparés et leurs performances catalytiques évaluées pour une réaction d'aldolisation asymétrique. Les processus à l'origine des propriétés catalytiques modérées de ces catalyseurs supportés sont discutés. La troisième partie porte sur le catalyseur de Takemoto, organocatalyseur bifonctionnel contenant un groupement donneur de liaisons hydrogène et une fonction amine tertiaire. Les différentes stratégies envisagées pour préparer des dérivés silylés de ce catalyseur sont exposées. Enfin, la nanostructuration de silsesquioxanes par le biais de liaisons hydrogène entre fonctions thiourée est présentée<br>Asymmetric organocatalysis is a blossoming area of research. Immobilisation of this kind of catalysts could present numerous advantages. This thesis deals with the sol-gel synthesis of organic/inorganic hybrid silicas and their applications in asymmetric organocatalysis. The first part of this work is dedicated to a bibliographic presentation of this area of research. In the second part, the use of L-proline as a model is described. Hybrid materials containing a L-proline component were prepared and their catalytic performances were evaluated in an asymmetric aldolisation reaction. The processes accounting for the moderate performances of these materials are discussed. The third part relates the synthetic strategies used to prepare silylated derivatives of the Takemoto catalyst, a bifunctional catalyst containig a H-bond donnor and a tertiary amine. Finally the nanostructuring of bridged silsesquioxanes through H-bonding interactions between thiourea cross-linkers is presented
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Sdanghi, Giuseppe. "Développement d’un compresseur hybride d’hydrogène : électrochimique à basse pression/adsorption à haute pression." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0145.
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La preuve de concept d’un compresseur non-mécanique d’hydrogène a été réalisée dans le cadre de ce travail de thèse. Le système étudié est hybride puisqu’il est constitué de (i) une première étape de compression électrochimique, qui comprime l’hydrogène de 1 bar jusqu’à 40-80 bar et ; (ii) une deuxième étape de compression par adsorption-désorption qui complète la compression jusqu’à 700 bar. Des modèles numériques ont été développés pour vérifier la faisabilité d’un tel système, et leur validité a été prouvée par les données expérimentales obtenues avec les prototypes réalisés pour chacune des deux étapes de compression. Concernant l’étape de compression électrochimique, un profil de densité de courant le long du compresseur électrochimique a été observé à l’aide d’une cellule segmentée, et le modèle pseudo-2D développé a permis de prouver que la stabilité de la densité de courant dépend fortement de la teneur locale en eau de la membrane. En effet, il a été observé une diminution de la densité de courant de 0.75 à 0.65 A/cm2 entre l’entrée et la sortie du compartiment basse pression. Cette variation correspond à une diminution du taux d’humidité dans le flux d’hydrogène, de 90 à 55%, le long des canaux de distribution des réactifs côté anodique (à 0.66 A/cm2 x 0.36 V et à 333 K). Concernant l’étape de compression par adsorption-désorption, le modèle modifié de Dubinin-Astakhov (MDA) a été mis en œuvre pour décrire l’adsorption d’hydrogène sur des charbons actifs en fonction des conditions de température et de pression. Cette loi, associée aux bilans de masse et d’énergie ont permis d’étudier la faisabilité d’un tel compresseur. Les résultats de modélisation ont été validés par comparaison avec des données expérimentales obtenues grâce à un prototype de 0.5 L, conçu et construit pour ce travail de thèse, et contenant 0.135 kg de charbon actif MSC-30 (Kansai, Japon). Lorsque le réservoir est rempli d’hydrogène à 80 bar et 77K, son réchauffement jusqu’ à 315 K permet d’obtenir des débits de 30 NL/h à 700 bar. Le compresseur hybride proposé pourrait être une alternative valable aux compresseurs mécaniques placés dans des installations décentralisées telles que les stations-service d’hydrogène de faible ou moyenne capacité<br>The proof of concept of a non-mechanical hydrogen compressor has been carried out in the present study. It is a hybrid compressor since it consists of: (i) a first electrochemical compression step, which compresses hydrogen from 1 bar up to 40-80 bar and; (ii) a second compression step based on the thermally-driven cyclic adsorption-desorption which allows compressing hydrogen up to 700 bar. Numerical models have been developed to verify the feasibility of such a system, and their validity has been proved by the experimental data obtained with the prototypes built for each of the two compression stages. Concerning the electrochemical compressor, a current density distribution along the electrochemical was observed using a segmented cell, and the developed pseudo-2D model proved that the stability of the current density strictly depends on the local water content of the membrane. Indeed, the current density was found to decrease from 0.75 A/cm2 to 0.65 A/cm2 between the first and the last segment of the compressor, which corresponds to a decrease of the relative humidity in the inlet hydrogen flow from 90% to 55% along the gas channels at the anode side (at 0.66 A/cm2 x 0.36 V and 333 K). Concerning the adsorption-desorption compressor, the Modified Dubinin-Astakhov model (MDA) was implemented to describe hydrogen adsorption on activated carbons as a function of the temperature and the pressure. It was used along with the mass and the energy balance equations to study the feasibility of such a compressor. The results from the numerical simulation were validated with the experimental data, which were obtained using a prototype of 0.5 L, designed and built for the present study, and containing 0.135 kg of the activated carbon MSC-30 (Kansai, Japan). 30 NL/h of high-pressure hydrogen at 700 bar were obtained when introducing hydrogen at 80 bar into the compressor, previously cooled to 77 K, and when heating it up to 315 K. The proposed hybrid hydrogen compressor could be a valid alternative to traditional mechanical compressors, and it could be used in small and decentralized facilities using hydrogen as a fuel, e.g. a hydrogen refuelling station
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Majewski, Alexander [Verfasser], and Axel [Akademischer Betreuer] Müller. "Dual-Responsive Polymer and Hybrid Systems: Applications for Gene Delivery and Hydrogels / Alexander Majewski. Betreuer: Axel Müller." Bayreuth : Universität Bayreuth, 2013. http://d-nb.info/1059352680/34.
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Gazey, Ross Neville. "Sizing hybrid green hydrogen energy generation and storage systems (HGHES) to enable an increase in renewable penetration for stabilising the grid." Thesis, Robert Gordon University, 2014. http://hdl.handle.net/10059/947.
