Inhaltsverzeichnis
Auswahl der wissenschaftlichen Literatur zum Thema „Ferrites de cobalt“
Geben Sie eine Quelle nach APA, MLA, Chicago, Harvard und anderen Zitierweisen an
Machen Sie sich mit den Listen der aktuellen Artikel, Bücher, Dissertationen, Berichten und anderer wissenschaftlichen Quellen zum Thema "Ferrites de cobalt" bekannt.
Neben jedem Werk im Literaturverzeichnis ist die Option "Zur Bibliographie hinzufügen" verfügbar. Nutzen Sie sie, wird Ihre bibliographische Angabe des gewählten Werkes nach der nötigen Zitierweise (APA, MLA, Harvard, Chicago, Vancouver usw.) automatisch gestaltet.
Sie können auch den vollen Text der wissenschaftlichen Publikation im PDF-Format herunterladen und eine Online-Annotation der Arbeit lesen, wenn die relevanten Parameter in den Metadaten verfügbar sind.
Zeitschriftenartikel zum Thema "Ferrites de cobalt"
1
de la Torre, Ernesto, Ana Lozada, Maricarmen Adatty und Sebastián Gámez. „Activated Carbon-Spinels Composites for Waste Water Treatment“. Metals 8, Nr. 12 (16.12.2018): 1070. http://dx.doi.org/10.3390/met8121070.
Der volle Inhalt der QuelleAnnotation:
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.
2
Boss, Alan F. N., Antonio C. C. Migliano und Ingrid Wilke. „The Influence of Stoichiometry on the Index of Refraction of Cobalt Ferrite Samples at Terahertz Frequencies“. MRS Advances 2, Nr. 58-59 (2017): 3663–66. http://dx.doi.org/10.1557/adv.2017.355.
Der volle Inhalt der QuelleAnnotation:
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.
3
Al-Kadhi, Nada S., Ghadah M. Al-Senani, Rasmiah S. Almufarij, Omar H. Abd-Elkader und Nasrallah M. Deraz. „Green Synthesis of Nanomagnetic Copper and Cobalt Ferrites Using Corchorus Olitorius“. Crystals 13, Nr. 5 (03.05.2023): 758. http://dx.doi.org/10.3390/cryst13050758.
Der volle Inhalt der QuelleAnnotation:
This study aims to develop a self-combustion method for use in the preparation of copper and cobalt ferrites. This development was based on the full use of dry leaves of Corchorus olitorius plant in order to stimulate the preparation of the studied ferrites by making full use of the small amount of carbon produced from the combustion process. The fabrication of CuFe2O4 and CoFe2O4 with spinel-type structures and the Fd3m space group is confirmed by XRD and FTIR investigations. Two major vibration bands occur laterally at 400 cm−1 and 600 cm−1. We were able to understand the existence of two stages through the thermal behavior based on TG-DTG analysis for the materials under investigation. The first is from room temperature to 600 °C, which indicates the formation of reacting oxides with Co or Cu ferrites, while the second is from 600–1000 °C, which indicates the growth in the ferrite fabrication. The surface morphological analyses (SEM/EDS and TEM) display formation of homogeneous and nanosized particles. The surface properties of the samples containing CoFe2O4 are superior compared to those of the samples not containing CuFe2O4. Every sample under investigation displays type-IV-based isotherms with a type-H3 hysteresis loop. The VSM approach was used to evaluate the magnetic characteristics of Cu and Co ferrites. Copper ferrites have a magnetization of 15.77 emu/g, and cobalt ferrites have a magnetization of 19.14 emu/g. Moreover, the squareness (0.263) and coercivity (716.15 G) of cobalt ferrite are higher than those of copper ferrite.
4
Pussi, Katariina, Keying Ding, Bernardo Barbiellini, Koji Ohara, Hiroki Yamada, Chuka Onuh, James McBride, Arun Bansil, Ray K. Chiang und Saeed Kamali. „Atomic Structure of Mn-Doped CoFe2O4 Nanoparticles for Metal–Air Battery Applications“. Condensed Matter 8, Nr. 2 (24.05.2023): 49. http://dx.doi.org/10.3390/condmat8020049.
