Dissertations / Theses on the topic 'Manganese carbide'
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Akil, Cem. "Optimization Of Conditions To Produce Manganese And Iron Carbides From Denizli-tavas Manganese Ore By Solid State Reduction." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608188/index.pdf.
Full textC with MoSi2 heating elements. After each experiment weight loss data were obtained and converted to percentage reduction. X-Ray, SEM-EDS and chemical analyses were done in order to determine whether or not carbide phases have been obtained, and calculate the composition of the product. Considering the experimental results, the optimum conditions found for reduction of Denizli-Tavas manganese ore were 1250 °
C, 4 hours, 100% of stoichiometric amount of active carbon and 5% CaO addition. Under the optimum conditions 83.85% reduction of calcined ore was obtained.
Kononov, Ring Materials Science & Engineering Faculty of Science UNSW. "Carbothermal solid state reduction of manganese oxide and ores in different gas atmospheres." Publisher:University of New South Wales. Materials Science & Engineering, 2008. http://handle.unsw.edu.au/1959.4/41459.
Full textReed, Izumi N. "Effect of chromium and manganese on corrosion behavior of Fe-TiC composites." Full text open access at:, 1998. http://content.ohsu.edu/u?/etd,276.
Full textGao, Pengcheng. "Matériaux carbonés nanostructurés pour supercapacités électrochimiques." Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20028/document.
Full textVarious nanostructured carbon materials were synthesized and further served as active materials of electrical double layer capacitor or substrates of pseudocapacitive materials in order to improve power capability of corresponding supercapacitor. On the one hand, a simple synthesis of porous silicon carbides (SiCs) was achieved by performing a topotactic thermal reduction by magnesium (Mg) of a silica/ carbon composite. Thanks to the low synthetic temperature (below 800 ºC), the SiCs well preserved the pristine skeletons of their silica/carbon precursors. Successively, the SiCs with diverse porous structures from their silica/carbon precursor emerged, e.g. ordered tunable mesoporous SiCs, 3D-hierarchical meso and macroporous SiC, SiC nanosheet and SiC nanofiber. Furthermore, the porous SiCs derived from magnesio-thermal reduction were reduced to hierarchical carbons with newborn narrow distributed microporosity by chlorination. In an organic electrolyte, the hierarchical carbon combines the high specific capacitance from narrow distributed microporosity and the outstanding rate capability from ordered-arranged meso or macroporosity that make it promising for high power and energy density capacitor. On the other hand, a “benzyl alcohol route” has been used to decorate RGO nanosheets with FeOx nanoparticles. The resulting FeOx/ RGO composite, due to their hybrid nanostructure, combine both EDLC capacitive and pseudocapacitive bahaviors of RGO and FeOx, respectively. Thanks to the laminated RGO and nano FeOx particles film, the resulting composite gains the same power capability as RGO and a higher energy density than raw FeOx. Furthermore, mesoporous carbon was introduced to adorn the CNF surface through self-assemble of resol, carbon nanofiber(CNF) and Pluronic@127. After further coating with birnessite-MnO2, the composite electrode gains extra capacitance and power improvement in presence of superficially coating mesoporous carbon with pore size larger than 10nm
Nohair, Khaddouj. "Formation de liaison carbone-carbone par addition radicalaire de composés fonctionnalisés sur des oléfines : amorcage par Mn(III) formé "in situ" par voie électrochimique." Paris 12, 1991. http://www.theses.fr/1991PA120046.
Full textJohnson, Tony Richard. "Vinylidene and cyclic carbene chemistry of iron and manganese half-sandwich complexes." Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340247.
Full textMartin, Thomas Antony. "Unravelling the photochemistry of organometallic N-heterocyclic carbene complexes." Thesis, University of Bath, 2011. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.547630.
Full textVan, der Westhuizen Belinda. "Synthetic investigation of Mn(I) and Re(I) N-heterocyclic carbene complexes." Diss., University of Pretoria, 2010. http://hdl.handle.net/2263/25922.
Full textDissertation (MSc)--University of Pretoria, 2010.
Chemistry
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Zheng, Jianxia. "Earth-abundant metal complexes for catalyzed hydroelementation." Thesis, Rennes 1, 2014. http://www.theses.fr/2014REN1S148/document.
Full textThis research work deals with the use of the catalysts based on the earth-abundant transition metals of the first row of the periodic table, such as Mn, Fe, and Ni, for hydroelementation reactions. First of all, the hydrosilylation of aldehydes and ketones was accomplished using a simple Ni(OAc)₂ 4H₂O/PCy₃ catalytic system with the inexpensive and stable silane PMHS as the hydride source. The reductive amination of aldehydes with amines was also achieved with the same catalytic system and TMDS, as the silane. Second, the efficiency of manganese half-sandwich complex CpMn(CO)₂(IMes) was exemplified for the reduction of aldehydes and ketones in the presence of Ph ₂ SiH ₂ (1.5 equiv.) under UV irradiation at room temperature. Still with manganese, the challenging transformation of carboxylic acids to aldehydes was performed using commercial Mn₂ (CO)₁₀ and Et₃SiH. Third, the methylation of the secondary amines with dimethyl carbonate as an alternative and safe C1 source was demonstrated under mild conditions with [CpFe(CO)₂(IMes)]I as the catalyst. Then, the hydroboration of functionalized alkenes and alkynes was catalyzed by an iron(0) carbonyl complex Fe(CO)₄(IMes) under UV irradiation. Finally, the hydroboration reaction was successfully extended to the reduction of CO₂ to methoxyboranes with Fe(CO)₃[P(OPh)₃]₂ as the catalyst and the borane sources, such as HBpin, HBcat or 9-BBN
Bauvineau, Laurent. "Approche locale de la rupture ductile : application à un acier carbone-manganèse." Paris, ENMP, 1996. http://www.theses.fr/1996ENMP0794.
