Relevant bibliographies by topics / Cobalt – Minerais – Ferrites de cobalt

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Academic literature on the topic 'Cobalt – Minerais – Ferrites de cobalt'

Author: Grafiati
Published: 25 May 2024

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Journal articles on the topic "Cobalt – Minerais – Ferrites de cobalt"

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Lazdovica, Kristīne, and Valdis Kampars. "Influence of Crystallite Size of Nickel and Cobalt Ferrites on the Catalytic Pyrolysis of Buckwheat Straw by Using TGA-FTIR Method." Key Engineering Materials 903 (November 10, 2021): 69–74. http://dx.doi.org/10.4028/www.scientific.net/kem.903.69.

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Pyrolysis of buckwheat straw with or without catalysts was investigated using the TGA-FTIR method to determine the influence of nickel and cobalt ferrites on the distribution of pyrolysis products. According to the obtained results, the overall shape of the thermogravimetric and derivative thermogravimetric curves is unchanged in the presence of nickel and cobalt ferrites but different weight losses were observed. All catalysts contribute to the formation of solid residue from BWS pyrolysis. The presence of cobalt ferrites exhibited the highest bio-oil yields, whereas the highest non-condensable gas yield and the lowest bio-oil yield was obtained with the addition of NiFe2O4 (1) catalyst. According to the obtained results, the ability of nickel and cobalt ferrites to catalyze deoxygenation reactions depends on the crystallite size. The nickel or cobalt ferrites with smaller crystallite size (15-22 nm) show a higher ability to catalyzed dehydration reaction than catalysts with larger crystallite size (45-54 nm).
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Assem, E. E., A. M. Abden, and O. M. Hemada. "Thermal Properties of Cobalt Cadmium Ferrites." Key Engineering Materials 224-226 (June 2002): 831–34. http://dx.doi.org/10.4028/www.scientific.net/kem.224-226.831.

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Kale, G. M., and T. Asokan. "Electrical properties of cobalt‐zinc ferrites." Applied Physics Letters 62, no. 19 (1993): 2324–25. http://dx.doi.org/10.1063/1.109405.

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Lenglet, M., F. Hochu, and J. Dürr. "Optical Properties of Mixed Cobalt Ferrites." Le Journal de Physique IV 07, no. C1 (1997): C1–259—C1–260. http://dx.doi.org/10.1051/jp4:19971100.

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Caltun, Ovidiu, Ioan Dumitru, Marcel Feder, Nicoleta Lupu, and Horia Chiriac. "Substituted cobalt ferrites for sensors applications." Journal of Magnetism and Magnetic Materials 320, no. 20 (2008): e869-e873. http://dx.doi.org/10.1016/j.jmmm.2008.04.067.

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Martin Cabañas, B., S. Leclercq, P. Barboux, M. Fédoroff, and G. Lefèvre. "Sorption of nickel and cobalt ions onto cobalt and nickel ferrites." Journal of Colloid and Interface Science 360, no. 2 (2011): 695–700. http://dx.doi.org/10.1016/j.jcis.2011.04.082.

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Gupta, Priyanka, and Dr Ravi Kumar Vijai. "Synthesis, Characterization and Dielectric properties of Nanoparticles of Cobalt Doped Ferrite (Cox Fe1-x Fe2 O4)." International Journal of Chemistry, Mathematics and Physics 7, no. 4 (2023): 1–8. http://dx.doi.org/10.22161/ijcmp.7.4.1.

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Ferrites, a recently uncovered category of materials, have found extensive application in various critical domains. Among them, cobalt ferrites stand out as hard magnetic materials with exceptional coercivity.. We successfully prepared cobalt ferrites by using nanocrystalline powers by Sol gel method. In our study Crystalline, Magnetic nanoparticles of Cobalt ferrites (Cox Fe1-x Fe2 O4) (x = 0.4, 0.5, 0.6, 0.8) were synthesized by Sol Gel Method using ferric chloride and cobalt nitrate with NaOH as a reactant. Structural characteristics of samples were determined by X-Ray diffraction and TEM. Particle size found between 8.8 nm to 14.26 nm using Debye Scherrer method. Lattice constant decreases as the value of ‘x’ increases. Dielectric properties were investigated using impedance analyser. The relative dielectric constant and loss tangents of ferrites a function of frequency (1kHz-30MHz) was investigated at room temperature, both parameter decreases as frequency increases.
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de la Torre, Ernesto, Ana Lozada, Maricarmen Adatty, and Sebastián Gámez. "Activated Carbon-Spinels Composites for Waste Water Treatment." Metals 8, no. 12 (2018): 1070. http://dx.doi.org/10.3390/met8121070.

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Nowadays, mining effluents have several contaminants that produce great damage to the environment, cyanide chief among them. Ferrites synthesized from transition metals have oxidative properties that can be used for cyanide oxidation due to their low solubility. In this study, cobalt and copper ferrites were synthesized via the precipitation method, using cobalt nitrate, copper nitrate, and iron nitrate as precursors in a molar ratio of Co or Cu:Fe = 1:2 and NaOH as the precipitating agent. The synthesized ferrites were impregnated in specific areas on active carbon. These composites were characterized using X-Ray Diffraction (XRD) and Scanning Electron Spectroscopy (SEM). The XRD results revealed a cubic spinel structure of ferrites with a single phase of cobalt ferrite and two phases (copper ferrite and copper oxides) for copper. The CoFe2O4 impregnated on active carbon reached a cyanide oxidation of 98% after 8 h of agitation; the composite could be recycled five times with an 18% decrease in the catalytic activity. In cobalt ferrites, a greater dissolution of iron than cobalt was obtained. In the case of copper ferrite, however, the copper dissolution was higher. These results confirm that ferrites and activated carbon composites are a novel alternative for cyanide treatment in mining effluents.
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Boss, Alan F. N., Antonio C. C. Migliano, and Ingrid Wilke. "The Influence of Stoichiometry on the Index of Refraction of Cobalt Ferrite Samples at Terahertz Frequencies." MRS Advances 2, no. 58-59 (2017): 3663–66. http://dx.doi.org/10.1557/adv.2017.355.