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A problem that has become apparently growing in the deployment of renewable energy systems is the power grids inability to accept the forecasted growth in renewable energy generation integration. To support forecasted growth in renewable generation integration, it is now recognised that Energy Storage Technologies (EST) must be utilised. Recent advances in Hydrogen Energy Storage Technologies (HEST) have unlocked their potential for use with constrained renewable generation. HEST combines Hydrogen production, storage and end use technologies with renewable generation in either a directly connected configuration, or indirectly via existing power networks. A levelised cost (LC) model has been developed within this thesis to identify the financial competitiveness of the different HEST application scenarios when used with grid constrained renewable energy. Five HEST scenarios have been investigated to demonstrate the most financially competitive configuration and the benefit that the by-product oxygen from renewable electrolysis can have on financial competitiveness. Furthermore, to address the lack in commercial software tools available to size an energy system incorporating HEST with limited data, a deterministic modelling approach has been developed to enable the initial automatic sizing of a hybrid renewable hydrogen energy system (HRHES) for a specified consumer demand. Within this approach, a worst-case scenario from the financial competitiveness analysis has been used to demonstrate that initial sizing of a HRHES can be achieved with only two input data, namely – the available renewable resource and the load profile. The effect of the electrolyser thermal transients at start-up on the overall quantity of hydrogen produced (and accordingly the energy stored), when operated in conjunction with an intermittent renewable generation source, has also been modelled. Finally, a mass-transfer simulation model has been developed to investigate the suitability of constrained renewable generation in creating hydrogen for a hydrogen refuelling station.
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Mhiri, Sirine. "Elaboration et caractérisation d’hydrogels à base de monomères biosourcés par la réaction de Diels-Alder." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSES024/document.
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Les travaux de recherche réalisés, dans le cadre de la préparation de cette thèse ont pour objectif l’élaboration de nouveaux réseaux thermoréversibles biodégradables à base de polyglycolide (PGA) et d’hydrogels à base de polylactide (PLA) modifiés chimiquement au moyen du noyau furanique et du cycle maléimide. La réticulation du PGA, en suivant deux stratégies, en vue d’élaborer des réseaux thermoréversibles et biodégradables via la réaction de Diels-Alder a fait l’objet de la première partie de ce travail. Le but était entre autres de valoriser le PGA en conduisant à des structures réticulées avec des propriétés mécaniques requises tout en améliorant ses propriétés de stabilité. Des réseaux hybrides de PLA/PEG et PLA/PHEMA ont été ensuite synthétisés en phase fondu en adoptant la réaction de Diels-Alder comme mécanisme de réticulation. Une fois obtenus, leur mise au contact de l’eau conduit à la formation d’hydrogels. Les analyses structurales menées par RMN ont permis de confirmer la formation des structures attendues. La thermoréversibilité des réseaux obtenus a été montrée par des analyses rhéologiques. La morphologie des gels avant et après gonflement a été analysée par Microscopie Electronique à balayage. La dégradabilité des réseaux préparés a été examinée selon deux modes : hydrolytique et par les microorganismes en milieu aérobie<br>The research conducted for the preparation of this thesis aims to develop new thermoreversible and biodegradable polyglycolic-acid (PGA) based networks and polylactic-acid (PLA) based hydrogels, from polymers chemically modified by means of furanic, and maleimide cycle. The cross-linking of PGA to develop thermoreversible and biodegradable networks via the Diels-Alder reaction has been done by following two strategies and was the first part of this work. The aim was, among other things, to enhance the PGA by leading to reticulated structures with required mechanical properties while improving its stability properties. Hybrid networks of PLA / PEG and PLA / PHEMA were then synthesized in the melt by adopting the Diels-Alder reaction as a crosslinking mechanism. Once obtained, their contact with water leads to the formation of hydrogels. NMR structural analyzes confirmed the formation of expected structures. The thermoreversibility of the obtained networks has been shown by rheological analyzes. The morphology of the gels before and after swelling was analyzed by Scanning Electron Microscopy. The degradability of prepared networks was examined in two modes: hydrolytic and aerobic by microorganisms
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Amoura, Makhlouf. "Elaboration de nouvelles matrices minérales pour l’encapsulation cellulaire : approche colloïdale." Paris 6, 2008. http://www.theses.fr/2008PA066104.
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Le travail décrit dans ce mémoire de thèse vise à étendre la technique d’encapsulation cellulaire par voie sol-gel à des matrices d’oxydes métalliques. L’utilisation de l’approche colloïdale pour l’élaboration de telles matrices nous a permis d’élaborer des gels d’oxyhydroxydes d’aluminium, de fer et de zirconium à des pH proches de la neutralité et à une température ambiante, conditions favorables à l’incorporation de bactéries Escherichia coli. Ces matériaux on été caractérisés de manière approfondie à l’aide de différentes techniques (analyse élémentaire, spectroscopie IR, diffraction des rayons X, zétamétrie, microscopies électroniques par balayage et par transmission, analyse thermogravimétrique et sorption de d’azote). Ce procédé de synthèse a été validé par une étude concluante de la viabilité des bactéries encapsulées au sein de ces matrices. Par ailleurs, des matrices biohybrides mettant en jeu des additifs bio-organiques, l’alginate et la glycine bétaïne, ont été réalisées afin d’améliorer la viabilité des bactéries en minimisant les stress mécaniques et chimiques liés à l’encapsulation. Enfin, des résultats préliminaires ont permis d’envisager l’exploitation des propriétés magnétiques des gels de ferrihydrite comme modèles dans le domaine de la géomicrobiologie et pour réaliser des biocapteurs magnétiques.
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Appressi, Lorenzo. "Biogas and bio-hydrogen: production and uses. A review." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9071/.
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The first part of this essay aims at investigating the already available and promising technologies for the biogas and bio-hydrogen production from anaerobic digestion of different organic substrates. One strives to show all the peculiarities of this complicate process, such as continuity, number of stages, moisture, biomass preservation and rate of feeding. The main outcome of this part is the awareness of the huge amount of reactor configurations, each of which suitable for a few types of substrate and circumstance. Among the most remarkable results, one may consider first of all the wet continuous stirred tank reactors (CSTR), right to face the high waste production rate in urbanised and industrialised areas. Then, there is the up-flow anaerobic sludge blanket reactor (UASB), aimed at the biomass preservation in case of highly heterogeneous feedstock, which can also be treated in a wise co-digestion scheme. On the other hand, smaller and scattered rural realities can be served by either wet low-rate digesters for homogeneous agricultural by-products (e.g. fixed-dome) or the cheap dry batch reactors for lignocellulose waste and energy crops (e.g. hybrid batch-UASB).
