Tesi sul tema "Ferrites (matériaux magnétiques) – Détérioration"
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Gallias, Jean-Louis. "Etude des caractéristiques physiques et chimiques de la liaison acier corrodé-pâte de ciment". Toulouse 3, 1992. http://www.theses.fr/1992TOU30131.
Testo completoHédin, Marc. "Sensibilité aux conditions initiales de l'évolution microstructurale de la ferrite d'aciers austéno-ferritiques vieillis dans le domaine 300-400°C". Rouen, 1998. http://www.theses.fr/1998ROUES080.
Testo completoNovy, Stéphane. "Mécanismes de vieillissement à très longue échéance des aciers inoxydables austénoferritiques". Rouen, 2009. http://www.theses.fr/2009ROUES039.
Testo completoEmbrittlement study of duplex stainless steels is a very important in order to predict the lifetime of primary circuits of nuclear power plant. Ferrite steels aged over 20 years, on-site, in laboratory and at different temperatures was analyzed by tomographic probe atom to assess the trend of aging of these materials with very long times. A more prospective work was also carried out, the aim was to model the decomposition of ferrite from austenitic-ferritic steels. The simulation of the decomposition of these steels are very complex, we initiated preliminary work in modelling the Fe-Cr alloys, because the decomposition of Fe and Cr in these steels is the main cause of their fragility. To validate the parameters used in simulation, an experimental study of the decomposition of an alloy Fe-20% at. Cr aged at 500 ° C was performed. This experimental study has shown that a non-classical germination (NCG) is involved in this alloy. The performed simulations on the same alloy at the same temperature, did not reproduce the progressive enrichment of precipitated phase α' (characteristic of NCG). The study of steels, aged over 20 years, has confirmed that the steel aged in laboratory are representative to steel aged in site ( T <350 ° C). Moreover, it has been shown that the Gphase (intermetallic precipitation at the interface α/α' phases) does not influence the embrittlement of the ferrite and the difference of thermo-mechanical treatment is not determinant of the variance decomposition observed in these steels
Renaux, Jeoffrey. "Ιnfluence de l'austénite et des impuretés sur le vieillissement thermique de la ferrite des aciers inοxydables austénο-ferritiques". Electronic Thesis or Diss., Normandie, 2024. http://www.theses.fr/2024NORMR026.
Testo completoAusteno-ferritic steels used in the design of various cast components (valves, pump bodies, etc.) in the primary circuit of second-generation nuclear power plants exhibit changes in their mechanical properties at service temperatures between 285°C and 325°C. These two-phase alloys, which combine ferrite and austenite, exhibit a microstructural hardening that occurs within the ferrite. This hardening is associated with two phase transformations, including, firstly, spinodal decomposition into an α phase rich in Fe and an α' phase rich in Cr, and secondly, the formation of a G phase rich in alloying elements Ni, Si, Mn, Mo. While austeno-ferritic steels containing Mo present a greater hardening than steels without Mo, the observation of a purely ferritic steel containing Mo, on the contrary, showed less hardening due to the absence of G phase precipitation. The aim of this study was to understand the influence of austenite on the aging of ferrite, which was the main hypothesis put forward to explain the reason for the lesser hardening of purely ferritic steel. To confront this hypothesis, the use of an electrochemical method allowed for the selective dissolution of austenite to obtain austenite-free ferrite, with the same composition, morphology, and thermo-mechanical history as the ferrite with austenite. The study by atom probe tomography of the microstructural evolution of these two ferrites, as well as that of a purely ferritic steel under aging conditions of 1,000 hours at 400°C, allowed for the investigation and understanding of the following points:- The results showed that the presence of austenite induces residual compressive stresses on the ferrite, which are not the cause of the enhanced aging of austeno-ferritic steels, as no significant difference in microstructure was observable between ferrites with and without austenite.- The characterization of the effect of the Cr/Ni composition gradient near the α/γ interfaces on the microstructural evolution of ferrite was conducted. The evolution of Cr and Ni concentrations towards the α/γ interfaces does not impact the spinodal decomposition but affects the formation of the G phase, with the main effect being a significant decrease in nanoparticle density towards the α/γ interfaces.- As residual stresses are not the cause of the difference in aging between purely ferritic and austeno-ferritic steels, the hypothesis of a chemical composition effect was considered. The results showed that the number density of G phase particles is strongly correlated with the impurity concentration in the ferrite. The absence of impurities in the ferritic alloy appears to explain the absence of G phase nanoparticles at the α/α’ interdomains and thus the lesser aging of the ferritic alloy
Vieille, Bertrand. "Modélisation de l’effet des contraintes sur le comportement magnétique des ferrites". Cachan, Ecole normale supérieure, 2007. http://tel.archives-ouvertes.fr/tel-00185947/fr/.
