To see the other types of publications on this topic, follow the link: Cobalt oxides.
Dissertations / Theses on the topic 'Cobalt oxides'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Cobalt oxides.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Curelea, Sergiu. "Non stoichiometric effects in cobalt rich complex oxides." Caen, 2012. http://www.theses.fr/2012CAEN2031.
Full textAbstract:
This memory is devoted to the research and characterization of new complex cobalt-rich oxides, by transmission electron microscopy (TEM) techniques. A part of the work presents the study of a “114”-type compound, non-stoichiometric at the level of the oxygen content, YBaCo4O7+δ, for the case when δ has a value of approximately 1. 5. When an extra oxygen content is applied to the original, stoichiometric material, it has been found during the TEM studies that these extra oxygen atoms cause the formation of a complex superstructure that has been characterized in terms of the lattice parameters. This is accompanied by a reduction of the original trigonal symmetry to an orthorhombic one. Layered, cobalt-rich materials in the Ba–Co–O system, formed by the intergrowth of the hexagonal perovskite, more exactly the Ba2Co9O14 and Ba3Co10O17 compounds, are presented in the second part of the memory. These materials are part of a larger structural family, which corresponds to the [BaCoO3]n[BaCo8O11] chemical formula, where n denotes the thickness (number) of hexagonal perovskite blocs [BaCoO3] in their structure. The second part of the formula represents the chemical composition of another block, common to all these materials. Which is a CdI2-type one, responsible for the magnetic properties at low temperature, that these compounds exhibit. Concerning the n = 2 term, it is impossible to synthesize the pure phase, systematically obtaining secondary phases (like BaCoO3 or Co3O4). Chemical doping, by replacing a part of the cobalt species with iron, and using the sol-gel technique, leads to obtaining a nearly pure phase Ba3(Fe,Co)10O17, which has been analyzed by X-ray diffraction, neutron diffraction and transmission electron microscopy.
2
Yar-Mukhamedova, G. Sh, M. V. Ved, A. V. Karakurkchi, and N. D. Sakhnenko. "Mixed alumina and cobalt containing plasma electrolytic oxide coatings." Thesis, IOP Publishing Ltd, 2017. http://repository.kpi.kharkov.ua/handle/KhPI-Press/30798.
Full textAbstract:
Principles of plasma electrolytic oxidation of the AL25 aluminum alloy in diphosphate alkali solutions containing cobalt(2+) cations are discussed. It has been established that a variation in the concentration of the electrolyte components provides the formation of mixed-oxide coatings consisting of the basic matrix materials and the cobalt oxides of different content. An increase in the cobalt oxide content in the coating is achieved by the variation in electrolysis current density as well as the treatment time due to both the electrochemical and thermo-chemical reactions at substrate surface and in spark region. Current density intervals that provide micro-globular surface formation and uniform cobalt distribution in the coating are determined. The composition and morphology of the surface causes high catalytic properties of synthesized materials, which confirmed the results of testing in model reaction CO and benzene oxidation as well as fuel combustion for various modes of engine operation.
3
Kroll, Thomas. "On the electronic structure of layered sodium cobalt oxides." Doctoral thesis, [S.l. : s.n.], 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1182443937257-74133.
Full text
4
El-Shinawi, Hany Zakaria Ibrahim. "Synthesis and characterization of cobalt-containing perovskite-type oxides." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/625/.
Full textAbstract:
A number of cobalt-containing perovskite-type oxides were synthesized and characterized in this study. All materials were half-doped with cobalt in their B-sites, i.e. contain the Co0.5M0.5 B-site state where M = Fe, Mn, Cr, Ni; the materials adopted single layered, double-layered and simple perovskite-type structures. The materials La2 xSrxCo0.5M0.5O4 (M = Fe, Cr) have shown enhanced stability under reducing conditions (10% H2/N2, up to 1000 ºC) with the formation of oxygen deficient compounds, while no evidence for oxygen hyperstoichiometry was observed under oxidizing conditions. Materials such La1.2Sr0.8Co0.5Mn0.5O4.1 and La1.7Sr0.3Co0.5Ni0.5O4.08, however, exhibit oxygen hyperstoichiometry under oxidizing conditions and also withstand reducing conditions via formation of oxygen deficiency. Oxygen vacancies were disordered and confined to the equatorial planes of the single layered structure in all materials, while oxygen hyperstoichiometry was accommodated in the interstitial (0, 0 .5, 0.25) sites of the tetragonal structure. In La1+xSr2 xCoMnO7-δ, oxygen vacancies were confined to the common apex of the double layered structure. The new brownmillerite phase LaSrCoFeO5 was synthesized and fluorination produced the new oxyfluoride LaSrCoFeO5F. Magnetic interactions between Co2+(3+) ions and ions such as Fe3+, Mn3+, Cr3+, Ni2+ in different perovskite-type structures were also studied and a range of magnetically ordered materials, at low and room temperatures, were investigated.
5
Kroll, Thomas. "On the electronic structure of layered sodium cobalt oxides." Doctoral thesis, Technische Universität Dresden, 2006. https://tud.qucosa.de/id/qucosa%3A24889.
Full textAbstract:
The discovery of an unexpectedly large thermopower accompanied by low resistivity and low thermal conductivity in NaxCoO2 raised significant research interest in these materials and let to a number of experimental and theoretical investigations. This interest has strongly been reinforced by the discovery of superconductivity in the hydrated compound Na0.35CoO2 •1.3H2O in 2003, and thus, NaxCoO2 experiences an again increasing attention. The similarity of the Na cobaltates to the high temperature superconductors (HTSC) - both are transition metal oxides and adopt a layered crystal structure with quasi-two-dimensional (Cu,Co)O2 layers - is an important aspect of the research activities. In contrast to the HTSC cuprates however, the CoO2 layers consist of edge sharing CoO6 octahedra which are distorted in such a way that the resulting local symmetry is trigonal. The trigonal coordination of the Co sites results in geometric frustration which favours unconventional electronic ground states. The geometrically frustrated CoO2 sublattice also exists in the nonhydrated parent compound NaxCoO2, which has been investigated in this work. The intercalation of water into the parent compound is expected to have little effect on the Fermi surface beside the increase in two dimensionality due to the effect of expansion. Upon lowering the symmetry from cubic to trigonal, the t2g states split into states with eg_and a1g symmetry. Measurements of polarisation and temperature dependent soft X-ray absorption have been performed on a wide doping range of NaxCoO2 single crystals. Beside the Co L_2,3-edges, the O K-edge and the Na K-edge have been measured. These measurements show strong polarisation dependencies especially for the excitations into the lower lying a1g energy level. In addition to that, also an unexpected polarisation dependence for higher energies has been observed, which should be absent in trigonal symmetry. These results point towards a deviation of the local trigonal symmetry of the CoO6 octahedra, which is temperature independent in a temperature range between 25 K and 372 K. This deviation was found to be different for Co3+ and Co4+ sites, which leads to a polaronic electron transport. Furthermore, a strong hybridisation between the Co and O ions has been found. In order to shed further light on the electronic structure of NaxCoO2, the electronic spectrum of a CoO6 cluster has been calculated including all interactions between 3d orbitals as well as hopping processes between Co and O and O and O ions. The ground state for two electronic occupations in the cluster (i.e. Co3+ and Co4+) that correspond nominally to all O in the O−2 oxidation state, and Co+3 or Co+4 has been obtained. Then, all excited states obtained by promotion of a Co 2p electron to a 3d electron, and the corresponding matrix elements are calculated. A fit of the observed experimental spectra is good and points out a large Co-O covalence and cubic crystal field effects, that result in low spin Co 3d configurations. The results indicate that the effective hopping between different Co atoms plays a major role in determining the symmetry of the ground state in the lattice. Remaining quantitative discrepancies with the XAS experiments are expected to come from composition effects of itineracy in the ground and excited states. Beside these points, results of photoemission spectroscopy, magnetisation measurements as well as resonant and non-resonant X-ray diffraction using high energy X-rays are shown and discussed.Die Entdeckung unerwartet großer Thermokraft bei gleichzeitigem niedrigem Widerstand und niedriger thermischen Leitfähigkeit in NaxCoO2 führte zu einem großen wissenschaftlichem Interesse an diesen