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Tamirisa, Prabhakar A. "Plasma polymerized hydrogel thin films for applications in sensors and actuators." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/19827.
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Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2007.Committee Chair: Hess, Dennis W.; Committee Member: Henderson, Cliff L.; Committee Member: Hunt, William D.; Committee Member: Meredith, J. Carson; Committee Member: Prausnitz, Mark R.
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Pareek, Pradeep. "Photo-crosslinked Surface Attached Thin Hydrogel Layers." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2005. http://nbn-resolving.de/urn:nbn:de:swb:14-1115623310082-44480.
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Stimuli sensitive polymers and hydrogels respond with large property changes to small physical and chemical stimuli (e.g. temperature, pH, ionic strength). The bulk behavior of these polymers is widely studied and they show an isotropic swelling. However, thin hydrogel layers of polymers on a substrate show a swelling behavior, which is constrained in some way. Therefore, size, confinement, patternability, response time and transition temperature of thin hydrogel layers are the most important parameters in technological applications and this study focuses on the investigation of these above-mentioned parameters. The aim of this study involves synthesis, characterization and application of thin photo-crosslinked hydrogel layers. Dimethylmaleimide (DMI) moiety was incorporated in the polymers chains and was used to introduce photo-crosslinking by [2+2] cyclodimerization reaction in the presence of UV irradiation. The following photo-crosslinkers based on DMI group were synthesized ? - Acrylate photo-crosslinker (DMIAm) - Acrylamide photo-crosslinker (DMIAAm) - Polyol photo-crosslinker (DMIPA, DMIPACl) The conventional free radical polymerization of above listed photo-crosslinker with its respective monomer resulted in formation of photo-crosslinkable polymers of (a) HEMA, (b) DMAAm, (c) NIPAAm/DMAAm, (d) NIPAAm/Cyclam. The properties of these polymers were investigated by NMR, UV-VIS spectroscopy, GPC and SPR. Thin hydrogel layers were prepared by spin coating on gold-coated LaSFN9 glass. The covalent attachment to the surface was achieved through an adhesion promoter. Swelling behavior of the thin polymer layers was thoroughly investigated by Surface Plasmon Resonance (SPR) Spectroscopy and Optical Waveguide Spectroscopy (OWS). SPR and OWS gave a wide range of information regarding the film thickness, swelling ratio, refractive index, and volume degree of swelling of the thin hydrogel layer. For hydrophilic photo-crosslinked hydrogel layers of HEMA and DMAAm, it was observed that the volume degree of swelling was independent of temperature changes but was dependent on the photo-crosslinker mol-% in the polymer. These surface attached thin hydrogel layer exhibited an anisotropic swelling. For NIPAAm photo-crosslinked hydrogel layers with DMAAm as a hydrophilic monomer, it was observed that both transition temperature (Tc) and volume degree of swelling increases with increase in the mol-% of DMAAm. To study the effect of film thickness on Tc and volume degree of swelling, hydrogels with wide range of film thickness were prepared and investigated by SPR. These results provided vital information on the swelling behavior of surface attached hydrogel layer and showed the versatility of SPR instrument for studying thin hydrogel layers. Later part of project involved synthesis of multilayer hydrogel assembly involving a thermoresponsive polymer and a hydrophilic polymer. The combination of two layers with photo-crosslinkable DMAAm polymer as base layer and photo-crosslinkable NIPAAm polymer as top layer formulate a multilayer assembly where, the base layer only swells in response to temperature and the top layer shows temperature dependent swelling. Photo-crosslinked hydrogel layers of NIPAAm, DMAAm and HEMA shows a high-resolution patterns when irradiated by UV light through a chromium mask. At last this study focused on an important application of these hydrogel layers for cell attachment processes. Cell growth, proliferation and spreading shows a biocompatible nature of these hydrogel surfaces. Such thermoresponsive photo-crosslinkable multilayer structure forms bases for future projects involving their use in actuator material and cell-attachment processes.
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Martwong, Ekkachai. "Design of surface-attached hydrogel thin films with LCST/UCST temperature-responsive properties." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS120/document.
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Les films minces d'hydrogels thermosensibles à propriétés LCST/UCST (Lower/Upper Critical Solution Temperature) avec des températures de transition variables ont été mis au point pour des applications spécifiques. Les réseaux chimiques de polymères fixés de manière covalente sur des substrats solides plans ont été synthétisés par une approche polyvalente et facile à mettre en œuvre en utilisant la chimie click thiol-ène. Elle consiste à déposer des polymères préformés et réactifs en présence des réticulants dithiol sur des substrats modifiés thiol, la réaction de thiol-ène permettant la réticulation simultanée entre chaînes et le greffage en surface. La stratégie CLAG (Cross-Linking And Grafting) donne des films d'hydrogel chimiquement stables et reproductibles avec une large gamme d'épaisseur et avec les propriétés thermostimulables désirées. Les polymères hydrophiles fonctionnalisés par des groupes fonctionnels alcène peuvent être synthétisés en utilisant une copolymérisation radicalaire du monomère souhaité avec du méthacrylate d'allyle dans un solvant organique ou un co-solvant avec de l'eau. Une autre voie est la synthèse dans l'eau en deux étapes: le monomère désiré est copolymérisé avec l'acide acrylique puis le copolymère est modifié par l’allylamine. Trois familles de polymères ont été étudiées: poly(PEGMA), poly(acrylamide) et poly(zwitterion). La température de transition des films d'hydrogel est déterminée en mesurant l'épaisseur dans des solutions aqueuses par ellipsométrie. Les films d'hydrogel de poly(PEGMA) montrent des propriétés de LCST avec la température de transition augmentant avec le nombre d'unités de PEG. La LCST varie de 15°C à 60°C avec deux à cinq unités de PEG dans les chaînes pendantes. La LCST peut également être ajustée en utilisant des copolymères avec différents ratios. Les films d'hydrogel acrylamide ont à la fois des propriétés LCST et UCST. Les films d'hydrogel de poly(sulfobetaïne) montrent un comportement UCST très intéressant en plus d’être « anti-fouling », ce qui est très prometteur pour les applications en biologieTemperature-responsive surface-attached hydrogel thin films with various LCST/UCST (Lower/Upper Critical Solution Temperature) were designed for specific applications. The chemical polymer networks covalently attached on plane solid substrates were synthesized by a versatile and straightforward approach using thiol-ene click chemistry. It consists in coating ene-reactive polymers and dithiol crosslinkers on thiol-modified substrates, the thiol-ene click reaction allowing simultaneous cross-linking between chains and grafting on the surface. The CLAG (Cross-Linking And Grafting) strategy provides chemically stable and reproducible hydrogel films with a wide range of thickness and with the desired temperature-responsive properties. Ene-functionalized hydrophilic polymers can be synthesized using free radical copolymerization of the desired monomer with allyl methacrylate in organic solvent or co-solvent with water. Another way is the synthesis in water in two steps: the desired monomer is copolymerized with acrylic acid and then the copolymer is post-modified by amidification. Three polymer families were investigated: poly(PEGMA), poly(acrylamide) derivatives and poly(zwitterions). The transition temperature of the hydrogel films is determined by measuring the thickness in aqueous solutions at different temperatures with ellipsometry. Poly(PEGMA) hydrogel films show LCST properties with the transition temperature increasing with the number of PEG units. The LCST ranges from 15 °C to 60 °C with two to five PEG units in the pendant chains. The LCST can also be adjusted using mixed copolymers hydrogel. Poly(acrylamide) derivatives hydrogel films have both LCST and UCST properties. Poly(sulfobetaine) hydrogel films show very interesting UCST behavior in addition to be anti-fouling, which is very promising for biology applications
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Martwong, Ekkachai. "Design of surface-attached hydrogel thin films with LCST/UCST temperature-responsive properties." Electronic Thesis or Diss., Sorbonne université, 2018. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2018SORUS120.pdf.
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Les films minces d'hydrogels thermosensibles à propriétés LCST/UCST (Lower/Upper Critical Solution Temperature) avec des températures de transition variables ont été mis au point pour des applications spécifiques. Les réseaux chimiques de polymères fixés de manière covalente sur des substrats solides plans ont été synthétisés par une approche polyvalente et facile à mettre en œuvre en utilisant la chimie click thiol-ène. Elle consiste à déposer des polymères préformés et réactifs en présence des réticulants dithiol sur des substrats modifiés thiol, la réaction de thiol-ène permettant la réticulation simultanée entre chaînes et le greffage en surface. La stratégie CLAG (Cross-Linking And Grafting) donne des films d'hydrogel chimiquement stables et reproductibles avec une large gamme d'épaisseur et avec les propriétés thermostimulables désirées. Les polymères hydrophiles fonctionnalisés par des groupes fonctionnels alcène peuvent être synthétisés en utilisant une copolymérisation radicalaire du monomère souhaité avec du méthacrylate d'allyle dans un solvant organique ou un co-solvant avec de l'eau. Une autre voie est la synthèse dans l'eau en deux étapes: le monomère désiré est copolymérisé avec l'acide acrylique puis le copolymère est modifié par l’allylamine. Trois familles de polymères ont été étudiées: poly(PEGMA), poly(acrylamide) et poly(zwitterion). La température de transition des films d'hydrogel est déterminée en mesurant l'épaisseur dans des solutions aqueuses par ellipsométrie. Les films d'hydrogel de poly(PEGMA) montrent des propriétés de LCST avec la température de transition augmentant avec le nombre d'unités de PEG. La LCST varie de 15°C à 60°C avec deux à cinq unités de PEG dans les chaînes pendantes. La LCST peut également être ajustée en utilisant des copolymères avec différents ratios. Les films d'hydrogel acrylamide ont à la fois des propriétés LCST et UCST. Les films d'hydrogel de poly(sulfobetaïne) montrent un comportement UCST très intéressant en plus d’être « anti-fouling », ce qui est très prometteur pour les applications en biologieTemperature-responsive surface-attached hydrogel thin films with various LCST/UCST (Lower/Upper Critical Solution Temperature) were designed for specific applications. The chemical polymer networks covalently attached on plane solid substrates were synthesized by a versatile and straightforward approach using thiol-ene click chemistry. It consists in coating ene-reactive polymers and dithiol crosslinkers on thiol-modified substrates, the thiol-ene click reaction allowing simultaneous cross-linking between chains and grafting on the surface. The CLAG (Cross-Linking And Grafting) strategy provides chemically stable and reproducible hydrogel films with a wide range of thickness and with the desired temperature-responsive properties. Ene-functionalized hydrophilic polymers can be synthesized using free radical copolymerization of the desired monomer with allyl methacrylate in organic solvent or co-solvent with water. Another way is the synthesis in water in two steps: the desired monomer is copolymerized with acrylic acid and then the copolymer is post-modified by amidification. Three polymer families were investigated: poly(PEGMA), poly(acrylamide) derivatives and poly(zwitterions). The transition temperature of the hydrogel films is determined by measuring the thickness in aqueous solutions at different temperatures with ellipsometry. Poly(PEGMA) hydrogel films show LCST properties with the transition temperature increasing with the number of PEG units. The LCST ranges from 15 °C to 60 °C with two to five PEG units in the pendant chains. The LCST can also be adjusted using mixed copolymers hydrogel. Poly(acrylamide) derivatives hydrogel films have both LCST and UCST properties. Poly(sulfobetaine) hydrogel films show very interesting UCST behavior in addition to be anti-fouling, which is very promising for biology applications
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Pillai, Karthikeyan Chyan Oliver Ming-Ren. "FTIR-ATR characterization of hydrogel, polymer films, protein immobilization and benzotriazole adsorption on copper surface." [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-5132.
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Xu, Zuxiang. "Underwater Adhesion between Biopolymer Model Surfaces and Hydrogels." Electronic Thesis or Diss., Université Paris sciences et lettres, 2022. http://www.theses.fr/2022UPSLS020.