Testo completoThe effect of stress on the magnetic behaviour of ferrites has been investigated by the use of experiments (parallelepipedic samples submitted to compression and tensile stress, and toric samples submitted to compressive stress) and a multiscale model. The measurements allow us to estimate the magnetic and magnetostrictive behaviours of the ferrite. The numerical model is based upon three scales : the magnetic domain, the single crystal and the polycrystal. At the scale of the magnetic domain, a minimisation of the potential energy gives the direction of magnetisation under the combined effect of magnetic field, stress, and crystal orientation. At the scale of the single crystal, the volumetric fractions of domains of different orientations are computed from their respective energies through a constitutive equation (Boltzmann function). The polycrystalline behaviour is deduced from the behaviour of a sufficient number of grains thanks to an averaging operation. The model allows us to simulate the magnetic and magnetostrictive behaviours. Experimental and numerical results are in good accordance. The modelling of the magnetic behaviour under high frequency magnetic field conditions constitutes the final point to the work. It allows us to describe the effect of stress on the domain walls motion and gyromagnetism
Ourry, Laurence. "Relation structure-propriétés de matériaux hybrides magnétiques polymère-ferrites spinelles". Paris 7, 2014. http://www.theses.fr/2014PA077193.
Testo completoI 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
Konn-Martin, Anne-Marie. "Propriétés magnétiques des ferrites doux polycristallins en présence d'un champ magnétique polarisant". Brest, 1989. http://www.theses.fr/1989BRES2013.
Testo completoLe, Reste Christophe. "Etude de cellules de caractérisation de matériaux anisotropes ferrimagnétiques". Brest, 1995. http://www.theses.fr/1995BRES2005.
Testo completoLargeteau, Alain. "Élaboration, caractérisation et modélisation de céramiques magnétodiélectriques à couches d'arrêt". Bordeaux 1, 1990. https://tel.archives-ouvertes.fr/tel-00173432.
Testo completoTenant, Pierre. "Modélisation des ferrites doux dans le contexte de l’électronique de puissance". Lyon, INSA, 1995. http://www.theses.fr/1995ISAL0076.
Testo completo[Soft ferrites are the base material of magnetic components in power electronics. Therefore,they are submitted to specific operating conditions. Frequencies are ligh, peak flux density is distant from saturation and the waveforms of the flux are rarely sinusoidal. In this context, soft ferrites modelling needs to take into account complex phenomena such as hysteresis and eddy currents. We present a behavioural mode! specifically adapted to soft ferrites. This model takes into account both hysteresis and dynamic phenomena. In the specific environment of power electronics, this model shows a good ability to predict iron losses, magnetic characteristics and electrical values. Its main advantages are the few experimental data needed to identify its parameters, its excellent accuracy and its speed of execution. ]
Kester, Etienne. "Dynamique d'évolution à basse température des ferrites de cuivre nanométriques de structure spinelle. Corrélation avec leur distribution cationique et quelques propriétés physiques". Dijon, 1996. http://www.theses.fr/1996DIJOS054.
Testo completoRivalin, François. "Développement d'aciers pour gazoducs à haute limite d'élasticité et ténacité élevée : mécanique et mécanismes de la rupture ductile à grande vitesse". ENSMP, 1998. http://www.theses.fr/1998ENMP0816.
