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Mohamed, Rozita. "Preparation of nano-structured macro-porous materials." Thesis, University of Newcastle upon Tyne, 2011. http://hdl.handle.net/10443/1317.
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This research reveals a catalyst development towards achieving catalysts with hierarchical porous structures with enhanced mechanical properties by using nano-structured macro-porous PolyHIPE polymer. This work can be divided into two parts: the fabrication and its characterisation of hierarchical metal structure using PHP and other fibre materials; and the fabrication and characterisation of PHP with silica particles and glass wool, further coated with silane material as templates. A catalyst system was successfully fabricated forming a 3D-interconnecting network of pore size, ranging from tens of micrometers and gradually reducing finally to nanometer scale. An electroless deposition flow through method using Ni-B bath solution was performed on the templates and was subsequently heat treated to obtain porous metallic structures, thus providing accessibility for reactants to the surface and for products away from the surface. Meanwhile, silanated templates were produced by surface treatment. This was performed by submerging templates directly into the silanes solution at room temperature (24°C) using a water-ethanol based solution of the silanes. The polymer-metal/alloy or silica functionalized based composite demonstrated a high impact strength. The results showed that not only hierarchical pore structure was formed, but it was also demonstrated that silica particles were totally and uniformly covered/coated by metal deposit and had good adhesion. When used on glass wool, silanation had greatly improved the bond strengths of metal deposits to the templates. SEM micrographs revealed that the formation of cracks were tremendously reduced and exhibited higher bond strengths due to silanated glass surface. It is expected to be more efficient and robust in the case of an enhanced surface area, and most desirable in catalyst applications.
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Cervin, Nicholas. "Porous Cellulose Materials from Nano Fibrillated Cellulose." Licentiate thesis, KTH, Fiberteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-104196.
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In the first part of this work a novel type of low-density, sponge-like material for the separation of mixtures of oil and water has been prepared by vapour deposition of hydrophobic silanes on ultra-porous nanocellulose aerogels. To achieve this, a highly porous (> 99 %) nanocellulose aerogel with high structural flexibility and robustness is first formed by freeze-drying an aqueous dispersion of the nanocellulose. The density, pore size distribution and wetting properties of the aerogel can be tuned by selecting the concentration of the nanocellulose dispersion before freeze-drying. The hydrophobic light-weight aerogels are almost instantly filled with the oil phase when they selectively absorb oil from water, with a capacity to absorb up to 45 times their own weight. The oil can also be drained from the aerogel and the aerogel can then be subjected to a second absorption cycle.In the second part of the work a novel, lightweight and strong porous cellulose material has been prepared by drying aqueous foams stabilized with surface-modified NanoFibrillated Cellulose (NFC). Confocal microscopy and high-speed video imaging show that the long-term stability of the wet foams can be attributed to the octylamine-coated, rod-shaped NFC nanoparticles residing at the air-liquid interface which prevent the air bubbles from collapsing or coalescing. Careful removal of the water yields a porous cellulose-based material with a porosity of 98 % and a density of 30 mg cm-3. These porous cellulose materials have a higher Young’s modulus than other cellulose materials made by freeze drying and a compressive energy absorption of 56 kJ m-3 at 80 % strain. Measurements with an autoporosimeter reveal that most pores are in the range of 300 to 500 μm.QC 20121107
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Traum, Matthew J. (Matthew Jason) 1977. "Latent heat fluxes through nano-engineered porous materials." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40361.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Vita.
Includes bibliographical references (p. 201-206).
Micro- and nano-scale truss architectures provide mechanical strength, light weight, and breatheability in polymer barriers. Liquid evaporation and transport of resulting vapor through truss voids (pores) cools surfaces covered by the barriers, suggesting the possibility for simultaneous protection of humans from mechanical and thermal stresses. Design of real systems employing this technique requires quantitative understanding of vapor transport within the truss pores and accompanying latent heat lift under ambient temperature and pressure. One application is desert Soldier protection. Need exists to clarify whether smaller pore diameters affect surface cooling and water vapor transport owing to fluid rarefaction or surface interactions. Contrasting previous studies where pressure within capillaries of fixed diameter was modulated, in this thesis Knudsen Number (Kn) was systematically varied by changing pore diameter at constant pressure (one atmosphere). Cooling efficacy was assessed for porous membranes with pore diameters ranging from 39 to 14,400 nm, varied in regular increments. Evaporative cooling experiments simulated combined daytime desert solar and metabolic thermal load on humans by heating an evaporation chamber partially filled with liquid water and capped with a porous membrane.
(cont.) Hot, dry gas was swept over the membrane, simulating desert ambient conditions. By continuously weighing the entire evaporation apparatus, intrinsic pore diffusion coefficients for dilute water vapor in air were deduced for each membrane by correcting for upstream and downstream boundary layer mass transfer resistances. Pore diameter impact on evaporative cooling of an underlying surface by water vapor transport across two types of porous polymer membranes with micro/nano-scale truss architecture was quantified. This research showed that transition diffusion regime theory predicted observed transport rates to better than + 35% for pore diameters between 14,400 nm and 60 nm (0.01 < Kn < 3). Despite low membrane porosity, substantial Fractional Accomplished Cooling (up to 60% maximum achievable) was demonstrated via latent heat transport. The absolute magnitude of achieved surface cooling was 3.7 K to 14.0 K. An engineering design correlation was developed linking latent heat transport at various Knudsen Numbers (pore diameters) to evaporative cooling efficacy. Results of this research inform design of porous mechanical barriers that permit evaporative cooling of underlying surfaces.
by Matthew J. Tram.
Ph.D.
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Burt, Luke Anthony. "Synthesis and characterisation of novel functional phthalocyanine nano-porous materials." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31347.
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This project was focused on the synthesis of novel phthalocyanines for the construction of porous molecular crystals that incorporate the desirable properties associated with phthalocyanine complexes. Conventional phthalocyanines are relatively insoluble, therefore, remain difficult to process, characterise and effectively crystallise. To counteract this problem, bulky 2,6-di-iso-propylphenoxy substituents were placed around the aromatic core of the phthalocyanine macrocycle and proved to successfully inhibit the co-facial aggregation which limits their solubility. These bulky groups also direct the crystallisation of the phthalocyanine macrocycle inducing a cubic packing arrangement with significant accessible solvent filled voids. The aim of this work was the modification of this 2,6-di-isopropylphenoxy substituted phthalocyanine to enhance the magnetic and catalytic properties and demonstrate its suitability as a platform for creating iso-reticular systems with increased functionality. It was anticipated that mixed double decker complexes of this derivative and another phthalocyanine macrocycle would form crystals with the same cubic spatial arrangement, while maintaining their high catalytic activity or single molecular magnetism behaviour. Firstly, a larger number of transition metals along with some lanthanide metals have been incorporated within this substituted phthalocyanine, extending the previous work on this system. Furthermore, the corresponding contracted macrocycle boron subphthalocyanine was also investigated. While the 2,6-diisopropylphenyl substituents did not greatly affect the electronic properties of the subphthalocyanine, the solid state properties of the material proved interesting. The lanthanide phthalocyanine complexes were further employed in the preparation of lanthanide double decker phthalocyanines that possess single molecule magnetic properties. While retaining this desired property, they also crystallised to produce clathrates with large solvent filled voids. A different double decker complex which contained two iron metal centres bridged by a single nitrogen atom was also prepared from the octa substituted 2,6-di-iso-propylphenoxy phthalocyanine and an unsubstituted phthalocyanine. This nitrido bridged di-iron phthalocyanine complex displayed similar catalytic activity to previously reported systems of this kind and crystallised to afford cubic crystals with large solvent filled voids. These were shown to be accessible by both solvent and ligand exchange. Suitable bidentate ligands for structural stabilisation could be also incorporated. Finally, the preparation of an alternatively substituted phthalocyanine for the construction of a potential porous molecular crystal was studied. By synthesising a hexamethylindan substituted phthalonitrile, it was possible to obtain a soluble phthalocyanine that crystallised to give a clathrate that contained large one-dimensional voids.
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Kodumuri, Pradeep. "IN-SITU GROWTH OF POROUS ALUMINO-SILICATES AND FABRICATION OF NANO-POROUS MEMBRANES." Cleveland State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=csu1243304850.