The biological and technical aspects raised during the first chapters are later supported with bibliographic research on the important and multifarious large-scale applications the products of the anaerobic digestion may have. After the upgrading techniques, particular care was devoted to their importance as biofuels, highlighting a further and more flexible solution consisting in the reforming to syngas. Then, one shows the electricity generation and the associated heat conversion, stressing on the high potential of fuel cells (FC) as electricity converters. Last but not least, both the use as vehicle fuel and the injection into the gas pipes are considered as promising applications. The consideration of the still important issues of the bio-hydrogen management (e.g. storage and delivery) may lead to the conclusion that it would be far more challenging to implement than bio-methane, which can potentially “inherit” the assets of the similar fossil natural gas.
Thanks to the gathered knowledge, one devotes a chapter to the energetic and financial study of a hybrid power system supplied by biogas and made of different pieces of equipment (natural gas thermocatalitic unit, molten carbonate fuel cell and combined-cycle gas turbine structure). A parallel analysis on a bio-methane-fed CCGT system is carried out in order to compare the two solutions. Both studies show that the apparent inconvenience of the hybrid system actually emphasises the importance of extending the computations to a broader reality, i.e. the upstream processes for the biofuel production and the environmental/social drawbacks due to fossil-derived emissions. Thanks to this “boundary widening”, one can realise the hidden benefits of the hybrid over the CCGT system.
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Zang, Dejin. "Hybrid polyoxometalate@M NP photosensitized systems for the generation of photocurrent or for the generation of dihydrogen." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAF032.
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Différents systèmes polyoxométallates@M-colorants ont été réalisés dans cette thèse pour électrochimique dégagement d'hydrogène catalytique et génération photocourant.• Des films hybrides, basés sur des interactions électrostatiques entre une porphyrine tetracationique et des nanoparticules stabilisées par des POMs du type POM@Pt sur ITO, ont été formés par la méthode dite couche par couche et ont été utilisés pour la génération de H2 ou de photocourant. • Pour améliorer le transfert de charge entre les nanoparticules POM@M et le substrat, la réduction de l'oxyde de graphène a été réalisée pour former des systèmes hybrides rGO/POM@Pt. Le dégagement d'hydrogène a été mesuré.• Les copolymères polycationiques bis-porphyrine ont également été obtenus par électropolymérisation avec des espaceurs bis-pyridinium. Par réaction de métathèse, l’incorporation avec divers POM de type Keggin ou des nanoparticules du type POM@Ag ont ensuite été realise. Leurs performances photovoltaïques ont ensuite été étudiées.• Enfin des films hybrides PEDOT dopés avec des nanoparticules du type POM@M ont également été fabriqués. Les performances photovoltaïques ont été examinés montrant une forte amélioration sous illumination dans le domaine du visible. L’ensemble de ces matériaux hybrides ont montré des propriétés intéressantes pour des applications photovoltaïques et la conversion d'énergie<br>Polyoxometalates@M NPs-dyes molecular hybrid systems were realized in this thesis for electrochemical catalytic hydrogen evolution and photocurrent generation. • First, hybrid films, based on electrostatic interactions between the tetracationic porphyrin and POMs@Pt NPs composites on ITO slides, were formed by the so called Layer-by-Layer method for HER and photocurrent generation.• To improve the charge transfer between POMs@M NPs and the substrate, reduced graphene oxide was introduced to form rGO/POMs@Pt NPs hybrid systems. Hydrogen evolution was measured after dropping this composites onto the surface of glassy carbon electrodes.• Polycationic bis-porphyrin copolymers have been also obtained by an electropolymerization leading to the formation of new bis-porphyrin copolymers with pyridinium as spacers. Incorporation with various Keggin type POMs or POMs@Ag was then achieved, their photovoltaic performances were also studied.• POMs@M NPs doped PEDOT hybrids films have been also fabricated. The photovoltaic performances has been examined showing particularly strong enhancement under visible light. In conclusion, these polyoxometalates based hybrids materials have shown interesting properties for photovoltaic application and energy conversion
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Moussa, Georges. "Nanoconfinement de l’ammoniaborane dans du carbone ou nitrure de bore mésoporeux : matériaux hybrides pour le stockage chimique et la génération d’hydrogène." Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20033/document.
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La thèse a concerné l'élaboration de matériau composite NH3BH3@BN pour le stockage chimique de l'hydrogène et a été divisée en 3 axes majeurs : la synthèse de NH3BH3 mais aussi celle d'un dérivé, l'hydrazine borane N2H4BH3 (publié dans /Phys.Chem.Chem.Phys/.: 2012, 14, 1768; "Hydrazine borane: synthesis,characterization, and application prospects in chemical hydrogen storage"), optimisation du processus de confinement en utilisant un matériau hôte commercial et abondant comme le charbon actif (NORIT SX1 700 m^2 /g) (publié dans /Int. J. Hydrogen Energy/:2012, 37, 13437 ; "Room-temperature hydrogen release from activated carbon-confined ammonia borane"), synthèse de nanostructures à base de BN, sous forme de nanocapsules creuses et de répliques de poreux à base de charbon actif pour le nanoconfinement de NH3BH3. (à paraitre dans /J. Mater.//Chem/.)<br>The thesis concerned the development of composite NH3BH3@BN for chemical hydrogen storage material and it has been divided into three major axes: the synthesis of NH3BH3 but also a derivative, hydrazine borane N2H4BH3 (published in / Phys Chem Chem Phys /: 2012, 14, 1768 "Hydrazine borane: synthesis, characterization, and application of prospects in chemical hydrogen storage"....), optimization of the confinement process using a commercial and abundant host material such as activated carbon (Norit SX1 700 m^2/g) (published / Int J. Hydrogen Energy /: 2012, 37, 13437, "Room-temperature hydrogen release from activated carbon-ammonia borane confined.") synthesis BN-based nanostructures in the form of hollow nanocapsules and replica of porous activated carbon for nanoconfinement of NH3BH3. (to be published in / J. Mater.Chem /.)
