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Zhang, Jin. "Shakedown of porous materials." Thesis, Lille 1, 2018. http://www.theses.fr/2018LIL1I044/document.
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Cette thèse est consacrée à la détermination des états limites de l'adaptation des matériaux ductiles poreux sur la base du théorème de Melan et en considérant le modèle de la sphère creuse. Dans un premier temps, nous proposons le critère analytique macroscopique d'adaptation avec la matrice de von Mises sous deux charges particuliers, alterné et pulsé. Le critère analytique dépend des première et seconde invariants des contraintes macroscopiques, du signe du troisième et du coefficient de Poisson. Ensuite, ce critère est étendu aux charges cycliques répétées générales par la construction d'un champ de contraintes résiduelles d'essai plus approprié permettant simultanément des calculs analytiques et l'amélioration du modèle précédent. De plus, il est également utilisé pour les matériaux ductiles poreux avec une matrice de Drucker-Prager.L'idée repose d'abord sur la solution exacte pour le charge purement hydrostatique. Il s'avère que la ruine se produit par fatigue. Ensuite, des champs de contrainte d'essai appropriés sont construits avec des termes supplémentaires pour capter les effets de cisaillement. Le domaine de sécurité, défini par l'intersection du domaine d'adaptationet celui d'analyse limite (la ruine survenant brusquement par formation d'un mécanisme au premier cycle), est entièrement comparé avec des simulations élasto-plastique incrémentales et des calculs directs simplifiés.Enfin, nous fournissons une méthode numérique directe pour prédire le domaine de sécurité de l'adaptation des matériaux poreux soumis à des charges variant de manière indépendante en considérant le chemin critique du domaine de chargement au lieu de l'histoire entière. Le problème de l'adaptation est transformé en un problème d'optimisation de grande taille, qui peut être résolu efficacement par l'optimiseur non-linéaire IPOPT pour donner non seulement le facteur de charge limite, mais aussi le champ de contrainte résiduelle correspondant à l'état d'adaptationThis thesis is devoted to the determination of shakedown limit states of porous ductile materials based on Melan's static theorem by considering the hollow sphere model, analytically and numerically. First of all, we determine the analytical macroscopic shakedown criterion of the considered unit cell with von Mises matrix under alternating and pulsating special loading cases. The proposed macroscopic analytical criterion depends on the first and second macroscopic stresses invariants, the sign of the third one and Poisson's ratio. Then, the procedure is extended to the general cyclically repeated loads by the construction of a more appropriate trial residual stress field allowing analytical computations and the improvement of the previous model simultaneously. Moreover, this approach is applied to porous materials with dilatant Drucker-Prager matrix.The idea relies firstly on the exact solution for the pure hydrostatic loading condition. It turns out that the collapse occurs by fatigue. Next, suitable trial stress fields are built with additional terms to capture the shear effects. The safety domain, defined by the intersection of the shakedown limit domain and the limit analysis domain corresponding to the sudden collapse by development of a mechanism at the first cycle, is fully compared with step-by-step incremental elastic-plastic simulations and simplified direct computations. At last, we provide a direct numerical method to predict the shakedown safety domain of porous materials subjected to multi-varying independent loadings by considering the critical loading path of the load domain instead of the whole history. The shakedown problem is transformed into a large-size optimization problem, which can be solved efficiently by the non-linear optimizer IPOPT to give out not only the limit load factor, but also the corresponding residual stress field for the shakedown state
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Gong, Xuehui. "POROUS POLYMERIC FUNCTIONAL MATERIALS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1595256175834586.
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NEGRONI, MATTIA. "Dynamics in Porous Materials." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2020. http://hdl.handle.net/10281/263115.
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Il mio lavoro di tesi si è basato sulla caratterizzazione dei materiali porosi rivolgendo particolare attenzione alla ricerca di elementi dinamici all’interno delle strutture e allo studio dei gas adsorbiti. Sono riuscito a rilevare la presenza di rotori parafenilenici ultraveloci sia in cristalli molecolari porosi che in metal-organic framework (MOF). Uno studio più approfondito ha inoltre rivelato come questi moti siano influenzati dal gas adsorbito. Nello specifico l’energia di attivazione della rotazione aumenta in funzione della quantità di gas nei pori. Per meglio capire questa interazione è però fondamentale la conoscenza del comportamento dei gas nei materiali porosi. Ho pertanto rivolto la mia attenzione allo studio del moto di xeno e CO2 in diversi materiali. L’utilizzo combinato di NMR e calcoli ab initio si è rivelato fondamentale per la comprensione di questi fenomeni ed è stato possibile rivelare particolari caratteristiche tanto dei gas quanto dei materiali stessi. La complessità della diffusione all’interno dei canali si è anche presentata in modi insoliti come il moto elicoidale dell’anidride carbonica imposto dal potenziale elettrostatico. Volendo continuare lo studio dei gas nei pori, ho caratterizzato diversi porous aromatic framework (PAF) con la tecnica dello xeno iperpolarizzato. Questo non mi ha consentito solo di misurare con accuratezza le dimensioni dei pori ma anche calcolare l’energia di interazione tra lo xeno e le pareti dei canali. Desiderando espandere le mie conoscenze sull’iperpolarizzazione come tecnica NMR, ho passato sei mesi presso il gruppo del Prof. L. Emsley a Losanna imparando la dynamic nuclear polarization (DNP) nonché la sua applicazione a diversi materiali.My thesis work was based on the characterization of porous materials, paying particular attention to the research of dynamic elements within the structures and to the study of adsorbed gases. I was able to detect the presence of ultrafast paraphenylenic rotors in both porous molecular crystals and metal-organic frameworks (MOFs). A more detailed study has also revealed how these motions are influenced by the adsorbed gas. Specifically, the activation energy of the rotation increases as a function of the quantity of gas in the pores. To better understand this interaction, the knowledge of the behavior of gases in porous materials is fundamental. I turned my attention to the study of xenon and CO2 motion in different materials. The combined use of NMR and ab initio calculations proved to be fundamental for understanding these phenomena and it was possible to reveal particular characteristics both of the gases and of the materials. The complexity of the diffusion within the channels has also been presented in unusual ways as the helicoidal motion of carbon dioxide imposed by the electrostatic potential. To continue the study of pore gases, I characterized several porous aromatic frameworks (PAFs) with the hyperpolarized xenon technique. This not only allowed me to accurately measure the pore size but also to calculate the interaction energy between the xenon and the channel walls. To expand my knowledge on hyperpolarization as an NMR technique, I spent six months at the group of Prof. L. Emsley in Lausanne learning dynamic nuclear polarization (DNP) as well as its application to different materials.
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Jiang, Tong. "Porous tin(IV) sulfide materials." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0007/NQ41557.pdf.
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Tchang, Cervin Nicholas. "Porous Materials from Cellulose Nanofibrils." Doctoral thesis, KTH, Fiberteknologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-155065.
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In the first part of this work a novel type of low-density, sponge-like material for the separation of mixtures of oil and water has been prepared by vapour deposition of hydrophobic tri-chloro-silanes on ultra-porous cellulose nanofibril (CNF) aerogels. To achieve this, a highly porous (>99%) robust CNF aerogel with high structural flexibility is first formed by freeze-drying an aqueous suspension of the CNFs. The density, pore size distribution and wetting properties of the aerogel can be tuned by selecting the concentration of the CNF suspension before freeze-drying. The hydrophobic light-weight aerogels are almost instantly filled with the oil phase when they selectively absorb oil from water, with a capacity to absorb up to 45 times their own weight. The oil can subsequently be drained from the aerogel and the aerogel can then be subjected to a second absorption cycle. The second part is about aerogels with different pore structures and manufactured with freeze-drying and supercritical carbon dioxide for the preparation of super slippery surfaces. Tunable super slippery liquid-infused porous surfaces (SLIPS) were fabricated through fluorination of CNFsand subsequent infusion with perfluorinated liquid lubricants. CNF-based self-standing membranes repelled water and hexadecane with roll-off angles of only a few degrees. The lifetime of the slippery surface was controlled by the rate of evaporation of the lubricant, where the low roll-off angle could be regained with additional infusion. Moreover, adjusting the porosity of the membranes allowed the amount of infused lubricant to be tuned and thereby the lifetime. The CNF-based process permitted the expansion of the concept to coatings on glass, steel, paper and silicon. The lubricant-infused films and coatings are optically transparent and also feature self-cleaning and self-repairing abilities. The third part describes how porous structures from CNFs can be prepared in a new way by using a Pickering foam technique to create CNF-stabilized foams. This technique is promising for up-scaling to enable these porous nanostructured cellulose materials to be produced on a large scale. With this technique, a novel, lightweight and strong porous cellulose material has been prepared by drying aqueous foams stabilized with surface-modified CNFs. Confocal microscopy and high-speed video imaging show that the long-term stability of the wet foams can be attributed to the octylamine-coated, rod-shaped CNF nanoparticles residing at the air-liquid interface which prevent the air bubbles from collapsing or coalescing. Careful removal of the water yields a porous cellulose-based material with a porosity of 98 %, and measurements with an autoporosimeter (APVD) reveal that most pores have a radius in the range of 300 to 500 μm. In the fourth part, the aim was to clarify the mechanisms behind the stabilizing action of CNFs in wet-stable cellulose foams. Factors that have been investigated are the importance of the surface energy of the stabilizing CNF particles, their aspect ratio and charge density, and the concentration of CNF particles at the air-water interface. In order to investigate these parameters, the viscoelastic properties of the interface have been evaluated using the pendant drop method. The properties of the interface have also been compared by foam stability tests to clarify how the interface properties can be related to the foam stability over time. The most important results and conclusions are that CNFs can be used as stabilizing particles for aqueous foams already at a concentration as low as 5 g/L. The reasons for this are the high aspect ratio which is important for gel formation and the viscoelastic modulus of the air-water interface. Foams stabilized with CNFs are therefore much more stable than foams stabilized by cellulose nanocrystals (CNC). The charge density of the CNFs affects the level of liberation of the CNFs within large CNF aggregates and hence the number of contact points at the interface, and also the gel formation and viscoelastic modulus. The charges also lead to a disjoining pressure related to the long-range repulsive electrostatic interaction between the stabilized bubbles, and this contributes to foam stability. In the fifth part, the aim was to develop the drying procedure in order to producea dry porous CNF material using the wet foam as a precursor and to evaluate the dry foam properties. The wet foam was dried in an oven while placed on a liquid-filled porous ceramic frit to preserve and enhance the porous structure in the dried material and prevent the formation of larger cavities and disruptions. The cell structure has been studied by SEM microscopy and APVD (automatic pore volume distribution). The mechanical properties have been studied by a tensile tester (Instron 5566) and the liquid absorption ability with the aid of the APVD-equipment. By changing the charge density of the CNFs it is possible to prepare dry foams with different densities and the lowest density was found to be 6 kg m-3with a porosity of 99.6 %. The Young ́s modulus in compression was 50 MPa and the energy absorption was 2340kJ m-3 for foams with a density of 200 kg m-3. The liquid absorption of the foam with a density of 13 kg m-3 is 34 times its own weight. By chemically cross-linking the foam,it wasalso possible to empty the liquid-filled foams by compression and then to reabsorb the liquid to the same degree with maintained foam integrity. This new processing method also shows great promise for preparing low-density cellulose foams continuously and could be very suitable for industrial up-scaling.QC 20141103
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Chow, Hon-nin. "Computer aided modelling of porous structures." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B39848929.