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Cheng, Chuan, and 程川. "Electro-chemo-mechanics of anodic porous alumina nano-honeycombs: self-ordered growth and actuation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hub.hku.hk/bib/B50899582.
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Self-ordered anodic porous alumina with a nano-honeycomb structure has recently been extensively used as templates for the synthesis of various nanomaterials for diverse applications. However, due to the insufficient knowledge on the combined electro-chemo-mechanical processes, the formation mechanism of self-ordering has been under debate for decades without clear conclusions. Also, fast fabrication of highly self-ordered and mechanically stable anodic porous alumina is still a challenge. Furthermore, the actuation behavior of anodic porous alumina upon external mechanical and electrical triggering in an electrochemical cell has not been exploited.
In this work, firstly, we investigated the self-ordering mechanism by establishing a kinetics model involving the Laplacian electric potential distribution and a continuity equation for current density within the oxide body. Current densities governed by the Cabrera-Mott equation are formed by ion migration within the oxide as well as across the interfaces. The pore channel growth, due to electric-field-assisted reactions, is governed by Faraday’s law. Real-time evolution of pre-patterned pore channel growth was simulated in two-dimensional cases by finite element method. The simulations revealed a parameter domain within which pre-patterned pore channels will continue to grow in a stable manner during the subsequent anodization if the pre-patterns are commensurate with the self-ordered configurations, or these are driven into stable if the pre-patterns do not initially match the self-ordered configurations. This was verified in experimentally observed pore channel growth under the guidance of pre-patterns made by focused-ion-beam milling. Furthermore, the simulations revealed that ionization reaction on (001) oriented Al grain is relatively easier than that on (101) grain, which results in stable and unstable pore channel growth on (001) and (101) Al grains, respectively, both of which were observed from the simulations and experiments.
Secondly, a scheme on quantitative evaluation of self-ordering qualities in anodic porous alumina has been developed, based on which we systematically searched the optimum self-ordering conditions, by varying the key anodization factors, including substrate grain orientation, electrolyte concentration, temperature, voltage, and time. A high acid concentration and high temperature anodization method was found. Compared with conventional methods, the present method can realize fast formation of highly self-ordered, and mechanically stable anodic porous alumina under a continuous range of anodization voltage with tunable interpore distances.
Thirdly, reversible bending was found in anodic porous alumina-Al composites upon cyclic electric actuation, as directly observed by an optical microscope and detected by in situ nanoindentation. The bending is thought to be the result of charge-induced surface stresses in the nanoporous alumina. The results suggest a new type of composite materials for applications as micro-scale actuators to transform electrical energy into mechanical energy. Furthermore, the composite exhibits significant softening during in situ nanoindentation when the estimated maximum stress underneath the indenter is exerted on the metal/oxide interface. Softening was further verified by in situ microindentation. Electron microscopy examination indicated that the softening is due to a combination of high compression stress and electric field acting near the interface, which enhance ionization reaction and cause the interface to move faster into the substrate.published_or_final_version
Mechanical Engineering
Doctoral
Doctor of Philosophy
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Greco, Pier Paolo. "Development of novel polymeric and composite nano-structured micro-porous materials for impact resistance applications." Thesis, University of Newcastle upon Tyne, 2014. http://hdl.handle.net/10443/2517.
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Impact resistant materials (IRMs) are widely used in the automotive and packaging industry. Their main purpose is the protection of the transported occupants or goods. Cellular materials as well as structures combine lightness with large deformation under load. The energy absorption mechanism is provided by limiting the peak load and ensuring the elastic deformation of the IRMs. Polymeric foams are largely used as IRMs due to their cellular structure. Prediction of the foam properties in terms of Young’s Modulus (Elastic Modulus) and the onset of Plateau Region can be related to the foam density and the mechanical properties of the bulk material (Gibson and Ashby model). The structure of the foam is only partly accounted for in the Gibson and Ashby model in terms of material density. However, it is possible to produce cellular materials with the same density but very different internal architectures. This cannot easily be exploited in conventional polymer foams but the processing of High Internal Phase Emulsion (PolyHIPE) and its polymerisation route to produce PolyHIPE Polymers (PHPs) can produce materials with very different structures. Experiments have revealed that the PHPs properties are dictated by their detailed structure. Elastic PHPs with: 1) varying ratio of polymerizable oil phase with respect to aqueous phase and 2) varying mixing time/energy input were produced and tested by mechanical compression at different temperatures and strain rates. The elastic modulus increases with a quadratic law as a function of the polymerizable oil phase content of the HIPE when the mixing time is the same, as predicted by the model. The Specific Absorption Energy (SAE), represented by the area under the stress-strain curve, increases in a similar way. Increasing mixing time on HIPE has the effect of modifying the cellular structure. Smaller pores and narrower distribution of pores are observed. Such features are consistent for any set of PHPs densities and represent a design tool when some specific mechanical characteristics are prescribed. The assessment of process-structure-properties relationships was performed by combining the mechanical response of the various PHPs with the imaging of their structure by Scanning Electron Microscopy. The properties of PHPs were benchmarked with reference to two commercially available products. One material is characterised by a porous structure with a relatively high Young’s Modulus while the other by a non-porous and composite-like solid structure with lower elastic modulus. The properties of the PHPs can be engineered to shift from a foam-like material to a composite-like through the processing parameters which in turn modify the material porous structure. The temperature has very limited effect on the PHPs material unlike for the reference commercial materials. The enhancement of properties (increasing Elastic Modulus and SAE) induced by changing the processing route are remarkable for such a class of porous materials. When plotted on a Modulus-Density chart, the PHPs fill an existing material-chart gap, representing a new class of materials and opening new possibilities as IRMs.
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Kirstein, Johanna, Christophe Jung, Christian Hellriegel, and Christoph Bräuchle. "Single molecule spectroscopy: translational and rotational diffusion of single fluorescent dyes in nano-structured porous materials." Diffusion fundamentals 2 (2005) 94, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14431.
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Daniel, Hedbom. "Linker substitution in ZIF-8 and its effect on the selective uptake of the greenhouse gases CH4, CO2 and SF6." Thesis, Uppsala universitet, Nanoteknologi och funktionella material, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-434657.
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In this master thesis project, attempts were made to synthesize, pore size tailor, and characterize ZIF-8 and several mixed-linker ZIF structures to improve capture of the greenhouse gasses CH4, CO2, and SF6. Three experimental linkers, 2-methylbenzimidazole, 2-aminobenzimidazole, and 5-nitrobenzimidazole were chosen to gradually substitute 2-methylimidazole as the linker in ZIF-8. This substitution was intended to gradually reduce pore sizes and possibly adding functionality to the apertures present in ZIF-8 (three different series). The methods of synthesis were first evaluated by performance and modified. Three series of ZIF-hybrids were then synthesized and characterized using PXRD, FTIR, 1HNMR, SEM, extensive sorption measurements, and subsequent modeling to evaluate any success tailoring the hybrid ZIF apertures to increase gas sorption. After modifying synthesis conditions, the undertaking was deemed a success as all three linkers were possible to incorporate to some degree. Hybrid ZIFs were mostly XRD-crystalline. The cleaning process was deemed sufficient. Linker incorporation was not complete but increased with the added linker. Sodalite topology was confirmed in ZIF-8 samples and confirmed as modified in hybrid ZIFs. The hybrid ZIFs did indeed show altered sorption results and surprisingly promising results regarding gas selectivity (favoring sorption of one gas over that of another).
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Ruan, Juanfang. "Development of electron microscopy towards nano-structured porous materials : focus on novel zeolites from layered silicates and chiral mesoporous nanotubes /." Stockholm : Department of Physical, Inorganic and Structural Chemistry, Stockholm university, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-7439.
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Raed, Khaled. "Investigation of Knudsen and gas‐atmosphere effects on effective thermal conductivity of porous media." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2013. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-117386.
