Dissertationen zum Thema „Catalyse or/silicium“
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Ducos, Paul. „Synthèse de nouveaux acides de Lewis silylés pour la catalyse organique“. Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0439/document.
Der volle Inhalt der QuelleIn contrast with carbocations which existence was unambiguously proven in the early 60’s, silylium ions (R3Si+) have remained for a long time elusive species and putative intermediates in many transformations involving organosilicon compounds. It was only in 2002 that the first structural proof (X-ray crystallography) dispelled any doubt about the existence of tricoordinated silicon cations in the condensed phase. Silylium ions are extremely electrophilic, able to coordinate to weak Lewis bases including solvent molecules such as benzene. The possibility to tame this acidity through an appropriate labile coordination even widens the scope of applications of these reactive species and allows their use as catalysts for organic synthesis. The aim of this thesis was to synthesize new stabilized silyliums ions and rationalize the impact of this stabilization onto the reactivity. In a first part, we focused on the use of hindered nitrogen derivatives to stabilize the silicon center. The nature and the strength of the interaction were assessed by NMR spectroscopy and theoretical calculations. In a second part, the introduction of chirality onto the silicon cation has been studied. A series of binaphtyl templated silyliums bearing an intramolecular Lewis base were synthesized. According to the strength of the stabilization, the chiral information present on the silicon can be persistent and used for asymmetric catalysis
Pascaretti, Mathieu. „Catalyse synergique οr/silicium par activatiοn d’οrganοsilanes et d’hydrοsilanes au mοyen de cοmplexes d’Au(Ι) : dévelοppements et applicatiοns“. Electronic Thesis or Diss., Normandie, 2024. http://www.theses.fr/2024NORMLH01.
Der volle Inhalt der QuelleSince the early 2000s, gold catalysis has developed particularly well in organic chemistry, offering new highly efficient synthetic methods, generally under very mild conditions. These advances have also led to abundant use in glycoscience, but despite important breakthroughs, the application of gold catalysis in glycochemistry is typically limited to conventional modes of sugar donor activation, in which the gold complex remains strictly confined to the role of a σ- or π-Lewis acid. The research work presented through this manuscript tends to introduce a new paradigm in gold-catalysed glycosylation reactions, by developing catalytic alkynylation reactions in which the gold complex should overcome the intrinsic difficulties of these couplings by contributing to the simultaneous activation of the sugar donor and the alkyne aglycone, based on an original gold/silicon synergistic catalysis strategy. The ideal combination of gold catalyst and counterion was sought (L and X) to achieve optimum catalytic reactivity and stereochemical control both for the alkynylation reaction of simple saturated glycosides and for the alkynylation of glycals. The discovery of a major impact of a hitherto unexploited Au(I) complex counterion in synergistic gold/silicon catalysis associated with a strongly deactivating phosphine has made it possible to extend the field of application of synergistic gold/silicon catalysis beyond the alkynylation of glycosides
Leroux, Denis. „Polystyrène sulfoné supporté sur silice poreuse : greffage et activité en catalyse acide“. Lyon 1, 1994. http://www.theses.fr/1994LYO10290.
Der volle Inhalt der QuelleBrouty, Marie-Sophie. „Recherche de nouveaux catalyseurs acides supportés de type polyphénylsilsesquioxanes chlorés sulfonés greffés sur silices“. Lyon 1, 1995. http://www.theses.fr/1995LYO10135.
Der volle Inhalt der QuelleLecomte, Sandrine. „Préparation des diénolates de potassium à partir des diénoxysilanes et du tertiobutylate de potassium : Etude de leur condensation régiosélective avec les dérivés carbonylées. Mise au point d'une méthode de prénylation“. Rouen, 1997. http://www.theses.fr/1997ROUES072.
Der volle Inhalt der QuelleMadani, Behrang. „Synthèse de Fischer-Tropsch sur catalyseur à base de cobalt supporté sur carbure de Silicium“. Université Louis Pasteur (Strasbourg) (1971-2008), 2005. https://publication-theses.unistra.fr/public/theses_doctorat/2005/MADANI_Behrang_2005.pdf.
Der volle Inhalt der QuelleThe Fischer-Tropsch synthesis (FTS) leads to various products, mainly alkanes as well as olefins and alcohols, starting with precise mixture of CO and H2. Currently, natural gas is recovered as a by-product of oil extraction and directly burnt, which leads a non negligible economic loss as well as an atmospheric pollution due to the production of CO2. The reaction of FTS is one of the ways permitting valorisation of natural gas after its transformation in gas of synthesis (mixture of CO and H2). The SFT reaction is exothermique and requires fast evacuation of heat from the catalytic sites in order to avoid the problem of hot spots formation and subsequent cracking of formed products. The supports used traditionally for the FTS are insulating supports, such as alumina and silica, which does not permit a good evacuation of heat. In this work, we replaced the insulating support by a conducting support based on SiC, which permits a better homogenisation of the temperature in the catalytic bed. In this study, different reaction parameters- the Co content, the total pressure and contact time, have been optimized in order to obtain the best activity, selectivity and stability of the catalysts. We also studied the influence of the morphology of the support on the catalyst performance. Among the different shapes of support based on SiC (grain, extrudes and foam), the support as foam seems to have the best performance. We finalised the procedures of regeneration of the catalyst as well as the doping by molybdenum. The thus obtained catalysts present the best activity and selectivity
De, Tymowski Benoît. „Synthèse de Fischer Tropsch sur support conducteur à base de carbure de silicium“. Phd thesis, Université de Strasbourg, 2012. http://tel.archives-ouvertes.fr/tel-00855282.
Der volle Inhalt der QuelleGarcia, Cervantes Gabriela. „Préparation et caractérisation de catalyseurs palladium sur supports thermoconducteurs (Si3N4, SiC, Cdiamant) : performances en catalyse d'hydrogénation du butadiène-1,3 et/ou d'oxydation totale du méthane“. Lyon 1, 2004. http://www.theses.fr/2004LYO10074.
Der volle Inhalt der QuelleTymowski, Benoît de. „Fischer Tropsch synthesis on conductive silicon carbide based support“. Thesis, Strasbourg, 2012. http://www.theses.fr/2012STRAF019/document.
Der volle Inhalt der QuelleThe Fischer-Tropsch synthesis (FTS) allows the transformation of a mixture of synthesis gas, i.e. H2 and CO, into valuable liquid hydrocarbons. The catalysts generally used in FTS are based on iron or cobalt supported on alumina or silica. ln the present work, silicon carbide (SiC) has been proposed as a replacement media to traditional supports. The results obtained indicate that the mesoporous SiC containing cobalt catalyst exhibits a good FTS activity and an extremely high selectivity towards liquid hydrocarbons compared to other FTS catalysts supported on alumina or silica. The FTS activity on the Co/SiC catalyst can be improved by changing the impregnation solvent or by promoting the cobalt phase with trace amount of noble metal. The doping of the SiC support with Ti02 phase also significantly improves the FTS activity keeping a similar high selectivity thanks to the formation of small cobalt particles in contact with the Ti02 phase
A, Ahad Hadad Caroline. „Valorisation de pentoses via la synthèse de glycodendrimères“. Reims, 2008. http://theses.univ-reims.fr/exl-doc/GED00000979.pdf.