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Novosád, Jan. "Alternativní pohon automobilů." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228852.
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In this work is processed a survey of perspective alternative drives in motor vehicles. There are main characteristic for each mentioned drive, their advantages and disadvantages and problems associated with their use in vehicles. The work is aimed at gas engines, electro mobiles, hybrid drives and hydrogen, therefore the most likely drives the future.
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Vaca, Flores Claudia Cecilia. "Substituts osseux hybrides (polymère / bio céramiques) à libération prolongée d'antibiotiques pour le traitement des infections osseuses." Thesis, Lille 2, 2015. http://www.theses.fr/2015LIL2S072.
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A ce jour l’os est le tissu le plus greffé au monde et les défets osseux suite à une ostéoporose, cancer et fractures restent problématiques avec un risque d’infections élevé. L’administration d’antibiotiques par voie systémique n'est pas satisfaisante car leur diffusion dans l'os est très faible, une administration locale est donc nécessaire. La stratégie de cette thèse est de développer deux substituts hybrides (hydroxyapatite/hydrogel), l'un massif, l'autre injectable, pour l'administration d'une association d'antibiotiques (ciprofloxacine/gentamicine). Un double système à libération sera ainsi développé pour traiter au long terme l'infection, l'un permettra une libération rapide (via la diffusion dans l'hydrogel), l'autre permettra une diffusion lente (via des microparticules). La première partie a permis de développer des microparticules de PLGA chargées de gentamicine (GM) par la technique de double émulsion par évaporation du solvant. La méthode de préparation des microparticules a été optimisée pour obtenir des microparticules de 50 à 80 µm, compatible avec la macroporosité de l'hydroxyapatite (HA) et une libération prolongée pendant 25-30 jours. Ainsi le temps de sonification de la première émulsion a été fixé à 2 minutes pour obtenir une efficacité d'encapsulation maximale et la vitesse de rotation de la seconde émulsion fixée à 700 rpm pour obtenir des microparticules d'environ 60 µm. Les microparticules ont été analysées par DSC, ATG et MEB. L'activité antibactérienne des microparticules chargées de GM a été démontrée sur le S. aureus (CIP224).La seconde partie a permis de développer un scaffold où l'hydrogel de chitosan (CHT) se formera in situ dans la macroporosité d'une pièce tridmensionnelle en HA. Cet hydrogel a été obtenu par voie chimique avec un agent réticulant (genipine) pour permettre une injection et une gélification relativement lente. Le suivi de la formation de l'hydrogel de CHT (2%-wt) par spectrophotométrie et rhéologie a permis d'optimiser le temps (24 heures) et la température (40°C) de gélification ainsi que la concentration de génipine (0.05%-wt). L'étude de la cinétique de libération de la ciprofloxacine (CFX) incorporée dans l'hydrogel lors de la formulation (0.1; 0.5 et 1%) a montré une libération rapide (<5 heures) en flux dynamique (30 ml/min). L'ajout de cyclodextrine(CD) dans la formulation pour ralentir la diffusion de la CFX n'a pas montré d'amélioration, elle est même responsable d'un ralentissement de la gélification par inclusion de la génipine dans la CD. Finalement l'hydrogel a été incorporé dans la macroporosité de l'HA avant la gélification; les études biologiques ont montré sa cytocompatibilité et une activité antibactérienne de 24 heures sur E. coli.La dernière partie a permis de développer un hydrogel injectable où les particules d'HA (90 µm) ont été incorporées dans l'hydrogel pendant la préparation. Cet hydrogel est obtenu par voie physique avec le polymère de cyclodextrine (PCD) pour une gélification rapide (<10 sec.) évitant la sédimentation de l'HA. Une étude plus approfondie a permis de montrer qu'une proportion d’au moins de 3% de CHT et d’au moins 3% de PCD était nécessaire pour la formation de l'hydrogel. Les études du gonflement et des propriétés rhéologiques ont montré l’impact du ratio PCD/CHT, de la forme soluble et insoluble du PCD et l'ajout d'HA sur la formation de l'hydrogel. Après lyophilisation, l'éponge a été hydratée dans une solution de CFX (2 mg/ml); les études biologiques n'ont pas montré de cytotoxicité et l'évaluation microbiologique a montré une activité prolongée (72 heures) sur E. coli [...]<br>Bone is the most transplanted tissue in the world and bone defects after osteoporosis, cancer and fractures remain problematic with a high level of infections. Systemic drug delivery is not efficient due to a low migration of drug into the bone, a local administration is necessary. The strategy of this thesis is to develop two hybrid substitutes (hydroxyapatite / hydrogel), the first one could be injectable and the other one could be directly implanted for the release of a combination of antibiotics (ciprofloxacin / gentamicin). A dual release system will be developed to treat long term infection with a rapid release (via diffusion into the hydrogel) and a slow release (via microparticles).In the first part, gentamicin (GM)-loaded PLGA microparticles were prepared by double emulsion with evaporation of the solvent. The microparticle preparation method has been optimized to obtain a size of microparticles compatible with the macroporosity of the hydroxyapatite (HA) and a sustained release over 25-30 days. Thus, the time of sonification of the first emulsion was set at 2 minutes in order to obtain a maximal efficacy of encapsulation. The speed of rotation of the second emulsion was fixed at 700 rpm to obtain a 60µm-diameter size of microparticles. The microparticles were analyzed by DSC, TGA and SEM. The antibacterial activity of gentamicin loaded microparticles was demonstrated on S. aureus (CIP224).In the second part we developed a bone substitute where chitosan (CHT) hydrogel was formed in situ in the macroporosity of a tridimensional hydroxyapatite printed piece. This hydrogel was obtained chemically with a crosslinking agent (genipin) to allow injection and a relatively slow gelation. The formation of the CHT hydrogel (2%-wt) was analyzed by UV-Vis spectrophotometry and rheology to optimize the time (24 hours), the temperature (40°C) and the concentration of genipin (0.05%-wt). The study of the release kinetics of ciprofloxacin (CFX) incorporated into the hydrogel (0.1; 0.5 and 1%) showed rapid release (<5 hours) in dynamic system (30 ml/min). The addition of cyclodextrin (CD) in the formulation did not shown a prolonged release of CFX, itself responsible to an increase of the gelation time due to an inclusion of genipin in the CD. Finally the hydrogel was incorporated in the macroporosity of HA before the gelation. Biological evaluation showed its cytocompatibility and antibacterial activity up to 24 hours on E. coli._x000D_In the last part, we developed an injectable bone substitute where HA particles (90 microns) were incorporated into the hydrogel during the preparation. This hydrogel was obtained by a physical way with an anionic polymer of cyclodextrin (PCD) for a fast gelation time (<10 seconds) avoiding sedimentation of the HA. Further study showed that a proportion of at least 3% of CHT and at least 3% of PCD was required for the formation of the hydrogel. Swelling and rheological properties showed the impact of the ratio PCD / CHT, the soluble and insoluble form of the PCD and the addition of HA on the formation of the hydrogel. After lyophilization, the sponge was hydrated in a solution of CFX (2 mg/ml). Biological studies did not shown cytotoxicity and microbiological evaluation showed a prolonged antibacterial activity up to 72 hours on E. coli.In conclusion, this thesis allowed the development of two hybrid bone substitutes for rapid release of CFX (<72 hours) and slow release of gentamicin-loaded microparticles (25-30 days). The incorporation of gentamicin loaded microparticles was possible in both bone substitutes allowing an antibacterial activity until 3 days against S. aureus and E. coli
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Santaniello, Tommaso. "Hybrid microfluidic devices based on polymeric materials functionalized for cell biology applications." Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/14933.