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Die vorliegende Arbeit befasst sich mit Untersuchung der gekoppelten Einflüsse von Gasart, Porengröße und Porengrößenverteilung auf die effektive Wärmeleitfähigkeit nicht-durchströmter poröser Materialien (Dämmstoffe). Diese Zusammenhänge sind bisher nur ansatzweise bekannt und für eine spätere praktische Anwendung von zunehmend großer Bedeutung. Um dies zu erreichen wurden 12 verschiedene hoch poröse Materialien (Porosität höher als 70 %) ausgewählt, die unterschiedlichen Porengrößenverteilungen im Makro- Mikro- und Nanobereich haben. Die effektive Wärmeleitfähigkeit wurde hauptsachlich in zwei unterschiedlichen Messverfahren untersucht. Die Messungen erfolgt bei normalem Druck in vier Gas Atmosphären (Kr, Ar, N2 and He) bei Temperaturen bis maximal 900 °C. Kritische Analyse zum jeweiligen Messverfahren und Auswertungsalgorithmus wurden durchgeführt. Ein mathematisches Model basiert auf die Porengrößenverteilung mit Berücksichtigung des Knudsen Effekts wurde entwickelt um die Änderung der effektiven Wärmeleitfähigkeit beim Wechsel der Gas Atmosphäre auszuwerten. Diese führt zu besser Ergebnisse als die ausgewertet Ergebnisse von den vorhandenen Modellen aus der Literatur. In the present work, the influences of exchanging the filling gas accompanied with Knudsen effect on effective thermal conductivity were investigated with experiments and physical mathematical modeling. This work is thought to be the first intensive study in this area of the research, which includes twelve different porous insulation materials. Analysis of the huge number of experimental results leaded to new observations regarding various coupling effects. An improved model for predicting the change in effective thermal conductivity due to exchanging the filling gas has been developed with regards to the Knudsen effect based on models for rarefied gases and parallel arrangements models for effective thermal conductivity
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Rudaz, Cyrielle. "Aérogels à base de cellulose et de pectine : Vers leur nano-structuration." Phd thesis, Ecole Nationale Supérieure des Mines de Paris, 2013. http://pastel.archives-ouvertes.fr/pastel-00957296.
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Le but de ce travail de thèse est de développer des aérogels biosourcés, mécaniquement résistants et thermiquement très isolants (voire super-isolants). Les aérogels à base de cellulose, souvent appelés " aérocelluloses ", sont connus pour être très poreux et extrêmement légers. Ils présentent en revanche une grande dispersion de tailles de pores, donnant de propriétés thermiques relativement modestes. Nous avons étudié plusieurs approches pour améliorer la morphologie des aérocelluloses: la modification du solvant, la réticulation chimique de la cellulose et la formation d'hybrides avec d'autres polymères. La réticulation de la cellulose a réellement permis d'affiner la structure poreuse de l'aérocellulose vers une nano-structuration ce qui a amélioré la conductivité thermique, s'approchant du domaine de la super-isolation (0.026 W.m-1.K-1). Un autre polysaccharide, la pectine, a été utilisé pour préparer un aérogel également poreux et très léger, " l'aéropectine ". L'aéropectine et l'aérocellulose présentent de fortes similitudes dans leur morphologie. Cependant, l'aéropectine possède de meilleures propriétés thermiques, super-isolantes (0.020 W.m-1.K-1), grâce à la nano-structuration du réseau poreux. Ces aérogels sont 100% biosourcés avec un faible impact environnemental, et sont très prometteurs non seulement pour l'isolation thermique mais également pour de nombreuses autres applications, telle que la libération contrôlée de médicaments ou la catalyse. La formation d'aérogel de silice à l'intérieur de la structure poreuse d'aéropectine a augmenté la surface spécifique jusqu'à 700 m2/g et a permis de diminuer la conductivité thermique (0.017 W.m-1.K-1).
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Sun, Xida. "Structured Silicon Macropore as Anode in Lithium Ion Batteries." Wright State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=wright1316470033.
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Jafari, Abbas. "The Effect of Citric Acid on Amorphous Calcium Carbonate, Mesoporous Magnesium Carbonate and Calcium Magnesium Composite : A brief study." Thesis, Uppsala universitet, Nanoteknologi och funktionella material, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-435989.
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During the past decades, emission of greenhouse gases has accelerated to unsustainable levels. This is a serious issue that can have a devastating impact on everything from global economy to the terrestrial or marine ecosystem. A method for reducing the emission is named carbon capture and storage, which this project is based on. In this study, different concentrations of citric acid (CA) is used (as an additive) for the enhancement and optimization of carbon dioxid sorption properties of amorphous calcium carbonate (ACC), mesoporous magnesium carbonate (MMC) and calcium magnesium carbonate composite (CMC). These materials were heat treated in a calcination and an alternating carbonation process in order to study the carbon dioxid sorption performance. During the calcination process, CA undergoes a pyrolysis reaction in order to increase the specific surface area of the individual nanoparticles, which is an important factor for the sorption capacity. In the case of CMC, different molar ratios of magnesium oxide and calcium oxide were used in order to alter the concentration of the resulting magnesium oxide prior to heating. All three materials consisted of aggregations of nanometer-sized particles. Thermogravimetric analysis, scanning electron microscopy, surface area and porosimetry and infrared spectroscopy analysis suggest that the carbon dioxid sorption properties and the sintering stability of ACC and MMC do not improve since CA evaporates due to pyrolysis. Sintering was a greater problem for the evaluated CA treated ACC sample. However, in the case of CMC, the sorption and sintering properties were enhanced due to the higher Tamman-temperature of magnesium oxide, specifically for the lower concentration of magnesium oxide. After 19 carbonation cycles, CMC-1:1-25% CA showed signs of improved sintering stability and sorption capacity, compared to ACC-75% CA.Presentationen genomfördes på distans.
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Riachy, Philippe. "Hierarchically Porous Silica Materials for the Encapsulation of Molecules of Interest." Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0013/document.
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Ce travail porte sur la préparation de matériaux silicatés à porosité hiérarchisée pour l'encapsulation de molécules d'intérêt dans le domaine de la pharmacie et en tant que biocatalyseur. Afin d’atteindre cet objectif, les nano-émulsions sont choisies comme empreinte pour créer les macropores du matériau en raison de la taille homogène et réduite des gouttelettes de l’émulsion (inférieure à 100 nm). Pour cela le système Remcopal 4/décane/eau est investi en déterminant les conditions les plus optimales de formation de nano-émulsion, via les méthodes d'inversion de phases. L’ajout de micelles aux nano-émulsions ne déstabilise pas les émulsions et permet la formation d’un réseau de mésopores organisés selon une symétrie hexagonale. Les matériaux hybrides issus des matériaux poreux contenant encore la phase organique sont dopés par le ketoprofène en vue d’étudier la libération de ce dernier. Celle-ci se révèle sensible au pH. De plus, cette étude de la libération du kétoprofène à partir du matériau méso-macroporeux indique qu'elle est assistée par les micelles qui sont solubilisées dans la solution réceptrice. Le deuxième objectif de ce travail est d'utiliser ces matériaux poreux en tant que biocatalyseur pour la synthèse de biodiesel à partir d'huile de colza. Pour cette application, il est nécessaire que les matériaux résistent à l’immersion dans des milieux aqueux. L’étude de la stabilité hydrothermale a montré que le matériau calciné présente la meilleure stabilité dans l’eau bouillante. Par ailleurs, le matériau peut résister jusqu’à 550°C, la structure ne subissant que des dégradations mineures. Nous avons également utilisé un matériau silicaté à double mésoporosité préparé à partir de micelles fluorées et hydrogénées coexistant dans une même solution. L'évaluation thermique et hydrothermale indique que ces matériaux présentent deux cinétiques de déstructuration qui correspondent à chacune des deux matrices ayant deux tailles de pores différents. L’immobilisation de la lipase Mml est étudiée sur le matériau méso-macroporeux calciné et sur le matériau à double mésoporosité. Les isothermes d'adsorption ont permis de mettre en évidence que le matériau à double mésoporosité peut encapsuler plus d’enzymes que son homologue méso-macroporeux. L’activité enzymatique, au regard des réactions de transestérification, est de façon inverse plus importante avec le matériau méso-macroporeux calcinéThis work concerns the preparation of silica materials with hierarchical porosity for the encapsulation of molecules of interest in the field of drug delivery and as biocatalysts. In order to reach this goal, the nano-emulsions were chosen as templates for the macropores of the material because of the homogeneous and small size of the emulsion droplets (less than 100 nm). The system Remcopal 4/decane/water was investigated and the optimal conditions for which nano-emulsion is formed via the phase inversion methods were determined. Adding micelles to the nano-emulsions does not affect its stability and can form a network of mesopores organized with a hexagonal symmetry. Hybrid materials which are hierarchically porous materials where the organic phase is still present, were doped with ketoprofen to study its release, which proved to be pH sensitive. Moreover, the study of the release of ketoprofen from the meso-macroporous material indicates that it is assisted by the micelles which are solubilized in the release medium. The second objective of this work was to use these porous materials as a biocatalyst for biodiesel synthesis from colza oil. For this application it was necessary that the materials are resistant to immersion in aqueous media. The study of the hydrothermal stability shows that the calcined material has the best stability in boiling water. Moreover, the material can withstand up to 550 ° C, the structure undergoes only minor damages. We also used a dual-mesoporous silica material prepared from hydrogenated and fluorinated micelles coexisting in the same solution. Thermal and hydrothermal evaluation indicates that these materials have two different decay kinetics corresponding to each of the two matrices having different pore sizes. The immobilization of lipase Mml was studied on the meso-macroporous calcined material and the dual-mesoporous material. The adsorption isotherms were used to demonstrate that the dual-mesoporous material can encapsulate more enzymes than its meso-macroporous counterpart. On the other hand, the enzyme activity, evaluated by the transesterification reactions, is more important for the calcined meso-macroporous material
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Le, Van Lich. "Multi-physics Properties in Topologically Nanostructured Ferroelectrics." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/217166.
