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1
Ritchie, Robert B. "Chemical routes to atomic nitrogen." Thesis, University of Aberdeen, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359346.
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Chapter 1 contains a general introduction and review of the field of atomic nitrogen chemistry. Included here is mention of the occurrences, generation, detection and analysis, reactions and uses of atomic nitrogen. A summary of previous work towards the chemical generation of atomic nitrogen in solution is given, this being stated as the overall aim of the thesis. This aim encompasses bond-breaking: (a) in nitrogen containing heterocycles upon mild photolysis or thermolysis, (b) in azidyl radicals. Chapter 2 describes the benzocinnoline N-imine system along with its isomeric 5H-dibenzo[1,2,3][d,f]triazepine with a view to the selective derivatisation of the latter. The photochemical and oxidative reactions of these systems are investigated by esr. 1H-Benzotriazole and selected derivatives are examined as triazenyl models for the triazepinyl system. Chapter 3 considers the chemistry of the 1,3,4-dioxazol-2-ones particularly the unreported 5-O-linked derivatives which are sought as possible precursors to the novel 1,3,4-dioxazolidine-2,5-diones themselves potential atomic nitrogen precursors. Chapter 4 concerns the 1,2,4-dithiazolidine-3,5-diones as potential atomic nitrogen precursors and two routes are pursued to the little reported unsubstituted parent 1,2,4-dithiazolidinedione. Chapter 5 departs from the heterocyclic theme of chapters 2-4 and considers the generation and fragmentation of the azidyl radical as a possible source of atomic nitrogen. Evidence for the production of atomic nitrogen from this radical, generated from the persulphate oxidation of azide anion, is discussed.
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Lawrence, Duncan. "Quantifying inherent safety of chemical process routes." Thesis, Loughborough University, 1996. https://dspace.lboro.ac.uk/2134/7427.
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Inherent safety is that which is intrinsic to a chemical plant. Chemical plants should be designed to be acceptably safe and it is better if this can be achieved through inherent safety, which can not be compromised, rather than engineered safety. The earlier that inherent safety is considered, the greater are the benefits. The choice of chemical route, that is the raw materials and the sequence of reactions that converts them to the desired products, is a key early design decision that influences the inherent safety of a plant. The inherent safety must be quantified in order to choose the optimum route from a number of alternatives. A trial inherent safety index has been developed for ranking alternative chemical routes by inherent safety. The physical properties of the chemicals involved, and the conditions in the reaction steps are parameters in the index calculation procedure. The index has been tested on a number of routes to methyl methacrylate (MMA). In order to verify and improve the index, a panel of experts was asked to rank the routes, and to make comments about the index and how it could be improved. This expert judgement exercise used three questionnaires and a group meeting to elicit the required information. Statistical methods were used to analyse the results from the questionnaires. The experts agreed closely among themselves on the rankings. The rankings from the trial index and the rankings from the experts matched closely. A new index was produced based on the comments of the experts and further research. The new index is more structured than the trial index, and separation and storage steps are included in addition to reaction steps. The inherent safety of the routes to MMA has been assessed with the new index. Developing a method for quantifying the inherent safety of chemical routes has proved to be a large and difficult task. Further research is needed to decide how the interactions between parameters affect the assessment of inherent safety. The ultimate goal is a computerised tool that could be used in the early stages of industrial process development.
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Tangeysh, Behzad. "SIZE-CONTROLLED SYNTHESIS OF TRANSITION METAL NANOPARTICLES THROUGH CHEMICAL AND PHOTO-CHEMICAL ROUTES." Diss., Temple University Libraries, 2015. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/327946.
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ChemistryPh.D.
The central objective of this work is developing convenient general procedures for controlling the formation and stabilization of nanoscale transition metal particles. Contemporary interest in developing alternative synthetic approaches for producing nanoparticles arises in large part from expanding applications of the nanomaterials in areas such as catalysis, electronics and medicine. This research focuses on advancing the existing nanoparticle synthetic routes by using a new class of polymer colloid materials as a chemical approach, and the laser irradiation of metal salt solution as a photo-chemical method to attain size and shape selectivity. Controlled synthesis of small metal nanoparticles with sizes ranging from 1 to 5nm is still a continuing challenge in nanomaterial synthesis. This research utilizes a new class of polymer colloid materials as nano-reactors and protective agents for controlling the formation of small transition metal nanoparticles. The polymer colloid particles were formed from cross-linking of dinegatively charged metal precursors with partially protonated poly dimethylaminoethylmethacrylate (PDMAEMA). Incorporation of [PtCl6]2- species into the colloidal particles prior to the chemical reduction was effectively employed as a new strategy for synthesis of unusually small platinum nanoparticles with narrow size distributions (1.12 ± 0.25nm). To explore the generality of this approach, in a series of proof-of-concept studies, this method was successfully employed for the synthesis of small palladium (1.4 ±0.2nm) and copper nanoparticles (1.5 ±0.6nm). The polymer colloid materials developed in this research are pH responsive, and are designed to self-assemble and/or disassemble by varying the levels of protonation of the polymer chains. This unique feature was used to tune the size of palladium nanoparticles in a small range from 1nm to 5nm. The procedure presented in this work is a new convenient room temperature route for synthesis of small nanoparticles, and its application can be extended to the formation of other transition metals and alloy nanoparticles. This research also focuses on developing new photo-chemical routes for controlling the size and shape of the nanoparticles through high-intensity ultra-fast laser irradiation of metal salt solution. One of the core objectives of this work is to explore the special capabilities of shaped laser pulses in formation of metal nanoparticles through irradiation of the solutions by using simultaneous spatial and temporal focusing (SSTF). Femtosecond laser irradiation has not yet been widely applied for nanoparticle synthesis, and offers new regimes of energy deposition for synthesis of nanomaterials. Photo-reduction of aqueous [AuCl4]- solution to the gold nanoparticles (AuNPs) has been applied as a model process for optimizing the experimental procedures, and evaluating the potential of shaped laser pulses in the synthesis of AuNPs. Systematic manipulation of the laser parameters and experimental conditions provided effective strategies to control the size of Au nanoparticles in strong laser fields. Varying the concentration of polyethylene glycol (PEG45) as a surfactant effectively tuned the size of AuNPs from 3.9 ±0.7nm to 11.0 ±2.4nm, and significantly increased the rate of Au(III) reduction during irradiation. Comparative studies revealed the capability of shaped laser pulses in the generation of smaller and more uniform AuNPs (5.8 ±1.1nm) relative to the other conventional laser irradiation methods (7.2 ±2.9nm). Furthermore, a new laser-assisted approach has been developed for selective formation of triangular Au nanoplates in the absence of any surfactant molecule. This method relies on rapid energy deposition by using shaped, ultra-intense laser pulses to generate Au seeds in aqueous [AuCl4]- solution, and the slow post-irradiation reduction of un-reacted [AuCl4]- species by using H2O2 as a mild reducing agent. Variation of the laser irradiation-time was found as an effective strategy to tune the morphology of Au nanomaterials from nanospheres to triangular nanoplates. The surfactant-free Au nanoplates produced in this research can be readily functionalized with a variety of target molecules or surfactants for desirable applications such as biomedicine. The concept of rapid laser processing followed by in situ chemical reduction can be expanded as a general methodology for high-yield production of nanomaterials, and provides a series of new laser dependent parameters for controlling the nanoparticle formation.
Temple University--Theses
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Grimsdale, Andrew Clive. "Routes to drimanes from podocarpic acid." Thesis, University of Auckland, 1989. http://hdl.handle.net/2292/2072.
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The synthesis and ozonolysis of the 6- and 7-substituted 12-hydroxypodocarpatrienes (26), (86), (90), and (98), as a possible route for the synthesis of drimanes from 12-hydroxypodocarpa-8,11,13-trien-19-oic acid (podocarpic acid) (9) has been investigated. Modification of the aromatic ring of (9) has given 11- and l4-hydroxypodocarpatrienes which were ozonised to give the congeners (31), (34), and (36) of the naturally occurring drimanes confertifolin (6), isodrimenin (7), and winterin (8). The oxidation of a 12,13-dihydroxypodocarpatriene (37) and its dimethyl ether (38) have also been investigated. Routes for the conversion of the enone (45) and oxime (230), derived from the ozonolysis products of methyl podocarpate (10), to drimanes have also been investigated.
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Cayado, Llosa Pablo. "Multifunctional nanostructured superconductors by chemical routes: towards high current conductors." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/384856.
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Uno de los temas de mayor interés en el ámbito de la superconductividad es la fabricación de cintas superconductoras (CCs) de YBa2Cu3O6+δ (YBCO) debido a las excelentes propiedades superconductoras que poseen y a las prometedoras perspectivas en cuanto a aplicaciones se refiere. Sin embargo, para poder generalizar el uso de dichas CCs, se requiere de un proceso de fabricación de bajo coste. En este contexto, la técnica de deposición por solución química se presenta como una alternativa muy prometedora. Las CCs pueden cumplir los requisitos actuales exigidos en diferentes aplicaciones, pero hay otras que están fuera de sus capacidades, especialmente aquellas relacionadas con aplicaciones de potencia en las que están presentes campos magnéticos de gran intensidad. El movimiento de los vórtices que tienes lugar en presencia de tales campos magnéticos hace que el YBCO sea poco efectivo en estos casos. El objetivo de este trabajo es mejorar las propiedades del YBCO de manera que se puedan satisfacer los requerimientos de estas aplicaciones de potencia. Para ello, hemos estudiado, principalmente, dos estrategias: la nanoestructuración de la matriz del YBCO añadiendo nanopartículas (NPs) obteniendo nanocomposites superconductores y la optimización del proceso de oxigenación del YBCO para conseguir aumentar todo lo posible la temperatura crítica y la densidad de corriente crítica. La preparación de los nanocomposites de YBCO se llevó a cabo siguiendo dos métodos diferentes de “deposición y crecimiento secuencial”: el método “in-situ” en el que las NPs se forman de manera espontánea durante el proceso de crecimiento, y el método “ex-situ”, que es un novedoso procedimiento desarrollado durante esta tesis en el cual las NPs se sintetizan primeramente formando una solución coloidal para luego quedar atrapadas en la matriz del YBCO durante los procesos térmicos. El uso del método “in-situ” se ha enfocado al estudio de como diferentes NPs (BaZrO3, Y2O3, Ba2YTaO6 and mezclas de éstas) afectan la microestructura del YBCO creando defectos cristalinos que incrementan la fuerza de anclaje. Hemos estudiado también la influencia de estos defectos, en particular, de las dobles cadenas Cu-O, en las propiedades finales de los nanocomposites de YBCO y GdBCO. En el caso del método “ex-situ”, el primer paso fue sintetizar diferentes soluciones coloidales de NPs magnéticas (MnFe2O4 and CoFe2O4) y no magnéticas (CeO2 and ZrO2). Se comprobó la estabilidad de las soluciones YBCO+NPs mediante medidas de DLS y de TEM para asegurar que las NPs conservaban su tamaño inicial sin formar aglomerados. El proceso de pirólisis fue optimizado para cada tipo de NPs teniendo en cuenta que los ligandos usados para estabilizar las NPs pueden influenciar de manera drástica la homogeneidad de las capas pirolizadas. Por último, el proceso de crecimiento fue también investigado para cada tipo de NPs. El estudio del proceso de oxigenación en la capas de YBCO se llevó a cabo usando medidas de resistencia “in-situ”, que permiten monitorizar la evolución de la resistencia en las capas durante los distintos procesos térmicos. Hemos estudiado como la temperatura, el flujo de gas y la presión parcial de oxigeno afectaba al proceso de difusión. De acuerdo con nuestros resultados, las reacciones que tienen lugar en la superficie de la capa antes de que en oxígeno se difunda en el interior de la misma, son el factor que limita la cinética del proceso de oxigenación. Por último El efecto de la adición de plata como catalizador y la difusión en nanocomposites también se ha estudiado.One of the hot topics in the field of superconductivity is the YBa2Cu3O6+δ (YBCO) Coated Conductors (CCs) fabrication due to the excellent superconducting properties and promising application prospects. However, in order to spread worldwide the use of YBCO coated conductors, a low cost fabrication is required. Chemical Solution Deposition has emerged as a promising alternative that can accomplish this requirement. Despite that YBCO CCs can satisfy the requirements in many different applications, the fact is that there are other uses that are out of it reach with its current status, especially those power applications in which high magnetic fields are applied. The vortex movement which takes place at such high magnetic fields makes YBCO CCs useless for these particular applications. The aim of this work is to improve the properties of YBCO satisfying the demands of these power applications. For this, we studied, mainly, two different strategies: nanostructuration of the original YBCO matrix by adding NPs (superconducting nanocomposites) and optimization of the YBCO oxygenation process to enhance as much as possible the critical temperature and critical current density. The preparation of YBCO nanocomposites was done following two different “Sequential deposition and growth” approaches: the in-situ approach in which the NPs are spontaneously segregated during the growth process; and the ex-situ approach, a new methodology developed in this thesis in which the NPs are firstly synthesized in a colloidal solution and then embedded in the YBCO matrix. Using the in-situ approach we have made an extensive study of how different NPs (BaZrO3, Y2O3, Ba2YTaO6 and mixtures of these) affect the microstructure of the YBCO creating defects that increase the pinning properties. We have also studied the influence of these defects, in particular, the stacking faults (double chains of Cu-O), on the final properties of the YBCO and GdBCO nanocomposites. With the ex-situ approach we have started by synthesizing different colloidal solutions of both magnetic (CoFe2O4) and non-magnetic (CeO2 and ZrO2) NPs. The stability of YBCO+NPs solutions was checked using TEM and DLS analyses to ensure that the NPs are maintaining the initial size without forming agglomerates. The pyrolysis process was optimized for each type of NPs. We realized that the stabilization agents can critically influence the homogeneity of the pyrolyzed films. Finally, the growth process was also optimized for each type of NPs trying to solve different difficulties that appeared: coarsening, pushing or reactivity. The study of the oxygen diffusion process in YBCO thin films was done using in-situ resistivity measurements that allow to monitor the evolution of the resistance in the thin films in different annealing conditions. We have studied how the temperature, the gas flow and the oxygen partial pressure affect the diffusion process. According to our results, we can conclude that the surface reactions that take place before the oxygen bulk diffusion is the limiting factor for the oxygen diffusion. The effect of the silver addition to the YBCO as oxygen catalyst was also tested. Finally, the first study about the oxygen diffusion process in nanocomposite films gave an idea of how the oxygen diffusion works in this kind of materials.
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Bond, Stuary Grahame. "Routes to reactive oligomers involving photochemical and chemical cleavage of copolymers." Thesis, Lancaster University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315936.
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Wernet, Judith Hedwig. "Composite and microcomposite fabrication via depletion stabilization routes." Case Western Reserve University School of Graduate Studies / OhioLINK, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=case1061910390.