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Alors que l'adhésion entre matériaux synthétiques a été plutôt bien étudiée expérimentalement et théoriquement, les mécanismes de bioadhésion sont encore très peu compris. Une manière de les aborder serait d’utiliser des systèmes biopolymères qui pourraient imiter biosurfaces, biotissus et bioadhésifs. Cependant, cette idée est confrontée à la difficulté de concevoir une structure modèle et de contrôler les propriétés physico-chimiques des matériaux fabriqués à partir de biopolymères. Les mécanismes de bioadhésion peuvent être mieux compris en étudiant l'adhésion en milieu immergé entre adhésifs hydrogels et substrats solides modifiés par des films minces d'hydrogel. Cela permet de séparer la contribution interfaciale avec des interactions spécifiques moléculaires et de la contribution du volume avec les propriétés viscoélastiques à l'adhésion. Dans un premier temps, nous avons conçu un système modèle avec de la gélatine et noua avons étudié l'adhésion en milieu immergé favorisée par des interactions électrostatiques. D'une part, des films stables de gélatine attachés en surface d’épaisseur et de gonflement finement ajustables ont été réalisés en utilisant la stratégie Cross-Linking and Grafting (CLAG). D'autre part, des adhésifs hydrogels de gélatine à double réticulation ont été synthétisés en ajoutant des réticulations chimiques aux réseaux de gélatine physiques. La structure microscopique des réticulations physique et chimique a été bien contrôlée, avec la détermination de la longueur de chaîne entre les réticulations à partir du module de cisaillement et du modèle de réseau fantôme. L'adhésion en milieu immergé mesurée par des tests de probe-tack a montré que les hydrogels de gélatine à double réticulation ont les mêmes propriétés adhésives quelle que soit la température, même si leur résistance diminue avec le chauffage. Nous avons également été en mesure de séparer les effets des réseaux physiques et chimiques sur l'adhésion. Dans un deuxième temps, nous avons étudié l'adhésion en milieu immergé entre des réseaux doubles contenant du carraghénane et des substrats solides modifiés par des micro-motifs d’hydrogels. Il a été démontré que plus les micro-motifs sont petits, plus l'énergie d'adhésion est élevée. Ce travail a fourni un aperçu des paramètres physico-chimiques et physiques qui contrôlent l'adhésion en milieu immergé des systèmes biopolymères tels que les propriétés viscoélastiques en volume, la charge et la topographie de la surface. Il aidera à mieux comprendre la bioadhésion et à concevoir des adhésifs efficaces en milieux aqueuxWhile the adhesion between synthetic materials has been rather well-studied experimentally and theoretically, there is still a lack of knowledge on bioadhesion, which could be tackled with biopolymer systems which could mimic biosurfaces, biotissues and bioadhesives. However, this idea is limited by the difficulty in designing a model structure and controlling the physical chemistry properties of biopolymer-made materials. Bioadhesion mechanisms can be tackled by studying the underwater adhesion between hydrogel adhesives and solid substrates modified by hydrogel thin films. This allows to separate interfacial contribution with molecular specific interactions and bulk contribution with viscoelastic properties to adhesion. First, a model system based on gelatins has been designed and underwater adhesion promoted by electrostatic interactions was investigated. On one side, stable surface-attached gelatin films with finely adjustable thickness and swelling were achieved using Cross-Linking and Grafting (CLAG) strategy. On the other side, dual-crosslinked gelatin hydrogel adhesives were synthesized by adding chemical crosslinks to physical gelatin networks. The microscopic structure of both physical and chemical crosslinks was well-controlled, with the determination of the chain length between crosslinks from shear modulus and phantom network model. Underwater adhesion measured by probe tack tests showed that dual-crosslinked gelatin hydrogels have the same adhesive properties at all temperatures even if their strength decreases with heating. We were also able to separate the effects of physical and chemical networks on adhesion. Second, the underwater adhesion between double-networks containing carrageenan and solid substrates modified by micro-patterned hydrogels was investigated. It was shown that the smaller the micro-patterns the higher the adhesion energy. This work has provided an insight of the physico-chemical and physical parameters that control underwater adhesion of biopolymers systems such as the bulk viscoelastic properties, the charge and the topography of the surface. It would help for better understanding bioadhesion and designing underwater adhesives
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Serpe, Michael Joseph. "Self-Assembly of Poly(N-isopropylacrylamide) Microgel Thin Films." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4806.
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The assembly of poly(N-isopropylacrylamide-co-acrylic acid) (pNIPAm-co-AAc) microgel thin films into disordered and ordered arrays was investigated. Disordered pNIPAm-co-AAc microgel arrays were assembled based on electrostatic attractions between polyanionic pNIPAm-co-AAc microgels and polycationic poly(allylamine hydrochloride) (PAH). These interactions were studied in solution and subsequently used to assemble thin films following a Layer-by-Layer assembly protocol. Thin films were assembled as a function of pNIPAm-co-AAc microgel solution temperature and the resultant film thermoresponsivity characterized as a function of microgel layer number and pH. The response of assembled thin films to pH 3.0 and 6.5 exposure was then characterized by quartz crystal impedance and surface plasmon resonance spectroscopy, which showed that the thin film solvation was highly dependent on the pH of the solution it was in. Assembled thin films were also shown to be useful as controlled drug delivery platforms, where it was found that small molecules could be released from the films in a temperature regulated fashion. Microgel thin films also exhibited unique optical properties and were used as microlens arrays, which were able to focus pattern in air as well as in solution and had focal lengths that could be tuned in response to pH and temperature changes. Ordered microgel arrays were assembled following a thermal annealing process, in order to make light diffracting materials. These ordered arrays were photopolymerized and exhibited temperature dependent Bragg diffraction properties.
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Augustine, Anusree. "Swelling induced debonding of thin hydrogel films grafted on silicon substrate : the role of interface physical-chemistry." Electronic Thesis or Diss., Université Paris sciences et lettres, 2022. http://www.theses.fr/2022UPSLS040.
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Les revêtements d'hydrogel sont des réseaux de polymères transparents et hydrophiles capables d’abosrber plusieurs fois leur épaisseur en eau. Cependant, les contraintes induites par le gonflement du film peuvent entraîner un décollement préjudiciable de l'hydrogel ce qui peut limiter l’utilisation pratique des ces revêtements. Dans cette étude, nous proposons de décrire les mécanismes de décollement de films minces d’hydrogel en fonction de leur densité de greffage à l'interface film/substrat. Le but est de pouvoir contrôler et prédire la dégradation des revêtements hydrogel pendant le gonflement ou sous des contraintes de contact. Dans ce but, nous avons développé une méthodologie permettant de mesurer l'initiation et la propagation de la délamination induite par le gonflement de films minces d’hydrogel à partir de défauts d'interface préexistants bien contrôlés.Des films minces d'hydrogel de poly(diméthylacrylamide) (PDMA) attachés à la surface sont préparés sur des plaquettes de silicium à partir de la réticulation et du greffage simultanés (CLAG) de chaînes polymères fonctionnalisées par la chimie click thiol-ène. Cette stratégie permet de faire varier l'épaisseur du film (0.1 - 2 µm) et de contrôler le taux de gonflement du réseau, ici fixé à 2, tout en assurant une densité de réticulation homogène. Afin de faire varier la résistance de l'interface film/substrat, le substrat en silicium est greffé avec des mélanges de mercaptosilane (réactif) et de propylsilane (inerte) dans différentes proportions avant le dépôt du film mince. Alors que le mercaptosilane est capable de former des liaisons covalentes avec le réseau PDMA, le propylsilane ne réagit pas, ce qui permet de contrôler le taux de greffage du film mince d’hydrogel sur le substrat. Nous caractérisons la fraction de surface de mercaptosilane ainsi obtenue par des analyses XPS et TOF-SIMS. Par ailleurs, toujours à l’interface subtrat/film, des défauts linéaires bien contrôlés ayant une faible adhérence (largeur entre 10 et 100 µm) sont créés sur le substrat en passivant de façon localisée les groupes thiol réactifs par microlithographie. Ces défauts nucléent le décollement des films de façon bien localisée, ce qui permet ensuite de suivre la propagation de la décohésion à partir de ces défauts.Le décollement du film induit par le gonflement est réalisé sous un flux de vapeur constant assurant la saturation du film en eau. En observant le décollement progressif du film à partir des défauts linéaires préexistants, nous retrouvons un motif d’instabilité classique dit de fil de téléphone et nous montrons que le décollement résulte de contraintes de gonflement localisées proche de la ligne de décollement. Nous mesurons la vitesse de propagation du décollement dans la zone où le film est greffé sur le substrat et nous observons qu’elle augmente de deux ordres de grandeur lorsque la quantité de propylsilane dans le mélange de silanes réactifs passe de 0 à 90 %, c’est-à-dire lorsque le taux de greffage du film décroit. Un seuil d'épaisseur pour le décollement est également observé, les films pouvant se décoller étant d’autant plus minces que le taux de greffage du film ets faible. Les mesures de ce seuil sont discutées à partir d'un argument simple de mécanique de la rupture qui permet de rendre compte semi quantitativement de nos mesuresHydrogel coatings are transparent and hydrophilic polymer networks that absorb a lot of water and can be suitable candidates for anti-mist coatings. However, swelling-induced stresses within the film can result in detrimental debonding of hydrogel and may fail. In this study, these debonding processes are investigated in the relation to the grafting density at the film/substrate interface, so as to control and predict the failure of the coatings during swelling or under contact stresses. For that purpose, we have developed a methodology consisting in monitoring the initiation and the propagation of swelling-induced delamination from well-controlled preexisting interface defects.Surface-attached poly(dimethylacrylamide) (PDMA) hydrogel thin films are prepared on silicon wafers from the simultaneous Cross-Linking And Grafting (CLAG) of functionalized polymer chains by thiol-ene click chemistry. This strategy allows to tune the film thickness (0.1-2 µm) while ensuring a homogeneous crosslinking density. In order to vary the strength of the film/substrate interface, the silicon wafer is grafted by mixing reactive mercaptosilane and unreactive propylsilane in various proportions prior to the formation of the hydrogel film. We characterize the mercaptosilane surface fraction thus obtained by XPS and TOF-SIMS analyses. Well-controlled line defects (width between 2 and 100 µm) are also created to nucleate delamination of the hydrogel from the substrate.Swelling-induced debonding of the film is achieved under a constant vapor flow ensuring water saturation. Optical observations show the progressive debonding of the film from the pre-existing line defects under the action of localized swelling stresses. We obtain a delamination pattern of typical so-called telephone cord instability. We measure the debonding propagation velocity where the hydrogel is grafted to the substrate. The debonding rate is found to decrease over two orders of magnitude when the amount of mercaptosilane in the reactive silane mixture is increased from 10% to 100% while increasing the covalent bonds between hydrogel and substrate. A threshold thickness for debonding is also observed. This threshold thickness increases with the amount of mercaptosilane used to graft the substrate. We derived quantitative values of the interface fracture energy from the measured thickness threshold with a simple fracture mechanics model
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Pillai, Karthikeyan. "FTIR-ATR Characterization of Hydrogel, Polymer Films, Protein Immobilization and Benzotriazole Adsorption on Copper Surface." Thesis, University of North Texas, 2007. https://digital.library.unt.edu/ark:/67531/metadc5132/.
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Plasma polymerization techniques were used to synthesize and deposit hydrogel on silicon (Si) substrate. Hydrogel is a network of polymer chains that are water-insoluble and has a high degree of flexibility. The various fields of applications of hydrogel include drug release, biosensors and tissue engineering etc. Hydrogel synthesized from different monomers possess a common property of moisture absorption. In this work two monomers were used namely 1-amino-2-propanol (1A2P) and 2(ethylamino)ethanol (2EAE) to produce polymer films deposited on Si ATR crystal. Their moisture uptake property was tested using FTIR-ATR technique. This was evident by the decrease in -OH band in increasing N2 purging time of the films. Secondly, two monomer compounds namely vinyl acetic acid and glycidyl methacrylate which have both amine and carboxylic groups are used as solid surface for the immobilization of bovine serum albumin (BSA). Pulsed plasma polymerization was used to polymerize these monomers with different duty cycles. Initial works in this field were all about protein surface adsorption. But more recently, the emphasis is on covalent bonding of protein on to the surface. This immobilization of protein on solid surface has a lot of applications in the field of biochemical studies. The polymerization of vinyl acetic acid and glycidyl methacrylate were shown as successful method to attach protein on them. Chemical mechanical polishing (CMP) of Cu is one of the processes in the integrated chips manufacturing industry. Benzotriazole is one of the constituents of this CMP slurry used as corrosion inhibitor for Cu. Benzotriazole (C6H5N3) is a nitrogen heterocyclic derivative having three nitrogen atoms, each with an unshared pair of electrons, forming five-membered ring structure. This molecule coordinates with Cu atoms by loosing a proton from one of its nitrogen atom and thereby forming a film which is polymeric in nature that prevents further oxidation of Cu. In this work, aqueous solution of BTA was used to study the adsorption characteristics on Cu when a Cu electrodeposited Si was immersed in to it. This study was performed using ATR-FTIR technique. The adsorption of BTA on Cu surface was evident by the presence of aryl C-H stretching band at 3061 cm-1.