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Nehache, Sabrina. "Elaboration de membranes à partir d’assemblages nano-organisés de particules polymères." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS080.
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Dans une optique de développement de nouvelles membranes innovantes, ce travail de thèse a permis l'élaboration de films minces nano-structurés et nano-poreux à partir de particules de polymère (copolymères ABA, AB, et homopolymère/MOF). Ces films ont notamment pu être utilisés en tant que membranes de filtration d'eau ou de mélange de gaz. Concernant les copolymères triblocs de type ABA (PS-PNaSS-PS), cette étude a montré que des films nano-poreux présentant des structures variées (nid d'abeilles, isoporeuse et compacte) pouvaient être obtenus. Les morphologies de ces particules pouvaient être adaptées en fonction de la taille des blocs hydrophiles et hydrophobes du copolymère, de la composition en solvant et de la concentration. Pour l'élaboration de films à partir de copolymère diblocs, des nanoparticules sphériques monodisperses, constituées de PDMAEMA-PMMA, ont été préparées in situ (PISA) par polymérisation RAFT en dispersion dans l'éthanol, à partir d'un agent de transfert fonctionnalisé coumarine. Les expériences successives d'irradiation UV ont montré que les nanopaticules ainsi fonctionnalisées pouvaient être connectées de façon réversible via la dimérisation de la coumarine. Les films minces ainsi élaborés présentaient des propriétés dynamiques dues à l'établissement de la formation réversible du cyclobutane lors de l'irradiation UV de la coumarine. Ce travail de thèse a été clôturé par la préparation de « Mix Matrix Membranes (MMMs) » à partir d'un mélange de polyimide (Matrimid®) et de nanoparticules de ZIF-8 pour la réalisation de membranes à perméation gazeuse. Une nouvelle approche d'élaboration des MMMs a permis d'obtenir la formation de membranes parfaitement homogènes avec une cohésion améliorée entre les MOF et la matrice de polymère. Une meilleure séparation du mélange de gaz CH4/CO2 a ainsi pu être obtenueThis thesis deals with the development of nano-structured thin nano-porous films from polymeric particles (ABA, AB copolymers and polymer/MOF) in perspective of developing new innovative membranes. The obtained films have been used as water filtration or gas separation membranes. Regarding the ABA triblock copolymer made of polystyrene-sodium polystyrene sulfonate-polystyrene (PS-PNaSS-PS) it was shown that nano-porous films with various structures (honeycombs, isoporous and compact), could be made. The morphologies of these nanoparticles could be tuned depending on the hydrophobic and hydrophilic block ratios, solvent composition and concentration. Concerning the study of the diblock copolymer, monodisperse spherical nanoparticles of PDMAEMA-b-PMMA were made in situ (PISA) using a coumarin functionalized RAFT chain transfer agent in ethanol. Upon UV irradiation, these particles could be connected reversibly through the dimerization of the coumarin function present on their corona. The resulting thin films had dynamic characteristic due to the establishment of the reversible formation of the cyclobutane ring under UV irradiation. This manuscript was concluded by preparation of Mix Matrix Membranes (MMMs) from mixture of polyimide (Matrimid®) and ZIF-8 nanoparticles to be used as gas permeation membrane. The employed new approach in this study led to formation of perfectly homogeneous membranes with improved cohesion between the MOF structure and the polymeric matrix. A better separation of CH4 / CO2 gas mixtures was achieved using the prepared MMM
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Ma, Hongfeng. "Étude numérique de la micro et nano structuration laser de matériaux poreux nanocomposites." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSES001.
Full textAbstract:
Cette thèse porte sur les simulations numériques de l’interaction laser avec des matériaux poreux. Une possibilité de traitement bien contrôlé est particulièrement importante pour la microstructuration laser du verre poreux et le nano-usinage de matériaux poreux semiconducteurs en présence de nanoparticules métalliques. La modélisation auto-cohérente se concentre donc sur une étude détaillée des processus impliqués. En particulier, pour comprendre les structures des micro-vides périodiques produits à l’intérieur du verre poreux par des impulsions laser femtoseconde, une analyse thermodynamique numérique détaillée a été réalisée. Les résultats des calculs montrent la possibilité de contrôler le micro-usinage laser en volume de SiO2 . De plus, les dimensions des structures densifiées par laser sont examinées pour différentes conditions de focalisation à de faibles énergies d’impulsion. Les dimensions caractéristiques obtenues à partir des structures sont corrélées avec les résultats expérimentaux. Comparés au verre poreux, les films mésoporeux TiO2 chargés d’ions Ag et de nanoparticules supportent des ré- sonances plasmoniques localisées. Les films nanocomposites obtenus sont capables de transférer des électrons libres et d’absorber l’énergie laser de manière résonnante, offrant des possibilités supplémentaires pour contrôler la taille des nanoparticules d’Ag. Pour identifier les paramètres optimaux du laser à onde continue, un modèle multi-physique prenant en compte la croissance des nanoparticules d’Ag, photo-oxydation, réduction a été développé. Les simulations réalisées montrent que la vitesse d’écriture laser contrôle la taille des nanoparticules d’Ag. Les calculs ont également représenté une nouvelle vision selon laquelle les nanoparticules d’Ag se développent devant le centre du faisceau laser du fait de la diffusion de chaleur. Il a été démontré que la croissance rapide activée thermiquement suivie d’une photo-oxydation est la principale raison du changement de taille et de température en fonction de la vitesse d’écriture. Un modèle tridimensionnel a été développé et reproduit les lignes écrites au laser. L’écriture de films mésoporeux TiO2 chargés de nanoparticules d’Ag par un laser pulsé promet également d’offrir des possibilités supplémentaires dans la génération de deux types de nanostructures: les rainures de surface périodiques induites par laser (LIPSS) et les nanogratings Ag à l’intérieur du film TiO2 . Pour mieux comprendre les effets d’un laser pulsé, deux modèles multiimpulsions - un semi-analytique et un autre basé sur une méthode par éléments finis (FEM) - sont développés pour simuler la croissance des nanoparticules d’Ag. Le modèle FEM s’avère précis car il traite mieux la diffusion de la chaleur à l’intérieur des films minces TiO2 . Le modèle pourrait être étendu à l’avenir pour comprendre la formation de nanogratings LIPSS et Ag dans de tels milieux en les couplant avec les migrations de nanoparticules, la fusion de surface et l’hydrodynamique.Les résultats obtenus ont ouvert de nouvelles perspectives sur le microtraitement laser des matériaux poreux et un meilleur contrôle laser sur la nanostructuration dans les films semiconducteurs poreux chargés de nanoparticules métalliquesThis thesis is focused on numerical simulations of the laser interaction with porous materials. A possibility of well-controlled processing is particularly important for the laser based micro-structuring of porous glass and nano-machining of semiconducting porous materials in the presence of metallic nanoparticles. The self-consistent modeling is, therefore, focused on a detailed investigation of the involved processes. Particularly, to understand the periodic micro-void structures produced inside porous glass by femtosecond laser pulses, a detailed numerical thermodynamic analysis was performed. The calculation results show the possibility to control laser micro-machining in volume of SiO2 . Furthermore, the dimensions of laser-densified structures are examined for different focusing conditions at low pulse energies. The obtained characteristic dimensions of the structures correlate with the experimental results. Comparing to the porous glass, the mesoporous TiO2 films loaded by Ag ions and nanoparticles support localized plasmon resonances. The resulted nanocomposite films are capable to transfer free electrons and to resonantly absorb laser energy providing additional possibilities in controlling Ag nanoparticle size.To identify the optimum parameters of the continuous-wave laser, a multi-physical model considering Ag nanoparticle growth, photo-oxidation, reduction was developed. The performed simulations show that the laser writing speed controls the Ag nanoparticles size. The calculations also depicted a novel view that Ag nanoparticles grow ahead of the laser beam center due to the heat diffusion. The thermally activated fast growth followed by the photo-oxidation was found to be the main reason for the writing speed dependent sizechange and temperature rises. A three-dimensional model was developed and reproduced the laser written lines.Writing of mesoporous TiO2 films loaded with Ag nanoparticles by a pulsed laser is, furthermore, promising to provide additional possibilities in the generation of two kinds of nanostructures: laser induced periodic surface grooves (LIPSS) and Ag nanogratingsinside the TiO2 film. To better understand the effects of a pulsed laser, two multi-pulses models - one semi-analytic and another one based on a finite element method (FEM) are developed to simulate the Ag nanoparticle growth. The FEM model is shown to be precise because it better treats heat diffusion inside the TiO2 thin films. The model could be extended in future to understand the formation of LIPSS and Ag nanogratings in such media by coupling with nanoparticle migrations, surface melting and hydrodynamics. The obtained results provided new insights into laser micro-processing of porous material and better laser controlling over nanostructuring in porous semiconducting films loaded with metallic nanoparticles
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Lin, Pao-Tai, and 林柏泰. "Synthesis of Nano-composites and Nano-porous Materials with Polymer Templates." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/85941617557481495623.