Materialien und zu einer großen Anzahl an experimentellen und theoretischen Arbeiten. Dieses Interesse steigerte sich noch einmal nach der Entdeckung von Supraleitung in der hydrierten Verbindung Na0.35CoO2 •1.3H2O im Jahre 2003. Die Ähnlichkeit der Na Kobaltate zu den Hochtemperatur-Supraleitern (HTSL) – beides sind Übergangsmetalloxide mit einer geschichteten Kristallstruktur in der quasi zwei dimensionale (Cu,Co)O2 Ebenen enthalten sind – ist ein wichtiger Aspekt moderner wissenschaftlicher Arbeiten. Im Gegensatz zu den HTSL Kupraten bestehen die CoO2 Ebenen aus CoO6 Oktaedern die über ihre Kanten verbunden sind und in der Art verzerrt sind, dass die resultierende Symmetrie trigonal ist. Die trigonale Anordnung der Co Plätze führt zu einer geometrischen Frustration und unkonventionellen elektronischen Grundzuständen. Diese geometrisch frustrierten CoO2 Untergitter existieren ebenfalls in den nicht hydrierten Mutterverbindungen NaxCoO2, welche in dieser Arbeit untersucht wurden. Interkalierung von Wasser in die Mutterverbindung hat nur einen kleinen Einfluss auf die Fermi Oberfläche und führt zu einem Anstieg des zwei dimensionalen Charakters durch den Effekt der Ausdehnung. Durch Verminderung der Symmetrie von kubisch zu trigonal splitten die vormals entarteten t2g Zustände auf in Zustände mit eg und a1g Symmetrie. Zur Bestimmung der elektronischen Struktur von NaxCoO2 wurden polarisations- und temperaturabhängige Messungen der Röntgenabsorption im weichen Röntgenbereich für einen großen Dotierungsbereich durchgeführt. Neben den Co L_2,3-Kanten wurden auch die O K-Kante und die Na K-Kante gemessen. Sie zeigen eine starke Polarisationsabhängigkeit speziell für Anregungen in die niederenergetischen a1g Level. Zusätzlich wurde eine unerwartete Polarisationsabhängigkeit bei höheren Energien gefunden, die für trigonalen Symmetrie so nicht auftauchen dürfte. Diese Ergebnisse weisen auf eine Abweichung von der lokalen trigonalen Symmetrie der CoO6 Oktaeder hin, welche Temperatur unabhängig ist in einem Temperaturbereich zwischen 25 und 372 Kelvin. Diese Abweichung ist unterschiedlich für Co3+ und Co4+ Ionen was wiederum auf einen polaronischen Transport hinweist. Zusätzlich wird deutlich, dass eine starke Co-O Hybridisierung existieren muss. Um weiteres Informationen über die elektronische Struktur von NaxCoO2 zu erhalten, wurde das elektronische Spektrum eines CoO6 Oktaeders berechnet in dem alle Wechselwirkungen zwischen 3d Orbitalen sowie Hüpfprozesse zwischen Co und O sowie O und O Ionen enthalten sind. Der Grundzustand für zwei elektronische Besetzungen in einem Cluster (d.h. Co3+ und Co4+) wurde bestimmt für O Ionen mit einer nominellen O-2 Oxidation sowie Co3+ und Co4+ Ionen. Im angeregten Zustand werden die entsprechenden Anregungen eines Co 2p Elektrons in einen unbesetzten 3d Zustand berücksichtigt und die entsprechenden Matrixelemente berechnet. Ein Fit an den experimentellen Daten ist gut und weist auf eine starke Co-O Kovalenz und auf einen starken Einfluss des kubischen Kristallfeldes hin, der zu einer Low-Spin Co 3d Konfiguration führt. Die Ergebnisse zeigen, dass ein effektives Hüpfen zwischen benachbarter Co Ionen eine große Rolle für die Symmetrie des Grundzustandes im Gitter spielt. Quantitative Unterschiede zwischen den experimentellen und theoretischen Daten kommen anscheinend von itineranten Effekten im Grund- und angeregten Zustand. Zusätzlich zu den oben kurz beschriebenen Ergebnissen werden in dieser Arbeit weitere Ergebnisse der Photoemissionsspektroskopie, der Magnetisierung sowie aus resonanter und nicht resonanter Röntgenbeugung mit harter Röntgenstrahlung gezeigt und diskutiert.
6
Hao, Yalin. "Continuous Hydrothermal Production of Iron Oxide (Fe[subscript 2]0[subscript 3]) and Cobalt Oxide (Co[subscript 3]O[subscript 4])." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/11217.
Full text
7
Sugiyama, J., H. Nozaki, Y. Ikedo, K. Mukai, D. Andreica, A. Amato, J. H. Brewer, et al. "Evidence of Two Dimensionality in Quasi-One-Dimensional Cobalt Oxides." American Physical Society, 2006. http://hdl.handle.net/2237/8880.
Full text
8
Rafique, Hafiz Muhammad. "Resonant and high resolution photoemission of rare-earth cobalt oxides." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/resonant-and-high-resolution-photoemission-of-rareearth-cobalt-oxides(33377a1a-670c-413d-a38f-73c52115b5e5).html.
Full textAbstract:
LnBaCo2O5+δ (Ln-112) where Ln = lanthanide element; 0 ≤ δ ≤1 and LnBaCo4O7+δ (Ln-114) are highly correlated cobalt oxides. Synchrotron photoemission spectroscopy of LnBaCo2O5+δ (Ln = Gd, Dy, Dy1-xTbx) and LnBaCo4O7 (Ln = Yb) has been undertaken at the UK Synchrotron Radiation Source (Daresbury Laboratory).During the photoemission experiments, the samples were observed to be contaminated due to residual gases inside the main vacuum chamber. The surface degradation of the samples is studied using the difference spectra generated from the valence band spectra of freshly scraped and contaminated samples and the nature of contaminated species on these samples is identified in the light of the reviewed literature. High-resolution photoemission is carried out to study the metal-insulator (MI) transition in double perovskites LnBaCo2O5+δ (Ln = Gd, Dy, Dy1-xTbx - Ln-112; 0 ≤ δ ≤ 1) as a function of temperature. The high-resolution photoemission results of single crystal samples of GdBaCo2O5.5, DyBaCo2O5.5 and Dy1-xTbxBaCo2O5+δ show that the temperature-based MI transitions in these compounds occur in the 300-400 K temperature range. A post-growth oxygen annealing treatment for as-grown single crystals of Ln-112 is necessary, achieving oxygen contents close to 5.50, to observe a marked nonmetal-to-metal transition. Resonant photoemission is used to identify the atomic parentage of the valence band states. A comparison of the electronic structure of LnBaCo2O5+δ (Ln = Gd, Dy, Dy1-xTbx - Ln-112; 0 ≤ δ ≤ 1) and LnBaCo4O7 (Ln = Yb - Ln-114) single-crystal surfaces is made using synchrotron photoemission spectroscopy. In both cases, the states close to the Fermi energy are found to be of mixed Co 3d/O 2p character, and the comparison allows identification of states due to low spin Co³⁺ in octahedral environments. The contributions from Ln elements to the valence band are found at higher binding energies.
9
Iablokov, 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 textAbstract:
Durant ce travail de thèse, d’importants paramètres concernant la synthèse de matériaux catalytiques nanostructurés à base de manganèse et d’oxydes de cobalt ont été établis. La corrélation entre les propriétés structurales du catalyseur et l’activité catalytique, ainsi que le mécanisme d’oxydation du CO ont été analysé au moyen d’une grande variété de méthodes expérimentales physico-chimiques.De 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
10
FERREIRA, JUNIOR JOSE M. "Síntese e caracterização elétrica de materiais com comportamento termistor à base de óxidos de manganês, de níquel de cobalto." reponame:Repositório Institucional do IPEN, 2007. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11600.
Full textAbstract:
Made available in DSpace on 2014-10-09T12:53:43Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T13:58:43Z (GMT). No. of bitstreams: 0
Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
11
Taylor, Anthony Park 1963. "Terbium iron cobalt diffusion barrier studies." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276931.
Full textAbstract:
Thin films (5nm ± 2nm thick) of ZrO2, Al2O3, TiO2, Sm, Gd, Zr, Ni, and Pt were deposited onto TbFeCo films (100nm ± 20nm thick) on silicon and graphite substrates and analyzed with XPS as prospective candidates for TbFeCo diffusion barriers. Metals were chosen primarily according to electronegativity. Samples were typically heated to 272°C in UHV for 20 hours to enhance diffusion. Experiments with the metals were performed in a more consistent manner than with the oxides. The Sm, Gd, and Zr were reactively oxidized during the deposition. The Sm/Sm-oxide and Gd/Gd-oxide appeared to be favorable candidates for TbFeCo diffusion barriers. TbFeCo was not detected near the surface before or after heating the samples to 272°C for 20 hours and depth profiles indicated oxygen contamination decreased steadily as the barrier/TbFeCo interface was approached. For the other materials examined, either the oxides were reduced (at least partially) during heating to 272°C (381°C for Al₂O₃) or diffusion of TbFeCo was detected after heating, indicating that they would not be favorable candidates for TbFeCo diffusion barriers.
12
SILVA, GRAZIELA C. T. da. "Efeito da adicao de oxido de cobalto na sinterizacao e na condutividade eletrica da zirconia estabilizada com itria." reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11718.
Full textAbstract:
Made available in DSpace on 2014-10-09T12:55:04Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:05:55Z (GMT). No. of bitstreams: 0
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
13
VALLENILLA, CLEMENTE DIOGENES. "SYNTHESIS, CHARACTERIZATION AND REACTIONS OF TERTIARY PHOSPHINE COMPLEXES OF COBALT DERIVATIVES OF NITROGEN OXIDES." Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/187919.