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Nogueira, Grinia Michelle. "Hidrogeis e filmes de fibroina de seda para fabricação ou recobrimento de biomateriais." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/267124.
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Orientador: Marisa Masumi BeppuTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: Hidrogéis e filmes de fibroína de seda foram preparados e caracterizados com o objetivo de avaliar sua potencial aplicação no campo de biomateriais. Hidrogéis foram obtidos durante a etapa de diálise da solução de fibroína de seda e suas propriedades físicas, químicas, citotoxicidade e potencial de calcificação in vitro foram determinados. Esses materiais apresentaram estrutura tridimensional porosa com resistência mecânica à compressão relativamente alta e grande potencial de calcificar in vitro, sendo possíveis candidatos à aplicação na área de regeneração óssea. Filmes de fibroína de seda com quitosana foram preparados utilizando-se a técnica "Layer-by-Layer". Com esta técnica, foi possível depositar filmes anisotrópicos, com fibras alinhadas na superfície de substratos de silício. Como os biopolímeros em estudo são conhecidamente biocompatíveis, o alinhamento de fibras na superfície do substrato poderia ser explorado como um meio de guiar a adesão e proliferação celular ou ainda agregar resistência mecânica a outros filmes poliméricos. Filmes de fibroína de seda foram também empregados para recobrir pericárdio bovino utilizado na fabricação de válvulas cardíacas. Amostras recobertas com fibroína de seda foram avaliadas quanto à sua propensão à calcificação in vitro e os filmes foram testados quanto a sua citotoxicidade e potencial de adesão e crescimento de células endoteliais. Os resultados indicaram que filmes de fibroína de seda não apresentam citotoxicidade, são compatíveis com células endoteliais e não induzem a calcificação do pericárdio bovino recoberto durante os testes in vitro. Assim, o recobrimento com fibroína de seda pode ser uma alternativa de tratamento do pericárdio bovino para funcionalização da sua superfície. Dos resultados apresentados, concluiu-se que tanto hidrogéis como filmes derivados de fibroína de seda podem ser aplicados no campo de biomateriais, sejam como matrizes para reconstituição óssea, ou filmes para recobrimento e funcionalização da superfície de materiais.
Abstract: Silk fibroin hydrogels and films were prepared and characterized in order to investigate their potential application in the biomaterials field. The hydrogels were obtained during the dialysis step and their physical and chemical characteristics, cell toxicity and compatibility and potential to calcify in vitro were investigated. Those materials presented a porous tridimensional structure, mechanical strength and ability to deposit calcium phosphate crystals during in vitro calcification tests; therefore, silk fibroin hydrogels can probably be used in the bone regeneration field. Silk fibroin films were obtained by using the Layer-by-Layer technique. Bidirectional alignment of silk fibroin fibers was designed by adjusting the substrate position during the dipping process. A potential application to films with alignment of fibers is to guide cell adhesion and proliferation, since the biopolymers used to build the films are known as biocompatible materials. Silk fibroin films were also used to coat bovine pericardium used to fabricate cardiac valves. The coated samples were characterized by in vitro calcification tests and biocompatibility of silk fibroin films was evaluated by citotoxicity tests and their ability to adhere and grow of endothelial cells. The results showed that silk fibroin films are biocompatible and do not induce calcification during in vitro calcification tests, being suitable to coatand functionalize bovine pericardium surface. From the presented results, it can be concluded that silk fibroin hydrogels and films are suitable materials to be explored in the biomaterials field, for bone regeneration or biomaterials surface coating.
Doutorado
Engenharia de Processos
Doutor em Engenharia Química
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Moraes, Mariana Agostini de 1985. "Obtenção e caracterização de materiais micro e nanoestruturados contendo fibroína de seda combinada a outros polímeros biocompatíveis para contato com células." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266126.
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Orientador: Marisa Masumi BeppuTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: Neste estudo, a fibroína de seda foi explorada no preparo de materiais micro e nanoestruturados, em estruturas bi- e tridimensionais, visando o uso em biomateriais. Para isto, foi estudada a incorporação de microfibras de fibroína em hidrogéis de colágeno, formando uma estrutura 3D, e a formação de filmes ultrafinos contendo fibroína pelo método layer-by-layer. No primeiro caso, a fibroína de seda foi explorada como um material promissor para reforçar mecanicamente os hidrogéis de colágeno devido às suas ótimas propriedades mecânicas e também por apresentar citocompatibilidade adequada com diversos tipos de células. Os resultados mostraram uma boa interação entre as microfibras de fibroína e as fibrilas de colágeno, além de melhorias na resistência mecânica dos hidrogéis. Os hidrogéis contendo fibroína foram capazes não somente de manter o desempenho biológico do colágeno, mas de melhorar a proliferação celular. Os resultados obtidos sugerem que hidrogéis de colágeno podem ser microestruturados com fibroína de seda e representam um material promissor para uso em engenharia tecidual vascular. Já para o caso dos filmes ultrafinos (2D), foi estudada a formação dos mesmos através do método conhecido como layer-by-layer, pela técnica de imersão de substrato em solução polimérica. Como pares catiônicos foram estudados a quitosana e o hidrocloreto de poli(alilamina), sendo possível controlar a formação de fibrilas nanométricas de fibroína de seda através da variação do par polimérico. Fibrilas alinhadas de fibroína foram observadas no filme layer-by-layer com quitosana, porém no filme com hidrocloreto de poli(alilamina) não foram observadas fibrilas. A densidade de cargas do par polimérico é a característica que governa a formação de fibrilas na escala nanométrica. A etapa de secagem entre cada camada também é fundamental para a formação e estabilização dos filmes, que apresentaram coexistência de conformação molecular seda I e seda II. A viabilidade celular permaneceu entre 90 e 100% em todos os filmes estudados, porém o padrão de topografia imposto pelas fibrilas de fibroína não orientou o crescimento e adesão celular. Filmes finos multicamadas nanoestruturados com fibroína de seda possuem aplicação potencial na área biomédica, como recobrimentos e superfícies funcionais
Abstract: In this study, silk fibroin was explored in the preparation of micro and nanostructured materials, in bi- and tridimensional structures, aiming the use in the biomaterials field. For that, the incorporation of fibroin microfibers in collagen hydrogels forming a 3D structure was studied. We also studied the formation of ultrathin films containing fibroin by the layer-by-layer method. In the first case, the silk fibroin was explored as a promising material to mechanically reinforce collagen hydrogels due to its good mechanical properties and also for having cytocompatibility adequate with several cell types. The results showed a good interaction between fibroin microfibers and collagen fibrils, as well as improvements in the mechanical resistance of the hydrogels. The hydrogels containing fibroin were capable to maintain the biological behavior of collagen and also to improve cell proliferation. The results suggest that collagen hydrogels can be microstructured with silk fibroin and represent a promising material for use in vascular tissue engineering. In the case of the ultrathin films (2D), the formation of these films was studied by the layer-by-layer method, using the technique of substrate dipping in a polymeric solution. Chitosan and poly (allylamine hydrochloride) were used as cationic pair species, being possible to control the formation of nanometric fibrils of fibroin by varying the polymeric pair. Fibroin aligned fibrils were observed in the layer-by-layer film with chitosan, while no fibrils were observed in the film with poly (allylamine hydrochloride). The charge density of the polymeric pair is the main characteristic that governs the fibrils formation at the nanometric scale. The drying step between each layer is also essential for formation and stabilization of the films that show the co-existence of molecular conformation of silk I and silk II. Cell viability between 90 and 100% was attained for all the studied films; however the topographic pattern imposed by the fibroin fibrils did not orient cell adhesion and growth. Multilayer thin films nanostructured with silk fibroin have potential for application in the biomedical field, as coatings and functional surfaces
Doutorado
Engenharia Química
Doutora em Engenharia Quimica
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Ali, Momen Sayed Ahmed [Verfasser], Dirk [Akademischer Betreuer] Kuckling, and Klaus [Akademischer Betreuer] Huber. "Synthesis and characterization of photo-crosslinkable polymers and hydrogel thin films / Momen Sayed Ahmed Ali. Betreuer: Dirk Kuckling ; Klaus Huber." Paderborn : Universitätsbibliothek, 2012. http://d-nb.info/1036552071/34.
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Hecht, Mandy. "Particulate systems and thin-film based platforms." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2015. http://dx.doi.org/10.18452/17329.
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Die Verbindung von hoch entwickelten Nanomaterialien mit fluoreszenzbasierten Technologien hat sich zu einem aufstrebenden Forschungsbereich entwickelt. Nichtsdestotrotz ist bis heute der Schritt von einem organischen Indikatormolekül zum anwendbaren Sensorsystem ein komplexer Prozess. Diese Arbeit zielte darauf ab, sensorische Materialien verschiedener chemischer Natur für diverse Analyten zu entwickeln, zu charakterisieren und zu etablieren. Hierbei wurden zunächst pH sensitive Fluoreszenzfarbstoffe entwickelt und in dünnen Membranen immobilisiert. Der Teststreifen ermöglicht die Beurteilung von pH-Änderungen mit dem Auge. Darüber hinaus wurde gezeigt, wie diese Farbstoffe auch in eine wasserlösliche Form überführt werden können. Damit konnten lokale pH-Änderungen an der Wachstumsfront von Silikat-Biomorphs detektiert werden. Auch partikuläre Systeme stellten sich als geeignete Materialien heraus. Es konnte gezeigt werden, wie die Silikat-Matrix von Partikeln zu verbesserten Eigenschaften für Farbstoffe führt. Mittels farbstoffbeladener Partikel konnte in einem Lateral-Flow-Assay ein schneller Nachweis von TATP etabliert werden. Ein anderer Ansatz verfolgte das Ziel des sensitiven Nachweises von Quecksilberionen in Wasser. In einem anderen System konnten Silikat-Nanopartikeln so funktionalisiert werden, dass ein sensitiver und selektiver Nachweis von Schwermetallionen und Anionen über ein Quencher-Displacement-Assay gelang. Zusätzlich wurde die einzigartige Oberfläche von Zellulosepartikeln mithilfe eines neu entwickelten Fluoreszenzfarbstoffs untersucht. Die untersuchten Materialien und Strategien zeigen, wie leicht innovative Moleküle für potentielle sensorische Systeme im wässrigen Medium auf Basis von fluoreszierenden Partikeln und dünnen Schichten geschaffen werden können. Das Verhalten der hergestellten Materialien wurde über spektroskopische Methoden evaluiert und dabei, wenn möglich, die Parameter Sensitivität, Selektivität und Ansprechzeit beurteilt.The combination of fluorescence and nanomaterials has developed into an emerging research area. Nonetheless until now the step from an organic sensory molecule to a final sensor format is a complex endeavor. This thesis aimed at the preparation of particulate and thin-film based platforms for various analytes through combining the features of an appropriate host material with outstanding properties of dyes concomitant with sensitive fluorescence detection techniques. In particular, pH sensitive fluorescent probes were sterically immobilized into a thin membrane. The dip-stick allows the assessment upon change in pH with the eye. Especially a probe working at high basic pH range was converted into a water-soluble analogue and was directly applied at the growth front of silica biomorphs to detect local pH changes. But also particulate structures are suitable host materials. It is shown how the silica matrix of nanoparticles lead to improved optical properties for embedded dyes. The interactions of silica and fluorescent dyes within the pores of mesoporous particles were exploited to develop an actual sensor format based detection of TATP. In another approach it was possible to detect mercury ions in water. Heavy metal ions were also successfully detected in a quencher displacement assay involving receptor-dye functionalized silica nanoparticles. The impact of the unique surface properties of cellulose microparticles was shown by a fluorescent dye which allows an assessment of the surface functional groups and microenvironment through the reactivity and its changes in the optical properties. The performance of the prepared materials were evaluated mostly by spectroscopic methods and if possible assessed in terms of sensitivity, selectivity and response time. The newly developed and investigated materials based on fluorescent particulate and thin-films show the facile application of innovative sensor probes for potentially sensing devices.
