Relevant bibliographies by topics / Ferrite de cobalt

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Academic literature on the topic 'Ferrite de cobalt'

Author: Grafiati
Published: 4 June 2021
Last updated: 25 May 2024

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Journal articles on the topic "Ferrite de cobalt"

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Pussi, Katariina, Keying Ding, Bernardo Barbiellini, et al. "Atomic Structure of Mn-Doped CoFe2O4 Nanoparticles for Metal–Air Battery Applications." Condensed Matter 8, no. 2 (2023): 49. http://dx.doi.org/10.3390/condmat8020049.

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We discuss the atomic structure of cobalt ferrite nanoparticles doped with Mn via an analysis based on combining atomic pair distribution functions with high energy X-ray diffraction and high-resolution transmission electron microscopy measurements. Cobalt ferrite nanoparticles are promising materials for metal–air battery applications. Cobalt ferrites, however, generally show poor electronic conductivity at ambient temperatures, which limits their bifunctional catalytic performance in oxygen electrocatalysis. Our study reveals how the introduction of Mn ions promotes the conductivity of the cobalt ferrite electrode.
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Majid, Farzana, Amarah Nazir, Sadia Ata, et al. "Effect of Hydrothermal Reaction Time on Electrical, Structural and Magnetic Properties of Cobalt Ferrite." Zeitschrift für Physikalische Chemie 234, no. 2 (2020): 323–53. http://dx.doi.org/10.1515/zpch-2019-1423.

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AbstractCobalt ferrite was synthesized by hydrothermal route in order to investigate the effect of hydrothermal reaction time on structural, magnetic and dielectric properties. The synthesized cobalt ferrite was characterized by X-ray diffraction, Fourier transform infrared and Vibrating-Sample Magnetometer (VMS). XRD data analysis confirmed the formation of cubic inverse spinel ferrite for complete time series as the high intensity peak corresponds to cubic normal spinel structure. The ionic radii, cation distribution among tetrahedral and octahedral sites, lattice parameters, X-ray density, bond lengths were also investigated cobalt ferrite prepared at different hydrothermal reaction time. The crystallite size was found to be in the range of 11.79–32.78 nm. Tolerance factor was near unity that also confirms the formation of cubic ferrites. VSM studies revealed the magnetic nature of cobalt ferrite. The coercivity (1076.3Oe) was observed for a sample treated for 11 h. The squareness ratio was 0.56 that is close to 0.5 which shows uniaxial anisotropy in cobalt ferrite. Frequency dependent dielectric properties i.e. dielectric constant, AC conductivity, tangent loss and AC resistivity are calculated with the help of Impedance Analyzer. Intrinsic cation vibration of cubic spinel ferrites are confirmed from FTIR analysis in the range of 400–4000 cm−1. In view of enhanced properties, this technique could possibly be used for the synthesis of cobalt ferrite for different applications.
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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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Zhang, Chang Sen, Lei Yang, and Feng Zhou. "Preparation and Microstructure of Co-Ferrite Fine Powder." Advanced Materials Research 328-330 (September 2011): 1365–68. http://dx.doi.org/10.4028/www.scientific.net/amr.328-330.1365.

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Cobalt ferrites were prepared by citrate sol-gel method, chemical co-precipitation, mechanical grinding, respectively. The grain size, morphology, and the size of crystal particles were studied by x-ray diffraction (XRD) and scanning electron microscope (SEM). Cobalt ferrite showed different morphologys when prepared by different methods, It was tapered corners which prepared by sol-gel method; It was tetrahedral which prepared by mechanical grinding method; It was sphere which prepared by chemical co-precipitation method. The average grain size of cobalt ferrite was less than 100nm, while particles prepared by chemical precipitation method were the smallest. The size of Cobalt ferrite prepared by sol-gel method was decreased with the cobalt content increased.
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Tomiczek, A. E. "Effect of milling time on microstructure of cobalt ferrites synthesized by mechanical alloying." Archives of Materials Science and Engineering 111, no. 1 (2021): 5–13. http://dx.doi.org/10.5604/01.3001.0015.5561.