Full textAbstract:
Co(NO)(NO₂)₂L₂ complexes (L = PPh₃, PMePh₂, PMe₂Ph, PMe₃, PEt₃, PEt₂Ph, PEtPh₂, PPrPh₂, PBu₃ and 1/2DPPPr) were prepared from the reactions of Co(NO)X₂L₂ (X = Cl, Br) with sodium nitrite in methanol freshly distilled from magnesium methoxide. The complexes were characterized by elemental analysis, 15-N labeling, infrared and NMR spectroscopy. The crystal structure of Co(NO)(NO₂)₂(PMePh₂)₂ was determined by X-ray diffraction. The cobalt atom has tetragonal pyramidal geometry. The nitrosyl group in the axial position is strongly bent. The NO₂ ligands have two different ligating geometries: one is bound to cobalt through the nitrogen atom and the other is bidentate forming an asymmetric four membered ring. The phosphine ligands are equivalent and trans to each other. Multinuclear NMR spectroscopy (¹H, ³¹P, ¹⁵N and ¹⁴N) was used to determine the solution structure of Co(NO)(NO₂ )₂L₂ complexes, to study mono and bisnitrosyls of cobalt, to establish some correlations between NMR parameters and structural characteristics of these complexes and to follow their reactions in solution. Reactions of Co(NO)(NO₂)₂L₂ with CO, NO and RCOX were observed to produce Co(NO)₂XL complexes. Since the structure may be indicative of electronic requirements at the metal center as well as the reactivity of the compounds, The crystal structures of Co(NO)₂Cl(PPh₃) and Co(NO)₂(ONO)(PPh₃) were also determined. In these complexes the cobalt atoms have pseudotetrahedral geometry. The CoNO angles are in the range considered to be linear. They are geniculated in an "atracto" conformation. Co(NO)(NO₂)₂L₂ and Co(NO)₂(ONO)L complexes react with oxygen in the solid state or in solution to form Co(NO₃)₂(OL)₂ complexes. When the reactions with O₂ were carried out in the presence of an excess of olefins, the formation of nitrates is inhibited Co(NO₂)₂(OL)₂ and olefin oxides are formed instead. The crystal structures of Co(NO₃)₂(OPMePh₂)₂ and Co(NO₂)₂(OPMePh₂)₂ were determined by X-ray diffraction. In these complexes, the NO₃ and NO₂ groups are bidentate. They are arranged in a cis configuration around the cobalt atom.
14
Podchezertsev, Stanislav. "Magnetoelectric coupling in cobalt-based tellurium (VI) oxides with complex spin structures." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMC228.
Full textAbstract:
La thèse actuelle est consacrée à une étude complexe de diffusion de neutrons sur des séries de spinelles de tellure à base de cobalt (VI) dopées au zinc. Il a été constaté que le composé parent peut être obtenu sous deux formes structurelles: centrosymétrique désordonnée (groupe d'espace # 227) et non-centrosymétrique ordonnée (groupe d'espace # 212). Alors que le polymorphe désordonné soit un ferrimagnet typique de type Néel avec une transition magnétique à 40 K, le polymorphe ordonné possède deux transitions de phase magnétiques incommensurables à 45 K et 27 K. Grâce à l'approche de symétrie super-spatiale, il a été découvert que la structure de spin d'un polymorphe ordonné est une spirale ferrimagnétique. La frustration magnétique et l'interaction Dzyaloshinskii-Morya stabilisent cet ordre magnétique. Le système montre la stabilité de la structure magnétique contre la dilution magnétique, qui occupe de préférence l'environnement tétraédrique: ce n'est que lorsque la moitié des sites A est remplacée par du zinc que l'ordre magnétique à longue distance est supprimé. Ce qui est remarquable, ce sont les deux polymorphes qui démontrent une diffusion diffuse magnétique bien au-dessus des températures de transition à longue distance. L'analyse de polarisation Neutron XYZ a révélé: quand le polymorphe est ordonné, l'ordre à courte portée a la même nature en spirale ferrimagnétique que l'état ordonné. L'ordre à courte portée du polymorphe ordonné fortement dilué est similaire au composé parent. La spectroscopie diélectrique du composé désordonné et ordonné a révélé un comportement magnétoélectrique en chaque casThe current thesis is dedicated to a complex neutron scattering study of magnetic behaviour cobalt-based tellurium (VI) spinel series doped with zinc. It was found that the parent compound may be obtained in two structural forms: disordered centrosymmetric (space group #227) and ordered non-centrosymmetric (space group #212). While the disordered polymorph is a typical Néel-type ferrimagnet with a magnetic transition at 40 K, the ordered polymorph possesses two incommensurate magnetic phase transitions at 45 K and 27 K. With a help of the superspace symmetry approach the spin structure of the ordered polymorph was found to be ferrimagnetic spiral. Both magnetic frustration and Dzyaloshinskii-Morya interaction stabilize such a magnetic ordering. The system shows stability of the magnetic structure against magnetic dilution, which occupies tetrahedral environment preferably: only when the half of A-sites is substituted with zinc the long range magnetic ordering is suppressed. Remarkably, both polymorphs demonstrate magnetic diffuse scattering far above long-range transition temperatures. Neutron XYZ polarization analysis revealed that in the case of the ordered polymorph the short-range ordering has the same ferrimagnetic spiral nature as the ordered state. Short-range ordering of the highly diluted ordered polymorph is similar to the parent compound. Dielectric spectroscopy of the disordered and ordered compound revealed magnetoelectric behaviour in each case
15
Gao, Hongyan. "Nano/Submicro-Structured Iron Cobalt Oxides Based Materials for Energy Storage Application." TopSCHOLAR®, 2017. https://digitalcommons.wku.edu/theses/2057.
Full textAbstract:
Supercapacitors, as promising energy storage devices, have been of interest for their long lifespan compared to secondary batteries, high capacitance and excellent reliability compared to conventional dielectric capacitors. Transition metal oxides can be applied as the electrode materials for pseudocapacitors and offer a much higher specific capacitance. Co3O4 is one of the most investigated transition metal oxides for supercapacitor. Besides simple monometallic oxides, bimetallic transition oxides have recently drawn growing attention in electrochemical energy storage. They present many unique properties such as achievable oxidation states, high electrical conductivities because of the coexistence of two different cations in a single crystal structure.
This study focuses on the bimetallic iron cobalt oxide based materials for the application of energy storage. We selected iron as the substituent in spinel Co3O4, by virtue of its abundant and harmless character. Four types of iron cobalt oxides based electrode materials with different morphologies and components have been synthesized for the first time. The hydrothermal method was the main strategy for the synthesis of iron cobalt based materials, which achieved the control of morphology and ratio of components. Multiple characterization methods, including SEM, TEM, XRD, XPS, TGA, BET, have been applied to study the morphologies and nano/submicron structures. The electrochemical properties of as-fabricated samples were performed by electrochemical workstation. In addition, in order to investigate the practical application of electrode materials, asymmetric supercapacitors have been assembled by using as-prepared samples as the positive electrodes and activated carbon as the negative electrodes.
16
Wei, Guang. "Lithium cobalt oxide thin films : preparation and characterization for electrochromic applications /." Thesis, Connect to Dissertations & Theses @ Tufts University, 1991.
Find full textAbstract:
Thesis (Ph.D.)--Tufts University, 1991.Submitted to the Dept. of Electrical Engineering (Electro-Optics Option). Includes bibliographical references. Access restricted to members of the Tufts University community. Also available via the World Wide Web;
17
Tsui, Hei Man. "Synthesis and Characterization of Magnetic Cabides and Oxides Nanomaterials." VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5366.
Full textAbstract:
The design and development of nanoparticles is of great interest in the current energy and electronic industry. However, based on the current materials available the production cost can be high with insignificant magnetic and mechanical properties. Specifically, rare-earth magnetic materials composed of neodymium and samarium are known for their high magnetic performance, however, due to the cost of development there is a need to develop a versatile and cost effective material. Alternatively, cobalt carbide nanomaterials have shown to be a promising alternative for rare-earth free magnets as they exhibit comparable properties as hexaferrite magnetic materials. The primary goal of this dissertation focuses on the development of nanoparticles for permeant magnetic, and magnetic refrigeration applications. The first part of this work focuses on the synthesis of cobalt carbide (CoxC, x=2,3) nanoparticles using a novel polyol synthesis method by introducing a small amount of Ru, Cu, or Au as nucleating agent. It was found that the morphology and magnetic properties of the as-synthesized CoxC nanoparticles change as a result of directional growth of nanoparticles using nucleating agents. Needle-like particle morphology ranges from 20-50 nm in width and as long as 1 µm in length were synthesized using Ru as nucleating agent. These particles exhibit magnetization saturation of 33.5 emu/g with a coercivity of 2870 Oe and a maximum energy product 1.92 MGOe (BHmax) observed. Particle morphology is a critical aspect in the development of magnetic nanoparticles as anisotropic particles have shown increased coercivity and magnetic properties. These CoxC nanomaterials have a higher maximum energy product compared to previous work providing further insight into the development of non-rare earth magnetic material.