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Votte, Guillaume. "Synthèse de cristaux photoniques modulables à partir de films minces d’hydrogel stimulables." Electronic Thesis or Diss., Université Paris sciences et lettres, 2020. http://www.theses.fr/2020UPSLS010.
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La recherche dans le domaine des cristaux photoniques synthétiques progresse à grande vitesse. En parallèle, les progrès réalisés dans le domaine de la matière molle et des polymères permettent également des avancées considérables pour des dispositifs stimulables. Dans ces travaux de thèse, nous avons développé une plateforme permettant désynthétiser des nano- et microstructures d'hydrogel stimulables stables et à grandes amplitudes de déformation. Pour ce faire, nous avons utilisé la méthode CLAG (Cross-LinkingAnd Grafting) qui consiste en la réticulation et le greffage simultanés de chaînes de polymère sur le substrat. Nous avons exploité cette plateforme pour mettre au point des miroirs de Bragg stimulables à grande amplitude de décalage spectral, avec des multicouches alternéesd’hydrogels et des couches d’or ou d’oxyde de titane Nous avons également développé des cristaux photoniques bidimensionnels en utilisant des masques photolithographiques. De plus, l’hyperthermie plasmonique ou magnétique est envisagée pour induire la transition des films d’hydrogel. Enfin, nous avons montré que la plateforme d’hydrogels permet également de coupler la température avec d’autres stimuli: chimiques, mécaniquesResearch in the field of synthetic photonic crystals has been advancing at high speed. In thedevelopment of this field, additional performances in terms of modularity and switchabilityusing soft matter and polymers provide unprecedented enhanced devices. In this thesis, wedeveloped a platform of stimuli-responsive nano- and microstructured polymer hydrogelsthat are surface-grafted to ensure chemical stability regardless of environmental change.This strategy is based on CLAG chemistry which consists in simultaneous Cross-Linking AndGrafting of polymer chains on the substrate. This platform is exploited to fabricate stimulableBragg mirrors with large amplitude of spectral shift. We also developed a strategy allowingus to design two-dimensional photonic cristals by using photolithographic masks. Finally, wedemonstrated that the hydrogel platform allows the coupling of temperature with otherstimuli: chemical, mechanical, light and electromagnetic field for plasmonic and magnetichyperthermia
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Song, Gang. "Hydrogen in thin niobium films." [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=961906529.
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Siviero, Giacomo. "Magnesium-based thin films for hydrogen storage." Doctoral thesis, Università degli studi di Padova, 2009. http://hdl.handle.net/11577/3426607.
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Magnesium hydride, MgH2, is one of the most studied reversible hydrides, due to its high gravimetric hydrogen density and energy density; unfortunately thermodynamic issues and slow kinetics are limiting its use in technological applications. Recently, it has been shown that great improvements can be attained by using nanostructured powders and catalysts.
Currently a lot of research effort is focused on the relation between microstructure, functional properties, and reliability: concerning this point thin films constitute a model material, due to the easy control of microstructure and the possibility of using complementary characterization techniques.
We first study the relation between the evolution, upon successive H2 cycling, of the crystalline degree and the H2 sorption properties of Pd capped-textured Mg thin films grown on Si and glass substrate by r.f. sputtering. The use of complementary characterization techniques provides information on structural, morphological and functional properties. By in-situ continuous grazing angle x-ray diffraction measurements we follow the structural transformations during the hydrogen desorption process, estimating enhanced kinetics and lower activation energy than bulk magnesium, thanks to nanostructure. The optimized diffraction geometry reveals that the initial preferential growth, typical of thin films, is lost after the first absorption/desorption cycle, showing the hydrogen-induced re-orientation of Mg crystallites. Moreover magnesium, upon hydride formation, transforms from a metal to a wide band gap semiconductor, hence showing interesting electrical and optical properties, which are studied by spectrophotometry; the switchability from a metal with high reflectance to a semiconductor with colourless high transmittance is promising for smart coatings and sensors. The Pd cap layer integrity and related surface effects are found to be crucial to the stability of functional properties during absorption/desorption cycling: the progressive degradation of Pd coverage of Mg film leads to a slowing down of kinetics, up to a complete process inhibition. Future developments of this study envisage further strategies to improve cycling stability and to speed up kinetics (e.g. by addition of suitable catalysts); as a starting point Ti-doping of Mg is considered: the non-equilibrium synthesis (sputtering) allows a high degree of mixing of these two otherwise immiscible elements, leading to peculiar structural properties stable upon cycling. By increasing Ti concentration it is possible to attain an enhanced hydrogen absorption/desorption kinetics, thanks to a hydride structure which favours hydrogen transport. By in-situ diffraction measurements structural transformations occuring during desorption are monitored and then compared with concurrent optical transmittance measurements, which provide an indirect estimation of hydrogen release kinetics, whose enhancement results into hydride decomposition even at room temperature. Mg-Ti system demonstrated to be a very fascinating and promising one, and therefore will be the subject of further investigations.L'idruro di magnesio, MgH2, è uno dei più studiati idruri reversibili, data la sua elevata densità gravimetrica ed energetica; sfortunatamente, l'eccessiva stabilità termodinamica e le cinetiche lente ne impediscono l'uso per applicazioni tecnologiche. Recentemente è stato dimostrato che notevoli miglioramenti possono essere ottenuti grazie all'uso di materiali nanostrutturati e catalizzatori. Attualmente la ricerca scientifica è incentrata sulla relazione intercorrente tra microstruttura, proprietà funzionali e stabilità: a questo proposito i film sottili sono un materiale ideale, grazie al facile controllo della loro microstruttura in fase di sintesi e alla possibilità di applicarvi diverse tecniche di caratterizzazione complementari. In questa tesi abbiamo dapprima studiamo la relazione tra l'evoluzione del grado di cristallinità, durante i cicli d'idrogenazione, e le proprietà di assorbimento e desorbimento dell'idrogeno da parte di film sottili di magnesio ricoperti da uno strato di palladio; i film sono stati sintetizzati tramite r.f. sputtering su substrati di silicio e vetro. L'uso di diverse tecniche di caratterizzazione complementari fornisce informazioni sulle proprietà strutturali, morfologiche e funzionali. Tramite misure di diffrazione X ad angolo radente vengono seguite le trasformazioni strutturali che si verificano durante il processo di rilascio d'idrogeno, permettendo così di stimare cinetiche migliori e ridotte energie di attivazione, riconducibili alla nanostruttura, rispetto al Mg in fase bulk. La geometria di diffrazione ottimizzata per i film sottili rivela che la tipica tessitura iniziale viene persa dopo il primo ciclo di assorbimento e desorbimento, indicando il manifestarsi di una riorientazione dei cristalliti di magnesio indotta dall'idrogeno. Inoltre quando il magnesio forma l'idruro passa da uno stato metallico ad uno di semiconduttore a grande band gap, mostrando così interessanti proprietà elettriche e ottiche, che vengono studiate tramite spettrofotometria. Il processo reversibile di trasformazione da un metallo con alta riflettanza ad un semiconduttore con alta trasmittanza neutra è promettente nel campo dei ricoprimenti intelligenti e dei sensori d'idrogeno. Particolarmente critici per la stabilità delle proprietà funzionali con i ciclaggi si rivelano l'integrità del layer di palladio e i processi superficiali relativi: il progressivo degrado della copertura di Pd sul film di Mg comporta il rallentamento delle cinetiche fino ad una totale inibizione del processo. I successivi sviluppi di questo lavoro prevedono di considerare strategie atte ad incrementare la stabilità e le cinetiche del film (per esempio, con l'aggiunta di catalizzatori): come primo passo viene studiato il drogaggio del Mg con titanio. Il processo di sintesi di non-equilibrio (sputtering) permette di ottenere un elevato grado di mixing tra questi due elementi altrimenti non miscibili, determinando così per il film peculiari proprietà strutturali, stabili con i ciclaggi. Con l'aumento della concentrazione di Ti in Mg è possibile altresì ottenere delle più rapide cinetiche di assorbimento e desorbimento, grazie al fatto che l'idruro assume una struttura favorevole per il trasporto d'idrogeno. Le trasformazioni strutturali che avvengono durante il processo di desorbimento sono monitorate tramite misure di diffrazione X in-situ e quindi confrontate con misure parallele di trasmittanza ottica, che forniscono una stima della cinetica di rilascio dell'idrogeno. Il miglioramento indotto dal Ti risulta nella decomposizione dell'idruro persino a temperatura ambiente. Il sistema Mg-Ti si è dimostrato piuttosto affascinante e promettente e pertanto sarà soggetto ad ulteriori indagini.
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Hughes, Luke J. R. "Hydrogen sorption properties of magnesium-based thin films." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/7064/.
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Magnesium hydride is a promising material for hydrogen storage. However, the thermodynamic stability of the hydride coupled with slow reaction kinetics means that it is currently infeasible for application as mobile hydrogen storage media. Thin films of magnesium have been investigated to ascertain the influence of stress on the effects of the sorption thermodynamics and kinetics. It was found that: • The intrinsic stress state can be heavily influenced by deposition conditions. • The influence of the underlying microstructure heavily influences hydrogen sorption mechanics. A model has been proposed which shows regimes dominated by porosity, elastic and plastic contributions and their likely effects on sorption thermodynamics. • Stress analysis using different film thicknesses has been used to model the diffusion behaviour within the films, demonstrating how differential rates and directionality of absorption also affect both kinetic and thermodynamic properties of the films. • A novel approach to tailor thin film stress using flexible substrates was used to investigate and tune thermodynamics. The use of an opto-mechanical hydrogen sensor based on this system design. • Y/Mg multilayer systems were investigated for the first time. The characterisation of these shows that hcp/fcc yttrium occurs at different layer thicknesses, altering the lattice spacings at coherent interfaces with Mg.
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Bonelli, Giulio. "Electrochemical loading of hydrogen in Mg thin films." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/22351/.
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The science and technology of hydrogen production from renewable energy, hydrogen sensing and hydrogen storage are central to the realization of a hydrogen-based society, in which me may be living one day.
The focus of my Master thesis will be the solid-state hydrogen storage in nanostructured metallic hydrides. In fact, beside the physical storage of hydrogen through pressurized tanks, it is also possible to store hydrogen in the chemical bonds of the metallic hydrides such as MgH2, LaNi5H6,FeTiH2, just to name a few. The problem is to achieve these goals at temperature and pressure as close as possible to ambient conditions. Knowledge-based design of advanced materials can help to solve issues related to unfavourable kinetics and thermodynamics of hydrogen storage. In particular, size effects and interface engineering in nanomaterials are exciting tools to modify and improving hydrogen sorption properties beyond the current state of the art. This is the subject of the present project.
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Faria, Ana Claudia Rangel. "Preparação e caracterização de filmes finos automontados de polieletrólitos/TiO2/CdSe para aplicação na geração de hidrogênio a partir da fotocatálise da água." reponame:Repositório Institucional da UCS, 2016. https://repositorio.ucs.br/handle/11338/1189.