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Purpose: of this paper is to determine the effect of manufacturing conditions, especially milling time, on the microstructure and phase composition of CoFe2O4 cobalt ferrite. Design/methodology/approach: Cobalt ferrite (CoFe2O4) has been synthesised from a stoichiometric mixture of CoCo3 and α-Fe2O3 powders in a high energy planetary mill. Annealing at 1000°C for 6 hours after milling was used to improve the solid-state reaction. Calcinated samples were analysed by X-ray diffraction (XRD), and transmission electron microscopy (TEM). The relationship between the milling time of powders, their microstructure, as well as their properties were evaluated. Particles size distribution and scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX) examination were also made. Findings: CoFe2O4 ferrites were successfully synthesized by mechanical alloying of α-Fe2O3 and CoCO3 powders. The powder particles had undergone morphological changes with the increasing milling time. However, the milling time does not affect the ferrite formation rate. It is expected that the improvement of fabrication parameters can further enhance the properties of cobalt ferrite presented in this work. Research limitations/implications: Contribute to research on the structure and properties of cobalt ferrites manufactured by mechanical alloying. Practical implications: The reactive milling and subsequently annealing is an efficient route to synthesise cobalt ferrite powder. However, using steel milling equipment risks powder contamination with iron and chromium from the vials and balls. Originality/value: The results of the experimental research of the developed ferrite materials served as the basis for determining material properties and for further investigation.
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Gupta, Meenal, Anusree Das, Dipankar Das, Satyabrata Mohapatra, and Anindya Datta. "Chemical Synthesis of Rare Earth (La, Gd) Doped Cobalt Ferrite and a Comparative Analysis of Their Magnetic Properties." Journal of Nanoscience and Nanotechnology 20, no. 8 (2020): 5239–45. http://dx.doi.org/10.1166/jnn.2020.18528.

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Lanthanum (La) and gadolinium (Gd) doped cobalt ferrite nanoparticles are synthesized using a soft chemical approach. The analysis of these ferrites using X-ray diffraction (XRD) and transmission electron microscopy (TEM) shows that lattice spacing decreases in the doped ferrite samples. Magnetization data indicates towards the decrease of saturation magnetisation but increase in coercivity with doping. Mössbauer spectroscopy measurements at room temperature indicate increased occupancy of trivalent cations at tetrahedral site. The addition of rare earth dopants reduces the hard-magnetic character of cobalt ferrite.
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Elsayed, Elsayed M., Hazem F. Khalil, Ibrahim A. Ibrahim, Mostafa R. Hussein, and Mohamed M. B. El-Sabbah. "The Significance of Buffer Solutions on Corrosion Processes of Cobalt Ferrite CoFe2O4 Thin Film on Different Substrates." Combinatorial Chemistry & High Throughput Screening 23, no. 7 (2020): 599–610. http://dx.doi.org/10.2174/1386207323666191217130209.