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ABSTRACT We report an experimental study on the terahertz frequency dielectric properties of manganese cobalt ferrites (MnxCo1−xFe2O4) and nickel cobalt ferrites (NixCo1-xFe2O4) with three different stoichiometry each, x=0.3, x=0.5 and 0.7. Particularly, we present a comparison and discussion of the terahertz frequency indices of refraction of these two ferrites compositions. MnxCo1−xFe2O4 and NixCo1-xFe2O4 pellets with different Mn/Co and Ni/Co ratios (x=0.3, x=0.5 and x=0.7) were prepared by state-of-the-art ceramic processing. The morphology and chemical homogeneity of these ferrites were characterized by energy dispersive x-ray spectroscopy. We observed that the indexes of refraction for manganese cobalt ferrites are 3.22, 3.71 and 3.67 for ratios of 0.3, 0.5 and 0.7, respectively. In the case of nickel cobalt ferrite, the indexes of refraction are 3.53, 3.57 and 3.47 for ratios of 0.3, 0.5 and 0.7 respectively. We notice a substantial difference in the index of refraction for the Mn0.3Co0.7Fe2O4. This difference may be correlated to a secondary phase formed in this sample.
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Bushkova, V. S., I. P. Yaremiy, B. K. Ostafiychuk, V. V. Moklyak, and A. B. Hrubiak. "Mössbauer Study of Nickel-Substituted Cobalt Ferrites." Journal of Nano- and Electronic Physics 10, no. 3 (2018): 03013–1. http://dx.doi.org/10.21272/jnep.10(3).03013.

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Dissertations / Theses on the topic "Cobalt – Minerais – Ferrites de cobalt"

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Ajroudi, LIlia. "Ferrites de cobalt nanostructurés ; élaboration, caractérisation, propriétés catalytiques, électriques et magnétiques." Thesis, Toulon, 2011. http://www.theses.fr/2011TOUL0017/document.

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Ce travail est consacré à l’élaboration et l’étude des propriétés catalytiques, électriques et magnétiques denanomatériaux à base de ferrite de cobalt. Les nanopoudres de ferrite de cobalt (CoxFe3-xO4 , x=0.6,1,1.2,1.8 ) ont étéélaborées par une nouvelle méthode chimique solvo-thermale. Les nanopoudres obtenues sont très bien cristallisées ontdes tailles de particules qui varient avec le taux de cobalt entre 4 et 7 nm et sont très homogènes en composition. Lesnanopoudres de ferrites de cobalt sont monophasées, de structure spinelle avec un paramètre de maille qui varie enfonction du taux de cobalt. Les nanopoudres de ferrites de cobalt ne s’oxydent pas sous air et en température .Lesnanopoudres de composition proches de x=1 sont stables jusqu’à 900°C, alors que pour de plus forts écarts à lastoechiométrie, des transformations de phase ont lieu au delà de 550°C.Les mesures catalytiques ont mis en évidence l’oxydation de CH4 en CO2 après passage sur le catalyseur pour tous leséchantillons. L’efficacité catalytique est maximale et l’énergie d’activation est la plus faible pour l’échantillon x=1.8 ;ceci est lié à la plus grande surface spécifique, et au plus fort taux de sites actifs pour cette composition.Les ferrites de cobalt élaborées présentent une conduction de type électronique avec un comportement semi conducteurjusqu’à 500-600°C et un comportement métallique au-delà. Les variations de conductivité d’une composition à l’autres’expliquent par les variations du nombre de paires [Co2+,Fe3+].Les nanoparticules ont un comportement superparamagnétique quelle que soit la composition. Ce comportement estdû principalement à un effet de taille et de forme, et à une distribution cationique différente entre les deux types desites tétraédriques et octaédriques de la structure spinelle. Ces ferrites présentent une aimantation à saturation prochede celle de l’état massif, du fait de la grande qualité cristalline attribuée à la méthode d’élaboration mise au point<br>This work is devoted to the synthesis and the study of the physical properties of cobalt ferrite nanomaterials. Thecobalt ferrite nanopowders (CoxFe3-xO4 , x=0.6,1,1.2,1.8 ) were synthesized by a new solvo thermal chemical route.The nanopowders are highly crystallized, very homogeneous in size and chemical composition. The nanopowderssizes are ranged from 4 nm for high cobalt content to 7 nm for low cobalt content. They are single phased, with thespinel structure, and a cell parameter varying with the cobalt content. The cobalt ferrites do not oxidize, when heatedunder air. For compositions near x=1, the cobalt ferrites are stable when heated under air up to 900°C, as for the othercompositions, phase transformations occur above 550°C.The catalytic measurements have shown the oxidation of CH4 into CO2 in presence of the catalyst for all thecompositions. Cobalt ferrite with composition x=1.8, presents the lowest activation energy and the best catalyticefficiency; this can be related to the great specific surface and the high rate of active sites for this composition.Concerning the conduction properties, the cobalt ferrites exhibit a semiconductor character up to 500-600 ° C and ametallic one above. Changes in conductivity from a composition to another are explained by changes in the number ofpairs [Co2+, Fe3+].A superparamagnetic behaviour was evidenced whatever the composition. This is due for one part to a size and shapeeffect and for the other part to different cationic distribution between tetrahedral and octahedral sites. These ferriteshave a saturation magnetization close to that of the massive state, because of the high crystallinity of the nanopowders,attributed to the synthesis method developed in this work
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Fernandes, de Medeiros Indira Aritana. "Nanostructuration de ferrites de cobalt CoxFe3-xO4 : Effets sur la catalyse et la détection de gaz polluants." Thesis, Toulon, 2018. http://www.theses.fr/2018TOUL0007/document.