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Filmes finos automontados (FFA) por adsorção física, compostos por polímeros orgânicos e nanopartículas de semicondutores inorgânicos são considerados um processo barato e não-poluente de deposição, que permite obter filmes com elevada organização molecular. Neste trabalho, o principal objetivo foi produzir e caracterizar FFA, através da técnica camada por camada (LbL), bem como avaliar o potencial de aplicação destes sistemas para a produção de hidrogênio (H2) através da quebra da molécula da água por irradiação solar. Foram depositados três conjuntos diferentes de filmes, onde o sistema catiônico e o número de camadas depositadas (40) foram comuns aos três tipos de FFA. O sistema catiônico foi composto pelas soluções aquosa do policátion hidrocloreto de polialilamina (PAH) e coloidal do semicondutor inorgânico seleneto de cádmio (CdSe). Os sistemas aniônicos foram compostos pelas soluções aquosas do poliânions orgânicos poli(ácido acrílico) (PAA) e poli-(3,4-etilenodioxitiofeno):poli(ácido estirenosulfônico) (PEDOT:PSS) e coloidal do semicondutor fotoativo óxido de titânio (TiO2 P25 e TiO2 STS-100). Análises dos FFA realizadas por perfilometria revelaram que as espessuras dos filmes automontados são da ordem nanométrica. Através do espectro de refletância difusa observou-se bandas de absorção na região do ultravioleta próximo à região do visível e, através da cromatografia, foi determinado a taxa média de produção H2. O sistema com o maior valor da taxa de produção de H2 – (PAH + CdSe)/(PEDOT:PSS + TiO2 STS-100) – foi otimizado em 120 camadas. Na avaliação da contribuição do tipo de nanopartícula do semicondutor para a geração de H2, os resultados de cromatografia indicaram que a combinação de (CdSe + TiO2 STS-100) promove um aumento de 75% desta geração quando comparado ao FFA composto somente pelo semicondutor TiO2 STS-100.Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2016-06-27T17:24:19Z No. of bitstreams: 1 Tese Ana Claudia Rangel Faria.pdf: 3615547 bytes, checksum: dd46f2460a25e8f792251379d3c801a6 (MD5)
Made available in DSpace on 2016-06-27T17:24:19Z (GMT). No. of bitstreams: 1 Tese Ana Claudia Rangel Faria.pdf: 3615547 bytes, checksum: dd46f2460a25e8f792251379d3c801a6 (MD5) Previous issue date: 2016-06-27
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES.
The self-assembled films (SAF) by physical adsorption, compounds of organic polyelectrolytes and inorganic semiconductor nanoparticles are considered an inexpensive process and non-pollutant deposition that gives films with high molecular organization. The aim of this work was to fabricate and characterize SAF via the layerby- layer technique (LbL) and evaluate the potential application of these systems to produce hydrogen (H2) by water splitting technique by solar radiation. In this work were deposited three different sets of films. The cationic system and the number of deposited layers (40) are common to all three types of SAF. The system was composed by the cationic aqueous solution of polycation polyallylamine hydrochloride (PAH), and colloidal inorganic semiconductor cadmium selenide (CdSe). The anionic systems were comprised of aqueous solutions of organic polyanions poly(acrylic acid) (PAA) and poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT: PSS) and colloidal photoactive semiconductor titanium oxide (TiO2 P25 and TiO2 STS-100). Analysis of SAF by profilometry revealed that the thickness of the self-assembled films are of nanometer order; by diffuse reflectance spectrum observed absorption bands in the near ultraviolet region and the visible region and through the chromatography was given the average H2 production. The system with the highest value of H2 production rate - (PAH + CdSe) / (PEDOT: PSS + TiO2 STS-100) - was optimized at 120 layers. In the evaluation of the contribution of the type semiconductor nanoparticle for the generation of H2 results chromatography indicated that the combination of (CdSe + TiO2 STS-100) promotes an increase of 75% from this generation as compared to SAF only composed by the semiconductor TiO2 STS -100.
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Dal', Acqua Nicolle. "Produção fotocatalítica de hidrogênio a partir de filmes finos poliméricos nanoestruturados suportados em substrato flexível." reponame:Repositório Institucional da UCS, 2017. https://repositorio.ucs.br/handle/11338/2486.
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O uso de energias renováveis como a energia solar para a produção de gás hidrogênio (H2), por meio do processo fotocatalítico da quebra da molécula de água, é uma alternativa promissora às fontes de energias convencionais. Neste contexto, a produção de filmes finos nanoestruturados de diferentes materiais é uma aplicação que pode aliar a fotocatálise e a nanotecnologia. Assim, o principal objetivo deste trabalho foi avaliar o efeito de diferentes concentrações de ácido tetracloroaurico (HAuCl4) para incorporação de nanopartículas de ouro (NPs Au) na produção de H2, a partir de filmes finos suportados em celulose bacteriana (CB), produzidos através da técnica camada por camada utilizando os polieletrólitos fracos, hidrocloreto de polialilamina (PAH) e poli(ácido acrílico) (PAA), combinados com dióxido de titânio (TiO2). Por meio das técnicas de espectroscopia de absorção molecular na região do ultravioleta e visível (UV-Vis), difração de raios X (DRX), microscopia eletrônica de varredura (MEV) e espectroscopia de infravermelho foi possível verificar a absorção da CB na região do UV, os picos em 14,6º, 16,6º e 22,6º, a superfície constituída de fibras e as bandas características da CB, respectivamente. A área superficial específica de 1,57 m2 g-1 foi encontrada para a CB. A absorção na região do UV das soluções de HAuCl4 e TiO2 foram determinadas por UV-Vis. Através da técnica de DRX, calculou-se o tamanho médio do cristalito do TiO2 que foi de ~5 nm corroborando com a microscopia eletrônica de transmissão (MET). O TiO2 também foi caracterizado por fluorescência molecular, MEV e área superficial específica. O potencial zeta foi utilizado para analisar as soluções poliméricas (PAH e PAA) e a solução de TiO2. Os filmes de diferentes concentrações de HAuCl4 (1,25 mmol L-1, 2,5 mmol L-1 e 5 mmol L-1) e com diferentes tempos de luz UV (6h, 12h, 24h, 24h, 48h e 96h) foram analisados por cromatografia gasosa (CG). Destes filmes, os que mais produziram H2 em cada concentração de HAuCl4 (c1-24 / concentração de 1,25 mmol L-1 e 24h de luz UV), (c2- 6 / concentração de 2,5 mmol L-1 e 6h de luz UV) e (c3-24 / concentração de 5 mmol L-1 e 24h de luz UV), foram caracterizados antes e depois da fotocatálise. Através do UV-Vis, foi possível observar a presença de NPs Au e TiO2 nos filmes. Por DRX, notou-se os picos da CB, do TiO2 (25,3º) e do Au (38,18º e 44,5º) nos filmes. No MEV foi possível observar que o filme (c1-24) possuia grãos de Au dispersos na matriz e a presença de Ti em toda a superfície sem aglomerações, revelando-se como um filme homogêneo comparado aos filmes (c2-6) e (c3-24). Pela técnica de MET, analisou-se a morfologia, tamanho e distribuição das NPs Au nos filmes revelando valores em escala manométrica. O filme (c1-24) apresentou menores tamanhos de NPs Au (9 nm). Área superficial específica, perfilometria, Espectroscopia de Emissão Óptica de Descarga Luminescente e Espectrometria de emissão óptica com plasma também foram analisados para avaliar o efeito das concentrações e tamanhos de NPs Au nos filmes. O filme com menor concentração de HAuCl4 (c1-24), o qual tinha NPs Au menores que em maior contato com a superfície do TiO2 produziu mais H2, foi analisado por CG para aperfeiçoar o melhor desempenho na produção de H2 variando alguns parâmetros como reutilização do filme (c1-24a) e (c1-24b), alteração de substrato (c1-24d), aumento de camadas (c1-24f) e filme sem polímeros (c1-24g). Analisando todas as variações dos parâmetros foi concluído que o filme (c1-24) produziu 29,12 μmol h-1cm2 de H2 apresentando uma melhor atividade fotocatalítica.Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2017-05-10T16:47:00Z No. of bitstreams: 1 Tese Nicolle Dal Acqua.pdf: 2359937 bytes, checksum: 79a564bfa513c80ed882f203002fc4ca (MD5)
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The use of renewable energy such as solar energy to produce hydrogen gas (H2), through the photocatalytic process of breaking the water molecule, is a promising alternative to conventional energy sources. In this context, the production of nanostructured thin films of different materials is an application that can combine photocatalysis and nanotechnology.Thus, the main objective of this work was to evaluate the effect of different concentrations of tetrachlorouric acid (HAuCl4) for the incorporation of gold nanoparticles (Au NPs) in H2 production from thin films supported on bacterial cellulose (BC), produced through of the technique layer by layer using the weak polyelectrolytes, polyallylamine hydrochloride (PAH) and polyacrylic acid (PAA) combined with titanium dioxide (TiO2). Through the techniques of molecular absorption spectroscopy in the ultraviolet and visible (UV-Vis), X-ray diffraction (XRD), scanning electron microscopy (SEM) and infrared spectroscopy (FTIR), it was possible to verify the absorption of BC in the UV region, the peaks at 14.6º, 16.6º and 22.6º, the fiber surface and the characteristic bands of BC, respectively. The specific surface area of 1.57 m2 g-1 was found for CB. Absorption in the UV region of the HAuCl4 and TiO2 solutions were determined by UV-Vis. By means of the XRD technique, the average crystallite size of the TiO2 was calculated which was ~5 nm corroborating with transmission electron microscopy (TEM). TiO2 was also characterized by molecular fluorescence, SEM and specific surface area. The zeta potential was used to analyze the polymer solutions (PAH and PAA) and the TiO 2 solution. The films with different concentrations of HAuCl4 (1.25 mmol L-1, 2.5 mmol L-1 and 5 mmol L-1) and with different UV light times (6h, 12h, 24h, 24h, 48h and 96h) were analyzed by gas chromatography (GC). Of these films, the ones that most produced H2 at each concentration of HAuCl4 (c1-24 / concentration of 1.25 mmol L-1 and 24h of UV light), (c2-6 / concentration of 2.5 mmol L-1 and 6h of UV light) and (c3-24 / concentration of 5 mmol L-1 and 24h of UV light) were characterized before and after photocatalysis. Through the UV-Vis, it was possible to observe the presence of Au and TiO2 NPs in the films. By XRD, the peaks were noted of CB, TiO2 (25.3 °) and Au (38.18 ° and 44.5 °) in the films. In the SEM it was observed that the film (c1-24) had Au grains dispersed in the matrix and the presence of Ti on the whole surface without agglomerations, revealing as a homogeneous film compared to the films (c2-6) and (c3-24). Using the MET technique, the morphology, size and distribution of Au NPs were analyzed in the films revealing values in manometric scale. The film (c1-24) presented smaller sizes of Au NPs (9 nm). Specific surface area, perfilometry, Glow-discharge optical emission spectroscopy (GD-OES) and inductively coupled plasma (ICP-OES) were also analyzed to evaluate the effect of concentrations and sizes of Au NPs in the films.The film with lower concentration of HAuCl4 (c1-24), which had Au NPs less than in greater contact with the surface of TiO2 produced more H2, was analyzed by CG to improve the best performance in H2 production varying some parameters as reuse of the film (c1-24a) and (c1-24b), substrate change (c1-24d), increase of layers (c1-24f) and film without polymers (c1-24g). Analyzing all the variations of the parameters it was concluded that the film (c1-24) produced 29.12 μmol h-1 cm2 of H2 presenting a better photocatalytic activity.
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Li, Mengxing. "Films minces d'hydrogels stimulables." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066268/document.
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Les films minces d'hydrogels que nous étudions sont des réseaux chimiques de polymères greffés par liaison covalente sur des substrats solides. Ces revêtements versatiles permettent le contrôle des propriétés interfaciales tel que les propriétés stimulables, le mouillage ou les propriétés mécaniques. Ici, nous nous intéressons aux films minces d'hydrogels stimulables (par la température, la lumière ou le champ électrique).La synthèse des films de gels greffés suit une stratégie simple basée sur la chimie click thiol-ène. Les films sont fabriqués en déposant les polymères stimulables fonctionnalisés par des groupes diène en présence de réticulants dithiols sur des surfaces modifiées thiol. Cette stratégie permet d'obtenir des films d'hydrogels sur une large gamme d'épaisseur avec les propriétés stimulables visées. Nous nous intéressons à la structure des films d'hydrogels greffés de poly(N-isopropylacrylamide) aux propriétés thermo-stimulables. Nous étudions l'effet du confinement et des contraintes dues au greffage sur la surface sur la transition de phase gonflement/dégonflement des gels avec deux approches : le gonflement unilatéral (perpendiculaire à la surface) par ellipsométrie et réflectivité de neutrons, et la topographie (dans le plan) de la surface libre du gel par AFM. Nous développons également de nouveaux films d'hydrogels avec des réseaux d'architectures ciblées. En s'inspirant de l'architecture des gels macroscopiques, nous élaborons diverses architectures : films de gels multicouches, films de réseaux interpénétrés et films de gels hybridesThin films of hydrogels we study are chemical polymer networks covalently grafted on solid substrates. These versatile coatings allow the control of various interfacial properties such as responsive properties, wetting or mechanical properties. Here, thin films of stimuli-responsive hydrogels (with temperature, light or electric field) are the point of interest. The surface-attached gel films are synthesized by following a straightforward strategy based on thiol-ene click chemistry. The formation of the films is achieved by adding bifunctional thiol molecules as cross-linkers to the ene-reactive polymers on thiol-modified surfaces. This strategy allows us to obtain hydrogel films with a wide range of thickness and with the desired properties. We study the structure of surface-attached poly(N-isopropylacrylamide) gel films which show thermo-responsive properties. We determine the effect of confinement and constraints due to the surface-attachment on the swelling/collapse phase transition of hydrogels with two approaches: the one-dimension swelling normal to the surface using ellipsometry and neutron reflectivity and the in-plane observation of the free surface of the gel using AFM. New and complex hydrogel films are also developed by targeting the architecture of the polymer networks. Inspired from macroscopic hydrogels architecture, we design various architectures: multilayer gel films, interpenetrating networks (IPN) gel films and hybrid gel films
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Akyildiz, Hasan. "Hydrogen Storage In Magnesium Based Thin Film." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612652/index.pdf.