Der volle Inhalt der QuelleWith the aim of developing renewable ressources from the region of Champagne-Ardenne, we synthesized glycodendrimers, starting from two pentoses (D-xylose and L-arabinose), usable in micellar reactions or like artificial receptors in biomedical field. The first part of this memory relates to the synthesis of nitrogen-based glycodendrimers starting from PAMAMs (PolyAMidoAMines) or PPIs (PolyPropylene Imines) having both the functions amines on the surface. By reaction of condensation between these functions and the pentonolactones, resulting from the two pentoses, we succeeded in obtaining glycodendrimers of first generation. However optimization with the higher generations remains to be developed. Then, in a second part, we wanted to obtain silicon glycodendrimers starting from three kinds of reaction: hydrosilylation, silylation and click chemistry. No convincing results were obtained starting from the reactions of hydrosilylation some either catalyst used and some length of the chain. On the other hand, small molecules and dendrimers of first generation were obtained by a sequence “hydrosilylation/condensation” and by reaction of silylation. Glycodendrimers of generation 1 to 3 were obtained by click chemistry but the method of purification remains to be developed. Lastly, the third part appeared much more encouraging because we succeeded in obtaining the phosphorated first glycodendrimers, starting from a derivative of D-xylose, of generations 1 to 3 by reaction of substitution with quantitative yields. A simple method of purification by successive precipitations was also developed as well as the deprotection of the acetyls groups
Berthet, Agnès. „Propriétés du palladium déposé par jet atomique et par pulvérisation plasma sur des supports réfractaires (SiC et Si3N4) : texture, structure et réactivité en catalyse“. Lyon 1, 1999. http://www.theses.fr/1999LYO10156.
Der volle Inhalt der QuelleZidelmal, Nacim. „SILIPOLYSALEN : étude du greffage par polymérisation contrôlée de complexes de salen sur silicium pour une application en catalyse asymétrique hétérogène“. Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS058.
Der volle Inhalt der QuelleChiral metal complexes of salen type are known for their efficient catalytic activity leading to the preparation of enantioselective enriched synthons. In accordance with the concept of green chemistry, one of the main challenge is to establish a procedure for the recovery and reuse of these catalysts. In this context, the objective of this work is to functionalize the silicon surface by grafting these catalysts by controlled polymerization especially by Atom Transfer Radical Polymerization (ATRP) to facilitate their recovery and reuse.Thus, styrene copolymers containing 5 to 50 mol % of an disymmetric salen comonomer were synthesized by ATRP in solution. The controlled nature of the polymerizations is obtained only when the incorporation of the salen comonomer is less than or equal to 10%.After complexation with cobalt, these complexes are shown to be capable of effective cooperative activation, leading to the targeted product with high yields and selectivities as catalysts in Hydrolytic Kinetic Resolution (HKR) of epibromohydrin.Constantio Constantini fratre imperatoris, matreque Galla.We also reported the polymerization of styrene on the silicon surface by ATRP after grafting of the initiator. Several methods of initiator grafting have been used either directly from the hydrogenated surface or indirectly from an acid or ester surface. Styrene has been successfully mass polymerized in a controlled manner on silicon with thicknesses of 9-29 nm of the layer obtained by ellipsometry and Atomic Force Microscopy
Godou, Timothé. „Mimer la chimie des hydrosilanes et hydroboranes par l’activation catalytique de dérivés silylés et borés de l’acide formique“. Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS307/document.
Der volle Inhalt der QuelleGlobal energy needs are mostly covered by the use of fossil fuels such as oil, coal or gas. The use of these fossil resources in the field of energy or the chemical industry causes a high accumulation of CO2 in the atmosphere and causes climatic disturbances. In addition to posing a major ecological problem, these fossil resources are not renewable and will pose a problem of availability in the long term. To overcome these difficulties, one possible solution is to limit or even stop the use of fossil resources in favor of renewable carbon sources such as CO2 or biomass. These resources could be used as a source of chemicals and / or storage of intermittent energies. These uses require the conversion of oxygenates with C=O (such as CO2) and C–O (such as biomass) and require energy input into reduction reactions. Few reducers are compatible with this use which requires the use of compounds both renewable and having a redox potential adapted to the reduction of C–O bonds. These are essentially dihydrogen and formic acid. In this context, this doctoral work aims to define and meet the specifications of a renewable reducer. In the first place, the use of silyl formates is explored, through reactions mimicking the behavior of hydrosilanes. This strategy is used in dehydrogenating coupling reactions and for the reduction of ketones by transfer hydrosilylation. Finally, this concept is transposed to transfer hydroboration with the use of boryl mono formate compounds and a catalyst involving a participative ligand. The boryl and silyl formates thus appear as attractive renewable reducers, which combine a source of renewable hydride (formic acid) with an oxophilic element of the main group whose stereo-electronic properties are easily adjustable
Roumanie, Marilyne. „Microréacteur pour la catalyse hétérogèneApplications : Stockage d'hydrogène dans les hydrocarbures Filtre pour capteur gaz“. Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 2005. http://tel.archives-ouvertes.fr/tel-00012119.
Der volle Inhalt der QuelleO'Donnell, Benedict. „Plasma grown silicon nanowires catalysed by post-transition metals and applications in radial junction solar cells“. Palaiseau, Ecole polytechnique, 2012. https://pastel.hal.science/docs/00/76/15/66/PDF/ODonnell_-_PhD_2012.pdf.
Der volle Inhalt der QuelleIn this thesis, disordered arrays of vertical silicon nanowires are used to trap light in PECVD-deposited silicon solar cells. The abrupt surface which they present can absorb light efficiently and be manufactured in the same vacuum run as the other layers of the cell, offering the prospect of dispensing with the additional fabrication steps conventionally required to texture the substrates of thin-film photovoltaics. Drops of liquid tin and indium, designed to catalyze the growth of silicon nanowires, were deposited and rearranged on transparent conducting oxide substrates under vacuum to obtain metal drop configurations with diameters and densities spanning several orders of magnitude. In discussing the suitability of different metals to catalyze the growth of silicon nanowires, we have highlighted distinctions between the behavior of transition and non-transition metals for vapor-liquid-solid growth and studied in particular the case of silicon nanowires catalyzed by tin. Nanowires doped P-type with the appropriate morphology were covered in conformal layers of intrinsic and N-type hydrogenated amorphous silicon, and an indium-tin-oxide electrical contact to produce networks of 107 radial PIN junctions connected over areas of 3. 1 mm². Optimizing the fabrication process of these devices has led to open-circuit voltages of 0. 8 V and short-circuit currents of 13 mA/cm². The cells are deposited over untextured substrates using techniques which are compatible with a single pump-down process. Their ability to trap light rivals that of established texturing techniques and their performance comes close to that of planar PIN structures
Rey, Nadège. „Synthèse de silices hybrides méso-structurées par auto-assemblage : vers des applications en catalyse“. Thesis, Montpellier, Ecole nationale supérieure de chimie, 2019. https://theses.enscm.fr/interne/ENSCM_2019_REY.pdf.