The second part of this dissertation work focuses on the sol-gel synthesis of perovskite LaCaMnO3 (LCMO) nanomaterials. In this process, various chain lengths of polyethylene glycol (PEG) was added into a solution consisting of La, Ca, and Mn salts. The solution was left for the gelation process, and high temperature sintering to obtain the final product. By varying the polymer chain of the PEG, the size of the as synthesized LaCaMnO3 nanomaterials were altered. The as-synthesized LCMO nanomaterials have shown a maximum change in magnetic entropy (-ΔSM) was found to be 19.3 Jkg-1K-1 at 278 K for a field change of 0-3 T and 8.7 Jkg-1K-1 for a field change of 0-1 T. This is a significant improvement in comparison to current literature of the material suggesting that this is a promising alternative to Gd materials that is prone to oxidation. With additional development, LCMO or related maganites could lead to application in commercial technologies.
18
Takeuchi, Tsunehiro, Takeshi Kondo, Tsuyoshi Takami, Hirofumi Takahashi, Hiroshi Ikuta, Uichiro Mizutani, Kazuo Soda, et al. "Contribution of electronic structure to the large thermoelectric power in layered cobalt oxides." The American Physical Society, 2004. http://hdl.handle.net/2237/7117.
Full text
19
Büttner, Gesine [Verfasser], and Anke [Akademischer Betreuer] Weidenkaff. "Misfit-layered cobalt oxides for thermoelectric energy conversion / Gesine Büttner ; Betreuer: Anke Weidenkaff." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2017. http://d-nb.info/1159570256/34.
Full text
20
Pérez, Galera Juana María. "Impregnated Cobalt, Nickel, Copper and Palladium Oxides on Magnetite: Nanocatalysts for Organic Synthesis." Doctoral thesis, Universidad de Alicante, 2016. http://hdl.handle.net/10045/57586.
Full textAbstract:
In this manuscript, the application of different nanocatalysts derived from metal oxides impregnated on the surface of the magnetite in different reaction of general interest in Organic Chemistry is described. In the First Chapter, a cobalt derived catalyst was used to study the hydroacylation reaction of azodicarboxylates with aldehydes. In the Second Chapter, a catalyst derived from copper was used to perform different reactions, including homocoupling of terminal alkynes and the subsequent hydration reaction to obtain the corresponding 2,5-disubstituted benzofurans, the reaction of alcohols and amines (or nitroarenes) to obtain the corresponding aromatic imines, the cross-dehydrogenative coupling reaction of N-substituted tetrahydroisoquinolines using deep eutectic solvents and air as final oxidant. Finally, the formation of benzofurans from aldehydes and alkynes through a tandem coupling-allenylation-cyclization process has been performed. In the Third Chapter, a bimetallic catalyst derived from nickel and copper was used to study the multicomponent reaction between benzyl bromides, sodium azide and alkynes to obtain the corresponding triazoles. In the Fourth Chapter, a catalyst derived from palladium was used in the direct arylation of heterocycles using iodonium salts. Also the synthesis of 4-aryl coumarins through the Heck arylation reaction and subsequent cyclization using the same catalyst is described. In the last Chapter, the use of different eutectic mixtures were studied as alternative media to perform in a single vessel the cyclation reaction of N-hydroxy imidoyl chlorides and alkynes, without any type of catalyst under oxidizing conditions.
21
Zhang, Hantao S. M. Massachusetts Institute of Technology. "Computational investigation of the thermal conductivities and phonon properties of strontium cobalt oxides." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/123356.
Full textAbstract:
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: S.M., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2019
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 87-91).
The thermal conductivities of electrochemically tuned strontium cobalt oxides (SCO) are significantly different among the perovskite SrCoO3 (P-SCO), the brownmillerite SrCoO2.5 (BM-SCO) and the hydrogenated HSrCoO2.5 (H-SCO)1. The underlying mechanism causing this large difference is still unclear. And phonon properties in SCO have not been investigated thoroughly or have some contradictive predictions. In this work, we have calculated the thermal conductivities in P-SCO and BM-SCO by applying molecular and lattice dynamics, and successfully reconstructed the large difference of the thermal conductivities, consistent with measurements. Furthermore, several phonon properties including heat capacities, group velocities, lifetimes and mean free paths have been calculated, and the key roles of local atomic environment and crystal symmetry in determining the thermal conductivities have been identified. We have also analyzed the impact of interfaces, isotropic strains and defects on thermal conductivities, predicted the neutron scattering intensity in P-SCO, and tested the accuracy and performance of molecular dynamics based on deep learning. Additionally, even though the calculations about the phonon properties in H-SCO are not complete, it still offers some inspirations about its thermal conductivity. The thorough investigations about the phonon properties and the mechanisms determining the thermal conductivities in SCO may benefit future research about tunable thermal conductivities in complex oxides.
by Hantao Zhang.
S.M.
S.M. Massachusetts Institute of Technology, Department of Nuclear Science and Engineering
22
FLORIO, DANIEL Z. de. "Analise de eletrolitos de ZrO sub(2):Y sub(2) O sub(3) + B sub(2) O sub(3) e de eletrodos de La sub(0,8) Sr sub(0,2) Co sub (0,8) Fe sub (0,2) O sub (3-delta) por espectroscopia de impedancia." reponame:Repositório Institucional do IPEN, 2003. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11130.
Full textAbstract:
Made available in DSpace on 2014-10-09T12:48:42Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T13:59:46Z (GMT). No. of bitstreams: 1 09305.pdf: 5404217 bytes, checksum: 19eda8ad49f8cd247304fef0fb69c1bc (MD5)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
23
Moura, Jadson Santos. "Desenvolvimento de catalisadores de ródio e cobalto para a reforma a vapor do etanol." reponame:Repositório Institucional da UFBA, 2007. http://www.repositorio.ufba.br/ri/handle/ri/13210.
Full textAbstract:
99 f.Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2013-10-14T14:32:46Z No. of bitstreams: 1 Dissertação de Jadson Santos Moura.pdf: 1942065 bytes, checksum: 6d4cf335ab5379599dc0e99dd43efeab (MD5)
Approved for entry into archive by Ana Hilda Fonseca(anahilda@ufba.br) on 2013-10-14T14:34:07Z (GMT) No. of bitstreams: 1 Dissertação de Jadson Santos Moura.pdf: 1942065 bytes, checksum: 6d4cf335ab5379599dc0e99dd43efeab (MD5)
Made available in DSpace on 2013-10-14T14:34:08Z (GMT). No. of bitstreams: 1 Dissertação de Jadson Santos Moura.pdf: 1942065 bytes, checksum: 6d4cf335ab5379599dc0e99dd43efeab (MD5) Previous issue date: 2007
CNPq
O desenvolvimento de tecnologias baseadas no uso de biocombustíveis tem despertado a atenção da comunidade científica, devido à dependência atual dos combustíveis fósseis, que resulta no crescente aumento da poluição atmosférica. Este aumento da poluição está relacionado a problemas de saúde pública e alterações climáticas. Neste contexto, a utilização de células a combustível movidas a hidrogênio é um meio de produzir energia de forma limpa, uma vez que o produto residual do funcionamento da célula é a água. O hidrogênio para ser usado neste equipamento pode obtido a partir da reação de hidrocarbonetos ou álcoois com vapor d’água, no processo de reforma a vapor. Com isso, o presente trabalho está baseado no desenvolvimento de catalisadores destinados à produção de hidrogênio a partir da reforma a vapor do etanol. Enquanto o processo envolvendo hidrocarbonetos contribui para o aumento da poluição atmosférica, já que grandes quantidades de dióxido de carbono são produzidas, a utilização do etanol contribui para a resolução de problemas ambientais, pois ele pode ser produzido a partir da cana-de-açúcar e outros vegetais e o dióxido de carbono produzido é consumido durante o crescimento da biomassa. Neste trabalho, foram sintetizados catalisadores monometálicos e bimetálicos de ródio (0,5%) e cobalto (1%) suportados em óxido de alumínio, óxido de magnésio e em um material misto contendo alumínio e magnésio obtido da decomposição térmica de uma hidrotalcita. As amostras foram caracterizadas por análise química, termogravimetria, análise térmica diferencial, espectroscopia no infravermelho com transformada de Fourier, difração de raios X, medida de área superficial específica, redução à temperatura programada e espectroscopia no infravermelho com transformada de Fourier de monóxido de carbono quimissorvido. Os catalisadores foram testados na reação de reforma a vapor do etanol a 500, 600 e 700 °C. A utilização da hidrotalcita como precursor gerou catalisadores com elevada área superficial específica, mas com baixa resistência à sinterização e à mudança de fase. Observou-se que os catalisadores contendo ródio foram ativos e seletivos a hidrogênio, enquanto os monometálicos de cobalto não apresentaram atividade, o que foi atribuído à baixa percentagem de cobalto nos sólidos e à formação de espécies com elevada temperatura de redução, como a solução sólida CoO-MgO e a fase espinélio CoAl2O4. Os resultados mostraram que com o aumento da temperatura de reação são obtidas conversões mais elevadas do etanol e a formação de subprodutos como o eteno, o acetaldeído e o éter etílico é inibida. Além disso, as propriedades ácido-base dos suportes mostraram influência na seletividade dos catalisadores aos produtos gasosos, durante a reforma a vapor do etanol. Os catalisadores contendo magnésio apresentaram baixa seletividade a eteno, enquanto aqueles baseados em óxido de alumínio apresentaram elevadas seletividades à este alceno
Salvador
24
Calisan, Atalay. "Syngas Production Over Reducible Metal Oxides." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615586/index.pdf.