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Background: The spinel ferrite nanoparticles, such as zinc, nickel, and cobalt ferrites have exceptional electronic and magnetic properties. Cobalt ferrite nanomaterial (CoFe2O4) is a hard material that reveals high magnetic, mechanical, and chemical stability. Aim and Objective: The objective of this research is to predict the corrosion behavior of cobalt ferrite (CoFe2O4) thin films deposited on different substrates (platinum Pt, stainless steel S.S, and copper Cu) in acidic, neutral, and alkaline medium. Materials and Method: Cobalt ferrite thin films were deposited on platinum, stainless steel, and copper via electrodeposition-anodization process. After that, corrosion resistance of the prepared nanocrystalline cobalt ferrite on different substrates was investigated in acidic, neutral, and alkaline medium using open circuit potential and potentiodynamic polarization measurements. The crystal structure, crystallite size, microstructure, and magnetic properties of the ferrite films were investigated using a combination of XRD, SEM and VSM. Results: The results of XRD revealed a cubic spinel for the prepared cobalt ferrite CoFe2O4. The average size of crystallites was found to be about 43, 77, and 102 nm precipitated on platinum, stainless steel, and copper respectively. The magnetic properties of which were enhanced by rising the temperature. The sample annealed at 800oC is suitable for practical application as it showed high magnetization saturation and low coercivity. The corrosion resistance of these films depends on the pH of the medium as well as the presence of oxidizing agent. Conclusion: Depending on the obtained corrosion rate, we can recommend that, CoFe2O4 thin film can be used safely in aqueous media in neutral and alkaline atmospheres for Pt and Cu substrates, but it can be used in all pH values for S.S. substrate.
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Beera, Chandra Sekhar, B. Dhanalakshmi, D. Nirmala Devi, et al. "Magnetic and Magnetostrictive Properties of Sol–Gel-Synthesized Chromium-Substituted Cobalt Ferrite." Gels 9, no. 11 (2023): 873. http://dx.doi.org/10.3390/gels9110873.

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Chromium (Cr)-doped cobalt ferrite nanoparticles were synthesized using a sol–gel autocombustion method, with the chemical formula CoCrxFe2xO4. The value of x ranged from 0.00 to 0.5 in 0.1 increments. X-ray diffraction analysis confirmed the development of highly crystalline cubic spinel structures for all samples, with an average crystallite size of approximately 40 to 45 nm determined using the Scherrer equation. Pellets were prepared using a traditional ceramic method. The magnetic and magnetostrictive properties of the samples were tested using strain gauge and VSM (vibrating sample magnetometer) techniques. The results of the magnetic and magnetostrictive tests showed that the chromium-substituted cobalt ferrites exhibited higher strain derivative magnitudes than pure cobalt ferrite. These findings indicated that the introduction of chromium into the cobalt ferrite structure led to changes in the material’s magnetic properties. These changes were attributed to anisotropic contributions, resulting from an increased presence of Co2+ ions at B-sites due to the chromium substitutions. In summary, this study concluded that introducing chromium into the cobalt ferrite structure caused alterations in the material’s magnetic properties, which were explained by changes in the cationic arrangement within the crystal lattice. This study successfully explained these alterations using magnetization and coercivity data and the probable cationic dispersion.
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Gupta, Priyanka, Dr Ravi Kumar Vijai, and Subhash Chander. "Synthesis, Characterization and Magnetic properties of Nanoparticles of Cobalt Doped Ferrite." International Journal of Chemistry, Mathematics and Physics 6, no. 5 (2022): 06–11. http://dx.doi.org/10.22161/ijcmp.6.5.2.

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Ferrites are ceramic like material having magnetic properties which are being utilized for several applications. Cobalt ferrites are hard magnetic material with high coercivity. In our study Crystalline, Magnetic nanoparticles of Cobalt ferrite Co0.8Fe2.2O4 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, FESEM and TEM. Particle size found 14.26nm by using Debye Scherrer method. Scanning electron microscopic (SEM) studies revealed nano-crystalline nature of the sample. AFM showed surface roughness. Magnetic properties were investigated using VSM (vibrating sample magnetometer). Various magnetic parameters such as saturation magnetization (Ms) and remanence (Mr) and coercivity (Hc) are obtained from the hysteresis loops. The calculated value of saturation magnetization in our study for Cobalt ferrite was found lower than the value reported for the bulk. The coercivity was found very high which indicate that the nanoparticles exhibit ferromagnetic behavior.
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Alotaibi, M. A., I. Ud Din, A. I. Alharthi, et al. "Synthesis, Characterization, and Magnetic Behavior of Cobalt-Ferrite Nanoparticles under Variant Temperature Conditions." Физика твердого тела 63, no. 4 (2021): 513. http://dx.doi.org/10.21883/ftt.2021.04.50746.pss109.

