Letteratura scientifica selezionata sul tema "Oxyde de lanthane (La2O3)"
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Articoli di riviste sul tema "Oxyde de lanthane (La2O3)"
1
Karthikeyan.S e Selvapandiyan.M. "Facile synthesis of nanoplates and nanoflower shaped La2O3 nanostructures by Reflux Route". INTERNATIONAL JOURNAL OF SCIENCE TECHNOLOGY AND HUMANITIES 2, n. 2 (30 ottobre 2015): 95–98. http://dx.doi.org/10.26524/ijsth64.
Testo completoAbstract (sommario):
Lanthanum Oxide (La2O3 ) nanoparticles are successfully synthesized by simple reflux method using starting materials Lanthanum Nitrate and Urea. Lanthanum Oxide (La2O3 ) have multiple applications such as gas sensors, catalyst, Hydrogen storage, catalysts, photocatalytic wet oxidation etc. This paper mainly focuses on the synthesis of Lanthanum Oxide (La2O3 ) nanoparticles at different precursor concentration at different reaction time on the properties of the synthesized Lanthanum Oxide (La2O3) nanoparticles can be explored. The synthesized samples were calcinated 500ºC for 1hr. The Lanthanum Oxide (La2O3) nanoparticles were investigated by XRD, FTIR, SEM, & UV studies. The morphology and particle size were analyzed by SEM. The structure of the crystallites was investigated using powder XRD technique. The FTIR analysis was used to examine the functional groups present in the synthesized Lanthanum Oxide (La2O3) nanoparticles. The optical band gap was calculated from the UV-Vis absorption spectra
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Karthikeyan.s, Divya.j, Selvapandiyan.M e Arumugam.J. "Synthesis of Nickel Oxide Thin Films via Sol Gel Route". INTERNATIONAL JOURNAL OF SCIENCE TECHNOLOGY AND HUMANITIES 2, n. 2 (30 ottobre 2015): 99–101. http://dx.doi.org/10.26524/ijsth65.
Testo completoAbstract (sommario):
Lanthanum Oxide (La2O3) nanoparticles are successfully synthesized by simple reflux method using starting materials Lanthanum Nitrate and Urea. Lanthanum Oxide (La2O3) have multiple applications such as gas sensors, catalyst, Hydrogen storage, catalysts, photocatalytic wet oxidation etc. This paper mainly focuses on the synthesis of Lanthanum Oxide (La2O3) nanoparticles at different precursor concentration at different reaction time on the properties of the synthesized Lanthanum Oxide (La2O3) nanoparticles can be explored. The synthesized samples were calcinated 500ºC for 1hr. The Lanthanum Oxide (La2O3) nanoparticles were investigated by XRD, FTIR, SEM, & UV studies. The morphology and particle size were analyzed by SEM. The structure of the crystallites was investigated using powder XRD technique. The FTIR analysis was used to examine the functional groups present in the synthesized Lanthanum Oxide (La2O3) nanoparticles. The optical band gap was calculated from the UV-Vis absorption spectra.
3
Upolovnikova, A. G., A. A. Babenko e L. A. Smirnov. "Equilibrium content of lanthanum in metal under the slag of СаО – SiO2 – La2O3 – 15 % Al2O3 – 8 % MgO system". Izvestiya. Ferrous Metallurgy 63, n. 11-12 (3 gennaio 2021): 946–51. http://dx.doi.org/10.17073/0368-0797-2020-11-12-946-951.
Testo completoAbstract (sommario):
Thermodynamic modeling results of lanthanum equilibrium content in metal under the slag of CaO – SiO2– La2О3– Al2O3– MgO system corresponding to chemical composition of 16 points of local simplex plan are presented using the HSC 8.03 Chemistry (Outokumpu) software package in combination with the simplex planning lattice method. In the work, slag is represented by CaO – SiO2– La2O3– – 15 % Al2O3– 8 % MgO oxide system in a wide range of chemical composition for temperatures of 1550 and 1650 °C, and metal contains 0.06 % C, 0.25 % Si, 0.05 % Al (in this expression and hereinafter in mass.%). The results of mathematical modeling are shown graphically in the form of composition - equilibrium content diagrams of lanthanum. There is significant effect of slag basicity on the lanthanum equilibrium content in metal. An increase in slag basicity from 2 to 5 at temperature of 1550 °C leads to an increase in the lanthanum equilibrium content from 0.2 ppm in the region of lanthanum oxide concentration of 1 – 5 % to 7 ppm in the region of increased concentration of lanthanum oxide to 4 – 7 %, hence the increase in slag basicity favorably affects development of lanthanum reduction. Increase in metal temperature also has positive effect on lanthanum reduction process. As temperature rises to 1650 °C, the lanthanum equilibrium content in metal increases from 0.2 ppm in the region of lanthanum oxide concentration of 1 – 3 % to 12 ppm in the region of increased concentration of lanthanum oxide to 4 – 7 %. In diagrams of chemical composition of slag containing 56 – 61 % CaO, 12 – 14 % SiO2and 4 – 7 % La2O3, the lanthanum content in metal at level of 7 – 12 ppm is ensured in temperature range from 1550 to 1650 °C. Therefore, there can be confirmed a decisive role of slag basicity, concentration of lanthanum oxide and temperature factor in development of lanthanum reduction from slags of the studied oxide system by aluminum dissolved in metal.
