Academic literature on the topic 'Cobalt oxide (Co3O4)'
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Journal articles on the topic "Cobalt oxide (Co3O4)"
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Eliseeva, E. A., S. L. Berezina, I. G. Gorichev, L. E. Slynko, and V. N. Goryacheva. "The Initial Surface Structure of Co3O4 as a Factor of Influence on Kinetic Features of the Dissolution of the Solid Phase." Herald of the Bauman Moscow State Technical University. Series Natural Sciences, no. 4 (91) (August 2020): 138–44. http://dx.doi.org/10.18698/1812-3368-2020-4-138-144.
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Due to the depletion of natural reserves of cobalt-containing ores, it is urgent to optimize the processes of cobalt replenishment, based on the leaching of its compounds, processing of industrial waste, regeneration of cobalt compounds from catalysts. The kinetic characteristics of the dissolution of metal oxides are influenced by the initial state of their surface structure, which requires the accumulation of experimental material and individual targeted studies. The paper presents the results of an experimental study of the surface structure of industrial Co3O4 cobalt oxide samples. The studies were carried out by electron microscopy and X-ray phase analysis and revealed the size and shape of the Co3O4 particles and the nature of their surface distribution. The correspondence of experimental and theoretical data has been established, Co3O4 cobalt oxide has been identified as an α-form of the cubic crystal system. The data obtained are of interest in the study of the effect of the surface characteristics of the solid phase of Co3O4 cobalt oxide on the dissolution kinetics under the chemical and electrochemical influence
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Lendzion-Bieluń, Zofia, Roman Jędrzejewski, and Walerian Arabczyk. "The effect of aluminium oxide on the reduction of cobalt oxide and thermostabillity of cobalt and cobalt oxide." Open Chemistry 9, no. 5 (October 1, 2011): 834–39. http://dx.doi.org/10.2478/s11532-011-0059-x.
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AbstractDuring precipitation and calcination at 200°C nanocrystalline Co3O4 was obtained with average size crystallites of 13 nm and a well developed specific surface area of 44 m2 g−1. A small addition of a structural promoter, e.g. Al2O3, increases the specific surface area of the cobalt oxide (54 m2 g−1) and decreases the average size of crystallites (7 nm). Al2O3 inhibits the reduction process of Co3O4 by hydrogen. Reduction of cobalt oxide with aluminium oxide addition runs by equilibrium state at all the respective temperatures. The apparent activation energy of the recrystallization process of the nanocrystalline cobalt promoted by the aluminium oxide is 85 kJ mol−1. Aluminium oxide improves the thermostability of both cobalt oxide and the cobalt obtained as a result of oxide phase reduction.
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Абдуллин, Х. А., С. К. Жумагулов, Г. А. Исмаилова, Ж. К. Калкозова, В. В. Кудряшов, and А. С. Серикканов. "Синтез гетерогенных наноструктур ZnO/Co-=SUB=-3-=/SUB=-O-=SUB=-4-=/SUB=- методом химического осаждения из растворов." Журнал технической физики 90, no. 7 (2020): 1184. http://dx.doi.org/10.21883/jtf.2020.07.49454.317-19.
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Nanocrystalline cobalt oxide Co3O4 and the ZnO / Co3O4 composite were obtained by the chemical bath deposition method followed by thermal annealing. It has been shown that the growth mechanism of cobalt carbonates changes dramatically in the presence of zinc oxide particles during synthesis, as a result, the phase composition, morphology, and material properties change. The conductive layers formed from the ZnO / Co3O4 composite have an electrical resistance at room temperature that is more than three orders of magnitude lower than the resistance of the Co3O4 layers, and ZnO / Co3O4 composite gas sensors showed significantly higher gas sensitivity at room temperature than that of control cobalt oxide sensors.
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Zeng, H. C., J. Lin, and K. L. Tan. "Memory effect of ZrO2 matrix on surface Co3O4–CoO transition." Journal of Materials Research 10, no. 12 (December 1995): 3096–105. http://dx.doi.org/10.1557/jmr.1995.3096.
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Cobalt oxide system Co3O4-CoO has been studied on the ZrO2 matrix surfaces with FTIR and XPS. The tetragonal and monoclinic ZrO2 matrix materials have been synthesized from the Zr-n-propoxide-acetylacetone-water-isopropanol system. The study shows that the ZrO2 matrix is able to retain the relative Co3O4:CoO population at elevated temperatures. The thermodynamically stable oxide population (Co3O4:CoO) at room temperature for ZrO2-supported Co3O4-CoO is about 50:50 (Co2+ :Co3+ = 2:1), which is markedly different from the 100:0 case (Co2+ :Co3+ = 1:2) for an unsupported Co3O4-CoO surface oxide system. The relative Co3O4 :CoO ratio in the surface region of the ZrO2 is temperature dependent but matrix-polymorph independent. The composition of an oxide solid solution formed by the Co3O4-CoO and matrices of ZrO2 is determined to have a cobalt molar percentage of 4.5%. Diffusion thermodynamic quantities are investigated, and the measured diffusion activation energy for a cobalt ion in the ZrO2 matrices is 0.21 eV. The mechanism of the ZrO2 memory effect on surface Co3O4-CoO transition will also be addressed.