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Green, Mark A. "Novel routes to nanodispersed semiconductors." Thesis, Imperial College London, 1999. http://hdl.handle.net/10044/1/12035.
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Karlsson, Johan. "Theoretical Routes for c-BN Thin Film Growth." Doctoral thesis, Uppsala universitet, Oorganisk kemi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-191181.
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c-BN has been in focus for several years due to its interesting properties. The possibility for large area CVD is a requirement for the realization of these different properties in various applications. Unfortunately, there are at present severe problems in the CVD growth of c-BN. The purpose with this research project has been to theoretically investigate, using DFT calculations, the possibility for a layer-by-layer CVD growth of c-BN. It could be established that, PEALD, using a BF3-H2-NH3-F2 pulse cycle and a diamond substrate, is a promising method for deposition of c-BN films. The gaseous species will decompose in the plasma and form BFx, H, NHx, and F species (x = 0, 1, 2, 3). The H and F radicals will uphold the cubic structure by completely hydrogenate, or fluorinate, the growing surface. However, surface radical sites will appear during the growth process as a result of atomic H, or F, abstraction reactions. The addition of NHx growth species (x = 0, 1, 2) to B radical sites, and BFx growth species (x = 0, 1, 2) to N radical sites, will then result in a continuous growth of c-BN.
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Sandberg, Birgersson Paulina. "Transparent paper: Evaluation of chemical modification routes to achieve self-fibrillating fibres." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-281347.
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Transparenta papper tillverkade av cellulosa nanofibriller (CNF), visar stor potential att kunna ersätta petroleumbaserade plaster inom många användningsområden, till exempel för mat- och varuförpackningar. CNF, även känt som nanocellulosa, kombinerar viktiga cellulosaegenskaper, med unika egenskaper hos nanomaterial. Denna kombination av egenskaper möjliggör tillverkning av ett pappers-liknande material som uppvisar både utmärkta mekaniska egenskaper och hög transparens. Användningen av nanocellulosa är dock förknippad med diverse utmaningar, för att materialet ska kunna bli kommersiellt slagkraftigt. En av de främsta utmaningarna är nanocellulosas höga affinitet för vatten och dess höga specifika yta som försvårar hanteringen av materialet. Avvattningen av nanocellulosadispersioner, för att tillverka transparenta papper, kan ta upp till flera timmar. För att övervinna detta hinder, har avdelningen för Fiberteknologi vid KTH tillsammans med BillerudKorsnäs AB, nyligen utvecklat en metodik för att skapa så kallade själv-fibrillerande fibrer (SFFer). Dessa fibrer möjliggör en snabbavvattnad papperstillverkningsprocess med makroskopiska vedbaserade fibrer, som efter tillverkning av pappret omvandlas till ett nanocellulosapapper, det vill säga ett nanopapper. För att erhålla SFFer krävs det att höga koncentrationer av karboxyl- och aldehydgrupper introduceras i cellulosafibrerna. Införandet av dessa funktionella grupper, möjliggör självfibrilleringen då SFFerna utsätts för moderata alkali-koncentrationer. I den ursprungliga studien som utfördes av Gorur m.fl., introducerades de funktionella grupperna med hjälp av sekventiell TEMPO- och periodatoxidation. I detta examensarbete, har alternativa kemiska metoder för att introducera samma kemiska funktionalitet som TEMPO-periodatsystemet undersökts. Huvudsyftet med arbetet är att besvara frågan: Hur påverkar olika kemiska behandlingar vid SFF tillverkningen, de kemiska och fysikaliska egenskaperna hos de modifierade fibrerna, samt de slutgiltiga pappersegenskaperna? För att besvara frågan, preparerades fibrer med liknande karboxyl- och aldehydinnehåll med hjälp av följande tre kemiska metoder: 1) TEMPO- följd av periodatoxidation (detta kommer att användas som referenssystem); 2) periodat- följd av kloritoxidation; 3) karboxymetylering följd av periodatoxidation. Egenskaperna hos fibrerna undersöktes med avseende på aldehyd- och karboxylinnehåll, avvattningspotential och förmåga att självfibrillera. Papper tillverkades med hjälp av en vakuumfiltreringsuppställning och följande egenskaper undersöktes hos pappret: mekaniska egenskaper (dragstyrka, brottsyrka och Young’s modul); optiska (transparens och ytreflektion); samt syrgaspermeabilitet. De erhållna fibrerna från samtliga tre kemiska modifieringar visade på självfibrillerande egenskaper i alkaliska lösningar. Detta beteende styrker hypotesen att ett strategiskt införande av ett högt karboxyl- och aldehydinnehåll leder till självfibrillerande fibrer. Transparenta papper tillverkade av fibrer som utsatts för TEMPO-periodatoxidation samt klorit-periodatoxidation, visade på utmärkta mekaniska egenskaper, hög transparens och bra barriäregenskaper - jämförbara med vad som vanligen kan noteras hos papper tillverkat av nanocellulosa. Samtliga egenskaper förbättrades ytterligare efter fibrillering av fibrerna i papperen. De karboxymetylerade-periodatoxiderade materialet, å andra sidan, uppvisade andra egenskaper jämfört med de två, tidigare nämnda, metoderna. TEMPO-periodat- och periodat-klorit-pappersmassan var halvgenomskinlig och geléliknande, medan den karboxymetylerade-periodatoxiderade massan var mer lik det omodifierade materialet. Detsamma gällde det tillverkade pappret som liknade ett konventionellt papper. Det var inte heller möjligt att åstadkomma en fibrillering av det karboxymetylerade-periodatoxiderade-pappret som utsattes för behandling med alkaliska lösningar. Avvattningstiden vid papperstillverkningen varierad mellan 4 och 60 sekunder, och karboxymetylering-periodat oxidation visade på snabbast avvattningstid. Den förlängda avvattningstiden i jämförelse med studien utförd av Gorur m.fl., tros främst bero på att ett filtreringsmembran med mindre porer användes på vakuumfiltreringsuppställningen, istället för en avvattningsvira som tidigare använts. Sammanfattningsvis så har det visat sig möjligt att tillverka självfibrillerande fibrer med hjälp av samtliga tre undersökta kemiska modifieringar. SFFer möjliggör tillverkning av snabbavvattnade transparenta nanocellulosapapper och visar på så vis på hög potential att kunna ersätta olje-baserade plaster till många förpackningsapplikationer.Transparent papers made from cellulose nanofibrils (CNF), derived from e.g. wood, show great potential to replace petroleum-based plastics in many application areas, such as packaging for foods and goods. CNF, also known as nanocellulose, combine important cellulose properties with the unique features of nanoscale materials, gaining paper-like materials with outstanding mechanical properties and high transparency. However, nanocellulose faces various challenges in order to make the products commercially competitive. One of the main challenges is accompanied with nanocelluloses’ high affinity for water, which makes processing difficult. Dewatering of a nanocellulose dispersion in order to produce transparent paper may take up to several hours. To overcome this obstacle, the Fibre technology division at KTH Royal Institute of technology and BillerudKorsnäs AB have recently developed a new concept of self-fibrillating fibres (SFFs). This material enables fast-dewatering papermaking using fibres of native dimensions and conversion into nanocellulose after the paper has been prepared. In order to obtain SFFs, proper amounts of charged groups and aldehyde groups need to be introduced into the cellulose backbone. When SFFs are exposed to high alkali concentration, i.e. > pH=10, the fibres self-fibrillates into CNFs. In the original study, the functional groups were introduced through sequential TEMPO oxidation and periodate oxidation. In this work, alternative chemical routes have been examined to prepare SFFs with the same functional groups as introduced with the TEMPO-periodate system. The aim of the thesis has been to answer: how does different chemical routes to prepare transparent nanopaper made from SFFs affect the chemical and physical properties of the modified fibres, as well as the final physical properties of the transparent papers? To answer the question, fibres with similar carboxyl and aldehyde contents were prepared using three chemical routes: 1) TEMPO oxidation followed by periodate oxidation (which was used as reference system); 2) periodate oxidation followed by chlorite oxidation; 3) carboxymethylation followed by periodate oxidation. The properties of the fibres were examined regarding aldehyde and carboxyl content, dewatering potential and self-fibrillating ability. Papers were produced using a vacuum filtration set-up and the properties investigated were the mechanical; tensile strength, strain at failure and Young’s modulus, the optical properties; transparency and haze, as well as the oxygen permeability. In order to investigate the impact of the fibrillation of the papers, the properties were measured for both unfibrillated and fibrillated samples. Furthermore, the gravimetric yield after each chemical modification procedure was examined, as well as the dewatering time during sheet making. Fibres obtained from all three chemistries demonstrated self-fibrillating properties in alkaline solutions. This strengthens the hypothesis that the strategical introduction of aldehydes and carboxyl groups is the main feature responsible for the self-fibrillating ability of the fibres. Transparent papers made from fibres treated through TEMPO-periodate oxidation and periodate-chlorite oxidation showed excellent mechanical, optical and barrier properties, comparable to those seen in nanocellulose papers. The properties were further increased after fibrillation. The carboxymethylated-periodate oxidized fibres, on the other hand, behaved differently from the others. While the TEMPO-periodate and periodate-chlorite pulp was semi-translucent and gel-like, the carboxymethylated-periodate oxidized fibres resembled more the unmodified material. Likewise, the properties of those papers resembled conventional paper and no fibrillationwas experienced after immersing the papers in alkaline solution, according to the same protocol developed for the other two chemistries. The dewatering time during sheet making ranged from 4–60 seconds (carboxymethylation-periodate oxidation showing the fastest dewatering rates). The increased dewatering time compared to earlier studies is believed to mainly be due to the use of a filtration membrane on the vacuum filtration set-up, instead of a metallic wire with larger pores. Overall, SFFs was successfully produced using three different chemical routes. SFFs enables production of fast-dewatering transparent nanocellulose papers that shows the potential to replace oil-based plastics in many packaging applications.
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Hajiani, Pouya. "New magnetic stimulation routes with magnetic nanoparticles from process intensification in chemical engineering." Thesis, Université Laval, 2013. http://www.theses.ulaval.ca/2013/29833/29833.pdf.
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Les nanoparticules magnétiques (NPM) suscitent un vif intérêt dans plusieurs branches de l’ingénierie et de la recherche. En effet, la taille de ces dernières ainsi que leur propriétés magnétiques lorsqu’en suspension permettent leur manipulation à distance en utilisant des champs magnétiques externes appropriés. Cela ouvre la voie à l’activation de fonctionnalités supplémentaires lorsqu’ancrées à des catalyseurs métalliques, des enzymes ou des agents thérapeutiques. Conséquemment, les NPM ont été impliquées au sein de plusieurs applications dans lesquelles le mélange à l’échelle microscopique est une problématique importante, par exemple dans les réactions catalytiques, la séparation et l’administration de médicaments.
Le présent travail de thèse explore l’utilisation de NPM en tant que dispositifs nanométriques pour manipuler le mélange à l’échelle microscopique lorsque le système complet est soumis à des champs magnétiques. Toutes les expérimentations ont été menées à l’intérieur d’un électro-aimant à bobines tubulaire statique possédant deux pôles et trois phases. Ce dernier génère des champs magnétiques rotatifs uniformes (CMR), des champs magnétiques oscillatoires (CMO) ainsi que des champs magnétiques stationnaires (CMS).
En premier lieu, une technique de mélange dans laquelle un CMR transforme des NPM en agitateurs nanométriques créant de petits tourbillons dans la phase liquide est présentée. L’utilisation de cette technique permet l’augmentation du coefficient de diffusion de l’eau quiescente dans une cellule de diffusion statique jusqu’à 200 fois. Les études systématiques des paramètres d’opération révèlent que l’ampleur de l’augmentation dépend de la fraction volumique en NPM ainsi que de la force et de la fréquence du champ magnétique.
En second lieu, un écoulement convectif est utilisé afin de comprendre l’effet du couple hydrodynamique sur le comportement des NPM en champs magnétiques. Des tests de distribution de temps de séjour par impulsion sont effectués avec et sans champ magnétique dans le but d’examiner la dispersion axiale d’un écoulement laminaire de Poiseuille à l’intérieur d’un tube capillaire (Tests de dispersion de Taylor). Les résultats obtenus démontrent que le mélange latéral au long du tube est favorisé en présence de NPM et d’un champ magnétique. De plus, l’effet hydrodynamique observé de ce mélange latéral sur le
profil de vitesse laminaire est interprété comme provenant d’une approche d’un profil de vitesse plat similaire à celui d’un écoulement piston. À l’aide de la même technique, l’effet des CMO et des CMS sur la dispersion de Taylor et sur le profil de vitesse laminaire est aussi examiné en écoulement capillaire. Alors que les CMO n’induisent pas de mélange nano-convectif dans le capillaire et ont un impact négligeable sur la dispersion axiale, les CMS pour leur part, détériorent le mélange latéral du traceur et créent des profils de vitesse déviant de la forme parabolique vers une forme plus saillie. Une discussion détaillée de la vorticité du fluide en fonction de l’orientation du champ magnétique est aussi présentée.