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ABSTRACT
HYDROGEN STORAGE IN MAGNESIUM BASED
THIN FILMS
Akyildiz, Hasan
Ph.D., Department of Metallurgical and Materials Engineering
Supervisor : Prof. Dr. Tayfur Öztü
rk Co-Supervisor : Prof. Dr. Macit Ö
zenbas October 2010, 146 pages A study was carried out for the production of Mg-based thin films which can absorb and desorb hydrogen near ambient conditions, with fast kinetics. For this purpose, two deposition units were constructed
one high vacuum (HV) and the other ultra high vacuum (UHV) deposition system. The HV system was based on a pyrex bell jar and had two independent evaporation sources. The unit was used to deposit films of Mg, Mg capped with Pd and Au-Pd as well as Mg-Cu both in co-deposited and multilayered form within a thickness range of 0.4 to 1.5 &mu
m. The films were crystalline with columnar grains having some degree of preferred orientation. In terms of hydrogen storage properties, Mg/Pd system yielded the most favorable results. These films could desorb hydrogen at temperatures not greater than 473 K. The study on crystalline thin films has further shown that there is a narrow temperature window for useful hydrogenation of thin films, the upper limit of which is determined by the intermetallic formation. The UHV deposition system had four independent evaporation sources and incorporated substrate cooling by circulating cooled nitrogen gas through the substrate holder. Thin films of Mg-Cu were produced in this unit via co-evaporation technique to provide concentrations of 5, 10 and 15 at. % Cu. The films were 250-300 nm thick, capped with a thin layer of Pd, i.e. 5-25 nm. The deposition was yielded nanocrystalline or amorphous Mg-Cu thin films depending on the substrate temperature. At 298 K, the films were crystalline, the structure being refined with the increase in Cu content. At 223 K, the films were amorphous, except for Mg:Cu=95:5. The hydrogen sorption of the films was followed by resistance measurements, with the samples heated isochronally, initially under hydrogen and then under vacuum. The resistance data have shown that hydrogen sorption behaviour of thin films was improved by size refinement, and further by amorphization. Among the films deposited, amorphous Mg:Cu=85:15 alloy could absorb hydrogen at room temperature and could desorb it at 223 K (50 º
C), with fast kinetics.
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Sporar, Daniel. "Sputter Deposition of Iron Oxide and Tin Oxide Based Films and the Fabrication of Metal Alloy Based Electrodes for Solar Hydrogen Production." Connect to Online Resource-OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=toledo1183481021.
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Thesis (M.S.Ch.E.)--University of Toledo, 2007.Typescript. "Submitted as partial fulfillment of the requirements for The Master of Science degree in Chemical Engineering." Bibliography: leaves 72-77.
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Sorrell, Courtney Davis. "Fundamental studies of responsive microgel thin films at interfaces." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24679.
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Thesis (Ph.D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009.Committee Chair: Lyon, L. Andrew; Committee Member: Beckham, Haskell; Committee Member: Janata, Jiri; Committee Member: Pielak, Gary; Committee Member: Ragauskas, Arthur
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Gharemeshg, Gharavi Ayshe. "Thickness Effects In Hydrogen Sorption Of Magnesium/palladium Thin Films." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614051/index.pdf.
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Magnesium (Mg) thin films with various thicknesses ranging from 50 to 1000 nm capped with nominally 20 nm Palladium (Pd) were prepared by a thermal evaporation unit. A total of 25 glass substrates were used in each experiment. The unit had a rotatable macro shutter, rectangular in shape, rotation axes opposite to the Mg source, which allowed controlled exposure of the substrates. Thin films of 50, 100, 150, 200, 300, 400, 500, 600, 800 nm and 1000 nm were produced in a single experiment. Hydrogenation and dehydrogenation of the films were examined using a gas loading chamber which allowed in-situ resistance measurement. Samples were hydrogenated isochronally up to 453 K with a heating rate of 1.5 K/min. Samples cooled to room temperature were subjected to dehydrogenation test. The chamber was taken under vacuum (~10-2 mbar) and the sample was heated up to 453 K at a rate of 1.5 K/min. The results showed that the hydrogenation and dehydrogenation temperatures correlate with the film thickness, thinner films reacting with hydrogen at low temperatures. While 200 nm thin film hydrogenated at 420 K and desorbed it at 423 K, 50 nm thin film hydrogenated at room temperature and desorbed it at 405 K. Thicker films needed higher temperatures to react with hydrogen. It is concluded that films thinner than 200 nm react fully with hydrogenwhile a considerable portion of the thicker films remain unreacted. Significance of this is discussed with reference to the design of hydrogen storage systems based on thin films or nanoparticles.
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Ukirde, Vaishali. "Evaluation of hydrogen trapping in HfO2 high-κ dielectric thin films." Thesis, University of North Texas, 2006. https://digital.library.unt.edu/ark:/67531/metadc5596/.
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Hafnium based high-κ dielectrics are considered potential candidates to replace SiO2 or SiON as the gate dielectric in complementary metal oxide semiconductor (CMOS) devices. Hydrogen is one of the most significant elements in semiconductor technology because of its pervasiveness in various deposition and optimization processes of electronic structures. Therefore, it is important to understand the properties and behavior of hydrogen in semiconductors with the final aim of controlling and using hydrogen to improve electronic performance of electronic structures. Trap transformations under annealing treatments in hydrogen ambient normally involve passivation of traps at thermal SiO2/Si interfaces by hydrogen. High-κ dielectric films are believed to exhibit significantly higher charge trapping affinity than SiO2. In this thesis, study of hydrogen trapping in alternate gate dielectric candidates such as HfO2 during annealing in hydrogen ambient is presented. Rutherford backscattering spectroscopy (RBS), elastic recoil detection analysis (ERDA) and nuclear reaction analysis (NRA) were used to characterize these thin dielectric materials. It was demonstrated that hydrogen trapping in bulk HfO2 is significantly reduced for pre-oxidized HfO2 prior to forming gas anneals. This strong dependence on oxygen pre-processing is believed to be due to oxygen vacancies/deficiencies and hydrogen-carbon impurity complexes that originate from organic precursors used in chemical vapor depositions (CVD) of these dielectrics.
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Fletcher, Sean. "Thin film Palladium-Ytrium membranes for hydrogen separation." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/924/.
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The permeability of hydrogen in thin film Pd-Y composite membranes has been investigated for the first time. Thin (5 µm) Pd-Y films were deposited onto macroporous 316L stainless steel substrates by magnetron sputtering. Prior to deposition, a novel laser melting technique was employed in an attempt to reduce the surface roughness and pore size, thus facilitating the deposition of defect-free films. The active hydrogen transport mechanisms of each layer have been determined and the observed hydrogen permeability was analysed using a series resistance type model. The porous substrate was found to contribute significantly to the total transport resistance, and was the predominant source of the non diffusion limited permeation. After correcting for the substrate effects, the permeability of thin film Pd-Y closely matched that in bulk Pd-Y alloys.
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Ozgit, Cagla. "Isochronal Hydrogenation Of Textured Magnesium/palladium Thin Films." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610385/index.pdf.
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Pure and palladium‐
covered 350 nm thick magnesium thin films were deposited on glass substrates via thermal evaporation. In the as&
#8208
deposited state, films were highly textured with Mg (001) parallel to the substrate. Hydrogen loading experiments were carried out in two different conditions
namely isothermal and isochronal. Hydrogenation behaviors of the thin films were followed by twopoint probe electrical resistance and optical transmittance measurements, as well as x&
#8208
ray diffraction studies. Isothermal hydrogenation experiments conducted on Pd&
#8208
covered Mg thin films have revealed that these films can absorb hydrogen at temperatures starting from 333 K, producing MgH2 with a random texture. When the films were heated slowly starting from the room temperature, on the other hand, hydrogenation gives rise to a textured MgH2, where (110) parallel to the substrate with a minor (101) component. Formation of the textured hydride in isochronal loading was discussed within the context of lattice mismatch in Mg to MgH2 transformation. It was further shown that formation of such a textured hydride in Mg thin films minimizes in&
#8208
plane lattice distortion.
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Piskin, Fatih. "Deposition And Testing Of Thin Film Hydrogen Separation Membranes." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615550/index.pdf.
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Industrial production of hydrogen from the syngas, generated from steam reformation of natural gas or coal gasification, sets conditions for hydrogen separation membranes in terms of operating conditions. An alternative source for hydrogen is a syngas generated by gasification of municipal solid wastes which are likely to set more stringent conditions for the separation membranes. There is therefore, a growing demand for separation membranes with improved permeability and particularly of low cost. Among various alternatives, metallic membranes are particularly attractive due to their high selectivity and permeability for hydrogen, exemplified by palladium (Pd). However, due to high cost of Pd there is still a demand to develop alternative metallic membranes that are of low cost and have improved durability. Efforts have therefore concentrated on either alloying Pd so as to reduce its cost or on alternative membrane compositions of particularly b.c.c. structure.
The current study deals with hydrogen separation membranes and aims to develop infrastructure for rapid identification of membrane compositions with improved permeability. The study is made up of three partsi) development of sputter deposition system that would allow deposition of multiple compositions in a single experiment, ii) development of substrate material that would support the thin film membranes and would allow permeability measurement and iii) development of a set-up to measure the permeability of the thin film membranes. In the present thesis, a sputter deposition system incorporating three targets was successfully constructed. The system as tested with palladium-niobium-titanium (Pd-Nb-Ti) ternary system after necessary adjustment would yield thin films of homogenous thickness (&le
7%) over a sample area of &asymp
150 mm diameter. A total of 21 substrates each in 19 mm diameter arranged in triangular form in the substrate holder could successfully be deposited where composition distributions covered a greater portion of Pd-Nb-Ti ternary phase diagram. The structure of the deposited thin films can successfully be controlled by substrate temperature as well as by the pressure of plasma gas (argon). With the help of these parameters, structural diversity can also be produced beside the compositional variation. As for substrates, two materials were investigated. These were titanium dioxide (TiO2) modified porous stainless steel (PSS) and anodic porous alumina (AAO). TiO2 modified PSS due to its associated surface roughness leads to the deposition of films with defected structure which as a result is not gas tight. AAO produced via anodization of aluminum foil had a regular (40-60 nm) pore structure that provides a suitable surface for thin film depositions which could be defect free. However, AAO is very delicate and fragile which makes it difficult to adapt it as a support material for permeability measurement/hydrogen separation purposes. Finally, a set-up was developed for measurement of hydrogen permeability which is capable of measurement over a wide pressure and temperature conditions, i.e. hydrogen pressures up to 10 bar and temperature as high as 450 °
C. It is recommended that so as to identify compositions with improved permeability, Nb or a similar metal which has extremely high permeability could be used as a support material. This would tolerate the evaluation of the films which are not totally defect free.
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Montero, Suárez Laura. "Tailoring Surfaces to improve Biomaterials performance: piCVD & iCVD approaches." Doctoral thesis, Universitat Ramon Llull, 2012. http://hdl.handle.net/10803/84178.