Full textDeetlefs, Maggel. "Carbene and coordination complexes of gold, palladium, platinum and manganese derived from N-containing heterocycles." Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/52155.
Full textIablokov, Viacheslav. "Manganese and cobalt oxides as highly active catalysts for CO oxidation." Doctoral thesis, Universite Libre de Bruxelles, 2011. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209847.
Full textDe l’oxyde de manganèse non-stœchiométrique (MnOx) a été préparé par décomposition spinodale d’oxalate de manganèse trihydraté en ayant recours à la technique d’oxydation programmée en température (TPO). Tant l’analyse quantitative relatives à ces données TPO que les résultats obtenus par spectroscopie de structure au front d’absorption des rayons X (XANES), ainsi que par spectroscopie des photoélectrons X (XPS) ont permis d’estimer la stœchiométrie de l’oxyde avec un x situé entre 1.61 et 1.67. En accord avec à la fois la surface spécifique élevée et la combinaison d’isothermes d’adsorption/désorption de type I et IV, la microscopie électronique à transmission à haute résolution (HRTEM) démontre la présence de micro-bâtonnets caractéristiques et « imbriqués » les uns dans les autres, accompagné de particules nanocristalline à l’extrémité de ces bâtonnets.
Les découvertes faites par spectroscopie infra-rouge de réflexion diffuse par transformée de Fourier (DRIFTS), par études isotopiques et cinétiques suggère que l’adsorption des deux molécules, CO et O2, est suivie par leur réaction en surface via des intermédiaires de type carbonate/formate, pour finalement produire du CO2. Nous supposons un mécanisme de type Mars-van Krevelen où l’oxygène appartenant à la structure de type MnOx prend part dans l’oxydation catalytique du CO à basse température. Cependant, ces espèces mobiles d’oxygènes ne faisaient pas partie du cœur de phase du réseau d’oxyde, et de ce fait, ont été capables de « sauter » sur la surface et approvisionner les espèces oxygénées nécessaires à l’oxydation du CO déjà adsorbé.
Une structure spinelle d’oxyde de cobalt Co3O4 dans lequel le cobalt présente deux états de valence (+2 et +3) a été choisie pour élucider l’effet de la taille des particules sur l’activité lors de la réaction d’oxydation du CO. Tout d’abord, des nanoparticules monodispersées de cobalt métallique présentant une déviation standard en taille inférieure à 8% ont été synthétisées à partir de carbonyle de cobalt (Co2(CO)8) par une méthode optimisée «d’injection chaude». Un contrôle de la taille des nanoparticules dans la gamme 3 à 11 nm a pu être obtenu en variant la température d’injection du carbonyle de cobalt dans une solution de dichlorobenzène et d’acide oléique. La microscopie électronique à transmission (TEM) nous montre que ces particules de cobalt sont quasiment hémisphériques. Ensuite, de la silice poreuse (de type MCF-17) a été imprégnée par des nanoparticules de cobalt, et ensuite activée par TPO menant à des nanoparticules d’oxyde de cobalt. Des études par diffraction des rayons X (XRD) et spectroscopie des photoélectrons X (XPS) ont démontré la structure spinelle Co3O4. Finalement, l’activité des catalyseurs obtenus vis-à-vis de l’oxydation du monoxyde de carbone fut mesurée à 423 K et ce en fonction de la taille des particules. Les particules de Co3O4 présentant une taille allant de 5 à 8 nm se sont révélées les plus actives. Ceci peut s’expliquer par une plus grande mobilité des atomes d’oxygène en surface des nanoparticules d’oxyde de cobalt.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
Campbell, Alistair Jonathan. "Neutron scattering studies of rare earth manganese oxides and rare earth nickel borocarbides." Thesis, University of Warwick, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343210.
Full textSiafakas, Dimitrios. "On deoxidation practice and grain size of austenitic manganese steel." Licentiate thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH. Forskningsmiljö Material och tillverkning – Gjutning, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-37788.
Full textHadfieldstålen exceptionella slitstyrkan och deformationshårdnande har gjort dessa till ettav de viktigaste materialen för tillverkning av gjutna komponenter som används inomgruv-, kross-, borr-och gruvindustrin. I alla metallegeringar som används för tillverkningav gjutna komponenter styrs de mekaniska egenskaperna av materialets mikrostruktur.Gjutna komponenter med fin mikrostruktur presentera bättre mekaniska egenskaper ochminskad risk för defekter jämfört med komponenter med grov mikrostruktur. En minskadkornstorlek i Hadfieldstål kan öka materialets hållfasthet upp till 30% och minska riskenför porositetsbildning vid stelning.Tillsatsning av spårämnen eller legeringselement i en metallsmälta för att modifiera ochförbättra mikrostrukturen kallas ympning. Denna metod används i lättmetaller och vidtillverkning av gjutjärnskomponenter, men har ännu inte fått acceptans i stålindustrineftersom forskningen inte har funnit effektiva kärnbildare att användas som ympmedel.Huvudsyftet med detta arbete är att undersöka kvalitativa och kvantitativa egenskaper hosde desoxideringsprodukter som skapas under tillverkningen av Hadfield stål och hur deunder och efter stelning påverkar mikrostrukturens grovlek. Arbetet syftar till att identifierapartikeltyper och legeringselement som är effektiva för att förfina den austenitiskamikrostrukturen och bana väg för utveckling nya och förbättra desoxiderings- ochympningsprocesser som i sin tur kommer att resultera i en förbättring av den gjutnakomponentens egenskaper.Partiklarnas utskiljning och materialet resulterande kornstorlek studerades i aluminiumochtitan-desoxidiserade Hadfieldstål, tillverkade i pilotskala. Den första delen av dettaarbete var att identifiera kvalitativa och kvantitativa egenskaper hosdesoxidationspartiklar, som typ, morfologi, sammansättning och storlek.Utskiljningssekvensen fastställdes. En modell för att förutsäga partikelstorlek och derastillväxt utvecklades. De experimentella resultaten jämfördes med termodynamiskajämviktberäkningar och utskiljningen för varje typ av partikel beskrevs. I den andra delenstuderades kornstorleken och hur denna varierade desoxideringsbehandlingen. Därefterkorrelerades kornstorleken med partikeltyp och dess karaktäristika och rangordnades efterderas förmåga att förfina mikrostrukturen. Partiklarnas kristallografiska missanpassningmot austenitens kristallstruktur beräknades och jämfördes med experimentellt fastställdarangordningen.