Full textAbstract:
碩士國立臺灣大學
化學研究所
89
Abstract Nano-composites and nano-porous materials were prepared from ionic polymer and metal oxide precursors by sol-gel methods. The ionic polymers were the derivatives of polystyrene, and the metal oxides were silica and titania. The interaction between the organic and inorganic component was varied depending on the functional groups on the polymers such as ammonium ion, sulfonate ion, and diol. The ratio of the organic/inorganic composites was also varied to determine the optimal condition for synthesis. Nano-composite was prepared when the polymer content in the composite was greater than metal oxide. Different methods were compared in order to find the best way in synthesis of nano-composite. The properties of the composites were characterized by elemental analysis, TGA, DSC, 1H-NMR, and GPC. The thermal properties of the nanocomposites were different from the polymer itself. The glass transition temperature (Tg) of the copolymer, polystyrene-poly-4-vinylbenzyl chloride, was lower than pue polystyrene. On the other hand, the Tg of the composite increased with the introduction of metal oxide and the amount of ionic functional groups on the copolymer. Nano-porous material was prepared when the polymer content in the composite was less than metal oxide. The organic component was removed by calcination to leave the porous structure. N2 adsorption-desorption isotherm, XRD, SEM, TGA, EA, NMR was used to character the properties of the nano-porous material. The polymers were used as shape-directing agents and addition of small organic molecule as co-templates was also examined. It was found that the porosity was sensitive to the pH of the synthesis gel, the temperature of hydrothermal process, and the addition of small organic template. Porous metal oxides with both meso- and micro- pores were obtained.
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Chen, Pei-kuan, and 陳佩冠. "Fabrication of Novel Nano/Micro Hierarchical Porous Materials for Catalytic Applications." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/45115152082033525938.
Full textAbstract:
碩士逢甲大學
環境工程與科學所
99
In this study, two different morphologies of zinc oxide have been prepared by hydrothermal system and then gold nanoparticles have been coated on the surface of zinc oxide by electrostatic self-assembly method to better enhance the efficiency of heterogeneous photocatalysis. Different alkaline conditions were use to evaluate the effect on morphology and optical characteristics of zinc oxide Thus, it was expected to produce more free radicals with high oxidation potential to promote surface catalysis for the degradation of dye molecules in the solution. Two phases were involved in this thesis: Phase I is photocatalyst preparation via hydrothermal method. Subsequently a simple electrostatic self-assembly method was developed to uniformly disperse Au (1 wt %) on ZnO surface in the presence of β-D-glucose as a stabilizer to improve the photocatalytic activity. Phase II is heterogeneously photocatalytic degradation of Orange II dye. The crystalline phase composition, surface structure, and light absorption degradation of ZnO photocatalysts were examined using SEM, XRD, UV-visible spectroscopy, XPS, PL, and Raman spectra. According to the experimental results, it showed that coral-like ZnO was prepared by nanosheet-based ZnCH microspheres, which was self-assembled by the hydrothermal process using urea as the homogeneous precipitant and were decomposed into microspheric forms of multilayered ZnO nanosheets with hierarchically porous structures at 550℃. Pyramid-like ZnO was synthesized using ammonium as the homogeneous precipitant and it contained many radial flat-tipped hexagonal ZnO prisms originated growth along [0 0 0 1] direction. The XRD and TEM results revealed that great crystallinity was observed with wurtzite structure and Au metallic phase with average size were about 15 nm. PL analyses exhibit a broad blue emission resulting from Zn interstitials. The PL intensity of gold-coated ZnO decreased due to the reduction of the electron/holes recombination rate. The analytical results of UV-visible diffuse reflection spectra (DRS) indicated that surface Plasma resonance bands in the range of 400 - 600 nm were observed in the Au/ZnO heterostructures due to the formation of nanometer-size Au. The adsorption edges had red–shift phenomenon by gold-deposited ZnO due to lower band gap of Au-coated ZnO. XPS, PL, Raman spectra, and DRS spectra have also revealed the interactions between Au nanoparticles and ZnO crystals and the formation of a new Fermi level. Photodegradation of Orange II dye under 365-nm UV and visible light irradiation has been performed to investigate the photocatalytic activities of Au/ZnO heterostructures and ZnO powder. The results show that Au-coated/ZnO could initiate the enhancement of photocatalytic decolorization due to the increase of electron-hole lifetime, thus increasing 1.2 – 2.6 times of decolorization efficiency less than 3 hs of irradiation time in comparison with uncoated ZnO. The plausible formation mechanisms of the microspheres and microflowers in two systems and the photocatalytic mechanisms have been suggested.
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Niknam, Mohamad. "Origin of NMR Spectral Features in MCM-41 at Low Hydrations." Thesis, 2010. http://hdl.handle.net/10012/5462.
Full textAbstract:
Although extensive literature exists on NMR of water in MCM-41, the origin of a number of NMR spectral features in this material had not been understood. Specifically, the
OH proton resonance observed in the dry material disappears completely as it is hydrated to 0.2 mono-layer hydration level. The purpose of this study was to gain insight into the physical basics for these spectral features and in the process broaden our understanding of behaviour/interactions of water molecules in porous material. First, measurements of MAS spectra as a function of temperature and hydration, at very low hydrations, made possible a definitive spectral peak assignment. Second, using 1D and 2D selective inversion recovery and magnetization exchange experiments, as well as MAS and non-MAS techniques, magnetization exchange between the water protons and surface OH group protons was quantified. The present results lead to the conclusion that chemical exchange is not responsible for producing the observed changes in proton spectra in MCM-41 as this material is hydrated up to the 0.2 mono-layer hydration level. This represents an important result as it is at odds with what is assumed in the literature in this connection and means that previous conclusions about hydration dynamics in this material need to be revisited. A dynamics model of water interaction with the surface OH hydration sites was introduced to explain the observed proton spectra. The model can successfully predict the observed chemical shifts and temperature dependent changes of proton spectra in the very low hydration MCM-41.
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Zhou, Xin-Lin, and 周欣麟. "Study in nano-scale porous silicon fabrication for silicon-on-insulator materials." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/06042385013106743621.