4
Upolovnikova, A. G., A. A. Babenko e L. A. Smirnov. "Equilibrium content of lanthanum in metal under the slag of СаО – SiO2 – La2O3 – 15 % Al2O3 – 8 % MgO system". Izvestiya. Ferrous Metallurgy 63, n. 11-12 (3 gennaio 2021): 946–51. http://dx.doi.org/10.17073/0368-0797-2020-11-12-946-951.
Testo completoAbstract (sommario):
Thermodynamic modeling results of lanthanum equilibrium content in metal under the slag of CaO – SiO2 – La2О3 – Al2O3 – MgO system corresponding to chemical composition of 16 points of local simplex plan are presented using the HSC 8.03 Chemistry (Outokumpu) software package in combination with the simplex planning lattice method. In the work, slag is represented by CaO – SiO2 – La2O3 – – 15 % Al2O3 – 8 % MgO oxide system in a wide range of chemical composition for temperatures of 1550 and 1650 °C, and metal contains 0.06 % C, 0.25 % Si, 0.05 % Al (in this expression and hereinafter in mass.%). The results of mathematical modeling are shown graphically in the form of composition - equilibrium content diagrams of lanthanum. There is significant effect of slag basicity on the lanthanum equilibrium content in metal. An increase in slag basicity from 2 to 5 at temperature of 1550 °C leads to an increase in the lanthanum equilibrium content from 0.2 ppm in the region of lanthanum oxide concentration of 1 – 5 % to 7 ppm in the region of increased concentration of lanthanum oxide to 4 – 7 %, hence the increase in slag basicity favorably affects development of lanthanum reduction. Increase in metal temperature also has positive effect on lanthanum reduction process. As temperature rises to 1650 °C, the lanthanum equilibrium content in metal increases from 0.2 ppm in the region of lanthanum oxide concentration of 1 – 3 % to 12 ppm in the region of increased concentration of lanthanum oxide to 4 – 7 %. In diagrams of chemical composition of slag containing 56 – 61 % CaO, 12 – 14 % SiO2 and 4 – 7 % La2O3 , the lanthanum content in metal at level of 7 – 12 ppm is ensured in temperature range from 1550 to 1650 °C. Therefore, there can be confirmed a decisive role of slag basicity, concentration of lanthanum oxide and temperature factor in development of lanthanum reduction from slags of the studied oxide system by aluminum dissolved in metal.
5
Han, Hong Jing, Yan Guang Chen, Cong Hao Xie, Dan Dan Yuan, Ying Chen e Bao Hui Wang. "Influence of La2O3 on NOx Emission in Iron Ore Sintering". Advanced Materials Research 781-784 (settembre 2013): 2594–97. http://dx.doi.org/10.4028/www.scientific.net/amr.781-784.2594.
Testo completoAbstract (sommario):
NOx emission in coke combustion with and without La2O3 was investigated in a fixed bed quartz reactor. The effects of La2O3 loading and lanthanum oxide particle size on NOx emission were discussed. NOx emission was also studied by sintering pot tests with lanthanum oxide modified coke as sintering fuel. The results showed that lanthanum oxide was catalytically active in promoting not only coke combustion but also NOx reduction. In coke combustion experiments, NOx and CO emission decreased with increasing lanthanum oxide loading up to 2.0wt% and decreasing lanthanum oxide particle size (28~150μm).
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Sun, Yunhan, Xiaoning Wang, Qingxiu Jia e Jian Yang. "Study on Organic Modification of Lanthanum Oxide". Journal of Physics: Conference Series 2194, n. 1 (1 febbraio 2022): 012032. http://dx.doi.org/10.1088/1742-6596/2194/1/012032.
Testo completoAbstract (sommario):
Abstract In this paper, lanthanum oxide was modified by silane coupling agent (KH560), titanate coupler NDZ-201 and dopamine hydrochloride (DP). The microstructure and chemical structure of modified La2O3 were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), and the dispersion of modified lanthanum oxide in polypropylene (PP) was investigated. The results show that the three modifiers can improve the organic properties of lanthanum oxide, and the interfacial compatibility between dopamine modified La2O3 and PP is better than the other two modifiers.
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Sun, Yunhan, Xiaoning Wang, Qingxiu Jia e Jian Yang. "Preparation of modified rare earth lanthanum oxide/polypropylene nonwoven fabric by meltblown method". Journal of Physics: Conference Series 2194, n. 1 (1 febbraio 2022): 012046. http://dx.doi.org/10.1088/1742-6596/2194/1/012046.
Testo completoAbstract (sommario):
Abstract Lanthanum oxide was organically modified with dopamine and blended with polypropylene, and then lanthanum oxide (La2O3)/polypropylene (PP) nonwovens were prepared by melt blown method. The nonwovens were characterized by FTIR, SEM, TG, mechanical properties and X-ray shielding. The experimental results show that the addition of modified La2O3 makes the fiber arrangement of PP nonwovens more densely arranged and improves the thermal stability of PP nonwovens. The higher the amount of La2O3, the better the X-ray shielding performance of composite nonwovens.
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Samin, Samin, Suyanti Suyanti, Susanna Tuning Sunanti e Wisnu Ari Adi. "Synthesis and Certification of Lanthanum Oxide Extracted from Monazite Sand". Indonesian Journal of Chemistry 20, n. 6 (5 ottobre 2020): 1213. http://dx.doi.org/10.22146/ijc.44327.