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Différentes méthodes de synthèses ont été mises au point pour contrôler la forme et la composition des nanoparticules. L’effet de la nature et la concentration des surfactants, des solvants, la température et le temps de synthèse a également été étudié. Les poudres ont été caractérisées par diffraction des rayons X et microscopie électronique à transmission, couplée à la spectroscopie d'énergie dispersive. Des propriétés catalytiques et de détection ont été évaluées respectivement en présence de faibles concentrations de CO et de NO2 dans de l’air synthétique.Des nanooctaèdres de CoxFe3-xO4 ( x=1, 1,5 et x = 1,8 ) de 15-20 nm ont été produits par synthèse hydrothermale en utilisant différents surfactants (CTAB, SDS et PVP). Des nanocubes de tailles différentes de CoFe2O4 ont été produits par synthèse solvothermique en utilisant l'oléylamine comme surfactant. La poudre de CoxFe3-xO4 avec x = 1,5 a une activité plus élevée pour la conversion du CO que les nanooctaèdres x=1, et la conversion a lieu à plus basse température dans le cas des nanocubes. Les nanocubes présentent une sensibilité inférieure de détection au NO2 à celle des nanooctaèdres, ce qui indique que les faces {111} sont plus réactives que les faces {100} dans les nanoparticules de ferrites de cobalt<br>Different synthesis methods such as hydrothermal, solvothermal and thermal decomposition were developed to control nanoparticles shape and composition. The influence of synthesis parameters such as the nature of surfactants, the solvents, temperature and time of synthesis were also investigated. The powders were characterized by X-ray Diffraction and Transmission Electron Microscopy coupled with Dispersive Energy Spectroscopy. The catalytic and detection properties were evaluated in presence of CO and NO2 in synthetic air. CoxFe3-xO4 (x = 1, 1.5 ) nanooctahedra with 15-20 nm were produced by hydrothermal synthesis using different surfactants (CTAB, SDS and PVP). Nanocubes of CoFe2O4 were successfully obtained by solvothermal synthesis using oleylamine as surfactant. Nanooctahedra of CoxFe3-xO4 with x = 1.5 have higher activity for the CO conversion than those with x=1, and the conversion starts at lower temperature for the nanocubes. The nanocubes show lower sensitivity for the detection of NO2 than the nanooctahedra which indicates that the {111} faces are more reactive than the {100} ones in cobalt ferrites nanoparticles
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Mahhouti, Zakaria. "Synthesis and characterization of functional monodispersed cobalt ferrite nanoparticles." Electronic Thesis or Diss., Amiens, 2019. http://www.theses.fr/2019AMIE0010.

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Dans le présent travail, les nanoparticules monodispersées à base de ferrite de cobalt ont été explorées pour leurs propriétés magnétiques et leur effet magnétostrictif, ainsi que pour une utilisation en tant que ferrofluide. Les nanoparticules ont été dispersées avec succès dans un solvant organique. La chimie de surface de la nanoparticule magnétique s'avère cruciale pour obtenir une dispersion haute densité homogène et bien séparée dans l'hexane. De plus, l'acide oléique a été utilisé pour modifier la surface des nanoparticules de ferrite de cobalt et permettre d'obtenir une bonne dispersion. Les nanoparticules obtenues sont caractérisées par XRD, spectroscopie Raman, TGA, FT-IR, DLS, SEM et la caractérisation magnétique. En utilisant l'analyse STEM, nous avons constaté que la taille et la forme des nanoparticules pouvaient être contrôlées en faisant varier certains paramètres tels que la température de synthèse, la quantité et la nature des réactifs. En outre, des membranes anodiques poreuses à pores très ordonnés ont été fabriquées avec succès avec une anodisation en plusieurs étapes. Des nanorods de ferrite de cobalt ont été produites par la transformation des nanoparticules de CoFe2O4 à l'aide d'une membrane d’alumine poreuses. L'insertion des nanoparticules de CoF2O4 dans les pores des membranes a été étudiée par le microscope électronique à balayage, et il a été possible de suivre le comportement des nanoparticules de CoFe2O4 dans les pores lors de l'insertion ainsi que lors de la transformation<br>In the present work, monodisperse cobalt ferrite nanoparticle systems have been explored in regard to their magnetic properties and magnetostrictive effect, as well as for use as a ferrofluid. Nanoparticles have been successfully dispersed in an organic solvent. The surface chemistry of the magnetic nanoparticle proves critical to obtaining a homogeneous and well separated high density dispersion in Hexane. In addition, Oleic acid was used to alter the surface of cobalt ferrite nanoparticles and successfully achieve good dispersion. The obtained nanoparticles are characterized using XRD, Raman spectroscopy, TGA, FT-IR, DLS, SEM, and magnetic investigations. Using STEM analysis, we found that the size and shape of nanoparticles could be controlled by varying certain parameters such as the synthesis temperature, the quantity, and nature of reagents. Furthermore, porous anodic membranes with highly ordered pores were successfully fabricated with multi-steps anodizing. Cobalt ferrite nanorods were produced by a transformation of CoFe2O4 nanoparticles using anodic alumina membrane. The insertion of CoF2O4 nanoparticles into the pores of the AAO membranes was studied with a scanning electron microscope, and it was possible to follow the behavior of CoFe2O4 nanoparticles in the pores during the insertion step as well as the transformation step
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Ourry, Laurence. "Relation structure-propriétés de matériaux hybrides magnétiques polymère-ferrites spinelles." Paris 7, 2014. http://www.theses.fr/2014PA077193.