Finalement, un écoulement multiphasique est étudié en ciblant le transfert de matière gaz-liquide entre des bulles de Taylor d’oxygène et la phase liquide, composée d’une solution diluée de NPM, à l’intérieur de tubes capillaires soumis à des CMR, des CMO et des CMS. Les résultats indiquent que les NPM qui tournent sous l’action d’un CMR améliorent le mélange dans le film lubrificateur qui entoure les bulles de Taylor comme cela est révélé par une augmentation mesurable du kLa. À l’opposé, les CMS immobilisent les NPM, menant à des taux de transfert de matière systématiquement plus faibles alors que les CMO n’ont pas d’effet détectable sur le coefficient de transfert de matière. Par ailleurs, l’interaction entre le couple magnétique et le couple hydrodynamique nécessaire pour dominer la direction de rotation des NPM est tirée de ces résultats.Magnetic nanoparticles (MNPs) have attracted significant interest in diverse areas of engineering and research. Particle size and magnetic properties of suspended MNPs in a suspension allow their manipulation at a distance using appropriate external magnetic fields. In particular by enabling additional functionality in forms anchored to metal catalysts, enzymes or therapeutic drug agents. Owing to this feature, MNPs have been involved in many applications where mixing in micro-scale is also a critical issue, e.g., catalytic reaction, separation and drug delivery. This thesis explores MNPs as nano-scale devices to manipulate mixing in micro-scale when the whole system is subject to magnetic fields. All the experiments were performed in tubular two-pole, three-phase stator winding magnet, generating uniform rotating magnetic field (RMF), oscillating magnetic field (OMF) and stationary magnetic field (SMF). Initially, we present a mixing technique in which a RMF converts MNPs into nano-stirrers generating small vortices in liquid phase. Using this technique, self-diffusion coefficient of motionless water in a static diffusion cell was intensified up to 200 folds. Systematic studies of operating parameters revealed that the extent of enhancement depends on MNP volume fraction, and strength and frequency in magnetic field. In order to understand the effect of hydrodynamic torque on the MNPs behavior under magnetic fields, convective flow was also included. As such, axial dispersion of pressure-driven laminar Poiseuille flows in a capillary tube (Taylor dispersion test) was examined through a series of impulse (residence time distribution) RTD tests with and without RMF. This resulted in lateral mixing along the channel that was promoted relative to that in absence of MNPs or magnetic field. Moreover, we interpreted the observed hydrodynamic effects of such lateral mixing on laminar velocity profile as resulting from an approach to plug flow-like flat velocity profile. Using the same technique, the effect of OMF and SMF on Taylor dispersion and laminar velocity profile was examined in capillary flows. OMF did not induce nano-convective mixing in the capillary and had negligible impact on axial dispersion. On the contrary, SMF deteriorated lateral mixing of solute tracer and led to velocity profiles deviating from parabolic shape towards more protruded ones. A detailed discussion of magnetic field orientation versus fluid vorticity vector was presented. Finally a multiphase flow case concerned gas-liquid mass transfer from oxygen Taylor bubbles to the liquid in capillaries which was studied using dilute concentration of MNPs as the liquid phase under RMF, OMF and SMF. Experimental results implied that spinning MNPs under RMF improved mixing in the lubricating film that surrounds Taylor bubbles which reflected in a measurable enhancement of kLa. On the contrary, SMF pinned MNPs leading to systematically degraded gas-liquid mass transfer rates whereas axial oscillating magnetic field had no detectable effects on the mass transfer coefficient. Moreover, interaction between magnetic torque and hydrodynamic torque to dominate MNP spin direction was conceived from these results.
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Black, Gerald. "Chemical and electrochemical routes to novel heterocycles and the generation of quinone methides." Thesis, University of Bath, 1985. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303797.
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The structural assignment of the product from the palladium (11) promoted coupling of 3-benzoyl-1-methyl-indole was questioned, and thus alternative syntheses of the possible products were desired. Therefore both 1OH-5-methylindeno [1,2-b] indole and 6H-5-methylindeno-[2,1-b] indole were made, followed by attempts to oxidise the methylene group of both compounds. Eventually X-ray crystallography was used to confirm the product as 5-methylindeno [1,2-b] indole-10-one. Isochroman-3-one, 3,1-benzoxazin-3-one, and 1,4-dihydropyrano [4,5-b] indole-3-one were considered to be suitable precursors to their respective quinone methide intermediates, therefore substituted derivatives of these systems were required. Such derivatives in the isochromanone and benzoxazinone series were made, and an investigation of their behaviour during flash vacuum pyrrolysis undertaken. Attempts to make 1,4-dihydro-pyrano [4,5-b]indole-3-one were unsuccessful as the reduction of methyl 3-formyl-1 methylindolylacetate gave a "dimeric" compound rather than the desired product. The synthesis of 6,7-dimethoxy-4-(3,4-dimethoxy-phenylothyl) isochroman-3-one was achieved, and this compound was subjectod to electro-oxidation . The product was eventually proven to be 12H-3a,4,5-9b-tetrahydro- 7,8,11-trimethoxy-12-oxonaphtho [2 ,1 - d ] isochroman-3-one. Treatment of this compound with methylamine gave 11 11H-2a, 3, 4, 12, 12a-hexahydro-12a-hydroxymethyl-6,7,10-trimethoxy-1-methyl-11-oxonaphtho[2,1-c] oxindole. Finally studies towards an alternative synthesis of this novel ring system have been undertaken.
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Noor, N. "The chemical vapour deposition of transparent conducting oxides : exploring routes toward improved functionality." Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1435738/.
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Transparent conducting oxide (TCO) thin films were synthesised by different chemical vapour deposition (CVD) techniques, including aerosol-assisted CVD (AACVD) and atmospheric-pressure CVD (APCVD). Such methods were used to control deposition of primarily SnO2-based TCO films, as well as TiO2, allowing for in-depth analysis of properties for improved control and functionality. Investigations were carried out using a variety of techniques including x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), ultraviolet (UV) Transmittance-Reflectance, Raman spectroscopy and Hall Effect probe measurements. Variation of AACVD deposition parameters in an attempt to improve overall SnO2-TCO properties illustrated how a metathesis reaction (a halide exchange at the Sn-centre) in the precursor is an important step for the formation of high-performing films. Such deposited films exhibit values comparable to the best-performing commercial materials (sheet resistances as low as 3 ohm/square for a 600 nm thick film and figures-of-merit often greater than 2) depending on the defect site identity of the extrinsic dopant. Exploration of various dopant effects on the SnO2 system were also carried out. Fluorine, commonly regarded as the best halide dopant, was confirmed as such (with optical transmittances of 81 % and sheet resistances of 7 ohm/square for a 698 nm thick film), as compared to the other halides. Furthermore, a non-competitive, double-substitutional doping of the SnO2 system, concurrently utilising fluorine and various metal dopants, yields novel methods for control of TCO film morphology (and the attendant optical haze characteristics) and improved electrical properties (resistivities of the order of 10-4 ohm.cm and carrier concentrations of 1020 cm-3 or higher). Such control is highly useful in tailoring TCO functionality to its use, so maximising effectiveness and output for commercial applications. The final chapter explores a novel TCO system, TiO2, and its potential as a TCO material, coupled to its more established materials (e.g.; photocatalytic and wetting) properties. Experimental APCVD values of systems doped with dopants such as uorine, niobium, nitrogen and tungsten (with resistivities ranging 10-1 - 102 Ω.cm and optical transmittances of approximately 70 %, extending into long-wavelength regions) show it is an interesting material worthy of study but that further improvements are clearly required to make it a commercially viable TCO system. The improved mechanistic understanding and synthetic control afforded by the work presented in this thesis should help prepare thin film crystalline TCO systems to meet demands for the next-generation of functional materials applications.
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Le, Cong Nha. "Fabrication processes by chemical routes of textured Barium ferrite compacts for non reciprocal microwave devices." Thesis, Brest, 2018. http://www.theses.fr/2018BRES0046.
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Il existe actuellement un important besoin en dispositifs électroniques dans le domaine des longueurs d’ondes millimétriques, tels que les circulateurs et les isolateurs fonctionnant dans la gamme de fréquence 30-100 GHz. Les aimants permanents qui garantissent la propagation de l’onde électromagnétique dans ces dispositifs comportent très généralement des éléments terres rares. En raison du coût à l’acquisition de ces éléments, d’une part, ainsi que de leur coût environnemental d’autre part, il existe une demande d’aimants permanents produits sans terres rares. Les ferrites durs peuvent présenter les propriétés demandées pour une intégration dans les dipositifs micoondes non réciproques. Ainsi, les particules de ferrite de baryum (BaM) possèdent un champ d’anisotropie magnétocristallin important, dirigé selon l’axe de facile aimantation. Un matériau autopolarisé, constitué d’un empilement de ces particules, peut donc présenter une aimantation permanente d’intensité suffisante pour les applications visées. De nombreuses méthodes d’élaboration de tels matériaux ont été mises au point. Cependant les mises en oeuvre de ces méthodes sont contraignantes. En revanche, nous avons mis au point dans le présent travail un processus de réalisation de ferrites de BaM massifs autopolarisés, dont l’aspect technologique est simple (basé sur des méthodes de chimie douce et des traitements thermiques adaptés), et très abordable financièrement. Les résultats obtenus sont très compétitifs (aimantation rémanente normalisée MR/MS comprise entre 0.87 et 0.90. Le champ coercitif HC atteint la valeur de 303 kA/m, rendant le matériau peu sensible aux effets démagnétisants), et permettent d’envisager la production de ces matériaux en vue d’applications à des fréquences allant jusqu’à 55 GHzPresently, there is a critical need for millimeter wave devices, among which are non-reciprocal devices such as isolators and circulators, which operate in the frequency range from about 30 GHz to 100 GHz.Permanent magnets that ensure the propagation of the wave in such devices are for long based on rare-earth elements. Nowadays, the escalation of rare earths cost encourages to look for alternative materials containing much less, or no, rare earth elements selected from the most common and most available. Alternatively, hard ferrites may show the required potential for integration into non-reciprocal microwave devices. Barium ferrite (BaM) is a wellknown, high-performance, permanent magnet material with a large magneto-crystalline anisotropy along the c-axis of its hexagonal structure. A suitable form of barium ferrite for mm-wave applications is a magnetically oriented bulk material.Several constraining processing techniques were therefore set up to perform the alignment and compaction of plate hexaferrite particles. In contrast to these methods, the present study demonstrates the feasibility of simple alternative ways to provide highly oriented bulk compacts made of BaM particles. In the present work efficient and inexpensive chemical processes (co-precipitation, dry mixing and wet mixing) are presented that produces highly oriented bulk compacts made of Barium hexaferrites (BaM) particles. Hysteresis loops that display very competitive squarenesses between 0.87 and 0.90 (normalized remanent magnetization) and coercivity as high as 303 kA/m are obtained. The sensitivity to demagnetizing effects is therfore reduced. These properties make these BaM bulk ferrite materials suitable for selfbiased applications at frequencies up to 55 GHz
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Saarinen, Gabrielle. "Development of Synthetic Routes for Preparation of 2,6-Disubstituted Spiro[3.3]heptanes." Thesis, Mälardalen University, School of Sustainable Development of Society and Technology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-6027.
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2,6-Disubstituted spiro[3.3]heptanes were synthesized to investigate and develop synthetic methods for preparation of these compounds. Possibilities for introducing different functionalities like nitriles and sulfonamides were also investigated.
Synthetic routes presented describe successive [2+2] cycloadditions between dichloroketene and olefins to give the sought after spiro compounds with low to moderate yields throughout the multi-step synthesis. [2+2] Cycloadditions offered low turnovers and chromatography was required for purification.
A synthetic route with cyclisations through double substitution reactions between di-electrophiles and di-nucleophiles resulting in a 2,6-disubstituted spiro[3.3]heptane is also described. This multi-step synthesis offered higher turnover and yields and often there was no need for purification through chromatography.
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Bernardo, Maria Manuel Serrano. "Physico-chemical characterization of chars produced in the co-pyrolysis of wastes and possible routes of valorisation." Master's thesis, Faculdade de Ciências e Tecnologia, 2011. http://hdl.handle.net/10362/10213.
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Thesis submitted for the Degree in Master of Energy and BioenergyA presente dissertação tem como objectivo principal o estudo da valorização dos carvões obtidos na co-pirólise de resíduos de plásticos, pneus e biomassa florestal. Os carvões pirolíticos foram submetidos a um tratamento multietápico tendo em vista a obtenção de materiais carbonosos de valor acrescentado. Realizou-se uma caracterização físico-química dos carvões tratados tendo em vista o estudo de possíveis aplicações destes materiais, nomeadamente, a possibilidade de serem utilizados como adsorventes de poluentes. Os carvões pirolíticos brutos foram submetidos a uma extracção sequencial com solventes orgânicos de polaridade crescente seguida de uma desmineralização ácida. Os resultados obtidos demonstraram que o procedimento multietápico realizado garantiu uma descontaminação eficiente dos carvões, permitindo a recuperação de uma fracção significativa dos óleos da pirólise e/ou de subprodutos condensados que ficaram retidos nos carvões brutos, assim como uma redução significativa do seu conteúdo em cinzas. O procedimento de desmineralização ácida realizado permitiu também concluir que os metais pesados maioritários, assim como os mais tóxicos, estão significativamente imobilizados e retidos na matriz dos carvões, desde que não sejam aplicadas condições acídicas agressivas. A análise elementar aos carvões permitiu determinar heteroátomos como o oxigénio, enxofre e azoto, sendo este facto indicativo da presença de grupos funcionais na superfície dos carvões, o que representa um interesse acrescido relativamente à adsorção de poluentes orgânicos e inorgânicos específicos. As propriedades texturais e de adsorção dos carvões tratados foram determinadas e os resultados obtidos indicaram que estes carvões são predominantemente materiais meso e macroporosos, com capacidade para adsorver moléculas volumosas. O tratamento aplicado aos carvões permitiu obter materiais carbonáceos com qualidade suficiente para serem reutilizados como adsorventes ou como percursores de carvão activado.
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Hussain, Shahed. "The development of novel biocatalytic routes for the synthesis of enantiomerically-pure chiral amines." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/the-development-of-novel-biocatalytic-routes-for-the-synthesis-of-enantiomericallypure-chiral-amines(eba89b88-6801-40cc-a3c3-9c5f1c518d0f).html.
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Chiral amines represent a pervasive structural motif found in various natural products, pharmaceuticals, agrochemicals and fine chemicals. Their preparation in single-enantiomer form continues to attract significant research attention and although many advances have been made in the area of synthetic organic chemistry to increase the scope of the routes to these moieties, there remains an ever-growing need of general strategies for the assembly of structurally-diverse amines which also conform to the efficiency and environmental requirements of modern manufacturing processes. This report investigates biocatalytic routes as a means for constructing chiral amine scaffolds, which offer a more environmentally benign approach when compared with traditional chemocatalysed processes. Probing the catalysts available in the biocatalytic toolbox of enzymes, several routes were examined in more detail. Imine reductases (IREDs) represent a recent addition to the toolbox, enzymes which by definition are able to reduce pre-formed imines to their corresponding amines with high selectivity. This report analyses the (R)-imine reductase [(R)-IRED] from Streptomyces sp. GF3587, one of the first imine reductases identified for its biocatalytic potential, in greater depth. The enzyme was found to catalyse the reduction of a broad range of cyclic imines while displaying high levels of activity and selectivity, thereby offering a direct route of access to chiral secondary and tertiary amines. Substrate kinetic parameters were established for the enzyme in order to understand its substrate preferences and the enzymeâs catalytic mechanism was probed through the generation of mutant (R)-IREDs. Owing to their operation under physiological conditions as well as the orthogonal nature of their reactions, it is possible to combine multiple enzyme reactions to enable cascades. This report examines a multi-enzyme reaction combining Ï-transaminases (ATAs) with imine reductases, for the synthesis of chiral disubstituted piperidines from simple diketone substrates. The cascade was then taken a step further by the inclusion of the carboxylic acid reductase (CAR) enzyme, for the synthesis of the nitrogen-containing heterocycles morpholine and thiomorpholine from ketoacid compounds. Finally, the well-established deracemisation technique, employing a selective amine oxidase (AO) with either a non-selective chemical reducing agent or a biocatalytic reductant (IRED), was explored in more detail by encompassing new substrate motifs. As biocatalysis becomes more readily accepted as a general technique in the synthetic chemistâs repertoire, the concept of carrying out enzymatic reactions in constant flow was explored as a means for applying this methodology with increased production and decreased processing rates.