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Mery, Adrien. "Oxydes de manganèse et ses composites à base de nanotubes de carbone ou de graphène pour la réalisation de supercondensateurs." Thesis, Tours, 2016. http://www.theses.fr/2016TOUR4018/document.
Full textThe work realized in this thesis focused on the synthesis of manganese oxides and their assembly in composites with carbon materials (CNT, graphene) for supercapacitor applications in aqueous media. Physico-chemical and electrochemical characterizations were conducted to evaluate the effect of the nanostruturation. It was found that nanocomposites MnO2/CNT and MnO2/ reduced graphene oxide contributed to improve the electrochemical performances in aqueous media. Several compositions Mn/C were tested to estimate the best ratio for optimized electrode materials. In order to maximize the energy of the devices, asymmetric devices in aqueous media were assembled using graphene as negative electrode and nanocomposites for positive. Clear improvements in term of energy and power densities were obtained with these systems working at 2 volts in aqueous media
Bouhatmi, Marième. "Dépollution de l'habitacle automobile par photocatalyse et catalyse d'oxydation à froid." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1036.
Full textThe presence of Volatile Organic Compounds (VOCs) and carbon monoxide in indoor air is a major health issue. The vehicle cabin air is also affected by this problem, being the first mode of transportation. Most of the current depollution systems are based on trapping using adsorption methods, while photocatalytic processes offer the potential to fully degrade VOCs at room temperature in presence of relative humidity. However, carbon monoxide cannot be degraded by photocatalysis without a co-catalyst. Consequently, the room temperature oxidation catalysis of carbon monoxide has been studied. This thesis aims to develop an economical solution for cleaning the vehicle cabin air. This solution is based on crossing the photocatalytic oxidation of a target molecule the n-pentane over by TiO2 P25 and the room temperature oxidation of CO over synthesized MnO2. Results show that the n-pentane degradation rate decreases with the humidity level, and linearly increases with the irradiance power and the VOC concentration. Intermediates species are lowed concentrates (ppbv order) for ppmv of n-pentane used. Operando DRIFTS experiments highlighted the presence of formates surface species during the photocatalytic degradation of n-pentane. PTR-MS-TOF-SRI and GC-MS experiments highlighted the presence of carbonyl compounds as formaldehyde and pentan-2-one in gas phase during the degradation. Those intermediates species allowed us to propose a mechanism for the photocatalytic oxidation of n-pentane over TiO2 P25. Moreover, the efficiency of the photocatalytic degradation of n-pentane over TiO2 has been proved given that an almost complete mineralization is obtained whatever the working conditions. In catalysis, manganese oxides were synthesized by a co-precipitation method then calcined under oxygen at three different temperature: 100°C, 200°C and 300°C. The catalyst performances were evaluated for CO oxidation at room temperature in dry conditions. Temperature programmed methods were used for probing the impact of the calcination temperature on the catalyst surface. DRX and BET characterizations confirmed the formation of the phase γ-MnO2 stable between 100°C and 300°C, and a large surface area (178-197 m²/g). Results highlighted that the synthesized catalysts can oxide the CO at room temperature. The catalyst calcined at 100°C (MnO2-100) show the best performances with an initial conversion rate of 60% for 500 ppmv CO, at 10 L/h at 20% O2 (VVH = 25 000 h-1). However, a deactivation over the time of all the catalysts was observed, especially for MnO2-100. This deactivation could be related to the capacity of the catalyst to renew the oxygen bulk implied in the catalytic process
Dubarle, Offner Julien. "Novel heterobimetallic manganese-chromium and rhenium-chromium complexes : coordination, cyclometallation, benzannulation and haptotropic metal migration." Paris 6, 2009. http://www.theses.fr/2009PA066040.
Full textMessori, Alessandro. "Bidentate N-heterocyclic carbene complex of Manganese as catalyst for hydrosilylation and hydroboration of double and triple bonds." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21666/.
Full textLesne, Laurent. "Étude des mécanismes de recristallistion dans le fer de ultra-haute pureté dopé en carbone, manganèse et phosphore." Grenoble INPG, 2000. http://www.theses.fr/2000INPG4211.
Full textCourty, Claudie. "Rôle du carbone et du manganèse lors de l'oxydation du fer a haute température. Interactions avec les éléments actifs cérium et yttrium." Dijon, 1997. http://www.theses.fr/1997DIJOS024.
Full textLachaise, Isabelle. "Additions radicalaires amorcées par le manganèse au degré d'oxydation trois formes in situ par voie électrochimique : mécanisme et application à la synthèse de composés cycliques." Paris 11, 1993. http://www.theses.fr/1993PA112220.
Full textBoisset, Aurelien. "Electrolytes pour supercondensateurs asymétriques à base de MnO2." Thesis, Tours, 2014. http://www.theses.fr/2014TOUR4038/document.