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Zhang, Weidong, Paola Anguita, Javier Díez-Ramírez, Claude Descorme, Jose Luis Valverde, and Anne Giroir-Fendler. "Comparison of Different Metal Doping Effects on Co3O4 Catalysts for the Total Oxidation of Toluene and Propane." Catalysts 10, no. 8 (August 3, 2020): 865. http://dx.doi.org/10.3390/catal10080865.
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Metal-doped (Mn, Cu, Ni, and Fe) cobalt oxides were prepared by a coprecipitation method and were used as catalysts for the total oxidation of toluene and propane. The metal-doped catalysts displayed the same cubic spinel Co3O4 structure as the pure cobalt oxide did; the variation of cell parameter demonstrated the incorporation of dopants into the cobalt oxide lattice. FTIR spectra revealed the segregation of manganese oxide and iron oxide. The addition of dopant greatly influenced the crystallite size, strain, specific surface area, reducibility, and subsequently the catalytic performance of cobalt oxides. The catalytic activity of new materials was closely related to the nature of the dopant and the type of hydrocarbons. The doping of Mn, Ni, and Cu favored the combustion of toluene, with the Mn-doped one being the most active (14.6 × 10−8 mol gCo−1 s−1 at 210 °C; T50 = 224 °C), while the presence of Fe in Co3O4 inhibited its toluene activity. Regarding the combustion of propane, the introduction of Cu, Ni, and Fe had a negative effect on propane oxidation, while the presence of Mn in Co3O4 maintained its propane activity (6.1 × 10−8 mol gCo−1 s−1 at 160 °C; T50 = 201 °C). The excellent performance of Mn-doped Co3O4 could be attributed to the small grain size, high degree of strain, high surface area, and strong interaction between Mn and Co. Moreover, the presence of 4.4 vol.% H2O badly suppressed the activity of metal-doped catalysts for propane oxidation, among them, Fe-doped Co3O4 showed the best durability for wet propane combustion.
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Gorimbo, Joshua, Ralph Muvhiiwa, Ephraim Llane, and Diane Hildebrandt. "Cobalt Catalyst Reduction Thermodynamics in Fischer Tropsch: An Attainable Region Approach." Reactions 1, no. 2 (November 17, 2020): 115–29. http://dx.doi.org/10.3390/reactions1020010.
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A fundamental understanding of the precise reduction reaction pathway of cobalt-based catalysts is a crucial piece of knowledge in terms of the Fischer–Tropsch Synthesis (FTS) reaction. The use of hydrogen (H2) as the reduction agent results in a two-stage reduction of cobalt tetraoxide (Co3O4) to cobalt oxide (CoO) and then to metallic Co. The objective of the present work is to apply the Thermodynamic Attainable Region (TAR) to cobalt catalyst reduction using H2 so as to gain better insight regarding the thermodynamics of reduction reaction. TAR space diagrams suggest that complete Co3O4 reduction is feasible through two reaction pathways. Thus, the observed AR results suggest that the temperature programmed reduction’s (TPR) first reaction peak may be attributed to direct reduction of Co3O4 → Co and/or reduction to an intermediate compound Co3O4 → CoO. The second peak is a result of the reduction of either of the cobalt oxides to Co (Co3O4 → Co or CoO → Co).
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Shi, Peng Hui, Shao Bo Zhu, Rui Jing Su, Jin Tao Ren, Deng Xin Li, and Shi Hong Xu. "Synthesis of Co3O4/RGO as Catalyst for Degradation of Orange II in Water by Advanced Oxidation Processes Based on Sulfate Radicals." Advanced Materials Research 534 (June 2012): 269–72. http://dx.doi.org/10.4028/www.scientific.net/amr.534.269.
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One step synthesis reduced graphene oxide and cobalt oxides nanocomposites (Co3O4/RGO) in ethylene glycol as heterogeneous catalyst. The Co3O4/RGO was confirmed by X-ray diffraction (XRD). And Co3O4/RGO exhibits an unexpected, surprisingly high catalytic activity in degradation of Orange II in water by advanced oxidation processes based on sulfate radicals and 100% decomposition could be achieved in 16 min.
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Abudayyak, Mahmoud, Tuba Altincekic Gurkaynak, and Gül Özhan. "In vitro evaluation of cobalt oxide nanoparticle-induced toxicity." Toxicology and Industrial Health 33, no. 8 (June 9, 2017): 646–54. http://dx.doi.org/10.1177/0748233717706633.