Der volle Inhalt der QuelleHybrid Silica-based materials have been investigated for many applications, ranging from micro-lenses for optics to drug encapsulation for health. In particular, the incorporation of metal cations in organized silica-based network is essential to the design of supported catalysts. Si-based matrices exhibit tunable mechanical properties, thermal stability and porosity. These matrices can be prepared with different shapes that play a role in their applications. Rods, stars, dumbbell, layer or polymeric network, that can be categorized in 2D or 3D architectures, are among the shapes encountered in the literature. For the construction of 2D and 3D architectures, several families are studied, such as bridged silsesquioxanes, polyhedral oligomeric silsesquioxanes (POSS) and lamellar silica.Lamellar silica is used as scaffolds or 2D building blocks to create functional materials. Crystalline layered silicates are easily modified by the intercalation of guest molecules and ions in the interlayer. Covalent modification is achieved by silylation of the interlayer Si–O- / Si–OH groups with organosilanes. Moreover POSS consists of a cage-like structure and formula (RSiO3/2)n, R being an organic group. T8 structure is the most common one which when it is octa-substituted can be used as a node in a polymer-like self-assembly by connection to other POSS. In the case of a mono-substituted cage, two scenarios are available: functionalization of the substituted corner or synthesis of dumbbell-like object formed by grafting of another POSS.In this work, the aim is to provide new functional hybrid materials involving original 2D and 3D architectures.2D self-structure assemblies, made of lamellar silica and silylated organic linkers, will be used for complexation reactions and catalysis For this purpose, there is a need for new functional linkers. Here, we present the original synthesis of linkers for the assembly of the 2D structures. Inspired by previously reported bis-urea compounds, we designed and prepared bi-functional urea-thiourea monosilylated linkers. The originality of these flexible molecules comes from the combination of four key sites allowing interactions or complexation: (i) the silyl moiety will serve as a single grafting anchor to the lamellar silica, (ii) the urea moiety will promote order in the self-assembled layer via H-bonding, (iii) the thiourea moiety will mainly serve for the coordination of metallic cations and (iv) in the case of the monosilylated precursors, the terminal functional R group will offer the possibility of self-organization of the pillars within the layer. Hence long alkyl chains are likely to interact through Van der Waals interactions and to tune the interlayer distance and thus the size of the cations possibly hosted within the layers while aryl R groups will enable the self-assembly thanks to the-conjugated system.3D self-structure assemblies will be synthesized from POSS and bis-silylated organic linkers. We used a bis-silylated version of the urea-thiourea compound as well as various bis-silylated malonamide compounds. The panel of malonamide compounds will allow to tune the flexibility of the final structure offering more or less accessibility for the metal complexation in the system. Prior to the materials synthesis, we investigated the feasibility of various dumbbell systems as models for the future studies and for a better understanding of the possible arrangement of these units within the final corresponding materials. We also demonstrate the formation of polymeric-like self-assembled hybrid silica by using Si-H functionalized POSS/POS connected with the same bridging units
Chauvier, Clément. „Nouvelles réactions d'hydroboration et d'hydrosilylation par transfert avec des réducteurs renouvelables à base d'acide formique“. Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS359/document.
Der volle Inhalt der QuelleThe utilization of cheap and abundant sustainable resources such as carbon dioxide or biomass derivatives as source of fuel and chemicals imposes the development of efficient reduction methods, able to promote the conversion of C-O bonds (π and σ) into C-H bonds in an energy and atom efficient manner. Within the realm of C-O reduction methods, the utilization of main group element-based hydrides (e.g. LiAlH₄ or NaBH₄) has proven highly beneficial in terms of selectivity and versatility in the reduction of various functional groups, including poorly electrophilic CO₂. This behavior not only stems from the positive kinetic attributes of these reductants in hydride transfer reactions but also from the oxophilicity of the main group elements that ensures the reductions are downhill processes. Yet, the latter appealing features comes at an energetic price, and the preparation of main group hydrides mainly relies on energy-demanding processes, which in turn limit the recyclability of these reductants. With the goal in mind to circumvent these limitations while preserving the beneficial properties of the main-group element during reduction, one of the major objectives of the research project presented therein was to study the unknown reductive chemistry of boryl formate and silyl formates. The latter indeed combine a renewable hydride source (formic acid can be obtained by 2e electroreduction of CO₂) linked directly to the main group element by the oxygen atom of the formate, which hints at the recyclability of this class of main group element-based reductants. Through a joint experimental and theoretical study, it will be demonstrated that these compounds can advantageously replace non-renewable hydroboranes or hydrosilanes in various reducing processes, which will be unified behind the more general concept of transfer hydroelementation
O'donnell, Benedict. „La croissance plasma de nanofils de silicium catalysée par l'étain et l'indium et applications dans les cellules solaires à jonctions radiales“. Phd thesis, Ecole Polytechnique X, 2012. http://pastel.archives-ouvertes.fr/pastel-00761566.
Der volle Inhalt der QuelleRaachini, Rita. „Nanoparticles of Ni strongly embedded in porous silica : towards the design of efficient catalysts for lignin hydrogenolysis“. Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS540.
Der volle Inhalt der QuellePhenols may be obtained from lignin instead of petroleum. Here, improving lignin conversion by hydrogenolysis, while limiting side hydrogenation of produced phenols using nickel-based catalysts instead of noble metals, was our main concern. Porous materials made of highly dispersed nickel onto silica were synthesized by different ways, characterized before and after reduction under H2, then tested in the hydrogenolysis of three compounds bearing C-OAr bonds, as in the β-O-4 linkage of lignin, using isopropanol as H-donor. In a first series of materials, Ni was introduced by the impregnation of Aerosil-380 in the presence of ammonia and similar materials were prepared with Rh. The latter favored phenol formation but resulted in much slower C-OAr cleavage. In fact, the most active catalyst was found to be the Ni-based one, affording high phenol productivity could be reached by reducing the Ni-based catalyst at high temperature. Unlike Ni, no Rh-phyllosilicates were detected, this was related to the counterion in the precursor and the metal itself. Secondly, designing highly dispersed nickel-based mesoporous monoliths with different pore structures (Sx) (wormlike, hexagonal or cubic pore structures) through an original sol-gel method. Divergences were observed between the reduced forms of NiII@Sx, with better yields with the more open cubic structure. The resulting solids were compared to two materials obtained by the impregnation of either aerosil silica or a hexagonal silica monolith with Ni(II) in the presence of ammonia in order to study the effect of the support and the incorporation method. the best catalyst with respect to phenol selectivity, avoiding its hydrogenation to cyclohexanol, was Ni-based aerosil silica. Lastly, studying the effect of adding a second metal with Ni (Co or Fe) by three methods, impregnation of Co or Fe on Ni@SBA-15 like monolith, a direct one-pot synthesis introduction or co-impregnation of both metals Ni and Co or Fe on blank SBA-15 like monolith. The incorporation method of metals is the most critical parameter. Incorporation Co or Fe by “two-solvents” method on Ni@SBA-15 like monolith led to the best catalytic activity in terms of selectivity towards phenol. In fact, not all active species were sufficiently reduced and it would be interesting to increase the reduction temperature of these solids and to optimize the reaction conditions
Ruiz, Johal. „Nouvelles synthèses par catalyse de composés organosilicés et leur transformation en fragments de polycétides“. Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S138/document.