Full textThe aim of this thesis was to investigate the performances of asymmetric supercapacitors based on manganese dioxide (birnessite) and activated carbon electrode materials using various electrolytes. From this work, it appears that neutral aqueous electrolytes containing inorganic salts have the best electrochemical performances. Furthermore, the nature and the structure of both ions (cations and anions) in solution seem to impact strongly the electrochemical performances of the supercapacitors, as well as, the MnO2’s structure stability and affinity. In the case of aqueous-based electrolyte, a device degradation mechanism has been proposed as a function of salt ions structure and nature to further understand the supercapacitor’s life-cycling when a large potential window is applied. Some novel synthesis ways and/or modifications were investigated to further improve the electrochemical properties of MnO2 material. Additionaly, original non-aqueous electrolytes has been also formulated and then characterized, particularly the ‘Deep Eutectic’ Solvents, based on the N-methylacetamide mixed with a lithium salt. However, these electrolytes don’t have a good affinity with manganese oxide-based materials. Interestingly, these Deep Eutectic Solvents show good cycling results with activated carbon. In fact, these electrolytes seem to be promising for high temperature energy storage applications, especially using activated carbon or insertion electrode material like the lithium ferrophosphate
Zein, Eddin Mohamed Yahia. "Caractérisation de catalyseurs bimétalliques cobalt-manganèse issus de carbonyles, actifs en hydrogénation du CO." Lyon 1, 1989. http://www.theses.fr/1989LYO10094.
Full textPibaleau, Baptiste. "Elaboration et caractérisation d'électrodes VACNT/MnO2 pour application aux supercondensateurs hybrides." Thesis, Tours, 2018. http://www.theses.fr/2018TOUR4034/document.
Full textThis thesis was focused on the development, optimization and study of composite electrodes of vertically aligned carbon nanotubes (VACNT) on an aluminum collector and modified with manganese oxide (MnO₂).VACNT were synthesized by a CVD process at low temperature (580° C) directly on the collector. Perfectly aligned CNT forest with a thickness of 20 to 80 μm were obtained with high densities of 10¹¹ NTC.cm² and whose catalyst (Fe) content is less than 1%. Their modification with MnO₂ increase their electrochemical storage capacity. In order to achiew optimal coating of VACNT by MnO₂, different precursors of the oxide and various methods ( electrochemical, chemical, CVD) were used and optimized. Composites were studied as electrode material for the realization of asymmetric supercapacitors in aqueous media. In addition, structurals, morphologicals and electrochemicals analyzes carried out on the different materials allowed a better understanding of the role of the elaboration's conditions on the properties of the VACNT/MnO₂ composites obtained
Moreno, Jean-Charles. "Vieillissement dynamique dans les joints soudés d'acier au carbonne manganèse : relation entre les paramètres métallurgiques et le comportement mécanique." Châtenay-Malabry, Ecole centrale de Paris, 1998. http://www.theses.fr/1998ECAP0604.
Full textDandeville, Yann. "Analyse thermique et électrochimique de supercondensateurs carbone-MnO2 en milieu aqueux." Phd thesis, Université de Nantes, 2012. http://tel.archives-ouvertes.fr/tel-00765136.
Full textRé, Maria Inês. "Décomposition thermique et réduction des oxydes de manganèse par le monoxyde de carbone : étude cinétique en réacteur différentiel et mise en oeuvre en lit fluidisé." Toulouse, INPT, 1993. http://www.theses.fr/1993INPT053G.
Full textCarrier, Jean-François. "Une alternative au cobalt pour la synthèse de nanotubes de carbone monoparoi par plasma inductif thermique." Mémoire, Université de Sherbrooke, 2013. http://hdl.handle.net/11143/6162.
Full textSarmeo, David. "Insertion de chlorure de manganèse dans les fibres de carbone (ex-mésophase de brai) à l'aide de complexes gazeux : application au dosage de l'énergie thermique." Grenoble INPG, 1997. http://www.theses.fr/1997INPG0191.
Full textHemming, Oliver. "Structure and reactivity of low-coordinate first-row transition metal complexes." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/structure-and-reactivity-of-lowcoordinate-firstrow-transition-metal-complexes(a7879b58-897e-4080-99f6-8551511a503a).html.
Full textLei, Yannick Ruani. "Matériaux composites électroactifs à porosité contrôlée." Montpellier 2, 2009. http://www.theses.fr/2009MON20074.
Full textAmong all systems for electrical storage, electrochemical devices are interesting because they turn chemical energy into electrical energy. Supercapacitor and Li-ion battery have high power density and good energy density, respectively. The topic of the present work is the preparation of composite electrode material MnO2/C for supercapacitor, SnO2/C for Li-ion battery and synthesis of porous SiC. This could be achieved starting by the synthesis of mesoporous carbon (900m2/g) following a hard template method. At first, the evaluation of electrochemical performances of composite electrode material for supercapacitor shows two different behaviours versus the ratio of MnO2. We could observe an optimal ratio for which capacitance was maximal (900F/g). Secondly, the volumic variations occurring while charge/discharge of SnO2/C electrode materials are contained by the carbon matrix. In spite of limited electrochemical performances for pure SnO2 electrode material, the cyclability of SnO2/C electrode materials is enhanced. At last, the synthesis of porous SiC can be achieved by the thermal reduction of SiO2/C composite using Mg as reducing agent. The as-prepared material is a replica of silica template
Srour, Hassan. "Catalyse avec des métalloporphyrines : oxydation asymétrique et transfert de carbènes." Phd thesis, Université Rennes 1, 2013. http://tel.archives-ouvertes.fr/tel-00910073.
Full textStanbury, Matthew. "Réduction photo et électro-assistée sélective du dioxyde de carbone sur des catalyseurs moléculaires." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAV094/document.