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Cobalt oxide (Co3O4) nanoparticles have applications in nanomedicine and nanotechnology; therefore, any possible adverse effects require thorough investigation. The present study investigated the effects of Co3O4 nanoparticles on four different cell lines: liver, HepG2 hepatocellular carcinoma cells; lung, A549 lung carcinoma cells; gastrointestinal, Caco-2 colorectal adenocarcinoma cells; and nervous system, SH-SY5Y neuroblastoma cells. A difference was observed in cell sensitivity toward Co3O4 nanoparticles. Co3O4 nanoparticles were taken up by all the cell types. However, no cell death was observed in HepG2, Caco-2, or SH-SY5Y cells; only A549 cells showed cytotoxicity at relatively high exposure concentrations. Co3O4 nanoparticles did not induce DNA damage or apoptosis in the cell lines tested except in A549. Interestingly, Co3O4 nanoparticles induced cellular oxidative damage in all cell types except Caco-2, resulting in increased malondialdehyde and 8-hydroxydeoxyguanosine levels and decreased glutathione levels. According to our results, it could be indicated that high concentrations of Co3O4 nanoparticles affected the pulmonary system but were unlikely to affect the liver, nervous system, or gastrointestinal system. Co3O4 nanoparticles might be safely used for industrial, commercial, and nanomedical applications if dose rates are adjusted depending on the route of exposure. However, further in vivo and in vitro studies are required to confirm the safety of Co3O4 nanoparticles.
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Lusiana, Lusiana, and Sigit Dwi Yudanto. "Pembentukan Fasa Co3O4 Dengan Metoda Dekomposisi CoCO3 Menggunakan Sinar Diffraksi." Jurnal Teknik Mesin 12, no. 2 (December 31, 2019): 46–49. http://dx.doi.org/10.30630/jtm.12.2.262.
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Experiments have been carried out to obtain the decomposition of cobalt carbonate cobalt oxide to be used as raw material for the manufacture of calcium cobalt oxide thermoelectric materials. The experiments were performed by heating cobalt carbonate powder material (CoCO3) from Kanto Chemical with a temperature of 1000°C. Heating aims to obtain Co3O4 phase. Co3O4 phase is what will be used in the manufacture of thermoelectric materials based on the phase diagram of the system Ca-Co-O. The results of X-ray diffraction CoCO3 materials are heated to 1000°C showed that Co3O4 phase has been formed. Analysis quantitative diffraction pattern shows the diffraction peaks are the property throughout the Co3O4 phase. The crystal structure of Co3O4 is Face Centered Cubic (FCC) with space group F d -3 m. Lattice parameters of the diffraction pattern is the result of smoothing a = 8.0838 Å.
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Wang, Hong Juan, Dong Zhou, Feng Peng, and Hao Yu. "Facile Synthesis and Performance of Reduced Graphene Oxide/Cobalt Oxide Composite for Supercapacitor." Advanced Materials Research 785-786 (September 2013): 779–82. http://dx.doi.org/10.4028/www.scientific.net/amr.785-786.779.
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A series of reduced graphene oxide/cobalt oxide composites (Co3O4/rGO)were fabricated via a chemical precipitation approach and subsequent calcination in Ar atmosphere. Experimental results show that Co3O4/rGO composite with 86 wt% of Co3O4 loading exhibits the optimum specific capacitance of 240 F g-1 in 6.0 M KOH electrolyte at the current density of 0.8 A g-1, excellent quick charge-discharge performance and outstanding cyclic stability with 2.3% of its specific capacitance increase after 2400 cycles at the current density of 8 A g-1 in GCD test, exhibiting significant potential of Co3O4 /rGO composite in the application of supercapacitors.
Dissertations / Theses on the topic "Cobalt oxide (Co3O4)"
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Kabre, Tushar Shriram. "Co3O4 Thin Films: Sol-Gel Synthesis, Electrocatalytic Properties & Photoelectrochemistry." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1316552072.
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Godillot, Gérôme. "Electrodes pour supercondensateurs à base d’oxydes de cobalt conducteurs." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14597/document.
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Les travaux de recherche actuels menés dans le domaine des supercondensateurs s’orientent vers l’augmentation des densités d’énergie, notamment via le développement de supercondensateurs hybrides "oxydes de métaux de transition / carbones activés". Dans ce contexte, les présents travaux avaient pour objectif d’évaluer les propriétés d’oxydes de cobalt nanométriques en tant que matériaux d’électrode positive pour supercondensateur hybride.Ces oxydes de cobalt, de structure spinelle, sont préparés par précipitation de nitrate de cobalt en milieu basique (T < 90 °C). Ils possèdent une formule chimique du type HxLiyCo3-δO4•zH2O et présentent une bonne conductivité électronique grâce à la présence d’ions H+, Li+ et Co4+. Les analyses par DRX, ATG, RMN et les mesures de conductivité électroniques ont mis en évidence une réorganisation de la structure spinelle de ces matériaux sous l’effet d’un traitement thermique, conduisant à une augmentation du rapport Co4+/Co3+ ainsi qu’à une amélioration des propriétés de transport électrique. L’association d’une conductivité électronique élevée et d’une forte surface spécifique confère à ces oxydes des performances prometteuses en tant que matériaux d’électrode.L’étude des propriétés électrochimiques a montré la présence de deux modes de stockage des charges, l’un électrostatique (double couche électrochimique) et l’autre faradique via l’oxydation et la réduction du cobalt. Elle a également permis de déterminer la signature électrochimique de ces oxydes (capacité, fenêtre de potentiels), prérequis indispensable à leur intégration dans une cellule complète. Finalement, un supercondensateur hybride "oxyde de cobalt / carbone activé" a été assemblé et équilibré, donnant lieu à des performances attractives (61,6 F/g sur 1,60 V)Investigations on supercapacitors are focusing on increasing energy densities, in particular with the development of hybrid supercapacitors "metal oxides / activated carbons". In this field, the present work aims at evaluating nanometric cobalt oxides as positive electrode material for hybrid supercapacitors.These oxides, with spinel structure, are synthesized by precipitation of cobalt nitrate in a basic medium (T < 90 °C). They exhibit formulae such as HxLiyCo3-δO4•zH2O and good electronic properties thanks to the presence of H+, Li+ and Co4+ ions. XRD, TGA, NMR analysis as well as electronic measurements have highlighted a structural reorganization of the spinel structure under thermal treatment, resulting in increase of the Co4+/Co3+ ratio and an enhancement of the electronic transport properties. The high electronic conductivity together with a huge specific surface area imparts these oxides promising performances as electrode material.The study of the electrochemical properties underlines two charge storage mechanisms, one electrostatic (electrochemical double layer) and the other one faradic through the oxidation and the reduction of cobalt. The electrochemical signature (capacity, potential window) of these oxides was also determined in order to develop a complete cell. Finally, a hybrid supercapacitor "cobalt oxide / activated carbon" was assembled and balanced, revealing attractive performances (61,6 F/g over 1,60 V)
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Li, Yanguang. "Nanostructured Materials for Energy Applications." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1275610758.