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J'ai travaillé à la conception de matériaux hybrides magnétiques constitués de polymère et de nanoparticules d'oxydes métalliques de type spinelles en me concentrant sur (i) ta synthèse de nanopoudres d'oxydes magnétiques par le procédé polyol et le contrôle de leurs propriétés magnétiques (modulation de la taille des NPs, recours à l'échange-bias pour augmenter la stabilité thermique magnétique. . . ), (ii) le contrôle de la dispersion des NPs par la connaissance de leur état de surface et des procédés de fonctionnalisation judicieux et (iii) leur mise en forme au sein de matrices de polymères thermoplastiques ou de biopolymères préformés, Ces différents points sont discutés à travers trois thèmes : (a) La synthèse de nanoparticules coeur-coquille Fe304@CoO présentant un phénomène d'échange blas, qui ont ensuite été fonctionnalisées par des brosses de polystyrène (PS) et de polyméthacrylate de méthyle (PMMA nous avons comparé les propriétés magnétiques (interactions dipolaires et échange bias) de ces hybrides à celles des nanoparticules nues. (b) La synthèse de nanoparticules de ferrite de cobalt, CoFe204, et leur fonctionnalisation de surface par deux ligands. Ces nanoparticules ont ensuite été introduites dans une matrice de polyfluorure de vinylidène (PVDF) afin de réaliser des films rnagnétoélectriqUes. (c) La conception de gels et de films magnétothermosensibles pour la délivrance médicamenteuse ou l'ingénierie tissulaire. Ce projet est une étude exploratoire à un projet développé par IBM, Centre d'Almaden, USA, où j'ai réalisé un stage de 3 mois au cours de ma thèse<br>I worked on the design of magnetic hybrid materiais consisting of polyrner and spinel metal oxide nanoparticles focusing on (1) the synthesis of nanopowders of magnetic oxides by the polyol process and controlling the magnetic properties (timing of the size of NPs, use of exchange-bias to increase the magnetic thermal stability. . . ), (ii) the control of the dispersion of NPs as a function of their surface state and suitable functionalizations and ( iii) their processing in thermbplastic polymer matrices or preformed biopolymers. These points are discussed through three topics: (a) the synthesis of Fe304@CoO core-shell nanoparticles exhibiting exchange bias, and their further functionalization by polystyrene (PS) and polymethylmethacrylate (PMMA) brushes", we compared the magnetic properties (dipolar interactions and exchange bias) of these hybrids with those of bare nanoparticles. (b) The ynthesis of cobalt ferrite nanoparticles, CoFe204, and surface functionalization with two ligands. These nanoparticles were then introduced into a polyvinylidene fluoride matrix (PVDF) to design magnetoelectric films. (c) The design of magnetothermosensitives gels and films for drug delivery and tissue engineering. This project is an expioratory study to a project developed by IBM, Almaden Center, USA, where I reallzed a 3 month internship dunng my PhD involvement
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Song, Sang-Hoon. "Magnetic and magnetoelastic properties of M-substituted cobalt ferrites (M=Mn, Cr, Ga, Ge)." [Ames, Iowa : Iowa State University], 2007.

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Villette, Carole. "Elaboration et caractérisation de fines particules de ferrites spinelles substitués (cuivre/cobalt/manganèse) : relations structure-propriétés magnétiques." Toulouse 3, 1995. http://www.theses.fr/1995TOU30286.

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Les conditions d'elaboration a basses temperatures de particules aciculaires de differents ferrites substitues au cuivre ont ete determinees en vue de l'etude de leurs proprietes physico-chimiques. La caracterisation structurale des ferrites peu riches en cuivre a permis de reveler les valences mixtes du cuivre et du fer. Dans ces phases stoechiometriques les ions cuivreux et ferriques sont localises en sites tetraedriques et octaedriques et les ions cuivriques et ferreux uniquement en sites octaedriques. Compte tenu des basses temperatures utilisees pour leur elaboration ces ferrites possedent une reactivite vis-a-vis de l'oxygene suffisante pour faire apparaitre des phases lacunaires. L'oxydation des ions cuivreux a ete mise en evidence de maniere originale puisque le ferrite stoechiometrique riche en cuivre (21% massique) de symetrie cubique possede apres oxydation une maille quadratique. Le ferrite cuivrique (26,5% massique) possede lorsqu'il est refroidi lentement a partir de sa temperature de preparation une symetrie quadratique. Pour cette composition, l'association de l'anisotropie de structure (deformation de la maille) et de l'anisotropie de forme due a l'acicularite des particules permet d'atteindre des champs coercitifs de l'ordre de 1600 oe. Par ailleurs, si l'on substitue les ions cobalt (cations a forte anisotropie magnetocristalline) aux ions cuivre le champ coercitif de ces ferrites atteint une valeur de 4000 oe environ pour une teneur massique relativement faible de 3,7%. L'incidence de la deformation de la maille spinelle sur le champ coercitif a egalement ete observee pour le ferrite substitue au manganese (un manganese pour deux fer). En effet, a l'etat stoechiometrique le ferrite possede une symetrie cubique, mais au terme d'un traitement d'oxydation faisant apparaitre une quantite importante d'ions manganese trivalents la maille cristalline devient quadratique. Cette evolution structurale et chimique se traduit par un tres fort accroissement du champ coercitif qui passe de 180 oe pour le ferrite stoechiometrique a 500 oe apres oxydation
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Artus, Mathieu. "Synthèse en milieu polyol et caractérisation de nanoparticules de ferrite de cobalt à forte anisotropie magnétique." Paris 7, 2008. http://www.theses.fr/2008PA077244.