Der volle Inhalt der QuelleThe aldol reactions is one of the most important and commonly used methods to form C-C bonds. The catalytic tandem isomerization-aldol reaction of allylic alcohols allows to perform this reaction with many synthetic advantages. Thus, we have prepared by this method beta-hydroxyacylsilanes from alpha-hydroxyallylsilanes. First, we have attempted to develop a catalytic asymmetric version of this reaction, and also to synthesize beta-hydroxyacylsilanes by direct aldol reaction. Then, we used alpha-hydroxyallylsilanes to prepare alpha-silyl aldols trough epoxidation reactions. Next, we synthesized aldols from protected beta-hydroxyacylsilanes in a simple and efficient fashion which allowed us to perform iterative aldol reactions. We have illustrated the potential of this method by the synthesis of a fragment of (±)-pironetine. Finally, we have synthesized, from the same protected beta-hydroxyacylsilanes, silyl enol ethers that next have been used successfully as substrates for Mukaiyama aldol reactions
Char, Joëlle. „Nouvelles réactions de couplages des organosilanes pour la synthèse d’esters à partir du CO₂ et de sulfones à partir du SO₂“. Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS262/document.
Der volle Inhalt der QuelleCross coupling reactions are well studied reactions and their development was awarded a Nobel price. These reactions aim at coupling organometallic nucleophiles and electrophiles compounds and are the best way to form a little to none polarized bond such as C–C and C–S bond. They however make use of strong nucleophiles, decreasing their selectivity and tolerance. On one hand, among all available nucleophiles, organosilanes are very attractive because of their abundance, selectivity, stability and tolerance towards functional groups, they are also less toxic, easy to handle, and cheap. Their use though is a challenge because of their lower reactivity. On the other hand, for the sake of increasing the atom economy of a reaction, carbon dioxide (CO₂) is the best source of carbon and ester functional group; and sulfur dioxide (SO₂) is the best source of sulfur and sulfone functional group. In this manuscript, we herein report several coupling reactions between organosilanes giving a direct access to esters from CO₂ and to sulfones from SO₂. Experimental and theoretical studies have been carried out to develop a coupling reaction between arylsilanes, CO₂ and alkyl halides catalyzed by a copper(I) complex. SO₂ being more electrophilic and more nucleophilic, is used in a catalyzed less coupling reaction with arylsilanes and alkyl halides and in a coupling reaction with allylsilanes and aryl halides catalyzed by a palladium(II) complex, known as sulfonylating Hiyama coupling
Jeon, Taewoo. „Nanostructured hybrid solar cells based on PECVD grown SiNWs and organic semiconducting polymers“. Palaiseau, Ecole polytechnique, 2013. http://pastel.archives-ouvertes.fr/docs/00/91/78/26/PDF/Thesis_Taewoo_JEON_EP_PICM.pdf.
Der volle Inhalt der QuelleSolar cells are an exciting alternative energy technology due to the infinite energy source, the Sun. Many types of solar cells based on inorganic or organic materials are currently developed with the objective of higher efficiency and lower cost. In this context, this thesis suggests to study nano-structured hybrid solar cells based on silicon nanowires (SiNWs) and organic active materials to benefit advantages of both materials. SiNWs are grown by PECVD on transparent conducting oxide via Vapor-Liquid-Solid (VLS) mechanism with careful control of their nano-morphology. The organic materials made of polymers or blend polymers are then deposited by spin-coating on top of SiNWs. In these hybrid solar cells the SiNWs are used as light-trapping medium and/or electron acceptor material. For better solar cell performance, the optimization of SiNWs array is carried out by removing residual catalyst and etching parasitic hydrogenated amorphous silicon. Their effects on hybrid solar cells have been fully analyzed and discussed. Furthermore, the electron-acceptor properties of the nano-structured SiNWs have been estimated with Bismuth-doped n-type SiNWs. The results clearly reveal the potential of this type of hybrid solar cells, namely, 1) power conversion efficiency improvement by enhancing external quantum efficiency in longer wavelength regime and 2) variety uses of SiNWs by tuning their electrical property and morphology
Jeon, Taewoo. „Cellules solaires hybrides à base de polymères et de nanofils de silicium fabriqués par dépôt chimique en phase vapeur assisté par plasma“. Phd thesis, Ecole Polytechnique X, 2013. http://pastel.archives-ouvertes.fr/pastel-00917826.
Der volle Inhalt der QuelleCarreras, Virginie. „Réactions d'insertion énantiosélective de composés diazoïques dans la liaison silicium-hydrogène et synthèses de cyclopropènes via la cycloaddition [2+1] d’alcynes avec des diazirines en flux continu“. Doctoral thesis, Université Laval, 2021. http://hdl.handle.net/20.500.11794/69597.