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Harter, Thomas. "Unconditional and conditional simulation of flow and transport in heterogeneous, variably saturated porous media." Diss., The University of Arizona, 1994. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1994_36_sip1_w.pdf&type=application/pdf.
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Jacobs, Tia. "Self-assembly of new porous materials." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/3970.
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Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2009.ENGLISH ABSTRACT: The primary objective of the work was to prepare and investigate new porous materials using the principles of crystal engineering. Both organic and metal-organic systems were studied and the work can best be divided into two separate sections: 1. The crystal engineering of Dianin’s Compound, a well-known organic host. 2. The design and synthesis of a series of related porous coordination compounds consisting of discrete, dinuclear metallocycles. The first section discusses the synthetic modification of Dianin’s compound in order to engineer a new clathrate host with an altered aperture size. Although this study ultimately failed to isolate the host material in its porous guest-free form, the work led to the discovery of a chiral host framework that aligns guest molecules in a polar fashion, and consequently displays non-linear optical properties. These findings are unprecedented in the long history of crystal engineering of Dianin’s compound and its analogues. This section also describes desorption studies of the new inclusion compound, as well as the known thiol analogue of Dianin’s compound. Systematic characterisation of these desorbed phases has raised interesting fundamental questions about desolvation processes in general. The second section constitutes the major portion of the work. A series of related isostructural coordination metallocycles were synthesised and their structure-property relationships were investigated using a variety of complementary techniques. These metallocyclic compounds all crystallise as solvates in their as-synthesised forms, and different results are obtained upon desolvation of the materials. In each case, desolvation occurs as a single-crystal to single-crystal transformation and three new “seemingly nonporous” porous materials were obtained. A single-crystal diffraction study under various pressures of acetylene and carbon dioxide was conducted for one of the porous metallocycles. This enabled the systematic study of the host deformation with increasing equilibrium pressure (i.e. with increasing guest occupancy). The observed differences in the sorption behaviour for acetylene and carbon dioxide are discussed and rationalised. Gravimetric gas sorption isotherms were also recorded for the three different porous materials and the diffusion of bulkier molecules through the host was also investigated structurally. Finally, a possible gas transport mechanism is postulated for this type of porous material (i.e. seemingly nonporous), and this is supported by thermodynamic and kinetic studies, as well as molecular mechanics and statistical mechanics simulations.
AFRIKAANSE OPSOMMING: Die primêre doel van die werk was om nuwe poreuse materiale te berei en deur die toepassing van beginsels van kristalmanipulasie (E. crystal engineering) te ondersoek. Beide organiese- en metaal-organiese sisteme is bestudeer en die werk kan in twee kategorieë verdeel word: 1. Die kristalmanipulasie van Dianin se verbinding, ’n bekende organiese gasheer. 2. Die ontwerp en sintese van ’n reeks verwante poreuse koördinasieverbindings wat uit diskrete, binukleêre metallosiklieseverbindings bestaan. Die eerste deel handel oor die sintetiese verandering van Dianin se verbinding om ’n nuwe klatraatgasheer met ’n veranderde spleetgrootte te vorm. Alhoewel hierdie studie nie daarin geslaag het om die gasheer in sy poreuse “gas(E. guest)-vrye” vorm te isoleer nie, het die werk ’n nuwe chirale gasheerraamwerk aan die lig gebring. Die chirale gasheerraamwerk rig gas(E. guest)molekules in eendimensionele kolomme op ’n polêre wyse en gevolglik vertoon die materiaal nie-linieêre optiese eienskappe. Hierdie resultaat is ongekend in die lang geskiedenis van kristalmanipulasie van Dianin se verbindings en sy analoë. Hierdie afdeling beskryf ook die desorpsiestudies van die nuwe gasheer, en die tiol-afgeleide van Dianin se verbinding. Die sistematiese karakterisering van hierdie fases na desorpsie het fundamentale vrae na vore gebring oor desorpsieprosesse oor die algmeen. Die tweede afdeling maak die grootste gedeelte van die werk uit. ’n Reeks verwante isostrukturele ringvormige koördinasieverbindings is gesintetiseer en hul struktuureienskap verhoudings is deur ’n verskeidenheid komplementêre tegnieke ondersoek. Hierdie metallosiklieseverbindings kristalliseer almal in gesolveerde toestand vanaf sintese en verskillende resultate word verkry wanneer die verbinding desorpsie ondergaan. In alle gevalle vind gas(E. guest)desorpsie as enkel-kristal na enkel-kristal omsettings plaas en drie nuwe ‘oënskynlik nie-poreuse’ poreuse materiale is bekom. ’n Enkelkristal diffraksiestudie onder verskeie gasdrukke is met asetileen en koolstofdioksied uitgevoer vir een van die poreuse metallosiklieseverbindings. Dit het die geleentheid geskep om die mate waartoe die gasheer as gevolg van verhoogde ewewigsdruk vervorm (en dus toename in gasheerbesetting), sistematies te bestudeer. Die waargenome verskille in sorpsie-optrede vir asetileen en koolstofdioksied word bespreek en verklaar. Gravimetriese gassorpsie isoterme is ook vir die drie poreuse materiale verkry en die diffusie van groter molekules deur die gasheer is struktureel ondersoek. Laastens word ’n moontlike gasoordragmeganisme vir hierdie tipe poreuse (i.e. oënskynlik nie-poreuse) materiale gepostuleer. Hierdie bespreking word deur termodinamiese en kinetiese studies aangevul, sowel as molekulêre-meganika en statisties-meganiese studies.
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Alsayednoor, Jafar. "Modelling and characterisation of porous materials." Thesis, University of Glasgow, 2013. http://theses.gla.ac.uk/4808/.
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Porous materials possessing random microstructures exist in both organic (e.g. polymer foam, bone) and in-organic (e.g. silica aerogels) forms. Foams and aerogels are two such materials with numerous engineering and scientific applications such as light-weight cores in sandwich structures, packaging, impact and crash structures, filters, catalysts and thermal and electrical insulators. As such, design and manufacture using these materials is an important task that can benefit significantly from the use of computer aided engineering tools. With the increase in computational power, multi-scale modelling is fast becoming a powerful and increasingly relevant computational technique. Ultimately, the aim is to employ this technique to decrease the time and cost of experimental mechanical characterisation and also to optimise material microstructures. Both these goals can be achieved through the use of multi-scale modelling to predict the macro-mechanical behaviour of porous materials from their microstructural morphologies, and the constituent materials from which they are made. The aim of this work is to create novel software capable of generating realistic randomly micro-structured material models, for convenient import into commercial finite element software. An important aspect is computational efficiency and all techniques are developed paying close attention to the computation time required by the final finite element simulations. Existing methods are reviewed and where required, new techniques are devised. The research extensively employs the concept of the Representative Volume Element (RVE), and a Periodic Boundary Condition (PBC) is used in conjunction with the RVEs to obtain a volume-averaged mechanical response of the bulk material from the micro-scale. Numerical methods such as Voronoi, Voronoi-Laguerre and Diffusion Limited Cluster-Cluster Aggregation are all employed in generating the microstructures, and where necessary, enhanced in order to create a wide variety of realistic microstructural morphologies, including mono-disperse, polydisperse and isotropic microstructures (relevant to gas-expanded foam materials) as well as diffusion-based microstructures (relevant for aerogels). Methods of performing large strain simulations of foams microstructures, up to and beyond the onset strain of densification are developed and the dependence of mechanical response on the size of an RVE is considered. Both mechanical and morphological analysis of the RVEs is performed in order to investigate the relationship between mechanical response and internal microstructural morphology of the RVE. The majority of the investigation is limited to 2-d models though the work culminates in extending the methods to consider 3-d microstructures.
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Thompson, Benjamin Robert. "Hierarchically structured composites and porous materials." Thesis, University of Hull, 2017. http://hydra.hull.ac.uk/resources/hull:16570.