Testo completoAbstract (sommario):
Synthesis and certification of lanthanum oxide extracted from monazite sand have been carried out. This research aimed to increase the added value of monazite sand and obtain the lanthanum oxide in-house certified reference material (CRM). Synthesis of lanthanum oxide consists of several stages, namely: monazite sand digestion, rare-earth elements hydroxide [REE(OH)3] precipitation, Ce separation, Nd separation, lanthanum oxalate precipitation, and calcination. Certification of lanthanum oxide was carried out by determining the average concentration of the oxides and its uncertainty from the seven accredited laboratories by the ISO 35-2006 statistical method. Two other minerals in the lanthanum oxide analyzed by the XRD method were cerium hydroxide [Ce(OH)3] and neodymium yttrium oxide fluoride (Nd2Y2O3F16). Lanthanum oxide certified contains ten oxides, with the two highest concentrations of La2O3 (91.662 ± 0.007)% and Nd2O3 (3.949 ± 0.002)%. Lanthanum oxide has met the qualification in-house CRM since it contained water less than 1%, was homogeneous, stable, and certified. La2O3 concentration in the lanthanum oxide in-house CRM from CSAT-BATAN, Indonesia was not significantly different in comparison to that from the Department of Chemical Engineering, Srinakharinwirot University, Thailand. Lanthanum oxide extracted from monazite sand can be used as reference material in determining the lanthanum oxide quality from the pilot plant process.
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Nirlakalla, Ravi, R. Ravanamma, K. Muralidhara Reddy e R. Padma Suvarna. "Structure and Dielectric Studies of Lanthanum Oxide Activated Niobium-Barium Titanate for Energy Storage Applications". ECS Transactions 107, n. 1 (24 aprile 2022): 19505–15. http://dx.doi.org/10.1149/10701.19505ecst.
Testo completoAbstract (sommario):
A 10 mol% of La2O3 doped niobium-barium titanate (60-y) BaO –(40-x) TiO2 – y Nb2O5 – La2O3x (BTNb10La10) (where x = y = 10), BTNb10 and BTLa10 ferroelectric ceramics were prepared by solid state reaction, those are sintered at temperatures 1000 oC for 8 h and calcined at 1250 oC for 6 h to investigate various properties such as structure, morphology and dielectric that include electric hysteresis. Different phases of the BTNb10La10 ceramics were revealed and identified in XRD profile. La–O bending vibration band was identified at 541 cm-1 in the FTIR spectra of BTNb10La10 samples. A broad phonon vibrational Raman band was identified at 770 cm-1of BTNb10La10 ceramics due to the presence of La2O3. 132, 143 and 148 nm are the average particle sizes revealed in scanning electron microscope (SEM) for BTNb10, BTLa10 and BTNb10La10ferroelectrics, respectively. The recoverable energy storage density (Wrec) of the BTNb10La10 ferroelectric is found to be Wrec = 0.3370 J/cm3 with an energy storage efficiency of η = 94%. The slim and antiferroelectric features of electric hysteresis indicates that the BTNb10La10 ferroelectric could be a potential candidate for energy storage pulsed capacitor applications.
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Lu, Victor M., e Kerrie L. McDonald. "Lanthanum nanoparticles to target the brain: proof of biodistribution and biocompatibility with adjuvant therapies". Nanomedicine 15, n. 22 (settembre 2020): 2107–17. http://dx.doi.org/10.2217/nnm-2020-0165.
Testo completoAbstract (sommario):
Aim: To determine the biodistribution of lanthanum (III) oxide (La2O3) nanoparticle (NP) therapy to the brain and its biocompatibility with radiation therapy (RT) and chemotherapy (CT). Materials & methods: Healthy balb/c nude mice were administered 4 weekly doses of La2O3 NP therapy via tail vein injection. Organ weights and lanthanum concentrations were evaluated. Results: La2O3 NP penetrated the brain. Concentrations were found to peak in the brain at 24 h after injection and persisted at 8 weeks after injection. Neither RT nor CT affected biodistribution. No adverse events or safety concerns in other organs were noted. Conclusion: La2O3 NP can reach the brain to target neurological disease and is biocompatible with RT and CT in a biological system.
Tesi sul tema "Oxyde de lanthane (La2O3)"
1
Abbadi, Meryem. "Synthèse et caractérisation de solutions solides ZnO/CeO2 et CeO2/La2O3/ZnO pour la minéralisation photocatalytique du diclofénac de sodium en solution aqueuse". Electronic Thesis or Diss., Strasbourg, 2024. http://www.theses.fr/2024STRAF019.