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Wet chemical method was applied for the synthesis of cobalt-ferrite nanoparticles. The physicochemical properties were investigated by number of analytical techniques. TGA revealed the thermal stability of synthesized cobalt-ferrite nanoparticles. X-ray diffraction studies displayed the nanoparticles crystalline nature. Structure of cobalt-ferrite nanoparticles was confirmed via infrared spectroscopy by manifesting Co and Fe ions absorption peaks. Morphological studies showed synthesis of nanoparticles of cobalt-ferrite by employing field emissions scanning electron microscopy. The magnetic properties of cobalt-ferrite nanoparticles were investigated by vibrating sample magnetometer (VSM). The X-ray photoelectron spectroscopy studies confirmed the synthesis of cobalt-ferrite by displaying the oxidation of Co as Co2+ and Fe as Fe3+, respectively. The VSM results revealed that the magnetic characteristics of cobalt-ferrite nanoparticles were completely changed by the variation of temperature. Keywords: ferrite nanoparticles, VSM, temperature effect, magneton number, anisotropy constant.
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Dissertations / Theses on the topic "Ferrite 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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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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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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Scott, Byron L. "Magneto-Optical Study of Cobalt Ferrite Nanoparticles." ScholarWorks@UNO, 2007. http://scholarworks.uno.edu/td/623.

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A magneto-optical study of CoxFe1-xFe2O4 nanoparticles is presented, with cobalt molar ratio 0.x.1. The ferrite nanoparticles were produced using a generic wet-chemical synthesis procedure. Stoichiometric amounts of Fe2+, Fe3+ and Co2+ salts are dissolved in a non-aqueous polar medium (diethylene glycol). A coprecipitation reaction with sodium hydroxide produces ferrite nanoparticles with average diameter of 6 nm. The nanoparticles can be stabilized by tetramethyl ammonium hydroxide in water, or, alternatively, the nanoparticles can be treated with a hydrophobic capping ligand with a carboxylic acid or amine head group and suspended in a non-polar organic solvent. As a complete structural analysis of this series of samples is quite difficult due to the similarities of the constituents, magneto-optical spectroscopy is performed to decode the structural orientations of each cation involved. Faraday rotation was measured on nanoparticle samples dried on an amorphous silica substrate from 400-1000 nm.
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Ajroudi, LIlia. "Ferrites de cobalt nanostructurés ; élaboration, caractérisation, propriétés catalytiques, électriques et magnétiques." Electronic Thesis or Diss., Toulon, 2011. http://www.theses.fr/2011TOUL0017.

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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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Olsson, Richard T. "Alternative routes to uniformly dispersed cobalt ferrite nanocomposites /." Stockholm : Fiber- och polymerteknologi, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4328.

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7

Spillane, Liam Jonathan. "Nanoanalytical electron microscopy of cobalt ferrite thin films." Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/6447.

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Electron energy­‐loss spectroscopy (EELS) is a powerful method for providing detailed information on the bonding, chemical structure and electronic structure of materials. In this work, EELS has been used to correlate variations in magnetic properties of cobalt ferrite films with film thickness and post‐processing conditions. Magnetometry performed on as‐deposited and oxygen post­‐annealed films has shown saturation magnetization (Ms) to be strongly affected by post processing. This has been attributed to an enhancement in superexchange by reoxidation and cation ordering processes during post­‐anneal. To date this has not been confirmed using nanoanalytical techniques. This work addresses this issue. In particular, it is of interest to determine local changes in the degree of inversion of the ferrite spinel in order to link local chemical changes to bulk magnetic properties. Two sample preparation techniques were used to produce electron transparent sections – conventional ion beam milling and focussed ion beam (FIB) milling using a dual beam system. The suitability of each technique is discussed in terms of, sample damage, thickness, reproducibility and reliability. Aberration corrected HRTEM was used to investigate the microstructure of the thin films. Lattice strain and defect strain were quantified at increasing distance from the substrate/interface in as‐deposited and oxygen post­‐annealed cobalt ferrite films and structural defects responsible for misfit accommodation were characterised. Local variation in cation valence and coordination cobalt in an oxygen post­‐annealed film was investigated by monochromated EELS of the iron and cobalt L2,3­‐edges in the electron energy­‐loss spectrum. A method to determine the spinel degree of inversion (λ) by multiple linear least squares fitting was developed using data acquired from reference materials. A commercially available full multiple scattering code (FEFF 8.2) was used to aid interpretation of reference spectra and the fitting technique used to determine λ was applied to the cobalt ferrite thin film in order to identify variations in λ.
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Haffer, Stefanie [Verfasser]. "Mesoporous spinel-type cobalt oxide, cobalt ferrite and alumina by nanocasting / Stefanie Haffer." Paderborn : Universitätsbibliothek, 2014. http://d-nb.info/1046651994/34.