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This thesis develops a hydrogel bead templating technique for the preparation of hierarchically structured composites and porous materials. This method involves using slurries of hydrogel beads with different size distributions as templates. Mixing hydrogel beads with a scaffolding material and then allowing the scaffold to harden, followed by drying of the composite leaves pores in the place of the hydrogel beads. These pores reflect the size and shape of the templates used and the porosity reflects the volume percentage of hydrogel bead slurry mixed with the scaffolding material. A viscous trapping technique has been developed which utilises the viscosity of methylcellulose to stop sedimentation of the scaffold particles during network formation. Both of these methods are attractive due to being cheap, non-toxic and they use food grade materials which allows their use in a multitude of applications. Porous and hierarchically porous gypsum composites have been prepared using both hydrogel bead templating and viscous trapping techniques, or a combination of the two. The level of control over the final microstructure of the dried composites offered by these techniques allowed for a systematic investigation of their thermal and mechanical properties as a function of the pore size, porosity and hierarchical microstructure. It has been shown that the thermal conductivity decreases linearly with increasing porosity, however it was not dependent on the pore sizes that were investigated here. The mechanical properties, however, were significantly different. The porous composites produced with either small hydrogel beads (100 μm) or methylcellulose solution had approximately twice the compressional strength and Young’s modulus compared to the ones produced with large hydrogel beads (600 μm). The sound insulating properties of porous and hierarchically porous gypsum composites have also been investigated. With increasing porosity, the sound transmission loss decreases, as expected. At constant porosity, it is shown that the composites with large pores perform significantly better than the ones with small pores in the frequency range of 75-2000 Hz. At higher frequencies (>2400 Hz) the composites with smaller pores begin to perform better. The material’s microstructure has been studied in an attempt to explain this effect. The hydrogel templating technique can be used to prepare composite materials if the drying step is not performed. Hydrogel beads have been incorporated into a soap matrix. The dissolution rate of these composites as a function of hydrogel bead size and volume percentage of hydrogel beads incorporated within the soap matrix has been investigated. It has been shown that the dissolution rate can be increased by increasing the volume percentage of hydrogel beads used during composite preparation but it is independent on their size distribution. Finally, three methods of controlling the release rate of encapsulated species from these soap-hydrogel bead composites have been shown. The first method involved varying the size distribution of the hydrogel beads incorporated within the soap matrix. The second involved changing the concentration of the gelling polymer and the final method required co-encapsulation of an oppositely charged polyelectrolyte. A binary hydrogel system has been developed and its rheological and thermal properties have been investigated. It consists of agar and methylcellulose and shows significantly improved rheological properties at high temperatures compared to agar alone. The storage modulus of the two component hydrogel shows a maximum at 55 °C which was explained by a sol-gel phase transition of methylcellulose, evidence of which was seen during differential scanning calorimetry measurements. After exposure of this binary hydrogel to high temperatures above the melting point of agar alone (> 120 °C), it maintains its structure. This suggests it could be used for high temperature templating or structuring of food products. The melt-resistant binary hydrogel was used for the preparation of pancake-hydrogel composites using hydrogel bead templating. Mixing slurry of hydrogel beads of this composition with pancake batter, followed by preparation at high temperatures produced pancakes with hydrogel beads incorporated within. Bomb calorimetry measurements showed that the caloric density could be reduced by a controlled amount by varying the volume percentage of hydrogel beads used during preparation of the composites. This method could be applied to other food products such as biscuits, waffles and breakfast bars. Furthermore, there is scope for development of this method by the encapsulation of flavour enhancing or nutritionally beneficial ingredients within the hydrogel beads.
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Haubensak, Frederick G. (Frederick George). "Microstructure design of porous brittle materials." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/26876.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1994.Includes bibliographical references (leaves 214-223).
by Frederick George Haubensak.
Ph.D.
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McMonagle, Charles James. "Effect of pressure on porous materials." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31504.
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Research to design and synthesise new porous materials is a rapidly growing field with thousands of new systems proposed every year due to their potential use in a multitude of application in a wide range of fields. Pressure is a powerful tool for the characterisation of structure-property relationships in these materials, the understanding of which is key to unlocking their full potential. In this thesis we investigate a range of porous materials at a range of pressures. Over time the chemical architecture and complexity of porous materials has increased. Although some systems display remarkable stability to high-pressures, which we generally think of as being above 1 GPa (10,000 bar), in general, the compressibility of porous materials have increased substantially over the last 10 years, rendering most unstable at GPa pressures. Here we present new methods for investigating porous materials at much more moderate pressures (100's of bar), alongside more traditional high-pressure methods (diamond anvil cell techniques), finishing with gas sorption studies in a molecular based porous material. Here, the design and development of a new moderate pressure sapphire capillary cell for the small molecule beamline I19 at the Diamond Light Source is described. This cell allowed access to pressures of more than 1000 bar regularly with a maximum operating pressure of 1500 bar with very precise pressure control (< 10 bar) on both increasing and decreasing pressure. This cell closes the gap between ambient pressure and the lowest pressures attainable using a diamond anvil cell (DAC), which is generally above 0.2 GPa (2000 bar). Along with the development of the sapphire capillary pressure cell, the compression to 1000 bar of the small organic sample molecule Hexamethylenetetramine (hexamine, C6H12N4) and its deuterated form (C6D12N4) was determined, demonstrating the precision possible using this cell. Solvent uptake into porous materials can induce large structural changes at 100's of bar. In the case of the Sc-based Metal-organic framework (MOF), Sc2BDC3 (BDC = 1,4-benzenedicarboxylate), we used the sapphire capillary pressure cell to study changes in the framework structure on the uptake of n-pentane and isopentane. This work shows how the shape and smaller size of n-pentane facilitated the swelling of the framework that could be used to explain the increase in stability of the MOF to applied pressure. The effect of pressure on the previously unreported Cu-framework bis[1-(4- pyridyl)butane-1,3-dione]copper(II) (CuPyr-I) was investigated using high-pressure single-crystal diffraction techniques (DAC). CuPyr-I was found to exhibit high-pressure and low-temperature phase transitions, a pressure induced Jahn- Teller switch (which was hydrostatic medium dependent), piezochromism, and negative linear compressibility. Although each of these phenomena has been reported numerous times in a range of materials, this is to the best of our knowledge the first example to have been observed within the same material. The final two chapters investigate the exceptional thermal, chemical, and mechanical stability of a porous molecular crystal system (PMC) prepared by the co-crystallisation of a cobalt phthalocyanine derivative and a fullerene (C 60 or C70). The stabilising fullerene is captured in the cavity between two phthalocyanines in a ball and socket arrangement. These PMCs retain their porous structure: on the evacuation of solvent of crystalisation; on heating to over 500 K; on prolonged immersion in boiling aqueous acid, base, and water; and at extreme pressures of up to 5.85 GPa, the first reported high-pressure study of a PMC. the reactive cobalt cation is accessible via the massive interconnected voids, (8 nm3), as demonstrated by the adsorption and binding of CO and O2 to the empty metal site using in situ crystallographic methods available at beamline I19, Diamond Light Source.
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Eder, Grace M. "Dye Molecule-Based Porous Organic Materials." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1530012900215452.
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Farghaly, Ahmed A. "Fabrication of Multifunctional Nanostructured Porous Materials." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4189.
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Nanostructured porous materials generally, and nanoporous noble metals specifically, have received considerable attention due to their superior chemical and physical properties over nanoparticles and bulk counterparts. This dissertation work aims to develop well-established strategies for the preparation of multifunctional nanostructured porous materials based on the combination of inorganic-chemistry, organic-chemistry and electrochemistry. The preparation strategies involved one or more of the following processes: sol-gel synthesis, co-electrodeposition, metal ions reduction, electropolymerization and dealloying or chemical etching. The study did not stop at the preparation limits but extended to investigate the reaction mechanism behind the formation of these multifunctional nanoporous structures in order to determine the different factors controlling the nanoporous structures formation. First, gold-silica nanocomposites were prepared and used as a building blocks for the fabrication of high surface area gold coral electrodes. Well-controlled surface area enhancement, film thickness and morphology were achieved. An enhancement in the electrode’s surface area up to 57 times relative to the geometric area was achieved. A critical sol-gel monomer concentration was also noted at which the deposited silica around the gold coral was able to stabilize the gold corals and below which the deposited coral structures are not stable. Second, free-standing and transferable strata-like 3D porous polypyrrole nanostructures were obtained from chemical etching of the electrodeposited polypyrrole-silica nanocomposite films. A new reaction mechanism was developed and a new structural directing factor has been discovered for the first time. Finally, silver-rich platinum alloys were prepared and dealloyed in acidic medium to produce 3D bicontinuous nanoporous platinum nanorods and films with a nanoporous gold-like structure. The 3D-BC-NP-Pt displayed high surface area, typical electrochemical sensing properties in an aqueous medium, and exceptional electrochemical sensing capability in a complex biofouling environment containing fibrinogen. The 3D-BC-NP-Pt displayed high catalytic activity toward the methanol electro-oxidation that is 30 times higher that of planar platinum and high volumetric capacitance of 400 F/cm3. These findings will pave the way toward the development of high performance and reliable electrodes for catalysis, sensing, high power outputs fuel cells, battery-like supercapacitors and miniaturized device applications.
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Richards, Emma. "Immobilisation of polyazamacrocycles into porous materials." Thesis, University of Liverpool, 2012. http://livrepository.liverpool.ac.uk/8513/.
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The synthesis and characterisation of functionalised polyazamacrocycles and their subsequent immobilisation into porous materials were investigated and reported in this thesis. The incorporation of polyazamacrocycles into porous materials offers the potential to enhance their biomimetic and environmental properties with tuneable microenvironments around the macrocycles. Nine polyazamacrocycles have been synthesised that are functionalised with vinyl, pyridyl, carboxylate and iodide pendant arms in order to immobilise them into porous materials. Of these macrocycles nine metal complexes were successfully synthesised and their crystal structures are discussed. The most interesting of these metal complexes are complex 2, a cyclam based metal complex and complex 7, a [12]aneN3 based metal complex which both have coordinated water molecules and therefore are activated for hydrolase activity. Polyazamacrocycles have successfully been immobilised into organic cross-linked polymers using polar and non-polar cross-linkers and a systematic investigation has taken place in order to determine the effects of the nature and amount of porogen and the concentration of macrocycle within the polymer on the porous properties of the polymer. These effects include BET surface area, shape and size distributions of pores, and CO2 uptake capacities. The effect of incorporation of metal complexes and metal ions is also discussed. It was found that with non-polar based polymers, BET surface areas were find to be higher when non-polar porogens were employed and decrease with increasing polarity of the porogen. However, the nature of the macrocycle also plays an important role in the porosity of the resulting polymers. Zinc and copper metal organic frameworks containing cyclam based macrocycles with pyridyl pendent arms have been synthesised with 2D layered structures. The crystal structures reveal that triflate and hexafluorophosphate counterions play an important role in stabilisation of the framework but with the disadvantage of blocking possible porosity.
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Acartürk, Ayhan. "Simulation of charged hydrated porous materials." Essen VGE, 2009. http://d-nb.info/998591939/04.