Der volle Inhalt der QuelleAnnotation:
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.
5
Frolova, Liliya A. „Investigation of Magnetic and Photocatalytic Properties of CoFe2O4 Doped La3+, Nd3+, I3+“. ECS Meeting Abstracts MA2022-01, Nr. 30 (07.07.2022): 2496. http://dx.doi.org/10.1149/ma2022-01302496mtgabs.
Der volle Inhalt der QuelleAnnotation:
Cobalt ferrites are widely used for permanent magnets, magnetic fluids, microwave devices, high density information storage and environmental technologies. The properties of nanosized magnetic materials strongly depend on the shape, size, and phase composition of the particles. The great interest of researchers in nanosized materials in recent years is associated with the possibility of changing the properties of magnetic materials by controlling the particle size and distribution of cations over sublattices in ferrite [1]. Nanoparticles of doped cobalt ferrite showed improved physicochemical characteristics compared to individual components due to the synergistic effect of the mutual presence of cations. Currently, various technologies for producing ferrites are used. However, to obtain a single-phase product, calcination of the precursors at a temperature of 1300-1500 0C is required, which causes agglomeration and sintering of the product. The use of modern methods of electrochemical synthesis is the basis for obtaining ferrites from transition materials with a given set of properties. A characteristic recent trend is the development of new technologies and compositions for the production of precisely nanodispersed ferrites [2]. The purpose of this work is to study the possibility of using contact low-temperature nonequilibrium plasma for the synthesis of cobalt ferrites doped with La3+, Nd3+, I3+ cations, to establish a relationship between the cationic composition of ferrites and its phase composition, magnetic and structural characteristics. Ferrites were synthesized in the form of nanoparticles using contact nonequilibrium low temperature plasma in an electrochemical reactor. The crystalline microstructure of the samples was revealed by X-ray diffraction and X-ray phase methods. The magnetic characteristics were determined from hysteresis loops. The EPR spectra were obtained on a Radiopan SE/X-2543 radiospectrometer. To characterize the EPR signals, the intensity and width of the signal, and the resonant frequency were used. The visualization of the dependences of the technological characteristics of La3+-Nd3+-I3+ ferrites on the cationic composition was carried out by the simplex method using the STATISTICA 12 program. It has been established that the nature of the rare-earth metal cation in cobalt ferrite directly determines the magnetic and photocatalytic properties of spinel ferrites. The effect of the mutual influence of the content of cations on the saturation magnetization and coercive force is determined. The most influencing factor is the content of neodymium cations. Low values of the coercive force for Mn-Zn and Co-Zn ferrites and high values for the entire range of Co-Mn ferrites are established. An increase in the content of cobalt cations leads to an increase in the saturation magnetization value of Co-Mn ferrites. The EPR spectra show that the values of the resonance field and linewidth in the EPR spectrum correlate with the value of magnetic saturation. Simultaneous substitution of Nd3+ and La3+ in CoFe2O4 nanoparticles affected the structure, magnetic and photocatalytic properties. Structural parameters were investigated and calculated using X-ray diffraction studies. The magnetization analyzes were carried out at room temperature. Various magnetic parameters have been obtained and discussed, including remanence (Mr), coercive force (Hc), saturation magnetization (Ms), squareness ratio (SQR=Mr/Ms) and magnetic moment (nB). An increase in Mr, Ms, Hc and nB was found at lower concentrations of Nd3+ and La3+. An increase in the content of Nd3+ cations leads to a significant increase in the coercive force. The analysis of photocatalytic activity in the reaction of isolation of furacilin showed the best results (destruction rate 98%, time 40 minutes) for the ternary composition. References Caldeira, Luis Eduardo, et al. "Correlation of synthesis parameters to the structural and magnetic properties of spinel cobalt ferrites (CoFe2O4)–an experimental and statistical study." Journal of Magnetism and Magnetic Materials550 (2022): 169128. Lu, Yuzheng, et al. "Effect of Gd and Co contents on the microstructural, magneto-optical and electrical characteristics of cobalt ferrite (CoFe2O4) nanoparticles." Ceramics International2 (2022): 2782-2792.