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Hubert, Mathieu. "Chalcogenide Glasses for Infrared Applications: New Synthesis Routes and Rare Earth Doping." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/223357.
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Chalcogenide glasses and glass-ceramics present a high interest for the production of thermal imaging lenses transparent in the 3-5 μm and 8-12 μm windows. However, chalcogenide glasses are conventionally synthesized in sealed silica ampoules which have two major drawbacks. First, the low thermal conductivity of silica limits the sample dimensions and second the silica tubes employed are single use and expensive, and represent up to 30% of the final cost of the material. The present work therefore addresses the development of innovative synthesis methods for chalcogenide glass and glass-ceramics that can present an alternative to the silica tube route. The method investigated involves melting the raw starting elements in reusable silica containers. This method is suitable for the synthesis of stable chalcogenide glasses compositions such as GeSe₄ but uncontrolled crystallization and homogenization problems are experienced for less stable compositions. The second approach involves preparation of amorphous chalcogenide powders by ball milling of raw elements. This mechanosynthesis step is followed by consolidation of the resulting powders to produce bulk glasses. Hot Uniaxial Pressing is suitable for compositions stable against crystallization. However, uncontrolled crystallization occurs for the unstable 80GeSe₂-20Ga₂Se₃ glass composition. In contrast consolidation through Spark Plasma Sintering (SPS) allows production of bulk glasses in a short duration at relatively low temperatures and is appropriate for the synthesis of unstable glasses. A sintering stage of only 2 min at 390°C is shown to be sufficient to obtain infrared transparent 80GeSe₂-20Ga₂Se₃ bulk glasses. This method enables the production of lenses with a 4-fold increase in diameter in comparison to those obtained by melt/quenching technique. Moreover, increasing the SPS treatment duration yielded infrared transparent glass-ceramics with enhanced mechanical properties. This innovative synthesis method combining mechanosynthesis and SPS has been patented in the framework if this study. The controlled etching of 80GeSe₂-20Ga₂Se₃ glass-ceramics in acid solution yields nanoporous materials with enhanced surface area. The porous layer created on the surface of the glass-ceramic is shown to play the role of anti-reflection coating and increase the optical transmission in the infrared range by up to 10%. These materials may have potential for the production of sensors with increased sensitivity in the infrared. The influence of indium and lead addition on the thermal and optical properties of the 80GeSe₂-20Ga₂Se₃ glass has also been assessed. Increased In or Pb contents tend to decrease the Tg of the glasses and shift the optical band gap toward higher wavelengths. A systematic ceramization study emphasizes the difficulty of controlling the crystallization for glasses in the systems GeSe₂-Ga₂Se₃-In₂Se₃ and GeSe₂-Ga₂Se₃-PbSe. No crystallization of the In₂Se₃ and PbSe crystalline phase was obtained. Finally, the possibility of producing rare-earth doped 80GeSe₂-20Ga₂Se₃ glass-ceramics transparent in the infrared region up to 16 μm is demonstrated. Enhanced photoluminescence intensity and reduced radiative lifetimes are observed with increased crystallinity in these materials.
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Garcia-Hernandez, Margarita. "Luminescent systems of Ln (Ln=Er3+, Yb3+ , Eu3+) doped BaTiO3 nanostructured powders and films prepared by soft chemical routes." Clermont-Ferrand 2, 2010. http://www.theses.fr/2010CLF22040.
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Ce travail concerne, la synthèse, la caractérisation structurale, morphologique et optique de matrices de titanates de baryum (BaTiO3) activées par les ions Eu3+, Er3+ et Yb3+. Trois voies de synthèse sont étudiées : sol-gel, hydrothermale et solide. Il a été montré que la synthèse hydrothermale conduisait à des poudres nanométriques constituées de particules de 20 nm, dix fois plus petites que celles rencontrées dans les poudres obtenues par les techniques classiques de céramisation. L' influence de ce paramètre sur la structure cristallographique des titanates a pu être mise en évidence. L'ajout d'agents chélatants au cours de la synthèse sol-gel permet de modifier la morphologie des poudres et de stabiliser les sols destinés à l'élaboration de revêtements. Des films épais monocouche ( 800 nm) de titanates de baryum dopés Er3+ et Eu3+ ont été ainsi obtenus. Une étude des propriétés optiques des ions de terres rares dans les différents systèmes synthétisés a été menée en enregistrant les différents spectres d'exitation et d'émission. Les phénomènes de transfert d'énergie entre les ions de terres rares ont été étudiés dans les matrices co-dopées
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Calvaruso, Gaetano [Verfasser], Roberto [Gutachter] Rinaldi, and Martin [Gutachter] Muhler. "On the chemical conversion of Lignin and Lignin streams \(\it via\) reductive routes / Gaetano Calvaruso ; Gutachter: Roberto Rinaldi, Martin Muhler." Bochum : Ruhr-Universität Bochum, 2017. http://d-nb.info/1127335057/34.
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Krasnopolski, Michael [Verfasser], Roland A. [Gutachter] Fischer, and Anjana [Gutachter] Devi. "Metalorganic chemical vapor deposition (MOCVD) routes for fabrication of rare earth nitride thin films : precursor evaluation, thin film deposition and characterization / Michael Krasnopolski ; Gutachter: Roland A. Fischer, Anjana Devi ; Fakultät für Chemie und Biochemie." Bochum : Ruhr-Universität Bochum, 2014. http://d-nb.info/1231542314/34.
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Gomes, baltazar alves Gabriel. "The Wide Extent of Reactivity Descriptors Applicability : From Chemical Pathway Predictor to Charge Transference and Transport Description." Electronic Thesis or Diss., Pau, 2025. http://www.theses.fr/2025PAUU3017.
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L’utilisation d’outils computationnels en sciences des matériaux constitue un domaine établi, la théorie de la fonctionnelle de la densité (DFT) s’étant imposée depuis près de cinquante ans comme un fondement de la physique de l’état solide. L’évolution des technologies numériques a permis un accroissement notable de la précision et de la fiabilité des méthodes de simulation, au prix cependant d’un coût computationnel et énergétique croissant. Dans ce contexte, l’emploi de descripteurs de réactivité s’avère particulièrement pertinent : ces outils, à la fois simples sur les plans théorique et numérique, offrent des résultats robustes et en excellent accord avec les données expérimentales ainsi qu’avec des méthodes de calcul plus onéreuses.Le travail présenté propose d’élargir l’usage classique des descripteurs de réactivité, traditionnellement limités à l’identification de sites réactifs, vers de nouvelles applications. Dans un premier temps, les indices de Fukui atomiques condensés ont été mobilisés pour caractériser les sites donneurs et accepteurs d’électrons au sein de molécules candidates à des applications en cellules photovoltaïques organiques. Cette approche permet ainsi de prédire l’efficacité potentielle de matériaux pour le transfert de charges photoinduit. Dans un second temps, le concept de souplesse locale, dérivé de la souplesse globale, est employé pour identifier, au sein d’une même molécule, les atomes susceptibles d’interagir. Cette stratégie vise à proposer des chemins réactionnels internes, en particulier pour élucider la conversion du 1-azafulvénallène en phénylnitrène, une transformation d’intérêt en chimie organique.Les résultats obtenus démontrent que, malgré leur simplicité, les descripteurs de réactivité offrent une capacité prédictive étendue, non seulement en matière d’analyse de réactivité, mais également pour la description fine des transferts de charge et l'identification de voies de réaction moléculaires. Ces travaux ouvrent ainsi des perspectives nouvelles pour l’exploitation de méthodes computationnelles légères au service de problématiques complexes en chimie des matériauxThe use of computational tools in material science is not a novelty, for instance, Density Functional Theory has been a staple for solid-state physics for about fifty years. As time goes by, technology evolves, and so do the computational methods, their accuracy and reliability. Of course, the more complex and complete a method is, the more computationally expensive it becomes. An expensive method is one that requires a lot of CPU time to be finished, thus requiring more energy. However, there are some tools to be used that are not expensive and also produce reliable results. One of these tools are the reactivity descriptors, which are theoretically and computationally simple, but have been offering great reliable results, aligned with other methods and experimental data. This work set out to explore new grounds with the reactivity descriptors, using them for more than reactivity calculations. In the first chapter, the descriptor called Condensed-to-Atoms Fukui Indexes, that is generally used to describe reactive sites in a molecule, is used to as a mean to describe sites for electron retrieval and receival, as a tool to define what is a good or bad electron donor/acceptor material for Organic Solar Cells applications. Moreover, the second chapter applies the global softness to the previous descriptor to build what is called Local Softness, a descriptor used to classify how likely two molecules are prone to interact and with which atoms. However this descriptor is used here as a method to search atoms likely to interact with each other in the same molecule, altering its structure and becoming a new molecule. This is done to help find pathways for the 1-azafulvenallene to become phenylnitrene. The results point that indeed, although simple, the reactivity descriptors are capable of producing reliable and accurate results that go beyond just reactivity studies and can be used for charge transference description and to find chemical reaction pathways
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Silva, Isác Almeida da. "Sinterização e caracterização estrutural, térmica e elétrica do compósito BiSrCaCu0 (coprecipitado)." Universidade Presbiteriana Mackenzie, 2014. http://tede.mackenzie.br/jspui/handle/tede/1338.
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Previous issue date: 2014-02-05The so-called low-temperature physics had its development from studies of the dutch physicist Karmelingh Onnes, in the early twentieth century (1908), when he first got the liquefaction of helium. Studying thereafter the behavior of chemicals at low temperatures, three years after he found that resistance to the passage of electric current of mercury fell to zero for temperature equal to 4,2 K or -269ºC. This phenomenon came to be called superconductivity. In the following years many metallic superconductors were found, all, however, with a very low critical temperature. Intending to raising this temperature, doping in composite superconductors, such as BSCCO BiSrCaCuO have been made. In this research, physical and chemical properties of BSCCO composite were studied and discussed. This was done after different sintering routes. The precursor solutions were prepared by M. Pechini method, obtaining a material in powder form that was milled, calcinated, pressed, sintered, and then the characterization of samples was carried out using X-ray diffraction (XRD), electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The crystal structure of the material was refined by Rietveld method, by factors of disagreement Rwp = 5,43% e RBragg = 2,54%, checking 91,3% of phase 2234 BSCCO composite, which it is highly superconducting and rarely obtained together with 8,7% of other phases.
A denominada física de baixas temperaturas teve o seu desenvolvimento a partir dos estudos do físico holandês Karmelingh Onnes, no início do século XX (1908), quando pela primeira vez obteve a liquefação do hélio. Estudando a partir de então o comportamento de elementos químicos a baixas temperaturas, ele constatou três anos depois que a resistência à passagem da corrente elétrica do mercúrio sofreu uma queda a zero, quando à temperatura de 4,2 K, - 269 °C. Este fenômeno passou a ser chamado de supercondutividade. Nos anos seguintes muitos materiais metálicos supercondutores foram encontrados, todos, porém, com uma temperatura crítica baixíssima. Com a intenção de elevar esta temperatura, dopagens em compósitos supercondutores, tais como o BSCCO BiSrCaCuO vêm sendo efetuadas. Neste trabalho foram estudadas, discutidas e comparadas as propriedades físicas e químicas do compósito BSCCO após rotas distintas de sinterização. As soluções precursoras foram preparadas pelo método de M. Pechini, obtendo-se um material em forma de pó que, após moagem, calcinação, prensagem e sinterização, foram caracterizados, utilizando-se difração de raios X (DRX), microscopia eletrônica (MEV) e espectroscopia de energia dispersiva (EDS).. A estrutura cristalina do material obtido foi refinada até fatores de discordância Rwp = 5,43% e RBragg = 2,54%, verificando-se a presença de 91,3% da fase 2234 do compósito BSCCO, altamente supercondutora e de rara obtenção e 8,7% de outras fases.
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Stridh, Malin. "Glial hemichannels : a new route for chemical communication in brain /." Göteborg : Dept. of Physiology, Institute of Neuroscience and Physiology, Sahlgrenska Academy at University of Gothenburg, 2008. http://hdl.handle.net/2077/9880.
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Parker, Gemma M. "A new route to polyhydric alcohols." Thesis, University of Glasgow, 2009. http://theses.gla.ac.uk/620/.
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Pentaerythritol is an important industrial chemical for use in paints and coatings, primarily, but also in fuels, explosives, medicine and polymers. The current process for this material is over 50 years old and is a multi-step process involving 3 homogeneous aldolizations and a crossed Cannizzaro reaction, generating 1.5 tonnes of waste for every 4 tonnes of product. This is also very energy inefficient. We are currently developing a radically different concept, shown below. This will deliver an integrated heterogeneous catalytic process with no waste and a high energy and materials efficiency. Methanol/ Dehydrogenation Base Hydrog Ethanol Catalyst Catalyst Catalyst Pentaerythritol The initial step, CH3OH HCHO + H2, will involve the use of Ag/SiO2 catalysts. This will be in the absence of O2, which differs from the current oxidative dehydrogenation process used to produce HCHO, i.e. a direct dehydrogenation. This step has been optimised by investigation of different surface properties to determine how surface area and dispersion will affect the overall adsorption and consequently the methanol/ethanol conversion and product yields. Deactivation of these catalysts has also been touched on by use of in-situ temperature programmed oxidation’s. Base catalysis involving an aldol type reaction of 2 aldehydes, HCHO and CH3CHO, will give the methylolated aldehyde intermediate. This will then undergo a final hydrogenation to the desired product. Any unreacted aldehydes will, therefore, be hydrogenated back to starting materials and consequently recycled. It will be attempted to couple all three reactions to explore how the catalysts perform when used in succession.
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Shahine, Issraa. "A chemical route to design plasmonic-semiconductor nanomaterials heterojunction for photocatalysis applications." Thesis, Université de Lorraine, 2019. http://www.theses.fr/2019LORR0105/document.