Der volle Inhalt der QuelleThe insertion of diazo compounds into the Si–H bond is a direct and efficient method of synthesizing organosilanes. Various methods employing catalysts, in particular asymmetric catalysts, have been studied in the past. The common issue, detailed in the first part of this thesis, is the use by existing methods of complex and expensive chiral catalysts. This can make the synthesis and use of chiral organosilanes less attractive. This is why in Chapter 1 a green method of asymmetric catalysis for the synthesis of chiral organosilanes is developed, using diazo compounds. This route employs an inexpensive CuI catalyst system, an easy-tosynthesize ligand, mild reaction conditions and which show excellent results. A wide range of chiral organosilanes have been synthesized with yields up to 98% and enantioselectivities up to 98:2 er. To get insight into the reaction mechanism of this reaction, isotopic, competition or computational studies allowed us to understand the key steps of this transformation. The second part of this thesis was to develop an innovative method for the synthesis of gem-difluoro alkenes via an 1,2-desilylative defluorination reaction of organosilanes. This gem-difluorinated alkenes are real synthetic tools, often used in many subsequent reactions. This is why simplifying its synthesis by the 1,2-desilylative defluorination of trifluoromethylated organosilanes represents a real potential. This transformation arises from the possible application to the synthesis of organosilanes via the insertion of diazo compounds into the Si–H bond. The addition of a catalytic amount of fluoride on trifluoro-methylated organosilanes activates the catalytic system that provides excellent yields of gem-difluoro alkenes. Various examples and applications have been demonstrated. This method promotes the use of polyfluoromethylated organosilanes for the synthesis of perfluorinated alkenes. The third chapter of this thesis was about the cyclopropenation of alkynes by cycloaddition [2+1] with the use of carbene precursors. The first part consisted in studying the photochemical decompositions of the diazo compounds and diazirines, using a continuous flow system. The aim was to present a new pathway for the synthesis of trifluoromethylated cyclopropenes. This transformation has shown excellent results with the use of trifluoromethylated diazirines, for the synthesis of new cyclopropenes. Different ranges of LEDs were used to be suitable for a wide range of diazirines. Control experiments were carried out, and comparison of diazo compounds vs diazirines reactivities, and also comparisons of cyclopropenation vs cyclopropanation transformations could be evaluated. We were also able to benefit from the advantages of using continuous flow by allowing us to work on several grams, while remaining safe. Lastly, using synchronous measurements of infrared spectra, we were able to illustrate the presence of diazo compounds during the decomposition of diazirines by photochemistry, allowing us to raise certain hypotheses about the reaction mechanism The second part of chapter 3 illustrates the development of an asymmetric synthesis of chiral cyclopropenes by repeating the concepts developed above for the Si–H insertion. This reaction involving trifluoromethylated diazo compounds has not yet shown satisfactory results. This part is still under study and other approaches are being considered to date.
Commandeur, Claude. „Chimio-et stéréosélectivité induites par le silicium dans des réactions d'allylation catalysées par le palladium : application aux cyclisations 5-et 6-endo-trig“. Paris 6, 2003. http://www.theses.fr/2003PA066066.
Der volle Inhalt der QuelleBatt-Coutrot, Delphine. „Recherche de nouveaux catalyseurs isospécifiques destinés à la polymérisation du propylène : catalyse Ziegler-Natta et métallocène“. Nancy 1, 2000. http://www.theses.fr/2000NAN10070.
Der volle Inhalt der QuelleJanisch, Daniel. „Geo-inspired pathways towards ternary non-noble metal (pre-)catalysts for water splitting and CO2 reduction“. Electronic Thesis or Diss., Sorbonne université, 2023. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2023SORUS387.pdf.
Der volle Inhalt der QuelleA full transition from fossil-based energy sources towards green energy production requires storage systems compensating for the intermittency of renewables. The production of green hydrogen from electrolysis of water powered by surplus electricity from solar or wind attracts a lot of attention as an abundant, clean and renewable energy vector. Beyond the electrolysis of water, surplus renewable energy can further be stored in more complex fuels or chemicals. Related to electrolysis, the electroreduction of CO2 (CO2R) yields energy-dense hydrocarbons storing also energy in chemical bonds. A lack of economic viability, however, still blocks widespread industrial use of these processes. The benchmark electrodes in water electrolysis cells are platinum group metals that are expensive and not abundantly available. Compounds of more common transition metals represent a much cheaper alternative as potential electrocatalysts for water splitting. It was shown that activity and stability in both acidic and alkaline electrolytes is enhanced most notably in binary transition metal borides (TMBs), silicides (TMSs) and carbides (TMCs). Covalent bonds between p-block elements and between these elements and the transition metals, and the resulting modifications of the metal charge density have been identified as key factors responsible for augmented catalytic activity. Nevertheless, the structure-activity relationship remains obscure and whether catalytic properties could be further boosted by a twofold combination of p-block elements with a transition metal has not been answered. Low CO2R selectivity is the current bottleneck in this process as intricate downstream product separation renders an industrial process unprofitable. Copper is the only metal electrocatalyst able to form substantial amounts of C+2 hydrocarbons. Again, p-block elements such as sulphur are reported to increase selectivity in copper sulphides to one-carbon products. Yet, the role of sulphur during CO2R remains unclear and whether a second p-block element could tune the charge state of copper to favour a single reduction pathway towards C+2 products has not been explored. To resolve these open questions, we have designed reaction pathways towards ternary compounds combining a transition metal with two p-block elements. The reaction processes are inspired by geological processes and rely on the use of molten salts as reaction media. Compared to classical solid-state synthesis, molten salts increase diffusivity of reactants and enable overall lower temperatures and reaction times. As a result, the process is prone to deliver nanostructured materials with high surface-to-volume ratio and without organic surface ligands, which is ideal for catalytic applications. In the first part of this work, the synthesis of four ternary transition metal silicoborides Ni6Si2B, Co4.75Si2B, Fe5SiB2 and Mn5SiB2 is presented, together with a detailed study of the electrocatalytic properties for alkaline water oxidation (OER). Synchrotron radiation-based in situ XRD resolves the formation mechanisms during the synthesis and sheds light on structural relationships between reaction intermediate and the final products. The second part is dedicated to the investigation of the influence of silicon, boron and carbon on molybdenum in three ternary compounds, Mo2BC, Mo4.8Si3C, Mo5SiB2, as electrocatalysts of hydrogen evolution from acidic and alkaline aqueous electrolytes. XPS and XAS point out the relationship between the oxidation state of molybdenum and the electrocatalytic activity. The assessment of two ternary copper silicosulphides Cu8SiS6 and Cu2SiS3 as catalysts for CO2R constitutes the topic of the third part of this work. The crystallisation sequence during synthesis was monitored during in situ XRD measurements and electronic configurations were assessed by XPS and XAS. Finally, in situ XAS during CO and CO2 reduction reactions shows how the materials evolve during electrocatalysis
Colin, Boris. „Développement de méthodes de criblages et d'analyses en parallèle appliquées aux polymères modifiés silanes“. Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S145.
Der volle Inhalt der QuelleThe aim of this work is to discover new catalytic systems to replace organotin compounds. The strategy used on our laboratory exploits tools of high throughput experiments to test a large number of catalysts in the same time in order to discover new catalytic systems more quickly
Maheshwari, Himanshu. „Functional 1D mesochannels for Electrochemical Sensors“. Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0267.