Testo completoLiorzou, Françoise. "Introduction de la subdivision en domaines dans la modélisation électromagnetique hyperfréquence des ferrites doux polycristallins : développement d'un modèle d'aimantation adapté". Brest, 1996. http://www.theses.fr/1996BRES2051.
Testo completoPichavant-Berthou, Karine. "Contribution à la modélisation des ferrites non saturés en hyperfréquences". Brest, 1996. http://www.theses.fr/1996BRES2036.
Testo completoKazemi, Shahab. "Etude du comportement anélastique des ferrites Mn-Zn". Lyon, INSA, 2005. http://theses.insa-lyon.fr/publication/2005ISAL0059/these.pdf.
Testo completoA series of Mn-Zn ferrite with general formula MnxZn1-xFe2O4 were prepared by a double sintering method. We fixed the content iron oxide (50% Mol) and varied the Zn content which replaces Mn. With these compositions, we can explore the influence of Zn2+ ions on the anelastic properties. Shear modulus G and internal friction Q-1 in polycrystalline manganese-zinc ferrite have been investigated at low frequencies as a function of temperature, by using a torsion inverted pendulum. From the modulus curves as the temperature of the specimen is increased the shear/Young's modulus initially decrease, attain a minimum value (Tk) and thereafter increase up to the Curie point (TC). Three internal friction peaks R1, R2 and R3 are observed on the curves of internal friction versus temperature. The peak R1 in ferrimagnetic state is discussed in interaction of domain walls with point defects. The peak R2 below the Curie temperature is attributed to viscous motion of domain walls. The peak R3 could be ascribed to the exchange of cations and their vacancies, and clustering Mn3+ ions
Amilain-Basset, Karine. "Etude de l'évolution de la composition superficielle d'oxydes mixtes lors de leur oxydation". Dijon, 2000. http://www.theses.fr/2000DIJOS066.
Testo completoLe, Traon Pierre. "Etude théorique et expérimentale de structures microruban à ferrite pour des applications de puissance". Brest, 1990. http://www.theses.fr/1990BRES2018.
Testo completoRomero, de la Osa Marc. "Modélisation de la fissuration lente d'une céramique technique de type ferrite". Lyon, INSA, 2009. http://theses.insa-lyon.fr/publication/2009ISAL0050/these.pdf.
Testo completoAlthough less studied, iron oxyde ferrites, like most ceramic materials are sensitive to delayed fracture. The slow crack growth (SCG) mechanism is characterised by a rising crack velocity with applied loading and also with temperature and humidity content. In addition, SCG is noticeably sensitive to microstructural effects as the variation of the grain size, and also influenced by the presence of some porosity at triple junctions. The ferrites under consideration in this study exhibit a heterogeneous microstructure with regions of variable grain size, and abundant porosities. Such a microstructure results in noticeable scattering in the measurements of the V-K characteristics from sample to sample, so that estimating the material's lifetime is not reliable. Thus,the development of a model for SCG and computational analyses are necessary to gain insight on the influence of the microstructure on the delayed rupture and ultimately to predict the material's durability. We have developed a local description of SCG, at the lengthscale of the microstructure. Within a cohesive zone methodology and based on available physics and on recent atomistic results, we propose a viscoplastic cohesive model that mimics the reaction-rupture mechanism underlying failure. The description is shown able to capture variations in the V-K predictions in agreement with the observations. From the simulations of intergranular failure under static fatigue, we observe a discontinuous crack advance in time, with different crack velocities depending on the local crack path. The crossing of the triple junction slows down crack propagation, and ultimately governs the average crack velocity. We evidence that account for the initial stresses originating from the process's cooling is necessary to predict an influence of the variation of the grain size in agreement with the observations. Simulation show that porosity at triple junctions are benefical for crack propagation resistance
Devillers-Guerville, Lydia. "Rupture d'aciers inoxydables austéno-ferritiques moules, fragilises par vieillissement à 350-400c : aspects microstructuraux - simulation numérique de la dispersion et des effets d’échelle". ENSMP, 1998. http://www.theses.fr/1998ENMP0837.