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Cooper, Emma. "Renewable routes to porous aluminosilicate materials." Thesis, University of York, 2012. http://etheses.whiterose.ac.uk/3936/.
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The objectives of this project were to synthesise zeolites and aluminosilicate materials from silicon sources derived from biomass ashes. These materials will have great potential as catalysts and adsorbents. In order to begin this study it was necessary to find and optimise a technique for extraction of silicon to an alkali silicate solution from biomass ashes. It was then necessary to develop a technique for analysis of the alkali silicate solutions. This was done using calibration of integrals from infrared spectra. An optimisation of the synthesis of Zeolite X from a rice hull ash derived alkali silicate was developed and these materials were analysed and characterised using XRD, N2 Adsorption porosimetry, X‐Ray Fluorescence Spectroscopy, and X‐Ray Photoelectron Spectroscopy. An in‐depth study of the surface of the ash derived and reference Zeolite X was undertaken using in situ small molecule probing FT‐IR. It was found that although the materials were similar there was a significant difference due to the presence of a strongly bonded carbonate species in the pores of the bio‐derived zeolite. Synthesis of a Miscanthus ash derived mesoporous silica, MCM‐41, was successfully achieved which was comparable to its conventionally synthesised equivalent. Both displayed ordered hexagonal pores and high surface areas. A study on addition of different sources of aluminium found that it was possible to introduce aluminium into the structure successfully. Included in this study was the addition of the waste product ‘red clay’ as an aluminium source. Another mesoporous silica, SBA‐15 was synthesised from a Miscanthus ash derived alkali silicate. It was necessary to optimise the synthesis to adapt to the different pH systems of the conventional method and bio‐derived alkali silicate solutions. This was achieved and a bio‐derived SBA‐15 material with ordered hexagonal pores was produced.
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Lopes, Felipe Robles. "Estudos experimentais de danos de formação em meios porosos." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265225.
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Orientador: Rosângela Barros Zanoni Lopes MorenoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica e Instituto de Geociências
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Resumo: A invasão de fluidos de perfuração e suas consequências na produção de petróleo são bem conhecidas e intensivamente discutidas por especialistas. Além disso, a comunidade científica tem buscado o entendimento dos mecanismos de invasão e do retorno de permeabilidade. Este estudo estende investigações anteriores sobre análise de dano e inclui as etapas de invasão de fluido de perfuração e de fluxo reverso de óleo. Foram realizados testes de invasão de fluidos base-água, soluções de goma xantana e de poliacrilamida, à pressão constante, em amostras saturadas com óleo e água conata. Usando um porta-testemunho especial, perfis de saturação e de pressão foram monitorados durante a invasão e o fluxo reverso, permitindo a observação das características do processo de invasão e de remoção do dano de forma dinâmica. A condição de saturação da amostra antes da invasão de polímero, óleo e água conata, permitiu melhorar a representatividade de um reservatório de petróleo. O monitoramento da pressão ao longo da direção de escoamento e varreduras de Raios-X combinados com o balanço de massa de fluidos injetados e produzidos permitiu observar o avanço do fluido invasor. Durante o fluxo reverso foi possível acompanhar dinamicamente a mudança de permeabilidade da região invadida. As principais contribuições deste estudo referem-se à análise do retorno de permeabilidade devido à produção de óleo em uma região danificada pela invasão do fluido de perfuração, bem como a influência da presença de água conata nestes processos
Abstract: Invasion of drilling fluids and their effects on oil production are well known and have been extensively discussed by experts. Furthermore, the scientific community has invested a lot of effort into understanding the mechanisms of invasion and permeability restoration. This study extends previous investigations and includes both invasion and back flow evaluation conditions. Test sample, initially at connate water condition, were submitted to constant pressure displacement. Using a special core holder, saturation and pressure profiles were monitored during overbalance pressure invasion and oil back flow. Monitored data has allowed observing the formation damage characteristics as well as cleaning dynamics. In this work, polymer injection into the sample at residual water saturation has improved the reservoir representation. The pressures data, from the taps along the core, X-Ray data and also the mass balance allow the author to follow the invasive fluid going through the core. Additional insights about dynamic mechanisms were also discussed based on a large quantity of monitored data. During the back flow was possible to dynamically monitor the change of permeability of the invaded region. The main contributions of this study are related to the analysis of the permeability restoration due to oil natural cleanup of the region damage by drill in fluid. The influence of connate water in this process was also important
Mestrado
Reservatórios e Gestão
Mestre em Ciências e Engenharia de Petróleo
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Biju-Duval, Paul M. "A new porous material based on cenospheres." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/26523.
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Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2008.Committee Chair: Dr. Mulalo Doyoyo; Committee Member: Dr. Arash Yavari; Committee Member: Dr. Kenneth M. Will. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Rioux, Ran Wei. "The Rate of Fluid Absorption in Porous Media." Fogler Library, University of Maine, 2003. http://www.library.umaine.edu/theses/pdf/RiouxRW2003.pdf.
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Kou, Shuting, and 寇舒婷. "Porous structure modeling with computers." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206700.
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Porous structures are a particular type of solids, where a large number of pores exist in the geometric domain of interest. Research on porous structures have received increasingly keen interest in recent years and this is largely because of many unique and superior properties that porous structures possess. They can undertake special tasks which general solid materials are not competent to do.
In recent twenty years numerous representations are put forward for porous structure modeling. But the challenges in practical porous structure design still exist and the structure heterogeneity brings many difficulties. This thesis is motivated to propose new porous structure modeling strategies which are more accurate, flexible and easy for porous structure description.
An approach of porous structure modeling based on quadtree/octree and NURBS is proposed first. Quadtree and octree are tools for modeling domain partition. The pore size and pore distribution are controlled by the flexibility of quadtree and octree enumeration technique. Derived polygon and polyhedron are then introduced to assist the generation of NURBS curves and surfaces. These NURBS curves and surfaces form the boundaries of the porous structures.
However there are limitations of the above method. The accurate control of porosity is not easily achieved in 3D porous structure modeling and seemingly adopting quadtree/octree for the modeling domain partition is also less than satisfactory. Hence a new representation for porous structures based on Centroidal Voronoi tessellation (CVT) and pore-network is put forward. CVT is utilized for modeling domain partition because the CVT cells are approximate hexagons which is widely existent in plants, animals and other cellular structures in nature. The density distribution function used in CVT generation also helps to build functionally graded porous structures. Pore-network, which is a mature and commonly used model in the research of multiphase flow in porous media, is subsequently introduced to build the porous structures. This modeling approach results in porous structures that could mimic the geometry and performance of structures in nature.
To evaluate the object’s properties, finite element analysis (FEA) is conducted on the porous structure models represented by the two methods. The mechanics properties of the two types of models are analyzed. The stress-strain curve of each sample is plotted and the effective Young’s modulus is calculated. Comparison of these two types of models is also done. Besides, the contributions of the thesis and suggestions for future research are also discussed.published_or_final_version
Mechanical Engineering
Master
Master of Philosophy
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Chow, Hon-nin, and 周漢年. "Computer aided modelling of porous structures." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B39848929.
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Lizardi-Mendoza, Jaime. "Structured porous materials of chitin and chitosan." Thesis, Queen's University Belfast, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486244.
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Chitin is an abundant polysaccharide that is mainly found in the exoskeleton of arthropods (insect, crustaceans, etc.). It is chemically and structurally similar to cellulose but chitin has an acetamido group in the second position: Chitosan, the main derivative ofchitin, is deacetylated leaving the amide groups uncovered and liable to be protonated in acid environments. These together with other features provide chitin and chitosan with a range of distinctive functional properties that including structural qualities, adsorption capacity, reactivity, biocompatibility, bioactivity and biodegradability. Such chitin and chitosan properties have been the origin of increasingly interest and oftheir application in diverse fields. In order to improve the availability ofthe functional groups ofchitin and chitosan in the solid stat~ it is proposed the generation ofporous materials with large surface area. The proposal is remove the liquid phase of chitin and chitosan physical gels using C02 critical point drying to minimize the disruption of the formed microstructure. The analysis of the diverse solution characteristics and their relationships with' the features ofthe gel and porous structures produced provide basic information that could allow the design offunction specific structures. Two types ofchitin solutions were obtained using dimethylacetamide containing 5% LiCI and cold «4°C) 10% NaOH as solvents. Chitosan was dissolved in diluted acetic acid and in formaldehyde sodium bisulfite (FSB) solution. Homogeneously deacetylated chitosan was obtained and dissolved in water. The basic characterisation ofthe solutions indicate that the molecular interaction ofthe polysaccharide with each solvent is distinctive. Every solution type were cast and physical gels were generated by diffusion of gelating agent fumes. Additionally, gels of alkali chitin (chitin in 10% NaOH) were produced by thermal treatment. Once washed, a portion of each type ofgel was equilibrated in water and other part in acetone; except the homogeneous chitosan gels that were equilibrated only in acetone. The water gels were freeze dried and the acetone was removed by C02 critical point drying to get porous materials. The porous structure of such materials were analyzed by scanning electron microscopy, crystallinity, chemical compositionand BET gas adsorption. The freeze dried materials have porous structure morphology similar to what has been previously reported. On the other hand, most ofthe critical point dried porous structures are in the mesoporous range and have large specific surface areas (323-887 m2/g). Apparently, for this tYpe ofmaterials the molecular interactions occurring in the solution could be related with the morphology of their respective porous structure
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Ridgway, Catherine Jean. "Modelling pore-level properties of porous materials." Thesis, University of Plymouth, 1995. http://hdl.handle.net/10026.1/1707.