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L’ingénierie de nanomatériaux hybrides semi-conducteurs/plasmoniques représente une technologie durable en raison de l’efficacité parfaite du couplage pour améliorer, rénover et enrichir les propriétés des composants intégrés. Ce couplage a pour résultat la variation des propriétés fonctionnelles du système, grâce auquel les plasmons de surface générés par les métaux peuvent améliorer la séparation des charges, l’absorption de la lumière et la luminescence du semi-conducteur. Ce phénomène permet de fortes interactions avec d'autres éléments photoniques tels que les émetteurs quantiques. Ces fonctionnalités aux multiples facettes découlent de l'interaction synergique exciton-plasmon entre les unités liées. Ainsi, les nanomatériaux hybrides conviennent à diverses applications, notamment : conversion de l'énergie solaire, dispositifs optoélectroniques, diodes électroluminescentes (LED), photocatalyse, détection biomédicale, etc. Les nanostructures Au-ZnO suscitent un intérêt croissant dans ces applications où le couplage de ZnO à de nanoparticules d’or (GNPs) favorise la réponse du système dans le domaine du visible grâce à leur résonance plasmon de surface (SPR). En fonction de la taille de deux nanomatériaux, de la distance qui les sépare et leurs rapports massiques dans un échantillon, les propriétés des particules hybrides peuvent varier. Dans ce contexte, nous nous sommes concentrés sur la construction de nano-cristaux (NCs) de ZnO purs de dimensions contrôlables, puis incorporés dans des solutions de GNPs par une simple voie chimique. Ce travail est divisé en deux parties : la première consiste à effectuer une synthèse de nanocristaux de ZnO (NCs) purs présentant d'excellentes propriétés de photoluminescence dans l’UV. Ceci a été réalisé par une synthèse à basse température, aboutissant à des structures rugueuses et amorphes. La synthèse a été suivie d'un traitement post-thermique afin de cristalliser les nanoparticules obtenues. Une étude structurale et optique poussée a été établie à la suite de la synthèse (SEM, TEM, DRX, photoluminescence). Les activités photocatalytiques des ZnO NCs ont été étudiées en mesurant leur capacité à dégrader le bleu de méthylène (MB). De plus, la relation entre les structures en ZnO, la luminescence et les propriétés photocatalytiques a été explorée en détail. Dans la deuxième étape, les ZnO NCs obtenus ont été couplés ajoutés à des nanoparticules d'or de tailles et fractions volumiques variables. Le rôle effectif des GNPs concernant leur morphologie, leur contenu et leur effet SPR sur la photoémission des nanostructures de ZnO est souligné par le transfert de charge et / ou d'énergie entre les constituants du système hybride. De plus, l’activité photocatalytique du système hybride a été examinée. Comme débouché et perspective de ce travail de thèse, l'intégration des ZnO NC dans une couche nanoporeuse de polymère (PMMA) a été réalisée et caractérisée afin d'obtenir un substrat de large surface à base de ZnO. Les ZnO NCs assemblés dans du PMMA pourraient être des substrats prometteurs en tant que catalyseurs pour la croissance de nanofils de ZnO, de nanomatériaux métalliques et de matériaux hybridesHybrid heterojunctions composed of semiconductors and metallic nanostructures have perceived as a sustainable technology, due to their perfect effectiveness in improving, renovating, and enriching the properties of the integrated components. The cooperative coupling results in the variation of the system’s functional properties, by which the metal-generated surface plasmon resonance can enhance the charge separation, light absorption, as well as luminescence of the semiconductor. This phenomenon enables strong interactions with other photonic elements such as quantum emitters. These multifaceted functionalities arise from the synergic exciton-plasmon interaction between the linked units. Thereby, hybrid systems become suitable for various applications including: solar energy conversion, optoelectronic devices, light-emitting diodes (LED), photocatalysis, biomedical sensing, etc. Au-ZnO nanostructures have received growing interest in these applications, where the deposition of gold nanoparticles (GNPs) promotes the system’s response towards the visible region of the light spectrum through their surface plasmon resonance (SPR). Based on a specific size and purity of ZnO nanostructures, as well as the GNPs, and a definite inter-distance between the nanoparticles, the properties of the ZnO nanostructures are varied, especially the photoemission and photocatalytic ones. In this context, we have focused on the construction of size-tunable ZnO nanocrystals (NCs), then incorporated into GNPs solutions using a simple chemical way. This work is divided into two parts: the first is to perform synthesis of pure ZnO NCs having excellent UV photoluminescence. This was achieved through a low-temperature aqueous synthesis, resulting in rough and amorphous structures. The synthesis was followed by a post-thermal treatment in order to crystallize the obtained particles. The synthesis was followed by structural and optical studies (SEM, TEM, XRD, photoluminescence). The photocatalytic activities of ZnO NCs were studied through tailoring their ability to degrade the methylene blue (MB) dye. In addition, the relationship between ZnO structures, luminescence, and photocatalytic properties was explored in details. In the second step, the obtained ZnO NCs were added to gold nanoparticles of various sizes and volume fractions. The effective role of GNPs concerning their size, amount, and their capping molecule on the photoemission of the ZnO nanostructures was emphasized through the charge and/or energy transfer between the constituents in the hybrid system. In the same way, the systems photocatalytic activities were examined after coupling ZnO to GNPs. Further advancement in the integration of the ZnO NCs into PMMA polymer layers was featured in order to obtain large area template of homogenous ZnO properties. The PMMA-assembled ZnO nanoparticles could be promising substrates as catalysts for growing ZnO nanowires, metallic nanoparticles and hybrid nanomaterials
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Shahine, Issraa. "A chemical route to design plasmonic-semiconductor nanomaterials heterojunction for photocatalysis applications." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0105.
Full textAbstract:
L’ingénierie de nanomatériaux hybrides semi-conducteurs/plasmoniques représente une technologie durable en raison de l’efficacité parfaite du couplage pour améliorer, rénover et enrichir les propriétés des composants intégrés. Ce couplage a pour résultat la variation des propriétés fonctionnelles du système, grâce auquel les plasmons de surface générés par les métaux peuvent améliorer la séparation des charges, l’absorption de la lumière et la luminescence du semi-conducteur. Ce phénomène permet de fortes interactions avec d'autres éléments photoniques tels que les émetteurs quantiques. Ces fonctionnalités aux multiples facettes découlent de l'interaction synergique exciton-plasmon entre les unités liées. Ainsi, les nanomatériaux hybrides conviennent à diverses applications, notamment : conversion de l'énergie solaire, dispositifs optoélectroniques, diodes électroluminescentes (LED), photocatalyse, détection biomédicale, etc. Les nanostructures Au-ZnO suscitent un intérêt croissant dans ces applications où le couplage de ZnO à de nanoparticules d’or (GNPs) favorise la réponse du système dans le domaine du visible grâce à leur résonance plasmon de surface (SPR). En fonction de la taille de deux nanomatériaux, de la distance qui les sépare et leurs rapports massiques dans un échantillon, les propriétés des particules hybrides peuvent varier. Dans ce contexte, nous nous sommes concentrés sur la construction de nano-cristaux (NCs) de ZnO purs de dimensions contrôlables, puis incorporés dans des solutions de GNPs par une simple voie chimique. Ce travail est divisé en deux parties : la première consiste à effectuer une synthèse de nanocristaux de ZnO (NCs) purs présentant d'excellentes propriétés de photoluminescence dans l’UV. Ceci a été réalisé par une synthèse à basse température, aboutissant à des structures rugueuses et amorphes. La synthèse a été suivie d'un traitement post-thermique afin de cristalliser les nanoparticules obtenues. Une étude structurale et optique poussée a été établie à la suite de la synthèse (SEM, TEM, DRX, photoluminescence). Les activités photocatalytiques des ZnO NCs ont été étudiées en mesurant leur capacité à dégrader le bleu de méthylène (MB). De plus, la relation entre les structures en ZnO, la luminescence et les propriétés photocatalytiques a été explorée en détail. Dans la deuxième étape, les ZnO NCs obtenus ont été couplés ajoutés à des nanoparticules d'or de tailles et fractions volumiques variables. Le rôle effectif des GNPs concernant leur morphologie, leur contenu et leur effet SPR sur la photoémission des nanostructures de ZnO est souligné par le transfert de charge et / ou d'énergie entre les constituants du système hybride. De plus, l’activité photocatalytique du système hybride a été examinée. Comme débouché et perspective de ce travail de thèse, l'intégration des ZnO NC dans une couche nanoporeuse de polymère (PMMA) a été réalisée et caractérisée afin d'obtenir un substrat de large surface à base de ZnO. Les ZnO NCs assemblés dans du PMMA pourraient être des substrats prometteurs en tant que catalyseurs pour la croissance de nanofils de ZnO, de nanomatériaux métalliques et de matériaux hybridesHybrid heterojunctions composed of semiconductors and metallic nanostructures have perceived as a sustainable technology, due to their perfect effectiveness in improving, renovating, and enriching the properties of the integrated components. The cooperative coupling results in the variation of the system’s functional properties, by which the metal-generated surface plasmon resonance can enhance the charge separation, light absorption, as well as luminescence of the semiconductor. This phenomenon enables strong interactions with other photonic elements such as quantum emitters. These multifaceted functionalities arise from the synergic exciton-plasmon interaction between the linked units. Thereby, hybrid systems become suitable for various applications including: solar energy conversion, optoelectronic devices, light-emitting diodes (LED), photocatalysis, biomedical sensing, etc. Au-ZnO nanostructures have received growing interest in these applications, where the deposition of gold nanoparticles (GNPs) promotes the system’s response towards the visible region of the light spectrum through their surface plasmon resonance (SPR). Based on a specific size and purity of ZnO nanostructures, as well as the GNPs, and a definite inter-distance between the nanoparticles, the properties of the ZnO nanostructures are varied, especially the photoemission and photocatalytic ones. In this context, we have focused on the construction of size-tunable ZnO nanocrystals (NCs), then incorporated into GNPs solutions using a simple chemical way. This work is divided into two parts: the first is to perform synthesis of pure ZnO NCs having excellent UV photoluminescence. This was achieved through a low-temperature aqueous synthesis, resulting in rough and amorphous structures. The synthesis was followed by a post-thermal treatment in order to crystallize the obtained particles. The synthesis was followed by structural and optical studies (SEM, TEM, XRD, photoluminescence). The photocatalytic activities of ZnO NCs were studied through tailoring their ability to degrade the methylene blue (MB) dye. In addition, the relationship between ZnO structures, luminescence, and photocatalytic properties was explored in details. In the second step, the obtained ZnO NCs were added to gold nanoparticles of various sizes and volume fractions. The effective role of GNPs concerning their size, amount, and their capping molecule on the photoemission of the ZnO nanostructures was emphasized through the charge and/or energy transfer between the constituents in the hybrid system. In the same way, the systems photocatalytic activities were examined after coupling ZnO to GNPs. Further advancement in the integration of the ZnO NCs into PMMA polymer layers was featured in order to obtain large area template of homogenous ZnO properties. The PMMA-assembled ZnO nanoparticles could be promising substrates as catalysts for growing ZnO nanowires, metallic nanoparticles and hybrid nanomaterials
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Chirume, Blessing Hellen. "Investigation of a hydrometallurgical process route to recover metals from waste printed circuit boards." Master's thesis, Faculty of Engineering and the Built Environment, 2019. http://hdl.handle.net/11427/31434.
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The loss of valuable materials such as base and precious metals is increasing due to the increase in waste electronic and electric waste (WEEE). Most of these metals in WEEE are on the printed circuit boards (PCBs). This study aims to compare different pre-treatment methods to recycle copper from PCBs using a hydrometallurgical process. In order to obtain a uniform/consistent sample across all the tests done, similar custom-made PCBs with 55.45% wt copper were used to compare different parameters. Pre-treating the PCBs is the first stage of the process and it is done to liberate metals which are then dissolved in subsequent leaching stages. Eight different pre-treatment methods were explored. The pre-treated PCBs were then leached under similar conditions in a diagnostic leach test in order to get an indication of the effectiveness of the pre-treatment. Copper recoveries corresponding to each of the pretreatment methods were compared. In addition to recovery, other factors such as time taken for copper recovery, material losses incurred, practicability, environmental impact, health and safety were used to compare the pre-treatment methods. A score was given for each factor and the average was used to choose the optimal pre-treatment method. A method where the PCBs were cut into 1.5 cm x 2 cm pieces and then soaked in 2 M NaOH at 40 °C for 24 hours had the highest average score. This pre-treatment method was then used to prepare PCBs that were used for test work done with the aim to optimise copper leaching. The influence of total ammonia concentration, liquid to solid ratio and choice of ammonium salt used in the buffer system, were investigated in the copper leaching optimisation stage of this thesis. Using ammonium carbonate resulted in lower recoveries compared to ammonium sulphate in the diagnostic leach test. Increasing the ammonia concentration to 7M did not have a significant effect on the copper recovery. Decreasing the liquid to solid ratio from 20ml/g to 10ml/g resulted in a slower rate of recovery. The optimal leaching conditions were found to be; 750 ml mixture of 4 M NH3, 2 M (NH4)2SO4, 100ppm CuSO4 at 25 °C and 500 rpm using the optimal pre-treatment method for the PCBs.
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CROIN, LUCA. "A Si based technology route to chemical vapor deposition of large area graphene." Doctoral thesis, Politecnico di Torino, 2015. http://hdl.handle.net/11583/2593358.
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The era of two-dimensional materials has begun with graphene. It is the first artificially-isolated single-atom-thick material, which is also an exceptional example of its kind. With its extraordinary physical and chemical properties, it has become hugely popular among scientists and technologists isn a timeframe of less than a decade.
When first isolated, graphene has been a subject of fundamental research by condensed matter physicists. Later, the possibility to exploit graphene’s applicability have brought research toward methods for large scale production. One leading technique to obtain graphene is by its synthesis on sacrificial substrates by Chemical Vapor Deposition (CVD). Thus, a great deal of interest in research and development of graphene has risen all over the world.
This thesis work has been conducted at INRiM (Istituto Nazionale di Ricerca Metrologica) and has addressed the synthesis of graphene by CVD on copper, which has become the most popular catalyst for graphene growth. The entire CVD process, performed on both Cu thin films and foils, is here presented as well as transfer methods are discussed. Growth of graphene is discussed also in terms of direct deposition onto insulating substrates, and preliminary results are reported. Finally, a first approach on electrical characterization of graphene grown on Cu foils is described.
Although many aspect of graphene growth have been developed, the main work has been done on the growth of graphene on Cu thin films investigating the possibility of lowering the film thickness. This goal was in competition with dewetting phenomena: thin films energy minimization at high temperature, indeed, let the film to dewet forming holes and eventually islands. In chapter 3 is reported an analysis on Cu thin films dewetting, results of chapter 3 are used in chapter 4 where CVD on such thin films is reported. Chapter 5 deals with transferring methods of graphene, alongside of the "standard" method a new technique is proposed. In Chapter 6 the direct deposition onto insulating substrates is investigated via a method where Cu is used as a remote catalyzer. In the last chapter the electrical characterization of graphene is approached with the aim of demonstrating the feasibility of performing also this characterization procedure in INRiM labs.
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Galileu, Speranza Lais. "Development of a new route for direct conversion of wet algae to biodiesel." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7591/.