Testo completoBayard, Bernard. "Contribution au développement de composants passifs magnétiques pour l'électronique hyperfréquence". Saint-Etienne, 2000. http://www.theses.fr/2000STET4019.
Testo completoRecently, there has been a growing need for microwave integrated circuits in telecommunication applications. The main purpose of this work is to lay the foundations for the design of microwave magnetic passive components such as insulators and circulators which use the gyromagnetic properties of ferrites. . . [etc. ]
Zegadi, Lakhdar. "Introduction de la température dans un modèle comportemental pour ferrites doux". Lyon, INSA, 1995. http://www.theses.fr/1996ISAL0026.
Testo completo[This work concerns the modeling of high frequency magnetic material and magnetic components used in power electronics. We aim to introduce temperature in a behavior model elaborated in CEGELY. This model especially suitable for soft ferrites take into account the static (hysteresis) and dynamically (eddy currents) phenomena. We have firstly studied the temperature effect on some magnetic characteristics of soft ferrites (saturation flux density, remnant induction, coercive and losses) then we have established empirical laws to identify the temperature dependence of these characteristics. We have introduce these laws in a behavior model. The model at fixed temperature is establish at the temperature of minimum loss (near 80°C because the transformer core is usually operated at these temperature). The parameters of the model are calculated at this temperature and taken independent of temperature. To describe temperature dependence of magnetic and electrical characteristics, we introduce two law on the static model. The complete model requires few material data for entire simulation. It gives bath iron lasses and waveforms in a wide range of temperature (40°C – 140°C), in the classical operating conditions of soft ferrite in power electronics. The computing time is less than ten seconds in a PC. ]
Melon, Christian. "Contribution à la modélisation des ferrites par la méthode des différences finies en régime transitoire : applications à l'étude des dispositifs microondes à ferrites". Limoges, 1996. http://www.theses.fr/1996LIMO0037.
Testo completoBonte, Jean-Jacques. "Contribution à la caractérisation électromagnétique de nouveaux matériaux dans une large bande de fréquences". Lille 1, 1990. http://www.theses.fr/1990LIL10119.
Testo completoLorimier, Johan. "Problématique des valences mixtes dans les ferrites nanométriques : possibilités offertes par la diffraction résonnante des rayons X". Dijon, 2001. http://www.theses.fr/2001DIJOS004.
Testo completoVillette, Carole. "Elaboration et caractérisation de fines particules de ferrites spinelles substitués (cuivre/cobalt/manganèse) : relations structure-propriétés magnétiques". Toulouse 3, 1995. http://www.theses.fr/1995TOU30286.
Testo completoZemirli, Mourad. "Propriétés inhomogènes de verres de spin réentrants, étudiés par spectrométrie Mössbauer : zn::(x)mg::(1-x)fe::(2)o::(4) (x = 0.6 a 0.9)". Le Mans, 1988. http://www.theses.fr/1988LEMA1004.
Testo completoMillot, Nadine. "Synthèse et propriétés de ferrites nanométriques : influence de la taille des grains et de la nature de la surface sur les propriétés structurales et magnétiques de ferrites de titane synthétisés par chimie douce et mécanosynthèse". Dijon, 1998. http://www.theses.fr/1998DIJOS053.
Testo completoAbakar, Mahamat Tahir. "Modélisation thermique des composants magnétiques utilisés en électronique de puissance". Lyon, INSA, 2003. http://theses.insa-lyon.fr/publication/2003ISAL0049/these.pdf.
Testo completoThe subject of our work concerns the thermal modelling of magnetic component used in power electronic. The model will have to satisfy the following constraints: - easy to build, easy to use - accurate model (+/-a fawn degrees). This work presents the development of a model in which the temperature of both magnetic material and windings ( copper and magnetic material ) is computed from the measure of losses ( copper losses and core }osses ). The model is composed of many elements which represent thermal exchanges in the component. The chosen method is the nodal method. To validate the model, sorne measurements h~ve been made. A thermal measure equipment has been developed. To validate our results, a comparison between simulated and measured temperatures has carried out, in order to validate our results
Ajroudi, LIlia. "Ferrites de cobalt nanostructurés ; élaboration, caractérisation, propriétés catalytiques, électriques et magnétiques". Electronic Thesis or Diss., Toulon, 2011. http://www.theses.fr/2011TOUL0017.