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Pore-Cor is a 1.2 Mbyte Fortran 77 software package, which uses information from mercury porosimetry curves, supported by image-analysed electron micrographs, to generate a three-dimensional representational model of the pore-space within a porous material. As a result of this project, a much-improved version has been produced. The mercury intrusion curves for the simulated structures now converge automatically onto the experimental curves, so reducing the simulation time from several days to less than an hour. A further time economy has been provided by the incorporation of an improved permeability routine, reducing the calculation time from 10 minutes to 30 seconds. Modifications have allowed non-homogeneous structures to be modelled, in simulation of real samples of banded, vuggy and clay-included sandstones. Porosimetry measurements have been made for Fontainebleau sandstone into which small amounts of illite, a simulated clay deposit, had been introduced by hydrothermal crystallisation. Despite having no effect on porosity, the effects on simulated permeability could be successfully assessed. The causes of hysteresis, i.e. the trapping of a non-wetting fluid in a porous medium, were also investigated. The need for higher quality experimental data to feed into the Pore-Cor software has led to improved measurement and analysis methods for the porosimetry. A new spreadsheet-based iterative programme, named Pore-Comp. provides a unique method of measuring the compressibility (or bulk modulus) of the solid phase of a porous medium, and this has been used to examine the effects of silicate micro-crystallinity and latex binders on the compressibility of paper-coating formulations. Using the cryo-stage of the electron microscope, the retention of mercury in some paper coating formulations has been investigated further.
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Wilcox, O. T. "Porous materials for the uptake of ammonia." Thesis, University of Liverpool, 2017. http://livrepository.liverpool.ac.uk/3007235/.
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Mohamed, Rozita. "Preparation of nano-structured macro-porous materials." Thesis, University of Newcastle upon Tyne, 2011. http://hdl.handle.net/10443/1317.
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This research reveals a catalyst development towards achieving catalysts with hierarchical porous structures with enhanced mechanical properties by using nano-structured macro-porous PolyHIPE polymer. This work can be divided into two parts: the fabrication and its characterisation of hierarchical metal structure using PHP and other fibre materials; and the fabrication and characterisation of PHP with silica particles and glass wool, further coated with silane material as templates. A catalyst system was successfully fabricated forming a 3D-interconnecting network of pore size, ranging from tens of micrometers and gradually reducing finally to nanometer scale. An electroless deposition flow through method using Ni-B bath solution was performed on the templates and was subsequently heat treated to obtain porous metallic structures, thus providing accessibility for reactants to the surface and for products away from the surface. Meanwhile, silanated templates were produced by surface treatment. This was performed by submerging templates directly into the silanes solution at room temperature (24°C) using a water-ethanol based solution of the silanes. The polymer-metal/alloy or silica functionalized based composite demonstrated a high impact strength. The results showed that not only hierarchical pore structure was formed, but it was also demonstrated that silica particles were totally and uniformly covered/coated by metal deposit and had good adhesion. When used on glass wool, silanation had greatly improved the bond strengths of metal deposits to the templates. SEM micrographs revealed that the formation of cracks were tremendously reduced and exhibited higher bond strengths due to silanated glass surface. It is expected to be more efficient and robust in the case of an enhanced surface area, and most desirable in catalyst applications.
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Littlefield, Benjamin T. R. "Solvothermal synthesis of porous beryllate containing materials." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/359297/.
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Natural and synthetic zeolites have been the focus for extensive research owing to their many applications and huge potential number of new topologies. The work presented here represents the first major study into the formation of zeotypical materials incorporating BeO4 and T5+O4 (T5+ = As or P) tetrahedra and a large number of new structures have been produced. These novel materials have been synthesised via hydrothermal procedures and characterised via Single Crystal X-ray Diffraction, supported by Powder X-ray Diffraction, Thermogravimetric Analysis, Magic Angle Spinning Nuclear Magnetic Resonance and Electron Dispersive Spectroscopy. The berylloarsenates produced encompass the entire range of dimensionality, from cluster structures such as Na3.5[AsO4(BeF3)(BeF2)]•0.4H2O to the novel three dimensional framework [Hbis( 2-ethylhexyl)amine, NH4] [(AsO4)3(AsO3OH)Be3(BeOH)] and include analogues of known zeolite topologies; MER, AFI and WEI. Four completely novel fully connected three-dimensional zeolitic topologies are also reported with one already being assigned the Framework Type code of BOZ. These new topologies represent the most structurally complicated zeolites known and are remarkable in their high calculated internal pore volume. The berylloarsenates are supported by parallel research into the beryllophosphates which has produced unusual new structures of low dimensionality such as the one dimensional chain Na2[(BeO2OH)(PO2)]•H2O as well as structural analogues of the berylloarsenate structures including [H-pyridine][(BeO4)2BeO3(OH2)P3(OH)] which exhibits the AFI topology. These structures could potentially be used in catalysis, ion exchange and due to their low framework density, gas storage. A short investigation into other beryllate chemistry is also presented which includes the novel two dimensional structures Na[BeGeO3(OH)] and Ba[BeGeO3(OH)] which significantly contribute to the sparse field of beryllogermanates. This section also contains the first structural characterisation of Sr[Be(OH)4], a vital species in beryllium solution chemistry.
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Panella, Barbara. "Hydrogen storage by physisorption on porous materials." [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-29012.
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Yan, Xuecheng. "Carbon-based Porous Materials for Electrochemical Reactions." Thesis, Griffith University, 2016. http://hdl.handle.net/10072/366852.
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The exploration of highly active and durable cathodic oxygen reduction reaction (ORR) catalysts with economical production cost is still the bottleneck to realize the large-scale commercialization of some emerging technologies, such as fuel cells and metal-air batteries. At present, the composite that contains expensive platinum (Pt) particles dispersed on a porous carbon support (e.g., activated carbon (AC)) is the most efficient ORR catalyst. In a common sense, the AC itself normally shows very low activity for the ORR, so the Pt particles are vital. Imagine that if we remove all of the Pt particles, can the remaining AC still play the similar role? The current work aims to make the inert AC active for the electrochemical reactions by creating unique defects in the AC.
First of all, different porous carbon materials with variable specific surface areas were synthesized by an easy and scalable chemical activation method. It is shown that all the activated samples demonstrate obviously improved ORR activity. Afterwards, the unique defects were introduced into the activated ACs via a facile nitrogen doping and removal approach to further enhance their catalytic performance, based on the defective mechanism that was proposed in our group, in which the nitrogen was incorporated into the ACs under an ammonia atmosphere at 500 °C and subsequently removed at 1050 °C under a nitrogen environment. The results showed that the doped nitrogen did not enhance the ORR performance of the synthesized samples directly, but the produced defects possibly served as the active sites for the ORR, which finally contributed to the catalytic performance improvement. Particularly, the resulting defective carbon (D-AC) derived from the highest surface area AC (3508 m2/g) also exhibits the best ORR performance in alkaline medium with low overpotential. For example, the ORR activity of the D-AC is comparable to the commercial Pt/C (20 wt% Pt) in terms of 4-electron pathway, half-wave potential and limiting current density, namely, 3.6, 0.771 V and 4.4 mA·cm-2 vs 3.9, 0.785 V and 5.0 mA·cm-2, respectively. Meanwhile, the D-AC also exhibits excellent HER activity, which is better than most of the reported metal-free HER catalysts, but with much lower production cost.School of Natural Sciences
Science, Environment, Engineering and Technology
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Kunjir, Shrikant. "Study of new porous materials by NMR." Thesis, Normandie, 2018. http://www.theses.fr/2018NORMC211/document.
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Les zéolites sont des «tamis moléculaires» connus pour leurs nombreuses applications en adsorption, échange d'ions et catalyse. Dans cette thèse, nous nous sommes concentrés sur l'étude de quelques questions liées à la synthèse et à la post-synthèse de la zéolithe, qui ne sont pas encore résolues par d'autres techniques.La RMN a été l'outil principal dans ce travail, donnant accès à des informations structurales locales sur les nanocristaux même lorsque les techniques de diffraction trouvent leurs limites. Elle peut également être utilisée pour étudier la porosité en utilisant l'adsorption de molécules sondes, et en particulier, le xénon est connu comme une bonne molécule pour cet objectif. En effet, l'isotope 129Xe peut être hyperpolarisé pour augmenter la sensibilité de détection, et il présente une large plage de déplacement chimique en fonction du confinement et donc de la porosité du matériau étudié.(I) Dans la première étude, les étapes initiales de la cristallisation de nano-faujasite (FAU) ont été étudiées en utilisant la RMN classique (principalement par 29Si et 23Na MAS RMN) et la RMN avancée (129Xe). RMN HP). Il a été montré que la cristallisation commence à des stades de synthèse bien antérieurs à ceux observés par d'autres techniques classiques (XRD, SEM, adsorption de N2 ...). La première SBU semble être les prismes hexagonaux, avant les cages sodalite, qui forment rapidement un environnement confiné puis des supercages. De plus, il a été démontré par RMN 129Xe HP et 2D EXSY que la zéolithe nano-faujasite présente des cages sodalite ouvertes et une structure plus souple que dans la zéolite de type micro-faujasite.(ii) La seconde étude est une recherche sur les phénomènes de recristallisation survenant au cours du processus de hiérarchisation de la zéolithe et qui pourrait expliquer la distribution homogène des tailles de mésopores. Comme résultat remarquable, il a été montré dans ce travail que lors de la hiérarchisation de la zéolithe bêta avec le TPAOH, la recristallisation conduisait à la formation de minuscules particules de MFI, formées à la surface des mésopores (RMN 1H MAS, RMN 129Xe HP et 2D EXSY)The zeolites are ‘molecular sieves’ known for their numerous applications in adsorption, ion exchange, and catalysis. In this thesis, we focused on the study of some questions related to zeolite synthesis and post-synthesis, which are not yet resolved by other techniques. NMR was the primary tool in this work, as it gives access to local structural information on nanocrystals even when diffraction techniques found their limits. NMR can also be used to study porosity using probe molecules adsorption, and in particular, xenon is known as a good molecule for this purpose. Indeed, the isotope 129Xe can be hyperpolarized to increase the detection sensitivity, and interestingly it presents a wide chemical shift range depending on its confinement and thus the porosity of studied material. Two studies are reported in this manuscript: (i) In the first study, the initial steps during the crystallization of nano-faujasite (FAU) type materials were investigated using classical NMR (mainly by 29Si and 23Na MAS NMR) and advanced NMR (129Xe HP NMR). It was shown that crystallization starts at much earlier synthesis stages than those observed by other classical techniques (XRD, SEM, N2 adsorption…). The first SBU seems to be the hexagonal prisms, prior to the sodalite cages, which rapidly form confined environment and then supercages. Moreover, it has been proved by 129Xe HP NMR and 2D EXSY that nano-faujasite zeolite presents opened sodalite cages and a more flexible structure than in micro-faujasite zeolite. (ii) The second study is an investigation on the recrystallization phenomena occurring during hierarchization process of zeolite and which could explain the homogenous distribution of the mesopore sizes. As a remarkable result, it has been shown in this work that during the hierarchization of beta zeolite with TPAOH, the recrystallization lead to the formation of tiny MFI particles, formed at the surface of the mesopores (1H MAS NMR, 129Xe HP NMR and 2D EXSY)
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Cervin, Nicholas. "Porous Cellulose Materials from Nano Fibrillated Cellulose." Licentiate thesis, KTH, Fiberteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-104196.