Full textAbstract:
The present thesis work deals with the development of a novel manufacturing protocol for the realization of excimer laser micro-patterned freestanding hydrogel layers (50 to 300 ??m thickness) based on thermo-responsive poly-(N-isopropyl)acrylamide (PNIPAAm) which can operate as temperature-triggered actuators for cells-on-chip applications. PNIPAAm based thin films were synthesized in house and manufactured by an injection/compression moulding based technique in order to obtain flat hydrogels attached to rigid polyvinyl chloride (PVC) substrates to facilitate laser focusing. Laser machining parameters were empirically optimized to fabricate arrays of through-holes with entrance diameter ranging from 30 ??m to 150 ??m and having different exit diameter (from 10 to 20 ??m) on the PNIPAAm employing a stencil aluminum mask. After laser processing, the microstructured layers were detached from the PVC using a chemical treatment and then left to swoll in pure water. The KrF excimer laser machined through-holes could be reversibly modulated in terms of size as a consequence of the polymer volumetric phase transition induced by a temperature change above the critical value of 32 ??C. Thermo-responsiveness characterization was carried out on the detached water swollen freestanding layers using a thermostat bath, by changing the temperature from 18 ??C to 39 ??C and each sample could undergo multiple cycles. As a result of the polymer water loss, the shrinkage of the layer caused the holes to shrink homogeneously, thus reducing their original size of about the 50% in the polymer collapsed state. To prove the functionality of these stimuli-responsive smart surfaces in the frame of cells-on-chip systems, they were integrated in a multilayer microfluidic device to operate as self-regulating cell sorting actuators for single cell assays applications. Using mechanical fastening as the packaging strategy, the hydrated hydrogel was sealed between two micro-milled poly-methyl methacrylate (PMMA) components, which provided the fluid accesses and ducts to the cell suspension to be flown over the thermoresponsive actuator (top layer) and the well to collect the sorted sample (bottom layer). The device is also equipped with a thin transparent heater to control the microfluidic chip temperature. When the system is assembled, the temperature-triggered actuation mechanism was exploited to trap a cellular sample in the shrunken exit hole on the top of the hydrogel layer by applying a negative pressure across the film via the bottom PMMA component when the system is kept at 37 ??C. Subsequently, the sorting of the trapped cell took place through the micro-capillary when the polymer natural relaxation at room temperature towards its initial state occurred; the operational principle of the device was proved using MG63 cells as a model cell line by monitoring the sorting through the size-modulating structures using optical microscopy.
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Cilliers, Joe-Nimique. "Techno-economic evaluation of the hybrid sulphur chemical water splitting (HyS) process / J. Cilliers." Thesis, North-West University, 2010. http://hdl.handle.net/10394/4144.
Full textAbstract:
The constantly growing demand for energy and the consequent depletion of fossil
fuels have led to a drive for energy that is environmentally friendly, efficient and
sustainable. A viable source with the most potential of adhering to the criteria is
nuclear-produced hydrogen. The hybrid sulphur cycle (HyS) is the proposed electrothermochemical
process that can produce the energy carrier, hydrogen. The HyS
consists of two unit operations, namely the electrolyzer and the decomposition
reactor, that decomposes water into hydrogen and oxygen. A techno-economic
evaluation of the technology is needed to prove the commercial potential of the cycle.
This research project focuses on determining the hybrid sulphur cycle’s
recommended operating parameter range that will support economic viability whilst
maintaining a high efficiency. This is done by comparing the results of an evaluation
of four case studies, all operating under different conditions.
The technical evaluation of the research project is executed using the engineering
tool Aspen PlusTM. The models used to achieve accurate results were OLI Mixed
Solvent Electrolyte, oleum data package for use with Aspen PlusTM, which provides
an accurate representation of the H2SO4 properties, and ELECNRTL to provide an
accurate representation of H2SO4 at high temperature conditions. This evaluation
provides insight into the efficiency of the process as well as the operating conditions
that deliver the highest efficiency. The economic evaluation of the research project
determines the hydrogen production costs for various operating conditions. These
evaluations provide a recommended operating parameter range for the HyS to obtain
high efficiency and economic viability.<br>Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2010.
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Sommer, Samantha. "Hybrid Metal-Ligand Hydrogen-Bonded (MLHB) Architectures Based on the Quinolone Subunit: Understanding and Expanding the Accessible Space of Supramolecular Systems." Thesis, University of Oregon, 2015. http://hdl.handle.net/1794/19298.
