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Pugh, Dylan Vicente. "Nanoporous Platinum." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/27256.
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Dealloying is a corrosion process in which one or more elements are selectively removed from an alloy leading to a 3-dimensional porous structure of the more noble element(s). These porous structures have been known to cause stress corrosion cracking in noble metal alloy systems but more recent interest in using the corrosion process to produce porous metals has developed. Applications for these structures range from high surface area electrodes for biomedical sensors to use as skeletal structures for fundamental studies (e.g. low temperature heat exchangers or sensitivity of surface diffusivity to chemical environment). In this work we will review our current understanding of alloy corrosion including our most recent results demonstrating a more accurate method for calculating alloy critical potential based on potential hold experiments. The critical potentials calculated through the potential hold method were â 0.030VMSE, 0.110VMSE, and 0.175VMSE for Cu80Pt20, Cu75Pt25 Cu71Pt29 respectively. We will present the use of porous metals for making surface diffusivity measurements in the Pt systems as a function of chemical environment. A review of the use of small angle neutron scattering to make accurate measurements of pore size is presented and the sensitivity of pore size to electrolyte, electrolyte composition, applied potential and temperature will be explained. The production of porous Pt with pore sizes ranging from 2-200nm is demonstrated.Ph. D.
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Nguyen, Thanh Xuan. "Characterization of nanoporous carbons /." [St. Lucia, Qld.], 2006. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe19108.pdf.
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Wilke, Kyle (Kyle L. ). "Evaporation from nanoporous membranes." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104571.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 56-58).
Cooling demands of advanced electronics are increasing rapidly, often exceeding capabilities of conventional thermal management techniques. Thin film evaporation has emerged as one of the most promising thermal management solutions. High heat transfer rates can be achieved in thin films of liquids due to a small conduction resistance through the film to the evaporating interface. In this thesis, we investigated evaporation from nanoporous membranes. The capillary wicking of the nanopores supplies liquid to the evaporating interface, passively maintaining the thin film. Different evaporation regimes were predicted through modeling and were demonstrated experimentally. Good agreement was shown between the predicted and observed transitions between regimes. Improved heat transfer performance was demonstrated in the pore level evaporation regime over other regimes, with heat transfer rates up to one order of magnitude larger for a given superheat in comparison to the flooding regime. An improved experimental setup for investigating thin film evaporation from nanopores was developed, where a biphilic membrane, i.e., a membrane with two wetting behaviors, was used for enhanced experimental control to allow characterization of the importance of different design parameters. This improved setup was then used to demonstrate the dependence of thin film evaporation on the location of the meniscus within the nanopores. This dependence on meniscus location within the pore was also shown to increase with increasing superheat. We observed a 46% reduction in heat transfer rates at a superheat of 15 °C for an L* of 14.67 compared to an L* of 2, where L* is the ratio of the depth of the meniscus within the pore to the pore radius. This work provides practical insights for the design of devices based on nanoporous evaporation. Heat transfer regimes can be predicted based on fluid supply conditions, evaporative heat flux, and membrane geometry. Furthermore, the biphilic membrane serves as a valuable experimental platform for testing the role of membrane geometry on heat transfer performance in the pore level evaporation regime. Future work will focus on demonstrating the importance of different parameters and using experimental results to either validate existing models for evaporation from nanopores or develop more suitable ones.
by Kyle Wilke.
S.M.
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Crowson, Douglas A. "Stability of Nanoporous Metals." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/28111.
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A study of the stability of bicontinuous nanoporous metals is presented. Atomic scale simulations are used to probe the dominant mechanisms of geometric relaxation in these materials. A method is presented for generating model bicontinuous metal / void structures for use in atomistic simulations of bicontinuous nanoporous solids. The structures are generated with periodic boundary conditions using a phase-field model to simulate the spinodal decomposition of an ideal system. One phase in the model is then associated with the pore volume while the other phase is associated with the metal ligaments. Small angle neutron scattering was used to quantitatively compare experimental samples to those generated by the phase field method.
EAM results using model structures with experimentally accessible length scales are presented which demonstrate the potential of such simulations in understanding the behavior of nanoporous metals. Simulated relaxations of these structures, as well as the relaxation of model spherical clusters, indicate that the surface relaxation effect dominates the overall dimensional relaxation of np-metals post processing. Capillary effects play a secondary role in the overall relaxation. The simulation results presented also identify a maximum surface area to volume ratio necessary to maintain mechanical stability beyond which the pore structure collapses.Ph. D.
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Cooney, D. T. P. "Nanoporous materials from block copolymers." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597952.
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This project assesses the potential for block copolymers (BCPs) to be used in making nanoporous membranes. BCPs self assemble to produce structured phase morphologies based on their molecular composition. One such structure is composed of cylinders of one polymer phase in a matrix of another. It is proposed that nanoporous products could be produced by selectivity removing the material forming the cylindrical phase in an aligned BCP sample. Methods of inducing good phase alignment in BCP samples are reviewed. The effects of high shear rates on the orientation of a cylindrical phase formed by a triblock copolymer are investigated using the Cambridge Multipass Rheometer and a customised X-ray diffraction system. A new X-ray collection technique is developed and used to show that high shear rates can destroy phase orientation in a BCP melt. BCP etching is investigated. The removal of a cylindrical poly(lactide) phase in a P(S-b-LA) BCP by hydrolysis is examined. The method is shown to produce complete removal of the PLA phase, with the etch considered to be reaction limited. Diffusion of acid and alkali through such etched samples is observed in a specially designed cell. Transport in aqueous conditions is established through samples up to 7 mm long, proving pore continuity in the material and establishing the practical validity of the proposed idea. Thin films of BCP aligned using electric fields are obtained and etched. Acid transport through the films indicates porosity has been introduced. Size exclusion experiments using gold colloids prove that small particles are transmitted by these films, whilst large particles are retained. These experiments establish that size separation could be conducted using BCP products, as proposed, and form the basis for future work in developing such products.
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Preuss, Frida, Julia Asp, Sofia Larsson, and Stephanie Kylington. "Separation of Nanoporous Silica Particles." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-277106.
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In this study a sample of particles in a size region of 0.05-10 μm were run through a centrifugation process with the ambition to make it monodisperse. The product requirements were stated as follows, particles within the size range of 2 to 3.8 μm should be isolated and separated from the sample with a D90/D10 < 1.4 where the D90/D50/D10 values should be approximately 3.8 μm/2.5 μm/2 μm. It was found that two layers of sucrose with a 50/50 volume distribution of 45w% sucrose solution and 60w% sucrose solution respectively, was the most efficient density gradient arrangement for separation of this particular sample. The optimal time and RPM combination was found to be 5 min 3000 RPM with a fast acceleration and slower deceleration, ratio 9:6. Two centrifugation rounds on the same sample improved D90/D10 drastically. The effect of centrifugation rounds on D90/D10 was not investigated further than 3 rounds, however this would be a good starting point for further studies. The upscaled test runs indicated a positive result, i.e. the yields with respect to both mass and purity were reproducible. It is worth mentioning that the upscale was only in the volume, sample load volume and surface area factors. The gradient height or particle travel distance remained the same.
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Odunsi, Oluwatoni Yewande. "Hydrogen storage on nanoporous carbons." Thesis, University of Bath, 2007. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437723.
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Morgado, Lopes André. "Reactive transport through nanoporous materials." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0560/document.
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Le but de cette thèse est d’étudier le comportement des asphaltènes dans des condition de hydrotraitement, y compris les propriétés de transport et d’adsorption. La chromatographie d'exclusion stérique inverse (ISEC) ainsi que la spectroscopie d'impédance sont utilisées pour déterminer des paramètres topologiques de solides poreux d’alumine (porosité, taille de pores, tortuosité). Des coefficients de diffusion effectifs de polystyrènes de différentes tailles sont aussi étudiés par chromatographie liquide en conditions non-adsorbantes: les molécules de petites tailles pénètrent plus profondément dans le milieu poreux donc elles prennent plus de temps pour traverser la colonne, tandis que les molécules ayant une taille supérieure à la taille du pore ne sondent que la macroporosité. Avec l'utilisation des méthodes dynamique et «peak parking», il est possible de modéliser le transport des molécules de différentes tailles, et cela aidera à prédire le comportement de molécules d’une taille quelconque. Les colonnes ont été assemblées au laboratoire à partir de poudres et de monolithes d’alumine. Les caractéristiques d'adsorption des asphaltènes modèles sont déterminées et comparées avec une fraction d’asphaltènes extraite d’un brut. Un phénomène de dimérisation ainsi qu’une très forte adsorption sur la surface de l’alumine sont observés avec la molécule modèle. La méthode dynamique a été utilisée avec des colonnes courtes dans des conditions de saturation. Une influence apparente du débit dans l’importance et le mécanisme d’adsorption a pu être constatéeThis work aims to study the complex behaviors of asphaltenes within the hydrotreatment catalytic porous system including transport properties and adsorption. Inverse size-exclusion chromatography (ISEC) and impedance spectroscopy are used to determine the topological characteristics of different alumina porous solids (porosity, pore size, tortuosity). The effective diffusion coefficient of polystyrenes of different sizes was studied via chromatography in non-adsorbing conditions. Elution peaks are used to determine the effect of molecule size on the accessible pore volume and the transport properties therein: molecules of relatively small sizes penetrate further into the porous medium, thus taking more time to navigate the chromatographic setup, while larger molecules traverse much faster, through the macroporosity. The liquid chromatography technique is divided in two different methods. Both methods yield diffusion coefficient values which are modelled, predicting the behavior of molecules of any size. Columns were assembled manually from alumina powders or monoliths. A synthesized asphaltene model molecule was used and its adsorption behavior was determined and compared to an asphaltene fraction recovered from crude oil. The asphaltene model molecule shows a dimerization behavior as well as extremely strong interactions with the alumina surface. Dynamic method was attempted in short alumina columns at saturation conditions and an apparent influence of the flow rate on the extent and mechanics of adsorption was observed
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Freeman, Christopher J. "Biosensing and Catalysis Applications of Nanoporous Gold (NPG) and Platinum-Speckled Nanoporous Gold (NPG-Pt) Electrodes." VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5473.