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In the first part of this work a novel type of low-density, sponge-like material for the separation of mixtures of oil and water has been prepared by vapour deposition of hydrophobic silanes on ultra-porous nanocellulose aerogels. To achieve this, a highly porous (> 99 %) nanocellulose aerogel with high structural flexibility and robustness is first formed by freeze-drying an aqueous dispersion of the nanocellulose. The density, pore size distribution and wetting properties of the aerogel can be tuned by selecting the concentration of the nanocellulose dispersion before freeze-drying. The hydrophobic light-weight aerogels are almost instantly filled with the oil phase when they selectively absorb oil from water, with a capacity to absorb up to 45 times their own weight. The oil can also be drained from the aerogel and the aerogel can then be subjected to a second absorption cycle.In the second part of the work a novel, lightweight and strong porous cellulose material has been prepared by drying aqueous foams stabilized with surface-modified NanoFibrillated Cellulose (NFC). Confocal microscopy and high-speed video imaging show that the long-term stability of the wet foams can be attributed to the octylamine-coated, rod-shaped NFC nanoparticles residing at the air-liquid interface which prevent the air bubbles from collapsing or coalescing. Careful removal of the water yields a porous cellulose-based material with a porosity of 98 % and a density of 30 mg cm-3. These porous cellulose materials have a higher Young’s modulus than other cellulose materials made by freeze drying and a compressive energy absorption of 56 kJ m-3 at 80 % strain. Measurements with an autoporosimeter reveal that most pores are in the range of 300 to 500 μm.QC 20121107
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Mochizuki, Shuto. "Controlled radical polymerization in designed porous materials." Kyoto University, 2019. http://hdl.handle.net/2433/242535.
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Lutzweiler, Gaëtan. "Porous polyurethane-based materials for tissue engineering." Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAE019/document.
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Les matériaux poreux représentent une solution idéale en ingénierie tissulaire car leur structure peut offrir un environnement tridimensionnel aux cellules similaire à leur matrice extracellulaire tout en maintenant de bonnes propriétés mécaniques. Une première partie de cette thèse consiste à développer des matériaux poreux en polyuréthane (PU), dont l’architecture est contrôlée pour favoriser au mieux la survie et la croissance des cellules. Ces matériaux sont combinés à des traitements de surface (revêtement de polydopamine (PDA) et traitement plasma) pour augmenter notamment l’adhésion des cellules. Nous avons pu démontrer que le diamètre des interconnexions (i.e. l’ouverture connectant deux pores adjacents) impacte profondément la survie et l’organisation des cellules à long terme dans le matériau. Le revêtement de PDA s’est révélé efficace pour des cellules de type fibroblaste, alors que le traitement plasma favorise la colonisation des cellules souches mésenchymateuses (MSCs). Par ailleurs, nous avons étudié l’influence de la formulation du PU sur les capacités d’adhésion des cellules au matériau. Nous avons démontré que pour un ratio donné entre les réactifs, l’adhésion des cellules peut être exclue ou permise. Finalement, nous avons mis un gel de peptides auto-assemblés dans les pores du matériau pour fournir aux cellules un environnement similaire à leur matrice extracellulaire. Nous avons pu montrer que le gel permet d’augmenter la prolifération des MSCsPorous materials are an ideal solution in tissue engineering since they can provide a three-dimensional environment to the cells that is close to their extracellular matrix while keeping suitable mechanical properties. In the first part of this Thesis we develop porous materials made from polyurethane (PU) whose architecture is controlled to allow cells colonisation and growth. These materials are subsequently surface-treated (polydopamine (PDA) coating and plasma treatment) to enhance the adhesion of the cells. We were able to show that the interconnection diameter (i.e. the aperture connecting two adjacent pores) has an important impact on the long-term cell survival and organization in the material. Polydopamine coating was shown to be efficient for fibroblasts, whereas plasma treatment promoted mesenchymal stem cells (MSCs) colonisation. Besides, we also studied the influence of the PU formulation on the adhesion capacity of the cells. We demonstrated that at a given ratio between the reactants, cell adhesion could be allowed or prevented. Finally, we put a hydrogel of self-assembled peptides inside the pores of the material to provide an environment close to the extracellular matrix for the cells. We could show that the gel increases the proliferation ability of MSCs. In summary, this Thesis puts forward the important interplay between material properties and morphology of porous scaffolds
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TANZI, MARLOTTI GIACOMO. "THEORY OF POSITRONIUM INTERACTIONS WITH POROUS MATERIALS." Doctoral thesis, Università degli Studi di Milano, 2018. http://hdl.handle.net/2434/609709.
Full textAbstract:
The work in this thesis is focused on studying the behavior of a positronium
atom (Ps) inside matter and especially in porous materials. The need for im-
proved theoretical models is justified by the lack of a simple explanation for
the well known phenomenon of the lowering of the contact density, a parameter
describing the electron density at the positron position.
Given that this parameter is experimentally accessible, connecting its value
to specific properties would be extremely useful in the context of structural
analysis of materials. In the first two chapters we will give an introduction to
positronium physics and an overview of methods and models commonly used
by the positron community.
In the third chapter we analyze a simple two-particle model we formulated
to describe Ps confined in nanopores.
This model is based on the observation that the confining potential acting
on Ps is a net result of two independent and different contributions, acting on
the electron and on the positron separately. In particular, a positive value for
the positron work function, as derived by theoretical models and found, for
example, in silica, suggests that the positron is attracted toward the medium
and then is not confined a priori.
The well known confining behavior of Ps is then related to the repulsive
electron-electron interaction at short distances and to the strong Pauli exchange
forces with bulk electrons. In this picture, it is the electron in o-Ps that prevents
large overlap between Ps and electrons in matter.
By applying approximate semi-analytical techniques, a variational method
approach, and finally a quantum montecarlo code, we were able to demonstrate
that our model correctly describe the lowering of the contact density, obtaining
also promising results in the comparison with experimental data.
However this model was not fully satisfactory because it is based on a macro-
scopic parameter (the positron work function) which is not easy to obtain ex-
perimentally.
For this reason in the fourth chapter we will provide some theoretical insight
about Ps interactions with external electrons, taking into account correlation as
well as exchange interactions.
Given the difficulty of the general problem itself we focused on a system
of Ps interacting with a homogeneous electron gas (HEG). We will show that
this calculation recover the same result obtained for a positron-HEG system in
the limit of high density, while on the opposite limit we recover two different
annihilation rates for o-Ps and p-Ps as expected fo Ps in a free space region. We
will formally prove that the pickoff annihilation rate has the same expression
both for o-Ps and p-Ps , a result which was never proved for a system of N
electrons. Finally we will show how the presence of a low external electron
density manage to screen the positron charge effectively lowering the contact
density, with a mechanism which can be seen as a Ps negative ion formation.
In the last chapter we will give a comparison of our results with experimental
data.
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Crimm, Robert Prentiss. "Experimental apparatus for measuring moisture transfer in porous materials subject to relative humidity and temperature differences." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-01122010-020146/.
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Qiao, Chongzhi. "Theoretical study of fluid adsorption in porous materials." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEN051/document.
Full textAbstract:
Les matériaux poreux ont une importance stratégique en génie chimique, par exemple en capturant les gaz à effet de serre, la séparation et la purification, les catalyseurs et la conception de capteurs. En raison de la diversité des matériaux poreux et des propriétés thermodynamiques des fluides confinés affectés par autant de matériaux et de propriétés des fluides, les méthodes classiques de la mécanique statistique sont encore étudiées au cas par cas, ce qui rend difficile l’offre des variables de contrôle. de fluide confiné ni pour fournir un motif régulier de fluide confiné. L'élaboration de théories thermodynamiques ou des lois d'échelle universelles permettant de décrire avec précision les fluides confinés devient de plus en plus importante. Cette thèse étudie la relation entre le fluide confiné et le fluide en vrac correspondant, les propriétés interfaciales des fluides sur une surface courbe, l'équation d'état générale des fluides confinés et l'effet de trempe.Une relation de mise à l'échelle générale relie le fluide confiné et le fluide en vrac. Cette relation d'échelle montre que la différence de propriétés thermodynamiques entre un fluide confiné et un fluide en vrac peut être décrite uniquement par la porosité, la quantité d'adsorption en excès et la pression du système en vrac équilibré. La relation intrinsèque entre la relation d’échelle et la théorie d’adsorption de Gibbs est également révélée. En combinant le SPT et la thermodynamique morphologique, nous avons d'abord proposé un SPT augmenté pour explorer les propriétés interfaciales des fluides sur une surface incurvée. En introduisant un terme de courbure d'ordre supérieur, une nouvelle équation d'état offrant une expression plus précise de la tension interfaciale d'un fluide sur une surface sphérique est obtenue. Pour construire une équation d'état générale pour des fluides confinés et explorer les variables de contrôle des fluides confinés, en combinant thermodynamique morphologique et SPT, nous avons introduit la première équation d'état pour un fluide confiné, sans rapport avec le modèle de matériau poreux. Dans cette équation d'état, quatre propriétés géométriques du matériau poreux, à savoir la porosité, l'aire de l'interface solide-fluide, la courbure moyenne et la courbure gaussienne, sont considérées comme des variables de contrôle. Les variables indépendantes sont le potentiel chimique et la température. Les résultats de cette équation d'état concordent parfaitement avec la simulation moléculaire. L'effet de confinement est lié à son potentiel chimique. Nous avons d’abord étudié l’influence des conditions confinées sur le potentiel chimique des fluides. Les résultats montrent qu’une augmentation du potentiel chimique, ce qui signifie que l’augmentation de la résistance des fluides dans les matériaux poreux peut être obtenue en réduisant la porosité, en augmentant la densité du fluide ou en augmentant la surface d’interface solide-liquidePorous materials have strategically important in chemical engineering, e.g., capturing Greenhouse gas, separation and purification, catalysts, and design of sensors. Due to the variety of porous materials, and thermodynamic properties of confined fluid are affected by so many materials and fluid properties, studies of classical statistical mechanic methods are still on a case-by-case way, which is hard to offer neither the control variables of confined fluid nor to provide a regular pattern of confined fluid. The development of thermodynamic theories or the universal scaling laws that can accurately describe confined fluids becomes more and more important. This thesis investigates the relation between confined fluid and the corresponding bulk fluid, interfacial properties of fluids at a curved surface, the general equation of state for confined fluids, and quench effect.With the help of scaled particle theory (SPT) and molecular simulation, a general scaling relation that connects the confined fluid and bulk fluid is found. This scaling relation shows that the difference of thermodynamics properties between confined fluid and bulk fluid can be described by only porosity, excess adsorption amount, and the pressure of equilibrated bulk system. The intrinsic relation between scaling relation and Gibbs adsorption theory is also revealed. By combining SPT and morphological thermodynamics, we first proposed an augmented SPT to explore the interfacial properties of fluids at a curved surface. By introducing a higher order curvature term, a new equation of state which offers a more accurate expression of the interfacial tension of fluid at a spherical surface is derived. To construct a general equation of state for confined fluids and explore the control variables of confined fluids, by combining morphological thermodynamic and SPT, we introduced the first equation of state for confined fluid which is irrelevant to the model of porous material. In this equation of state, four geometric properties of porous material, i.e., the porosity, the area of solid-fluid interface, integrate mean and Gaussian curvature are considered as control variables. Independent variables are chemical potential and temperature. Results from this equation of state have a great agreement with molecular simulation in a wide range. The confinement effect is related to its chemical potential. We first studied the influence of confined conditions on the chemical potential of fluids. Results show that an increase on chemical potential, which means the increase of resistance of fluids into porous materials can be led by reducing the porosity, or increasing the fluid density, or increasing the area of solid-liquid interface
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Sun, Ssu-Hsueh. "Finite element analyses of coupled heat and moisture transport in cylindrical porous media and coal logs /." free to MU campus, to others for purchase, 1997. http://wwwlib.umi.com/cr/mo/fullcit?p9841186.