Full textAbstract:
Despite the prevalence of supramolecular architectures derived from metal-ligand or hydrogen-bonding interactions, few studies have focused on the simultaneous use of these two strategies to form discrete metal-ligand hydrogen-bonded (MLHB) assemblies.
The design, synthesis, and characterization of 2-quinolone based hybrid subunits, 7-DPQ and 5-PYQ, that contain phosphine and pyridyl metal binding sites, respectively, is reported. Both subunits give two-fold symmetric hydrogen-bonded tectons that assemble with metal precursors to give hybrid MLHB structures. Treatment of [Cp*RhCl2]2 with the 7-DPQ subunit yields hybrid MLHB assemblies with closed topology. 1H diffusion ordered spectroscopy experiments established the stability of the structures in solution, and the measured hydrodynamic radii match those determined crystallographically, suggesting that the closed topology is maintained in solution and the solid state.
In order to further explore possible MLHB architectures and test the selectivity boundaries of our quinolone-based subunits we report the selective assembly of 5-PYQ with mono- and bis-platinated anthracene precursors. Addition of 5-PYQ to [1-trans-Pt(PEt3)2NO3]-8-chloroanthracene yielded a hybrid MLHB structure with preorganization for a hybrid MLHB polymer. Despite the systems preorganization for the hybrid polymeric structure the assembly of 5-PYQ with 1,8-bis(trans-Pt(PEt3)2NO3)anthracene selects only for one discrete closed self-assembled macrocycle. The strong π-π stacking interactions of the 5-PYQ subunits erode the hydrogen-bonding fidelity to favor ambidentate coordination modes of 5-PYQ and give the non-hybrid macrocycle.
In the course of investigating the intricacies of hybrid MLHB supramolecular structures we observed that, in addition to metal-ligand and hydrogen-bond interactions, the π-π stacking interactions of the 7-DPQ and 5-PYQ subunits played a critical role in determining the final assemblies. In fact, the prominent π-π interactions were typically found to be more favorable than the quinolone interligand hydrogen-bonding interactions.
These results contribute to the overall knowledge of the design principles, synthesis, characterization, and fundamental assembly trends when exploiting both hydrogen-bonding and metal-ligand interactions to form stable supramolecular architectures. These studies have provided the foundation for expanding the accessible space of supramolecular chemistry to include rationally designed hybrid MLHB systems to give structures that more closely mimic the complex supramolecular systems observed in Nature.
This dissertation includes both previously published/unpublished and co-authored material.<br>10000-01-01
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Solli, Christian. "Fission or Fossil? : A Comparative Hybrid Life Cycle Assessment of Two Different Hydrogen Production Methods." Thesis, Norwegian University of Science and Technology, Industrial Ecology Programme, 2004. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1417.
Full textAbstract:
<p>A comparative hybrid life cycle assessment was conducted to assess two different methods for hydrogen production. Environmental impacts from nuclear assisted thermochemical water splitting are compared to hydrogen production from natural gas steam reforming with CO<sub>2</sub>-sequestration. The results show that the two methods have significantly different impacts. The nuclear alternative has lower impacts on global warming potential, acidification and eutrophication, but very much higher for some of the other impact categories. A weighting procedure is not applied, hence no overall ”winner” can be proclaimed. The different impacts relative importance remains a challenge for eventual decision makers.</p><p>Further the assessment has demonstrated the importance of including economic inputs in a comparative assessment; ordinary process-LCA may produce distorted results since a larger fraction of impacts can be accounted for in one case than in another.</p><p>Another analytical finding is that avoiding double counting of material inputs in the input-output part of the assessment, significantly affects the results of some impact categories. A procedure to avoid double counting should therefore always be applied when performing a hybrid LCA.</p>
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SILVA, ANNA CAMILA SOUSA E. "NUMERICAL AND EXPERIMENTAL SIMULATION OF A HYBRID SOLAR/ETHANOL/HYDROGEN OF AN ELECTRICAL GENERATION SYSTEM." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2017. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=32489@1.
Full textAbstract:
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>PROGRAMA DE EXCELENCIA ACADEMICA<br>O presente trabalho trata da implementação de um sistema integrado de fornecimento de energia elétrica a sistemas isolados da rede de distribuição através de célula a combustível, combustível renovável (etanol) e painéis fotovoltaicos. Apresenta como objetivo a construção de um simulador para a otimização do sistema integrado de fornecimento de energia elétrica. O sistema consiste em um reformador de hidrogênio que utiliza etanol para a reforma do hidrogênio, uma célula a combustível do tipo PEM, painéis fotovoltaicos, banco de baterias de chumbo, inversor de corrente, compressor de hidrogênio. O sistema foi dimensionado para atender um consumidor SIGFI 45. A partir da implementação do sistema foram realizados diferentes tipos de ensaios a fim de caracterizar o funcionamento de cada um dos equipamentos separadamente.
Conhecendo o funcionamento de cada equipamento foi possível simular o funcionamento deles em diferentes condições de operação. Posteriormente foi implementado um simulador em VBA desse sistema e os resultados obtidos experimentalmente foram comparados com os simulados para a validação desse
simulador. Com o simulador validado foi possível simular diversos casos de operação com o intuito de otimizar o funcionamento desse sistema.<br>This current work deals with the implementation of an integrated electrical power supply system with isolated fuel cell distribution networks: renewable fuel (ethanol) and photovoltaic panels. This thesis presents the objective of constructing a simulator in order to optimize the integrated electrical power supply system. The system consists of a hydrogen reformer that uses ethanol to produce hydrogen, a PEM fuel cell, photovoltaic panels, lead battery bank, current inverter, hydrogen compressor. The system has been sized to meet SIGFI 45 consumer. During the implementation and application of the system,
different types of tests were carried out in order to characterize the behavior of each component separately. Knowing the function of each component within the system, it was possible to simulate their behavior in different operating conditions. Later, a VBA simulator of this system was created and then
implemented. The results produced by the simulator were compared with those carried out experimentally to validate the accuracy of this simulation. With the validation of the simulator it was possible to simulate several operational cases in order to optimize the function of this system.
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Heiner, Mark C. "Development and Testing of a Hydrogen Peroxide Injected Thrust Augmenting Nozzle for a Hybrid Rocket." DigitalCommons@USU, 2019. https://digitalcommons.usu.edu/etd/7630.