6
Majid, Farzana, Amarah Nazir, Sadia Ata, Ismat Bibi, Hafiz Shahid Mehmood, Abdul Malik, Adnan Ali und Munawar Iqbal. „Effect of Hydrothermal Reaction Time on Electrical, Structural and Magnetic Properties of Cobalt Ferrite“. Zeitschrift für Physikalische Chemie 234, Nr. 2 (25.02.2020): 323–53. http://dx.doi.org/10.1515/zpch-2019-1423.
Der volle Inhalt der QuelleAnnotation:
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.
7
Hochu, F., und M. Lenglet. „Co(II) Optical Absorption in Spinels: Infrared and Ligand-Field Spectroscopic Study of the Ionicity of the bond. Magnetic Structure and Co2+→Fe3+MMCT in Ferrites. Correlation with the Magneto-Optical Properties“. Active and Passive Electronic Components 20, Nr. 3 (1998): 169–87. http://dx.doi.org/10.1155/1998/16871.
Der volle Inhalt der QuelleAnnotation:
The analysis of the infrared and ligand field spectra of COM2O4spinels reveals that the ionicity of these compounds varies in the following order aluminate > gallate > ferrite and chromite > rhodite and cobaltite. A linear relation has been established between the Δ(LO-TO)1splitting, Racah parameter and the ionic-covalent parameterSSp=ΣICP+tetra∑ICPocta. The influence of strong superexchange interactions on the optical spectrum of cobalt ferrites has been studied. The cation distribution has been established by EXAFS and XANES measurements. The cluster (CoFeO10)15–is characterized by a large MMCT transition Co2+→Fe3+at 1.65–1.7 eV (FWMH: 1.35–1.95 eV). The4A2→4T1(P) tetrahedral cobalt(II) in ferrimagnetic compounds is overlapped by the MMCT band. This study and the reinvestigation of the iron(III) electronic spectrum is ferrites may explain the magneto-optical properties of mixed cobalt-ferrites.
8
Gupta, Priyanka, Dr Ravi Kumar Vijai und Subhash Chander. „Synthesis, Characterization and Magnetic properties of Nanoparticles of Cobalt Doped Ferrite“. International Journal of Chemistry, Mathematics and Physics 6, Nr. 5 (2022): 06–11. http://dx.doi.org/10.22161/ijcmp.6.5.2.
Der volle Inhalt der QuelleAnnotation:
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.
9
Kikuchi, Takeyuki, Tatsuya Nakamura, Masamichi Miki, Makoto Nakanishi, Tatsuo Fujii, Jun Takada und Yasunori Ikeda. „Synthesis of Hexagonal Ferrites by Citric Complex Method“. Advances in Science and Technology 45 (Oktober 2006): 697–700. http://dx.doi.org/10.4028/www.scientific.net/ast.45.697.
Der volle Inhalt der QuelleAnnotation:
Various hexagonal ferrites, which include hard and soft ferrites, were prepared by citric complex method. High purity reagent of strontium carbonate, iron (III) nitrate ennnahydrate, cobalt (II) nitrate hexahydrate and lanthanum oxide were used as starting materials. Prepared aqueous solution was heated for dehydration and gelling. Thermal pyrolysis was carried out by heating the gel. The obtained precursor powders were ground with an alumina mortar and compacted by uniaxial pressing into disk specimens and then heated at temperature range between 1023K and 1523K in air. Phase identification and determination of lattice parameters were carried out by powder X-ray diffraction. Scanning Electron Microscope was utilized to investigate the microstructure of the polycrystalline ferrites. Magnetic properties were discussed by magnetization measurements by using a vibration sample magnetometer. Magnetization and coercive force were measured. In the case of M-type ferrite, M-type barium and strontium ferrites were formed at vary low temperature relative to by conventional synthesis. The lanthanum and cobalt substituted M-type strontium ferrite ultra fine powders prepared by citric complex method showed extremely large coercive force.
10
Zhang, Chang Sen, Lei Yang und 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.
Der volle Inhalt der QuelleAnnotation:
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.
Dissertationen zum Thema "Ferrites de cobalt"
1
Ajroudi, LIlia. „Ferrites de cobalt nanostructurés ; élaboration, caractérisation, propriétés catalytiques, électriques et magnétiques“. Thesis, Toulon, 2011. http://www.theses.fr/2011TOUL0017/document.