Full textAbstract:
The scope of this thesis was to study thermodynamics of lead oxide and cobalt oxide as the chemical looping agent for oxygen. Furthermore, the theoretical results were verified experimentally. Ellingham diagrams were constructed for the selected oxides. Then, detailed thermodynamic analysis was conducted for stability analysis at different temperatures and pressures. Equilibrium product compositions for various reactions involving these oxides were calculated via Gibbs free energy minimization analysis. Finally, it was shown that cobalt, lead and their oxide forms can be used for syngas production.
In the experimental part PbOx, CoOx, Pt-doped CoOx and Pt-doped cobalt alumina, and mixed lead cobalt oxides were synthesized. In addition, technical grade cobalt oxide and lead rods were also used. XRD analysis indicated that Co3O4, Pb2O3 and &alpha-PbO were the main crystal structures. Oxygen evolution from mixed oxides was monitored by TPD in a home built system. Re-oxidation of the reduced metals was successfully conducted using CO2 and H2O as oxidizing agents. Oxygen TPD studies indicated that oxygen evolution rates and amounts were higher and started at lower temperatures when two oxides were together. These observations were consistent with the predictions obtained from thermodynamics. In a series packed bed reactor, evolved oxygen from the mixed oxides were used to react with coal packed upstream of the oxides. It was found that coal oxidation can be achieved around 400oC and 600oC by using Pb/Co=3 (wt./wt.) looping media with almost no CO2 formation. It was also found that desired product selectivity (CO) can be increased by controlling reactive agent (O2) concentration in reaction environment.
25
Chebiam, Ramanan Venkata. "Lithium-ion battery cathodes : structural and chemical stabilities of layered cobalt and nickel oxides /." Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3008298.
Full text
26
Padilla, Pantoja Jessica. "Spin‐lattice coupling in strongly correlated cobalt oxides investigated by synchrotron and neutron techniques." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/381262.
Full textAbstract:
El trabajo que se presenta en esta tesis has sido realizado entre Enero del 2011 y Diciembre del 2015 en el Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), con la colaboración del Sincrotrón ALBA (Cerdanyola del Vallès).
Los óxidos de cobalto presentan numerosas propiedades funcionales y fenómenos físicos de interés como magnetorresistencia gigante, doble intercambio, separación de fases, cambios de estado de espín, transiciones metal-aislante (TMI), alto poder termoeléctrico, difusión de oxígeno, conducción mixta, orden de carga, orbital, de estado de espín o superconductividad, entre otras propiedades. Presentan interés desde un punto de vista fundamental y debido a su potencial aplicación en campos como la espintrónica, los dispositivos termoeléctricos, como materiales para SOFC, catálisis, sensores, etc..
Destaca en algunas cobaltitas la singular habilidad de los iones del cobalto para adoptar diferentes estados de espín. Ello proporciona un grado de libertad adicional, que además favorece el acoplamiento espín-red, y tiene efectos importantes sobre la movilidad electrónica, la respuesta termoeléctrica y catalítica, o la estabilidad estructural y magnética.
Esta tesis investiga la influencia de las inestabilidades del estado de espín en cobaltitas con acoplamiento espín-red. Aborda cuatro clases principales de cobaltitas correlacionadas, con diferentes estructuras, preparadas o fabricadas principalmente (pero no sólo) en forma másica: LnCoO3, Ln0.50Sr0.50CoO3, LnBaCoO5.50 and Ba2Co9O14. Distintas transiciones estructurales, electrónicas, magnéticas, magnetostructurales y metal-aislante han sido investigadas mediante experimentos en fuentes de radiación sincrotrón y de neutrones. Entre ellas, los sincrotrones ALBA (Barcelona), ESRF (Grenoble), SLS ((PSI, Switzerland)) y Helmholtz-Zentrum Berlin-BESSY II (HZB, Berlín), el reactor de neutrones ILL (Grenoble) y la fuente de espalación SINQ (PSI, Switzerland). A partir de experimentos de difracción de polvo mediante neutrones (NPD) y radiación sincrotrón (SXRPD), espectroscopías de absorción y emisión de rayos-X (XAS y XES) y dicroísmo magnético circular (XMCD).
El interés por los sistemas con fórmula general LnCoO3 reside en la naturaleza de las transiciones de estado de espín (SS) y los dos posibles escenarios propuestos para el compuesto de referencia LaCoO3: LS→LS+HS→HS o LS→IS→HS. Nosotros hemos combinado el análisis de datos de absorción XAS con difracción de neutrones para comprender la influencia de la configuración de espín sobre la evolución de las estructuras cristalinas, y su variación en el diagrama de fases aumentando la distorsión de las cobaltitas LnCoO3.
En el caso de la inesperada segunda transición magnética que muestra la cobaltita metálica Pr0.50Sr0.50CoO3 , la resolución de las estructuras cristalinas y magnéticas que aquí se presenta, junto a la characterización del momento orbital, han sido cruciales para entender el mecanismo de la transición magnetoestructural que presenta este compuesto. La síntesis de otros compuestos similares nos ha permitido trazar las propiedades magnéticas y electrónicas de las cobaltitas semi-dopadas ricas en estroncio de la familia Ln0.50(Sr, A)0.50CoO3 (A=Ba, Ca).
Se han examinado cuidadosamente las complejas propiedades de algunas perovskitas dobles laminares con fórmula LnBaCoO5.50 que presentan una transición metal-aislante cerca de temperatura ambiente. YBaCoO5.50 muestra sucesivas transiciones estructurales y magnéticas que están relacionadas con cambios en el estado de espín. A partir de técnicas de difracción y espectroscopías de rayos-X hemos examinado el papel de los cambios en el estado de espín de los iones Co3+ (en coordinación octaédrica y piramidal) como mecanismo para la transición metal-aislante.
La cobaltita de fórmula Ba2Co9O14 presenta una cierta complejidad estructural y propiedades catalíticas y termoeléctricas prometedoras. Hemos encontrado y descrito una fuerte correlación entre el orden magnético singular, los cambios estructurales y la transición aislante-aislante de alta temperatura con cambios del estado del espín en posiciones específicas de los átomos de cobalto durante dicha transición.The work presented in this thesis has been carried out between January of 2011 and December of 2015 at the Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), with the collaboration of the ALBA Synchrotron Light Source (Cerdanyola del Vallès). Cobalt oxides present a plethora of remarkable properties and physical phenomena like giant magnetoresistance, double-exchange, phase separation, spin-state changes, metal-insulator transitions (MIT), high thermoelectric power, oxygen diffusivity, mixed-conduction, charge, spin-state and orbital ordering or superconductivity among others. These properties are interesting not only from a fundamental point of view but also due to their potential applicability in different fields (spintronics, thermoelectric devices, materials for SOFCs, catalyst systems, sensors, etc..). A very remarkable characteristic of cobaltites is the almost unic ability of Co ions to adopt different spin states. This makes that Co oxides have, in comparison with other transition metal oxides, an extra degree of freedom, which favors the spin-lattice coupling and plays a prominent role in the electron mobility, the thermoelectric and catalytic responses or the structural and magnetic stability. In this thesis, we have investigated the influence of spin state instabilities on the structural, electrical and magnetic properties of cobalt oxides with spin-lattice coupling. Four main classes of strongly correlated cobaltites having different crystallographic structures were prepared or fabricated (mainly but not solely) in bulk form: LnCoO3, Ln0.50Sr0.50CoO3, LnBaCoO5.50 and Ba2Co9O14. Structural, electronic, magnetic, magnetostructural and metal-insulator transitions were addressed by means of experiments using synchrotron X-rays and neutron sources. Among them, the ALBA (Barcelona), ESRF (Grenoble), SLS (PSI, Switzerland) and Helmholtz-Zentrum Berlin-BESSY II (HZB, Berlín) synchrotrons, the ILL neutron reactor (Grenoble) and the SINQ (PSI, Switzerland) spallation source, performing Neutron Powder Diffraction (NPD), Synchrotron X-Ray Powder Diffraction (SXRPD), X-ray Absorption and Emission Spectroscopies (XAS and XES), and X-ray Magnetic Circular Dichroism (XMCD). The interest for LnCoO3 arises from the nature of the two stages spin-state (SS) transition and the possible scenarios proposed for the LaCoO3 reference compound: LS→LS+HS→HS or LS→IS→HS. We have combined the analysis of XAS and NPD to understand the influence of the espín configuration on the crystalline structure evolution, and its variation in the phase diagram by increasing the distortion of LnCoO3 compounds. In the case of the low temperature unexpected second magnetic transition in the FM metal Pr0.50Sr0.50CoO3, the resolution of the crystal and magnetic structures we here provide together with the orbital moment characterization have been crucial to understand the mechanism of the magnetostructural transition in this compound. The synthesis of compounds with similar composition has allowed us to draw an overview of the magnetic and electronic properties of the half-doped Ln0.50(Sr, A)0.50CoO3 cobaltites family (A=Ba, Ca). The complex properties of some double-layered LnBaCoO5.50 perovskites presenting a metal-insulator transition close to room temperature were carefully examined. YBaCoO5.50 exhibits successive concomitant structural and magnetic transitions coupled to spin-state changes. The influence of the changes in the spin state of Co3+ ions as the mechanism for the metal-insulator transition has been described for Co atoms in octahedral and pyramidal coordination using X-ray spectroscopies and diffraction techniques. The charge-ordered Ba2Co9O14 cobaltite presents structural complexity and promising catalytic and thermoelectric properties. We have described a close correlation between its singular magnetic order, structural changes and the insulator-insulator transition at high temperature, and the change in the spin-state of specific Co sites at this transition.