Der volle Inhalt der QuelleIn this thesis, we discuss vertically oriented mesoporous silica and their characteristic properties, synthesis procedures and applications. It is of particular interest as it provides direct access to underlying substrate through the pores and is suitable for a variety of applications such as molecular sieving, electrode protection, enhanced detection of cations through electrochemistry and electrochemiluminescence, deposition of isolated metallic and polymeric nanowires, DNA biosensor, etc. We then discuss the electrochemically mediated oxidation of natural aminothiols (cysteine, glutathione and homocysteine) by a ferrocene derivative following an EC’ mechanism and the rate kinetics at a bare indium-tin oxide (ITO) electrode. Further, mesoporous silica thin films exhibiting vertical nanochannels were grown by electrochemically assisted self-assembly method onto ITO electrode. When using the silica film deposited electrodes and ferrocenedimethanol (Fc(MeOH)2) as mediator in solution, both cysteine and glutathione can be oxidized by Fc(MeOH)2+ generated at the electrode surface, following an EC’ mechanism. Electron transfer rates were three times faster with cysteine than glutathione, suggesting that selectivity for cysteine could be achieved using mesoporous films. This was exploited for the reagent-free selective detection of cysteine over glutathione by using a ferrocene-functionalized mesoporous silica film on ITO electrode, based on a combination of charge transfer kinetic and mass transport limitations through the oriented nanochannels. This has been demonstrated by cyclic voltammetry and amperometry in a flow injection analysis mode. Experimentally, the lowest concentration of cysteine detected was 3 µM in flow injection analysis mode. Further, microelectrodes made of ITO and carbon were fabricated and modified with mesoporous silica. Carbon microelectrodes were further functionalized with ferrocene and characterized electrochemically. Overall, silica modified electrodes show a good potential in electroanalytical applications for a variety of reagents through their size and charge selective properties
Hantzer, Sylvain. „Nouveaux materiaux pour la reaction d'hydrodesulfuration (hds)“. Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13120.
Der volle Inhalt der QuelleLacroix, Maxime. „Optimisation et caractérisation d’un nouveau support catalytique à base de mousses alvéolaires de β-SiC : Application à la synthèse de Fischer-Tropsch“. Université Louis Pasteur (Strasbourg) (1971-2008), 2008. https://publication-theses.unistra.fr/restreint/theses_doctorat/2009/LACROIX_Maxime_2009.pdf.
Der volle Inhalt der QuelleThe catalytic Fischer Tropsch Synthesis (FTS) enables the transformation of synthetic gas, i. E. Mixture of H2 and CO, into a distribution of hydrocarbons (CnH2n+2 with 1 < n < 60-100), more or less saturated and more or less oxygenated. The Gas to Liquids way, including FTS, is consequently an opportunity allowing the transformation of the flared and/or stranded gas into liquid hydrocarbons for car or plane fuelling. This could first reduce the CO2 release in the atmosphere and secondly increase the oil resources by the transformation of natural gas. The classical catalysts used in Fischer-Tropsch processes are composed of cobalt or iron supported on alumina or silica, and, although they present good performances, they are highly constricted by the high exothermicity of the reaction inducing high temperature on the catalyst surface, leading to low selectivity towards desired products (i. E. Long chained parafins). In this context, silicon carbide (β-SiC) has been proposed as replacement support to alumina and silica in order to better evacuate the heat released by the reaction and thus keeping higher selectivity even at high conversion levels. Moreover, always in order to optimize the process, the impact of the catalytic support morphology (extrudates, cellular foams) on the Fischer-Tropsch reaction has been studied. It appeared that the intrinsic properties of the cellular supports (high effective thermal conductivity, low pressure drops) could let foresee new perspectives in the fixed bed FT reaction. In this work, silicon carbide as catalyst support revealed to be far more attractive than alumina both in the form of extrudates or cellular foams. Indeed, thermal runaway have been observed on alumina whereas the use of β-SiC allowed better control of the temperature and thus better selectivity towards C5+ products. A study on the influence of the active phase charge on the catalytic performances of the catalyst supported on β-SiC foams has been performed. A simple geometric model of the foam as been developed in order to estimate the pressure drop induced by the cellular supports. A correlation with classical packed beds was showed to be able to model the pressure loss induced by a gaseous flow in the cellular material. Finally, a study on the biphasic behaviour of β-SiC foams has evidenced higher liquid hold-ups compared to classical packed beds. The influence of this property on the FT reaction has here not been made and will be the subject of a next study
Wardag, Alam Rahman Khan. „Filtration and Catalytic Reaction in Trickle Beds - Use of Solid Foam Guard Beds to Mitigate Fines Plugging“. Thesis, Université Laval, 2012. http://www.theses.ulaval.ca/2012/29089/29089.pdf.
Der volle Inhalt der QuelleDemichel, Olivier. „Propriétés électroniques de nanofils de silicium obtenus par croissance catalysée“. Phd thesis, Grenoble, 2010. http://www.theses.fr/2010GRENY001.
Der volle Inhalt der QuelleFor a bottom-up approach, the catalysed growth of nanowires opens the way for numerous applications: vertical nano-transistors with a surrounding gate, core-shell heterostructures and so on. . . With these new devices, new questions emerge concerning catalyst or surface influences on the nanowire electronic properties. My work, based on a spectroscopic study with photoluminescence experiments underlined the predominant role of the surface on the electronic properties of nanowires. The surface state passivation allowed to observe the radiative recombination of free carriers of a dense phase: the electron-hole liquid, in gold- and copper-catalysed nanowires. This liquid phase has the singularity to be stable and its density is constant. This property is unique in semiconductors and led to a quantitative study of the influence of the surface via a modification of the surface/volume ratio. An original method for the surface recombination velocity (SRV) measure has been developed and very low SRV have been measured which is linked to an efficient passivation of surfaces states. The volume properties of gold-catalysed nanowires were found to be very similar to those of standard bulk silicon used in micro-electronics. Finally, the sacrificial oxidation of silicon allowed to obtain nanowires whose diameter were smaller than 10 nm. The progressive oxidation of nanowires allowed the observation of a shift of the PL line towards lower energy attributed to strains, then the increase of the gap energy is correlated to the carrier quantum confinement
Demichel, Olivier. „Propriétés électroniques de nanofils de silicium obtenus par croissance catalysée“. Phd thesis, Grenoble, 2010. http://tel.archives-ouvertes.fr/tel-00437370.
Der volle Inhalt der QuelleBoualleg, Malika. „Nouveaux catalyseurs hétérogènes bien définis obtenus par croissance contrôlée d’une matrice silicique nanostructurée autour de nanoparticules métalliques“. Thesis, Lyon 1, 2009. http://www.theses.fr/2009LYO10155.
Der volle Inhalt der QuelleNew materials containing nanoparticles were prepared by the control growth of a mesostructured silica matrix around differents metal colloids (Ru, Pt, Pd, Au). This original methodology led to the selective and regular localisation of small metal nanoparticles in the pores, in the walls, or both in the pores and in the walls of mesostructured silica matrixes. These materials were obtained by: i) the preparation hydrophilic/hydrophobic metal colloids. ii) the growth of silica around these colloids via a solgel process, and using a template. iii) the removal of the surfactant to release the porosity and the NPs surface. The colloidal solutions and the materials were characterised with several techniques such as N2 adsorption/desorption, T.E.M, XRD, WAXS, elemental analysis... Besides, their catalytic performances were tested in propene hydrogenation, isobutane dehydrogenation or CO oxidation and were compared to those of a reference catalyst
Boukhicha, Rym. „Croissance et caractérisation des nanofils de silicium et de germanium obtenus par dépôt chimique en phase vapeur sous ultravide“. Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00595422.