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Ce travail cherche à optimiser les propriétés magnétiques de nanoparticules pour des applications dans le domaine du stockage de l'information. La méthodologie de synthèse est basée sur le procédé polyol. Après un résumé sur le magnétisme dans les nanoparticules et une présentation de la méthode polyol, la première partie de ce travail porte sur la synthèse de nanoparticules de ferrite-dé cobalt simple. Les particules synthétisées sont caractérisées sur le plan structural par diffraction des rayons X, MET, XANES et Mössbauer. Les propriétés magnétiques ont été également étudiées, notamment l'influence de la taille sur la température de blocage. Ensuite, pour améliorer la valeur de la température de blocage, des nanoparticules de CoFe₂O₄ dopées aux terres rares à hauteur de 10% ont été préparée. Malheureusement, les propriétés magnétiques, et notamment la température de blocage, ne sont pas celles attendues. Une analyse de la structure locale par spectroscopie XANES, révèle un changement dans la structure locale de la maille spinelle avec une migration des ions Co²⁺ des sites tétraédriques vers les sites octaédriques, provocant la chute de l'anisotropie magnétocristalline. Le dernier chapitre traite de la synthèse de nanoparticules de type cœur/coquille présentant une interaction d'échange. Des particules composites, CoFe₂O₄ /NiO et CoFe₂O₄ /NiO ont été obtenue avec succès. De plus on constate une augmentation de la température de blocage, jusqu'à 100 K, sur les échantillons étudier. Il reste cependant à optimiser le protocole de synthèse et à procéder à des caractérisations supplémentaires pour obtenir de plus ample information sur la structure de ces matériaux<br>This work deals about the enhancement of the magnetic properties of nanoparticles for magnetic data storage. The main synthesis method used, is the forced hydrolysis in polyol medium. After a short description of the magnetism in the nanoparticles and a presentation of synthesis method, the first of the present work concern the size control of the nanoparticles and is influence on the magnetic properties. The obtain product were characterized by différent technique such as the XRD, TEM, XANES, SQUID and Mössbauer. It reveals that, if a continuous variation of the blocking temperature was observed, the local structure of the particles is affected by the size reduction. After, the nanoparticles were doped with rare earth at 10%, in order to increase the value of TB. Various techniques were used to characterize the particles and the chemical composition is closed from the expected one, but the introduction caused a fall of the blocking temperature. This behavior is a consequence of a change in the cationic distribution, the departure of the Co²⁺ ion from the octahedral site to the tetrahedral one cause a loss of magnetic anisotropy. In the last chapter, the synthesis and the characterization of core/shell nanoparticles is describe. The existence of a exchange bias between the ferromagnetic core and the antiferromagnetic shell gave a rise of the blocking temperature, until 100 K for the CoFe₂O₄/CoO one. But synthesis improvement and a deeper investigation of the particles structure is require for this part
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Moyeux, Alban. "Nouvelles réactions de couplage catalysées par des sels de fer ou de cobalt." Cergy-Pontoise, 2008. http://www.theses.fr/2008CERG0484.

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L’utilisation de sels de fer ou de cobalt pour catalyser des réactions de couplage présente de nombreux avantages à la fois au niveau économique et écologique. Au cours de ce travail, nous avons développé plusieurs méthodes de couplage catalysées par ces métaux de transition : le couplage entre des halogénures d’alkyle et des composés organomagnésiens aromatiques ou vinyliques en présence de sels de fer, le couplage entre des halogénures d’alkyle et des composés organomagnésiens aromatiques ou aliphatiques en présence de sels de cobalt, enfin, la réaction d’hétérocouplage oxydatif entre un composé diorganozincique aliphatique et un composé diorganozincique aromatique en présence de sels de fer<br>Sustainable development now plays an increasingly important role in the strategy of chemical industries. As a part of these preoccupations, the search for more economic and more eco-friendly new efficient synthetic methods is of vital concern. The development of iron- and cobalt-catalyzed cross-coupling reactions is one of the current promising fields of research since these reactions are very attractive compared to the related palladium- or nickel-catalyzed procedures extensively used until now. Several new coupling procedures were described in this thesis. - The iron-catalyzed reaction between aryl Grignard reagents and alkyl halides. - The cobalt-catalyzed reaction between aryl or alkyl Grignard reagents and alkyl halides. - The iron-catalyzed oxidative heterocoupling between dialkylzinc and diarylzinc compounds The last reaction paves the way to a new class of coupling reactions between two organometallics
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DOUARD, SYLVIE. "Nouveaux catalyseurs a base de ferrites spinelles substitues (molybdene/cobalt) et de molybdates pour l'oxydation menagee du propylene." Toulouse 3, 1998. http://www.theses.fr/1998TOU30022.

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Des ferrites spinelles de molybdene et de cobalt mo#xco#yfe#3#-#x#-#yo#4 ont ete synthetises par chimie douce a partir de precurseurs hydroxydes. Les nouvelles phases obtenues recouvrent un domaine de composition assez large : x 0,5 et 0 y 1 et presentent une surface specifique de l'ordre de 20 m#2/g. L'etude de leur processus d'oxydo-reduction par thermogravimetrie differentielle a permis d'etablir leur repartition cationique. Les ions molybdene situes majoritairement en sites octaedriques presentent les etats de valence +iii et +iv. Outre les ions co#2#+, la presence en sites octaedriques d'ions co#3#+ a ete mise en evidence et leur reduction a l'air en ions co#2#+ a ete observee vers 500c. Divers molybdates ont ete egalement synthetises par chimie douce : fe#2mo#3o#1#2 de structure grenat, comoo#4 constitue majoritairement de la variete allotropique dont la structure est derivee de la wolframite, bi#2mo#3o#1#2 de structure scheelite et bi#2mo#2o#9. La maitrise des conditions de synthese (ph, temperature, concentration) est capitale pour l'obtention de phases pures. Les molybdates de fer et de cobalt peuvent presenter une surface specifique variable autour de 10-20 m#2/g alors que les molybdates de bismuth se caracterisent par une tres faible surface comprise entre 1 et 5 m#2/g. Le test catalytique d'oxydation du propylene montre que les ferrites et le molybdate fe#2mo#3o#1#2 convertissent le propylene des 280-300c en co#x alors que la phase comoo#4 est tres peu reactive. Les molybdates de bismuth necessitent des temperatures superieures a 340c, mais apparaissent tres selectifs en acroleine et acide acrylique. Le melange binaire mo#xco#yfe#3#-#x#-#yo#4 + bi#2mo#3o#1#2 permet d'ameliorer les performances catalytiques, et certaines de ses caracteristiques tels la composition, la surface specifique et l'etat d'oxydation du ferrite ont ete optimisees. La selectivite en acroleine et acide acrylique, associee a un taux de conversion de 96%, peut ainsi atteindre 70% a 350c.
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Valetas, Matthieu. "Couches minces magnétiques pour applications hyperfréquences : étude des Samarium-Cobalt et des Néodyme-Fer-Bore par pulvérisation radiofréquence magnétron." Limoges, 2003. http://aurore.unilim.fr/theses/nxfile/default/e4a981a5-04cb-45b7-a3d1-c4d68512c71c/blobholder:0/2003LIMO0044.pdf.