Der volle Inhalt der QuelleAnnotation:
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 pointThis 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
2
Ajroudi, LIlia. „Ferrites de cobalt nanostructurés ; élaboration, caractérisation, propriétés catalytiques, électriques et magnétiques“. Electronic Thesis or Diss., Toulon, 2011. http://www.theses.fr/2011TOUL0017.
Der volle Inhalt der QuelleAnnotation:
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 pointThis 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
3
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.
Der volle Inhalt der QuelleAnnotation:
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 cobaltDifferent 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
4
Mahhouti, Zakaria. „Synthesis and characterization of functional monodispersed cobalt ferrite nanoparticles“. Electronic Thesis or Diss., Amiens, 2019. http://www.theses.fr/2019AMIE0010.
Der volle Inhalt der QuelleAnnotation:
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 transformationIn 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
5
Gonçalves, Nizomar de Sousa. „Síntese e caracterização de nanopartículas de ferritas de níquel e de colbalto preparadas pelo método sol-gel proteico“. reponame:Repositório Institucional da UFC, 2011. http://www.repositorio.ufc.br/handle/riufc/9794.
Der volle Inhalt der QuelleAnnotation:
GONÇALVES, Nizomar de Sousa. Síntese e caracterização de nanopartículas de ferritas de níquel e de colbalto preparadas pelo método sol-gel proteico. 2011. 119 f. Tese (Doutorado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2011.Submitted by Edvander Pires (edvanderpires@gmail.com) on 2014-11-14T18:02:46Z No. of bitstreams: 1 2011_tese_nsgoncalves.pdf: 10518347 bytes, checksum: e003b7eaec2ac72b848255b9299513ce (MD5)
Approved for entry into archive by Edvander Pires(edvanderpires@gmail.com) on 2014-11-14T18:18:09Z (GMT) No. of bitstreams: 1 2011_tese_nsgoncalves.pdf: 10518347 bytes, checksum: e003b7eaec2ac72b848255b9299513ce (MD5)
Made available in DSpace on 2014-11-14T18:18:09Z (GMT). No. of bitstreams: 1 2011_tese_nsgoncalves.pdf: 10518347 bytes, checksum: e003b7eaec2ac72b848255b9299513ce (MD5) Previous issue date: 2011
In this work we present the study of the synthesis of nanosized nickel and cobalt ferrites by sol-gel proteic method. This work revisited the method of X-ray powder diffraction analysis known as Williamson-Hall plotting. This method provides size-strain studies in nanoparticles samples. Nickel ferrites has presented particle sizes that increase when the calcination temperature increases. Nickel ferrites nanoparticles were characterized by Mössbauer spectroscopy. Sample calcined at 400°C has presented superparamagnetic properties and those calcined at higher temperatures behavior as magnetic materials. Cobalt ferrites nanoparticles were charcterized by X-ray powder diffraction, small angle X-ray scattering e magnetization. Cobalt ferrites has not presented superparamagnetic behavior. For the synthesis of cobalt ferrites some parameters that are important to the process control were studied: calcination temperature, calcination time, heat rate. We have shown the relation among those parameters and the particle size and properties control to the cobalt ferrite nanoparticles.
Este trabalho apresenta o estudo da síntese de nanopartículas de ferritas de níquel e de cobalto usando o método sol-gel proteico. Inicialmente, é resgatado o método do gráfico de Williamson-Hall na análise dos dados de difração de raios X. Este método permite calcular o tamanho médio de partícula e a microdeformação. Ferritas de níquel apresentaram tamanhos de partículas que crescem com o aumento da temperatura de calcinação. Nanopartículas de ferrita de níquel foram caracterizadas por espectroscopia Mössbauer. As amostras calcinadas a 400 °C apresentaram comportamento superparamagnético ao passo que aquelas calcinadas em temperaturas superiores apresentaram comportamento magnético. As ferritas de cobalto foram caracterizadas usando difração de raios X, espalhamento de raios X a baixo ângulo e medidas de magnetização. As ferritas de cobalto não apresentaram comportamento superparamagnético. Na síntese das ferritas de cobalto, alguns parâmetros associados com o controle do processo foram estudados: temperatura de calcinação, tempo de calcinação, taxa de aquecimento/resfriamento. Deduziu-se a relação de cada parâmetro com o controle do tamanho de partícula e das propriedades das ferritas de cobalto.