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The importance of porous materials has risen substantially in the last few decades due to their ability to reduce the size and cost of bioanalytical devices and fuel cells. First, this work aims to describe the fabrication of nanoporous gold (NPG) electrodes that are resistant to electrode passivation due to fibrinogen biofouling in redox solutions. The effect on potentiometric and voltammetric experiments was seen as a deviation from ideal behavior on planar gold electrodes, whereas NPG electrodes were consistently behaving in a Nernstian fashion at low concentrations of ferri-ferrocyanide (£100 mM). An improvement in electrode behavior on NPG electrodes versus planar gold was seen in solutions containing ascorbic acid as well as blood plasma. Second, cost effective NPG electrodes were fabricated using a glass substrate to test the response in the presence of a variety of redox molecules. The optical transparency of these electrodes allowed for microdroplet measurements to be made using an inverted microscope in several redox solutions for validation and subsequent biological applicability. Nernstian behavior was demonstrated for all one- and two-electron transfer systems in both poised and unpoised solutions. All experiments were conducted using volumes between 280 and 1400 pL producing rapid results in less than one minute. Third, in order to decrease the requirement for complex instrumentation, microdroplet fabrication technique was used to create mini-nanoporous gold (mNPG) electrodes on glass capillary tubes. The cylindrical shape of the electrodes allowed for testing in sample volumes of 100 mL. The response to ferri-ferrocyanide, ascorbic acid, cysteine, and uric acid was then investigated with Nernstian behavior shown. However, the mNPG electrodes were insensitive to glucose and hydrogen peroxide. In order to increase the sensitivity of the electrodes, a minimal amount of platinum was electrodeposited onto the NPG surface using a low concentration of platinum salt (0.75 mM) for a short deposition time (2 seconds) producing a Nernstian response to both glucose and hydrogen peroxide. Lastly, to test the viability of crossover applications, the platinum incorporated NPG electrode was employed as a fuel cell anode material, testing their oxidation capability with methanol, ethanol, and formic acid.
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Bera, Chandan. "Thermo electric properties of nanocomposite materials." Phd thesis, Ecole Centrale Paris, 2010. http://tel.archives-ouvertes.fr/tel-00576360.
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Cette thèse présente une étude théorique du transport de chaleur dans les matériaux composites nano poreux et nano fils ainsi qu'une étude théorique des propriétés thermoélectriques de l'alliage Si0:8Ge0:2 confrontée à des mesures expérimentales réalisées pour une partie, dans le cadre de l'étude.La première étude démontre que les alliages poreux affichent des réductions de conductivité thermique à des dimensions de pores beaucoup plus grandes que les matériaux poreux non alliés de même porosité nominale. Si on considère une taille de pores de 1000nm, la conductivité thermique de l'alliage Si0:5Ge0:5 avec 0:1 de porosité est deux fois plus faible que la conductivité thermique d'un matériau non poreux, alors que les pores plus petits que 100 nm sont nécessaires pour obtenir la même réduction relative dans le Si ou Ge pur. Nos résultats indiquent que les alliages nano poreux devraient être avantageux devant les matériaux nano poreux non alliés, et ceux pour les applications nécessitant une faible conductivité thermique, tels que les nouveaux matériaux thermoélectriques.La deuxième étude théorique sur la conductance thermique de nano fils révèle l'effet de la structure sur le transport des phonons. Avec un modèle théorique qui considère la dépendance en fréquence du transport des phonons, nous sommes en mesure quantitativement de rendre compte des résultats expérimentaux sur des nano fils droits et coudés dans la gamme de température qui montre qu'un double coude sur un fil réduit sa conductance thermique de 40% à la température de 5K. Enfin, nous avons procédé à une approche théorique des propriétés thermoélectriques des alliages SiGe frittés, en les comparant aux mesures expérimentales nouvelles et antérieures, tout en évaluant leur potentiel d'amélioration. L'approche théorique a été validée par comparaison de la mobilité prévue et la conductivité thermique prévues, en faisant varier la quantité de Ge et les concentrations de dopage, dans une gamme de température comprise entre 300 et 1000K. Nos calculs suggèrent qu'une optimisation par rapport à l'état de l'art actuel est possible pour le matériau de type n et type p, conduisant potentiellement à une augmentation de 6% (5%) du ZT _a 1000K et 25% (4%) _a température ambiante. Même des améliorations plus grandes devraient être possibles si la probabilité de diffusion des phonons aux joints de grains pouvait être augmentée au-delà de sa valeur actuelle de 10%.
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Quintana, Puebla Alberto. "Enhanced magnetoelectric effects in electrolyte-gated nanoporous metallic alloy and dense metal oxide films." Doctoral thesis, Universitat Autònoma de Barcelona, 2018. http://hdl.handle.net/10803/663838.
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Esta tesis abarca el estudio de propiedades magnetoeléctricas en aleaciones magnéticas y metálicas nanoporosas, y en capas densas de óxidos de metales de transición.
La naturaleza interfacial de los procesos magnetoeléctricos ha hecho que históricamente el estudio de estos fenómenos se abordara en sistemas de elevada relación superficie/volumen, limitándose muchas veces a capas ultradelgadas (1-2 nm). En esta tesis, se postula una nueva forma de afrontar el estudio de estos procesos, basada en el uso de materiales nanoporosos los cuales se caracterizan por tener una relación superficie/volumen muy elevada y una pared de poro o ligamento de pocos nanómetros. De esta forma, se han obtenido efectos magnetoeléctricos en materiales cuyo grosor global supera el centenar de nanometros.
La síntesis de los materiales de interés se ha llevado a cabo por métodos de deposición electroquímica. Específicamente, se ha sacado partido de la formación de micelas al disolver copolímeros bloque en soluciones acuosas por encima de la concentración micelar crítica. Estas micelas quedan atrapadas durante el proceso de electrodeposición, actuando como agente moldeador. Usando este enfoque, se han podido sintetizar diferentes muestras de distintas morfologías y composiciones de la aleación cobre-níquel.
La aplicación de voltaje se ha realizado haciendo uso de electrolitos, aprovechando la formación de una doble capa eléctrica. Con la intención de obtener efectos magnetoeléctricos puros (acumulación de carga) y evitar procesos oxidativos simultáneos, se ha utilizado un electrolito orgánico aprótico. Con este método, se pueden obtener campos eléctricos del orden de centenares de MV/cm. Gracias a este elevado campo eléctrico, junto con la enrome relación superficie/volumen de los materiales nanoporosos, se ha obtenido una disminución de la coercitividad de una muestra nanoporosa de Cu25Ni75 en un 32 %. Simulaciones ab-initio atribuyen estos cambios a modificaciones en la energía de anisotropía magnética adscritos a la acumulación de cargas electrostáticas en la aleación.
En una segunda aproximación, se han realizado estudios de procesos de oxidación-reducción en medios acuosos (1M NaOH) controlados por voltaje, en este tipo de aleaciones. Después de aplicar potenciales positivos, se ha visto una modificación de un 33 % en la magnetización, debido a la oxidación selectiva del cobre en una muestra nanoporosa de Cu20Ni80. La oxidación resulta en una aleación enriquecida en níquel y, por ende, en una aleación con mayor momento magnético.
En esta tesis, también se ha demostrado la idoneidad de la técnica de deposición por capas atómicas para producir recubrimientos conformales en materiales nanoporosos. Se ha visto que esta técnica permite preservar la integridad morfológica y estructural de la capa activa, asentando así las bases para aplicaciones en estado sólido.