Full textThe general context of this thesis is on CO2 valorisation, and recounts fundamental research aimed at finding new molecular catalysts in order to achieve CO2 conversion. The results obtained provide additional knowledge in view of developing an efficient and selective catalytic CO2 reduction process. The first chapter begins with the general picture of CO2 utilisation and contains a bibliographical overview on the use of molecular catalysts for CO2 photo- and electroreduction. This short review demonstrates the wide variety of transition metal complexes used as catalysts, in particularly those based on rhenium. An analysis on the current state of CO2 reduction research using molecular catalyst complexes of the manganese carbonyl type is then reported. In Chapter II, the discussion begins with a brief overview of the research developed during this thesis relating to new complexes of the general formula: [Mn(L)(CO)3(X)] (X = Br, n = 0 ou CH3CN, n = 1; L = terpyridine derivatives). The interest in these complexes is twofold, as their physico-chemical properties give them potential catalytic CO2 reduction applications, as well as applications in the field relating to controlled CO release molecules. Developing new complexes based on ligands derived from terpy is one of the main routes that were chosen for catalyst performance optimisation and improvement. In this context, Mn complexes were synthesised, their photo- and electrochemical properties were studied in detail, before testing their activity with respect to catalytic CO2 reduction. The most remarkable result comes from the unique ability of these species to release one of their carbonyl ligands in a controlled fashion, which led to the discovery of novel Mn dicarbonyl complexes which are selective catalysts for CO2 reduction, and also to new molecules which are applicable in the release of small quantities of CO for therapeutic purposes.Chapter III covers the study of the complex [Mn(phen-dione)(CO)3(X)]n+ (X = Br, n = 0 ou CH3CN, n = 1). This complex was synthesised with the aim in mind of obtaining complexes soluble in aqueous media. While this objective was ambitious, it was soon found that these species showed no catalytic activity for CO2 reduction in the target aqueous medium. Nevertheless, electrocatalytic activity was demonstrated in hydro-organic media and photocatalytic applications in organic media proved promising. This work allowed us to gain a better understanding of the physicochemical properties and catalytic mechanisms of a Mn complex containing a redox-active ligand.The results presented in Chapter IV are based on the study of another new Mn carbonyl complex family. The study concentrated mainly on the complex [Mn(pyperNH)(CO)3(CH3CN)]+. The pyperNH ligand, with its aromatic system and NH functional group, plays a major role and is redox-active. After a section dedicated to its synthesis and characterisation, this chapter devotes a large part to the role that different experimental parameters can play on the efficiency of the catalytic CO2 reduction reaction. The Mn complexes described in this chapter have remarkable redox properties. A preliminary study of the catalytic activity of these complexes for CO2 reduction has allowed us to have an initial idea about the potential role of the N-H functional group of the ligand on the catalytic mechanism and reaction selectivity. This research was extended beyond the pyperNH ligand into a complex class of similar ligand structures, and the preliminary results obtained are original and promising, and open the way towards new perspectives
Dinh, Thi Ty Mai. "Développement de filières technologiques pour la réalisation de micro-supercondensateurs intégrés sur silicium." Toulouse 3, 2014. http://thesesups.ups-tlse.fr/2724/.
Full textThe recent advances in microelectronics have led, during the last decade, to the development of embedded systems, particularly wireless sensor networks. Many applications of these systems (industrial process optimization, traffic and environmental monitoring. . . ) have attracted the attention of researchers and investors. One of the main challenges limiting the implementation of these wireless sensor networks remains the autonomy of energy. Harvesting micro-devices extracting renewable energy from various ambient environmental sources (thermal, mechanical, solar energy) have received in this sense an increasing research interest in recent years, with the objective to obtain autonomous self-powered systems. The harvested energy is usually stored in micro-batteries. However, these devices have low power, limited lifetime and restricted operation temperatures. The use of micro-supercapacitors, as an alternative or a complementary device to micro-batteries, could overcome these limitations. In this thesis, we have focused on the development of technological fields to realize on-chip micro-supercapacitors, with good properties in terms of power and energy density, operating voltage, size and lifetime. High resolution micro-supercapacitors with high performance have been obtained in this thesis. Innovative electrolytes as gels allowed to develop all-solid-state micro-devices, which can be produced on a large scale. Ultra-high specific capacitance has been also obtained by combining materials of high specific surface and materials of high specific capacitance within an electrode. Finally, asymmetric micro-supercapacitors have been developed for extending the potential window and, therefore, improving the energy density of the micro-devices
Ryabova, Anna. "Électrocatalyse de la réduction de l'oxygène et du peroxyde d'hydrogène sur les oxydes de manganèse." Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAF011/document.
Full textManganese oxides are of great interest due to their catalytic activity towards the ORR (the oxygen reduction reaction) in alkaline media and can be used as noble metal-free materials for the cathode in liquid and polymer electrolyte alkaline fuel cells. The present thesis is devoted to the investigation of the ORR activity of manganese oxides. It was shown that Mn2O3 with bixbyite structure has a better catalytic activity toward the ORR in alkaline media than other investigated manganese oxide, the surface activity of Mn2O3 is only 4 times lower than that of Pt at an overvoltage of 0.3 V (RHE). The link between the structure of Mn oxides and the ORR activity is found: the specific ORR activity exponentially increases with the potential of the surface Mn(III)/Mn(IV) red-ox couple. To ensure the high electrocatalytic activity of Mn2O3, it is necessary to add carbon to the electrode composition, as well as to keep potential above 0.7 V (RHE)
Pu, Xiaoxue. "Thermomechanical study of the gigacycle fatigue behavior of pure iron and carbon-manganese steels : influence of chemical composition and microstructure on damage and crack initiation mechanism." Thesis, Paris 10, 2019. http://www.theses.fr/2019PA100051.