Full textAbstract:
碩士國立中央大學
機械工程研究所
97
Even with the mature semiconductor processing technology, the Moore’s Law is difficult to keep up with the necessity. The Silicon on Insulator (SOI) has become a material to solve the leakage effect when the process is in the scale of nanometer. Recently, Smart-Cut® is a common means for manufacturing the SOI. By applying the high dosage of hydrogen ions and implanting them into the silicon wafers, followed with wafer bonding process and high temperature annealing, the hydrogen ions gather and finishe the purpose of layer transfer. This thesis is in reference to fabricating a buried porous silicon layer under a capping silicon layer by using electrochemical etching. With certain parameters, the heavily doped P-type silicon wafer is etched by electrochemical method to cause the dissolving reaction and produce the porous layer. Under the capping silicon layer, Crevices are existent in the porous layer. In the later process, a small stress is applied on the creviced zones to cause the layer split along the crevices. It provides another approach to fabricate SOI material by using this method.
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Omar, Haneen. "Design and Synthesis of Porous Smart Materials for Biomedical Applications." Diss., 2018. http://hdl.handle.net/10754/630095.
Full textAbstract:
Porous materials have garnered significant interest within scientific community
mainly because of the possibility of engineering their pores for selective applications.
Currently, much research has focused on improving the therapeutic indices of the active
pharmaceutical ingredients engineered with nanoparticles.
The main goal of this dissertation is to prepare targetable and biodegradable
silica/organosilica nanoparticles for biomedical applications with a special focus on
engineering particle pores.
Herein, the design of biodegradable silica-iron oxide hybrid nanovectors with large
mesopores for large protein delivery in cancer cells is described. The mesopores of the
nanomaterials span 20 to 60 nm in diameter, and post-functionalization allowed the
electrostatic immobilization of large proteins (e.g., mTFP-Ferritin, ~534 kDa). The
presence of iron oxide nanophases allowed for the rapid biodegradation of the carrier in
fetal bovine serum as well as magnetic responsiveness. The nanovectors released large
protein cargos in aqueous solution under acidic pH or magnetic stimuli. The delivery of
large proteins was then autonomously achieved in cancer cells via the silica-iron oxide
nanovectors, which is thus promising for biomedical applications.
Next, the influence of competing noncovalent interactions in the pore walls on the
biodegradation of organosilica frameworks for drug delivery applications is studied.
Enzymatically-degradable azo-bridged organosilica nanoparticles were prepared and
then loaded with the anticancer drug doxorubicin (DOX). Controllable drug release was
observed only upon the stimuli-mediated degradation of azo-bridged organosilica
nanoparticles in the presence of azoreductase enzyme triggers or under hypoxia
conditions. These results demonstrated that azo-bridged organosilica nanoparticles are
biocompatible, biodegradable drug carriers and that cell specificity can be achieved both
in vitro and in vivo. Overall, the results support the importance of studying self-assembly
patterns in hybrid frameworks to better engineer the next generation of dynamic or “soft”
porous materials.
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Lee, Yueh-Jian, and 李粵堅. "Optical studies of the rare-earth-doped InGaAsP epilayers and meso-porous siliceous nano-materials." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/10429378256390859054.
Full textAbstract:
博士中原大學
應用物理研究所
92
This thesis studies the optical properties of the rare-earth doped InGaAsP epilayers and mesoporous materials. Different optical techniques such as photoluminescence (PL), photoconductivity (PC), contactless electroreflectance (CER), micro-Raman, polarized PL, PL excitation measurements are carried out to investigate the physical properties of the rare-earth doped InGaAsP epilayers and mesoporous materials. These results are presented in the following parts: (1) Influence of rare-earth elements doping on the optical properties of quaternary InGaAsP epitaxial layers: The PL, PC, and CER measurements were used to study the influence of rare-earth doping on the optical properties of InGaAsP layers grown by liquid phase epitaxy (LPE). Both the full width at half maximum (FWHM) of PL and the broadening parameter of CER were found to reduce as the doping amount of Ho element increases. The absorption tails were analyzed with the Urbach tail model and the Urbach energies were obtained from these fits. It is found that the Urbach energy decreases with increasing the doping amount of Ho elements, indicating the Ho doping leads to the decrease of impurity concentrations. The Nd-deoped InGaAsP layers exhibit the similar results and the narrowest value of the FWHM of PL peak is 7.5 meV with Nd of 0.031 wt%. We demonstrate that the introduction of the rare-earth elements can greatly reduce the residual impurities of LPE-grown layers. (2) Large-lattice-relaxation model for persistent photoconductivity in quaternary InGaAsP epitaxial layers: We report the first observation of persistent photoconductivity (PPC) in In1-xGaxAsyP1-y epilayers. Under the excitation-energy, temperature, and alloy composition dependence of the PPC effects, it is found that the lattice relaxation of DX-like impurity is responsible for PPC in In1-xGaxAsyP1-y. PPC was also investigated in Ho-doped InGaAsP epilayers with Ho concentrations in the range of 0-0.15 wt%. As the Ho doping increases, the decay-time constant and the electron-capture barrier were found to decrease. We suggest that the introduced Ho elements may chemically react with donor impurities, suppressing lattice relaxation and hence reducing the electron-capture barrier. Also, the rare earth doping is demonstrated to be an effective method of improving the quality of InGaAsP epilayers. (3) Raman scattering study of rare-earth elements doped InGaAsP epilayers: Raman scattering measurements have been used to study the structural properties of the rare-earth doped InGaAsP epilayers. Using a spatial correlation model, we found the asymmetric broadening of lineshape of the Raman signal is not influenced by the rare-earth doping. It indicates that no large amounts of the rare-earth elements are being incorporated into the epitaxial layers during the purification. (4) Red-light emission in MCM-41 and MCM-48 meso-porous nanostructure: PL was used to study the emission of light from siliceous MCM-41 and MCM-48 that has undergone rapid thermal annealing (RTA). Two PL bands were observed at 1.9 and 2.16 eV and assigned to the non-bridging oxygen hole centers (NBOHCs) and the NBOHCs associated with broken bonds, respectively. The PL intensity is enhanced after RTA. Based on the surface chemistry, the enhancement is explained by the generation of NBOHCs that originates from the hydrogen-bonded and single silanol groups on the MCM-41 and MCM-48 surfaces. The PL intensity degrades with time during photoexcitation. The dominant mechanism of PL degradation involves the formation of the chemisorbed oxygen-related complexes (probably O2－ molecules) on the surface, which are adsorbed onto the surface and act as an efficient quencher of PL. (5) Blue-green photoluminescence in MCM-41 meso-porous nanotubes: Different PL techniques have been used to study the blue-green emission from siliceous MCM-41. It is found that the intensity of the blue-green PL is enhanced after RTA. This enhancement is explained by the generation of the two-fold coordinated Si centers and the non-bridge oxygen hole centers according to the surface properties of MCM-41. Through the analysis of PL with RTA, polarized PL, and PL excitation, we suggest that the triplet-to-singlet transition of two-fold coordinated silicon centers is responsible for the blue-green PL in MCM-41. In addition, we suggest a model to explain the temperature dependence of the carrier time constant and the PL intensity.
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Che, Mu-Lung, and 車牧龍. "Study on the structure-property relationship of porous low-k dielectrics based on novel hybrid and nano-clustering materials." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/06319238663891195851.