6
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.
Der volle Inhalt der QuelleAnnotation:
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 cobaltDifferent 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
7
Aygar, Gulfem. „Preparation Of Silica Coated Cobalt Ferrite Magnetic Nanoparticles For The Purification Of Histidine-tagged Proteins“. Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613894/index.pdf.
Der volle Inhalt der QuelleAnnotation:
The magnetic separation approach has several advantages compared with conventional separation methodsit can be performed directly in crude samples containing suspended solid materials without pretreatment, and can easily isolate some biomolecules from aqueous systems in the presence of magnetic gradient fields. This thesis focused on the development of new class of magnetic separation material particularly useful for the separation of histidine-tagged proteins from the complex matrixes through the use of imidazole side chains of histidine molecules. For that reason surface modified cobalt ferrite nanoparticles which contain Ni-NTA affinity group were synthesized. Firstly, cobalt ferrite nanoparticles with a narrow size distribution were prepared in aqueous solution using the controlled coprecipitation method. In order to obtain small size of agglomerates two different dispersants, oleic acid and sodium chloride, were tried. After obtaining the best dispersant and optimum experimental conditions, ultrasonic bath was used in order to decrease the size of agglomerates. Then, they were coated with silica and this was followed by surface modification of these nanoparticles by amine in order to add functional groups on silica shell. Next, &ndash
COOH functional groups were added to silica coated cobalt ferrite magnetic nanoparticles through the NH2 groups. After that N&alpha
,N&alpha
-Bis(carboxymethyl)-L-lysine hydrate, NTA, was attached to carboxyl side of the structure. Finally, nanoparticles were labeled with Ni (II) ions. The size of the magnetic nanoparticles and their agglomerates were determined by FE-SEM images, particle size analyzer, and zeta potential analyzer (zeta-sizer). Vibrational sample magnetometer (VSM) was used to measure the magnetic behavior of cobalt ferrite and silica coated cobalt ferrite magnetic nanoparticles. Surface modifications of magnetic nanoparticles were followed by FT-IR measurements. ICP-OES was used to find the amount of Ni (II) ion concentration that was attached to the magnetic nanoparticle.
8
Ourry, Laurence. „Relation structure-propriétés de matériaux hybrides magnétiques polymère-ferrites spinelles“. Paris 7, 2014. http://www.theses.fr/2014PA077193.
Der volle Inhalt der QuelleAnnotation:
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 thèseI 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
9
GonÃalves, Nizomar de Sousa. „Sintese e caracterizaÃÃo de nanoparticulas de ferritas de nÃquel e de colbalto preparadas pelo mÃtodo sol-gel proteico“. Universidade Federal do CearÃ, 2011. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=6787.
Der volle Inhalt der QuelleAnnotation:
CoordenaÃÃo de AperfeiÃoamento de NÃvel SuperiorEste trabalho apresenta o estudo da sÃntese de nanopartÃculas de ferritas de nÃquel e de cobalto usando o mÃtodo sol-gel proteico. Inicialmente, Ã resgatado o mÃtodo do grÃfico de Williamson-Hall na anÃlise dos dados de difraÃÃo de raios X. Este mÃtodo permite calcular o tamanho mÃdio de partÃcula e a microdeformaÃÃo. Ferritas de nÃquel apresentaram tamanhos de partÃculas que crescem com o aumento da temperatura de calcinaÃÃo. NanopartÃculas de ferrita de nÃquel foram caracterizadas por espectroscopia MÃssbauer. As amostras calcinadas a 400 ÂC apresentaram comportamento superparamagnÃtico ao passo que aquelas calcinadas em temperaturas superiores apresentaram comportamento magnÃtico. As ferritas de cobalto foram caracterizadas usando difraÃÃo de raios X, espalhamento de raios X a baixo Ãngulo e medidas de magnetizaÃÃo. As ferritas de cobalto nÃo apresentaram comportamento superparamagnÃtico. Na sÃntese das ferritas de cobalto, alguns parÃmetros associados com o controle do processo foram estudados: temperatura de calcinaÃÃo, tempo de calcinaÃÃo, taxa de aquecimento/resfriamento. Deduziu-se a relaÃÃo de cada parÃmetro com o controle do tamanho de partÃcula e das propriedades das ferritas de cobalto.