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Algae have been studied as a potential biodiesel feedstock by identifying on a global scale suitable cultivation locations for three specific cases (EU, US and Brazil) based on the area requirements. A direct conversion of oil harvested from wet algae to biodiesel was undertaken using ethanol at supercritical conditions, eliminating the use of catalyst, feedstock drying and the oil extraction steps. Chlorella vulgaris with 7.3% wt. lipid content was characterised (by elemental, chemical and thermal analyses) and used to assess the supercritical ethanol approach. A biodiesel yield of 47.5% wt. was achieved in a flow reactor at 260°C, 75 bar, aqueous algae concentration of 6 mg·mL-1 and 2 mL·min-1 flowrate. This result demonstrates the advantages of the flow reactor over a batch process where the maximum biodiesel yield was 26% wt. after 6 hours. A life cycle analysis of the proposed route showed that biodiesel yield must exceed 60% wt. to make the process competitive when compared to the traditional route of oil extraction and catalyst transesterification adopted to algae biodiesel production. In comparison to the soybean biodiesel, the use of algae as feedstock would not be justified unless improvements to reduce energy consumption are made.
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Viljanen, Johan. "A Novel Route for Construction of Multipurpose Receptors through Chemical Modification of Glutathione Transferases." Doctoral thesis, Linköpings universitet, Organisk Kemi, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-11612.
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This thesis describes how the human Alpha class glutathione transferase (GST) A1-1 can be reprogrammed either to function as a multipurpose biosensor for detection of small molecule analytes, or as a handle providing for more efficient protein purification. A novel, user-friendly, and efficient method for site-specific introduction of functional groups into the active site of hGST A1-1 is the platform for these achievements. The designed thioester reagents are glutathione-based and they are able to label one single nucleophile (Y9) and leave the other 50 nucleophiles (in hGST A1-1) intact. The modification reaction was tested with five classes of GSTs (Alpha, Mu, Pi, Theta and Omega) and was found to be specific for the Alpha class isoenzymes. The reaction was further refined to target a single lysine residue, K216 in the hGST A1-1 mutant A216K, providing a stable amide bond between the protein and the labeling group. To further improve the labeling process, biotinylated reagents that could deliver the acyl group to Y9 (wt hGST A1-1) or K216 in the lysine mutant, while attached to streptavidin-coated agarose beads, were designed and synthesized. A focused library of eleven A216K/M208X mutants was made via random mutagenesis to provide an array of proteins with altered micro-environments in the hydrophobic binding site, where M208 is situated. Through the invented route for site-specific labeling, a fluorescent probe (coumarin) was introduced on K216 in all double mutants, with the purpose of developing a protein-based biosensor, akin to the olfactory system. The array of coumarin-labeled proteins responded differently to the addition of different analytes, and the responses were analyzed through pattern recognition of the fluorescence signals. The labeled proteins could also be site-specifically immobilized on a PEG-based biosensor chip via the single C112 on the surface of the protein, enabling development of surface-based biosensing systems. Also, a refined system for efficient detection and purification of GST-fusion proteins is presented. Through a screening process involving A216K and all produced A216K/M208X mutants, two candidates (A216K and A216K/M208F) were singled out as scaffolds for the next generation of fusion proteins. In addition to the features present in commercially available GST fusion constructs, the new mutants can be site-specifically labeled with a fluorophore in bacterial lysates providing quick and sensitive monitoring of expression and purification. Furthermore, the proteins could be labeled with a unique aldehyde moiety providing for a novel protein purification scheme.
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Izsová, Radka. "Design centrum HANÁK NÁBYTEK a.s., Popůvky u Kojetína - příprava a organizace výstavby objektu." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-227002.
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This thesis addresses the Design centrum HANÁK NÁBYTEK a.s., Popůvky u Kojetína - This is a new object had the basement and a second floor. The thesis includes - Technical report on the construction technology of the project , which are described in each chapter building equipment, coordination of building relationships with the wider transport routes , the study of the main technological stages, the design of the main building machines and mechanisms. There is a solution on time and financial plan object , the schedule object SO03 - Rapid technological and construction timetable and plan for securing material resources SO03 object . This thesis addresses the technological specification for excavation work with the control and test plan then is solved problems of chemical anchoring pillars object SO203 , which are included tensile tests on chemical anchors.
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Girouard, Natalie. "Cellulose nanocrystal thermoset composites: A physical and chemical route to improving dispersion and mechanical properties." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54928.
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Cellulose nanocrystals (CNCs) are crystalline nanoparticles that are extracted from renewable sources such as trees or bacteria through mechanical or chemical treatments of their source. CNCs are of interest to several research communities concerned with sustainable technologies. Specifically, CNCs have attracted great interest in the polymer composite community given their high theoretical specific strength and modulus. Two key obstacles surround the use of CNCs in polymer composites, namely their comparatively lower thermal stability and hydrophilicity render their dispersion, and therefore mechanical reinforcement, in polymer matrices challenging. This research considered a waterborne epoxy and a polyurethane elastomer for CNC/polymer composites since these composites are seldom reported in literature or often suffer from degraded mechanical properties. In the epoxy/CNC composites, samples were prepared by two methods, first an epoxy emulsion was mixed with an amine crosslinker and an aqueous based CNC suspension (1-step mixing), and second, the epoxy emulsion was premixed with the aqueous based CNCs and the amine crosslinker was added some time later (2-step mixing). Both composites were mixed by magnetic stirring, however the samples prepared by the 2-step mixing method exhibited enhanced dispersion and mechanical properties, specifically the storage modulus (E’), tensile strength, and work of fracture. Zeta potential measurements and chemical analysis by FTIR indicated that the dispersion mechanism was physical in nature, rather than chemical. In the second composite system, CNCs were chemically modified with an isophorone diisocyanate (IPDI) monomer having unequally reactive isocyanate groups. The goal of the modification step was to react only one isocyanate group with the CNC surface and have a free isocyanate group available for further modification. The chemical structure of one linked isocyanate (urethane bond) and one free isocyanate was confirmed by FTIR and 13C NMR. The particles modified by IPDI (m-CNC) and the neat particles (um-CNC) were incorporated into a polyurethane matrix based on IPDI and a triol crosslinker. Upon visual inspection of the cured composites, it was clear that the modification step produced homogeneously dispersed nanoparticles in the polyurethane while the um-CNCs were aggregated. When the mechanical properties were tested by uniaxial tensile testing, it was determined that the m-CNC composites resulted in improvements in the tensile strength and work of fracture without degradation of the elongation of break property when compared to the neat matrix. Overall the findings in this research highlight important considerations for designing CNC/thermoset composites with enhanced dispersion and mechanical performance.
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Gorantla, Sandeep, Alicja Bachmatiuk, Jeonghyun Hwang, Hussain A. Alsalman, Kwak Joon Young, Thomas Seyller, Jürgen Eckert, Michael G. Spencer, and Mark H. Rümmeli. "A universal transfer route for graphene." Royal Society of Chemistry, 2014. https://tud.qucosa.de/id/qucosa%3A36288.
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Often synthetic graphene requires transfer onto an arbitrary substrate prior to use because the substrate it was originally synthesized on is inappropriate for either electrical measurement or characterization. While a variety of routes have been developed they are substrate dependant and often involve the use of harsh treatments. Here we present a facile and cheap route that can be applied to graphene over any substrate. This universal transfer route is based on a wet chemical reaction producing gaseous species which can intercalate between the substrate and the graphene and thus gently delaminate the two.
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Lindmark, Johanna. "Evaluation of Esterification as a Valorization Route for Oxidized Lignin." Thesis, Luleå tekniska universitet, Industriell miljö- och processteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-66306.
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RISE Bioeconomy is working with the biorefinery concept. That is, for the company, to utilize all wood derivatives in effective processes, resulting in unique products. RISE Bioeconomy is investigating the possibilities of producing holocellulose through an oxidative delignification process of wood, using peracetic acid (PAA). The product, high-purity holocellulose, can be used for the production of for example cellulose nanofibers, a product that in recent years have increased in interest. The PAA-delignification process relies on oxidative treatment with peracetic acid, where the lignin is solubilized in water through the formation of carboxylic groups in the lignin, yielding cellulose of very low lignin content and minimal degradation of the cellulose. In addition to the holocellulose, a solution containing water, acetic acid, salts and highly oxidized lignin is obtained. The PAA-delignification has yet only been performed in lab-scale, however, the aim is to scale up the process. There has not yet been any further utilization of the oxidized lignin and it has been proposed that esterification of the carboxylic groups with an alcohol is a possible valorization route. Due to the up-scaling of the PAA-delignification, it is of large interest to find a valorization route for the lignin by-product to fulfill the biorefinery concept. This master thesis focuses on evaluating esterification of an oxidized lignin, with the aim to propose a process suitable for up-scaling. The lab trials for the PAA-delignification of wood yielded limited amounts of lignin and due to difficulties while isolating this lignin, it was not partially characterized until months into the project. Therefore, model compounds were initially used to evaluate the process setup. Compounds with muconic acid type structures are some of the expected products from PAA-delignification of wood and muconic acid was therefore used as a model compound. In addition to this, vanillic acid was used to represent the phenolic lignin compounds. Gas Chromatography/Mass Spectrometry (GC/MS) analysis of the vanillic acid esterification was shown to be a suitable method for analyzing the conversion of this reaction. Due to the difficulties with the analysis of the model compounds, no results regarding the reaction procedures were obtained. As a “proof-of-concept”, a kraft lignin was oxidized, isolated and then esterified. Two different methods of esterification were performed, with and without a molecular sieve. It was assumed that the amount of carboxylic groups would increase after oxidation and decrease after a successful esterification. The amount of carboxylic groups after each process was analyzed with Phosphorus Nuclear Magnetic Resonance (31P-NMR). For the process without molecular sieve, the 31P-NMR analysis indicated that esterification of the lignin had occurred, to a limited extent. This was confirmed by Fourier Transform Infrared Spectrometry (FTIR). The process with molecular sieve showed no indication of esterification of the lignin. The project did prove the concept of esterifying an oxidized lignin and led to several different proposals for further work in the area. Due to the very wide scope of this project and several unexpected obstacles, this project did not fully answer the research questions given.
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Witkowska, Malgorzata Danuta. "Interrogation of the manufacturing route of aluminium AA 1050 used in lithographic application." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/interogation-of-the-manufacturing-route-of-aluminium-aa-1050-used-in-lithographic-application(57658930-cb45-470e-b6ab-626781f1c8a2).html.
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The aluminium AA1050 alloy, known as commercially pure aluminium, contains 99.5% Al, together with Fe and Si as major alloying elements. During fabrication of aluminium substrates for lithographic printing plates in Bridgnorth Aluminium Ltd, the AA 1050 aluminium alloy proceeds through various stages of thermomechanical processing, with the conditions at each processing stage influencing the microstructure of the final coil. Because of its specific gravity, tensile strength, surface performance and coating adhesion behaviour, the AA 1050 aluminium alloy is one of the preferred materials for offset printing, which has been the dominant printing process for years. During manufacturing of the offset plate, the AA 1050 alloy is subjected to alkaline etching, electrograining and anodizing. Reactivity of the material to those chemical and electrochemical processes depends on various alloy properties, the thickness and composition of oxide film over the macroscopic alloy surface, cold work applied and the presence of second phase particles, which influence properties and quality of the final product.During the project, the main objectives were to understand the process in the production of the final product from slab to coil as well as to investigate some microstructural changes during the following stages of the production process and, finally, the performance behaviour of the final product.The set of experiments, including microstructural observation and electrochemical tests, has been developed to investigate the AA 1050 aluminium sheet in accordance with the objective of this study. Four homogenisation trials in the industry environment were performed to enable sample collection from the real production line; also, samples from each processing stage were examined with the special attention paid to those collected during the plant experimental homogenisation trials. It was found that the microstructure of the aluminium changed throughout the different production stages and influences the material response in the alkaline solution used for etching. Furthermore, the conditions of homogenisation (time and temperature) have impact on the properties like the electrochemical behaviour in alkaline and acid solutions, as well as the microstructure of the final aluminium sheet. Differentiation between the behaviour of final gauge samples was possible in terms of characterisation of the second phase particles characterisation (distribution and composition) present in the resultant alloy product.
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Kerkar, Awdhoot Vasant. "Investigation of steric stabilization as a route for colloidal processing of silicon carbide/silicon nitride composites." Case Western Reserve University School of Graduate Studies / OhioLINK, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=case1059055054.
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Li, Xiaoxun Livant Peter D. "Toward a breathable fabric for protection against airborne toxic chemicals, and an olefin-forming cascade reacion en route to 2,2'-BI(glycerol)." Auburn, Ala, 2009. http://hdl.handle.net/10415/1829.
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Abidh, Sarah. "Méthodologie d'ingénierie sensorielle pour la formulation de produits cosmétiques, application au rouge à lèvres." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLA023.
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: Le rouge à lèvres est un produit incontournable du marché des cosmétiques. C’est un produit de formulation complexe et aux fonctionnalités multiples, parmi lesquelles la sensorialité est centrale et dépend principalement des corps gras mis en œuvre. Face à la multiplicité des ingrédients disponibles et aux pratiques de formulation s’appuyant largement sur l’expertise empirique des formulateurs, cette thèse répond à une problématique industrielle de mise en place d’une méthodologie de formulation raisonnée pilotée par la fonctionnalité sensorielle. Mettre en place une telle démarche d’ingénierie sensorielle nécessite d’intégrer la connaissance des liens entre la formulation, la structure et les fonctionnalités du produit. Pour ce faire, nous avons proposé une démarche en sept étapes, s’appuyant sur la réalisation d’une formule simplifiée et réaliste. Ce système a permis de structurer une approche hypothético-déductive concernant le rôle de différentes catégories d’ingrédients sur les propriétés sensorielles du produit. Nous avons ainsi pu montrer que les huiles et les cires ont un rôle majeur sur ces propriétés. Les huiles affectent principalement le glissant, le fondant, l’huileux, la douceur, le collant et la présence sur les lèvres. Les cires, quant à elles, ont une influence sur l’opacité et la quantité de rouge à lèvres déposé. Ce travail s’appuie sur une compréhension approfondie des mécanismes physicochimiques à l’origine de la structure du rouge à lèvres, observée à différentes échelles, et des propriétés résultantes. Enfin, sur deux cas concrets d’ingénierie inverse, nous avons validé cette démarche ainsi que les relations entre les propriétés des ingrédients, la structure et les propriétés mécaniques et sensorielles du rouge à lèvresLipstick is a must-have product of the cosmetics market. It is made from a complex formulation and it has multiple functionalities, among which the sensoriality is central and depends mainly on fats and oils used. Given the multiplicity of available ingredients, formulation practices are largely based on the formulators’ empirical expertise. In this industrial context, this thesis aims at setting up a reasoned formulation methodology driven by the sensory functionality. Implementing such a sensory engineering approach requires integrating knowledge of the relationships between formulation, structure and product functionalities. In order to do this, we proposed a seven-step approach, based on the realization of a simplified and realistic formula. This system allowed to structure a deductive reasoning approach concerning the role of different categories of ingredients in the sensory properties of the product. Thanks to this approach, we have shown that oils and waxes have a major role in these properties. The oils mainly affect the slipperiness, the melting quality, the oiliness, the softness, the stickiness and the presence on the lips. Waxes, on the other hand, have an influence on the opacity and the amount of lipstick deposited. This work is based on a thorough understanding of the physicochemical mechanisms at the origin of the structure of lipsticks, observed at different scales, and of the resulting properties. Finally, we validated this approach, as well as the relationships between the properties of the ingredients, the structure and the mechanical and sensory properties of lipsticks, on two concrete cases of reverse engineering
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Termoss, Hussein. "Préparation de revêtements de nitrure de bore (BN) par voie polymère précéramique : étude des paramètres d'élaboration : caractérisations physico-chimiques." Phd thesis, Université Claude Bernard - Lyon I, 2009. http://tel.archives-ouvertes.fr/tel-00699530.