Full textAbstract:
博士國立交通大學
材料科學與工程學系
100
This work examines the structure-property relationship of porous low-k dielectrics such as novel MSQ/high-temperature porogen hybrid materials and nano-clustering materials, and explores their integration feasibility for future technology node. Specifically, the effect of porogen structure on the structure-property relationship in MSQ/porogen hybrid films and their corresponding porous films by using a post-integration porogen removal scheme is investigated. Poly(styrene-b-4-vinylpyridine) containing di-block structure and pyridine polar group possesses higher moisture uptake and k-value in the hybrid films as compared to poly(styrene-block-butadiene-block-styrene) with symmetrical structure and non-polar groups. Moreover, the moisture uptake behavior in both as-prepared hybrid films is in physical sorption mode based on their reversible adsorption-desorption curve measured by quartz-crystal-microbalance. After porogen removal, the k-values of porous films are favorably not influenced by porogen structures. The k-value decreases from 2.89 to 2.44 when a porosity of 40.1 vol% is introduced into a dense MSQ matrix. Furthermore, the moduli of the hybrid films were found to be higher than their porous forms, and even better than the dense MSQ film, for porogen loading below a critical level (~69.5 vol%). This could be attributed to their enhanced degree of crosslinking in MSQ as evidenced by the network/cage structural ratios. Besides, high-temperature porogen plays different roles during the crosslinking of MSQ depending on its loadings. In our study, with immediate loading at 16.7 vol%, PS-b-P4VP can serve as plasticizer to enhance the degree of crosslinking, but at a large loading >16.7 vol%, it becomes a steric hindrance reducing the degree of crosslinking. On the other hand, a methyltrimethoxysilane (MTMS) modified silica zeolite (MSZ) film was prepared using a high ratio of MTMS/tetraethyl orthosilicate (TEOS) to study the structure-property relationship. The study investigated the effect of MTMS addition on the low-k matrix structure, elastic modulus, and pore geometry. High MTMS loading reduced the k-value of MSZ film down to 2.0, but yielded a lower elastic modulus, 2.7 GPa. Based on grazing-incidence small-angle X-ray scattering (GISAXS) analysis, the pore geometry of the MSZ film was found to be small but elliptical (Rin-plane ~3.75 nm; Rout-of-plane ~3.04 nm). The elliptical pore shape was formed by a collapse of film structure at 150–160°C as a result of ~32% thickness shrinkage due to the decomposition of tetra-n-propylammonium hydroxide (TPAOH), a structure directing catalyst, and due to a large degree of crosslinking reaction in the silica matrix. Combining GISAXS, 29Si-NMR, and FT-IR results, we propose that the lower elastic modulus was caused by the incorporation of a large amount of methyl groups from the MTMS precursor and the elliptic pores.
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Mani, Biswas Mousumi. "Theoretical Investigations on Nanoporpus Materials and Ionic Liquids for Energy Storage." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-12-9737.
Full textAbstract:
In the current context of rapidly depleting petroleum resources and growing environmental concerns, it is important to develop materials to harvest and store energy from renewable and sustainable sources. Hydrogen has the potential to be an alternative energy source, since it has higher energy content than petroleum. However, since hydrogen has very low volumetric energy density, hence it is important to design nano porous materials which can efficiently store large volumes of hydrogen gas by adsorption. In this regard carbon nanotube and Metal Organic Framework (MOFs) based materials are worth studying.
Ionic liquids (IL) are potential electrolytes that can improve energy storage capacity and safety in Li ion batteries. Therefore it is important to understand IL's thermodynamic and transport properties, especially when it is in contact with electrode surface and mixed with Li salt, as happens in the battery application. This dissertation presents computation and simulation based studies on:
1. Hydrogen storage in carbon nanotube scaffold.
2. Mechanical property and stability of various nanoporous Metal Organic Frameworks.
3. Thermodynamic and transport properties of [BMIM][BF4] ionic liquid in bulk, in Li Salt mixture, on graphite surface and under nanoconfinement.
In the first study, we report the effects of carbon nanotube diameter, tube chirality, tube spacer distance, tube functionalization and presence of Li on hydrogen sorption capacity and thermodynamics at different temperature and pressure. In the second one, we observe high pressure induced structural transformation of 6 isoreticular MOFs: IRMOF-1. IRMOF-3, IRMOF-6, IRMOF-8, IRMOF-10 and IRMOF-14, explore the deformation mechanism and effect of Hydrogen inside crystal lattice. In the third study, we observe the equilibrium thermodynamic and transport properties of [BMIM][BF4] ionic liquid. The temperature dependence of ion diffusion, conductivity, dielectric constant, dipole relaxation time and viscosity have been observed and found similar behavior to those of supercooled liquid. The ion diffusion on graphite surfaces and under nanoconfinement was found to be higher compared to those in bulk.
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yuan, ching-yao, and 袁敬堯. "The Preparation and Properties of Silica-Containing Nano Materials by Sol-Gel Method：(1)Porous Materials Using Ionic Liquids as Solvent (2) Solid Polymer Electrolyte Based on PEG/Polysilsesquioxanes (3) Flame Retardant Phosphazene/Silica-Containing PMMA." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/18215511659654516297.
Full textAbstract:
博士中原大學
化學研究所
91
This research is to investigate three kinds of new novel silicon-containing nano-materials prepared via sol-gel method. It is divided into three parts. Part 1. Preparation of mesoporous materials using ionic liquids as solvents and templates This part included three sections: Section 1: In this section, a new methodology, without the supercritical drying step, has been developed by using ionic liquids as solvents to prepare silica aerogels and organosilica aerogels via sol-gel reactions of tetramethylorthosilicate, bis(triethoxysilyl)ethane and bis(triethoxysilyl)benzene, respectively. In addition, the modification agents, NH2(CH2)3Si(OMe)3, NH2CH2CH2NH(CH2)3Si(OMe)3, CH3Si(OMe)3 and C6H5Si(OMe)3, have been successfully incorporated into the silica and the organosilica aerogel matrixes on a molecular level. The synthetic conditions have been systematically studied and optimized. For all the aerogels prepared above, their pore structures have been studied in detail by Transmission Electron Microscopy (TEM), X-ray diffraction and Brunauer-Emmett-Teller (BET) measurement. The relationship between the ionic liquid concentration and the pore parameters has been established. The results indicated that all the aerogels prepared in the study exhibit type IV isotherms and mesoporosity with a pore surface area larger than 600m2/g and pore volume over 2cm3/g. The surface areas and the pore volumes of all the modified aerogels decrease with increasing the content of the modification agent. It was found that the amino group modified aerogels were good absorbents for Cu2+ and Zn2+ ions. The efficiency of the absorption was as high as 99%. The alkyl group modified aerogels have lower water wettability than the unmodified aerogels. With meso-sized pore structure the aerogels are also anticipated to be used as catalyst support, host for enzymes and other proteins, and material for controlled drug delivery. Section 2: The nano-structured mesoporous photocatalysts, titania and silica-titania binary have also been successfully synthesized by using ionic liquids as template (or pore-forming agent) via sol-gel reactions of tetrabutyl titanate alone and with tetraethylorthosilicate, respectively, followed by removing the ionic liquids by extraction with acetonitrile. The powder X-ray diffraction patterns reveal that both the as-prepared mesoporous TiO2 and the mesoporous SiO2-TiO2 binary systems have anatase structures. The BET results showed that both have high surface area (500~800 m2/g) and large diameter of skeletal particles (20~50nm). Section 3: A new cationic surfactant, 1-methyl-hexadecane-imidazole bromide synthesized from 1-methylimidazole and 1-bromohexadecane, was used as template to prepare the mesoporous silica MCM-41. Periodic arrangement of mesoscopically ordered pores with 2-d hexagonal symmetry was observed by TEM micrograph and X-ray diffraction. The BET measurement of the MCM-41 showed that the surface area was as high as 1200m2/g, the total pore volume was 1.048cm3/g and the pore diameter was 27.8 Å, though no micropore volume was found. Part 2 Physical and Electrochemical Properties of Low Molecular Weight Poly (ethylene glycol)s-Bridged Polysilsesquioxane Organic-Inorganic Composite Electrolytes via Sol-Gel Process A new class of ionic conducting organic/inorganic hybrid composite electrolyte with high conductivity, better electrochemical stability and mechanical behavior was prepared through the sol-gel reaction between ethylene-bridged polysilsesquioxane and poly (ethylene glycol). The composite electrolyte with 0.05 LiClO4 per poly(ethylene glycol) repeat unit has the best conductivity of up to 10-4 Scm-1 at room temperature with the transference number up to 0.48 and the electrochemical stability window as high as 5.5V vs. Li/Li+. Moreover, the effect of the PEG chain length on the properties of composite electrolyte has been analyzed. The interactions between ions and polymer in the composite electrolyte in the presence of LiClO4 have been investigated by means of FT-IR, DSC and TGA measurements. The results demonstrated that the interactions of Li+ ions with the ether oxygen of the PEG, and the formation of transient cross-links with LiClO4 resulted in an increase in Tg. The VTF-type behavior of ionic conductivity with temperature implied that the diffusion of charge carrier was assisted by the segmental motions of the polymer chains. Part 3 Preparation and Properties of Novel Flame Retardant Materials based on Phosphorus, Nitrogen and Silicon for PMMA by Sol-Gel Technique A free-OH-contained cyclotriphosphazene, N3P3(OC6H4OH)6, HPP, has been synthesized and incorporated with various amount of silica and PMMA to form hybrids by sol-gel technique. The characterization and properties of the hybrids were investigated by FTIR, solid-state 29Si NMR, TGA, DSC, LOI and SEM/EDX measurements. The results indicated that the hybrids were well-hybridized, transparent materials caused by the formation of the covalent bonding between HPP and silica and the hydrogen bonding between the unreacted hydroxyl group on HPP/SiO2 and the carbonyl groups of PMMA polymer. The thermal degradation temperature up to above 300oC and LOI value up to 39 were obtained, indicating that compared to PMMA, the thermal stability and the flame retardancy of the hybrids with proper ratio of HPP and SiO2 were greatly improved.