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Woods, Matthew P. "Activity and Selectivity in Oxidation Catalysis." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1228175906.
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Malecki, Andrzej. "Décomposition thermique et propriétés électriques de Co3O4." Phd thesis, Université Sciences et Technologies - Bordeaux I, 1985. http://tel.archives-ouvertes.fr/tel-00835492.
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La cinétique de la décomposition thermique de Co3O4 a été étudiée sur des échantillons pulvérulent ou monocristallins. La formation d'une couche compacte de monoxyde de cobalt ainsi que la forme de l'équation décrivant les courbes degré de décomposition-temps ont abouti au développement d'un modèle dans lequel la cinétique est limitée par la diffusion de l'oxygène à travers la couche. Ce modèle dérive de celui de Ginstling et Brounshtein tient compte de la variation de l'énergie d'activation avec le degré de décomposition. Une interprétation des propriétés électriques de Co3O4 pur et dopé est également proposée.
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Lopes, Vinícius Ferreira. "Sensors of volatile organic compounds based on Co3O4 and V2O5 and their composites with graphene oxide /." São José do Rio Preto, 2020. http://hdl.handle.net/11449/192885.
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Orientador: Diogo Paschoalini VolantiResumo: O avanço na ciência e tecnologia de sensores de compostos orgânicos voláteis (VOCs) é importante para o desenvolvimento sustentável de materiais funcionais. A dissertação de mestrado refere-se à avaliação do uso de óxido de grafeno (GO, sigla em inglês) em óxido metálicos (OM) tipo-n (V2O5) e tipo-p (Co3O4) para melhorar a sensibilidade, a seletividade e o tempo de resposta dos sensores. O GO teve uma modificação sendo submetido a um processo oxidativo. Os OMs nano ou microestrurados foram preparados a partir de seus sais ou por processos de ressolubilização dos óxidos. Por fim, os compósitos GO-OM foram preparados após os percursores ficarem em suspensão com o GO por 24 horas. O GO aumentou a adsorção gasosa dos compostos resultando em maior seletividade e sensibilidade. Por outro lado, os principais benefícios das estruturas nano e microestrutruradas dos OMs seriam a maior área superficial do material resultando em melhores propriedades gasosas, resultando em mais sítios ativos para adsorção do oxigênio e das moléculas do gás analito. As respostas sensoras foram avaliadas na presença de diferentes concentrações (nas faixas de ppm e ppb) de VOCs (ex.: acetona, acetaldeído, etanol, metanol, benzeno, xileno e tolueno) em atmosfera seca.
Abstract: The advancement in science and technology of volatile organic compounds (VOCs) sensors is essential for the sustainable development of functional materials. The master's thesis refers to the evaluation of the use of graphene oxide (GO) in metallic oxides (OM) type-n (V2O5) and type-p (Co3O4) to improve sensitivity, selectivity and the response time of the sensors. The GO had a modification being subjected to an oxidative process. The nano or microstructured OMs were prepared from its precursors. Finally, the GO-OM composites were prepared after the precursors were in suspension with the GO for 24 hours. The GO increased the gaseous adsorption of the compounds resulting in greater selectivity and sensitivity. On the other hand, the main benefits of the nanostructured and micro-structured structures of OMs would be the greater surface area of the material resulting in better gaseous properties, resulting in more active sites for adsorption of oxygen and analyte gas molecules. The sensory responses were evaluated in the presence of different concentrations (in the ppm and ppb ranges) of VOCs (e.g., acetone, acetaldehyde, ethanol, methanol, benzene, xylene and toluene) in a dry atmosphere.
Mestre
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Godillot, Gérôme. "Electrodes pour supercondensateurs à base d'oxydes de cobalt conducteurs." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2012. http://tel.archives-ouvertes.fr/tel-00986640.