27
Wahl, Sebastian. "Shed Light on Cobalt Oxides for the Oxygen Evolution Reaction – An Operando Spectroelectrochemical Study." Doctoral thesis, Humboldt-Universität zu Berlin, 2020. http://dx.doi.org/10.18452/21108.
Full textAbstract:
In dieser Dissertation wird der Einfluss unterschiedlicher Sauerstoff-Koordinationsgeometrien um ein zentrales Kobaltatom evaluiert. Genauer werden Oxide, die tetraedrisch und oktaedrisch koordiniertes Kobalt enthalten, synthetisiert und charakterisiert. Zudem wird ihre Aktivität in Hinblick auf die Sauerstoffentwicklungsreaktion (OER) unter alkalischen Bedingungen untersucht. Die elektrochemischen Analysen zeigen dabei, dass Materialien, die Kobalt in tetraedrischer Sauerstoffkoordination enthalten, die besseren Katalysatorvorläufer für die OER sind. Weiterhin kann demonstriert werden, dass das Herauslösen von inaktiven Metallen aus einer Struktur die Aktivität erhöht. Darauf basierend wird das neue Material Zn0.35Co0.65O vorgeschlagen. Es kristallisiert in der Wurtzitstruktur und enthält nur tetraedrisch koordinierte Atome. In alkalischen Lösungen wandelt sich die Wurtzitstruktur über die Zwischenstufe Co(OH)2 zum gamma-Co(O)OH um, und nahezu alles Zink wird aus der Struktur herausgelöst. Dadurch wird ein Material mit einer großen elektrochemisch aktiven Oberfläche gewonnen, das unterkoordinierte CoO(6-x) Oktaeder als aktive Zentren für die OER enthält. Hierdurch wird eine herausragende katalytische Leistung erreicht. Um weitere Einblicke in die OER zu generieren, wird Diffuse Reflexions UV/Vis (DRUV) Spektroskopie verwendet. Es werden neuartige Durchflusszellendesigns vorgeschlagen, die es erlauben, DRUV Spektren während der Katalyse aufzunehmen, d.h. operando. Durch diesen spektroelektrochemischen Ansatz werden Veränderungen der Katalysatoren während der OER beobachtet. So kann die Phasenumwandlung von Zn0.35Co0.65O erfolgreich verfolgt werden. Ebenso kann gezeigt werden, dass CoAl2O4 und Co2SnO4 nur an ihrer Oberfläche katalytische Aktivität aufweisen. Durch den Vergleich mit ex situ Analysen werden eindeutige Struktur-Eigenschaftsbeziehungen vorgeschlagen und tiefere Einsichten in die katalytisch aktiven Strukturmotive erhalten.In this PhD thesis, the influence of different coordination geometries of oxygen atoms around a central cobalt atom is evaluated. Specifically, oxides containing tetrahedral and octahedral coordinated cobalt are synthesized, characterized and their activity towards the OER under alkaline conditions is evaluated. The electrochemical analyses reveal, that materials containing cobalt in tetrahedral oxygen coordination are better precatalysts for the OER. Furthermore, it is demonstrated that leaching of inactive metals from a structure increases the activity as well. Based on the previous mentioned, the new material Zn0.35Co0.65O is proposed. It crystallizes in the wurtzite structure and contains solely tetrahedrally coordinated atoms. In alkaline solutions, it transforms from wurtzite structure via a hydroxide to gamma-Co(O)OH, and nearly all Zn is leached from the structure. By this, a material with a large electrochemically active surface area is generated, that contains under-coordinated CoO(6-x) octahedra as active centers for the OER. Thus, outstanding catalytic performance is achieved. To generate further insights into the OER, diffuse reflectance ultraviolet visible (DRUV) spectroscopy is facilitated. Novel flow-cell designs are proposed, that allow to record DRUV spectra of catalysts under working conditions, i.e. operando. By this spectroelectrochemical approach, changes the catalysts undergo during the OER are observed. The phase transitions of Zn0.35Co0.65O are successfully followed, and it can be further shown, that CoAl2O4 and Co2SnO4 are only active at their surface. By comparison to ex situ analyses, clear structure-activity correlations are proposed, and deeper insights in the catalytically active structural motifs are obtained.
28
Yung, Matthew Maurice. "Oxidation catalysis in environmental applications nitric oxide and carbon monoxide oxidation for the reduction of combustion emissions and purification of hydrogen streams /." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1187128442.
Full text
29
Risch, Marcel [Verfasser]. "Structure-function relations in water-oxidizing cobalt oxides investigated by X-ray absorption spectroscopy / Marcel Risch." Berlin : Freie Universität Berlin, 2012. http://d-nb.info/1029941270/34.
Full text
30
Luo, Wen. "Tuning the redox properties of cobalt particles supported on oxides by an In-between graphene layer." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAF007/document.
Full textAbstract:
L'interaction métal-support (MSI) joue un rôle important dans la catalyse hétérogène. La compréhension et la modification du MSI sont des étapes essentielles pour développer catalyseurs de haute performance. Dans cette thèse, un nouveau concept, qu’il s’agit de recouvrir le support l'oxyde avec un revêtement mono-couche de graphène, a été proposé pour modifier le MSI. L'influence de la couche de graphène sur les interactions de métal (Co et Co-Pt) - oxyde (ZnO et SiO2) et sur les propriétés d'oxydo-réduction des particules métalliques ont été évaluées via des systèmes catalytiques de modèle. Les résultats ont montré que la mono-couche de graphène peut influencer considérablement les états d'oxydation et les morphologies des Co monométallique et Co-Pt bimétallique par rapport aux ceux résultent d’un dépôt direct sur les oxydes nus. En particulier, par calcination sous vide, le graphène protége Co d'être oxydé par ZnO, ce qui conduit à la formation d’un mélange métallique Co-Pt. Co interagit avec les substrats d'oxydes pour former des particules plates qui sont facilement oxydés par O2 en pression faible, tandis que l'insertion d'une couche intermédiaire de graphène entre la couche supérieure métallique et le supporte d’oxyde entraîne la formation des nanoparticules de Co en état très dispersés, qui sont résistants à l'oxydation. Sous la condition de réduction par H2, le graphène favorise clairement la réduction de Co. La quantité de dépôt de Co, le substrat d'oxyde, la température de calcination et l'environnement ont été prouvés pour pouvoir influencer la stabilité de graphène. Ces résultats ouvrent des nouvelles voies possibles d'utiliser le graphène comme promoteur dans des réactions catalytiques à l'avenirThe metal-support interaction (MSI) plays an important role in heterogeneous catalysis. Understanding and tuning the MSI are essential steps for developing catalysts with high performance. In this thesis, a new concept, which is coating the oxide supports with a single layer graphene, was introduced to modify the MSI. The influence of graphene layer on the metal (Co and Co-Pt) – oxide (ZnO and SiO2) interactions and on the redox properties of metal particles were evaluated through model catalyst systems. The results showed that single layer graphene can significantly influence the oxidation states and morphologies of both mono Co and bimetallic Co-Pt as compared to the one after direct deposition on bare oxides. In particular, under vacuum annealing, graphene protects Co from being oxidized by ZnO and results in Co-Pt metallic mixture. Co interacts with oxide substrates forming flat particles which are easily oxidized by low pressure O2, while insertion of a graphene interlayer between the metal overlayer and the oxide supports leads to the formation of highly dispersed Co nanoparticles, which are resistant to oxidation. Under H2 reduction condition, graphene evidently facilitates the reduction of Co. The deposition amount of Co, the oxide substrate, the annealing temperature and the environment were proved to influence the stability of graphene. These results explore new directions for the possible future of using graphene as a promoter in catalytic reactions
31
Xiao, Jie. "Layered lithium nickel manganese cobalt dioxide as a cathode material for Li-ion batteries." Diss., Online access via UMI:, 2008.
Find full text
32
Komissarenko, Dimitry. "Selective catalytic oxidation of methane to synthesis gas over complex oxides of cobalt and rare earth elements." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAF063/document.