Full textThis work attempts to a better understanding of the fatigue damage in ferrite-pearlite steels in the Very High Cycle Fatigue (VHCF) domain. The influences of two parameters, pearlite phase percentage and free interstitial atoms percentage in solid solution, are investigated to understand dissipative mechanisms under 20 kHz high frequency fatigue loading. In-situ infrared thermography is carried out to record the temperature changes, while fractography studies and microscope observations are conducted to investigate the dissipative mechanism on the surface of specimens.For body centered cubic (BCC) materials, under high stress amplitudes, a sudden increase of the temperature occurs without a crack initiation and fracture. The inevitable temperature increase up to hundreds of degrees at high stress amplitudes, is caused mainly by the screw dislocations mobility, which is the key to explaining the observed fatigue behavior and thermal response of BCC structure under high frequency loading. Therefore, PSBs on surface and micro-voids in matrix emerge massively, accompanying with this abrupt temperature increase. These phenomena are considered as transition of deformation mechanism from thermal regime to athermal regime. At low amplitudes, few PSBs or surface roughness are still observed on the specimen surface. Through the cycles of PSB appearance on armco-iron, it’s found that PSBs are inclined to appear before 1x10(7)cycles, and PSB threshold lies below the conventional fatigue limit. The increase of pearlite phase content weakens the temperature elevation, and strengthens the fatigue properties. The presence of free interstitial atoms in steels results in appearence of a secondary temperature increase in the stabilized temperature part (100-200 degree). This behavior seems to be related to the interaction of edge dislocations with free interstitial atoms. Moreover, the remarkable hardening-softening-hardening phenomenon after the sudden temperature elevation to above 300 degree is thought as the interaction of multiplicated screw dislocations and free interstitial atoms
Belotteau, Jeanne. "Comportement et rupture d’un acier au C-Mn en présence de vieillissement sous déformation." Thesis, Châtenay-Malabry, Ecole centrale de Paris, 2009. http://www.theses.fr/2009ECAP0002/document.
Full textPas de résumé en anglais disponible
Loffreda, David. "Modélisation théorique de l'adsorption et de la réactivité de la molécule NO sur les surfaces de catalyseurs à base de palladium, de rhodium et d'alliages palladium-manganèse." Lyon 1, 1999. http://www.theses.fr/1999LYO10295.
Full textNguyen, Van Tang. "Nanostructured soft-hard magnetic materials with controlled architecture." Thesis, Le Mans, 2018. http://www.theses.fr/2018LEMA1007.
Full textAmong currently investigated rare-earth-free magnets, ferromagnetic τ-MnAl is a highly potential candidate as having promising intrinsic magnetic properties. In my thesis, Mn(Fe)AlC was synthesized by mechanical alloying method. Effects of carbon on microstructure and magnetic properties were systematically investigated. It was found that high purity of τ-MnAl(C) could be obtained at 2 at.% C doping, showing clearly stabilizing effect of carbon. Mn54.2Al43.8C2 has the best magnetic properties: magnetization at 2T M2T = 414 kAm-1, remanent magnetization Mr = 237 kAm-1, coercivity HC = 229 kAm-1, and |BH|max = 11.2 kJm-3. HC increased inversely with the crystallite size of τ phase and proportionally with C content. Moreover, first principle calculation showed both stabilizing effect and preferable interstitial positions of carbon in tetragonal τ-MnAl. Mn51-xFexAl47C2 (x= 0.25, 0.5, 1, 2, 4, 6) alloys were also synthesized by mechanical alloying method, showing high purity of τ phase up to 2 at.% Fe doping. Adding of Fe on MnAl(C) reduced both magnetization and TC but likely increased slightly HC. 57Fe Mössbauer spectrometry at 300K was used to probe local enviroment in ε-, τ-, β-, and γ2-MnFeAl(C). In which, γ2-, ε-, and β-MnFeAl(C) exhibited a quadrupolar structure while τ -Mn50.5Fe0.5Al47C2 spectrum showed a rather complex magnetic hyperfine splitting. The interaction between Fe and Mn examined by in-field Mössbauer measurement at 10 K and 8 T showed a non-collinear magnetic structure between Fe and Mn with different canting angles at different sites. Hyperfine field of MnFeAl alloy calculated by Win2k supported both magetic properties and Mossbauer results
Didot, Alexandre. "Corrosion sous contrainte des aciers non alliés dans les conditions du stockage géologique." Compiègne, 2008. http://www.theses.fr/2008COMP1787.
Full textThe aim of this study is to evaluate the risk of stress corrosion cracking (SCC), in the conditions of the nuclear waste storage in deep geological layer, on the carbon steels which are postpone for the construction of the lining and the canisters. References, regarding the SCC susceptibility of buried pipelines, show two types of SCC, trans- and intergranular, which are related to two potential - pH domains. Usually, transgranular SCC is attributed to hydrogen embrittlement mechanism and intergranular SCC to film rupture processes. Slow strain rate tests (SSRT) were performed in order to identify SCC susceptibility domains on samples extracted from prototypes representatives of the canisters. As SSRT tests overestimate the potential SCC susceptibility, a one year duration experiment was carried on to evaluate the materials resistance toward crack initiation under static loads representatives of residual stresses. SCC tests results did not allow us to exclude, as regards to the expected chemical conditions, intergranular SCC risks. Nevertheless, we observed delayed cracking caused by the poor quality of the selected steels which are far from the usual recommendations specified for buried pipelines. Thus, a dedicated experimental program, for this deep geological storage, is set up to assess carbon steel selection compliant with existing specifications
Trillat, Jean-Frédéric. "Réduction de NO par CO sur catalyseurs bimétalliques Pd-Mn : application à la conversion de mélanges complexes en post-combustion automobile (moteurs à essence)." Lyon 1, 1997. http://www.theses.fr/1997LYO10029.