Testo completoAbstract (sommario):
La présence de résidus pharmaceutiques dans les milieux aquatiques est une préoccupation majeure. Parmi ceux-ci, le diclofénac de sodium est un anti-inflammatoire non stéroïdien détecté dans les eaux usées. Parmi les méthodes de traitement de ces eaux, la photocatalyse hétérogène constitue une méthode efficace et prometteuse. Comparé au TiO2, largement utilisé en photocatalyse, le ZnO est une alternative présentant une activité photocatalytique intéressante sous irradiation UV. Cependant, son activité photocatalytique est atténuée par une recombinaison de charge plus rapide et une mauvaise séparation des paires électron-trou sous irradiation visible, et sa sensibilité à la photo-corrosion limite sa capacité à minéraliser les polluants récalcitrants sous rayonnement UV-visible. Afin d'améliorer l’activité photocatalytique du ZnO dans la région visible, son association avec des espèces métalliques est très attractive. Pour cela, nous avons opté pour l’oxyde de cérium CeO2 considéré comme un bon accepteur d’électrons et un excellent support de stockage d’oxygène en dehors de sa grande stabilité thermique et sa non-toxicité. Des matériaux de la solution solide Ce1-xZnxO2-x lacunaires en oxygène ont été préparés par voie de chimie douce en présence d’acide citrique et caractérisés par diverses techniques. L'insertion du cérium génère des lacunes en oxygène et des sites actifs responsables d'une meilleure minéralisation photocatalytique du diclofénac sous la lumière visible. Ensuite, nous avons synthétisé des composés ternaires CeO2/La2O3/ZnO et leur activité photocatalytique a été évaluée sous irradiation solaire pour la dégradation du diclofénac. Les résultats ont montré que l’addition de lanthane au sein de la solution solide Ce1-xZnxO2-x permet d’améliorer d’avantage la minéralisation photocatalytique du diclofénac dans l’eauThe presence of pharmaceutical residues in aquatic environments is a major concern. Among these, diclofenac sodium is a non-steroidal anti-inflammatory drug detected in wastewater. Among the methods of water treatment, heterogeneous photo catalysis constitutes an effective and promising method. Compared to TiO2, widely used in photo catalysis, ZnO is an alternative, which presents an interesting photocatalytic activity under UV irradiation. However, its photocatalytic activity is attenuated by faster charge recombination and poor separation of electron-hole pairs under visible irradiation, and its sensitivity to photo-corrosion limits its ability to mineralize recalcitrant pollutants under UV-visible radiation. In order to improve the photocatalytic activity of ZnO in the visible region, its association with metallic species is very attractive. For this, we opted for cerium oxide CeO 2 considered a good electron acceptor and an excellent oxygen storage medium apart from its great thermal stability and non-toxicity. Ce1-xZnxO2-x materials were prepared by soft-chemistry in the presence of citric acid, and characterized by various techniques. The insertion of cerium generates oxygen vacancies and active sites responsible for better photocatalytic mineralization of diclofenac under visible light. Then, we synthesized CeO2/La2O3/ZnO ternary compounds and their photocatalytic activity was tested under solar irradiation for the degradation of diclofenac. The results showed that the addition of lanthanum to the Ce1-xZnxO2-x solid solution further improves the photocatalytic mineralization of diclofenac in water
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Blech, Vincent. "Analyse corrélée du plasma de pulvérisation et des films minces de La2O3 et de RuO2 pour les futurs transistors MOSFET". Paris 11, 2004. http://www.theses.fr/2004PA112040.
Testo completoAbstract (sommario):
Afin d'accroître la puissance de calcul et la rapidité des circuits intégrés, l'industrie de la micro électronique n'a cesse de miniaturiser les composants élémentaires logiques: les transistors à effet de champ (MOSFET). Cette miniaturisation conduit à une limitation fondamentale: sous 2 nm, le diélectrique de grille de SiO2 est fortement perméable aux courants tunnel. Une solution consiste à déposer des films plus épais d'un diélectrique à "forte permittivité" (e > 15). Nous avons étudié les propriétés physico-chimiques et électriques de films minces de La2O3 (e ~30) déposés par pulvérisation cathodique magnétron afin de tester les possibilités d'intégration d'un tel diélectrique dans les MOSFET. Le matériau étant fortement hygroscopique, il faut éviter tout contact avec l'air, ce qui a été réalisé en l'encapsulant sous un film mince protecteur de Ru ou de ZrO2. De plus l'utilisation de la cible de pulvérisation est également rendue complexe par l'instabilité chimique de La2O3: nous avons étudié un procédé de prépulvérisation adapté de la cible qui permet d'obtenir des films minces reproductibles. La seconde partie de cette thèse traite de l'oxyde de ruthénium RuO2, utilisé comme électrode de grille métallique pour réaliser des structures métal-isolant-semiconducteur, nécessaires à l'étude des propriétés électriques des films de La2O3. Les films minces de RuO2 étant obtenus par pulvérisation cathodique en milieu réactif (argon + oxygène), nous avons étudié le plasma (par spectroscopie d'émission optique, ou SOE) ainsi que les films minces obtenus, en fonction du débit d'oxygène. La corrélation de ces mesures permet d'une part une meilleure compréhension des mécanismes de croissance de RuO2 en pulvérisation réactive et, d'autre part, laisse envisager la possibilité d'utiliser la SOE comme un moyen de contrôle du dépôt, bon marché, en temps réel et in-situ. Enfin les caractérisations électriques des hétérostructures Si/La2O3/RuO2, encapsulées sous ZrO2, révèlent que La2O3 possède une permittivité de ~20, et qu'un film de 4. 