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S’han dipositat capes primes d’hidrogel per tal de modificar les propietats superficials i millorar el comportament dels biomaterials. Dues de les tècniques de deposició química en fase vapor més comunes s’han estudiat per poder dur a terme aquestes modificacions. La deposició química foto-iniciada en fase vapor (piCVD) és un mètode simple, ràpid i no agressiu que permet depositari films d’hidrogel. És un mètode que s’inicia a la superfície de la mostra i que permet recobrir de manera homogènia superfícies tridimensionals com és el cas de les micro-partícules. El piCVD ofereix un ventall molt ampli d’hidrogels amb capacitat d’absorbir aigua, incorporant co-monòmers amb diferents propietats. Els hidrogels poden ser dissenyats perquè la reactivitat es localitzi a nivell superficial, millorant d’aquesta manera la funcionalització química dels hidrogels. Tanmateix, un nou mètode s’ha utilitzat per micro-estructurar les superfícies durant la deposició via piCVD per obtenir hidrogels amb comportaments especials.
Els hidrogels termo-sensibles s’han obtingut via deposició química iniciada en fase vapor (iCVD). S’ha desenvolupat una llibreria d’hidrogels termo-sensibles, els quals exhibeixen una temperatura de transició molt marcada. La microbalança de quars amb dissipació (QCM-D) s’ha fet servir per analitzar la transició d’aquests films. La combinació de les propietats que ofereixen els films termo-sensibles dona la possibilitat de dissenyar una plataforma per prevenir la formació de biofilms.Se han depositado capas delgadas de hidrogel para lamodificación superficial y mejora del comportamiento de los biomateriales. Dos de las técnicasmás comunes de deposición química en fase vapor se han estudiado para llevar a cabo estas modificaciones. La deposición química foto-iniciada en fase vapor (piCVD) es un método simple, rápido y no agresivo que permite depositar films de hidrogel. Es un método que se inicia en la superficie de la muestra y que permite recubrir de manera homogénea superficies tridimensionales como es el caso de las micro-partículas. El piCVD ofrece un abanico muy amplio de hidrogeles con capacidad de absorber agua, incorporando co-monomeros con diferentes propiedades. Los hidrogeles se pueden diseñar para que la reactividad se localice a nivel superficial, mejorando de esta manera la funcionalización química de los hidrogeles. Así mismo, un nuevo método se ha utilizado para micro-estructurar las superficies durante la deposición vía piCVD para obtener hidrogeles con comportamientos especiales. Los hidrogeles termo-sensibles se han obtenido vía deposición química iniciada en fase vapor (iCVD). Se ha desarrollado una librería de hidrogeles termo-sensibles, los cuales exhiben una temperatura de transición muy marcada. La microbalanza de cuarzo con disipación (QCM-D) se ha utilizado para analizar la transición de este film. La combinación de las propiedades que ofrecen los films termo-sensibles da la posibilidad de diseñar una plataforma para prevenir la formación de biofilms.
Thin hydrogel films have been deposited to modify surface properties and improve biomaterials performance. Two of the most common chemical vapor deposition techniques have been studied to carry out these modifications. Photo-initiated chemical vapor deposition piCVD has been developed as a simple, not aggressive and easy method for the deposition of thin hydrogel films. This method follows a versatile surface-driven reaction process that allows homogeneous coating of both 2D and 3D geometries, such as microspheres. piCVD offers the possibility to fabricate a wide range of swellable thin films, incorporating co-monomers with different properties, such as amine-reactivity, suitable for further modification. The hydrogels can be designed by nano-confining the reactivity to the near surface region, improving the chemical functionality of hydrogels. In addition, a new method to create micro-patterned surfaces can be applied during piCVD deposition to design surfaces having special behavior. Thermo-responsive thin hydrogel films have also been obtained via initiated chemical vapor deposition (iCVD). A library of thermo-sensitive films exhibiting controlled lower critical solution temperatures (LCST) has been generated. Quartz crystal microbalance with dissipation analysis has been used to analyze the phase-transition of these films. The intrinsic properties of thermo-sensitive hydrogels, such as tunable surface hydrophilicity or release of film-entrapped molecules, open the possibility to design systems for controlling biofilm formation.
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Prinz, Jan. "Hydrogen in thin metal films as seen by electron and light scattering." Thesis, Uppsala universitet, Materialfysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-132061.
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Schulz, Meghan E. "Nitrogen- and carbon-doped titanium dioxide thin films for solar hydrogen generation." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 95 p, 2009. http://proquest.umi.com/pqdweb?did=1896914051&sid=4&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Ukirde, Vaishali El Bouanani Mohamed. "Trapping of hydrogen in Hf-based high [kappa] dielectric thin films for advanced CMOS applications." [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-5114.
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Backholm, Jonas. "Electrochromic Properties of Iridium Oxide Based Thin Films." Doctoral thesis, Uppsala universitet, Fasta tillståndets fysik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8505.
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Electrochromic iridium oxide (IrOx) and iridium-tantalum oxide (IrTaOx) thin films were prepared by reactive magnetron sputtering. Composition, density, and structure were determined using Rutherford backscattering spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and electron energy loss spectroscopy. The electronic density of states (DOS) and the solid phase chemical diffusion coefficient (D) were determined for hydrogen in IrOx and IrTaOx by potentiostatic intermittent titration technique (PITT), and electrochemical impedance spectroscopy (EIS). The complex refractive indices were determined for colored and bleached IrOx and IrTaOx by inverting transmission and reflectance, measured using spectrophotometry in the 300-2500 nm wavelength range. A very porous structure, with a stoichiometry of IrO2.2, was found for IrOx. It contained ~4 nm sized grains. The IrTaOx had a denser structure built up by ~4 nm sized grains. The composition of IrTaOx was found to vary on a nanometer scale, with an average composition of IrTa1.4O5.6. It was found that DOS can be measured using PITT and EIS in the presence of spontaneous side reactions, even for systems influenced by non-negligible charge transfer kinetics and Ohmic drops. It was found that the measured DOS is 30-50% of the theoretically calculated DOS and that D is in the 10-10 – 10-11 cm2/s range for both materials. The hydrogen diffusion mechanism was described by an anomalous diffusion model, possibly indicating percolation or diffusion paths described by a fractal network. The refractive indices were found to be ~1.3 and ~2 for IrOx and IrTaOx, respectively, and independent of coloration state, whereas the extinction coefficients were found to modulate by ~30% for IrOx and ~50% for IrTaOx, making IrTaOx more favorable for electrochromic applications. A modulation peak was found at ~660 nm for both IrOx and IrTaOx associated with the removal of intraband transitions within the Ir t2g band.
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Tuckute, S., and L. L. Pranevicius. "Separation of Hydrogen from Water Molecules by Ion Implantation into Thin Ti Films." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35410.
Full textAbstract:
The potential of hydrogen as primary gas source has generated considerable interest in hydrogen separation
technologies. In the present work, the method of ion implantation has been used to separate hydrogen
from energetic water molecules penetrating into Ti films. According to the results of the present study,
the technique and method of implantation are capable of splitting water molecular ions into their constituent
atoms with accommodation of oxygen and hydrogen atoms in interstitials of Ti film.
The experimental distribution profiles are fitted with the simulated results based on the analysis of solutions
of rate equations including processes of molecular ion implantation and diffusion. The dominant
mechanisms transporting incident particles from the surface into the bulk are discussed. The obtained results
are compared to literature data on the widely studied titanium–hydrogen bulk system. The experimental
and simulation results are in consistency that molecular ions upon entering the substrate break up
into constituent atoms and separation of hydrogen occurs.
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Li, Chi Ying Vanessa Materials Science & Engineering Faculty of Science UNSW. "Study of hydrogen storage and electrochemical properties of LANI5-based thin films and porous silicon thin films for mini-fuel cells and micro-batteries." Awarded by:University of New South Wales. Materials Science & Engineering, 2008. http://handle.unsw.edu.au/1959.4/43303.
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Two thin film materials - intermetallic and porous silicon thin films, have been studied in this thesis. The first part focuses on the hydrogen storage and electrochemical properties of single layer LaNi5-based thin films fabricated by magnetron sputtering. The aim is to enhance their performance in mini hydrogen storage systems, and their application as electrodes in thin film Ni-MH micro-batteries. Such LaNi5-based thin films were fabricated by magnetron puttering. Using X-ray diffraction (XRD), these thin films revealed a crystalline structure with uniform chemical composition. Using AFM, SEM and TEM, they were found to have a unique microstructure: (1) Nanopores of approximately 15-40 nm which could possibly act as hydrogen reservoir (2) A dense, defect free cross sectional region which would ultimately improve the efficiency and lifetime of the thin film electrodes used in thin film battery. The hydrogen absorption/desorption behaviour of these thin films were determined by volumetric method. The maximum hydrogen content of the La-Ni-A1 film was found to be 1.45 wt% at 333 K which was very close to the theoretical capacity of 1.47 wt%; and higher than that of the La-Ni-AI powder materials (1.2 wt%). Electrochemical properties of the films were measured by simulated battery tests. When discharged at low current, the discharge capacity of the film was similar to that of powder materials - about 220 mAh/g for the first 30 cycles. When the thin film electrode was discharged at a high rate, 4C (current density of 100 mA/g), it could reach the maximum specific capacity of 200 mAh/g and maintained this capacity for 200 cycles; the value was not attainable for La-Ni-AI powder electrode. The presence of crack propagation in film during charge/discharge cycles would improve the electrochemical performance which was different to that of powder materials. Cyclic voltammetry reported that the efficiency of the film could maintain at 80% for the first 200 cycles and gradually decreased due to the formation of corrosion products on surface, which is consistent with the galvanostatic results. XPS (X-ray Photoelectron Spectroscopy) revealed that the corrosion products ??? A1203, La203 and La(OH)3 formed on the film surface after cyclic voltammetry. The second part reported the hydrogen absorption/desorption behaviour of porous silicon thin films. The hydrogen content was determined quantitatively by both volumetric method and thermogravimetric analysis (TGA) and found to be 15 wt% at 423 K under 15 atm of hydrogen pressure. This is an extraordinary amount of hydrogen absorption which supersedes the US Department of Energy's 2007 target of 6.5 wt%. Hydrogen depth profiles of the film after hydrogenation performed by Secondary Ion Mass Spectroscopy confirmed there was hydrogen within the film structure, this was an indication that hydrogen was not just physisorbed on the film surface, but chemisorbed into the porous Si lattice. X-ray diffraction found that there was a lattice contraction upon hydrogen insertion, again suggesting the hydrogen entered into the film structure by chemisorption.
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Li, Mengxing. "Films minces d'hydrogels stimulables." Electronic Thesis or Diss., Paris 6, 2014. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2014PA066268.pdf.
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Les films minces d'hydrogels que nous étudions sont des réseaux chimiques de polymères greffés par liaison covalente sur des substrats solides. Ces revêtements versatiles permettent le contrôle des propriétés interfaciales tel que les propriétés stimulables, le mouillage ou les propriétés mécaniques. Ici, nous nous intéressons aux films minces d'hydrogels stimulables (par la température, la lumière ou le champ électrique).La synthèse des films de gels greffés suit une stratégie simple basée sur la chimie click thiol-ène. Les films sont fabriqués en déposant les polymères stimulables fonctionnalisés par des groupes diène en présence de réticulants dithiols sur des surfaces modifiées thiol. Cette stratégie permet d'obtenir des films d'hydrogels sur une large gamme d'épaisseur avec les propriétés stimulables visées. Nous nous intéressons à la structure des films d'hydrogels greffés de poly(N-isopropylacrylamide) aux propriétés thermo-stimulables. Nous étudions l'effet du confinement et des contraintes dues au greffage sur la surface sur la transition de phase gonflement/dégonflement des gels avec deux approches : le gonflement unilatéral (perpendiculaire à la surface) par ellipsométrie et réflectivité de neutrons, et la topographie (dans le plan) de la surface libre du gel par AFM. Nous développons également de nouveaux films d'hydrogels avec des réseaux d'architectures ciblées. En s'inspirant de l'architecture des gels macroscopiques, nous élaborons diverses architectures : films de gels multicouches, films de réseaux interpénétrés et films de gels hybridesThin films of hydrogels we study are chemical polymer networks covalently grafted on solid substrates. These versatile coatings allow the control of various interfacial properties such as responsive properties, wetting or mechanical properties. Here, thin films of stimuli-responsive hydrogels (with temperature, light or electric field) are the point of interest. The surface-attached gel films are synthesized by following a straightforward strategy based on thiol-ene click chemistry. The formation of the films is achieved by adding bifunctional thiol molecules as cross-linkers to the ene-reactive polymers on thiol-modified surfaces. This strategy allows us to obtain hydrogel films with a wide range of thickness and with the desired properties. We study the structure of surface-attached poly(N-isopropylacrylamide) gel films which show thermo-responsive properties. We determine the effect of confinement and constraints due to the surface-attachment on the swelling/collapse phase transition of hydrogels with two approaches: the one-dimension swelling normal to the surface using ellipsometry and neutron reflectivity and the in-plane observation of the free surface of the gel using AFM. New and complex hydrogel films are also developed by targeting the architecture of the polymer networks. Inspired from macroscopic hydrogels architecture, we design various architectures: multilayer gel films, interpenetrating networks (IPN) gel films and hybrid gel films
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Dorenkamp, Yvonne Jeannette. "Inelastic H-Atom scattering from ultra-thin films." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2018. http://hdl.handle.net/11858/00-1735-0000-002E-E49B-7.