Full textAbstract:
Pour la première fois l'oxydation partielle du méthane en gaz de synthèse a été effectué en présence de pérovskites lamellaires Nd2-xCaxCoO4±δ et La2-xSrxCoO4±δ (x = 0.75; 1.0). Nouveau catalyseur d'oxydation partielle NdCaCoO3.96 de méthane a été suggéré qui permet d’obtenir la sélectivité en gaz de synthèse proche de 100% avec 90% de la conversion de CH4 (T = 900ºC; CH4/O2 = 2; W = 20 L·g-1·h-1; brevet russe № 2433950, 21/04/2010). Le catalyseur a été active et stable au moins 140 h, aucune tendance à la désactivation n’a été observée. Sur la base des analyses DRX, MEB et MET, il a été déterminé que l'activité et la sélectivité élevées de NdCaCoO3.96 ainsi que la stabilité dans l'oxydation partielle du méthane sont dues à sa transformation au cours de la réaction de la structure initiale en des nanoparticules de cobalt métallique dispersées dans Nd2O3-CaO matrice. Il a été observé que l'activité des pérovskites lamellaires dans l'oxydation partielle du méthane dépend à la fois de la taille des particules métalliques actives formées et à la stabilité de la structure initialeFor the first time partial oxidation of methane to synthesis gas over layered perovskite-type oxides Nd2-xCaxCoO4±δ and La2-xSrxCoO4±δ (x = 0.75; 1.0) was investigated. New catalyst NdCaCoO3.96 for partial oxidation of methane was suggested allowing the selectivity toward synthesis gas close to 100% with 90% of CH4 conversion (T = 900ºC; CH4/O2 = 2; W = 20 L·g-1·h-1; Russian patent № 2433950, 21/04/2010). The catalyst was active and stable at least for 140 h, no trend to deactivation was observed. Based on XRD, SEM and TEM results it was determined that high activity and selectivity of NdCaCoO3.96 as well as stability in partial oxidation of methane are due to its transformation during reaction of initial structure to nanosized particles of metallic cobalt dispersed in Nd2O3-CaO matrix. It was observed that the activity of synthesized layered perovskite-type oxides in partial oxidation of methane depends both on the size of the formed active metallic particles and on the stability of initial structure
33
Ge, Dayang. "Direct Lithium-ion Battery Recycling to Yield Battery Grade Cathode Materials." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/92800.
Full textAbstract:
The demand for Lithium-ion batteries (LIBs) has been growing exponentially in recent years due to the proliferation of electric vehicles (EV). A large amount of lithium-ion batteries are expected to reach their end-of-life (EOL) within five to seven years. The improper disposal of EOL lithium-ion batteries generates enormous amounts of flammable and explosive hazardous waste. Therefore, cost-effectively recycling LIBs becomes urgent needs. Lithium nickel cobalt manganese oxides (NCM) are one of the most essential cathode materials for EV applications due to their long cycle life, high capacity, and low cost. In 2008, 18.9% of Lithium-ion batteries used NCM cathode material worldwide while this number increased to 31% six years later. An environment–friendly and low-cost direct recycling process for NCM has been developed in this project. The goal of this project is to recycle the EOL NCM and yield battery-grade NCM with equivalent electrochemical performance compared to virgin materials. In order to achieve this goal, four different heat treatment conditions are investigated during the direct recycling process. From the experimental results, the charge and discharge capacities of the recycled material are stable (between 151-155 mAh/g) which is similar to that of the commercial MTI NCM when sintered at 850 °C for 12 hours in the air. In addition, the cycling performance of recycled NCM is better than the commercial MTI NCM up to 100 cycles.Master of Science
The demand for Lithium-ion batteries has been growing exponentially in recent years due to the proliferation of electric vehicles. A large amount of lithium-ion batteries are expected to reach their end-of-life within five to seven years. The improper disposal of end-of-life lithium-ion batteries generates enormous amounts of flammable and explosive hazardous waste. Therefore, cost-effectively recycling Lithium-ion batteries becomes urgent needs. Lithium nickel cobalt manganese oxides are one of the most essential cathode materials for electric vehicles applications due to their long cycle life, high capacity, and low cost. In 2008, 18.9% of Lithium-ion batteries used Lithium nickel cobalt manganese oxides cathode material worldwide while this number increased to 31% six years later. An environment–friendly and low-cost direct recycling process for Lithium nickel cobalt manganese oxides material has been developed in this project. The goal of this project is to recycle the end-of-life manganese oxides cathode material. In order to achieve this goal, four different heat treatment conditions are investigated during the direct recycling process. From the experimental results, the cycling performance of recycled NCM is better than the commercial MTI NCM.
34
Shaw, Cynthia Kit Man. "Mass transport in mixed conducting perovskite related oxides." Thesis, Imperial College London, 2001. http://hdl.handle.net/10044/1/8380.
Full text
35
PEREIRA, LUCIANO F. D. "Estudo do gradiente de campo elétrico e da estrutura eletrônica do ZnO dopado com Co e Cd e do HfOsub(2) dopado com Ta por cálculos de primeiros princípios." reponame:Repositório Institucional do IPEN, 2011. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10031.
Full textAbstract:
Made available in DSpace on 2014-10-09T12:34:00Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:01:05Z (GMT). No. of bitstreams: 0
Tese (Doutoramento)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
36
Buselli, Lorenzo. "Study of Co-based hydrotalcite-derived mixed metal oxides partially modified with silver as potential catalysts for N2O decomposition." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/11930/.
Full textAbstract:
Co-Al-Ox mixed metal oxides partially modified with Cu or Mg, as well as Ag were successfully prepared, characterized and evaluated as potential catalysts for the N2O decomposition. The materials were characterized by the following techniques: X-Ray Diffraction, Thermogravimetric Analysis (TGA), N2 Physisorption, Hydrogen Temperature-Programmed Reduction (H2-TPR), and X-ray photoelectron spectroscopy (XPS). Ag-modified HT-derived mixed oxides showed enhanced activity compared to the undoped materials, the optimum composition was found for (1 wt.% Ag)CHT-Co3Al. The catalyst characterization studies suggested that the improved catalytic activity of Ag-promoted catalysts were mainly because of the altered redox properties of the materials.
37
Kenny, Leo Thomas. "Preparation and characterization of lithium cobalt oxide by chemical vapor deposition for application in thin film battery and electrochromic devices /." Thesis, Connect to Dissertations & Theses @ Tufts University, 1996.
Find full textAbstract:
Thesis (Ph.D.)--Tufts University, 1996.Adviser: Terry E. Haas. Submitted to the Dept. of Chemistry. Includes bibliographical references. Access restricted to members of the Tufts University community. Also available via the World Wide Web;
38
Olanipekun, Opeyemi B. "MBE Growth and Characterization of Graphene on Well-Defined Cobalt Oxide Surfaces: Graphene Spintronics without Spin Injection." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc1011813/.
Full textAbstract:
The direct growth of graphene by scalable methods on magnetic insulators is important for industrial development of graphene-based spintronic devices, and a route towards substrate-induced spin polarization in graphene without spin injection. X-ray photoelectron spectroscopy (XPS), low energy electron diffraction LEED, electron energy loss spectroscopy (EELS) and Auger electron spectroscopy (AES) demonstrate the growth of Co3O4(111) and CoO(111) to thicknesses greater than 100 Å on Ru(0001) surfaces, by molecular beam epitaxy (MBE). The results obtained show that the formation of the different cobalt oxide phases is O2 partial pressure dependent under same temperature and vacuum conditions and that the films are stoichiometric. Electrical I-V measurement of the Co3O4(111) show characteristic hysteresis indicative of resistive switching and thus suitable for advanced device applications. In addition, the growth of Co0.5Fe0.5O(111) was also achieved by MBE and these films were observed to be OH-stabilized. C MBE yielded azimuthally oriented few layer graphene on the OH-terminated CoO(111), Co0.5Fe0.5O(111) and Co3O4(111). AES confirms the growth of (111)-ordered sp2 C layers. EELS data demonstrate significant graphene-to-oxide charge transfer with Raman spectroscopy showing the formation of a graphene-oxide buffer layer, in excellent agreement with previous theoretical predictions. XPS data show the formation of C-O covalent bonding between the oxide layer and the first monolayer (ML) of C. LEED data reveal that the graphene overlayers on all substrates exhibit C3V. The reduction of graphene symmetry to C3V – correlated with C-O bond formation – enables spin-orbit coupling in graphene. Consequences may include a significant band gap and room temperature spin Hall effect – important for spintronic device applications. The results suggest a general pattern of graphene/graphene oxide growth and symmetry lowering for graphene formation on the (111) surfaces of rocksalt-structured oxides.
39
Lu, Yunxiang. "Study of electrochemical performance of strontium doped lanthanum cobalt oxides using electrochemical impedance spectroscopy and microelectrode array cell design /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/9818.
Full text
40
Malik, M. S. "Comparative studies of the electronic properties of copper tellurite glasses containing nickel, cobalt and lutetium oxides and cupric chloride." Thesis, Brunel University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235019.