5 nm (possédant une épaisseur équivalente de SiO2 de 3 nm) donne des courants de fuite de 10^-6 A. Cm^-2 pour une tension de grille de 1V. Enfin nous avons estimé les densités d'états électroniques et de charges fixes dans la zone interfacialeIn order to increase the calculation power and speed of integrated circuits, semiconductor industry has continuously scaled down its elementary components: the field effect transistors, so called MOSFETs. Such scaling down leads to a fundamental limitation: for a SiO2 gate dielectric thinner than 2 nm, high direct tunnel current appears to dramatically alter the behaviour of the transistor. To solve this problem, high dielectric constant (high-K, i. E. K > 15) dielectrics are needed. We studied the physical and electrical properties of La203 (K~30) thin films deposited by magnetron sputtering, in order to evaluate its compatibility with the industrial process of MOSFETs fabrication. This material is highly reactive with water molecules in air and, as a consequence, must be capped; such process could be achieved with Ru or ZrO2 cap layers. On the other hand, the use of the La2O3 sputtering target was also made complicated by its chemical instability. Thus, we studied a "pre-sputtering" process which allows obtaining reproducible thin films. The second part of this thesis is about ruthenium oxide RuO2, which was used as the metal gate electrode in metal-insulator- semiconductor structures, in order to study the electrical properties of La2O3 thin films. Since RuO2 thin films are deposited by reactive (Ar + O2) sputtering, we studied both properties of the plasma (with optical emission spectroscopy, or OES) and properties of thin films, as a function of O2 flux. The correlation of both measurements allows understanding the mechanisms of RuO2 growth in oxidizing atmosphere, as well as controlling the deposition process with OES, a non expensive, fast and in-situ technique. Moreover, the electrical characterization of Si/La2O3/RuO2 structures, capped with a ZrO2 film, show a dielectric constant of ~20 for La2O3, and leakage currents of 10^-6 A. Cm^-2 (at gate voltage = 1V) for a 4. 5 nm La2O3 film (which corresponds to an equivalent SiO2 thickness of 3 nm). To conclude, interface states density and fixed charge density in the dielectric film have also been estimated
3
Klettlinger, Jennifer Lindsey Suder. "Fischer-Tropsch Cobalt Catalyst Improvements with the Presence of TiO2, La2O3, and ZrO2 on an Alumina Support". University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1333981467.
Testo completo
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Lacombe, Sylvie. "Etude mécanistique du couplage oxydant du méthane sur oxyde de lanthane". Lyon 1, 1993. http://www.theses.fr/1993LYO10276.
Testo completoAbstract (sommario):
Le mecanisme du couplage oxydant du methane a ete etudie sur un oxyde de lanthane (caracterise par xps, ftir, xrd, tem, sem) en utilisant les techniques de cinetique rapide avec marquage isotopique sur reacteur dynamique (equilibre ch#4/cd#4, transitoires a l'etat stationnaire) et la technique pulsee sur reacteur tap. Le schema mecanistique suivant a ete propose. Le methane gazeux s'active soit reversiblement et heterolytiquement sur des sites acido-basiques la#3#+-o#2#, soit irreversiblement et homolytiquement sur des sites fortement basiques de type o# pour former un radical methyle. Les sites o# sont issus de l'activation dissociative de l'oxygene sur une paire (o#2#, lacune anionique). La grande mobilite de l'oxygene de reseau fait que ces sites ne sont pas localises. Le couplage des radicaux methyles en ethane s'opere en phase gaz et l'ethane peut etre deshydrogene par la suite en ethylene. L'origine du monoxyde de carbone est probablement liee a une oxydation en phase gaz des hydrocarbures. Le dioxyde de carbone provient de l'oxydation des radicaux methyles par une succession d'etapes de surface, faisant intervenir des groupements methoxy puis carbonates. Les sites impliques seraient des sites faiblement coordines, localises sur les defauts de structure des particules. Ce schema mecanistique a permis d'elaborer un schema cinetique general de la reaction, avec modelisation des equations cinetiques et optimisation des principaux parametres
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Petitjean, Marie. "Propriétés et réactivité de ferromanganites de lanthane strontium, cathodes de piles à combustible SOFC". Dijon, 2003. http://www.theses.fr/2003DIJOS057.
Testo completo
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Flandre, Xavier. "Nouvelles électrodes pour pile à combustible à oxyde solide et électrolyseur à haute température". Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10182/document.