Full textAbstract:
During a rocket launch, the point at which the most thrust is needed is at lift-off where the rocket is the heaviest since it is full of propellant. Unfortunately, this is also the point at which rocket engines perform the most poorly due to the relatively high atmospheric pressure at sea level. The Thrust Augmenting Nozzle (TAN) investigated in this paper provides a solution to this dilemma. By injecting extra propellant into the nozzle but downstream of the throat, the internal nozzle pressure is raised and the thrust is increased, and the nozzle efficiency, or specific impulse is potentially improved as well. Using this concept, the payload capacity of a launch vehicle can be increased and provides an excellent option for single stage to orbit vehicles.
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SSAJJA, SSALI GODFREY. "Energy flow in a Hybrid Wind/ Hydrogen System for Kampala and Tororo towns in Uganda." Thesis, KTH, Energiteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-200961.
Full textAbstract:
This report presents modeling for energy flow of a distributed renewable energy system based on an integrated wind power and hydrogen production system supplying a local electric load connected to an electric grid. The system consists of a 200kW wind generator, an Electrolyzer with a maximum production capacity of 5kg of hydrogen per 24h and a 3.5kW peak electric load. There is an external connection to the electric grid, assumed large enough to serve as a back-up supply, and whose electricity source of the system is unknown.The main objective of this research was to simulate optimal control strategies that regulate the flow of power from the wind generators to the grid at wind power peaks and from the grid to the Electrolyzer at low wind speeds thereby enabling production of 4-5kg of electrolytic hydrogen for transportation and stationary applications using a renewable resource.The system inputs are hourly wind speed, hourly load demand, and hourly hydrogen demand. The wind generator is modeled as an energy conversion device, which follows the cubic law with cut-in and a maximum speed of 25m/s. The Electrolyzer and compressor are modeled as energy consuming units. The system fully exhausts the wind generator power to meet hydrogen production and electric load requirements per day. The excess power is supplied to the grid while shortages are sourced from the grid. The system outputs are hydrogen production per hour and the power exported to and imported from the grid. The controller thus monitors energy flows from the system and optimizes utilization of the renewable energy source. A computer program using MATLAB for this integrated system is developed, where Energy and hydrogen flow are balanced at each time step depending on the specified strategy. An economic assessment was done to get the annualized costs and the cost of electricity from wind energy in comparison with the electric grid. The system is experimented with hypothetical wind speed data and then validated using wind speed data from two towns in Uganda, Kampala and Tororo Towns.The validation of the model was carried out using wind speeds for Kampala City and Tororo Town in Uganda; the monthly average wind speed were sourced from the RETScreen software with embedded NASA data measured/estimated at 10m above the ground. The Weibull distribution was then used to simulate random hourly data for 24 hours in a day for each particular month of the year as required by the Matlab program. The smart grid application of this model in the production of hydrogen has been investigated and found feasible. The model monitors hydrogen flow within storage and optimizes the flow of power to meet the hydrogen demand for the day. The economic assessment done showed that the cost of electricity from the wind generator was not competitive with the commercial electricity production within the country though there is an environmental benefit in using the wind energy in production of hydrogen, as there are more than 140,000 kg of CO2 emissions saved. Therefore, the results obtained here confirm that such an integrated system has the potential to support remote investments in the production of electrolytic hydrogen from a non-polluting source.<br>Denna rapport presenterar modeller för energiflödet i ett distribuerat system för förnybar energi baserad på ett system med integrerad vindkraft och vätgasproduktion som levererar en lokal elektrisk last är och är ansluten till elnätet. Systemet består av en 200 kW vindgenerator, en elektrolysör med en maximal produktionskapacitet på 5 kg väte per 24 h och en 3,5 kW elektrisk belastning. Det finns en extern anslutning till elnätet, som antas tillräckligt stor för att fungera som en back-up-tillförsel, och vars energikälla är okänd. Huvudsyftet med denna undersökning var att simulera optimala kontrollstrategier som reglerar flödet av ström från vindgeneratorer till elnätet vid vindkrafttoppar och från nätet till elektrolysören vid låga vindhastigheter och därmed möjliggör produktion av 4-5kg av elektrolytisk vätgas för transport och stationära applikationer med hjälp av en förnybar resurs. Systemsimuleringen baseras på vindhastighet, belastningsbehovet, och efterfrågan på väte varje timme. Vindgeneratorn modelleras som en energiomvandlingsanordning, vars effekt ökar kubiskt med vindhastigheten, med cut-in och en maximal hastighet på 25 m / s. Elektrolysören och kompressorn modelleras som energiförbrukande enheter. Systemet uttömmer helt vindgeneratorkraft för att möta produktionen av väte och elektriska belastningskraven per dag. Överskottet ger strömförsörjning till nätet medan brist hämtas från nätet. Simuleringens resultat är väte produktionen per timme och effekten som exporteras till och importeras från nätet. Styrenheten övervakar således energiflöden från systemet och optimerar användningen av förnybar energikälla. Ett datorprogram med hjälp av MATLAB för detta integrerade system utvecklas, där energi och väteflödet balanseras vid varje tidssteg beroende på den angivna strategin. En ekonomisk bedömning gjordes för att få de årliga kostnaderna och kostnaderna för el från vindkraft jämfört med elnätet. Systemet har testats med hypotetiska vindhastighetsdata och sedan validerats med vindhastighets uppgifter från två städer i Uganda, Kampala och Tororo. Det månatliga genomsnittet för vindhastigheten kom från RETScreens programvara med inbyggda NASA uppgifter mätt / beräknad 10m över marken. Weibull-fördelningen användes sedan för att simulera slumpmässiga timvisa uppgifter under 24 timmar i en dag för varje enskild månad under året i enlighet med Matlab-programmet. Smarta elnät med tillämpning av denna modell i produktion av vätgas har undersökts och befunnits genomförbart. Modellen övervakar vätgasflöde till lagring och optimerar kraftflödet för att möta efterfrågan av väte för dagen. Den ekonomiska analysen visade att kostnaden för el från vindgeneratorn kan inte konkurrera med den kommersiella elproduktionen inom landet även om det finns en miljöfördel i att använda vindkraft i produktion av vätgas, eftersom det ger mer än 140.000 kg CO2 sparade utsläpp per år. De erhållna resultaten här bekräftar att ett sådant integrerat system har potential att stödja avlägset belägna investeringar i produktion av elektrolytisk vätgas från en icke förorenande källa.