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Les dispositifs micro-ondes non réciproques à ferrite, comme les circulateurs, sont actuellement très utilisés dans les télécommunications sous forme massive. Ils nécessitent, pour fonctionner, d'être polarisés par un champ magnétique, qui peut être créé par un aimant permanent. L'enjeu actuel est d'intégrer ces circulateurs, sous forme de multicouche, sur un même substrat (technologies MMIC). Une autre application possible de ces dispositifs intégrés à ferrite sont les antennes à polarisation circulaire. Une simulation de leur comportement à 40 GHz est notamment présentée dans ce mémoire. La suite de ce travail traite de la réalisation par pulvérisation radiofréquence magnétron et de la caractérisation de couches magnétiques de Samarium-Cobalt et de Néodyme-Fer-Bore ; elles sont susceptibles de polariser magnétiquement une couche de ferrite doux. Pour ce faire, l'axe de facile aimantation des mailles doit être perpendiculaire au plan de la couche. Afin de favoriser cette orientation, un dispositif de dépôt sous induction magnétique a été conçu après simulation. Des possibilités d'épitaxie des dépôts sur les substrats ont également été envisagées afin de favoriser la croissance axe c. L'influence, sur la structure des couches, leurs propriétés magnétiques et leur composition, de nombreux paramètres expérimentaux a été étudiée. La phase magnétique Nd(2)Fe(14)B a ainsi pu être mise en évidence sous forme polycristalline. Des champs coercitifs de l'ordre de 0,6 Tesla ont pu être obtenus. L'intégration des circulateurs nécessitera, ensuite, d'orienter convenablement ces couches magnétiques dures
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Book chapters on the topic "Cobalt – Minerais – Ferrites de cobalt"

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Zhang, Xijun, Guoqian Wang, Xin Peng, et al. "Structural and Magnetic Properties of Rare Earth Lanthanum-Doped Cobalt Ferrites." In The Minerals, Metals & Materials Series. Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-92388-4_39.

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Caldeira, Luis Eduardo. "Synthesis, Properties, and Applications of Spinel Cobalt Ferrites." In Environmental Applications of Nanomaterials. Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-86822-2_1.

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Bhuvaneswari, M., and S. Sendhilnathan. "Preparation and Characterization of Cobalt Doped Mn-Zn Ferrites." In Lecture Notes in Mechanical Engineering. Springer India, 2012. http://dx.doi.org/10.1007/978-81-322-1007-8_55.

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Chandra, Kailash, Sonal Singhal, and Sandeep Goyal. "Magnetic and Mössbauer spectral studies of nano crystalline cobalt substituted magnesium ferrites (MgxCo1 − xFe2O4)." In ICAME 2007. Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-78697-9_28.

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Siyar, Muhammad, and Asghari Maqsood. "Development of Graphene Based Cobalt-Ferrites Nanocomposites for Microwave Shielding." In Ferrite [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.99849.

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The study is related to cobalt ferrites nanocomposites embedded with graphene nanosheets, prepared by co-precipitation method. Various doping of graphene from 0.1% up to 1% were applied within the cobalt ferrite structure to study its microwave and mechanical effects on the nanocomposites. Microstructural analysis confirms the homogeneous dispersion and successful adhesion of graphene nanosheets within the cobalt ferrite matrix. Microwave absorbing capacity of these samples was studied by Agilent network analyzer in low frequency band of microwave (1MHz to 2 GHz), Results reveals that graphene incorporation not only improved the absorption capacity of cobalt ferrites (13dB-17d), but also widened its maximum absorption peak. This change was supposed to be due to inhomogeneity and combine effects of electric (graphene), and magnetic dielectric nature (cobalt ferrites). Further mechanical characterizations reveal that our composites samples have higher flexural strength (19.92 MPa for 1% loading) and improved toughness (&gt;6000 J/mm2) compare to pure cobalt ferrites (10.28 MPa, 1000 J/mm2).
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Ziaul Ahsan, Md. "Comparison of Magnetic and Electrical Properties of Manganese-Doped Cobalt Ferrite Nanoparticles." In Applications of Ferrites [Working Title]. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.1001859.

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Cobalt ferrites have been regarded as one of the competitive candidates in diversified applications because of their tailored electrical and magnetic properties by tuning structural parameters with doping of transition and/or rare earth elements. To meet the ever-growing technological demands, varieties of new compositions of cobalt ferrites with diverse properties are continuously developed and produced through different synthetic routes across the globe and are made available to the consumers. In the recent past, three compositions of manganese-doped cobalt ferrite nanoparticles have been developed through a solid-state reaction route by using the planetary ball milling technique. In this chapter, a comparison on their novelty in respect of their magnetic and electrical properties is made to spot their possible applications. Besides, few suggestions have been put forwards for further investigations to meet the challenges in the days to come.
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Bokhan, Yuri. "Thermoelectric Elements with Negative Temperature Factor of Resistance." In Thermoelectricity [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.98860.