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Yarahmadi, Sina. "Preparation and performance of nanostructured iron oxide thin films for solar hydrogen generation." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/8131.
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Nowadays, energy and its resources are of prime importance at the global level. During the last few decades there have been several driving forces for the investigation of new sources of energy. Hydrogen has long been identified as one of the most promising carriers of energy. Photoelectrochemical (PEC) water splitting is one of the most promising means of producing hydrogen through a renewable source. Hematite (α-Fe2O3) is a strong candidate material as photoelectrode for PEC water splitting as it fulfils most of the selection criteria of a suitable photocatalyst material for hydrogen generation such as bandgap, chemical and photelectrochemical stability, and importantly ease of fabrication. This work has explored different preparation techniques for undoped and Si-doped iron oxide thin films using microwave-assisted and conventional preparation methods. Two distinct strategies towards improving PEC performance of hematite photoelectrodes were examined: retaining a finer nanostructure and enhancing the photocatalytic behaviour through doping. By depositing thin films using atmospheric pressure chemical vapour deposition (APCVD) and aerosol-assisted CVD (AACVD) at high temperature, it was shown that a combination of different factors (such as silicon incorporation into the hematite structure and formation of lattice defects, along with a nanostructure of small agglomerate/cluster enhancing hole transportation to the surface) were the contributing factors in improving the PEC performance in hematite films. The role of the Si-containing precursors and their consecutive effect on nanostructure of the hematite films were investigated. Further work is needed to study the decomposition pattern of precursors and consequent effects of Si additives as well as co-dopants on fundamental physical and electrical properties of hematite electrodes. In addition, the feasibility of using microwave annealing for the fabrication of iron oxide thin films prepared by electrodeposition at low temperature was also investigated. Hematite films showed improved PEC performance when microwave assisted annealing was used. Microwave heating decreased the annealing temperature by ~40% while the PEC performance was increased by two-fold. The improved performance is attributed to the lower processing temperatures and rapidity of the microwave method that help to retain the nanostructure of the thin films whilst restricting the grain coalescence to a minimum. Around 60% of the energy can be saved using this low carbon foot-print approach compared to conventional annealing procedures for the lab-scale preparation of hematite films – a trait that will have significant implications for scale-up production. The lower processing temperature requirements of the microwave process can also open up the possibility of fabricating hematite thin films on conducting, flexible, plastic electronic substrates.
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Hadjixenophontos, Efi [Verfasser]. "Hydrogen transport in thin films : Mg-MgH2 and Ti-TiH2 systems / Efi Hadjixenophontos." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2018. http://d-nb.info/1167771435/34.
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Taylor, Mark Philip. "Studies of the reaction of silane and hydrogen peroxide forming silica thin films." Thesis, University of Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337161.
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Guardi, Giorgia. "Thickness effects on electrochemical and gas-phase hydrogen loading in magnesium thin films." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/24841/.
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Renewable hydrogen is one of the tools necessary to reduce carbon emissions and achieve climate neutrality by 2050, so its production and consumption is planned to increase in the following 30 years. Developing new techniques for hydrogen storage is thus extremely relevant at the moment. Magnesium is a good candidate for hydrogen storage in solids due to its light weight, abundance, safety of operation and high achievable hydrogen density. However, the Magnesium-Hydrogen system needs to be investigated and understood more deeply.
This work focuses on the behaviour of hydrogen in magnesium thin films, using the techniques of electrochemical loading in KOH and gas-phase loading. The formation of magnesium hydride was studied by measuring and comparing isotherm curves.
With electrochemical loading it was possible to observe different behaviours during magnesium hydride formation, related to the intensity of the applied driving force. Both hydrogen loading techniques allowed to observe effects related to the thickness of the Magnesium layer. In particular, the voltage or pressure at which Magnesium hydride is formed increases as the film gets thinner.
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Wilson, Tate. "Thermodynamics of helium and hydrogen films adsorbed on single-walled carbon nanotube bundles /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/9754.
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Magnfält, Daniel. "Alternative method for deposition of alumina thin films." Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-16706.
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Deposition of alumina thin films in the presence of fluorine as a method for reducing thehydrogen incorporation in the films was investigated in this thesis. Hydrogen incorporated in alumina thin films have been shown to cause a lower density and refractive index in amorphous films, assist electrical conduction through thin amorphous films as well as inhibiting the formation of the thermally stable α-phase. The depositions were made in a ultra high vacuum system where high vacuum conditions were simulated by leaking water vapor into the system. No substrate heating or substratebias was applied. Films were deposited at a range of fluorine partial pressures, from 2,5×10-6- 5×10-5 Torr, and were analyzed by elastic recoil detection analysis, nuclear reaction analysis, scanning electron microscopy and x-ray diffraction. Mass spectrometry measurements were done during the depositions to analyze the deposition process. The mass spectrometry investigations show that there is a trend of increasing O2 partial pressures with increasing fluorine partial pressures during the depositions. This is attributed to the well known reaction: 2H2O+F2→O2+4HF. However, no trend in the measured water partial pressures can be observed. The increase in the O2 partial pressure is therefore attributed to a reaction between water and fluorine on the chamber walls. The chemical analysis show that the hydrogen incorporation in the films were lowered from ~10 at.% when deposited in the presence of water vapor to ~3 at.% when deposited in the presence of water vapor and 2×10-5 Torr fluorine. The hydrogen incorporation stabilize at ~3 at.% at higher fluorine partial pressures. However, there is also a large amount of fluorine incorporated in the films, ~20 at.% with a fluorine partial pressure during the deposition of 2×10-5 Torr and ~46 at.% with a fluorine partial pressure of 5×10-5 Torr. There is a slight increase in the aluminum concentration in the films deposited with fluorine. This is attributed to bonding the hydrogen in aluminum hydroxide while the reminder forms Al2O3 or Al leading to an increase in the aluminum concentration in the film. A linear decrease in the deposition rate with increasing fluorinepartial pressures during the deposition was observed, this can be explained by sputter etching of AlFx and AlOxFy by energetic O- ions. The XRD investigation show that the films deposited with the highest fluorine partial pressures were x-ray amorphous, the films with deposited with lower fluorine partial pressures are therefore also assumed to be amorphous.
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Tuckute, S., L. Pranevicius, L. Pranevicius, and M. Urbonavicius. "Oxygen implantation and behaviour into Ті thin films from water vapour plasma." Thesis, Видавництво СумДУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/20814.
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The behavior of O atoms in Ti film is investigated under high-flux, low-energy molecular water ion implantation. After 10 min of irradiation at room temperature, the anomalously deep penetration of oxygen without formation of new chemical compounds
observable by XRD has been registered in Ti films using Auger spectroscopy analysis. It is shown that the surface energy increases under ion irradiation, and the relaxation processes minimizing the surface energy initiate the redistribution of atoms. Two surface energy relaxation processes are considered: (i) the mixing of atoms on the surface resulting in annihilation of surface vacancies; and (ii) the annihilation of surface
vacancies by atoms transported from the bulk. The theoretical considerations are in agreement with the experimental results if to assume that the mass-transport in the bulk is controlled by the processes on the surface and the adsorption of reactive atoms or molecules leads to local and long-range restructuring and adatom relocation at the surface.
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Looi, Hui Jin. "Hydrogen doped thin film diamond : properties and application for electronic devices." Thesis, University College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392343.
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Johansson, Emil. "Synthesis and Characterisation of Potential Hydrogen Storage Materials." Doctoral thesis, Uppsala universitet, Fysik III, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4509.
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The dissociative and non-dissociative hydrogen uptake in carbon nanostructures and metallic films were investigated by measurements and analysis of solubility isotherms. The total, non-dissociative, uptake for multi-walled nano-barrels and amorphous nanoporous carbon was determined to be 6.2 and 4.2 wt. % respectively at 77 K and the adsorption energies (at lowest coverage) -7.2 and -4.2 kJ/mol. At 298 K the H-uptake was negligible. At low concentrations the H-uptake of Nb-films is strongly affected by the film thickness. For thicknesses less then about 31 nm, the absorption energy was found to be temperature dependent. Such changes have not been observed in Nb films before. The presence of multiple absorption energies was shown to limit the possibility to obtain relevant absorption and interaction energies by traditional Sievert's and van 't Hoff analysis. The Mg1-xNix system (0<0.43) was investigated with respect to the hydrogen uptake. For Mg2Ni the hydrogen uptake, at an external hydrogen pressure of 1 bar, is close to 1.33 H/M (Mg2NiH4). The enthalpy of formation is smaller in the film as compared to bulk material. The changes in the absorption energy are caused by the adhesion to the substrate as well as the nanocrystallinity of the absorbing layers. The optical band gap of Mg2NiH4 was determined to be 2.4 eV. In Mg1-xYx (0<0.17) it was found that the Y-concentration limits the hydrogen uptake at 1 bar. However, the kinetics of the uptake improves substantially with a minimum of 7 at.% of Y. For Mg-Y the optical band gap (3.6 eV) is independent of Y concentration within the concentration range investigated, while the transmittance decreases with increasing Y content.
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Al-Mufachi, Naser Azzat. "Effects of palladium thin films on the hydrogen permeability of Pd-Cu alloy membranes." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6028/.
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The hydrogen permeability of surface modified Pd\(_6\)\(_0\) Cu\(_4\)\(_0\) wt% (Pd\(_4\)\(_7\)\(.\)\(_3\)Cu\(_5\)\(_2\)\(_.\)\(_7\)at%) membranes have been determined for the first time. Surface modification was accomplished through the deposition of Pd thin films of three different thicknesses (95.5 ± 0.1, 797.4 ± 0.2 and 1,409.6 ± 0.2 nm) on to one side of a range of as-received Pd\(_6\)\(_0\) Cu\(_4\)\(_0\) wt% membrane coated with a 1,409.6 ± 0.2 nm thick Pd thin film positioned on the feed side (445 kPa of hydrogen pressure) and cycled between 50 and 450 °C achieved the highest hydrogen permeability of 1.09 x 10\(^-\)\(^8\) mol m\(^-\)\(^1\) s\(^-\)\(^1\) Pa\(^-\)\(^0\)\(^.\)\(^5\) at 450 °C during the third cycle. This is a 58% increase on the value measured for the as-received Pd\(_6\)\(_0\) Cu\(_4\)\(_0\) wt% under the same conditions. This improvement can be attributed to a Pd-rich Pd-Cu face centred cubic (FCC) phase forming through interdiffusion between the Pd thin film and bulk Pd-Cu membrane as a result of the test conditions used during hydrogen permeability measurements. This introduces a larger hydrogen concentration gradient across the membrane due to the relatively high hydrogen solubility of the Pd-rich Pd-Cu FCC phase resulting in the observed increase in permeability.
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Kayani, Asghar Nawaz. "Deposition and characterization of Diamond-like carbon films with and without hydrogen and nitrogen." Ohio University / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1080935389.
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Chin, Xiao Yao. "Ni-C electrocatalysts for hydrogen oxidation in low-temperature acidic fuel cells." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610637.
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