Full textAbstract:
Les travaux de recherche actuels menés dans le domaine des supercondensateurs s'orientent vers l'augmentation des densités d'énergie, notamment via le développement de supercondensateurs hybrides "oxydes de métaux de transition / carbones activés". Dans ce contexte, les présents travaux avaient pour objectif d'évaluer les propriétés d'oxydes de cobalt nanométriques en tant que matériaux d'électrode positive pour supercondensateur hybride.Ces oxydes de cobalt, de structure spinelle, sont préparés par précipitation de nitrate de cobalt en milieu basique (T < 90 °C). Ils possèdent une formule chimique du type HxLiyCo3-δO4*zH2O et présentent une bonne conductivité électronique grâce à la présence d'ions H+, Li+ et Co4+. Les analyses par DRX, ATG, RMN et les mesures de conductivité électroniques ont mis en évidence une réorganisation de la structure spinelle de ces matériaux sous l'effet d'un traitement thermique, conduisant à une augmentation du rapport Co4+/Co3+ ainsi qu'à une amélioration des propriétés de transport électrique. L'association d'une conductivité électronique élevée et d'une forte surface spécifique confère à ces oxydes des performances prometteuses en tant que matériaux d'électrode.L'étude des propriétés électrochimiques a montré la présence de deux modes de stockage des charges, l'un électrostatique (double couche électrochimique) et l'autre faradique via l'oxydation et la réduction du cobalt. Elle a également permis de déterminer la signature électrochimique de ces oxydes (capacité, fenêtre de potentiels), prérequis indispensable à leur intégration dans une cellule complète. Finalement, un supercondensateur hybride "oxyde de cobalt / carbone activé" a été assemblé et équilibré, donnant lieu à des performances attractives (61,6 F/g sur 1,60 V).
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Liu, Xuemei. "Conception en voie sèche de catalyseurs propres Co/Al2O3 pour la synthèse Fischer-Tropsch et modélisation numérique DEM." Thesis, Ecole centrale de Lille, 2018. http://www.theses.fr/2018ECLI0013.
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Ce travail de thèse concerne l’application d’une nouvelle technologie de préparation de catalyseurs propres Co/Al2O3 pour la synthèse de Fischer Tropsch (FT). Les matériaux sont préparés à l’aide d’un procédé de revêtement à sec dans un mélangeur à haut cisaillement le «Picomix». Les conditions opératoires, les supports en alumine, la taille des cristallites de cobalt et la teneur en charge de cobalt ont été optimisés pour augmenter l’activité catalytique du Co/Al2O3. De même, une modélisation DEM a été effectuée pour décrire le comportement des poudres dans le mélangeur. Les résultats expérimentaux montrent une très bonne adhésion des nanoparticules de Co3O4 à la surface des particules de Al2O3 pour une vitesse de rotation élevée pendant une courte période. Les particules γ-Al2O3 traitées thermiquement présentent une résistance mécanique améliorée des catalyseurs, mais une activité catalytique relativement faible. La taille des cristallites de Co3O4 a diminué de 64nm à 11nm après broyage dans un broyeur à boulets planétaire à 600 rpm/min pendant 40h. Enfin, le catalyseur optimal a été obtenu à 5000 rpm/min pendant 5min avec 5% en poids de cobalt. Le catalyseur obtenu présente des résultats catalytiques : conversion élevée en CO (37%) , sélectivité élevée en hydrocarbures en C5+ (75%) et faible sélectivité en CH4 (13%) à 250oC. La modélisation numérique par DEM a révélé que les paramètres liés aux conditions opératoires, la géométrie du dispositif et aux propriétés intrinsèques des particules avaient un impact sur le comportement des particules et la qualité de l’enrobage des matériauxThis thesis concerns the application of a novel preparation technology for Co/Al2O3 clean catalysts applied in Fischer Tropsch (FT) synthesis. The catalysts were prepared using a dry coating process in a high shear mixer “Picomix”. The operating conditions, alumina supports, cobalt crystallite size and cobalt loading content were optimized to increase the catalytic activity of Co/Al2O3 catalysts. Besides, DEM modeling was performed to describe the behavior or powders in the mixer. Experimental results showed a very good adhesion of the nano Co3O4 particles on the surface of Al2O3 particles after processed in the mixer under a high rotational speed and a short time. The heat-treated Al2O3γ particles presented enhanced mechanical strength of catalysts, however, exhibited relatively low catalytic activity. The Co3O4 crystallite size decreased from 64 nm to 11 nm after milling in planetary ball mill under 600 rpm for 40 h. Finally, the optimal catalyst was prepared by mixing milled-Co3O4 and Al2O3γ particles in “Picomix” under 5000 rpm for 5 min with 5 wt.% of Co. The obtained catalyst presented high CO conversion (37 %), high C5+ hydrocarbons selectivity (75 %) and low CH4 selectivity (13 %) in FT synthesis reaction at 250 oC. The DEM mumerical modeling revealed that the parameters related to operating condition, device geometry, and particle intrinsic properties had an impact on particle behavior and coating quality of materials
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de, Jongh Leigh-Anne. "The molecular precursor approach to control the morphology of Co₃O₄ on support materials." Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/2539.