Testo completoThis 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
Jeannot, Cécile. "Synthèse et étude des propriétés structurales, magnétiques et chimiques de ferrates (IV), (V) et (VI) alcalins". Nancy 1, 2000. http://www.theses.fr/2000NAN10132.
Testo completoSynthesis, magnetic and chemical properties of alkaline ferrate (IV), (V) and (VI) have been investigated. The first part of this report is devoted to the study of the K-Fe -O system. After a bibliographical review of potassium oxides, the syntheses carried out by. , solid-state reaction between KO2 and an iron oxide have showed that it is possible to synthesise K2FeO4 at 350°C under atmospheric pressure of oxygen, or at 450°C in a sealed "Pyrex" tube. Ferrate (V) was only detected in some of mixtures, the oxidation step (IV) was never found. The study of the Na-Fe -O system lead to evidence the existence of sodium ferrate (IV) Na4FeO4. This phase crystallises in the triclinic system and belong to the Na4MO4 series (M = transition element). In this compound, iron is in a tetrahedral site. Na4FeO4 is aritiferromagnetic below 16 K. The study of the magnetic structure shows that the exchange interactions may form via Fe-O-Na-O-Fe superexchange ways. Na4FeO4 is the first example of material which stabilises Fe (IV) in a tetrahedral site. With our experimental conditions, it was not possible to stabilise the oxidation step (VI), whereas a ferrate (V) could be detected while operating in presence of oxygen generated in-situ in the sealed Pyrex tube or in presence of hydroxide. The study of the Na-K-Fe-O system evidenced the existence of the oxidation step (V) in a compound with the K2NaFeO4 formula. Isotypic with K2NaMnO4, iron (V) is tetrahedrally co-ordinated. Paramagnetic until 6 K, the Mössbauer parameters ofthis Fe (V) high spin have been specified for the first time. The optimization of the synthesis of ferrate (VI) by electrochemical way is also described. Ferrate (IV) and (V) di sproportionate to give Fe (VI) and Fe (III). The last part of this work is devoted to the chemical propel1ies of ferrate (VI) which has potential industrial applications in the field of energy and environment
Grimal, Virginie. "Effets magnétiques et magnéto-élastiques en fréquencees dans les ferrites de Ni-Zn non stoechiométriques". Tours, 2005. http://www.theses.fr/2005TOUR4020.
Testo completoConcerning microwave applications of spinel ferrite, it appears a lack of knowledge in the field of hyperfrequency magneto-elastic effect. In this work, we want to evaluate the fabrication parameters effects (density, grain size, influence of the stoichiometry in iron, nickel and zinc) on the magnetic and magneto-elastic sensibility properties. Compositions studied were Ni0,5Zn0,5Fe2O4 and Ni0,4Zn0,6Fe2O4. Those materials were prepared through a classical ceramic way. This work shows that microstructure doesn't influence the sensitivity to stress, contrary to diverging stoichiometries which influence the crystalline lattice dimensions, and that, in another way for the two families. All the microstructural and magnetic properties obtained, have allowed establishing an ionic model joining the stress due to the lattice deformation and applied mechanical stress. A linear law between Curie temperature and lattice parameter was established allowing linking them with the exchange energy
Presmanes, Lionel. "Couches minces de ferrites mixtes de cobalt-manganèse et de cobaltites mixtes de fer-manganèse pour l'enregistrement magnéto-optique". Toulouse 3, 1995. http://www.theses.fr/1995TOU30162.
Testo completoGuinot, Dominique. "Recherche des paramètres physico-chimiques qui déterminent les propriétés mécaniques des céramiques de ferrite doux". Dijon, 1990. http://www.theses.fr/1990DIJOS023.