En la última parte de esta tesis, se ha demostrado la posibilidad de inducir ferromagnetismo mediante la aplicación de voltaje eléctrico en capas densas de Co3O4. El campo eléctrico aplicado da lugar a una migración iónica controlada, resultando en regiones ricas en oxígeno y otras en cobalto, estas últimas originando el ferromagnetismo. Este experimento es una de las primeras evidencias de movimiento iónico inducido por voltaje a temperatura ambiente y sin la necesidad de utilizar capas donadoras/aceptores de oxígeno (en otras palabras, sin fuentes o sumideros de oxígeno).This Thesis covers the study of the magnetoelectric response in nanoporous metallic alloy and transition metal oxide dense films. The interfacial nature of magnetoelectric processes, independently of its origin, has limited its study to ultrathin film configurations (usually 1-2 nm). Here we propose a novel approach to overcome this thickness limitation, thus achieving magnetoelectric response in materials whose overall thickness is larger than 100 nm. To accomplish this, we have employed nanoporous materials, with pore walls and ligands of very few nanometers, which are characterized by a large surface to volume ratio. These materials have been synthesized by micelle assisted electrodeposition. Micelles get trapped during the electrodeposition process thus acting as a soft templating agent, allowing us to synthesize nanoporous copper-nickel alloy films with tunable composition and morphology. Voltage application has been performed through electrolyte-gating, taking advantage of the generation of an electrical double layer in aprotic organic electrolytes which helps to avoid spurious oxidation processes. This method allows for the application of electric fields as high as hundreds of MV/cm. Thanks to the high electric field achieved, together with the ultrahigh surface area of nanoporous materials, a 32 % reduction in the coercivity of a Cu25Ni75 nanoporous film has been achieved. Ab-initio simulations attribute this large effect to changes in the magnetic anisotropy energy due to charge accumulation in the sample|electrolyte interface. In a second approach, the voltage control of redox processes has been studied in aqueous electrolytes (1M NaOH). After positive bias application up to a 33 % reduction in the magnetization has been achieved in a Cu20Ni80 nanoporous sample thanks to the selective Cu oxidation. The controlled oxidation process resulted in an enriched Ni alloy which possesses a larger magnetic moment. Moreover, we have demonstrated the suitability of atomic layer deposition to conformally coat the nanoporous alloys, preserving the morphology and structure, thus setting the basis for future solid state applications. In the last part of this Thesis, it has been demonstrated that, upon electric field application, a ferromagnetic response arises in a paramagnetic single Co3O4 layer, at room temperature. The applied voltage promotes the ionic diffusion, resulting in oxygen rich and cobalt rich regions, being the latter the responsible of the induced magnetic signal. This experiment is one of the first evidences of ionic motion at room temperature without the assistance of oxygen buffer layers such as Gd2O3 or HfO2.
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Topoglidis, Emmanuel. "Biosensors based on nanoporous TiO2 films." Thesis, Imperial College London, 2001. http://hdl.handle.net/10044/1/7573.
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Schofield, Eleanor Josephine. "Formation and characterisation of nanoporous materials." Thesis, Imperial College London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429052.
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Roche, Iain. "Nanoporous polymeric adsorbents for blood purification." Thesis, Loughborough University, 2009. https://dspace.lboro.ac.uk/2134/8143.
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This thesis is concerned with applying engineering principles to the use of polymeric nanoporous adsorbents for use in blood purification to obtain original knowledge. Styrene divinylbenzene copolymer nanoporous adsorbents offer a potential means to remove middle molecular (MM) sized molecules when in direct contact with blood. (Continues...).
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Gage, David Maxwell. "Fracture of nanoporous organosilicate thin films /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Brown, Jacob Leslie. "Vapour-liquid equilibria within nanoporous media." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/277690.
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This thesis is dedicated to the exploration of fluid phases confined in nanoporous materials using Nuclear Magnetic Resonance (NMR) techniques, with an aim to benefit catalysis research. Included in this report are studies of pure fluids and their mixtures, confined in titania and silica catalyst supports. These investigations are conducted at industrially-relevant, high-temperature (≥ 180 °C) and high-pressure conditions (up to 13 bar), made possible by a pilot-scale chemical reactor unit, designed to operate inside the strong magnetic fields of an NMR spectrometer. NMR spectroscopy, relaxation and pulsed field gradient (PFG) diffusion experiments were performed on each of the systems discussed in this report. Cyclohexane was initially studied inside a porous titania catalyst support at 188 °C and various pressures up to 13 bar. The adsorption and desorption processes of the cyclohexane were observed, revealing a number of previously unobserved phenomena. In addition to an overall, averaged diffusion coefficient, a slow diffusion coefficient was observed within the PFG NMR data attributable to surface diffusive processes occurring within the material. Additionally, T1 relaxation studies were found to provide experimental evidence for the differing configurations of adsorbed layers on the adsorption and desorption branch of the isotherm. Cyclohexane was subsequently studied alongside fluorobenzene in a series of silica catalyst supports of 6 nm, 10 nm and 20 nm pore size. In doing this, it was hoped that the multiple phenomena observed in the titania experiments might be deconvoluted, allowing a greater level of insight. The diffusivities of the fluids were found to differ significantly between the materials, and greater evidence was found of the slow-diffusing surface phase in each of the materials. Additionally, concentrations of cyclohexane and fluorobenzene in the gas and adsorbed layers inside the pore space were calculated via the results of the PFG NMR experiments, providing a map of confined phase behaviour. Competitive adsorption effects were found to become more significant, the smaller the pore size of the material. The results of the cyclohexane and fluorobenzene in silica studies were modelled, using approaches available in the literature, which were found to give varying levels of prediction. The data set acquired in this thesis was found to provide a useful standard, against which current and future models of confined phase behaviour might be verified.
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Hu, Yan. "Quantitative confocal imaging of nanoporous silica." Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/3106.
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Nanoporous materials have been widely used in the fields of biological and chemical sensing, chemical separation, heterogeneous catalysis and biomedicine due to their merits of high surface area-to-volume ratio, chemical and thermal stabilities, and flexible surface modification. However, as the nature of nanoporous materials, they are inherently heterogeneous in the micro- and nanoenvironments. The environmental heterogeneity plays a decisive role in determining the performance of various applications of nanoporous materials. In order to provide an in-depth understanding of the nanoporous materials, it is of great interest to investigate the environmental heterogeneity in them. Single molecule spectroscopy, combined the quantitative confocal fluorescence imaging which possesses the capability of optical sectioning, has demonstrated to be a powerful tool to approach the environmental heterogeneity inside nanoporous materials. Single molecule spectroscopy is an ultrasensitive technique for probing molecular transport and properties of individual molecules. This technique has been extensively used in the research of environmental heterogeneity in nanoporous materials since it removes the issues of ensemble averaging and directly approaches detailed information that is obscured in ensemble measurements. In order to proficiently interpret single molecule data, we developed a comprehensive methodology – single molecule counting – for characterizing molecular transport in nanoporous silica. With this methodology as a tool, the nanoenvironmental heterogeneity inside the nanopores of C18-derivatized silica particles was explored by probing single molecular diffusion inside the pores. By employing single molecule ratiometric spectroscopy and a solvatochromic fluorophore as viii reporter of local environment, the gradient in nanopolarity as well as the nanoviscosity along the C18 layer after the inclusion of solvent was uncovered. The chemical properties of solute molecules at the nanopore surface are ultimately controlled by the energetics of the solute-interface interactions. The imaging of distribution of energies would be a decisive approach to assess the fundamental heterogeneity of the interface. To this end, we investigated the ΔG distribution of C18-derivatized nanoporous silica particles with quantitative confocal imaging. The pixel-to-pixel and particle-to-particle analysis showed the existence of ΔG heterogeneity between particles as well as within individual particles. The heterogeneity in ΔG could be partially responsible for band broadening in chemical separations and significantly affect overall reaction yield when using nanoporous materials as solid support for heterogeneous catalysis.
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Svensson, Anna. "Nanocomposites made from nanoporous cellulose fibre." Licentiate thesis, KTH, Fiberteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-103342.
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This thesis explores how to use the dry nanoporous structure of cellulosic fibres in new types of composite materials. A large effort was also given on how to correctly characterize the structure of fibres where the wet structure has been preserved also in the dry state. Delignified wood fibres have an open fibrillar structure in their water-swollen state. In the present work, this open fibrillar structure was preserved in the dry state by performing a liquid exchange procedure and the samples were thereafter carefully dried with Ar(g). The samples of never-dried TEMPO-oxidized dissolving pulp had a specific surface area of 130 m2/g in the dry state, as measured using the Brunauer, Emmet, and Teller (BET) Nitrogen gas adsorption method. This open structure was also revealed using field emission scanning electron microscopy (FE-SEM). The water-swollen and dry open structures were thoroughly characterized for various pulps. A new method for determining the pore size of water-swollen delignified cellulosic fibres is presented. By combining the results from solid state nuclear magnetic resonance NMR, measuring the specific surface area [m2/g] in the water-swollen state, with fibre saturation point (FSP), measuring the pore volume of fibres in water-swollen state [mass water/mass fibre], the average pore size can be determined without the need of assuming a certain pore geometry. The dry nanoporous structure was then used as a scaffold for in-situ polymerization, to demonstrate how the properties of the fibrils in the fibre wall can be exploited without the need to disintegrate the fibre wall. Both poly(methylmethacrylate) (PMMA) and poly(butylacrylate) (PBA) were successfully used as the polymeric matrix, and both nanocomposites (i.e., fibre/PMMA and fibre/PBA) had a fibre content of approximately 20 w%. The structure of the composites was characterized using SEM and Atomic Force Microscopy (AFM) operated in the phase imaging mode. The AFM results indicate that the cellulose aggregates and polymeric matrix were successfully mixed on a nanoscale, creating a nanocomposite of interpenetrating polymer molecules and cellulose fibrils, rather than a microcomposite, when using microscopic cellulose fibres. The water absorption capacity of the nanocomposites was reduced significantly, indicating that almost all nanopores in the fibre wall were successfully filled with matrix polymer. The mechanical properties were investigated, showing the importance of nanosized reinforcement compared to fibres of micrometer size.QC 20121011
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Gomis, Berenguer Alicia. "Photochemical response of nanoporous carbons. Role as catalysts, photoelectrodes and additives to semiconductors." Doctoral thesis, Universidad de Alicante, 2016. http://hdl.handle.net/10045/63668.