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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." Electronic Thesis or Diss., Toulon, 2018. http://www.theses.fr/2018TOUL0007.

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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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Ramos, Ana V. "Epitaxial Cobalt-Ferrite Thin Films for Room Temperature Spin Filtering." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2008. http://tel.archives-ouvertes.fr/tel-00394398.

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Le filtrage de spin est un phénomène physique qui permet de générer des courants d'électrons polarisés en spin grâce au transport sélectif à travers une barrière tunnel magnétique. Dans cette thèse, nous présentons une étude du matériau ferrite de cobalt (CoFe2O4), dont le caractère isolant et la température de Curie élevée en font un très bon candidat pour le filtrage de spin à température ambiante. L'élaboration des couches minces de CoFe2O4 a été réalisée par épitaxie par jets moléculaires assistée par plasma d'oxygène. Les propriétés structurales, chimiques et magnétiques ont été étudiées par plusieurs méthodes de caractérisation in situ et ex situ. Des jonctions tunnel à base de CoFe2O4 ont été préparées pour des mesures de transport tunnel polarisé en spin, soit par la méthode de Meservey-Tedrow, soit par des mesures de magnétorésistance tunnel (TMR). Dans ce dernier cas, nous avons porté une attention particulière au retournement magnétique de la barrière tunnel de CoFe2O4 et de la contre électrode magnétique (Co ou Fe3O4), une étape cruciale avant toute mesure de TMR. Dans les deux cas, les mesures de transport tunnel polarisé en spin ont révélé des polarisations significatives du courant tunnel à basse température, et à température ambiante pour les mesures de TMR. Par ailleurs, nous avons trouvé une dépendance unique entre la TMR et la tension appliquée qui reproduit celle prédite théoriquement pour les barrières tunnel magnétiques. Nous démontrons ainsi que les barrières tunnel de CoFe2O4 constituent un système modèle pour étudier le filtrage de spin dans une large gamme de températures.
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Books on the topic "Ferrite de cobalt"

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Sehar, Fatima, and Zeeshan Mustafa. Synthesis and characterization of bismuth doped cobalt ferrite. LAP Lambert Academic Publishing, 2015.

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Book chapters on the topic "Ferrite de cobalt"

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Rao, G. S. N., O. F. Caltun, K. H. Rao, B. Parvatheeswara Rao, H. L. Wamocha, and H. H. Hamdeh. "Influence of silicon and cobalt substitutions on magnetostriction coefficient of cobalt ferrite." In ICAME 2007. Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-78697-9_80.

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Pileni, M. P., N. Moumen, I. Lisiecki, P. Bonville, and P. Veillet. "Ferrofluid of Cobalt Ferrite Differing by Their Particle Sizes." In Nanoparticles in Solids and Solutions. Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-015-8771-6_16.

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Rao, G. S. N., O. F. Caltun, K. H. Rao, et al. "Mössbauer and magnetic study of silicon substituted cobalt ferrite." In ICAME 2007. Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-78697-9_60.

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Ibrahim, Amal M., Morsi M. Mahmoud, and M. M. Abd El-Latif. "Microwave Synthesis of Cobalt-Ferrite Nano-Particles by Polyol Method." In Ceramic Transactions Series. John Wiley & Sons, Inc., 2010. http://dx.doi.org/10.1002/9780470930953.ch3.