Testo completoOuahab, Rozane. "Comportement des aciers bainitiques à différentes températures : étude de la cémentite aux grands instruments". Paris, ENSAM, 2012. https://pastel.archives-ouvertes.fr/tel-01513053.
Testo completoSarda, Christian. "Contribution à l'étude de l'hexaferrite de baryum et des ferrites spinelles dopés au baryum : application à l'enregistrement magnétique". Toulouse 3, 1990. http://www.theses.fr/1990TOU30085.
Testo completoBeji, Zyed. "Synthèse par chimie douce et caractérisation de poudres et de films nanocristallins de ferrites mixtes de Ni - Zn : études des propriétés magnétiques statiques". Paris 7, 2008. http://www.theses.fr/2008PA077203.
Testo completoNi-Zn soft ferrite thin films are promising materials for many applications in the hyperfrequency field. The preparation of nanocristalline films based on these materials and the comprehension of their static magnetic properties related to their structure and microstructure are primordial to control their dynamic magnetic properties and consequently, to integrale them, in an optimized way, as miniaturized devices. Ni₁₋xZnxFe₂O₄ powder and films have been prepared by the polyol method. Synthesis optimization allowed us to have fine and monodispersed nanoparticles. Films of micrometric thickness were obtained as well. Nanocristalline film structure was confirmed by X ray diffraction and also by transmission electronic microscopy. EXAFS and Mössbauer experiments conducted on the as-produced powders and films show that their structure is different from the thermodynamically stable one. Magnetic studies of the powder and the Ni ₁₋xZnxFe₂O₄ films showed that they present a superparamagnetic behaviour at room temperature. While powder magnetization was relatively high and close to bulk materials, film magnetization was low. This behavior was due to the film densification with interface formation between the nanocristals (such as grain boundaries) and also to the installation of cooperative phenomena. Our study proved that the thermal treatment does not take part in the improvement of the film magnetic properties
Hallynck, Sylvain. "Elaboration et caractérisations de composites chargés en ferrite spinelle à morphologie contrôlée pour utilisations micro-ondes". Université Louis Pasteur (Strasbourg) (1971-2008), 2005. https://publication-theses.unistra.fr/public/theses_doctorat/2005/HALLYNCK_Sylvain_2005.pdf.
Testo completoIn this work, the dynamic electromagnetic properties of composite materials loaded with nickel-zinc spinel ferrite platelets (Ni1-xZnxFe2O4) were studied. Firstly the synthesis of the ferrite platelets has been developed. It is carried out in two stages. Single crystal hematite (-Fe2O3) platelets are initially obtained by hydrothermal treatment. It is possible to control their diameter between 30 and 300 µm. In the second step, these particles undergo a topotactic transformation into spinel ferrite by molten salt reaction. The so obtained platelets are polycrystalline and textured. The size of the crystallites which compose them can be increased by rising the reaction temperature from 1000 to 1200°C. In a second part, fine composite sheets (250 µm) are obtained by tape casting. Two techniques were developed. The first one makes it possible to work out composites at variable load factor thanks to the solidification of polyvinylbutyral by solvent evaporation. The other one is based on in-situ polymerization of butylméthacrylate. Castings were also carried out under magnetic field in order to improve the orientation of the particles. Quantitative analyses show the texturing effect of this field and the improvement of the orientation with the increase in the size of the platelets used as load. Finally, the dynamic permeability and permittivity of the composites were measured in single coil and coaxial line. We have shown the importance of the load morphology. Platelets make it possible to reach higher permeability values at lower frequency than an equivalent load with spheroid form. All in all, the increase in the size of the platelets or of the crystallites which compose them and the improvement of the texture of the composites make it possible to obtain higher values of permeability at lower frequency
Ajroudi, LIlia. "Ferrites de cobalt nanostructurés ; élaboration, caractérisation, propriétés catalytiques, électriques et magnétiques". Thesis, Toulon, 2011. http://www.theses.fr/2011TOUL0017/document.