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The main objective of this doctoral thesis is explore the origin of the nanoporous carbons photoactivity for studying their applications in different fields of research covering their use as photocatalysts for pollutants degradation as well as photoelectrodes for water photooxidation reaction, either by themselves or as additives coupled to a semiconductor in hybrid electrodes. The first stage of this study mainly consisted in investigating the photoactivity of carbon materials by themselves (in the absence of semiconductors) towards different reactions, aiming at linking their photochemical response with the carbon material nature in terms of porosity, surface chemistry, composition and structure. The exploration of the photoassisted degradation of phenol nanoconfined in the pore voids of several nanoporous carbons showed a positive effect of the tight packing of the molecule in the carbon material porosity. This indicated the role of confinement to boost fast interactions between the photogenerated charge carriers at carbon material surface and the molecule adsorbed inside pores. The irradiation wavelength was found as a key variable upon phenol photooxidation reaction, with the best optimum performance at low and high wavelengths, and a minimum photodegradation yield at ca. 400 nm for all tested carbon materials. Another parameter strongly influencing the photoactivity of the nanoporous carbons was the surface functionalisation. When sulphur was incorporated to a carbon matrix, the light conversion towards the phenol photooxidation became more efficient and it was dependent on the nature of the S-containing groups. Further on, the analysis of photocurrent transients obtained by irradiating several nanoporous carbon electrodes exhibited different responses, with either anodic or cathodic photocurrent, and transient shapes, thus demonstrating the distinct nature of the catalysed reaction occurring onto electrode/electrolyte interface. The second stage deals with hybrid nanoporous carbon/semiconductor (i.e. WO3) electrodes which allowed to explore the role of nanoporous carbon as additive towards water oxidation reaction. The presence of carbon material had a notable effect on the hybrid electrode performance, in terms of conversion efficiency (IPCE), likely due to the improved collection of the photogenerated electrons by carbon matrix. An optimal amount of carbon additive of ca. 20 wt.% was obtained for the best performing hybrid electrode, with a twofold IPCE compared to that obtained for bare WO3 electrode. The effect of carbon matrix on WO3 performance was found dependent on semiconductor crystalline structure.
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Brach, Stella. "Strength properties of nanoporous materials : theoretical analyses and molecular dynamics computations." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066618.
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L’objectif principal de la thèse a été d’étudier les propriétés de résistance des matériaux nanoporeux par des approches théoriques et numériques. Dans le contexte des méthodes d’homogénéisation, des critères de résistance macroscopiques ont été établis par des approches analytiques à l’homogénéisation non-linéaire et à l’analyse limite. Les critères de résistance ainsi obtenus permettent de tenir en compte les effets de taille, tout en améliorant les formulations déjà existantes. En outre, dans le but de servir de référence pour la calibration et/ou la validation des modèles analytiques, des simulations numériques basées sur la dynamique moléculaire ont été conduites, en se référant à des monocristaux d’aluminium contenant des nanopores sphériques, sous des conditions multiaxiales de vitesse de déformation. Par rapport aux simulations actuellement disponibles dans la littérature, les résultats obtenus ont clairement établi que les surfaces de résistance sont significativement influencées par les trois invariants isotropes de contrainte. Finalement, dans le but de mettre à profit les indications fournies par les simulations numériques, le cas d’un matériau nanoporeux constitué d’une matrice ductile sensible aux trois invariants isotropes a été étudié par une approche par l’analyse limite, en prenant en compte une formulation modifiée du critère de résistance de bigoni. La solution exacte du problème a été établie dans le cas d’un chargement isotrope. A partir des résultats ainsi obtenus, une approche d’analyse limite cinématique a été mise en place, et permet de fournir des estimations des propriétés de résistance macroscopiques sous chargements axisymétriquesThe main objectif of the thesis consisted in investigating strength properties of nanoporous materials by means of theoretical and numerical approaches. In the framework of homogenization methods, novel macroscopic strength criteria have been established via a non-linear homogenization procedure and a kinematic limit-analysis approach. Resulting yield functions allowed to take into account void-size effects on nanoporous materials strength properties, thereby resulting in a strong enhancement of available estimates. Furthermore, aiming to funish effective benchmarking evidence for the calibration and/or the assessment of theoretical models, molecular-dynamics based computations have been carried out on in-silico single crystals embedding spherical nanovoids, simulation domains undergoing multiaxial strain-rate boundary conditions. With respect to available numerical studies, proposed results clearly showed the influence of all the three isotropic stress invariants on computed material strength surfaces. Finally, with the aim to account for physical indications coming from numerical simulations, a ductile nanoporous material with a general isotropic plastic matrix has been investigated via a limit analysis approach, by referring to a modified version of the bigoni strength criterion. The limit state of a hollow-sphere model undergoing isotropic loadings has been exactly determined. Correspondigly, a novel strength criterion has been analytically established in the case of axysimmetric boundary conditions
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O'Brien, Matthew Graham. "Investigations into the formation of nanoporous materials." Thesis, University College London (University of London), 2007. http://discovery.ucl.ac.uk/1445764/.
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The formation processes of a number of microporous materials have been investigated using a powerful combination of ex situ and in situ experimental techniques together with computational modelling. The materials investigated include both zeolites and their aluminophosphate counterparts, which have been previously synthesised and have shown some potential as industrial catalysts. Using an array of techniques has allowed different stages (such as nucleation or crystal growth) to be monitored as well as different aspects of the gel chemistry, such as the geometry of substituted metal ions and the location and conformation of organics within the framework. For MeAPO-34 and A1PO-5, quantum mechanical calculations have examined the early stages of A1PO formation and shown that, unlike silicates, chain growth seems to be preferred. Raman techniques have then identified metal-organic interactions and changes in organic conformation, key to the formation of a particular A1PO over another. For CoAPO-36, energy dispersive X-ray diffraction has been used to monitor crystal growth using three different organic species, and significant differences in the rate of formation have been identified. By combining these observations with crystallographic measurements and molecular mechanical modelling, it has shown that the rate of formation can be affected by both the size and shape of the organic used to form the crystal structure. Combined small angle/wide angle X-ray diffraction has also been used to follow the formation of zeolite-A throughout the nucleation and growth process and, it has been shown, that the insertion of the substituted metal germanium can alter the precise nature of the aggregation and dissolution processes occurring within this system. Finally, a synthesis project has been initiated to attempt to introduce mesopores into microporous A1PO materials. The synthesis of hierarchical microporous-mesoporous materials is of great interest as they offer advantages over both microporous and mesoporous materials for use in catalytic and other applications. The results from this work are very promising, and both A1PO-5 and MeAlPO-34 have been synthesised with some apparent mesoporosity, using non-ionic surfactants. A mechanistic process for the formation of these materials based on micelle and mesophase formation has also been proposed.
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David, Allan E. "Immobilization of enzymes on nanoporous, silica composites." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/2055.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2004.Thesis research directed by: Chemical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Lee, Kah Peng. "Fabrication and applications of nanoporous alumina membranes." Thesis, University of Bath, 2013. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.589649.
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The performance of membranes in various processes is largely dependent on their morphological properties. Thus, membrane structure has been continuously optimised for different applications. Anodic alumina membranes (AAMs) exhibit self-ordered pore structure and the pore size can be tuned in the sub-micrometre range. The aim of this PhD project is to propose and develop AAMs for the applications of membrane filtration and emulsification with potential for scale-up. In the project, the AAMs were initially fabricated in flat sheet form to optimise the process parameters to obtain membranes with a high quality of pore structure. The membrane pore diameter can be readily controlled by the anodization voltage. While AAMs are normally symmetric, by manipulating the anodization voltage, asymmetric AAMs consists of stem pores and active pores have been successfully made. After that, the flat AAMs with symmetric and homogeneous structure were used as a platform to study for surface modification and fluid transport in nano-channels. The surface chemistry and wettability of the membranes has been altered by grafting of silane molecules and carbon coating by chemical vapour deposition. Fluid flow measurement through pristine AAMs with pore diameter in the 20 nm to 100 nm range shows flow enhancement effect, experimentally for the first time, can occur in hydrophilic materials. Subsequently, tubular AAMs were fabricated using aluminium alloy tubes, to be assessed for ultrafiltration and membrane emulsification processes. The pore structure of the tubular AAMs was analogous to flat membranes. Despite the reduced pore circularity and hexagonal arrangement originated from the presence of impurities in the starting materials, the narrow pore size distribution was not compromised. In a selectivity-permeability analysis, the asymmetric tubular AAMs outperformed most of the commercial ceramic membranes but their flux was very low when compared to polymeric membranes. A bovine serum albumin filtration test showed that complete pore blocking-cake filtration model can be used to describe the fouling behaviour. Finally, symmetric tubular membranes were used to study dead-end and cross-flow emulsification processes. The resulting emulsions show low polydispersity. Using a membrane with 25 nm average pore diameter, the obtained average droplet size was as low as 120 nm during a cross-flow emulsification. This is by far the smallest achieved average droplet size by cross-flow membrane emulsification.
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Cohen-Tanugi, David. "Nanoporous graphene as a water desalination membrane." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98743.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 147-162).