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L'objectif de cette thèse est de réaliser des revêtements de nitrure de bore sur différents types de substrats comme le graphite, le quartz, le pyrex, en allant jusqu'aux métaux et en particulier le titane. Le choix de la voie PDCs s'avère intéressant grâce à la maîtrise du précurseur de départ au niveau atomique d'une part et à la facilité du procédé de dépôt, d'autre part. Nos objectifs étaient d'étudier la faisabilité de réaliser des revêtements BN sur différents types de substrat en utilisant un traitement thermique résistif et de mettre en place un dispositif qui nous permette de pyrolyser les films polymériques sur métaux sans dommage pour le substrat, en vue de leur protection contre l'oxydation ou d'autres applications mécaniques. Dans ce sens, nous avons démontré la possibilité d'utiliser un traitement thermique alternatif par lampe halogène émettant dans l'infra-rouge pour densifier les revêtement BN déposer sur substrats métalliques.
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Novaes, Karla Teixeira Farias de. "Síntese de derivados do megazol, com potencial atividade tripanosomicida." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/9/9135/tde-18122017-100516/.
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Este projeto visa à obtenção do megazol e de seus derivados, que possam ser comparados quanto a sua atividade biológica, no intuito de produzir um análogo mais potente e menos tóxico. O megazol, estrutura de interesse do trabalho proposto, foi sintetizado inicialmente em 1968 por Asato e Berkelhammer utilizando o 5-nitroirnidazol como material de partida. Nos anos 80, pesquisadores brasileiros da Fundação Instituto Oswaldo Cruz e do Centro René Rachou, devido a grande incidência da doença de Chagas no Brasil, relacionaram um grande número de substâncias químicas até então indicadas como ativas contra o Trypanosoma cruzi. Dentre estas substâncias, o megazol foi o que apresentou um grande interesse, pois em testes \"in vivo\" em ratos mostrou um efeito curativo significativo, em dose única. A partir daí, estudos desta molécula e análogos tornaram-se imprescindíveis, no intuito de determinar o mecanismo de ação desta estrutura e seus potenciais efeitos tóxicos. A rota de síntese utilizada como enfoque foi a descrita por Albuquerque em 1995 e otimizada por Moretto em 2001. No presente trabalho, obtiveram-se seis derivados do megazol a partir da modificação da função amina ligada ao anel 1,3,4 tiadiazólico. Uma destas modificações foi realizada pela sua reação com cloretos ou anidridos de ácidos, outra foi a partir da diazotação e substituição pelo átomo de cloro, e a substituição do cloro pelo metoxi. Os derivados obtidos foram testados em culturas de células Vero infectadas com Trypanosoma cruzi e analisados em relação ao índice de infecção do parasita. Até o presente momento três compostos mostraram-se tão ativos quanto ao megazol. Os dados obtidos serão empregados para ampliar não só O estudo de novos fármacos anti-chagásicos, mas também para uma melhor compreensão dos processos químicos envolvidos na síntese de intermediários do tipo 5-nitroirnidazóis.This project aims the synthesis of megazol and some derivatives, with more powerful and better biological activity. Megazol, the chemical structure of interest in this work, was synthesized initially in 1968 for Asato and Berkelhammer using 5-nitroimidazol as a starting material. In years 80, Brazilian researchers of the Oswaldo Cruz Institute Foundation and René Rachou Center, had related a great number of chemical substances active against the Trypanosoma cruzi, illness very common in Brazil One of these substances, the megazol, presented a great interest, as the tests \"in vivo\" in rats showed significant curative effect, in only one dose. As a result of this biological test, more accurate studies of the analogous molecules had become essential, in intention to determine the mechanism of action of this structure and its potential toxic effect. The synthesis route was that described by Albuquerque in 1995, and optimized by Moretto in 2001. In the present work, six derivatives of megazol resulted from the chemical modification from the amine of 1,3,4 thiadiazolic ring. One of these modifications was made by the reaction with anhydrides, chlorides or acids; another one was from the diazotation and substitution by the chlorine atom, and the substitution of chlorine by the methoxy group. The gotten derivatives had been tested in cultures of Vero cells infected with Trypanosoma cruzi and analyzed in relation to the parasite infection index. Until now three compounds presented a higher activity than megazol. The gotten data will be used not only for extend the study of new drugs against the Trypanosoma cruzi, but also for better understanding of the involved chemical processes in the 5-nitroimidazoles intermediate synthesis.
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Pechamat, Laurent. "Impacts de l'oxygène sur les évolutions chimiques et sensorielles du vin rouge." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0355/document.
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L’impact de l’oxygène a été suivi pendant 4 mois pour 3 vins de Merlot d’IPT 61, 63 et 76. Le vin d’IPT 63 était enrichi par une fraction d’ellagitannins de bois de chêne. Les vins ont été ajustés à pH 3, pH 3,5 et pH 4. Pour chaque pH, des doses de 0, 2, 8 et 20 mg/L d’oxygène ont été fournies à l’aide d’oxygène pur, puis des analyses mensuelles ont permis de suivre les évolutions chimiques et sensorielles des vins afin d’apprécier les impacts liés à l’oxygène.Les résultats montrent pour tous les vins, que la consommation de l’oxygène augmente de 2 à 4 fois plus lorsque l’on passe de pH 3 à pH 4. La présence d’ellagitannins dans le vin favorise la consommation d’oxygène, ainsi qu’en solutions modèles hydro-alcooliques de fractions phénoliques. Les teneurs en tannins totaux sont globalement stables. Les polymérisations analysées par la méthode DMACH se produisent majoritairement à pH 3 et pH 3,5 pour le vin d’IPT 61, alors que les différences liées à l’oxygène sont moins fortes sur le vin d’IPT 76. Pour le vin d’IPT 63 + ellagitannins, les polymérisations sont favorisées à pH 3. Les teneurs en anthocyanes totales et moléculaires montrent généralement des diminutions en fonction du temps, de l’oxygène ainsi que de l’acidité. Pour le vin d’IPT 76 et d’IPT 63 + ellagitannins, les anthocyanes se polymérisent davantage aux tannins polymères en présence d’oxygène, et à pH plus acide. 13 pyranoanthocyanes ont pu être identifiées et quantifiées, dont deux molécules de pyranomalvidine-di-(épi)catéchine quantifiées pour la première fois dans des vins rouges secs qui peuvent être considérées comme des marqueurs en lien avec l'apport en oxygène subi par le vin. Les analyses sensorielles réalisées sur le vin d’IPT 76 en fonction des pH montrent que l’amertume est plus forte à pH 4, et pH 3,5 dans une moindre mesure. Cette tendance se retrouve aussi sur la perception d’oxydation.Pour les deux autres vins, d’IPT 61 et d’IPT 63 enrichi par une fraction d’ellagitannins, l’intensité du fruité diminue globalement avec les doses d’oxygène, tandis que le caractère oxydé est bien corrélée avec les doses croissantes d’oxygène, ainsi que l’amertume dans une moindre mesureThe impact of oxygen has been followed-up during 4 months for 3 Merlot red wines of TPI 61, 63 anf 76. The wine of TPI 63 was supplied by a fraction of ellagitannin from oak wood. Wines have been adjusted at pH 3, pH 3.5 and pH 4. For each pH, quantities of 0, 2, 8 and 20 mg/L of pure oxygen have been added. Then, anlyses have been performed each month to follow the wine chemical and sensory evolutions in order to determine the impact of oxygen.For all wines, the results show that oxygen consumption is 2 to 4 fold higher from pH 3 to pH 4. The presence of ellagitannin in wine favors oxygen consumption, as well as in wine model solutions with phenolic fractions. Total tannin contents remain quite constant. Polymerisations analysed by DMACH index occur mainly at pH 3 and pH 3.5 for the wine of TPI 61, while the differences related to oxygen are less important in the wine of TPI 76. For the wine of TPI 63 + ellagitannins, polymerisations are favored at pH 3. Total and molecular anthocyanins contents generally show a decrease according to time, oxygen and acidity. For the wines of TPI 76 and TPI 63 + ellagitannins, the anthocyanins polymerise more to polymers of tannins with oxygen and acidity. 13 pyranoanthocyanins have been identified et quantified. Among them, two molecules of pyranomalvidin-di-(epi)catechin quantified for the first time in a dry red wine. They can be considerated as marker related to oxygen amount consumed by wine. Sensory analyses realized on wine of TPI 76 according to pH show that bitterness is higher at pH 4, and pH 3.5 in a lesser extent. There is the same trend with the oxidation perception.For the two other wines, of TPI 61 and 63 with ellagitannin fraction, fruity intensity globally decreases with oxygen quantities, while the oxidized parameter is well related to increasing oxygen amounts, as wella s bitterness in a lesser extent
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Damigos, Emmanuel. "Déshydratation de la boehmite en alumine de transition. Étude thermodynamique et structurale." Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 1987. http://tel.archives-ouvertes.fr/tel-00845575.
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L'influence de la température et de la pression de vapeur d'eau sur la déshydratation de la boéhmite et sa transformation en alumine de transition a été étudiée. La boéhmite n'est pas un monohydrate d'alumine mais un oxyhydroxide d'aluminium dont la maille contient deux ions aluminium en positions cationiques trivalentes, deux ions oxygènes en positions anioniques divalentes et deux hydroxyles en positions anioniques monovalentes. Lors d'une augmentation modérée de la température (inférieure à 300°C), la boéhmite subit une déshydratation partielle qui conduit à un composé sous stœchiométrique en hydroxyles et qui est provoquée par l'association des hydroxyles deux par deux qui s'éliminent sous forme d'eau en laissant dans le réseau une position anionique monovalente vide et une autre occupée par un ion oxygène (en substitution de l'hydroxyle). C'est une réaction non renversable avec la diminution de la température. La déshydratation de la boéhmite en alumine de transition est le résultats de la succession et superposition partielle de trois équilibres : la déshydratation partielle de la boéhmite sans changement de phase, la transformation du réseau de la boéhmite (au-delà d'un certain degré de déshydratation) en réseau d'alumine de transition (spinelle) partiellement hydratée, la déshydratation de l'alumine de transition qui se poursuit jusqu'à 900°C ou plus. Les trois réactions sont endothermiques et leurs chaleurs de réaction ont été calculées. Il existe un domaine de température et de pression de vapeur d'eau où la boéhmite et l'alumine de transition coexistent. La température de déshydratation et de transformation, en alumine de transition de la boéhmite augmente avec la pression de vapeur d'eau appliquée. A une température donnée l'alumine de transition contient un plus grand nombre d'hydroxyles lorsqu'elle est formée sous une pression de vapeur d'eau supérieure.
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Gmira, Ahmed. "Etude structurale et thermodynamique d'hydrates modèle du ciment." Phd thesis, Université d'Orléans, 2003. http://tel.archives-ouvertes.fr/tel-00006001.
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Les hydrates de ciment (C-S-H) obtenus par dissolution/précipitation du ciment anhydre, constituent la matrice donnant au matériau ses propriétés mécaniques et sont structurellement analogues de la tobermorite, un calcio-silicate lamellaire naturel. La compréhension de la cohésion du ciment passe donc par la compréhension de la cohésion entre feuillets tobermoritiques. La structure lamellaire de différents échantillons de CSH tobermoritiques synthétisés par "chimie douce" a été mise en évidence ; les échantillons avec un rapport Ca/Si égal à 0.9 étant particulièrement bien cristallisés. L'étude du processus de déshydratation pour ces échantillons a permis d'identifier 3 phases et de montrer la similarité de comportement vis à vis du "vrai" ciment. Nous montrons que la transition 14-11 Å est irréversible. Se pose alors la question du rôle de l'eau interfoliaire dans la cohésion du matériau en relation avec les deux structures possibles décrites dans la littérature pour la tobermorite naturelle 11 Å : la proposition d'Hamid (1981) décrivant un ensemble de feuillets indépendants et celle de Merlino et al (1999) décrivant des feuillets chimiquement liés. La confrontation entre résultats expérimentaux (29Si-RMN et spectroscopie infra-rouge) et numériques (calculs ab-initio et minimisation d'énergie) indique que la structure d'Hamid est un modèle acceptable pour les C-S-H tobermoritiques. La nature des liaisons inter-feuillets est d'origine coulombienne au sens de l'énergie de réseau des solides ioniques.
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Bergeot, Vincent. "Polymérisation par ouverture de cycle de l' e-caprolactone dans le dioxyde de carbone supercritique." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2002. http://tel.archives-ouvertes.fr/tel-00003499.
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Cette étude décrit la mise au point de la synthèse de poly( -caprolactone) dans le dioxyde de carbone supercritique (scCO2). Utilisant des isopropanolates d'aluminium, d'yttrium et de lanthane comme amorceurs, la poly( -caprolactone) a été synthétisée dans le scCO2. Les rendements obtenus varient énormément, selon les amorceurs et les conditions de polymérisation. Afin de mieux comprendre le mécanisme mis en jeu, une étude plus complète portant sur l'état thermodynamique du système et les interactions microscopiques a été initiée. Des mesures de point trouble pour des mélanges (monomère / CO2, polymère / CO2, monomère / polymère / CO2) ont été effectuées à l'aide d'une cellule PVT équipée de deux fenêtres en saphirs, conduisant à l'établissement des diagrammes de phase pour ces systèmes. De plus, les mélanges amorceurs/CO2 ont été étudiés par spectroscopie infra-rouge dans le scCO2 et différents types d'interactions entre l'alcoolate de métal et le CO2 ont été mis en évidence.
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Veschambre, Sophie. "Caractérisation et quantification des Eléments Traces Métalliques dans les dépôts et les particules atmosphériques de la vallée d'Aspe - Mise en place d'indicateurs de la Qualité de l'Air." Phd thesis, Université de Pau et des Pays de l'Adour, 2006. http://tel.archives-ouvertes.fr/tel-00118082.