Testo completoThis 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
Bui, ngoc Hai. "Modélisation µPEEC : représentation des matériaux magnétiques par des courants de surface. Application aux noyaux ferrites 2D". Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00737995.
Testo completoBui, Bgoc Hai. "Modélisation µPEEC : représentation des matériaux magnétiques par des courants de surface. Application aux noyaux ferrites 2D". Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENT007/document.
Testo completoThe aim of this thesis is to implement the method μPEEC to assess, without using simulations or measurements, the reluctance of magnetic circuits and simple 2D to predict their behavior from electromagnetic design phases . It's just asking the field created by a blade straight conductor placed in a round window or rectangular magnetic circuit with or without an air gap. This study is part of a larger research aimed at developing the equivalent circuit of transformers, before prototyping to optimize these components in their applications. Before reaching this goal, several steps were taken gradually, with the help of analytical solutions and finite element simulations to validate our approaches
Rudenko, Vasyl’ Viktorovitch. "Effets magnétoacoustiques paramétriques dans les matériaux magnétiques diélectriques et composites". Ecole Centrale de Lille, 2007. http://tel.archives-ouvertes.fr/index.php?view_this_doc=tel-00291549&extended_view=1&version=1&halsid=rvolvpnito1r5t694auconrvs5.
Testo completoParametric interaction in active magnetoacoustic materials of various composition and structures is studied experimentally. Influence of composition of nickel-based polycrystalline ferrite on sensitivity of sound velocities to DC and RF magnetic field is considered. Maximum magnetoelastic coupling 59% and magnetic sensitivity of shear wave velocity 100%/kOe were found for composition Fe2,026Ni0,95Co0,024О4. In the testing as an active medium for parametric wave phase conjugation this composition demonstrated extraordinary gain increment 4. 5 μs-1. Original amplitude-phase pulse (APP) method was elaborated and applied for studies of parametric sensitivity of perspective active materials with low (≈9 MRa) acoustic impedance: Terfenol-D based composite and porous nickel ferrite. Sensitivity of sound velocity to AC magnetic field is found as 4. 39%/kOe and 3. 39%/kOe in the composite and porous ferrite respectively. The new parametric acoustic phenomenon of three-phonon bound excitation is observed in “easy plane” antiferromagnetic crystal α-Fe2O3 under transversal AC magnetic pumping. Sub-threshold and supercritical modes of the three-phonon excitations were studied by the APP method and described theoretically. The specific feature of the supercritical mode is forming of singularity in a finite pumping duration. Singularity is stabilized by intrinsic nonlinearity in the phonon system
Briney, Emmanuel. "Contribution à l'intégration d'un circulateur HF : Caractérisations magnétiques de couches de ferrite". Limoges, 2002. http://www.theses.fr/2002LIMO0023.
Testo completoThe goal of this work is to contribute to the elaboration of a ferrite integrated circulator working in V band (60 - 70 GHz). My first work was to diminish the cracks which appear in barium ferrite films deposited on silicon (100) substrates. For this purpose, i have realized metallic films made of titanium, gold or copper on silicon prior to the ferrite deposition. They permit to adapt the stress between ferrite films and silicon and also constitute the circulator ground plane. We have chosen the magnetron sputtering technique to deposit these metallic films. To evaluate the barium ferrite films quality, i have developed a new characterization method which permits us to determine the gyromagnetic linewidth. It is based upon the ferrite absorption near the gyrotropic frequency in a metal cylindrical cavity at 56. 7 GHz. Tests on oriented bulk strontium hexaferrite have demonstrated its efficiency
Andriamanjato, Razafimahazo M. "Contribution à l'étude des structures rectangulaires à ferrite : applications aux déphaseurs et aux filtres à commande magnétique". Toulouse, INPT, 1992. http://www.theses.fr/1992INPT097H.
Testo completoBenevent, Evangéline. "Contribution à l’étude et à la réalisation d’un circulateur hyperfréquence à couche magnétique dans la bande 40-50 GHz". Saint-Etienne, 2006. http://www.theses.fr/2006STET4004.