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Lim, Cheol Woong. "Mathematical analysis of the lithium ion transport in lithium ion batteries using three dimensional reconstructed electrodes." 2012. http://hdl.handle.net/1805/3419.
Full textAbstract:
Indiana University-Purdue University Indianapolis (IUPUI)Computational analysis of lithium ion batteries has been improved since Newman and et al. suggested the porous electrode theory. It assumed the electrode as a simple structure of homogeneous spherical particles. Bruggeman relationship which characterizes porous material by a simple equation was adopted in the homogeneous electrode model instead of the electrode morphology. To improve the prediction of a cell performance, the numerical analysis requires the realistic microstructure of the cell. Based on the experimentally determined microstructure of the positive and negative electrodes of a lithium ion battery (LIB) using x-ray micro/nano-CT technology, three dimensional (3D) simulations have been presented in this research. Tortuosity of the microstructures has been calculated by a linear diffusion equation to characterize the 3D morphology. The obtained tortuosity and porosity results pointed out that the Bruggeman relationship is not sufficiently estimate the tortuosity by the porosity of electrodes. We studied the diffusion-induced stress numerically based on realistic morphology of reconstructed particles during the lithium ion intercalation process. Diffusion-induced stresses were simulated at different C rates under galvonostatic conditions and compared with spherical particles. The simulation results showed that the intercalation stresses of particles depend on their geometric characteristics. The highest von Mises stress and tresca stress in a real particle are several times higher than the stresses in a spherical particle with the same volume. With the reconstructed positive electrode structure, local effects in the LIB cathode electrode during galvanostatic discharge process have been studied. The simulation results reported that large current density usually occurs at the joints between cathode active material particles and in the small channels in electrolyte, which will generate high electric joule power. By using the 3D real image of a LIB cathode electrode, numerical simulation results revealed that the spatial distribution of variable fields such as concentration, voltage, reaction rate, overpotential, and etc. in the cathode electrode are complicated and non-uniform, especially at high discharge rates.
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Pan, Han-Chung, and 潘漢聰. "the research of the silica porous nano-composite material." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/70528877556608206762.
Full textAbstract:
碩士國立臺灣大學
材料科學與工程學研究所
92
The main purpose of this research was to study the processing, structure and physical properties of cetyltrimethylammonium bromide (CTABr) templated nano-porous silicate material. We altered the ratios of cetyltrimethylammonium bromide, tetramethoxysilane, water and pH value in the formulations to investigate the suitable condition for the the formation of micelles and their templated mesostructural silicate film. There are three factors for the formation of surfactant-templated nano-porous structure needed to be considered. First, the concentration effect of the surfactant: when the concentration of the surfactant exceeds CMC, surfactant molecules can aggregate to form micelles. Second, the effect of the pH value: when the amount of HCl is increased, micelles interact wih silicate stronger, resulting in severe aggragation between micelles and silicate. Third, the concentration effect of the silicate: silicate is regarded as an anionic polyelectorolyte which can interact with micelles through the cationic amine groups of CTABr. The concentration of silicate should be high enough to cover the surface of micelles and further divide the aggregate of micelles into an array of nanotubes. After freeze-drying the solution into powders, we calcinated the powders and used small angle x-ray scattering, TEM, XRD, BET, AFM to investigate their meso-porous structures and estimate their pore size distribution. Besides, we attempted to employ pyrene as a fluorescence sensor to investigate the micelle formation and their aggregation condition after the incorporation of silicate. Because the fluorescence properties of pyrene show strong solvation effects, we could use it to determine the critical micelle concentration of the surfactant as well as to study the initial formation of mesoporous structure in solutions.
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Lun, Chen Wei, and 陳威綸. "The study and analysis of nano-scale pores in porous silicon material." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/98465035340404295864.
Full textAbstract:
碩士中國文化大學
材料科學與奈米科技研究所
94
In this study, the porous silicon (PS) films are fabricated by electrochemical anodization method. Various experimental parameters, such as etching current density, etching time and HF concentration, are investigated. Photoluminescence (PL), scanning electron microscope (SEM), energy dispersive spectrometer (EDS) mapping and Fourier transform infrared spectroscopy (FTIR) are used to analyze the film characteristics in the PS. N-type PS is difficult to form by conventional method for the lack of holes. However, with the forward biased P-N junction, sufficient holes can drift from P layer to N layer and hence the N-type PS can be easily formed. In addition, the thickness of P-type layer influences the etching result. From P-L spectrum, it can be found that etching on the N/P sample produces better PL emission and blue-shifting. Deep and straight shape pores can be obtained. The morphology, cross section view, porosity, PL and EDX analysis are investigated and compared with conventional method.
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Peng, Guan-Jane, and 彭冠甄. "Study on Preparation and Thermal Physical Properties of Porous Nano-Particles/Polyurethane Composite Material." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/58685906665473969320.
Full textAbstract:
碩士國立雲林科技大學
化學工程與材料工程研究所
99
The preparation of Porous Nano-Particles/Polyurethane (PU) composites material has become the main class in the study, and the study is divided into two parts ( part A,part B ), part A is about preparation of aerogel/PU ; part B concerns with preparation of Polyhedral Oligomereic Silsesquioxane (POSS)-polyurethane composite materials. Discussions on the nano-particles in the substrate of the thermal properties ( included heat capacity: Cp, thermal conductivity: K ) and cenalssis on content and dispersion effect the composite thermal properties were carried out. Aerogel surface functional group was charaetenzed by ( FT-IR ), mesoporous structure was analyzed by BET; the dispersion of nano-particles in the substrate was gained by FE-SEM. Thermal properties ( Cp, K, ) was measured by DSC and Hot Disk. The results showed the dispersion of modified aerogel in the substrate is better than that of non-modified aerogel in the substrate; when the aerogel composition was added to 35 vol.%, K is compared to the substrate PU and they were to reduced 48%. When POSS added to 15.4 wt%, K is compared to the substrate PU and they were to reduced 3 times. Based on the measurement and analysis of the results, the study developed two series of materials is expected to be used as an insulation coating material.
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Kuo, Chin-Ya, and 郭瀞雅. "Natural nano-porous filter material as a new high-efficiency natural adsorbent to remove textile dyes." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/bz5fa4.
Full textAbstract:
碩士義守大學
生物科技學系
107
Most textile dyes are harmful to the environment and may cause cancer. The dyes are very toxic, harmful, and can cause a large amount of environmentally toxic waste, posing a serious hazard to the public. Nowadays, scientists have developed various chemical and physical processes to remove different dyes, for example: ozone oxidation, electrochemical methods, chemical coagulation, hypochlorite oxidation and adsorption to remove dyes from wastewater. According to previous researches, adsorption was an effective method for removing dyes from wastewater, which was an alternative to other expensive treatments. Previous literatures have been shown that the use of natural adsorbents would remove textile dyes by the advantages of their economic appeal, inexpensive and availability. To deal with the similar pollution of textile printing and dyeing wastewater, we used the natural nanoporous filter material in the challenged adsorption tests. By the different concentrations of the dye liquid, the adsorbent was uniformly distributed and absorbed with different times in this tests, and then had been measured by a spectrophotometer. In addition, the different environmental effects of adsorbent dosages and temperatures on the dye removal by the nanoporous pore filter were also investigated. Our goal will be to develop a novel and natural adsorbents with mathematic simulation models that would help to set up the industrial absorption condition with low cost and even lower secondary pollution.