Testo completoAbstract (sommario):
Dans le contexte actuel, les ressources en énergie fossiles diminuent et deviennent de plus en plus couteuses, se pose aussi le problème de l’environnement. Dans ce cadre, les piles à combustible à oxydes solides (Solid Oxide Fuel Cell en anglais, SOFC) sont une source d’énergie propre et alternative très prometteuse. Utilisé de façon réversible, ce système peut également permettre le stockage de l’électricité produite de façon intermittente via l’électrolyse de l’eau. Néanmoins, plusieurs verrous technologiques restent encore à lever en matière de performances et de durabilité des matériaux actuellement utilisés, notamment pour ce qui concernent les matériaux d’électrode. Dans ce travail de thèse de doctorat, notre contribution a porté sur deux matériaux de cathode de SOFC, Ba2Co9O14 et Ca3Co4O9+δ, et des composés dérivés de La4Ti2O10 pouvant présenter un intérêt comme matériau d’anode. Nous nous sommes intéressés plus particulièrement à la compréhension des mécanismes physico-chimiques intervenant au sein de ces matériaux en faisant appel à la spectroscopie d’impédance. Pour les cobaltites, cette étude a permis de mettre en évidence les paramètres limitants les performances électrochimiques. Elle aidera à l’optimisation de futures cellules complètes plus performantes. Pour les phases dérivées de La4Ti2O10, une étude par diffusion des neutrons a permis de confirmer les mécanismes de diffusion de l’oxygène au sein de ces matériaux. Leurs conductivités et propriétés catalytiques restent néanmoins insuffisantes pour pouvoir espérer les utiliser comme matériau d’anode, au contraire d’autres titanates de lanthane de structure perovskite lamellaireIn the current context, fossil energy resources decrease and become more expensive, in addition to environmental concern. In this frame, solid oxide fuel cells (SOFC) are a promising green alternative energy source. Reversibly used, this system can also allow storage of electricity produced intermittently through the electrolysis of water. However, several bottlenecks still remain in terms of performances and stability of materials currently used to improve their lifetime and decrease their working temperature. In this doctoral thesis, our contribution focused on two cathode materials for SOFCs, Ba2Co9O14 and Ca3Co4O9+δ, and compounds derived from La4Ti2O10 which may be relevant as anode material. Our study mainly focused on the understanding of the physicochemical mechanisms involved in these materials by using impedance spectroscopy. For cobaltites, this study has led to the identification of the limiting parameters and will help the future optimization of complete stacks with better performances. For the La4Ti2O10 derived phases with the cuspidine structure, a neutron scattering study confirmed the oxygen diffusion mechanisms in these materials. However, their conductivity and catalytic properties remain insufficient to hope to use these compounds as SOFC’s anode, unlike other lanthanum titanates which display a layered perovskite structure
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Guillot, Stéphanie. "Étude des paramètres principaux gouvernant les propriétés de conduction dans les apatites, électrolytes pour piles SOFC". Thesis, Lille 1, 2009. http://www.theses.fr/2009LIL10052/document.
Testo completoAbstract (sommario):
Cette thèse a pour objet l’élaboration et la caractérisation d’oxyapatite silicatées de lanthane, matériaux potentiellement utilisables comme électrolyte pour piles à combustible à oxyde solide. Des poudres et céramiques denses d’apatite de stœchiométries en oxygène et de compositions (substitutions) différentes ont été élaborées par réaction à l’état solide à haute température. Il ressort que quelque soit la composition, le paramètre principal qui gouverne les propriétés de conduction est la stœchiométrie en oxygène. La conductivité atteint 1,7 x 10-2 S.cm-1 à 700°C pour la composition La10Si5,5Mg0,5O26,5. La combinaison d’analyses spectroscopiques (Diffusion Raman, Résonance Magnétique Nucléaire) et de diffraction des neutrons a permis de définir un mécanisme de conduction des ions oxydes dans la structure. L’existence d’un site interstitiel localisé dans les canaux de la structure apatite en (-0,01, 0,04, 0,06) est confirmée. Un chemin de diffusion des ions oxyde de type « lacune sur le site 2a – atome interstitiel » est proposé le long de l’axe c. Ce mécanisme semble facilité par le déplacement des tétraèdres situés à la périphérie du canalThis work is devoted to the elaboration and the characterisation of apatite type lanthanum silicates as new electrolyte for SOFC fuel cells. Apatite powders and dense ceramics with different oxygen stoichiometries and compositions (substitutions) were prepared by high temperature solid state reaction. Whatever the composition, we can conclude that the key parameter which governs the conduction properties is the oxygen stoichiometry. The conductivity reaches 1.7 x 10-2 S.cm-1 at 700°C for the La10Si5,5Mg0,5O26,5 composition. By combining Raman spectroscopy, NMR and neutron diffraction, an oxide ion conduction mechanism was deduced. The existence of an interstitial site located at (-0.01, 0.04, 0.06) was confirmed. This allows to proposed a realistic oxygen diffusion pathway through this interstitial site along the c axis. Moreover, this mechanism seems to be facilitated by the displacement of tetrahedral located at the periphery of the oxide channels
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Bertrand, Gregory. "Films minces de manganites de lanthane (LaxMnyO 3 + δ) sur zircone yttriée ((100)YSZ) comme modèle de demi-pile à combustible à oxydes solides (SOFC) : élaboration par LP-MOCVD et propriétés interfaciales". Dijon, 2000. http://www.theses.fr/2000DIJOS036.
Testo completoAbstract (sommario):
Ce travail de thèse a pour objectif la réalisation d'un système modèle de demi-pile à combustible à oxydes solides (SOFC) adapté à l'étude de la réaction de dégradation à haute température de l'interface entre la cathode et l'électrolyte, respectivement LaMnO 3 (LM) et ZrO 2 : 9. 5 mol. % y 2o 3 (YSZ). Ces matériaux sont représentatifs de ceux utilisés dans la technologie SOFC fonctionnant dans un domaine de température compris entre 850 et 1000°C. Les performances et la durée de vie des piles dépendent fortement de la réactivité entre LM et YSZ qui est fonction du rapport cationique La/Mn. Ce travail a pour but de détecter la formation de la phase inhibitrice La2 Zr2 O7 (LZ) à l'interface cathode - électrolyte, en fonction du rapport La/Mn et d'en analyser les mécanismes de formation. Notre approche se singularise par le choix du procédé de synthèse en couche mince de la cathode, par sublimation contrôlée de précurseurs métalloorganiques solides ou LP-MOCVD. La synthèse directe à 600°C et l'utilisation d'un substrat monocristallin de YSZ a permis d'élaborer un système modèle idéal pour l'étude de la réactivité de l'interface LM/(100)YSZ. Cette phase de synthèse s'appuie sur une étude fondamentale des cinétiques de sublimation des précurseurs solides de La et de Mn permettant une optimisation du procédé de dépôt. La réactivité de ces assemblages a été abordée à partir de trois séries de compositions chimiques La/Mn choisies. La microscopie Auger à balayage associée à la diffraction électronique et la diffraction des rayons X en incidence rasante ont permis à la fois de préciser la chimie et les relations cristallographiques de l'interface. Des données concernant les produits de réaction et leur localisation en fonction de La/Mn et d’analyser les mécanismes de cette formation sont présentées.