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In this project, the TMP method was employed to produce “active sites.” These active sites are for influencing and controlling the Co₃O₄ growth. One of the aims was to investigate what effect the grafting of the molecular precursor has on the nature and distribution of active sites on the various support materials. The second aim was to investigate the effect an increase in molecular precursor loading, in various impregnation steps, has on the nature and distribution of the active sites. The third aim was to investigate the effect of the steric constraints of ligand groups, by changing the molecular precursor, on the nature and distribution of active sites. The fourth aim was to use the different aspects discussed above and apply them to investigate what effect the above-mentioned modifications have on Co₃O₄ morphology. While another aim was to investigated what effect varying the quantity of Co(NO₃)₂•6H₂O has on Co₃O₄ morphology. Lastly, we investigated what effect varying the impregnation procedure and calcination temperature have on the Co₃O₄ morphology. The effect the support has on the phase of titanium molecular precursor was investigated using molecular precursor, ⁱPrOTi[OSi(O[superscript(t)]Bu₃)]₃. The supports used were Silica 922, NanoDur, Aerosil 200, Stöber spherical silica, SBA-15, mod MCM-41 and sMCM-41. The molecular precursor ⁱPrOTi[OSi(O[superscript(t)]Bu₃)]₃ was revealed to be in the orthorhombic TiO₂ with space group P(cab), normal brookite lattice, on Silica 922 after calcination but only an isolated area displaying this morphology. Generally we do not observe any TiO₂ on the support, which indicates that we have produce site-isolated sites, suggesting the TMP method has been successful on all of the various supports. The emphasis is placed on the effect of this molecular precursor and the respective support has on the Co₃O₄ morphology in Chapter 3. In this Chapter, a unique morphology was observed on Silica 922 which showed Co₃O₄ nanorods of cubic Co₃O₄ in the space group Fd-3m. Silica 922 was used for the remainder of the thesis to investigate the effect the quantity of molecular precursor has on the nature of active sites and Co₃O₄ morphology in Chapter 4. This support was also used to investigate the effect the amount of Co(NO₃)₂•6H₂O has on Co₃O₄ morphology in Chapter 5. This support was lastly used to investigate the steric constraints of the ligand groups, Ti[OSi(O[superscript(t)]Bu)₃]₄ (TiSi4), ⁱPrOTi[OSi(O[superscript(t)]Bu)₃]₃ (TiSi3), (OtBu)₃TiOSi(O[superscript(t)]Bu)₃ (TiSi) and the least sterically constrained Ti(OⁱPr)₄ has on the loading of precursor and Co₃O₄ morphology in Chapter 6.
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Pezzotti, Simone. "DFT-MD simulations and theoretical SFG spectroscopy to characterize H-Bonded networks at aqueous interfaces : from hydrophobic to hydrophilic environments Structural definition of the BIL and DL: a new universal methodology to rationalize non-linear χ(2)(ω) SFG signals at charged interfaces, including χ(3)(ω) contributions What the Diffuse Layer (DL) Reveals in Non-Linear SFG Spectroscopy 2D H-Bond Network as the Topmost Skin to the Air-Water Interface Combining ab-initio and classical molecular dynamics simulations to unravel the structure of the 2D-HB-network at the air-water interface 2D-HB-Network at the air-water interface: A structural and dynamical characterization by means of ab initio and classical molecular dynamics simulations Spectroscopic BIL-SFG Invariance Hides the Chaotropic Effect of Protons at the Air-Water Interface Molecular hydrophobicity at a macroscopically hydrophilic surface Graph theory for automatic structural recognition in molecular dynamics simulations DFT-MD of the (110)-Co3O4 cobalt oxide semiconductor in contact with liquid water, preliminary chemical and physical insights into the electrochemical environment." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLE008.