Desalination is one of the most promising approaches to supply new fresh water in the face of growing water issues. However, commercial reverse osmosis (RO) techniques still suffer from important drawbacks. In order for desalination to live up to the water challenges of this century, a step-change is needed in RO membrane technology. Thanks to significant advances in the field of computational materials science in the past decade, it is becoming possible to develop a new generation of RO membranes. In this thesis, we explore how computational approaches can be employed to understand, predict and ultimately design a future generation of RO membranes based on graphene. We show that graphene, an atom-thick layer of carbon with exceptional physical and mechanical properties, could allow for water passage while rejecting salt ions if it possessed nanometer-sized pores. Using computer simulations from the atomic scale to the engineering scale, we begin by investigating the relationship between the atomic structure of nanoporous graphene and its membrane properties in RO applications. We then investigate the thermodynamics, chemistry and mechanics of graphene and the water and salt surrounding it. Finally, we establish the system-level implications of graphene's promising membrane properties for desalination plants. Overall, this thesis reveals that graphene can act as an RO membrane with two orders of magnitude higher water permeability than commercial polymer membranes as long as the nanopores have diameters around 0.6nm, that graphene is strong enough to withstand RO pressures as long as it is supported by a substrate material with adequate porosity, and that a nanoporous graphene membrane could ultimately reduce either the energy footprint or the capital requirements of RO desalination. Ultimately, this thesis highlights a path for the development of next-generation membranes for clean water production in the 21st century.
by David Cohen-Tanugi.
Ph. D.
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Rosario, Ryan (Ryan A. ). "Topological characterization of nanoporous gold during coarsening." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/76173.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 34-35).
Previous studies of nanoporous gold have found that, during the coarsening process, the genus per characteristic volume of nanoporous gold has remained constant. Using a rolling-ball type algorithm, in which a test probe rolls over the surface to identify atoms, several test structures and a small-scale nanoporous structure were meshed. The genus was then calculated for each of these meshed structures. It was found that an algorithm that accounts for periodic boundary conditions is required for an accurate genus calculation.
by Ryan Rosario.
S.B.
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Kadhim, Mohammed Salman. "Characterisation of nanoporous polymers for water treatment." Thesis, University of Newcastle upon Tyne, 2017. http://hdl.handle.net/10443/4011.
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Materials which have structural dimensions between 1 nm and 100 nm are called nanomaterials. These materials have unique geometric, physicochemical and mechanical properties. As a result of their properties, nanomaterials can be tailored for specific applications. Polymers Synthesized from High Internal Phase Emulsions (PolyHIPEs) are a type of porous material with high specific surface area due to their nanoscale structure which have the ability to function as ion exchange media that can remove contaminants from water. PolyHIPEs can therefore be used in ion exchange modules to remove metals from wastewater. The advantage of using PolyHIPEs is that fewer steps are necessary compared with traditional filtration methods, and they are more economic and more selective than the traditional materials. A high internal-phase emulsion (HIPE) contains both oil and aqueous or dispersed phases. The oil phase has monomers such as styrene, a cross-linker such as Divinylbenzene (DVB), and non-ionic surfactants while the aqueous phase consists of deionized water and polymerisation initiators such as potassium pyrosulphate. The emulsion is subjected to the polymerization process, usually at 60 ̊C and pores are produced within the polymer due to the presence of the aqueous phase. The polyHIPE is then washed with propanol to release the residual surfactant and unreacted monomer. In this work, we used different HIPE mixing times (10, 15, 20, 25, and 30 minutes, respectively) in order to change the pore size distribution. After synthesis the PolyHIPEs are subjected to a sulphonation process which changes the PolyHIPE character from hydrophobic to hydrophilic. Finally, ion exchange experiments have been conducted by using sulphonated PolyHIPE beads as is and coated with iron oxide. As simulated contaminated water nickel and copper solutions were used during this process. The results show the removal efficiency of the metal ion from solution was much higher with sulphonated beads at range of pH (6, 7, 8 and 9). Changing the pH allowed the metals to be removed from the PolyHIPE for recovery and filter regeneration but the amount of metals after the regeneration process is low compared with initial concentration.
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Sneddon, Gregor. "Nanoporous carbon capture materials from sustainable sources." Thesis, Heriot-Watt University, 2017. http://hdl.handle.net/10399/3364.
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Rising CO2 levels in the atmosphere from anthropogenic sources can be seen as one of the greatest problems faced by mankind in modern history. CO2 capture and subsequent storage or utilisation is one possible solution to increasing CO2 levels in the short-term, until humanity is less reliant on fossil fuels. This thesis will investigate currently available state of the art CO2 capture technologies and provide a critical evaluation on their suitability. Furthermore, current research into the storage and utilisation of captured CO2 will also be studied and the long-term suitability of these approaches to increasing CO2 levels determined. New solid-state CO2 adsorption materials have been developed using waste polymeric materials as the primary agent for selective adsorption of CO2. The approach of using waste materials for CO2 adsorption is advantageous in that the waste material is being used to deal with another waste material, namely CO2. The waste materials utilised in this research were chitosan, a waste material derived from chitin, a large waste from the seafood industry, and polyvinylchloride (PVC), a polymer mainly used in the fabrication of household products. It is demonstrated in this thesis that with minimal modification, these waste materials can be utilised for the capture of CO2 at levels comparable to that of the currently available state-of-the-art materials.
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Chung-Fu, Cheng. "NANOPOROUS MATERIALS FOR ENERGY STORAGE AND ELECTROCATALYSIS." University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron16188502947935.
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Kong, Xinguo. "APPLICATION OF NANOPOROUS MATERIALS IN MECHANICAL SYSTEMS." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1150255954.
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Smith, Ross Andrew. "Biomedical Applications Employing Microfabricated Silicon Nanoporous Membranes." Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1278705155.
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Uppalapati, Badharinadh. "Fabrication of Nanoporous Gold and Biological Applications." VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3552.
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FABRICATION OF NANOPOROUS GOLD AND BIOLOGICAL APPLICATIONS By Badharinadh Uppalapati A Dissertation submitted in partial fulfillment of the requirements for the degree of Master of Science at Virginia Commonwealth University. Virginia Commonwealth University, 2014 Major Director: Maryanne M. Collinson, Professor, Department of Chemistry Fabrication of nanoporous gold electrodes by dealloying Au:Ag alloys has attracted much attention in sensing applications. In the first part of this work, the electrochemical response of the redox active molecule, potassium ferricyanide, in a solution of bovine serum albumin in buffer, serum or blood was studied using nanoporous gold and comparisons made to planar gold. Nanoporous gold electrodes with different surface areas and porosity were prepared by dealloying Au:Ag alloy in nitric acid for different dealloying times, specifically, 7.5, 10, 12.5, 20 minutes. Characterization was done using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), and cyclic voltammetry (CV). Using cyclic voltammetry, planar gold electrodes exposed to bovine serum albumin in buffer showed a decrease in Faradaic peak current and an increase in peak splitting for potassium ferricyanide. The time required for the peak Faradaic current to drop to one-half of its original value was 3 minutes. At nanoporous gold electrodes, however, no significant reduction in Faradaic peak current or increase in peak splitting was observed. Nanoporous gold electrodes having the smallest pore size and largest surface area showed ideal results to biofouling. These electrodes are believed to impede the mass transport of large biomolecules while allowing small redox molecules to exchange electrons effectively with the electrode. In the second part of this work, the open circuit potential (OCP) of biologic solutions (e.g., blood) was measured using nanoporous gold electrodes. Historically, the measurement of blood redox potential has been hindered due to significant fouling and surface passivation of the metal electrodes. As nanoporous gold electrodes retained electrochemical activity of redox probes like potassium ferricyanide in human serum and rabbit blood, they were used to measure the OCP of blood and plasma from various animals like pig, rabbit, rat, monkey and humans. Comparisons were made to planar gold electrodes. The OCP values at both the planar gold and nanoporous gold electrodes were different from each other and there was variability due to different constituents present in blood and plasma. The OCP of rabbit blood and crashed rabbit blood was measured and the values were found to be different from each other indicating that ORP helps in measuring the animal condition. Ascorbic acid was added to rabbit and sheep blood and OCP measured at the nanoporous electrodes. Addition of reducing agent to blood at different intervals and different concentrations showed a change in potential with concentration.
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Kim, Seongjun [Verfasser]. "Nanoporous materials for optical applications / Seongjun Kim." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2020. http://d-nb.info/1224883616/34.
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Vanella, Andrea. "Nanoparticle formation in nanoporous structures and applications." Doctoral thesis, Università di Siena, 2022. http://hdl.handle.net/11365/1210313.
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In the recent years the scientific community demonstrates an increasing interest in the study of nanoparticles and their properties, such as interaction with a surface and the adsorption/desorption characteristic. The latte properties, as well the formation and growth of nanoparticles, can be controlled by a proper light source. On the other hand having a much larger specific surface to increase the adsorbed amount of atoms, is a desirable characteristic of the system. That is on of the reason of the large exploitation of nanoporous material in many different research fields. Porous glass presents a wide variety of benefits: thermal and chemical stability, low production cost, easiness of handling and large value of specific surface area, which can be of the order tens square meters per grams.
This thesis work falls into the context described above, in particular it aims to investigate the adsorption/desorption process of alkali atoms onto different randomly oriented pores structures, as well the formation of aggregates in the pores of the adsorbed atoms by using different external light sources. The control of the desorption process as well as the formation and the desorption of nanoparticles make use of two light induced process: Light Induced Atomic Desorption or LIAD and the Surface Plasmon Induced Desorption. The main difference between these two effects, beside the physics behind the two effects is intrinsically different, is that for the latter is required a resonant light source resonant with the plasmonic oscillation while for the LIAD it is not needed any resonant wavelength.