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Passos, Aline Ribeiro [UNESP]. "Aluminas macro-mesoporosas produzidas pelo método sol-gel para aplicação em catálise heterogênea." Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/136086.
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000854657.pdf: 7039373 bytes, checksum: e3e464e79dbd92c0c088c22c6648dea7 (MD5)Alumina é um suporte importante em catálise heterogênea. O controle das propriedades física e texturais pode melhorar seu desempenho como suporte em aplicações de catálise. Os catalisadores de cobalto são conhecidos por apresentarem excelente performance na reação de reforma de etanol (ESR) devido a elevada capacidade de quebra das ligações C-H e C-C. Muitos estudos visam correlacionar as propriedades das aluminas com o desempenho dos catalisadores. As aluminas exibem uma química de superfície complexa que pode ser controlada pelo método de preparação. Neste trabalho aluminas com meso e macroporos foram obtidas usando o método sol-gel acompanhado de separação de fases. Nesta estratégia integrativa a gelatinização e a separação de fases ocorrem de maneira espontânea no sistema contendo um indutor de separação de fases. Diferentes alumina foram produzidas a partir do isopropóxido e cloreto de alumínio e do óxido de polietileno e óxido de polipropileno como indutores de separação de fases. A escolha apropriada da composição de partida permite o controle do tamanho e volume dos poros. Os macroporos são formados como resultado da separação de fases após remoção do indutor de separação de fases, enquanto os mesoporos são formados entre as partículas do xerogel. As diferentes aluminas porosas preparadas e uma alumina comercial foram utilizadas como suporte de catalisadores de cobalto. Os precursores óxidos dos catalisadores obtidos após calcinação são compostos pelas fases Co3O4 e CoAl2O4, esta última em maior quantidade nas aluminas sintetizadas via sol-gel. As aluminas sol-gel possuem maior proporção de Al em sítios octaédricos e grupos hidroxilas superficiais do que a alumina comercial, verificou-se que estas características podem facilitar a migração de íons de Co na rede da alumina levando a maior formação de CoAl2O4. Os catalisadores foram...
Alumina is an important support for heterogeneous catalysts. The matching of appropriate alumina physical properties and controlled textural properties can improve its performance as support in catalysis applications. Cobalt based catalysts have been reported to have a good ethanol steam reforming (ESR) performance due to their high activity for the cleavage of C-H and C-C bonds. Many studies have been conducted about the effects of alumina properties on the cobalt catalysts properties. Alumina exhibits a rather complex surface chemistry which can be controlled by the preparation procedure. In this work alumina samples with macro and mesoporous structure were obtained using the one-pot sol-gel synthesis accompanied by phase separation. In this integrative strategy both processes, gelation and phase separation, spontaneously occur in system containing the presence of the phase separation inducer. The different aluminas were produced by using as aluminum reactants, aluminum isopropoxide and chloride and polyethylene oxide or polypropylene oxide as phase separation inducer. Appropriate choice of the starting composition allows the control the pore size and volume. Macroporous are formed as a result of phase separation after burning the phase separation inducer, while voids between particles of the xerogel skeletons form a mesoporous structures. The different alumina porous alumina and commercial alumina were used as supports for preparing by wetness impregnation cobalt-based catalyst. The oxidic catalyst precursors obtained after calcination are composed of Co3O4 and CoAl2O4-like phases, the latter being in higher proportions in the sol-gel alumina than in the commercial one. As the sol-gel alumina presents a larger amount of octahedral AlVI sites and surface hydroxyl groups than the commercial alumina, it was assumed that these features can facilitate the migration of Co ions into the alumina network...
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Passos, Aline Ribeiro. "Aluminas macro-mesoporosas produzidas pelo método sol-gel para aplicação em catálise heterogênea /." Araraquara, 2015. http://hdl.handle.net/11449/136086.
Full textAbstract:
Orientador: Celso Valentim SantilliOrientador: Valérie Briois
Co-orientador: Leandro Martins
Banca: Pedro de Oliveira
Banca: Sylvain Cristol
Banca: Victor Luis dos Santos Teixeira da Silva
Banca: Douglas Gouvêa
Resumo: Alumina é um suporte importante em catálise heterogênea. O controle das propriedades física e texturais pode melhorar seu desempenho como suporte em aplicações de catálise. Os catalisadores de cobalto são conhecidos por apresentarem excelente performance na reação de reforma de etanol (ESR) devido a elevada capacidade de quebra das ligações C-H e C-C. Muitos estudos visam correlacionar as propriedades das aluminas com o desempenho dos catalisadores. As aluminas exibem uma química de superfície complexa que pode ser controlada pelo método de preparação. Neste trabalho aluminas com meso e macroporos foram obtidas usando o método sol-gel acompanhado de separação de fases. Nesta estratégia integrativa a gelatinização e a separação de fases ocorrem de maneira espontânea no sistema contendo um indutor de separação de fases. Diferentes alumina foram produzidas a partir do isopropóxido e cloreto de alumínio e do óxido de polietileno e óxido de polipropileno como indutores de separação de fases. A escolha apropriada da composição de partida permite o controle do tamanho e volume dos poros. Os macroporos são formados como resultado da separação de fases após remoção do indutor de separação de fases, enquanto os mesoporos são formados entre as partículas do xerogel. As diferentes aluminas porosas preparadas e uma alumina comercial foram utilizadas como suporte de catalisadores de cobalto. Os precursores óxidos dos catalisadores obtidos após calcinação são compostos pelas fases Co3O4 e CoAl2O4, esta última em maior quantidade nas aluminas sintetizadas via sol-gel. As aluminas sol-gel possuem maior proporção de Al em sítios octaédricos e grupos hidroxilas superficiais do que a alumina comercial, verificou-se que estas características podem facilitar a migração de íons de Co na rede da alumina levando a maior formação de CoAl2O4. Os catalisadores foram...
Abstract: Alumina is an important support for heterogeneous catalysts. The matching of appropriate alumina physical properties and controlled textural properties can improve its performance as support in catalysis applications. Cobalt based catalysts have been reported to have a good ethanol steam reforming (ESR) performance due to their high activity for the cleavage of C-H and C-C bonds. Many studies have been conducted about the effects of alumina properties on the cobalt catalysts properties. Alumina exhibits a rather complex surface chemistry which can be controlled by the preparation procedure. In this work alumina samples with macro and mesoporous structure were obtained using the one-pot sol-gel synthesis accompanied by phase separation. In this integrative strategy both processes, gelation and phase separation, spontaneously occur in system containing the presence of the phase separation inducer. The different aluminas were produced by using as aluminum reactants, aluminum isopropoxide and chloride and polyethylene oxide or polypropylene oxide as phase separation inducer. Appropriate choice of the starting composition allows the control the pore size and volume. Macroporous are formed as a result of phase separation after burning the phase separation inducer, while voids between particles of the xerogel skeletons form a mesoporous structures. The different alumina porous alumina and commercial alumina were used as supports for preparing by wetness impregnation cobalt-based catalyst. The oxidic catalyst precursors obtained after calcination are composed of Co3O4 and CoAl2O4-like phases, the latter being in higher proportions in the sol-gel alumina than in the commercial one. As the sol-gel alumina presents a larger amount of octahedral AlVI sites and surface hydroxyl groups than the commercial alumina, it was assumed that these features can facilitate the migration of Co ions into the alumina network...
Doutor
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Su, Zixue. "Porous anodic metal oxides." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/1019.