In this work we present the study of the synthesis of nanosized nickel and cobalt ferrites by sol-gel proteic method. This work revisited the method of X-ray powder diffraction analysis known as Williamson-Hall plotting. This method provides size-strain studies in nanoparticles samples. Nickel ferrites has presented particle sizes that increase when the calcination temperature increases. Nickel ferrites nanoparticles were characterized by MÃssbauer spectroscopy. Sample calcined at 400ÂC has presented superparamagnetic properties and those calcined at higher temperatures behavior as magnetic materials. Cobalt ferrites nanoparticles were charcterized by X-ray powder diffraction, small angle X-ray scattering e magnetization. Cobalt ferrites has not presented superparamagnetic behavior. For the synthesis of cobalt ferrites some parameters that are important to the process control were studied: calcination temperature, calcination time, heat rate. We have shown the relation among those parameters and the particle size and properties control to the cobalt ferrite nanoparticles.
10
Gonçalves, Nizomar de Sousa. „Utilização da água de coco em pó na preparação de nanopartículas de ferritas“. reponame:Repositório Institucional da UFC, 2007. http://www.repositorio.ufc.br/handle/riufc/9793.
Der volle Inhalt der QuelleAnnotation:
GONÇALVES, Nizomar de Sousa. Utilização da água de coco em pó na preparação de nanopartículas de ferritas. 2007. 46 f. Dissertação (Mestrado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2007.Submitted by Edvander Pires (edvanderpires@gmail.com) on 2014-11-13T22:17:28Z No. of bitstreams: 1 2007_dis_nsgoncalves.pdf: 1509521 bytes, checksum: 892d11d7fe93897c2f435078c8f4175a (MD5)
Approved for entry into archive by Edvander Pires(edvanderpires@gmail.com) on 2014-11-14T17:51:45Z (GMT) No. of bitstreams: 1 2007_dis_nsgoncalves.pdf: 1509521 bytes, checksum: 892d11d7fe93897c2f435078c8f4175a (MD5)
Made available in DSpace on 2014-11-14T17:51:45Z (GMT). No. of bitstreams: 1 2007_dis_nsgoncalves.pdf: 1509521 bytes, checksum: 892d11d7fe93897c2f435078c8f4175a (MD5) Previous issue date: 2007
The present work is dedicated to the studies of the preparation and characterization of the nickel ferrites and cobalt. These ferrites were synthesized by the sun-gel process in suspension of water of coconut lyophilized (ACP) manufactured in Cear´a. This synthesis method allowed to obtain in way efficient ferrite nanoparticles. The samples were treated for 4 hours at 400, 600, 800, 1000 and 1200 C. A preliminary study of the cobalt ferrite varying the concentration of the coconut water above your critical micelle concentration (8,3 mmol/l) it showed as that can influence in the quality of the nanoparticles. The Xray difraction (XRD), the Raman spectroscopy and Scanning Eletron Microscopy (SEM) were applied to study the dependence of the size of the nanoparticle of nickel ferrite with the temperature of the thermal treatment, and the correlation of your electrical properties and the results of M¨ossbauer spectroscopy with your morphologic characteristics. The cristalinity of the ferrites increases with the temperature of the thermal treatment. Measurements of the complex permitivity carried out in cavity resonators at 5,9 and 9,0 GHz have showed that your values of the real part decrease with the increase of the temperature of the thermal treatment (3,6 - 2,4), while the imaginary part stay low for more elevated temperatures of the thermal treatment (about 10−3). Measurements of complex impedance to lower frequencies (75 KHz to 30 MHz), have showed that it increases with the increase of the temperature of the thermal treatment. The results of M¨ossbauer spectroscopy showed that the ferrites presents a structure inverse spinel with the ions Ni2+ occupying the site B and the ions Fe3+ equally distributed in the sites A and and B. To temperatures of thermal treatment below 800 ºC, favored the presence in the grains of a phase Grain Boundary (greater condutivity) observed so much in the behavior of the electric properties as in the answers of the M¨ossbauer spectroscopy.