The main and newer part of the work is done in a chamber were is present an Ultra High Vacuum regime. Most of the studies on this topic were performed in vapor filled cells. The use of an Ultra High Vacuum regime for this work is done to overcome some drawback of the vapor cells, such as the impossibility to change atomic species once that a cell is built or the difficult controlling of the atomic density. Indeed in this apparatus the loading process is done with an externally removable dispenser controlled by a current flowing into it. Hence the loading process is no more continuous an can be switched off by switching off the flowing current. Once the UHV regime is reached, the first step is the loading of the porous sample. Then the adsorption properties at different wavelengths are studied as well as that eventual desorption of the atomic specimen. The formation of nanoparticles in the porous structures are induced by an external light source under different condition of intensity and illumination time. Similar studies are also performed in alkali vapor filled cells, in order to compare the results.
There were performed simultaneously measurements by on the optical signal and electric signal by means of a channeltron.
The measurements performed in this work showed that by using porous glass, with different average pores size and under an appropriate illumination, it is possible to exploit the LIAD effect to enhance the aggregation of Rb nanoparticles in UHV regime. The most satisfying sample revealed to be a film of nanoporous alumina of 300 nm thickness.
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PINNA, ANDREA. "Nanoporous Metals: Fabrication and Structure-Properties Relationship." Doctoral thesis, Università degli Studi di Cagliari, 2022. http://hdl.handle.net/11584/332684.
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Nanoporous metals represent a unique class of materials with promising properties for a wide set of applications in advanced technology. Their combined self-supported monolithic form, high surface area, and high electrical conductivity are only the most obvious peculiarities of this kind of material. Since the beginning of an intensive work in 2001, nanoporous metals have shown high potential and tunable properties. However, the effective use in real applications is hampered by some challenging issues, such as the difficult fabrication of low-cost metals in a nanoporous form, the mechanical fragility and the low stability in certain working environments, i.e. electrolytes or high temperatures, and by the lack of a full understanding of the origin of some peculiar properties. The work presented in this thesis has been done with the purpose to address these issues. The fabrication of nanoporous metals and related composites has been studied to enlarge the possible properties of the common nanoporous gold and copper, and at the same time to find new strategies for the fabrication of nanoporous aluminum, a promising material for its low-cost, low-density, high electrical conductivity and corrosion resistance. Moreover, nanoporous gold thermal stability and behavior toward the degradation of organic dyes were further explored.
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Ceratti, Davide Raffaele. "Viability of nanoporous films for nanofluidic applications." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066482/document.
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Ces travaux de thèse ont eu deux objectifs: i) le développent de systèmes nanofluidique en utilisant une méthode non-lithographique, peu chère et facilement transposable à l'échelle industrielle ii) la compréhension des phénomènes nanofluidiques au travers des études expérimentales et de modélisation. Des couches minces mesoporeuses, en particulier des structures planaires avec des nanopiliers, ont été utilisé pour des études sur l'infiltration capillaire des liquides dans espaces confiné au niveau nanométrique. En plus des premiers tests pour des applications plus complexes comme des séparations et réactions nanoconfiné. Des structures mesoporeuses non-organisés ont aussi été étudiées pour déterminer la relation entre la nanostructure et la vitesse de remplissage capillaire. A été aussi démontré que pour des porosités avec des forts rétrécissements le remplissage capillaire se produit par l'intermédiaire d'une phase vapeur. Les échantillons ont été préparés par dip-coating. Une méthode de préparation basé sur une substitution de la plus grande parte de la solution à déposer par un fluide inerte a été développé. La méthode permet de réduire fortement le cout de procédé et, par conséquence, de faire des dépôts sur plus grande surface. Un effort dans la modélisation des phénomènes nanofluidiques a aussi été fait pendant cette thèse. Une méthode de simulation qui permet de décrire adéquatement les interactions hydrodynamiques dans un système nano a été utilisée pour simuler un flux électro-osmotique. La méthode, Stochastic Rotational Dynamics, a été valide par confrontation avec des résultats connus et l'influence des certains paramètres de simulation évaluée dans le détailThis thesis had a dual purpose: i) the development of nanofluidic devices through not lithographic, cheap and scalable bottom-up approach ii) the understanding of nanofluidic phenomena both through experiments and simulations. Mesoporous thin films, in particular Pillared Planar Nanochannels (PPNs), were prepared and utilized to study the capillary infiltration of liquids in nanostructures and have been tested for future nanofluidic applications like separations and nanoconfined reactions. Non organized mesoporous films have also been studied to determine the relationship between nanostructure characteristics and infiltration speed. It has been also demonstrated that in the case of porosities with reduced bottle-necks capillary penetration is performed through a vapor mediated mechanism The samples were prepared by dip-coating. A novel method of preparation based on the substitution of a large part of the deposing solution in dip-coating with an inert fluid has been developed in order to strongly reduce the fabrication costs and allow the preparation of larger samples. Moreover advancement in control of the dip-coating technique in “acceleration-mode” to produce thickness gradients has been developed and some potential application linked to fluidics shown. Finally a part of the effort of this thesis has been placed in the modeling of the electro-osmotic phenomenon in nanostructures through a rather novel simulation method, Stochastic Rotational Dynamics, which takes into account the hydrodynamics and the other interactions inside a nanofluidic system. Validations of the method and further investigations in particular nanofluidic conditions have been performed
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Ceratti, Davide Raffaele. "Viability of nanoporous films for nanofluidic applications." Electronic Thesis or Diss., Paris 6, 2015. http://www.theses.fr/2015PA066482.
Full textAbstract:
Ces travaux de thèse ont eu deux objectifs: i) le développent de systèmes nanofluidique en utilisant une méthode non-lithographique, peu chère et facilement transposable à l'échelle industrielle ii) la compréhension des phénomènes nanofluidiques au travers des études expérimentales et de modélisation. Des couches minces mesoporeuses, en particulier des structures planaires avec des nanopiliers, ont été utilisé pour des études sur l'infiltration capillaire des liquides dans espaces confiné au niveau nanométrique. En plus des premiers tests pour des applications plus complexes comme des séparations et réactions nanoconfiné. Des structures mesoporeuses non-organisés ont aussi été étudiées pour déterminer la relation entre la nanostructure et la vitesse de remplissage capillaire. A été aussi démontré que pour des porosités avec des forts rétrécissements le remplissage capillaire se produit par l'intermédiaire d'une phase vapeur. Les échantillons ont été préparés par dip-coating. Une méthode de préparation basé sur une substitution de la plus grande parte de la solution à déposer par un fluide inerte a été développé. La méthode permet de réduire fortement le cout de procédé et, par conséquence, de faire des dépôts sur plus grande surface. Un effort dans la modélisation des phénomènes nanofluidiques a aussi été fait pendant cette thèse. Une méthode de simulation qui permet de décrire adéquatement les interactions hydrodynamiques dans un système nano a été utilisée pour simuler un flux électro-osmotique. La méthode, Stochastic Rotational Dynamics, a été valide par confrontation avec des résultats connus et l'influence des certains paramètres de simulation évaluée dans le détailThis thesis had a dual purpose: i) the development of nanofluidic devices through not lithographic, cheap and scalable bottom-up approach ii) the understanding of nanofluidic phenomena both through experiments and simulations. Mesoporous thin films, in particular Pillared Planar Nanochannels (PPNs), were prepared and utilized to study the capillary infiltration of liquids in nanostructures and have been tested for future nanofluidic applications like separations and nanoconfined reactions. Non organized mesoporous films have also been studied to determine the relationship between nanostructure characteristics and infiltration speed. It has been also demonstrated that in the case of porosities with reduced bottle-necks capillary penetration is performed through a vapor mediated mechanism The samples were prepared by dip-coating. A novel method of preparation based on the substitution of a large part of the deposing solution in dip-coating with an inert fluid has been developed in order to strongly reduce the fabrication costs and allow the preparation of larger samples. Moreover advancement in control of the dip-coating technique in “acceleration-mode” to produce thickness gradients has been developed and some potential application linked to fluidics shown. Finally a part of the effort of this thesis has been placed in the modeling of the electro-osmotic phenomenon in nanostructures through a rather novel simulation method, Stochastic Rotational Dynamics, which takes into account the hydrodynamics and the other interactions inside a nanofluidic system. Validations of the method and further investigations in particular nanofluidic conditions have been performed
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Porta, Batalla Maria. "Development of Nanoporous Anodic Alumina Technologies for Drug Delivery." Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/460761.