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Lauret, Hervé. "Propriétés électriques et électrochimiques de manganites de lanthane dopées comme matériau de cathode pour pile à combustible à oxyde électrolyte solide". Grenoble INPG, 1994. http://www.theses.fr/1994INPG0053.
Testo completoAbstract (sommario):
Ce travail consiste en l'etude de materiaux de cathode pour les piles a combustible haute temperature. Ces materiaux ont pour formule generale la1-xsrxmno3 et (la1-yyy)0,5sr0,5mno3. Dans un premier chapitre nous faisons le point sur l'etat des recherches sur les piles a combustible a oxyde electrolyte solide et leurs constituants. Le deuxieme chapitre presente la synthese des echantillons ainsi que les differents dispositifs de mesures. Le chapitre trois est consacre a la caracterisation physique et electrique des echantillons. Nous avons montre en particulier que le dopage a l'yttrium diminuait le coefficient de dilatation thermique des manganites de lanthane. Pour les echantillons exempts d'yttrium une conductivite maximale est obtenue pour x=0,55. Une etude sur la reaction de reduction de l'oxygene a l'interface la1-xsrxmno3/y2o3-zro2 est menee dans le chapitre quatre. Nous confirmons l'apparition d'un effet electrocatalytique specifique a ce materiau d'electrode. Nous apportons une contribution complementaire a la comprehension du processus d'electrode: l'echantillon qui presente la plus grande activite electrocatalytique est celui qui a la plus forte conductivite electrique. Aux faibles polarisations cathodiques, superieures a -150 mv/air, nous prouvons que l'etape limitante a lieu le long du contact triple. Aux plus fortes polarisations cathodiques nous emettons l'hypothese d'une extension progressive de la reaction sur une zone annulaire autour du perimetre de contact entre le materiau de cathode et l'electrolyte. Enfin, la surface du materiau d'electrode exposee au gaz n'est pas limitante
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Blanck, Dimitri. "Modélisation de la structure et de la réactivité de la pérovskite LaFeO3 dopée". Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10166/document.
Testo completoAbstract (sommario):
La dépollution des gaz d’échappement des véhicules essence est opérée par catalyse trois voies (CTV). Ce terme désigne la combinaison de trois réactions : l’oxydation du CO en CO2, la combustion des hydrocarbures imbrûlés et la réduction des NOx. Les catalyseurs 3-voies actuels sont constitués de nanoparticules de métaux nobles (Pt, Rh, Pd…) dispersés sur un support oxyde. En raison de leur prix élevés de nombreuse recherche vise à limiter leur utilisation. Utilisées depuis le milieu des années 70 en catalyse en tant que support, les pérovskites sont une alternative possible. Dans le cas de la catalyse trois voies, les capacités oxydo-réductrices intrinsèques du fer font de la pérovskite LaFeO3 (LFO) un candidat intéressant pour la réduction des NOx et l’oxydation du CO. A ce jour, les mécanismes réactionnels de même que les sites actifs de ce catalyseur sont inconnus. Il est donc important de les mettre en évidence pour permettre une amélioration rationnelle des activités et sélectivités des catalyseurs 3 voies de nouvelle génération. Dans cette étude nous avons cherché à déterminer le mécanisme réactionnel sur la pérovskite. Dans un premier nous avons cherché à étudier l’état de surface de la pérovskite en présence d’eau et déterminer les surfaces présentes. Puis nous avons calculé la thermochimie d’un ensemble de réaction élémentaire sur les surfaces pour enfin proposé un mécanisme réactionnel possible de réduction de NO et d’oxydation de CO. Après détermination des états de transition nous avons cherché à optimiser la formulation de la pérovskite en dopant les surfaces en métaux de transitionPollution control of exhaust gases from gasoline vehicles is operated by three-way catalysis (TWC). This term refers to the combination of three reactions: the oxidation of CO to CO2, the combustion of unburned hydrocarbons and NOx reduction. Actually three-way catalysts are made of noble metal nanoparticles (Pt, Rh, Pd ...) deposed on an oxide support. Due to their high and fluctuating price numerous study are trying to limit their use. One possibility are perovskites which are used since the mid-70s in catalysis as support. These materials have also been a recent revival of interest as a carrier or as the active phase to the extent that their structural properties reduce the amounts of noble metals by limiting the aggregation of the metal nanoparticles. In the case of three-way catalysis, the redox intrinsic iron capabilities make the perovskite LaFeO3 (LFO) an interesting candidate for the reduction of NOx and oxidation of CO. To date, the reaction mechanisms, as well as the active sites of the catalyst are unknown. It is important to highlight them for rational improvement activities and selectivity of the catalysts 3 new generation pathways. In this study we sought to determine the reaction mechanism on perovskite. At first we tried to study the surface condition of the perovskite in the presence of water and determine these surfaces. Then we calculated the thermochemistry of a set of elementary reaction on surfaces to finally proposed possible reaction mechanism of NO reduction and CO oxidation. After determining transition states we sought to optimize the formulation of the perovskite by doping transition metal surfaces
Capitoli di libri sul tema "Oxyde de lanthane (La2O3)"
1
Zhao, Yi. "Hygroscopic Tolerance and Permittivity Enhancement of Lanthanum Oxide (La2O3) for High-k Gate Insulators". In High-k Gate Dielectrics for CMOS Technology, 185–223. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2012. http://dx.doi.org/10.1002/9783527646340.ch6.