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Améliorer notre connaissance de la structure de l'eau dans l'environnement spécial offert par une interface est essentiel pour la compréhension de nombreux phénomènes naturels et applications technologiques. Pour révéler cette structure interfaciale de l'eau, des techniques capables de fournir des informations microscopiques, de manière sélective, pour cette couche interfaciale (BIL) sont nécessaires. Dans le présent travail de thèse, nous avons donc étudié les interfaces aqueuses au niveau moléculaire, en couplant la modélisation théorique à partir de simulations DFT-MD avec les spectroscopies SFG et THz-IR. En développant de nouveaux protocoles/outils d'investigation associant simulations DFT-MD et spectroscopie SFG, en particulier pour la rationalisation plus complexe des interfaces chargées, nous avons fourni une compréhension globale de l'effet des conditions interfaciales d'hydrophilicité, de pH, de force ionique sur le réseau des liaisons-H formé dans la couche interfaciale BIL, sur ses signatures spectroscopiques et sur son impact sur les propriétés physico-chimiques. Nous avons montré pour la première fois que, dans des conditions suffisamment hydrophobes, l'eau interfaciale crée des réseaux des liaisons-H bidimensionnels, révélé expérimentalement par les spectres THz-IR. Le réseau-2D dicte la dynamique de l'eau interfaciale, le potentiel de surface, l'acidité de surface, la tension superficielle et la thermodynamique d'hydratation des solutés hydrophobes. Cet "ordre horizontal" aux interfaces hydrophobes est opposé à "l'ordre verticale" obtenu aux interfaces hydrophiles. Nous avons aussi révélé comment les ions et les conditions de pH modifient ces arrangements structurauxImproving our knowledge on water H-Bonded networks formed in the special environment offered by an interface is pivotal for our understanding of many natural phenomena and technological applications. To reveal the interfacial water arrangement, techniques able to provide detailed microscopic information selectively for the interfacial layer are required. In the present thesis work, we have hence investigated aqueous interfaces at the molecular level, by coupling theoretical modeling from DFT-MD simulations with SFG & THz-IR spectroscopies. By developing new investigation protocols/tools, coupling DFT-MD simulations and SFG spectroscopy, in particular for the more complex rationalization of charged interfaces, we have provided a global comprehension of the effect of various interfacial conditions (hydrophilicity, pH, ionic strength) on the HB-Network formed in the interfacial layer (BIL), on its spectroscopic signatures and on its impact on physico-chemical properties. We have shown for the first time that, in sufficiently hydrophobic conditions, BIL interfacial water creates special 2-Dimensional HB-Networks, experimentally revealed by one specific THz-IR marker band. Such 2D-network dictates HBs and orientational dynamics of interfacial water, surface potential, surface acidity, water surface tension and thermodynamics of hydration of hydrophobic solutes. Such "horizontal ordering” of water at hydrophobic interfaces is found opposite to the “vertical ordering” of water at hydrophilic interfaces, while coexistence of the two orders leads to disordered interfacial water in intermediate hydrophilic/hydrophobic conditions. Both DFT-MD and SFG further revealed how ions & pH conditions alter these BIL-water orders
Book chapters on the topic "Cobalt oxide (Co3O4)"
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Arora, Ekta, Ritu Chaudhary, Sacheen Kumar, and Dinesh Kumar. "Synthesis and Characterization of Copper Doped Cobalt Oxide (Co3O4) by Co-precipitation Method." In Springer Proceedings in Physics, 177–83. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-29096-6_23.
Full textConference papers on the topic "Cobalt oxide (Co3O4)"
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Glukhova, Olga E., Michael M. Slepchenkov, and Dmitriy A. Kolosov. "2D monocrystalline nanostructures of cobalt oxide Co3O4 for sensing individual molecules." In Reporters, Markers, Dyes, Nanoparticles, and Molecular Probes for Biomedical Applications XII, edited by Samuel Achilefu and Ramesh Raghavachari. SPIE, 2020. http://dx.doi.org/10.1117/12.2546528.
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Mueller, M., R. Henne, G. Schiller, M. I. Boulos, F. Gitzhofer, and R. B. Heimann. "Radio-Frequency Suspension Plasma Spraying of Cobalt Spinel Anodes for Alkaline Water Electrolysis." In ITSC 1998, edited by Christian Coddet. ASM International, 1998. http://dx.doi.org/10.31399/asm.cp.itsc1998p1523.
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Abstract Suspensions of cobalt spinel (Co3O4) powders (median size 6 µm and 0.3 µm) were r.f. plasma sprayed to form electrocatalytically active anode layers for alkaline water electrolysis. Stable cobalt oxide suspensions of low viscosity and exceeding 50wt.% solid phase content have been processed. A spheroidization study revealed the formation of large spherical powder particles (- 30 + 80 µm). Cobalt oxide coatings were produced by this novel r.f.-Suspension Plasma Spraying (SPS) method. The porosity was controlled by optimizing the spray distance and the reactor pressure. The main disadvantage of the thermal plasma processing of cobalt spinel, i.e. the decomposition of the spinel phase into CoO, could not be prevented, not even with the application of an 80% oxygen plasma. With a relatively low power oxygen plasma post-treatment the deposited CoO layers can be oxidized to Co3O4 resulting in a promising improvement of the electrochemical performance of the anode layers.
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Agrafiotis, Christos, Martin Roeb, and Christian Sattler. "Cobalt Oxide-Based Structured Thermochemical Reactors/Heat Exchangers for Solar Thermal Energy Storage in Concentrated Solar Power Plants." In ASME 2014 8th International Conference on Energy Sustainability collocated with the ASME 2014 12th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/es2014-6336.
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Based on the characteristics of the oxide redox pair system Co3O4/CoO as a thermochemical heat storage medium and the advantages of porous ceramic structures like honeycombs and foams in heat exchange applications, the idea of employing such ceramic structures coated with or manufactured entirely from a redox material like Co3O4, has been implemented. Thermo-Gravimetric Analysis (TGA) experiments have demonstrated that laboratory-scale Co3O4-coated, redox-inert ceramic foams and honeycombs exhibited repeatable, cyclic reduction-oxidation operation within the temperature range 800–1000°C, employing all the redox material incorporated, even at loading levels exceeding 100 wt% loading percentages. To further improve the volumetric heat storage capacity, monolithic porous ceramic foams made entirely of Co3O4 were manufactured, together with analogous pellets. Such porous structures were also capable of cyclic reduction–oxidation, exploiting the entire amount of Co3O4 used in their manufacture. In this perspective, “open” porous structures like the ones of ceramic foams seem to have significant advantages in addressing problems associated with cyclic expansion-contraction that could be detrimental to structural integrity.