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L'étude des apports atmosphériques des éléments traces métalliques (ETM) dans la vallée d'Aspe (Pyrénées Atlantiques) a un double objectif : (1) établir un état de référence des contaminants métalliques pour le suivi des émissions du trafic routier liés à l'ouverture du tunnel du Somport et, (2) évaluer les sources et les conditions climatologiques qui contribuent aux apports des ETM dans la vallée d'Aspe. La détermination des ETM (Al, Na, Mg, K, V, Mn, Cr, Zn, Cu, Rb, Cd, Sn, Sb, Ba, Ce, Pb et U) et des rapports isotopiques du plomb (208Pb/206Pb, 206Pb/207Pb et 208Pb/207Pb) dans les récepteurs atmosphériques (neiges fraîches, dépôts humides, particules atmosphériques et lichens) a permis de mettre en place des indicateurs de la qualité de l'air. La quantification des ETM a nécessité la mise en oeuvre de protocoles de prélèvements et d'analyses ultra-traces. Les différents récepteurs atmosphériques étudiés permettent d'intégrer une échelle temporelle journalière à pluriannuelle et un gradient spatial dans l'axe Nord-sud de la vallée et en fonction de l'altitude.La vallée d'Aspe présente un niveau de contamination spécifique des zones éloignées des émissions anthropiques et les contaminants métalliques identifiés sont le Cd, Sb, Zn, Cu, Pb et Sn. Dans sa partie basse, les indicateurs de la qualité de l'air présentent une contribution des contaminants (i) liée aux émissions locales des combustions domestiques, à la pratique saisonnière de l'écobuage et au trafic routier, et (ii) aux sources anthropiques régionales de l'incinération des déchets ménagers, de l'industries métallurgique et des centres urbains. Dans sa partie haute, la vallée est soumise significativement, d'une part, à l'érosion éolienne et, d'autre part, à la contribution des sources du transport à grande échelle de l'hémisphère Nord. La caractérisation des ETM et des rapports isotopiques du plomb dans le tunnel du Somport indique (i) que le trafic routier émet significativement du Cu, Sb, Zn et Ba et (ii) bien que Pb présente de faibles émissions sa composition isotopique montre une source faiblement radiogénique du trafic routier. Toutefois, la faible circulation des véhicules dans la vallée d'Aspe ne permet pas de mettre évidence une contamination significative provenant des émissions du trafic routier.
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Petit, Johan. "Monocristaux dopés ytterbium et matériaux assemblés pour lasers de fortes puissances." Phd thesis, Paris 6, 2006. http://pastel.archives-ouvertes.fr/pastel-00001720.
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Les lasers solides dopés terres rares ont certains avantages: ils sont compacts, possèdent un fort rendement et leur faisceau est de bonne qualité. Le principal problème limitant la puissance est la production de chaleur inhérente au processus laser. Cette thèse comporte un premier volet consacré à l'étude de nouveaux matériaux à forte résistance à la puissance de pompage: GdVO4 :Yb et CaGdAlO4 :Yb en particulier. Des émissions laser quasiathermiques et des impulsions ultra-brèves ont été obtenues dans ce dernier. Dans un second volet, une nouvelle méthode d'assemblage par voie sol-gel a été étudiée pour créer des sources composites permettant une dissipation efficace de la chaleur. Avec cette technique, les homo-assemblages (matériaux de même nature chimique) présentent les mêmes capacités de résistance que ceux obtenus par la méthode de soudage par diffusion. Les hétéroassemblages (deux matériaux différents) sont difficiles à obtenir par diffusion mais, avec une interface issue du procédé sol-gel, ils ont résisté jusqu'à 200°C et 15 W de pompage. Les pertes lasers à l'interface sont négligeables et la température dans le matériau est abaissée de près de 40%.
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Gascoin, Nicolas. "Etude multi-physique des phénomènes réactifs dans les technologies propulsives aérospatiales." Habilitation à diriger des recherches, Université d'Orléans, 2012. http://tel.archives-ouvertes.fr/tel-00705540.
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Le développement des technologies propulsives requiert la maîtrise de la régulation de poussée et parfois du refroidissement (propulsion hybride et hypersonique). Cet aspect de contrôle ne peut être abordé qu'après avoir développé une compréhension détaillée des phénomènes couplés mis en jeu (thermique, fluidique, cinétique chimique). La priorité est de proposer des moyens qui soient complémentaires entre eux (bancs d'essais, moyens de mesure, outils numériques) afin d'apporter de nouvelles connaissances scientifiques qui soient transposables à l'industrie. L'ensemble du travail mené dans cette optique est présenté ici en détaillant les applications visées. Ensuite, les similitudes identifiées entre celles-ci (couplage entre pyrolyse du carburant et combustion des produits, pilotage des phénomènes par la chimie) permettent de proposer une démarche globale de recherche portée par l'étude de certains verrous. Les connaissances ainsi développées sont assez larges pour être appliquées à d'autres systèmes, comme l'endommagement au feu des réservoirs de carburant en composite.
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Marchand, Nicolas. "Etude de la composante organique de l'aérosol atmosphérique : cas de deux vallées alpines (Chamonix et Maurienne) et développement analytique." Phd thesis, Chambéry, 2003. http://tel.archives-ouvertes.fr/tel-00003533.
Full textAbstract:
Les particules atmosphériques appelées aérosols jouent un rôle potentiellement important sur le bilan radiatif terrestre et sur celui des photo-oxydants comme l'ozone troposphérique. Lorsque leurs tailles est inférieures à 2,5µm, ils peuvent présenter un danger pour la santé publique. La connaissance de la composition physico-chimique de ces aérosols est encore très insuffisante en ce qui concerne sa composante organique, appelée MOP (Matière Organique Particulaire). De même, les mécanismes de formation de la MOP demeurent encore mal connus. Ce travail s'inscrit donc dans la problématique générale d'une meilleure connaissance de la composante organique de l'aérosol.Dans le cadre du programme PO.V.A. (POllution des Vallées Alpines), articulé autour de la réouverture du tunnel sous le Mont Blanc et dont les principaux objectifs sont de mieux appréhender les phénomènes de pollution atmosphérique et les mécanismes dispersifs propres aux systèmes montagneux, des aérosols ont été collectés dans les vallées de Chamonix et de Maurienne au cours de deux campagnes intensives de mesures. Elles se sont déroulées au cours de l'été 2000 et de l'hiver 2001.
Après la présentation des problématiques (chapitre I) et des méthodes utilisées (chapitre II), les résultats de deux types d'analyse sont présentés (chapitre III). Le premier type se focalise sur une classe de composés : Les Hydrocarbures Aromatiques Polycycliques (HAP). L'intérêt de l'étude des HAP est double. D'une part ils sont, pour la plupart, considérés comme cancérogènes et mutagènes. D'autre part, ils sont émis quasi exclusivement par les combustions (dérivés du pétrole et biomasse) et leur étude permet de mieux appréhender les influences relatives des différentes sources anthropiques. Le second type d'analyses, plus exploratoire, consiste à réaliser une spéciation quantitative, la plus exhaustive possible, de la fraction organique et d'établir des relations entre la composition chimique, les sources, les saisons et les paramètres météorologiques. Des composés comme le guaiacol, la vanillin, le syringol (...) (émis par les feux de bois) ou comme la nopinone (composé secondaire) ont ainsi pu être quantifiés.
Les résultats obtenus ont permis de mettre en évidence :
- un apport anthropique important dans les deux vallées, pour les deux saisons et plus particulièrement en hiver où des concentrations en HAP très élevées et représentatives de grands centres urbains ont été observées (maximum 150 ng.m-3) ;
- des niveaux de concentrations en composés anthropiques primaires systématiquement plus importants dans la vallée de Chamonix, malgré l'absence du trafic des poids lourds;
- l'influence des conditions météorologiques et de la géomorphologie des vallées dans la dispersion des polluants ;
- une contribution très marquée des combustions de bois (chauffage domestique) dans la vallée de Chamonix l'hiver.
La spéciation quantitative de la MOP (chapitre III) a permis de déterminer globalement entre 10 et 74% du carbone organique. La fraction identifiée dépend de la saison considérée et est plus élevée l'hiver (34-74%) lorsque l'apport des sources primaires anthropiques est prépondérant. Cette variabilité saisonnière a mis en évidence les lacunes du protocole analytique utilisé, qui ne permet pas de quantifier la plupart des composés oxygénés polyfonctionnels et donc les composés constitutifs l'aérosol organique secondaire. Une méthode alternative de prélèvement et d'analyse de ces composés a été développée (Chapitre IV).
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Waked, Antoine. "Caractérisation des aérosols organiques à Beyrouth, Liban." Electronic Thesis or Diss., Paris Est, 2012. http://theses.univ-paris-est.fr/intranet/2012/TH2012PEST1169_complete.pdf.
Full textAbstract:
La connaissance des sources primaires (combustion des énergies fossiles, combustion de la biomasse, éruptions des volcans, etc.) et secondaires (oxydation des composés organiques volatils (COV) suivie de la condensation formant des composés organiques particulaires) de l'aérosol organique ainsi que la caractérisation et la quantification de sa composition chimique restent un défit majeur, en particulier dans la région du Moyen Orient où les études de caractérisation de l'aérosol organique n'existent pas jusqu'à présent. Le Liban, un pays du Moyen Orient qui se situe au bord du bassin méditerranéen, représente un bon exemple pour la caractérisation des aérosols organiques dans cette région. Les travaux menés durant cette thèse s'inscrivent dans un objectif de l'étude de la qualité de l'air à Beyrouth (la capitale du Liban) en se concentrant plus spécifiquement sur les aérosols organiques. Tout d'abord, cette thèse a permis le développement d'un inventaire des émissions pour les gaz et les particules pour le Liban avec une résolution spatiale de 5 km x 5 km et pour la capitale Beyrouth avec une résolution spatiale de 1 km x 1 km. Les résultats obtenus indiquent que le transport routier est la source majoritaire responsable des émissions de monoxyde de carbone (CO), d'oxydes d'azote (NOX) et de composés organiques volatils non méthaniques (COVNM), tandis que les industries et les centrales électriques sont les principaux émetteurs des émissions de dioxyde de souffre (SO2) et des particules primaires. Ensuite, afin de caractériser les concentrations des polluants et plus spécialement la fraction organique des particules, deux campagnes de mesures intensives de 15 jours chacune ont été menées sur un site semi-urbain situé dans la banlieue de Beyrouth. Une première campagne estivale s'est déroulée en juillet 2011 et une deuxième campagne hivernale en février 2012. Ces campagnes, qui s'inscrivent dans le cadre du projet ECOCEM (Emission and Chemistry of Organic Carbon in East Mediterranean Beirut) ont permis une spéciation moléculaire et une catégorisation des sources en été et en hiver de l'aérosol organique au site de mesures où les campagnes ont été menées. En été, les précurseurs biogéniques tels que les monoterpènes et les sesquiterpènes qui aboutissent à la formation des aérosols organiques secondaires biogéniques sont la principale source à cause de l'insolation intensive et les températures élevées qui favorisent les émissions et les réactions de photo-oxydations. En hiver, la combustion de la biomasse est la principale source en raison de la combustion du bois dans le secteur résidentiel pour le chauffage. Enfin, les concentrations ambiantes des polluants à Beyrouth ont été simulées durant le mois de juillet 2011 à partir de données de l'inventaire des émissions développé dans le cadre de cette thèse en utilisant le modèle de chimie-transport Polyphemus/Polair3D. Les concentrations de polluants simulées avec le modèle ont été comparées aux concentrations mesurées durant la campagne estivale afin d'évaluer le modèle. Les résultats obtenus révèlent que le modèle est capable de simuler de manière satisfaisante les concentrations d'ozone (O3), de NOX et la plupart des composés présents dans les particules fines. Les différences entre le modèle et les mesures peuvent résulter des incertitudes dans les données d'entrée qui ont une très grande influence sur les sorties du modèle. Pour cela, une réduction des incertitudes engendrées par les données d'entrée et plus spécifiquement celles liées à l'inventaire des émissions est nécessaire. Par ailleurs, des mesures chimiques sur plusieurs sites sont aussi nécessaires dans le futur afin de mieux évaluer les simulations des concentrations de polluantsThe chemical composition of PM2.5 includes both organic and inorganic compounds. Organic compounds, which constitute a significant fraction of the PM2.5 mass, can be emitted directly as primary aerosol from sources such as fossil-fuel combustion, biomass burning, and natural biogenic emissions, or formed in the atmosphere via chemical reactions leading to secondary organic aerosol (SOA) formation. SOA, which account for 20 – 80 % of total organic aerosol, are currently a major source of uncertainty in air quality modeling. The identification and quantification of the chemical composition of the organic fraction of PM2.5 and its source apportionment are of great interest, especially in the Middle East region where data on organic aerosols are currently lacking. Lebanon, a small developing country in the Middle East region located on the eastern shore of the Mediterranean basin represents a good example for characterizing organic aerosols in this region. To address this issue, the air quality in Beirut (the capital city of Lebanon) was investigated with a focus on organic aerosols. First, an air pollutant emission inventory was developed for Lebanon with a spatial resolution of 5 km x 5 km and for Beirut with a spatial resolution of 1 km x 1 km. The results obtained show that the road transport sector is the major contributor to carbon monoxide (CO), nitrogen oxides (NOx) and non-methane volatile organic compounds (VOC) emissions, whereas fossil fuel-fired power plants and large industrial plants are the major contributors to sulfur dioxide (SO2) and primary particulate matter (PM) emissions. Then, two intensive 15-day measurement campaigns were conducted at a semi-urban site located in a Beirut suburb to characterize air pollutant concentrations. The first measurement campaign took place in July 2011 and the second in February 2012. Measurements included PM2.5, organic carbon (OC) and elemental carbon (EC) mass concentrations as well as a molecular characterization of organic aerosols. Using these data, a source apportionment of organic aerosols was conducted for summer and winter. In summer, biogenic precursors such as monoterpenes and sesquiterpenes were the major source of OC due to intensive solar radiation and high ambient temperatures that promote biogenic VOC emissions and photo-oxidation reactions. In winter, biomass burning was the major source of organic aerosols because of the intensive use of wood burning for heating. Finally, air pollutant concentrations in Beirut were simulated for July 2011 with the Polyphemus/Polair3D chemical-transport model (CTM). The emission inventory mentioned above was used as input to the model. Meteorological simulations were conducted with the Weather Research and Forecasting model (WRF) using different configurations and the configuration leading to the best agreement with the observations was used to drive the air quality simulations. The simulated air pollutant concentrations were compared to the measured concentrations collected during the summer measurement campaign. The results show that the model reproduces satisfactorily the concentrations of ozone (O3), nitrogen dioxide (NO2), carbon monoxide (CO), and the major components of PM2.5. The differences obtained between the modeled and measured air pollutants concentrations are due in part to uncertainties in input data. Future studies should address the reduction of uncertainties such as those of the emission inventory. In addition, measurement campaigns involving several sites are needed to better characterize air pollution in Beirut and provide a more complete database to evaluate simulated air pollutant concentrations