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The method of manufacturing of ceramic materials on the basis of ferrites of nickel and cobalt by synthesis and sintering in controllable regenerative atmosphere is presented. As the generator of regenerative atmosphere the method of conversion of carbonic gas is offered. Calculation of regenerative atmosphere for simultaneous sintering of ceramic ferrites of nickel and cobalt is carried out. It is offered, methods of the dilated nonequilibrium thermodynamics to view process of distribution of a charge and heat along a thermoelement branch. The model of a thermoelement taking into account various relaxation times of a charge and warmth is constructed.
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Corrêa, Iran Carlos Stalliviere, and Lauro Júlio Calliari. "Minerais Polimetálicos." In Recursos Minerais Marinhos. Sociedade Brasileira de Geofísica - SBGf, 2023. http://dx.doi.org/10.22564/sbgfbook.cad5.2023.cap12.

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A distribuição dos nódulos e das crostas polimetálicas ocorre sobre a maior parte do assoalho oceânico, em profundidades acima dos 4.000 m. Estes apresentam estratificações laminares, com espessuras que variam de milímetros a decímetros. Estima-se que estes depósitos de nódulos e crostas polimetálicas, cubram uma área de aproximadamente 6,4 x 106 km2. Estes nódulos polimetálicos, são concreções rochosas formadas por camadas concêntricas de hidróxidos de ferro e manganês os quais se desenvolvem a partir de um núcleo o qual pode ser um fragmento de rocha, restos de origem biogênica como dentes de tubarão ou carapaças de organismos como os radiolários e até mesmo fragmentos de antigos nódulos. Em sua composição química, os nódulos polimetálicos possuem metais estratégicos como níquel, cobalto e cobre, bem como a presença de terras raras, metais amplamente utilizados hoje em dia para o desenvolvimento tecnológico e econômico dos países industrializados. No presente estudo demonstra-se do desenvolvimento desde nódulos e o valor estratégico e econômico de sua exploração. Estes depósitos apresentam um valor econômico de importância mundial devido aos inúmeros elementos químicos que formam sua composição. Palavras-chave: nódulos polimetálicos, ocorrência de nódulos, formação de nódulos. Abstract The distribution of polymetallic nodules and crusts occurs over most of the ocean floor, at depths above 4,000 m. These have laminar stratifications, with thicknesses ranging from millimeters to decimeters. These deposits of polymetallic nodules and crusts are estimated to cover an area of approximately 6.4 x 106 km2. These polymetallic nodules are rocky concretions formed by concentric layers of iron and manganese hydroxides which develop from a core which can be a fragment of rock, remains of biogenic origin such as shark teeth or shells of organisms such as radiolaria and even fragments of old nodules. In their chemical composition, polymetallic nodules have strategic metals such as nickel, cobalt and copper, as well as the presence of rare earths, metals widely used today for technological and economic development in industrialized countries. This study demonstrates the development of nodes and the strategic and economic value of their exploration. These deposits have an economic value of world importance due to the numerous chemical elements that make up their composition. Keywords: polymetallic nodules, nodule occurrence, nodule formation.
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Souza, Kaiser Gonçalves. "Aspectos Legais dos Recursos Minerais da Área Internacional dos Oceanos." In Recursos Minerais Marinhos. Sociedade Brasileira de Geofísica - SBGf, 2023. http://dx.doi.org/10.22564/sbgfbook.cad5.2023.cap19.

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Este capítulo apresenta e discute os principais aspectos legais dos recursos minerais que podem ser encontrados em áreas situadas além de jurisdição nacional, a chamada “ÁREA”, e sobre os quais a Autoridade Internacional dos Fundos Marinhos (AUTORIDADE) elaborou regulamentação internacional para prospecção e exploração de nódulos polimetálicos, os sulfetos polimetálicos e as crostas ferromanganesíferas ricas em cobalto. Especificamente este capítulo apresenta as etapas necessárias para a realização de prospecção na ÁREA, seguida de pedidos de aprovação de planos de trabalho para exploração na forma de contratos e a elaboração de contratos de exploração mineral junto à AUTORIDADE. Os aspectos legais referentes a proteção e preservação do meio ambiente marinhos também são discutidos. O capítulo foi elaborado de forma a (a) servir como um guia para empresas públicas, empresas privadas e setores governamentais brasileiros com vistas ao desenvolvimento de atividades de exploração mineral na área internacional do Atlântico Sul; e (b) contribuir para a ampliação da presença brasileira no Atlântico Sul e Equatorial de forma racional e sustentável. Palavras-chave: recursos minerais, regulamentação, código mineral, área internacional dos oceanos. Abstract This chapter presents and discusses the main legal aspects of mineral resources that can be found in areas located beyond national jurisdiction, the so-called “AREA”, and upon which the International Seabed Authority (AUTHORITY) has developed international regulations for prospecting and exploration of polymetallic nodules, polymetallic sulfides and ferromanganese cobalt rich crusts. Specifically, this chapter presents the necessary steps for prospecting in the AREA, followed by requests for approval of plans of work for exploration in the form of contracts and the preparation of mineral exploration contracts with the AUTHORITY. The legal aspects related to the protection and preservation of the marine environment are also discussed. The chapter was designed to (a) serve as a guide for public companies, private companies and Brazilian government sectors with a view to developing mineral exploration activities in the international area of the South Atlantic Ocean; and (b) to contribute to the enlargement of the Brazilian presence in the South Atlantic and Equatorial in a rational and sustainable manner. Keywords: mineral resources, regulation, mining code, international area of the oceans.
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Cadar, Oana, Thomas Dippong, Marin Senila, and Erika-Andrea Levei. "Progress, Challenges and Opportunities in Divalent Transition Metal-Doped Cobalt Ferrites Nanoparticles Applications." In Advanced Functional Materials. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.93298.