Full textRAMIREZ-SALGADO, JOEL. "Contribution à l'étude des électrodes à gaz dans un capteur potentiométrique à CO2 de deuxième espèce." Université Joseph Fourier (Grenoble), 2001. http://www.theses.fr/2001GRE10113.
Full textBouchard, Michel. "Evaluation des Capacités de la Microscopie Raman dans la Caractérisation Minéralogique et physicochimique de Matériaux Archéologiques : Métaux, Vitraux & Pigments." Phd thesis, Museum national d'histoire naturelle - MNHN PARIS, 2001. http://tel.archives-ouvertes.fr/tel-00131055.
Full textévidence, par exemple, les capacités de la MR à distinguer les oxydes de Mn du carbone dans les peintures noires préhistoriques ou encore, la facile identification de l'hématite ; ils permettent également de distinguer assez facilement les différentes phases
d'altérations existantes sur les métaux corrodés (sulfates, oxydes, chlorures...). Enfin, si l'étude du verre et des colorations en surface offrent des résultats assez positifs (complexes de type : PbCrO4.PbO), l'identification de la coloration dans la masse des vitraux par des colloï des métalliques reste plus complexe. La fluorescence constitue
également un des désavantages certain de cette méthode. Toutefois, la réussite de cette technique, dans le domaine de l'archéometrie, où elle est encore peu appliquée, permet d'entrevoir un avenir prospère et une utilité incontestable pour les archéologues,
restaurateurs et conservateurs.
Wisniewski, Sandra. "Etude et mise en oeuvre de catalyseurs de type perovskite dans un procédé de dénoxification d'effluents gazeux, en présence d'oxygène." Compiègne, 2000. http://www.theses.fr/2000COMP1282.
Full textWu, Jianxiong. "Développement de nouveaux matériaux catalytiques à faible teneur en métaux précieux pour le post-traitement des gaz d'échappement automobiles." Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1R021/document.
Full textThe current study aims to develop novel catalytic materials for the post-treatment of exhaust gas stemming from gasoline engines. The Three Way Catalyst (TWC) is generally considered as a mature and reliable technology capable of removing simultaneously the main pollutants present in the automobile exhaust gas: CO, HC and NOx. The existing TWC system relies heavily on the significant use of Platinum Group Metals (PGMs) and Rare Earth Elements (REEs). However, the high-cost and scarcity of the conventional PGM-based TWC system constitutes an obstacle for the cost reduction of exhaust gas treatment technology as well as a severe burden on natural resource. Another drawback of conventional TWC is associated with the sintering of precious metals in the process of catalyst operation and unsatisfactory N2 selectivity during NOx reduction. Therefore, alternative solutions are required which should ideally allow a substantial reduction of PGMs usage without sacrificing significantly the catalytic performance. Trois voiesThe goal of this study is to evaluate the feasibility of applying perovskite-type materials as an alternative to the replacement of conventional TWC system. The main approach employed is composition optimization of perovskite-type materials, including creation of non-stoichiometry in the chemical composition, partial substitution in A or B site and addition of small amount of PGMs. Influence of partial substitution in A or B site as well as the synergistic effect of dual substitutions in both A and B site were investigated. Results showed that Cu doping in B site could enhance oxidation of CO and C3H6 while Mn doping had a noticeable promoting impact on NO reduction under stoichiometric conditions. Small amount of PGM loading combined with doping of Cu or Mn could enhance remarkably the redox properties of the lanthanum ferrite perovskite. Ca doping in A site affected the dispersion and diffusion of precious metals across the perovskite substrate. The PGM-loaded perovskite catalysts outperformed the commercial benchmark catalyst in terms of higher NO conversion and N2 selectivity in stoichiometric condition in the operating temperature range of the TWC system but the deNOx activity during cold-start process remains a big challenge
Huang, Zhiyong. "Endommagement des aciers au C-Mn en fatigue oligocyclique et gigacyclique." Thesis, Paris 10, 2010. http://www.theses.fr/2010PA100088.
Full textIn steam generators of nuclear power plants, typical pipes components are subjected to thermal and mechanical loading which are variable and divided into two different regimes: low cycle fatigue and gigacycle fatigue. Carbon-manganese steels A42, A48 and Tu48 steels (French standards) are often used in such applications. The material properties manifest some special characters in mechanics and metallurgy such as Dynamic Strain Aging, increasing UTS values in 200℃ temperature domain. The LCF and VHCF behaviors are investigated respectively by test method at room temperature and 200℃. The cumulative fatigue tests are implemented through referencing the load as prior LCF following gigacycle fatigue from the steam generator pipes thermal loads in order to obtain the performance of material under accumulated fatigue damage. All the test results are analyzed by using plastic mechanics, continuums damage mechanics and microscopic analysis. Hysteresis loops are due to plastic deformation in LCF which is the effect of kinematic hardening and they can be described by Armstrong – Frederick form models; the isotropy hardening is used to predict the evolution of stress amplitude in LCF. But with rising of accumulated plastic deformation, the damage can not be neglected. The Chaboche fatigue damage model is applied to describe the damage evolution of LCF and extended to VHCF regime. The cumulative fatigue damage model is extended from Chaboche model and applies to the estimation cumulative fatigue damage. The constitutive relationship and isotropy rule are coupled with fatigue damage model that can describe the whole fatigue behavior. In 200℃ for LCF, A48 is sensitive to dynamic strain aging and its secondary hardening behavior is important which can be predicted by dislocation theory and is simulated in the paper. The fractographic analysis is performed by SEM for LCF, VHCF and cumulative fatigue tests. The LCF crack is initiated in surface. Some of cracks of VHCF are given birth from the inclusions located at interior of sample
Roche, Ivan. "Catalyseurs de piles à combustible à membrane polymère échangeuse anionique." Grenoble INPG, 2007. http://www.theses.fr/2007INPG0010.