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L'alliberament de fàrmacs és un procediment en què un compost o un dispositiu allibera una molècula de manera controlada. D’aquesta manera, el medicament podrà ser sotmès a absorció, distribució, metabolisme i excreció. Els semiconductors nanoporosos com l'alúmina o el silici s'utilitzen per a la fabricació de vehicles de fàrmacs a causa de les seves característiques distintives, com ara: fabricació de baix cost, estructura de porus/ mida controlable dels nanotubs, química superficial adaptable, gran àrea superficial, capacitat d'alta càrrega, resistivitat química i rigidesa mecànica. Aquesta materials poden tenir un paper especial en la tecnologia d’alliberament de fàrmacs. Tot i que s'ha estudiat l'alliberament de medicaments a partir de materials nanoporosos i mesoporosos, hi ha una manca de comprensió de les cinètiques d'alliberament d'aquestes plataformes i la dinàmica que les regula. Per aquest motiu, el nostre objectiu és explicar la cinètica d'alliberament des de les superfícies nanoporoses i mesoporoses i modelar-les. Aquest model serà dilucidat mitjançant un estudi sistemàtic dels perfils d'alliberament. En conjunt, la tecnologia, la caracterització i les aplicacions presentades en aquesta tesi són força alentadores i proporcionen un punt de partida per desenvolupar estructures intel·ligents innovadores que trobaran aplicacions en sistemes de lliurament de medicaments.La liberación de fármaco es un procedimiento en el que un compuesto o un dispositivo libera una molécula de una manera controlada. Posteriormente, este fármaco podrà someterse a absorción, distribución, metabolismo y excreción. Se utilizan semiconductores nanoporosos como la alúmina o el silicio para fabricar vehículos de fármacos debido a sus características distintivas tales como: fabricación de bajo costo, estructura de poros/tamaño controlable de los nanotubos, química de superficie adaptable, área superficial grande, alta capacidad de carga, resistividad química y rigidez mecánica. Estos materiales pueden tener papel especial en la tecnología de liberación controlada de fármacos. Aunque se ha estudiado la liberación de fármacos a partir de materiales nanoporosos y mesoporosos, existe una falta de comprensión de la cinética de liberación de estas plataformas y de la dinámica que las gobierna. En este sentido, nuestro objetivo es explicar la cinética de liberación de superficies nanoporosas y mesoporosas y modelarlas. Este modelo será elucidado mediante un estudio sistemático de los perfiles de liberación. En conjunto, la tecnología, la caracterización y las aplicaciones presentadas en esta tesis son bastante alentadoras y proporcionan un punto de partida para el desarrollo de estructuras inteligentes e innovadoras que encontrarán aplicaciones en los sistemas de administración de fármacos.
Drug release is a procedure in which a composite or a device releases a molecule in a controlled way. Subsequently the drug would be subjected to absorption, distribution, metabolism and excretion. Nanoporous semiconductors like alumina or silicon are used to fabricate carriers because of their distinctive features such as: low-cost fabrication, controllable pore/nanotube structure, tailored surface chemistry, high surface area, high loading capability, chemical resistivity and mechanical rigidity, have affianced a special role in drug delivery technology. Although drug release from nanoporous and mesoporous materials has been studied, there is a lack of understanding of the release kinetics from these platforms and the dynamics governing them. For this reason, our aim is to explain the release kinetics from nanoporous and mesoporous surfaces and model them. This model will be elucidated by means of a systematic study of release profiles. Altogether, technology, characterization and applications presented in this thesis are rather encouraging and are providing a starting point for developing innovative smart structures that will find applications in drug delivery systems.
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Barsuk, Daria. "Conception Métallurgique de Nouvelles Structures Nanoporeuses." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI051/document.
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De nouveaux matériaux métalliques nanoporeux à base d’éléments n’appartenant pas à la famille du Pt ont été synthétisés par le "dealloying" (ou dissolution sélective) d’alliages rapidement solidifiés. L’objectif est d’examiner les propriétés catalytiques en vue d’utilisation dans des piles à combustible alcalines directes ou en tant que substrats actifs pour la spectroscopie SERS. Des surfaces et des matrices nanostructurées de cuivre de morphologie très fines et une forte surface spécifique ont été obtenues respectivement par le dealloying aqueux de rubans CuxCa100-x amorphe (35 New nanoporous metallic materials based on non-Pt group metals have been synthesized via dealloying of rapidly solidified alloys and aimed to demonstrate competitive catalytic performance in the field of direct alkaline fuel cells and SERS-active substrates. Nanostructured copper surface and nanoporous copper matrix with very fine morphology and specific surface area were obtained by chemical dealloying of bulk Cu90(HfZr)10 and melt-spun amorphous CuxCa100-x (x ranging from 35 to 80 at.%) family of alloys accordingly. Nanoporous silver and cobalt substrates were produced by dealloying of M38.75Cu38.75Si22.5 crystalline ribbons (M = Co and Ag) as a result of the removal of Cu and Si-rich phases. In addition to conventional characterization methods, all nanoporous structures have been reconstructed by FIB-nanotomography, clearly exposing the morphological diversity of the three systems with transversal porosity when visualized and color-mapped in 3D by a special numerical tomography tool. It is for the first time that a practical significance of these materials has been explored in the scope of self-supported anodic catalysts, suggested throughout this study as an alternative to the unstable Pt-based carbon-supported commercial composites. Half-cell electrochemical tests demonstrated an excellent catalytic activity towards the oxidation of a borane fuel and superior stability of functioning in the alkaline environment compared to Pt/C catalyst. In similar conditions, nanoporous Co showed higher efficiency but lower stability, attributed to the complex chemical composition of its porous scaffold. Nanoporous Cu has not been exploited for the mentioned applications due to its high brittleness and is suggested to go through improvements on the step of precursor synthesis. Lastly, while exploring the mechanical behavior of the NPMs by instrumented nanoindentation of different nanoporous Ag substrates, a load-displacement dependence phenomenological model has been suggested for this class of metallic materials
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Wang, Jian. "The nanoporous morphology of photopolymerized crosslinked polyacrylamide hydrogels." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2687.
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Chennapragada, Pavani. "Fabrication of palladium nanoparticles and nanoporous alumina templates." [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001027.
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Santos, Alejandro Abel. "Structural engineering of nanoporous anodic alumina and applications." Doctoral thesis, Universitat Rovira i Virgili, 2010. http://hdl.handle.net/10803/8480.
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En esta tesis doctoral se utilizan diversas estrategias de ingeniería estructural para desarrollar nuevas nanoestructuras basadas en alúmina nanoporosa. Dichas nanoestructuras o moldes son posteriormente utilizados para desarrollar otras nanoestructuras innovadoras basadas en ciertos materiales tales como polímeros, metales magnéticos y semiconductores, interesantes desde el punto de vista de futuras aplicaciones. Las nanoestructuras replicadas a partir de los moldes de alúmina porosa pueden ser integradas en varios tipos de nanodispositivos (nanoelectrodos para deposición directa de nanopartículas desde una corriente de gas, precipitadores electrostáticos, células solares con heterouniones volumétricas, dispositivos ópticos unidimensionales, nanofiltros, etc.).En primer lugar, se fabrican cuatro tipos tradicionales de alúmina porosa autoordenada utilizando la anodización blanda en dos pasos. Los ácidos utilizados para fabricar dichos tipos de alúmina porosa son sulfúrico, oxálico y fosfórico. Los voltajes de anodización aplicados son 20, 40 y 160-195 V, respectivamente. El diámetro del poro varia entre 20 y 250 nm, siendo la distancia entre poros 55, 100 y 400-500 nm, respectivamente. Posteriormente, se fabrica alúmina porosa autoordenada utilizando la anodización dura en un paso utilizando ácido oxálico. También se emplea la anodización dura en dos pasos para fabricar moldes de alúmina porosa ordenada sin capa protectiva, la cuál es característica de un proceso de anodización dura en un paso.
Además, siguiendo una técnica de re-anodización, se elimina la capa barrera de óxido de la parte posterior de los moldes de alúmina sin eliminar el sustrato de aluminio ni desprender el molde de alúmina del sustrato. Después, por medio de un proceso de anodización asimétrico en el cuál se modifican las condiciones de anodización (voltaje de anodinado, tipo y concentración de ácido), se fabrican moldes de alúmina jerarquizados con múltiples configuraciones. También se producen moldes de alúmina porosa bicapa combinando anodizado duro y blando. Posteriormente, se emplea un molde de nitruro de silicio para fabricar moldes de alúmina porosa perfectamente ordenados mediante la técnica de nanoimpresión. Además, utilizando esta misma técnica y seleccionando las condiciones de anodización adecuadas, es posible fabricar moldes de alúmina porosa perfectamente ordenados con un ordenamiento de poros extraordinario. Finalmente, se fabrican nanoembudos basados en alúmina porosa intercalando consecutivamente pasos de anodizado y ampliación de diámetro de poro. Dichas nanoestructuras son diseñadas con un alto grado de precisión mediante dos procesos de calibración sistemáticos. Además, se desarrolla un modelo teórico que predice el crecimiento del poro durante el proceso de anodización. Este modelo es experimentalmente validado.
A partir de dichas nanoestructuras basadas en moldes de alúmina porosa se estudian varias aplicaciones. En primer lugar, se sinterizan nanopilares magnéticos ordenados sobre sustratos de aluminio mediante deposición electroquímica. Estos se caracterizan por varias técnicas (ESEM, EDXS y XRD). Por sus propiedades magnéticas, dichos nanopilares podrían ser empleados como nanoelectrodos para deposición directa de nanopartículas desde una corriente de gas o como precipitadores electrostáticos. En segundo lugar, se fabrican estructuras poliméricas compuestas de nanopilares sobre un sustrato nanoestructurado basado en el mismo polímero. Para ello, se emplean moldes de alúmina porosa jerarquizados. Además, nanopilares del mismo polímero son transferidos sobre sustratos de ITO/vidrio. La nanoestructura resultante es caracterizada por ESEM, TEM, XRD, CS-AFM y se demuestra que ésta puede ser óptima para integrarse en celdas solares orgánicas con heterouniones volumétricas de alto rendimiento. En tercer lugar, se presenta la primera etapa en la fabricación de mosaicos de nanohilos y nanotubos de níquel. Además, dichas nanoestructuras se utilizan para llevar a cabo un estudio sistemático sobre cómo la re-organización de los poros durante el cambio de régimen de anodización de blando a duro en moldes de alúmina porosa bicapa. Estos mosaicos de nanoestructuras magnéticas podrían ser empleados para desarrollar nuevas plataformas de almacenamiento de datos. Finalmente, se fabrican cadenas de nanoesferas de silicio por infiltración bajo vacío a través de nanoembudos basados en alúmina porosa. Dichas nanoestructuras podrían ser integradas en dispositivos ópticos de tamaño nanométrico.