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Morais, P. C., A. C. Oliveira, V. K. Garg, et al. "Synthesis, thermal treatment and characterization of cobalt ferrite-based nanocomposites." In HFI/NQI 2007. Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-85320-6_60.

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Shankar, S., Vinita Tuli, S. Gaurav, O. P. Thakur, and M. Jayasimhadri. "Variable Dielectric and Ferroelectric Properties in Size-Controlled Cobalt Ferrite." In Springer Proceedings in Materials. Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-5971-3_4.

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El Foulani, A. H., R. C. Pullar, M. Amjoud, K. Ouzaouit, and A. Aamouche. "Magnetic and Nanostructural Properties of Cobalt–Zinc Ferrite for Environmental Sensors." In Handbook of Environmental Materials Management. Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-319-73645-7_85.

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El Foulani, A. H., R. C. Pullar, M. Amjoud, K. Ouzaouit, and A. Aamouche. "Magnetic and Nanostructural Properties of Cobalt–Zinc Ferrite for Environmental Sensors." In Handbook of Environmental Materials Management. Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-58538-3_85-1.

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Sagadevan, Suresh, Jiban Podder, and Isha Das. "Synthesis and Characterization of Cobalt Ferrite (CoFe2O4) Nanoparticles Prepared by Hydrothermal Method." In Springer Proceedings in Physics. Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-44890-9_14.

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Andrade, P. L., V. A. J. Silva, J. C. Maciel, et al. "Preparation and characterization of cobalt ferrite nanoparticles coated with fucan and oleic acid." In LACAME 2012. Springer Netherlands, 2013. http://dx.doi.org/10.1007/978-94-007-6482-8_25.

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Conference papers on the topic "Ferrite de cobalt"

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Gryaznova, Mariya, and Elena Belaya. "Thermolysis of cobalt ferrite." In PROCEEDINGS OF INTERNATIONAL CONFERENCE ON RECENT TRENDS IN MECHANICAL AND MATERIALS ENGINEERING: ICRTMME 2019. AIP Publishing, 2020. http://dx.doi.org/10.1063/5.0023203.

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Pawar, S. J., S. M. Patil, M. Chithra, Subasa C. Sahoo, and P. B. Patil. "Cobalt ferrite nanoparticles for supercapacitor application." In DAE SOLID STATE PHYSICS SYMPOSIUM 2019. AIP Publishing, 2020. http://dx.doi.org/10.1063/5.0017184.

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Parmar, S. K., and G. J. Baldha. "The electrical properties of substituted cobalt ferrite." In PROCEEDING OF INTERNATIONAL CONFERENCE ON RECENT TRENDS IN APPLIED PHYSICS AND MATERIAL SCIENCE: RAM 2013. AIP, 2013. http://dx.doi.org/10.1063/1.4810613.

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Shanmugavel, T., S. Gokul Raj, G. Rajarajan, and G. Ramesh Kumar. "Rapid phase synthesis of nanocrystalline cobalt ferrite." In SOLID STATE PHYSICS: Proceedings of the 58th DAE Solid State Physics Symposium 2013. AIP Publishing LLC, 2014. http://dx.doi.org/10.1063/1.4872651.

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Jeyanthi, J., R. Jayalakshmi, and Suganya Devi B. "Magnetic cobalt ferrite nanocomposites: Synthesis and characterization." In Proceedings of the International Conference on Nanotechnology for Better Living. Research Publishing Services, 2016. http://dx.doi.org/10.3850/978-981-09-7519-7nbl16-rps-293.

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Burra, K. G., and A. K. Gupta. "Isothermal Splitting of CO2 to CO Using Cobalt-Ferrite Redox Looping." In ASME 2020 Power Conference collocated with the 2020 International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/power2020-16960.