Full text
41
Botero, Carrizosa Sara C. "Synthesis, Characterization, and Properties of Graphene-Based Hybrids with Cobalt Oxides for Electrochemical Energy Storage and Electrocatalytic Glucose Sensing." TopSCHOLAR®, 2017. http://digitalcommons.wku.edu/theses/1941.
Full textAbstract:
A library of graphene-based hybrid materials was synthesized as novel hybrid electrochemical electrodes for electrochemical energy conversion and storage devices and electrocatalytical sensing namely enzymeless glucose sensing. The materials used were supercapacitive graphene-family nanomaterials (multilayer graphene-MLG; graphene oxide-GO, chemically reduced GO-rGO and electrochemical reduced GOErGO) and pseudocapacitive nanostructured transition metal oxides including cobalt oxide polymorphs (CoO and Co3O4) and cobalt nanoparticles (CoNP). These were combined through physisorption, electrodeposition, and hydrothermal syntheses approaches. This project was carried out to enhance electrochemical performance and to develop electrocatalytic platforms by tailoring structural properties and desired interfaces. Particularly, electrodeposition and hydrothermal synthesis facilitate chemically-bridged (covalently- and electrostatically- anchored) interfaces and molecular anchoring of the constituents with tunable properties, allowing faster ion transport and increased accessible surface area for ion adsorption. The surface morphology, structure, crystallinity, and lattice vibrations of the hybrid materials were assessed using electron microscopy (scanning and transmission) combined with energy dispersive spectroscopy and selected-area electron diffraction, X-ray diffraction, and micro-Raman Spectroscopy. The electrochemical properties of these electrodes were evaluated in terms of supercapacitor cathodes and enzymeless glucose sensing platforms in various operating modes. They include cyclic voltammetry (CV), ac electrochemical impedance spectroscopy, charging-discharging, and scanning electrochemical microscopy (SECM).
These hybrid samples showed heterogeneous transport behavior determining diffusion coefficient (4⨯10-8 – 6⨯10-6 m2/s) following an increasing order of CoO/MLG < Co3O4/MLG < Co3O4/rGOHT < CoO/ErGO < CoNP/MLG and delivering the maximum specific capacitance 450 F/g for CoO/ErGO and Co3O4/ rGOHT. In agreement with CV properties, these electrodes showed the highest values of low-frequency capacitance and lowest charge-discharge response (0.38 s – 4 s), which were determined from impedance spectroscopy. Additionally, through circuit simulation of experimental impedance data, RC circuit elements were derived. SECM served to investigate electrode/electrolyte interfaces occurring at the solid/liquid interface operating in feedback probe approach and imaging modes while monitoring and mapping the redox probe (re)activity behavior. As expected, the hybrids showed an improved electroactivity as compared to the cobalt oxides by themselves, highlighting the importance of the graphene support. These improvements are facilitated through molecular/chemical bridges obtained by electrodeposition as compared with the physical deposition.
42
Macpherson, Brendan P. "Discrete cyano-bridged mixed valence systems /." [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17778.pdf.
Full text
43
Silva, Edison Luiz Salgado. "OBTENÇÃO DE SENSORES DE TEMPERATURA DO TIPO NTC A PARTIR DE MISTURA MECÂNICA DE ÓXIDOS DE NÍQUEL E COBALTO." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2011. http://tede2.uepg.br/jspui/handle/prefix/1404.
Full textAbstract:
Made available in DSpace on 2017-07-21T20:42:34Z (GMT). No. of bitstreams: 1
EdisonLuizSalgadoSilva.pdf: 3033456 bytes, checksum: 5e84d69fb23291317b8839b858970322 (MD5)
Previous issue date: 2011-08-30In this work it was characterized the microstructure and the electrical parameters of NTC temperature sensors, based on the mechanical mixing of niquel and cobalt oxides. Different proportions of this two materials (mol), was prepared and sintered at 1150C, 1200C, 1250C and 1300C. The microstructure was characterized by x-ray diffraction, MEV and EDS referring to the fases formed during the sintering, as well as, regarding grain size, the distribution of the chemical elements of this two oxides and the porosity of the final ceramic product. For the proportions of 10, 20, 30, 40, 50, 60, 80 e 90 (mol) of NiO on C3O4, and sintered on the four temperarures, it was obtained solid solution between niquel and cobalt oxides. Spinel phase, NiC2O4, was formed in the composition with 70 NiO (mol) at 1250C and 1300C, with segregation of CoO phase between the grain boundaries. The one phase composition with 60 (mol) NiO, sintered at 1250°C, and the composition with 70 (mol) NiO, sintered at 1300C, showed the best thermistor characteristics, by DC characterization. The values of beta factor, sensitivity and activation energy for the conductivity process (Ea), of the composition with 70 NiO was respectively 6203 K-1; -4,0 at (120C) and 0,53 eV.
No presente trabalho foi caracterizada a microestrutura e os parâmetros elétricos de sensores de temperatura do tipo NTC, a partir de mistura mecânica de óxidos de níquel e cobalto. Foram preparadas diferentes composições ( em mol ) entre os dois materiais e sinterizados nas temperaturas de 1150, 1200, 1250 e 1300C. A microestrutura foi caracterizada pela técnica de raios X, por MEV e EDS, no que se refere às fases formadas durante a sinterização, assim como, com respeito ao tamanho de grão, distribuição dos elementos e da porosidade do corpo cerâmico final. Para as composições de 10, 20, 30, 40, 50, 60, 80 e 90 em mol de NiO em C3O4, e sinterizadas nas quatro temperaturas, obteve-se a formação de soluções sólidas entre os óxidos de níquel e de cobalto. A composição de 70 em mol de NiO apresentou a formação da fase do espinélio NiC2O4, nas temperaturas de 1250 e 1300 C, com a segregação da fase de CO na região intergranular. As melhores características termistoras, obtidas pela caracterização elétrica DC, foram encontradas para a composição monofásica de 60 em mol de NiO, sinterizada a 1250C, e para a composição de 70 em mol de NiO sinterizada a 1300C. A composição de 70 de NiO apresentou uma constante termistora de 6203 K-1, sensibilidade igual a -4,0 (a 120C) e energia de ativação (Ea) para o processo de condução eletrônica de 0,53 eV.
44
Del, Pilar Albaladejo Joselyn. "Hydrothermal and Ambient Temperature Anchoring of Co (II) Oxygen Evolution Catalyst on Zeolitic Surfaces." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1416483756.
Full text
45
Tourinho, Francisco. "Ferrofluides a base de ferrite de cobalt et de ferrite de manganese : elaboration, comportement physicochimique et magnetique." Paris 6, 1988. http://www.theses.fr/1988PA066570.
Full text
46
Klingan, Katharina [Verfasser]. "New insight in structure-function relations of water-oxidising cobalt and nickel oxides by electrochemistry combined with X-ray absorption spectroscopy / Katharina Klingan." Berlin : Freie Universität Berlin, 2016. http://d-nb.info/1083986449/34.
Full text
47
Wahl, Sebastian [Verfasser], Nicola [Gutachter] Pinna, Klaus [Gutachter] Rademann, and Holger [Gutachter] Dau. "Shed Light on Cobalt Oxides for the Oxygen Evolution Reaction – An Operando Spectroelectrochemical Study / Sebastian Wahl ; Gutachter: Nicola Pinna, Klaus Rademann, Holger Dau." Berlin : Humboldt-Universität zu Berlin, 2020. http://d-nb.info/1204424772/34.
Full text
48
Hillebrand, Philipp [Verfasser], Sebastian [Akademischer Betreuer] Fiechter, Peter [Akademischer Betreuer] Strasser, and Wolfram [Akademischer Betreuer] Calvet. "Structure function relationships of cobalt and manganese oxides as catalysts for (photo) electrochemical water splitting / Philipp Hillebrand. Gutachter: Sebastian Fiechter ; Peter Strasser ; Wolfram Calvet." Berlin : Technische Universität Berlin, 2015. http://d-nb.info/1077247087/34.
Full text
49
Mandia, David J. "NC-AFM and XPS Investigation of Single-crystal Surfaces Supporting Cobalt (III) Oxide Nanostructures Grown by a Photochemical Method." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23117.
Full textAbstract:
The work of this thesis comprises extensive Noncontact Atomic Force Microscopy (NC-AFM) characterization of clean metal-oxide (YSZ(100)/(111) and MgO(100)) and graphitic (HOPG) supports as templates for the novel, photochemically induced nucleation of cobalt oxide nanostructures, particularly Cobalt (III) Oxide. The nanostructure-support surfaces were also studied by X-ray Photoelectron Spectroscopy (XPS) to verify the nature of the supported cobalt oxide and to corroborate the surface topographic and phase NC-AFM data. Heteroepitaxial growth of Co2O3 nanostructures proves to exhibit a variety of different growth modes based on the structure of the support surface. On this basis, single-crystal support surfaces ranging from nonpolar to polar and atomically flat to highly defective and reactive were chosen, again, yielding numerous substrate-nanostructure interactions that could be probed by high-performance surface science techniques.
50
Zakri, Waleed. "Fabrication and Simulation of Semi-Solid Electrodes for Flexible Lithium-Ion Batteries." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1531480028749308.
Full text