Der volle Inhalt der QuelleGaboriau, Dorian. „Nanostructures de silicium par croissance chimique catalysée : une plate-forme pour des applications micro-supercondensateurs“. Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAV073/document.
Der volle Inhalt der QuelleSupercapacitors are electrochemical energy storage devices which have been recently developed, and possess intermediate performances between dielectric capacitors and batteries. These components exhibit interesting power and energy densities, combined with an exceptional cycle life and an easy miniaturization. Supercapacitors are thus envisioned as energy storage solutions for electronic micro-devices, such as autonomous micro-sensors or implantable medical devices.In recent studies, CVD nanostructured silicon proved to be an excellent electrode material candidate for micro-supercapacitor applications. Bottom-up synthesis allows an exceptional control of the morphology and electrical properties of the obtained silicon nano-wires and nano-trees. Moreover, the nanostructured electrodes possess superior electrochemical and temperature stability. These arguments lead to consider silicon as an excellent platform for micro-supercapacitors applications.This PhD thesis details various ways to improve and use silicon nano-wires and nano-trees. The nanostructures have been subjected to a systematic optimization study, yielding a significant increase of the electrochemical performances of the electrodes, compared to previously published studies. In addition, surface functionalization using thin ALD alumina layers permitted a considerable increase of the supercapacitor voltage window and an improved electrochemical stability. Finally, “on-chip” nanostructure growth, and temperature stability studies of the device were conducted, opening a broad field of improvements and potential uses for these silicon nanostructures
Le, Thi Ha-Linh. „Molecular dynamics simulations of H-induced plasma processes and cluster-catalyzed epitaxial growth of thin silicon films“. Palaiseau, Ecole polytechnique, 2014. https://tel.archives-ouvertes.fr/pastel-00985657/document.
Der volle Inhalt der QuelleThree different processes taking place in a plasma reactor; namely, heating and melting of plasma-born hydrogenated silicon clusters by reactions with atomic hydrogen, hydrogen-induced healing of cluster-damaged silicon surfaces, and cluster-catalyzed epitaxial growth of thin silicon films have been investigated by means of molecular dynamics simulations. Two plasma-born hydrogenated silicon clusters representing amorphous and crystalline structures are chosen to be exposed to atomic hydrogen as in a realistic plasma reactor. We investigate quantitatively how the clusters heat up and melt by the subsequent reactions with H-atoms. A silicon surface which was partly damaged by a too violent cluster impact has been treated by hydrogen atoms. We have observed that the ill-defined silicon surface is rearranged to its initial crystalline structure after the exposure with atomic hydrogen if the appropriate H-atom flux is chosen; i. E. , due to the surface reaction dynamics with hydrogen atoms, the silicon atoms of the investigated hydrogenated silicon cluster are positioned in an epitaxial surface structure. We have performed an in-depth study of the deposition dynamics of hydrogenated silicon clusters on a crystalline silicon substrate by controlling the parameters governing the cluster surface deposition. We have found that epitaxial growth of thin silicon films can be obtained from cluster deposition if the impact energies are sufficiently high for cluster atoms and surface atoms touching the cluster to undergo a phase transition to the liquid state before being recrystallized in an epitaxial order. Yet more strikingly, by applying a non-normal incidence angle for the impinging clusters, the epitaxial growth efficiency could considerably be enhanced. Those findings are crucially important to improve the high-speed growth of epitaxial silicon thin films at low temperatures using Plasma-Enhanced Chemical Vapor Deposition (PECVD) techniques for industrial applications
Roussey, Arthur. „Preparation of Copper-based catalysts for the synthesis of Silicon nanowires“. Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10164.
Der volle Inhalt der QuelleThe work presented in this PhD thesis aimed at the preparation of copper nanoparticles of controllable size and their utilization as catalysts for the growth of silicon nanowires in a process compatible with standard CMOS technology and at low temperature (< 450°C). The growth of silicon nanowires by Chemical Vapor Deposition (CVD) via the catalytic decomposition of a silicon precursor on metallic nanoparticles at low temperature (Vapor Solid-Solid process) was demonstrated to be possible from an oxidized Cu thin film. However, this process does not allow the control over nanowires diameter, which is controlled by the diameter of the nanoparticle of catalyst. In this PhD is presented a fully bottom-up approach to prepare copper nanoparticles of controllable size directly on a surface without the help of external stabilizer by mean of surface organometallic chemistry. First, the preparation of copper nanoparticles is demonstrated on 3D substrates (silica and titanium nitride nanoparticles), along with the fine comprehension of the formation mechanism of the nanoparticles as a function of the surface properties. Then, this methodology is transferred to planar (2D) substrates typically used in microelectronics (silicon wafers). Surface structure is demonstrated to direct the Cu nanoparticles diameter between 3 to 40 nm. The similarities between the 2D and 3D substrates are discussed. Finally, the activity of the Copper nanoparticles in the growth of Silicon nanowire is presented and it is demonstrated that in our conditions a critical diameter may exist above which the growth occurs
Barakat, Jean-Baptiste. „Croissance auto-catalysée de nanofils d'InP sur silicium par épitaxie par jets moléculaires en mode vapeur-liquide-solide : application aux interconnexions optiques sur puce“. Thesis, Ecully, Ecole centrale de Lyon, 2015. http://www.theses.fr/2015ECDL0027/document.
Der volle Inhalt der QuelleMonolithic integration of III-V semiconductors materials on Si substrate is essential for the Si photonic development. We aim at achieving an optical microsource based on a regular array of III-V (InAsP/InP) nanowires (NWs) standing on top a Si waveguide. Due to their ability to be fully relaxed, nanowires growth is of deep interest. This PhD thesis has been oriented towards such context especially among self-catalyzed InP NWs growth by epitaxy. Thus we have shown that highly dense and vertical self-catalyzed InP NWs accomplishment is related to Si substrate surface oxide. A monomodal or bimodal NWs distribution have been reached through a control of indium droplets formation or growth parameters. A critical pressure and a critical temperature have been found to delimit favorable growth regime. Intrinsic optical properties have been determined to be goal sufficient. Optical simulation modeling and characterization of the polarization light state in NWs and in the Si waveguide have led us to establish functional specifications to grow vertical NWs on SOI as way that their optical modes could be coupled efficiently at telecommunications wavelength
PESCHIERA, ERIC. „Synthese de carbure de silicium a partir de charbon actif et de monoxyde de silicium en vue de son application en tant que support de catalyseur“. Université Louis Pasteur (Strasbourg) (1971-2008), 1993. http://www.theses.fr/1993STR13261.
Der volle Inhalt der QuelleChainet, Fabien. „Spéciation du Silicium dans les charges d'hydrotraitement“. Thesis, Pau, 2012. http://www.theses.fr/2012PAUU3022/document.