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Abstract Rising atmospheric CO2 levels from significant imbalance between carbon emissions from fossil fuel utilization, especially for energy and chemicals, and natural carbon sequestration rates is known to drive-up the global temperatures and associated catastrophic climate changes, such as rising mean sea level, glacial melting, and extinction of ecosystems. Carbon capture and utilization techniques are necessary for transition from fossil fuel infrastructure to renewable energy resources to help delay the dangers of reaching to the point of positive feedback between carbon emissions and climate change which can drive terrestrial conditions to uninhabitable levels. CO2 captured from the atmosphere directly or from flue gases of a power plant can be recycled and transformed to CO and syngas for use as energy and value-added chemicals. Utilizing renewable energy resources to drive CO2 conversion to CO via thermochemical redox looping can provide a carbon negative renewable energy conversion pathway for sustainable energy production as well as value-added products. Substituted ferrites such as Co-ferrite, Mnferrite were found to be promising materials to aid the conversion of CO2 to CO at lower reduction temperatures. Furthermore, the conversion of these materials in the presence of Al2O3 provided hercynite cycling, which further lowered the reduction temperature. In this paper, Co-ferrite and Co-ferrite-alumina prepared via co-precipitation were investigated to understand their potential as oxygen carriers for CO2 conversion under isothermal redox looping. Isothermal reduction looping provided improved feasibility in redox conversion since it avoids the need for temperature swinging which improves thermal efficiency. These efforts alleviates the energy losses in heat recovery while also reducing thermal stresses on both the materials and the reactor. Lab-scale testing was carried out at 1673 K on these materials for extended periods and multiple cycles to gain insights into cyclic performance and the feasibility of sintering, which is a common issue in iron-oxide-based oxygen carriers. Cobalt doping provided with lowering of reduction temperature requirement at the cost of oxidation thermodynamic spontaneity that required increased oxidation temperature. At the concentrations examined, these opposing phenomenon made isothermal redox operation feasible by providing high CO yields comparable to oxygen carriers in the literature, which were operated at different temperatures for reduction and oxidation. Significantly high CO yields (∼ 750 μmol/g) were obtained from Co-ferrite isothermal redox looping. Co-ferrite-alumina provided lower CO yields compared to Co-ferrite. The oxygen storage was similar to those reported in the literature on isothermal H2O splitting, but with improved morphological stability at high temperature, especially compared to ferrite. This pathway of oxygen carrier development is considered suitable with further requirement in optimization for scaling of renewable CO2 conversion into valuable products.
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Rani, Ritu, Sangeeta Thakur, M. Singh, Alka B. Garg, R. Mittal, and R. Mukhopadhyay. "Processing and Characterization of Cobalt-Zinc Nano Ferrite." In SOLID STATE PHYSICS, PROCEEDINGS OF THE 55TH DAE SOLID STATE PHYSICS SYMPOSIUM 2010. AIP, 2011. http://dx.doi.org/10.1063/1.3605847.

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Supriya, Sweety, Sunil Kumar, Rabichandra Pandey, Lagen Kumar Pradhan, and Manoranjan Kar. "Ferroelectric like behavior in Cr substituted cobalt ferrite." In 2ND INTERNATIONAL CONFERENCE ON CONDENSED MATTER AND APPLIED PHYSICS (ICC 2017). Author(s), 2018. http://dx.doi.org/10.1063/1.5032725.

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Rao, G. S. N., O. F. Caltun, K. H. Rao, et al. "Compositional Dependence of Magnetostrictive Properties of Cobalt Ferrite." In INTERNATIONAL CONFERENCE ON MAGNETIC MATERIALS (ICMM-2010). AIP, 2011. http://dx.doi.org/10.1063/1.3601839.

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Sharma, M. P., Dinesh Uthra, and H. S. Tewari. "Synthesis and characterization of cerium substituted cobalt ferrite." In ADVANCED MATERIALS AND RADIATION PHYSICS (AMRP-2020): 5th National e-Conference on Advanced Materials and Radiation Physics. AIP Publishing, 2021. http://dx.doi.org/10.1063/5.0052392.

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Reports on the topic "Ferrite 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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