Este trabalho é dedicado aos estudos da preparação e caracterização das ferritas de níquel e cobalto. Estas ferritas foram sintetizadas pelo processo de sol-gel em suspensão de água de coco liofilizada (ACP) fabricada no Ceará. Este método de síntese permitiu obter de forma eficiente nanopartículas de ferritas. As amostras foram calcinadas durante 4 horas a 400, 600, 800, 1000 e 1200 °C. Um estudo preliminar da ferrita de cobalto variando a concentração da água de coco acima da sua concentração micelar crítica (8,3 mmol/litro) mostrou como isso pode influenciar na qualidade e na homogeneização das nanopartículas. A difração de raios-X (XRD), a espectroscopia Raman e a Microscopia Eletrônica de Varredura (SEM) foram aplicadas para estudar a dependência do tamanho da nanopartícula de ferrita de níquel com a temperatura do tratamento térmico, e a correlação de suas propriedades elétricas e os resultados de espectroscopia Mössbauer com as suas características morfológicas. A cristalinidade das ferritas aumenta com a temperatura do tratamento térmico. Medidas da permissividade complexa realizadas em cavidades ressonantes a 5,9 e 9,0 GHz mostraram que seus valores da parte real decrescem com o aumento da temperatura do tratamento térmico (3,6 - 2,4), enquanto os da parte imaginária permanecem baixos para as temperaturas mais altas do tratamento térmico (cerca de 10-3). Medidas de impedância complexa a frequências mais baixas (75 KHz a 30 MHz), mostraram que ela aumenta com o aumento da temperatura do tratamento térmico. Os resultados de espectroscopia Mössbauer mostraram que as ferritas apresentam uma estrutura espinélio inverso com os íons Ni2+ ocupando os sítios B e os íons Fe3+ distribuídos igualmente nos sítios A e B. Para temperaturas de tratamento térmico abaixo de 800°C favoreceram a presença nos grãos de uma fase mais condutora (Grain Boundary), observada tanto no comportamento das propriedades elétricas quanto nas respostas da espectroscopia Mössbauer.
Bücher zum Thema "Ferrites de cobalt"
1
Sehar, Fatima, und Zeeshan Mustafa. Synthesis and characterization of bismuth doped cobalt ferrite. LAP Lambert Academic Publishing, 2015.
Den vollen Inhalt der Quelle findenBuchteile zum Thema "Ferrites de cobalt"
1
Caldeira, Luis Eduardo. „Synthesis, Properties, and Applications of Spinel Cobalt Ferrites“. In Environmental Applications of Nanomaterials, 1–16. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-86822-2_1.
Der volle Inhalt der Quelle
2
Bhuvaneswari, M., und S. Sendhilnathan. „Preparation and Characterization of Cobalt Doped Mn-Zn Ferrites“. In Lecture Notes in Mechanical Engineering, 603–9. India: Springer India, 2012. http://dx.doi.org/10.1007/978-81-322-1007-8_55.
Der volle Inhalt der Quelle
3
Zhang, Xijun, Guoqian Wang, Xin Peng, Sujun Lu, Dalin Chen, Yutian Ma und Ailiang Chen. „Structural and Magnetic Properties of Rare Earth Lanthanum-Doped Cobalt Ferrites“. In The Minerals, Metals & Materials Series, 433–43. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-92388-4_39.
Der volle Inhalt der Quelle
4
Chandra, Kailash, Sonal Singhal und Sandeep Goyal. „Magnetic and Mössbauer spectral studies of nano crystalline cobalt substituted magnesium ferrites (MgxCo1 − xFe2O4)“. In ICAME 2007, 247–52. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-78697-9_28.
Der volle Inhalt der Quelle
5
Rao, G. S. N., O. F. Caltun, K. H. Rao, B. Parvatheeswara Rao, H. L. Wamocha und H. H. Hamdeh. „Influence of silicon and cobalt substitutions on magnetostriction coefficient of cobalt ferrite“. In ICAME 2007, 593–98. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-78697-9_80.