Full textThe electrocatalytic properties of materials for electrodes of Alkaline Fuel Cell were studied with their composition and morphology. Dispersed silver nanoparticles were synthesized by chemical Impregnation on various commercial carbons: the catalysts Ag/Monarch 1000 exhibit better massic activites towards the Oxygen Reduction Reaction (ORR) than the benchmark Ag/Vulcan XC72 (E-TEK). MnOx nanoparticles were also synthesized by chemical deposition on carbon. Me-doped (Me = Ni, Mg) MnOx/C exhibit ORR activity close to the benchmark catalyst 10 wt. % Pt/C (E-TEK), and yield quantitative formation of OH- (4-electron pathway). An ORR mechanism on MnOJC is suggested
Chen, Yu-Wen, and 陳昱文. "Investigation on the Synergistic Effect of Niobium Composite Carbide in Low Carbon Bainitic Steels and High Manganese Twinning-Induced Plasticity Steels." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/a4y5w6.
Full text國立臺灣大學
材料科學與工程學研究所
106
Low carbon steels have been wildly used in line pipes, the automotive industry, and submarine environments due to their remarkable mechanical properties, weldability and formability. In the 2000s, micro-alloying elements were added into low carbon steels to further enhance the performance and meet increasing demand. In the present study, the performance of low carbon steels and TWIP steels is enhanced by the addition at least two strong carbide forming elements, appropriate heat treatment and microstructure control. The effects of Nb accompanied with other strong carbide forming elements in BCC and FCC matrix are investigated through microstructural observations with optical microscopy, scanning electron microscopy, transmission electron microscopy, and mechanical property tests. The relationships between mechanical properties and microstructure are clearly illustrated in this study. Chapter 4 presents an efficient and accurate method for microstructural quantification of complex phases in a low carbon Nb-Mo bearing steel. Optical micrographs showed that this steel consisted of granular bainite with a small amount of ferrite and degenerated pearlite. In our previous work, we proposed a method to measure the misorientation angles via electron backscatter diffraction (EBSD) so as to differentiate granular bainite and ferrite. That method is accurate for phase quantification but laborious for the characterization process. To resolve this difficulty, in this study, EBSD was used in combination with a kernel average misorientation (KAM) map for phase characterization. Comparisons were made among KAM maps with different kernel sizes (300 to 600 nm) and various step sizes (100 to 600 nm). It is found that a kernel size close to the sub-structure size of granular bainite (500 nm) is optimal for phase identification, while varied step sizes produce relatively invariant results. Therefore, KAM maps can be used for fast and reliable phase quantification, provided that an appropriate kernel size and a large step size are used. Chapter 5 describes an investigation of the effects of tempering at three high temperatures (660, 680 and 700 ºC) for different holding times (5 min to 16 h) on the secondary hardening in Nb-bearing and Nb-Mo-bearing bainitic steel strips. It is found that with 0.3 wt.% Mo addition in Nb-Mo-bearing bainitic steel strip, the peak hardening occurs with a significant increment in hardness (up to 40 Hv) after approximately 10 min of tempering at all temperatures (660, 680 and 700 ºC). In contrast, for the Nb-bearing steel strip, the corresponding increment in hardness is small (about 15 Hv). Investigations of the microstructural evolutions of Nb-bearing and Nb-Mo-bearing steel strips during tempering at 700 ºC are also presented. It is found that during tempering, bainitic ferrite platelets in Nb-Mo-bearing steel strips remain much more stable and have a higher dislocation density than those in Nb-bearing steel strips. High-resolution transmission electron microscopy provides strong evidence that the Mo addition has significant effects on suppressing the annihilation rate of dislocations and retarding the coarsening rate of nanometer-size carbide particles at higher temperatures, leading to a remarkable resistance to softening after secondary hardening. In chapter 6, the microstructure evolution and mechanical properties of twinning-induced plasticity (TWIP) steel subjected to high temperature aging are elucidated. The yield stress and ultimate tensile stress of 18Mn-0.4C TWIP steel respectively increase by 46 MPa and 146 MPa after 700 ºC aging. Microstructural characterizations conducted to clarify the increments in strength are also presented. The as-received TWIP steel contained dense and homogeneously distributed dislocations, which, after aging, rearranged themselves into a lath-like sub-structure without obvious annihilation. In addition, the number density of precipitates was higher in the aging than in the as-received TWIP steel sheet. Ductile fracture surfaces were found both in the aging and as-received TWIP steel, and the deformation structures were investigated using transmission electron microscopy. In the as-received TWIP steel, austenite grains were dominated by single-variant primary mechanical twins, and few secondary twins were found. On the other hand, in the aging TWIP steels, a high amount of multiple-variant nano-sized mechanical twins with some strain-induced α’ martensite in the intersections was found. It is appropriate to conclude that after aging, the presence of a high amount of precipitates retards the formation of deformation twins, causing premature saturation of single-variant mechanical twins. Therefore, more secondary mechanical twins are activated, and they in turn interact with the primary twins as strain increases, inducing α’ martensite formation in the intersection. This phenomenon increases the strain hardening rate at a late stage (εe = 0.41) and thus the ultimate tensile stress in the aging TWIP steel.
Bezuidenhout, Daniela Ina. "Synthesis and Structural Investigations of manganese carbene complexes." Diss., 2006. http://hdl.handle.net/2263/28193.
Full textDissertation (MSc)--University of Pretoria, 2007.
Chemistry
unrestricted
Pinto, M. F. "Manganese and Iron Complexes with H-heterocyclic Carbene Ligands: Synthesis and Catalysis." Doctoral thesis, 2020. http://hdl.handle.net/10362/97198.
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