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Vahedi, Nasser, and Alparslan Oztekin. "Experimental Analysis of Kinetics and Cyclic Performance of Cobalt Oxide Powder As Redox Reactant Agent for High-Temperature Thermochemical Energy Storage." In ASME 2019 Heat Transfer Summer Conference collocated with the ASME 2019 13th International Conference on Energy Sustainability. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ht2019-3681.
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Abstract For continuous operation of Concentrated Solar Power (CSP) Plants it is necessary to integrate thermal energy storage module. High-density energy storage system at a high temperature is required for the new generation of large scale CSP plants. The Thermochemical Energy Storage (TCES) systems use the enthalpy of formation of a reversible chemical reaction for energy storage and release. Gas/solid reduction-oxidation (redox) reactions of solid metal oxides using air as heat transfer fluid (HTF) can be directly integrated with air operated CSP plants, and there is no need for HTF storage and any intermediate heat exchanger. A new generation of large scale CSP plants uses high-temperature solar collectors to increase power cycle efficiency. Such operating conditions require the development of suitable high-temperature TCES systems. The selection of suitable metal oxide reactant is very critical in the design of such high-temperature storage systems and requires a detailed study of the physics of reaction within the reactor. Cobalt oxide (Co3O4/CoO) has been verified to have a high reaction temperature, high enthalpy of reaction together with reasonable cyclic and thermal stability. Unique features of cobalt oxide require more fundamental study of the physics behind the redox reaction and its cyclic performance. Study of the physics of materials during the storage/release cycle is necessary for the design and improvement of the reactor and can be used as a benchmark for comparison of any implemented changes. A high precision, true differential TGA/DSC instrument is used for simultaneous measurement of weightchange (TGA) and true differential heat flow (DSC) for pure cobalt oxide (Co3O4) powder. Storage cycle (charge/discharge) was conducted for five cycles. Complete re-oxidation was achieved within reasonable times by performing the two reactions at close temperatures and controlling heating/cooling rates. Basic performance parameters were derived as a benchmark for future references. Single-cycle controlling parameters such as heating/cooling rate, dwelling time, and purge gas rate were investigated. System response for few initial cycles was studied. It was shown that pure cobalt oxide could regain weight and complete re-oxidation with reasonable stability. A transition for heat flow was detected after a few initial cycles which reduced discharge heat and decreased overall performance.
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Schiller, G., M. Müller, F. Gitzhofer, M. I. Boulos, and R. B. Heimann. "Suspension Plasma Spraying (SPS) of Cobalt Spinel." In ITSC 1997, edited by C. C. Berndt. ASM International, 1997. http://dx.doi.org/10.31399/asm.cp.itsc1997p0343.
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Abstract Fine (median size 6 μm and 0.3 μm) cobalt spinel (Co3O4) powders were processed suspended in a suitable liquid phase. Suspensions exceeding 50 wt.% solid phase content were successfully injected into an inductively coupled plasma. Spheroidized powders with large particle size (up to 80 μm) were prepared, and cobalt oxide coatings were produced by this novel RF-SPS method. The microstructural features of the coatings can be controlled by parameter optimization similarly to plasma spraying of dry powders. Numerous variations of the physical and chemical conditions of the process were performed in an attempt to overcome the main disadvantage of the process, i.e. the decomposition of the spinel phase to CoO. So far, the spinel phase could be reestablished only by a post-treatment of the deposited coatings with atomic oxygen in the RF plasma.
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Vahedi, Nasser, Qasim A. Ranjha, and Alparslan Oztekin. "Numerical Study of High Temperature Thermochemical Energy Storage Using Co3O4/CoO." In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-86329.
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Large-scale solar power generation becomes feasible using concentrated solar power plants, as the received heat is collected at high temperatures compatible with power cycle operations. The main drawback of solar power generation is the intermittent nature of available solar irradiation, which results in a mismatch between collected heat and electrical demand. Thermal energy storage (TES) systems are the options to resolve this problem by storing excess heat during high solar irradiance and releasing at off-sun conditions. Thermochemical energy storage (TCES) systems have the potential to store the solar energy at high temperatures suitable for CSP plants’ operations because of the higher energy density of the TCES materials than those used for sensible and latent heat storage options. In TCES, the heat is stored in the form of thermo-chemical energy using an endothermic reaction and is released by carrying out the reverse exothermic reaction. TCES using cobalt oxide redox (reduction/oxidation) reaction is selected for this study because of its unique features suitable for high temperature thermal energy storage. A reactor with the cylindrical fixed bed is considered, in which air flows through the bed during charging and discharging modes. Air is used as heat transfer fluid (HTF) and as the reactant gas supplying oxygen. Transient mass and energy transport equations are solved along with reaction kinetics equations using finite element method. Charging and discharging processes are investigated. The effect of geometrical and operational parameters including the material properties on overall storage and retrieval process has been studied. It was shown that the bed porosity plays a dominant role in the reactor performance. The increase in the bed porosity improves the reactor performance for both charging and discharging mode.