Der volle Inhalt der QuelleSilicon is known to be a severe poison for hydrotreatment (HDT) catalysts especially in naphtha and gasoline samples. The objective of the PhD was to develop analytical methods for silicon speciation in order to characterize silicon molecules formed during refining steps which potentially affects HDT catalysts. For the analytical strategy, different high-technology analytical tools based on gas chromatography coupled to mass spectrometry (MS and ICP/MS) were developed. Due to the high reactivities of several silicon species, representative samples of PDMS degradation were produced under thermal cracking of a mixture of heptane/xylene (500°C) using a pilot plant. The previously developed analytical strategy was applied to these samples and demonstrated the occurrence of silicon under a wide array of chemical forms. More than a hundred of silicon species belonging to 10 chemical families with a number of silicon atoms ranging from 1 to 1,500 were characterized. These silicon compounds could be present in all petroleum cuts, from the gas fractions to the heavier fractions. Therefore, the investigated range of boiling points was inevitably more important than for naptha and gasoline cuts. Cyclic siloxanes (Dn) were confirmed as the major PDMS degradation products. The other silicon compounds, almost never characterized before, were recovered at trace levels but consisted of reactive groups such as hydroxy, methoxy and hydroperoxy. These silicon species were able to strongly react with the catalytic support (Al2O3) and led to its deactivation
Benali, Abdennacer. „Nanofils de Ga ( AI) As sur silicium pour les cellules photovoltaïques de 3ème génération : simulation et croissance auto-catalysée“. Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEC011/document.
Der volle Inhalt der QuelleOver the past few years, semiconductor nanowires (NWs) have aroused a lot of interest for their specific optoelectronic properties. The latter make them particularly interesting for photovoltaics. The combination of the high absorption coefficient of the III-V semiconductors and the low cost of the silicon substrates would indeed make it possible to produce low-cost and with high-efficiency photovoltaic cells. This context made it possible to write this thesis. On the one hand, the RCWA (Rigorous Coupled Wave Analysis) simulation of the light absorption in an ordered GaAs NW array on a silicon substrate and on the other hand the self-catalyzed growth of GaAs NWs by Molecular Beam Epitaxy (MBE) in Vapor-Liquid-Solid (VLS) mode. The RCWA simulation was carried out to determine the optimal parameters such as the diameter and the height of the NWs, and the period of the NW array for efficient light absorption. This work took into account both GaAlAs "passivating" layer and ITO transparent contact layer in order to define the optimal parameters. The study of the self-catalyzed growth of GaAs NWs allowed us to determine the optimal growth parameters (temperature, Ga flux, As flux, V/III ratio, ...) in order to obtain a density, diameter and height of vertical NWs correlated to simulation results. A critical V/III ratio was also determined, and in order to produce pure Zinc-Blende NWs, this ratio should not exceed that value. GaAs NWs with p-n core-shell junction were produced and characterized by EBIC and SSRM. Finally, we demonstrated the feasibility of the self-catalyzed growth of GaAlAs NWs on Si substrate by VLS-MBE
Oehler, Fabrice. „Étude et compréhension des mécanismes de croissance catalysés des nanofils de silicium obtenus par dépôt chimique en phase vapeur“. Grenoble, 2010. http://www.theses.fr/2010GRENY024.
Der volle Inhalt der QuelleSilicon nanowires hold many technological promises but require a strict dimension and shape control. Growth of silicon nanowires can be performed by Chemical Vapour Deposition using gold catalysts and silicon precursors, with and without chlorine. We identify here the roles of chlorine on the growth stability and the wire morphology. The silicon surface is shown to chlorinate in the presence of chlorine, which reduces the gold migration on the wire surface without changing the (axial) growth kinetics. Growth conditions that use chlorine are then suitable for the stable growth of sm aIl diameter silicon nanowire down to 20 nm whereas chlorine- &ee growth can be unstable. The effect of chlorine is also visible on the wire sidewaIls, where the facets evolution depends on the radial growth speed. Passivation of the surfaces is then a key point to stabilize the growth of wires and to control their morphology
Ngono, Bernadette. „Organométalliques à carbonyle masqué : quelques propriétés du lithio-1 triméthylsiloxy-2 éthylène“. Rouen, 1989. http://www.theses.fr/1989ROUES021.
Der volle Inhalt der QuelleOehler, Fabrice. „Etude et compréhension des mécanismes de croissance catalysés des nanofils de silicium obtenus par Dépôt Chimique en phase Vapeur“. Phd thesis, Grenoble, 2010. http://tel.archives-ouvertes.fr/tel-00521128.
Der volle Inhalt der QuelleLe, Ha-Linh Thi. „Simulations de dynamique moléculaire des processus de plasma induits par l'hydrogène atomique et la croissance épitaxiale de couches minces de silicium catalysée par l'impact d'agrégats“. Phd thesis, Ecole Polytechnique X, 2014. http://pastel.archives-ouvertes.fr/pastel-00985657.
Der volle Inhalt der QuelleDuong-Viet, Cuong. „Synthesis and processing of nitrogen-doped carbon nanotubes as metal-free catalyst for H2S selective oxidation process“. Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAF029/document.
Der volle Inhalt der QuelleCarbon nanotubes (CNTs) containing different doping such as oxygen and nitrogen composites have received more and more scientific attention as metal-free catalyst in the field of heterogeneous catalysis. The aim of this thesis is related to the synthesis and characterization of nitrogen-doped CNTs decorated on SiC support using both in-situ (CVD with NH3) and ex-situ (N@C) methods. Other approach was employed for the surface functionalization of CNTs is based on the use of oxidative agent (HNO3) in gas phase. This oxidation process not only creates defects on the CNTs surface but also decorates their surface with oxygenated functional groups. The as-synthesized oxygen- and nitrogen-doped CNTs are characterized by different techniques (XPS, SEM, TEM, BET, TGA). The carbon based catalysts exhibit outstanding performances in term of activity and sulfur selectivity, and very high stability with time on stream in the partial oxidation of H2S into elemental sulfur even at high gas space velocity (WHSV) and low O2-to-H2S molar ratio. The influence of the physical-chemical properties and defects present on the CNTs surface on the catalytic performance was thoroughly investigated and discussed within the framework of this work
Agenet, Nicolas. „Synthèse de composés polycycliques silylés : étude DFT de la cycloaddition [2 + 2 +2] des alcynes et de la cocyclisation 2:1 d'alcynes et d'alcènes catalysées par des complexes du cobalt“. Paris 6, 2007. http://www.theses.fr/2007PA066276.
Der volle Inhalt der QuelleHoàng, Quoc Lam. „Séparation sélective de la cellulose, des hémicelluloses et des lignines par le système catalyseur-solvant : acide formique-acide acétique, de matières végétales à teneur variable en silicium“. Toulouse, INPT, 2000. http://www.theses.fr/2000INPT002C.
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