In this PhD thesis, several structural engineering strategies are applied to develop innovative templates based on nanoporous anodic alumina. These templates are subsequently used to develop other nanostructures based on certain materials with multiple applications such as polymers, magnetic metals and semiconductors. These replicated nanostructures could be integrated in various types of nanodevices (e.g. nanoelectrodes for direct deposition of nanoparticles from a gas draught, bulk-heterojunction solar cells, one-dimensional optoelectronic devices, nanofilters and so on). It is expected that the results presented will become a starting point to develop new nanodevices and applications in a wide range of research fields.
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Kirstein, Johanna. "Diffusion of single molecules in nanoporous mesostructured materials." Diss., lmu, 2007. http://nbn-resolving.de/urn:nbn:de:bvb:19-79478.
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Woodford, Julia Jane. "Hierarchical nanoporous solid base catalysts for biodiesel synthesis." Thesis, Cardiff University, 2013. http://orca.cf.ac.uk/51927/.
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The discovery of alternative solid base catalysts to replace homogeneous catalysts currently used in the industrial synthesis of biodiesel could remove the need for atom and energy inefficient routes to the desired biofuel product, and allow for the possibility of a continuous production process. Hydrotalcites have shown promise as catalysts in the transesterification of triglycerides with methanol to form biodiesel; however their activity is hampered by slow diffusion of the bulky triglycerides through the microporous hydrotalcite structure and poor accessibility of the active sites. This thesis has examined the synthesis of hydrotalcites via novel routes in an attempt to improve base site accessibility to triglycerides feedstocks in order to enhance catalytic performance. Macropore introduction into MgAl hydrotalcites helps to overcome mass transport limitations and increase their activity 10-fold for the transesterification of olive oil. Hydrotalcites prepared on an alumina support through a novel grafting and hydrothermal protocol form well-ordered crystallites on the high surface area oxide support. The resulting hydrotalcite-coated aluminas exhibit activities comparable to macroporous hydrotalcites of similar Mg:Al stoichiometries. Hydrotalcites prepared on alumina-grafted SBA-15 and macroporous-mesoporous SBA-15 employing the same grafting and hydrothermal synthesis are also extremely active in triglyceride transesterification, with the hierarchical macroporous-mesoporous outperforming the purely mesoporous SBA-15 support. Comparative studies on non-porous solid bases derived from nanocrystalline MgO reveal that Cs doping via co-precipitation confers superior activity for tributyrin transesterification. X-ray absorption spectroscopy has been applied to probe the local chemical environment of Cs atoms within such Cs-doped MgO, and the catalytically active phase identified as Cs2Mg(CO3)2(H2O)4. Cs-MgO is an order of magnitude more active for the transesterification of bulky triglycerides and olive oil than the undoped, parent MgO nanocrystals.
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Nguyen, Khanh Dieu Hong. "Framework redox sites in nanoporous molecular sieve catalyst." Thesis, University College London (University of London), 2008. http://discovery.ucl.ac.uk/17226/.
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The work described in this thesis is concerned with the characterisation of metal ions substituted nanoporous materials. The first chapter deals with the introduction to nanoporous materials, with historical background, structural chemistry, synthetic methods and catalytic applications. The second chapter describe the experimental techniques used in this work. Chapter 3 deals with the study of cobalt ions substituted nanoporous aluminophosphate material. Here the main aim is to understand the effect of synthesis condition used in preparing CoA1PO-34, CoSAPO-34 materials on the particle size, micro-structure stability and more importantly the oxidation-reduction chemistry of cobalt ions. It was found using microscopy and in situ XRD/EXAFS technique, that when CoA1PO-5.PO or CoSAPO-34 materials are prepared around pH 7.5, the system has small particles, with good structural stability and complete redox chemistry of cobalt ions. Chapter 4 describes the results obtained from the in situ studies of iron substituted A1PO-5. Here the aim to investigate the influence of structure directing organic template on the state of iron in the as-synthesised and calcined form. It was found that, depending on the nature of template, the coordination of Fe(III) ions change from octahedral to tetrahedral at different temperature. In situ studies of reactivity of Ti(IV) species in titanosilicate TS-1 material was studied using X-ray absorption near edge structure and they are described in chapter 5. A comparison between amorphous titanosilicate and crystalline TS-1 was made and it was found that titanium ions in amorphous material reacts much more readily with water molecules compared to crystalline counter part and this correlates with the hydrophobic character of crystalline TS-1 material. In the final chapter, 6, a brief summary and conclusions obtained from the work described in the results chapter are given.
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Schmidt, Iver. "Design of nanoporous materials for light alkane transformation." Thesis, University of Liverpool, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369114.
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Borchardt, Lars, Claudia Hoffmann, Martin Oschatz, Lars Mammitzsch, Uwe Petasch, Mathias Herrmann, and Stefan Kaskel. "Preparation and application of cellular and nanoporous carbides." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-138910.
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A tutorial review on cellular as well as nanoporous carbides covering their structure, synthesis and potential applications. Especially new carbide materials with a hierarchical pore structure are in focus. As a central theme silicon carbide based materials are picked out, but also titanium, tungsten and boron carbides, as well as carbide-derived carbons, are part of this reviewDieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
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Kulkarni, Ambarish R. "Multiscale modeling of nanoporous materials for adsorptive separations." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53053.
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The detrimental effects of rising CO₂ levels on the global climate have made carbon abatement technologies one of the most widely researched areas of recent times. In this thesis, we first present a techno-economic analysis of a novel approach to directly capture CO₂ from air (Air Capture) using highly selective adsorbents. Our process modeling calculations suggest that the monetary cost of Air Capture can be reduced significantly by identifying adsorbents that have high capacities and optimum heats of adsorption. The search for the best performing material is not limited to Air Capture, but is generally applicable for any adsorption-based separation. Recently, a new class of nanoporous materials, Metal-Organic Frameworks (MOFs), have been widely studied using both experimental and computational techniques. In this thesis, we use a combined quantum chemistry and classical simulations approach to predict macroscopic properties of MOFs. Specifically, we describe a systematic procedure for developing classical force fields that accurately represent hydrocarbon interactions with the MIL-series of MOFs using Density Functional Theory (DFT) calculations. We show that this force field development technique is easily extended for screening a large number of complex open metal site MOFs for various olefin/paraffin separations. Finally, we demonstrate the capability of DFT for predicting MOF topologies by studying the effect of ligand functionalization during CuBTC synthesis. This thesis highlights the versatility and opportunities of using multiscale modeling approach that combines process modeling, classical simulations and quantum chemistry calculations to study nanoporous materials for adsorptive separations.
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Markham, Matthew L. "An investigation into the properties of nanoporous semiconductors." Thesis, University of Southampton, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432628.
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Fung, Alex Weng Pui. "Localization transport in granular and nanoporous carbon systems." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/34088.
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Nazarudin, N. "Catalytic cracking of plastic waste using nanoporous materials." Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1380400/.
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The catalytic cracking of linear low density polyethylene (lldPE), polypropylene (PP) and plastic waste were investigated using commercial zeolites (ZSM-5, zeolite β, Mordenite, and USY), USY modified by ion-exchange, mixed catalyst (ZSM-5/ zeolite β, ZSM-5/USY), and nanocrystaline-ZSM-5. USY was modified by ion-exchange with ammonium salt at two different temperatures (298K and 353K) and for various reaction times. The cracking of PP and lldPE was performed using mixed catalysts and in addition a detailed study was carried out employing statistical design of response surface methodology to obtain the optimum reaction condition to produce maximum products. Nano crystalline ZSM-5 catalysts were prepared with/without the presence of alcohol (ethanol and isopropanol) and sodium and statistical analysis of completely random design was used to determine the effect of these constituents in the reaction mixture on the characteristics of ZSM-5 material and on their catalytic performance. The catalytic studies using commercial zeolites revealed that the zeolite β and mordenite produced higher liquid yield from lldPE and plastic waste, respectively. However, by using a modified USY, by ion-exchange at temperature 298K for 48hours, a further improvement to the liquid yield was achieved. Using a mixer of ZSM-5/ zeolite β it was possible to achieve very good conversions for both lldPE and PP with least amount of coke formation. Further studies on catalytic cracking of lldPE using nanocrystalline ZSM-5 indicate that the highest liquid yield that could be achieved was by using the material synthesised in the presence of alcohol and sodium in the starting solution. The effect of constituents in the starting gel mixture for ZSM-5 synthesis appears to influence surface area, acidity and particle size; however it appears that this does not affect the catalytic performance for cracking of lldPE. However the study suggest that control of external surface area and particle size is highly significant.