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Zhang, Jin. "Shakedown of porous materials". Thesis, Lille 1, 2018. http://www.theses.fr/2018LIL1I044/document.
Pełny tekst źródłaThis 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
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.
Pełny tekst źródłaNEGRONI, MATTIA. "Dynamics in Porous Materials". Doctoral thesis, Università degli Studi di Milano-Bicocca, 2020. http://hdl.handle.net/10281/263115.
Pełny tekst źródłaMy 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.
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.
Pełny tekst źródłaTchang, Cervin Nicholas. "Porous Materials from Cellulose Nanofibrils". Doctoral thesis, KTH, Fiberteknologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-155065.
Pełny tekst źródłaQC 20141103
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.
Pełny tekst źródłaHarter, 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.
Pełny tekst źródłaJacobs, Tia. "Self-assembly of new porous materials". Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/3970.
Pełny tekst źródłaENGLISH 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.
Alsayednoor, Jafar. "Modelling and characterisation of porous materials". Thesis, University of Glasgow, 2013. http://theses.gla.ac.uk/4808/.
Pełny tekst źródłaThompson, Benjamin Robert. "Hierarchically structured composites and porous materials". Thesis, University of Hull, 2017. http://hydra.hull.ac.uk/resources/hull:16570.
Pełny tekst źródłaHaubensak, Frederick G. (Frederick George). "Microstructure design of porous brittle materials". Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/26876.
Pełny tekst źródłaIncludes bibliographical references (leaves 214-223).
by Frederick George Haubensak.
Ph.D.
McMonagle, Charles James. "Effect of pressure on porous materials". Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31504.
Pełny tekst źródłaEder, Grace M. "Dye Molecule-Based Porous Organic Materials". The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1530012900215452.
Pełny tekst źródłaFarghaly, Ahmed A. "Fabrication of Multifunctional Nanostructured Porous Materials". VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4189.
Pełny tekst źródłaRichards, Emma. "Immobilisation of polyazamacrocycles into porous materials". Thesis, University of Liverpool, 2012. http://livrepository.liverpool.ac.uk/8513/.
Pełny tekst źródłaAcartürk, Ayhan. "Simulation of charged hydrated porous materials". Essen VGE, 2009. http://d-nb.info/998591939/04.
Pełny tekst źródłaCooper, Emma. "Renewable routes to porous aluminosilicate materials". Thesis, University of York, 2012. http://etheses.whiterose.ac.uk/3936/.
Pełny tekst źródłaLopes, Felipe Robles. "Estudos experimentais de danos de formação em meios porosos". [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265225.
Pełny tekst źródłaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica e Instituto de Geociências
Made available in DSpace on 2018-08-22T09:00:58Z (GMT). No. of bitstreams: 1 Lopes_FelipeRobles_M.pdf: 3706160 bytes, checksum: 5656fb6101eaefe1ce42e6acd4bcca9d (MD5) Previous issue date: 2013
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
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.
Pełny tekst źródłaCommittee Chair: Dr. Mulalo Doyoyo; Committee Member: Dr. Arash Yavari; Committee Member: Dr. Kenneth M. Will. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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.
Pełny tekst źródłaKou, Shuting, i 寇舒婷. "Porous structure modeling with computers". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206700.
Pełny tekst źródłapublished_or_final_version
Mechanical Engineering
Master
Master of Philosophy
Chow, Hon-nin, i 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.
Pełny tekst źródłaLizardi-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.
Pełny tekst źródłaRidgway, Catherine Jean. "Modelling pore-level properties of porous materials". Thesis, University of Plymouth, 1995. http://hdl.handle.net/10026.1/1707.
Pełny tekst źródłaWilcox, O. T. "Porous materials for the uptake of ammonia". Thesis, University of Liverpool, 2017. http://livrepository.liverpool.ac.uk/3007235/.
Pełny tekst źródłaMohamed, Rozita. "Preparation of nano-structured macro-porous materials". Thesis, University of Newcastle upon Tyne, 2011. http://hdl.handle.net/10443/1317.
Pełny tekst źródłaLittlefield, Benjamin T. R. "Solvothermal synthesis of porous beryllate containing materials". Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/359297/.
Pełny tekst źródłaPanella, Barbara. "Hydrogen storage by physisorption on porous materials". [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-29012.
Pełny tekst źródłaYan, Xuecheng. "Carbon-based Porous Materials for Electrochemical Reactions". Thesis, Griffith University, 2016. http://hdl.handle.net/10072/366852.
Pełny tekst źródłaSchool of Natural Sciences
Science, Environment, Engineering and Technology
Full Text
Kunjir, Shrikant. "Study of new porous materials by NMR". Thesis, Normandie, 2018. http://www.theses.fr/2018NORMC211/document.
Pełny tekst źródłaThe 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)
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.
Pełny tekst źródłaQC 20121107
Mochizuki, Shuto. "Controlled radical polymerization in designed porous materials". Kyoto University, 2019. http://hdl.handle.net/2433/242535.
Pełny tekst źródłaLutzweiler, Gaëtan. "Porous polyurethane-based materials for tissue engineering". Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAE019/document.
Pełny tekst źródłaPorous 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
TANZI, MARLOTTI GIACOMO. "THEORY OF POSITRONIUM INTERACTIONS WITH POROUS MATERIALS". Doctoral thesis, Università degli Studi di Milano, 2018. http://hdl.handle.net/2434/609709.
Pełny tekst źródłaCrimm, 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/.
Pełny tekst źródłaQiao, Chongzhi. "Theoretical study of fluid adsorption in porous materials". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEN051/document.
Pełny tekst źródłaPorous 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
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.
Pełny tekst źródłaPassos, 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.
Pełny tekst źródłaAlumina 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...
Passos, Aline Ribeiro. "Aluminas macro-mesoporosas produzidas pelo método sol-gel para aplicação em catálise heterogênea /". Araraquara, 2015. http://hdl.handle.net/11449/136086.
Pełny tekst źródłaOrientador: 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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Pełny tekst źródłaVita.
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by Jared Lee Sommer.
Ph.D.
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Pełny tekst źródłaThis 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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