Der volle Inhalt der Quelle
6
Pileni, M. P., N. Moumen, I. Lisiecki, P. Bonville und P. Veillet. „Ferrofluid of Cobalt Ferrite Differing by Their Particle Sizes“. In Nanoparticles in Solids and Solutions, 325–63. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-015-8771-6_16.
Der volle Inhalt der Quelle
7
Rao, G. S. N., O. F. Caltun, K. H. Rao, B. Parvatheeswara Rao, Ajay Gupta, S. N. R. Rao und A. Mahesh Kumar. „Mössbauer and magnetic study of silicon substituted cobalt ferrite“. In ICAME 2007, 465–69. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-78697-9_60.
Der volle Inhalt der Quelle
8
Ibrahim, Amal M., Morsi M. Mahmoud und M. M. Abd El-Latif. „Microwave Synthesis of Cobalt-Ferrite Nano-Particles by Polyol Method“. In Ceramic Transactions Series, 17–26. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2010. http://dx.doi.org/10.1002/9780470930953.ch3.
Der volle Inhalt der Quelle
9
Morais, P. C., A. C. Oliveira, V. K. Garg, M. L. Silva, E. F. C. Alcantara, F. Q. Soares und D. Rabelo. „Synthesis, thermal treatment and characterization of cobalt ferrite-based nanocomposites“. In HFI/NQI 2007, 387–92. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-85320-6_60.
Der volle Inhalt der Quelle
10
Shankar, S., Vinita Tuli, S. Gaurav, O. P. Thakur und M. Jayasimhadri. „Variable Dielectric and Ferroelectric Properties in Size-Controlled Cobalt Ferrite“. In Springer Proceedings in Materials, 35–40. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-5971-3_4.
Der volle Inhalt der QuelleKonferenzberichte zum Thema "Ferrites de cobalt"
1
Pannaparayil, T., und S. Komarneni. „Synthesis and charcterization of ultrafine cobalt ferrites“. In International Magnetics Conference. IEEE, 1989. http://dx.doi.org/10.1109/intmag.1989.690371.
Der volle Inhalt der Quelle
2
Rao, G. S. N., S. Ananda Kumar, K. H. Rao, B. Parvatheeswara Rao, A. Gupta, O. Caltun, I. Dumitru und Cheol Gi Kim. „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.
Der volle Inhalt der Quelle
3
Sharma, Harish, Bharat Mishra und 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.
Der volle Inhalt der Quelle
4
Boss, Alan F. N., Antonio C. C. Migliano und 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.
Der volle Inhalt der Quelle
5
Kamran, Muhammad, Yasir Abbas, Tanveer Akhtar und Muhammad Anis-ur-Rehman. „Electrical Properties of Lanthanum Doped Cobalt Ferrite Nanoparticales“. In International Symposium on Advanced Materials. Switzerland: Trans Tech Publications Ltd, 2022. http://dx.doi.org/10.4028/p-5v3687.
Der volle Inhalt der QuelleAnnotation:
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.
6
Kumar, N., D. R. Sagar und 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.
Der volle Inhalt der Quelle
7
Venkateshwarlu, Ch, M. Prasad, G. Vinod, Y. Suresh Reddy, K. Rajashekar, B. Naresh, P. Ramesh, U. Dhasaratha, P. Neeraja und J. Laxman Naik. „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.
Der volle Inhalt der Quelle
8
Watawe, S. C., U. A. Bamne und 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.
Der volle Inhalt der Quelle
9
Parvatheeswara Rao, B., K. H. Rao, P. S. V. Subba Rao, S. Pallam Setty, N. S. Gajbhiye und 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.
Der volle Inhalt der Quelle
10
Burra, K. G., und 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.
Der volle Inhalt der QuelleAnnotation:
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.
Berichte der Organisationen zum Thema "Ferrites de cobalt"
1
Song, Sang-Hoon. Magnetic and magnetoelastic properties of M-substituted cobalt ferrites (M=Mn, Cr, Ga, Ge). Office of Scientific and Technical Information (OSTI), Dezember 2007. http://dx.doi.org/10.2172/1342575.
Der volle Inhalt der Quelle