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Rizo, Pavel. "Mg/transition-metal nanomaterials for efficient hydrogen storage." Thesis, Paris Est, 2018. http://www.theses.fr/2018PESC1050/document.
Full textAbstract:
Nanomatériaux à base de magnésium et de métaux de transition pour un stockage efficace de l'hydrogène. Le magnésium est un élément de choix pour le stockage de l’hydrogène à l’état solide en raison de sa grande abondance dans la croûte terrestre et de ses fortes capacités de sorption massique et volumétrique de l’hydrogène. Cependant, la réaction de sorption souffre d'une cinétique lente et l'hydrure formé est trop stable pour des applications fonctionnant sous conditions ambiantes. Le premier problème peut être résolu en développant des composites associant deux hydrures, MgH2 et TiH2, à l'échelle nanométrique. Ces matériaux sont synthétisés par broyage mécanique sous atmosphère réactive. Cette technique permet la formation des nanocomposites et leur hydrogénation en une seule étape. De plus, ces matériaux peuvent être produits à grande échelle pour les besoins des applications. Les travaux ont été menés en trois parties : i) l’optimisation de la teneur en TiH2 dans le système (1-y)MgH2+yTiH2. Ceci a été accompli en ajustant la teneur en titane (0,0125 ≤ y ≤ 0,3 mole), tout en conservant une bonne cinétique, une réversibilité de l'hydrogène et une durée de vie utile. Les données montrent que la valeur y = 0,025 offre le meilleur compromis pour développer les propriétés les plus adéquates; ii) l'extension à d’autres métaux de transition pour le système 0,95MgH2 + 0,05TMHx (TM: Sc, Y, Ti, Zr, V et Nb), en évaluant la contribution de chaque additif sur la cinétique, sur la réversibilité de l'hydrogène et sur la durée de vie en cyclage; iii) la conception d'un dispositif de cyclage automatique capable de réaliser des centaines de sorption/désorption dans le but de mesurer la durée de vie des hydrures métalliques. Le travail a été effectué à l'aide de nombreuses méthodes expérimentales. Pour la synthèse, le broyage réactif sous atmosphère d'hydrogène a été principalement utilisé. La structure cristalline et la composition chimique des nanomatériaux ont été obtenues à partir de l'analyse par diffraction des rayons X (DRX). La taille et la morphologie des particules ont été déterminées par microscopie électronique à balayage et spectroscopie de rayons X à dispersion d'énergie (SEM / EDS). Les propriétés thermodynamiques, cinétiques et cycliques de la sorption d'hydrogène ont été déterminées par la méthode de Sieverts<br>Mg/transition-metal nanomaterials for efficient hydrogen storageMagnesium metal is a prominent element for solid-state hydrogen storage due to its large abundance in earth’s crust and its high weight and volumetric hydrogen uptakes. However, hydrogen sorption suffers from sluggish kinetics and the formed hydride is too stable for applications working under ambient conditions. The former issue can be solved by developing composites combining two hydrides, MgH2 and TiH2 at the nanoscale. These materials are synthesized by mechanical milling under reactive atmosphere. By this technique, the formation of nanocomposites and their hydrogenation can be obtained in a single-step. Moreover, these materials can be produced at large scale for application purposes. The work focused on three topics: i) the optimization of the TiH2 content in the (1-y) MgH2+yTiH2 system. This was accomplished by optimizing the titanium content (0.0125≤y≤0.3 mole), while keeping good kinetics, hydrogen reversibility and cycle-life. The data show that y=0.025 is the best compromise to fulfill the most practical properties; ii) the extension to other transition metals for the system 0.95MgH2+0.05TMHx (TM: Sc, Y, Ti, Zr, V and Nb), evaluating the contribution of each additive to kinetics, hydrogen reversibility and cycle-life; iii) the conception of an automatic cycling device able to carry out hundreds of sorption cycles whit the aim of measuring the cycle-life of metal hydrides. The work was done using manifold experimental methods. For synthesis, reactive ball milling under hydrogen atmosphere was primarily used. The crystal structure and the chemical composition of nanomaterials was determined from X-ray diffraction (XRD) analysis. Particle size and morphology were obtained by Scanning Electron Microscopy / Energy Dispersive X-Ray Spectroscopy (SEM/EDS). Thermodynamic, kinetic and cycling properties toward hydrogen sorption were determined by the Sieverts method
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Louw, Rudolph Petrus. "Design optimisation and costing analysis of a renewable energy hydrogen system / Rudolph Petrus (Rudi) Louw." Thesis, North-West University, 2012. http://hdl.handle.net/10394/9518.
Full textAbstract:
The South African Department of Science and Technology is striving to develop a means of producing hydrogen gas in remote and civil areas through the use of renewable energy sources. For the purposes of creating such mobile hydrogen production facilities, a small-scale hydrogen production system based on renewable energy sources needs to be developed and modelled. This system is to serve as a pilot plant for further development of a large scale mobile hydrogen production facility.
This work focuses on the characterisation of sizing algorithms for renewable energy sources which can determine component configurations that satisfy power requirements of the system. Additionally, optimal sizing techniques must be developed which can output an optimal plant configuration to a user based on cost and efficiency.
To this end, a literature study was done on all the components that make up a renewable energy hydrogen system. The techniques researched were then applied to create algorithms capable of correctly sizing the required components of such a plant. These techniques were integrated into an application created in the LabVIEW environment, which is capable of outputting an optimal plant configuration based on the specific needs of a client.
A case study was defined with which the results of the simulation models were verified. Using this work, a future, more comprehensive system may be developed and commercialised, building from the techniques implemented here.<br>Thesis (MIng (Computer and Electronic Engineering))--North-West University, Potchefstroom Campus, 2013
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Hertle, Yvonne [Verfasser]. "Structure and dynamics of new intelligent copolymer hydrogels and hydrogel nanoparticle hybrids / vorgelegt von Yvonne Hertle." 2010. http://d-nb.info/1012846601/34.
Full text