Full textAbstract:
An equifield strength model has been established to elucidate the formation mechanism for the highly ordered alumina pore arrays and titanium oxide nanotubular arrays prepared via a common electrochemical methodology, anodisation. The fundamentals of the equifield strength model was the equilibrium between the electric field driven oxidation rate of the metal and electric field enhanced dissolution rate of oxide. During the anodic oxidation of metal, pore initiation was believed to generate based on dissolution rate difference caused by inhomogeneity near the metal/oxide interface. The ionic nanoconvection driven by the electric force exerted on the space charge layer in the vicinity of electrolyte/oxide interface is established to be the main driving force of the pore ordering at the early stage of the anodisation. While the equifield strength requirement governs the following formation of the single pore and the self-ordering of random distributed pore arrays during the anodisation process. Hexagonal patterned Al2O3 nanopore arrays and TiO2 nanotubular arrays have been achieved by anodisation of corresponding metal substrates in proper electrolytes. The two characteristic microstructural features of anodic aluminium oxide (AAO) and anodic titanium oxide (ATO) were investigated using scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The observations of the hemispherical electrolyte/oxide and oxide/metal interfaces, uniform thickness of the oxide layer, as well as self-adjustment of the pore size and pore ordering can be well explained by the equifield strength model. Field enhanced dissociation of water is extremely important in determination of the porosity of anodic metal oxide. The porosity of AAO and ATO films was found to be governed by the relative dissociation rate of water which is dependent on anodisation conditions, such as electrolyte, applied voltage, current density and electric field strength. Using an empirical method, the relations between the porosity of the AAO (ATO) films and the anodisation parameters, such as electric field strength, current density and applied voltage, have been established. Besides, the extent that an external electric field can facilitate the heterolytic dissociation of water molecule has been estimated using quantum-chemical model computations combined with the experimental aspect. With these achievements, the fabrication of anodic metal oxide films can be understood and controlled more precisely. Additionally, the impacts of other factors such as the electrolyte type and the temperature effect on the morphology of the anodic products were also investigated. Some important experimental evidences on the pore diameters variation with applied voltage in the anodisation of aluminium and the titanium were obtained for future investigation of the anodic metal oxide formation processes.
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Yigit, Mehmet Veysel. "Design of open hydrogen-bonded frameworks using bis(imidazolium 2,4,6-pyridinetricarboxylate)metal complexes as secondary building units." Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0514103-110657.
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Karlsson, Linda. "Biomolecular interactions with porous silicon /." Linköping : Univ, 2003. http://www.bibl.liu.se/liupubl/disp/disp2003/tek804s.pdf.
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Sommer, Jared Lee 1960. "Infiltration of deformable porous media." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/13101.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1992.Vita.
Includes bibliographical references (leaves 179-188).
by Jared Lee Sommer.
Ph.D.
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Lin, Bingcan. "A new FEA modelling of porous solids." Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=59600.
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Byun, Caroline. "Bio-inspired photonic and plasmonic thermo-optical porous materials." Electronic Thesis or Diss., Sorbonne université, 2022. http://www.theses.fr/2022SORUS448.
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Cette thèse s’inscrit dans la volonté de développer des matériaux autonomes, dotés de capacité à auto réguler la température et l'aspect optique en imitant l'homéostasie des systèmes vivants. Nous explorons différentes stratégies « bottom-up » pour induire l'autorégulation en intégrant des cycles de rétroaction négative dans les nanomatériaux. Pour réaliser, nous exploitons les propriétés thermo-optiques des matériaux nanoporeux (Sol-gel, MOFs) en présence d'une phase vapeur et associé à des structures photoniques et/ou plasmoniques à différentes échelles. Deux approches de synthèses sont proposées : 1) les particules core-shell, microsphères plasmoniques 2) des couches mince hybrides thermo-optiques sous forme de cristal photonique 1D La fabrication de ces objets nécessite l'utilisation d’une large gamme de méthodes et de procédés synthétiques, notamment la synthèse de solutions, la chimie sol-gel, le dépôt liquide, l’aérosol. En outre, les matériaux sont caractérisés par la microscopie électronique (TEM, SEM-FEG), l'ellipsométrie environnementale et par une microscopie hyper spectrale environnementale permettant la caractérisation optique d'objets individuels. Une dernière partie du projet, plus exploratoire, est consacrée à l'étude des écailles de certains scarabées qui présentent des comportements optiques similaires à ceux de nos surfaces synthétiquesThis thesis aims to develop autonomous materials with the ability to self-regulate temperature and optical appearance by mimicking the homeostasis of living systems. We are exploring different bottom-up strategies to induce self-regulation by integrating negative feedback cycles into nanomaterials. To achieve this, we exploit the thermo-optical properties of nanoporous materials (Sol-gel, MOFs) in the presence of a vapour phase and associated with photonic and/or plasmonic structures at different scales. Two synthesis approaches are proposed: 1) core-shell particles, plasmonic microspheres 2) hybrid thermo-optical thin films in the form of 1D photonic crystals The fabrication of these objects requires the use of a wide range of synthetic methods and processes, including solution synthesis, sol-gel chemistry, liquid deposition, aerosolisation. In addition, the materials are characterised by electron microscopy (TEM, SEM-FEG), environmental ellipsometry and environmental hyperspectral microscopy for optical characterisation of individual objects. The last part of the project, which is more exploratory, is devoted to the study of the scales of certain beetles, which exhibit optical behaviours similar to those of our synthetic surfaces
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Rumplecker, Anja. "Host guest chemistry of mesoscopically ordered porous materials." [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=984866566.
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Guastavino, Rémi. "Elastic and acoustic characterisation of anisotropic porous materials." Doctoral thesis, KTH, MWL Marcus Wallenberg Laboratoriet, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4782.
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For an accurate prediction of the low and medium frequency surface vibration and sound radiation behaviour of porous materials, there is a need to improve the means of estimating their elastic and acoustic properties. The underlying reasons for this are many and of varying origin, one prominent being a poor knowledge of the geometric anisotropy of the cell microstructure in the manufactured porous materials. Another one being, the characteristic feature of such materials i.e. that their density, elasticity and dissipative properties are highly dependent upon the manufacturing process techniques and settings used. In the case of free form moulding, the geometry of the cells and the dimensions of the struts are influenced by the rise and injection flow directions and also by the effect of gravity, elongating the cells. In addition the influence of the boundaries of the mould also introduces variations in the properties of the foam block produced. Despite these complications, the need to predict and, in the end, optimise the acoustic performance of these materials, either as isolated components or as part of a multi-layer arrangement, is growing. It is driven by the increasing demands for an acoustic performance in balance with the costs, a focus which serves to increase the need for modelling their behaviour in general and the above mentioned, inherent, anisotropy in particular. The current work is focussing on the experimental part of the characterisation of the material properties which is needed in order to correctly represent the anisotropy in numerical simulation models. Then an hybrid approach based on a combination of experimental deformation, strain field mapping, flow resistivity measurement and physically based porous material acoustic Finite Element (FE) simulation modelling is described. This inverse estimation linked with high quality measurements is crucial for the determination of the anisotropic coefficients of the porous materials is illustrated here for soft foam and fibrous wool materials.QC 20100729
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Hussami, Linda. "Synthesis, Characterization and Application of Multiscale Porous Materials." Doctoral thesis, KTH, Oorganisk kemi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-27158.
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This thesis work brings fresh insights and improved understanding of nanoscale materials through introducing new hybrid composites, 2D hexagonal in MCM-41 and 3D random interconnected structures of different materials, and application relevance for developing fields of science, such as fuel cells and solar cells.New types of porous materials and organometallic crystals have been prepared and characterized in detail. The porous materials have been used in several studies: as hosts to encapsulate metal-organic complexes; as catalyst supports and electrode materials in devices for alternative energy production. The utility of the new porous materials arises from their unique structural and surface chemical characteristics as demonstrated here using various experimental and theoretical approaches.New single crystal structures and arene-ligand exchange properties of f-block elements coordinated to ligand arene and halogallates are described in Paper I. These compounds have been incorporated into ordered 2D-hexagonal MCM-41 and polyhedral silica nanofoam (PNF-SiO2) matrices without significant change to the original porous architectures as described in Paper II and III. The resulting inorganic/organic hybrids exhibited enhanced luminescence activity relative to the pure crystalline complexes.A series of novel polyhedral carbon nanofoams (PNF-C´s) and inverse foams were prepared by nanocasting from PNF-SiO2’s. These are discussed in Paper IV. The synthesis conditions of PNF-C’s were systematically varied as a function of the filling ratio of carbon precursor and their structures compared using various characterization methods. The carbonaceous porous materials were further tested in Paper V and VI as possible catalysts and catalyst supports in counter- and working electrodes for solar- and fuel cell applications.QC 20101207
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Chapman, David James. "Shock-compression of porous materials and diagnostic development." Thesis, University of Cambridge, 2010. https://www.repository.cam.ac.uk/handle/1810/252180.
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A robust experimental design for measuring the shock-response of granular materials at ambient and higher densities is described. The method employed Lagrangian sensors embedded in anvils surrounding a sample cavity. The shock-consolidation of silica powders with a range of initial densities, structural forms of silica, morphologies, and water-content were investigated. Data on the principal Hugoniot and off-Hugoniot states were measured for: fused-silica powders of initial density ρ00 = 0.1, 0.25, and 0.77 g cm-3, quartz-sand of varying water-content (0%, 10%,20%, and 22% by mass), and statically compacted soil with initial density ρ00 = 2.29 g cm-3. The presence of a high water-content (20% and 22%) between the sand grains significantly altered the shock-response of the material. For most materials a dramatic stiffening in the material behaviour was observed upon reshock, an observation consistent with data from the literature. A phenomenological description of the compaction process in terms of grain re-arrangement, particle fracture, and plastic flow is offered. The P-α compaction model in various functional forms is applied to the fused-silica data. The exponential and power-law descriptions are observed to best fit the experimental results. The state of the art of measuring lateral stress using manganin gauges is reviewed, particularly in light of recent published results from hydrocode simulations. A series of recommendations for how best to use manganin gauges to measure lateral stress is presented. These suggestions result in small modifications to current analysis techniques. An experimental investigation of the behaviour of T-gauges, a manganin gauge commonly used to measure lateral stress, is presented. It is conclusively demonstrated that T-gauges behave approximately as wire gauges in the longitudinal orientation, and not as grid gauges as previously believed.
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Guastavino, Rémi. "Elastic and acoustic characterisation of anisotropic porous materials /." Stockholm : Department of Aeronautical and Vehicle Engineering, Royal Institute of Technology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4782.
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