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Engineered nanomaterials with tailored properties are highly required in a wide range of industrial fields. Consequently, the researches dedicated to the identification of new applications for existing materials and to the development of novel promising materials and cost effective, eco-friendly synthesis methods gained considerable attention in the last years. Cobalt ferrite is one of the nanomaterials with a wide application range due to its unique properties such as high electrical resistivity, negligible eddy current loss, moderate saturation magnetization, chemical and thermal stability, high Curie temperature and high mechanical hardness. Moreover, its structural, magnetic and electrical properties can be tailored by the selection of preparation route, chemical composition, dopant ions and thermal treatment. This chapter presents the recent applications of nanosized cobalt ferrites doped or co-doped with divalent transition ions such as Zn2+, Cu2+, Mn2+, Ni2+, Cd2+ obtained by various synthesis methods in ceramics, medicine, catalysis, electronics and communications.
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Conference papers on the topic "Cobalt – Minerais – Ferrites de cobalt"

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Pannaparayil, T., and S. Komarneni. "Synthesis and charcterization of ultrafine cobalt ferrites." In International Magnetics Conference. IEEE, 1989. http://dx.doi.org/10.1109/intmag.1989.690371.

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Rao, G. S. N., S. Ananda Kumar, K. H. Rao, et al. "Doped Cobalt Ferrites for Stress Sensor Applications." In 2007 2nd IEEE International Conference on Nano/Micro Engineered and Molecular Systems. IEEE, 2007. http://dx.doi.org/10.1109/nems.2007.352231.

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Sharma, Harish, Bharat Mishra, and P. K. Sharma. "X-ray diffraction analysis on copper-cobalt ferrites." In NATIONAL CONFERENCE ON PHYSICS AND CHEMISTRY OF MATERIALS: NCPCM2020. AIP Publishing, 2021. http://dx.doi.org/10.1063/5.0061267.

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Boss, Alan F. N., Antonio C. C. Migliano, and Ingrid Wilke. "Terahertz frequency electrical properties of nickel cobalt ferrites." In 2016 41st International Conference on Infrared, Millimeter, and Terahertz waves (IRMMW-THz). IEEE, 2016. http://dx.doi.org/10.1109/irmmw-thz.2016.7758775.

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Kamran, Muhammad, Yasir Abbas, Tanveer Akhtar, and Muhammad Anis-ur-Rehman. "Electrical Properties of Lanthanum Doped Cobalt Ferrite Nanoparticales." In International Symposium on Advanced Materials. Trans Tech Publications Ltd, 2022. http://dx.doi.org/10.4028/p-5v3687.

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Ferrites materials with Spinel structure have been broadly studied in recent years because of numerous technological applications. Lanthanum substituted Co-ferrites nanoparticles (CoLa0.075Fe1.925O4) were synthesized via chemical co-precipitation method. X-ray Diffraction study revealed that prepared nanoparticales are single-phased spinel ferrites. Lattice constant, crystallite size, theoretical densities were estimated from XRD data. Electrical properties have been investigated with frequency ranging from 20Hz to 3MHz at room temperature. Dielectric constant and dielectric loss factor shows decreasing trend with increasing frequency. Ac conductivity exhibit increasing behavior with increasing frequency. The contribution of grains and intergrain boundaries in conduction process was estimated from impedance study. Nyquist plot shows dominant contribution of grain boundary resistance than the grain resistance in conduction mechanism.
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Kumar, N., D. R. Sagar, and P. Kishan. "Cobalt substituted Li-Ti ferrites for phase shifter application." In IEEE International Magnetics Conference. IEEE, 1999. http://dx.doi.org/10.1109/intmag.1999.837210.

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Venkateshwarlu, Ch, M. Prasad, G. Vinod, et al. "A.C conductivity of cobalt substituted in copper ferrites by DSCM." In INTERNATIONAL CONFERENCE ON MULTIFUNCTIONAL MATERIALS (ICMM-2019). AIP Publishing, 2020. http://dx.doi.org/10.1063/5.0022445.

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Watawe, S. C., U. A. Bamne, and B. D. Sarwade. "Interpretation of microstructure dependent magnetic properties of cobalt substituted lithium ferrites." In Proceedings of the Symposium F. WORLD SCIENTIFIC, 2003. http://dx.doi.org/10.1142/9789812704344_0018.

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Parvatheeswara Rao, B., K. H. Rao, P. S. V. Subba Rao, S. Pallam Setty, N. S. Gajbhiye, and O. F. Caltun. "Electric and Magnetic Studies on Copper/Cobalt Substituted Ni-Zn Ferrites." In Proceedings of the Symposium R. WORLD SCIENTIFIC, 2005. http://dx.doi.org/10.1142/9789812701718_0030.

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Pazhanivelu, V., and R. Murugaraj. "Effect of Ni2+ ion on the structural, magnetic and electrical properties of cobalt ferrites." In SOLID STATE PHYSICS: Proceedings of the 56th DAE Solid State Physics Symposium 2011. AIP, 2012. http://dx.doi.org/10.1063/1.4710440.

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Reports on the topic "Cobalt – Minerais – Ferrites de cobalt"

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Song, Sang-Hoon. Magnetic and magnetoelastic properties of M-substituted cobalt ferrites (M=Mn, Cr, Ga, Ge). Office of Scientific and Technical Information (OSTI), 2007. http://dx.doi.org/10.2172/1342575.

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