Testo completoAtti di convegni sul tema "Oxyde de lanthane (La2O3)"
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Gao, W., C. Zhang, F. Lapostolle, H. Liao, C. Coddet e V. Ji. "Synthesis of Lanthanum Silicates with Apatite-type Structure by Atmospheric Plasma Spraying". In ITSC2007, a cura di B. R. Marple, M. M. Hyland, Y. C. Lau, C. J. Li, R. S. Lima e G. Montavon. ASM International, 2007. http://dx.doi.org/10.31399/asm.cp.itsc2007p0756.
Testo completoAbstract (sommario):
Abstract The emergence of lanthanum silicate as an electrolyte is required to accelerate the development of synthesis techniques for intermediate temperature solid oxide fuel cells (ITSOFCs). Apatite-type oxide powders of La10(SiO4)6O3 have been elaborated through atmospheric plasma spraying (APS) using micro-scale mixtures of La2O3 and SiO2 powders. Granulometer and scanning electron microscopy analyses have indicated the result of high temperature reaction and rapid solidification in the evolution of multi-scale microstructure.
2
Yushkevich, Sergey, Oksana Korniienko, Olesia Pavlenko, Olena Olifan, Anatoliy Samelyuk e Irina Subbota. "Interaction Cerium Oxide with Lanthanum and Neodium at 1500°C". In International Young Scientists Conference on Materials Science and Surface Engineering. Karpenko Physico-Mechanical Institute of the NAS of Ukraine, 2023. http://dx.doi.org/10.15407/msse2023.028.
Testo completoAbstract (sommario):
The phase equilibria in the ternary system CeO2–La2O3–Nd2O were systematically studied at a temperature of 1500°C, covering the entire concentration range. No new phases were identified within the specified system. An isothermal section of the phase diagram for the CeO2–LaO2–Nd2O3 ternary system was constructed. The investigation revealed the formation of solid solutions, including cubic solid solutions with a fluorite-type structure F-CeO2, as well as solid solutions based on the hexagonal (A) and cubic (C) modifications of Ln2O3. The phase fields and crystal lattice periods of the formed phases were determined for all investigated systems.
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Tekeli, S., B. Aktas e S. Salman. "Synthesis and mechanical properties of lanthanum oxide (La2O3)doped 8 mol % yttria-stabilized cubic zirconia (8YSZ)". In 2012 IEEE International Conference on Oxide Materials for Electronic Engineering (OMEE). IEEE, 2012. http://dx.doi.org/10.1109/omee.2012.6464782.
Testo completo
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Friedrich, C. J., R. Gadow e T. Schirmer. "Lanthane Aluminate—A New Material for Atmospheric Plasma Spraying of Advanced Thermal Barrier Coatings". In ITSC 2000, a cura di Christopher C. Berndt. ASM International, 2000. http://dx.doi.org/10.31399/asm.cp.itsc2000p1219.
Testo completoAbstract (sommario):
Abstract One of the main application fields of the thermal spraying process are thermal barrier coatings (TBC). Today partially stabilised zirconia (YSZ or MSZ) is mainly used as TBC material. At temperatures above 1000°C, zirconia layers ages distinctively including shrinkage and microcrack formation. Therefore there is a considerable interest in TBCs for higher temperature application. In this paper lanthanum aluminate, a newly developed TBC material with long term stability up to 1400 °C, is presented. It ages significantly slower at these high temperatures than commercial zirconia based TBCs. Its composition favors the formation of platelets, which prevent a densification of the coating by postsintering. It consists of La2O3, AI2O3 and MgO. Its crystal structure corresponds to lanthanum aluminate powders were produced using two different fabrication routes, one based on salts, the other one based on oxides. To optimise the granulate various raw materials and additives were tested. The slurry was spray dried in a laboratory spray drier and calcined at 1650°C. Using these two powders, coatings were produced by atmospheric plasma spraying (APS). The residual stresses of the coatings were measured by the hole drilling method and the deposition process was optimised with respect to the residual stresses of the TBC. The coatings were extensively analysed regarding phase composition, thermal expansion, long term stability as well as microstructural properties.
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Karthikeyan, S., K. Dhanakodi, S. Surendhiran, P. Thirunavukkarasu, L. Arunraja e P. Manojkumar. "Structural, morphological and optical properties of pure and Yttrium (Y) doped lanthanum oxide (La2O3) nanoparticles by sonochemical method". In INTERNATIONAL CONFERENCE ON ADVANCES IN MATERIALS, COMPUTING AND COMMUNICATION TECHNOLOGIES: (ICAMCCT 2021). AIP Publishing, 2022. http://dx.doi.org/10.1063/5.0070786.
Testo completo