Testo completoThe passive components such as circulators use the ferrites’ magnetic properties. As they use bulk ferrites and permanent magnets, they can be of large sizes. If a preferential crystalline orientation of hard magnetic thin film (like barium hexagonal ferrite thin film) were obtained, the development of self-polarized and miniaturized planar circulators could be possible. The goal of this project is to design and to manufacture a miniaturized circulator with magnetic thin film operating at innovative frequencies in the 40-50 GHz frequency band. The mass-manufacturing process must enable the technological transfer from the DIOM laboratory to the industry. A state of art led to choose a coplanar configuration. Indeed, this configuration presents the advantage of reducing the number of technological steps for the circulator’s manufacture – and consequently the production costs – as well as to facilitate the interconnection with some other microwave components. This is the RF sputtering deposition that was adopted to manufacture the barium hexagonal ferrite thin films : these are 10 µm thick and have good physico-chemical properties. The design and S parameters calculation are based in the theoretical results obtained from a stripline structure. Then these results are transposed to the coplanar one. The analytical study is completed by numerical studies made with the software Ansoft HFSS. Parametric studies enable to define the many geometric parameters of a coplanar circulator and to optimize the component’s performances. Some series of prototypes are manufactured and, afterwards, characterized by the means of a probe tester and a vector network analyser. The first experimental results show that the insertion losses are too high. The experimental validation of the functioning of magnetic thin film coplanar circulator could not be possible without the addition of a matched termination on the third port of the circulator. For the moment, the S parameters measurement is only possible between 2 ports. The optimization of the component’s performances will be possible thanks to the improvement of the barium hexagonal ferrite analytical modelling and by getting the preferential crystalline orientation, the increase in conductor’s thickness, the manufacture of a matched termination and/or the use of a triangular configuration
Ahamada, Baroini. "Réalisation d'un imageur magnétique multi-éléments micro-intégrés à base de magnétorésistances anisotropes". Cachan, Ecole normale supérieure, 2003. http://www.theses.fr/2003DENS0034.
Testo completoLe, Houé Valérie. "Application des cristaux liquides et des ferrites pour la réalisation de dispositifs agiles en fréquence". Brest, 1999. http://www.theses.fr/1999BRES2015.
Testo completoRudenko, Vasyl'. "Effets magnétoacoustiques paramétriques dans les matériaux magnétiques diélectriques et composites". Phd thesis, Ecole Centrale de Lille, 2007. http://tel.archives-ouvertes.fr/tel-00291549.
Testo completoL'influence de la composition des ferrites poly-cristallines à base de nickel sur les sensibilités des vitesses acoustiques aux champs magnétiques DC et RF sont considérées. Un couplage magnéto-élastique maximum de 59% et une sensibilité au champ magnétique de la vitesse des ondes transversales de 100%/kOe ont été trouvées pour la composition Fe2,026Ni0,95Co0,024О4. En utilisation comme milieu actif pour conjugaison de phase paramétrique, cette composition a démontré un incrément d'amplification extraordinaire de 4.5 μs-1.
Une méthode impulsionnelle amplitude-phase (IAP) originale a été élaborée et appliquée à l'étude de la sensibilité paramétrique de matériaux actifs intéressants pour les perspectives possédant une faible impédance acoustique (≈9 MRa): composites à base de Terfenol-D et ferrites poreuses de nickel. Les sensibilités de la vitesse acoustique au champ magnétique AC trouvées étaient de 4.39%/kOe et 3.39%/kOe dans le composite et la ferrite poreuse respectivement.
Un nouveau phénomène paramétrique acoustique d'excitation de trois phonons liésa été observé dans les cristaux antiferromagnétiques de type “plan-facile” α-Fe2O3 sous pompage magnétique transversal AC. Les modes sous-critiques et super-critiques de ces excitations à trios phonons ont été étudiés par la méthode IAP et décrits théoriquement. La particularité du mode super-critique est la formation d'une singularité pour une durée de pompage finie. Cette singularité est stabilisée par la nonlinéarité intrinsèque du système de phonon.
Boucetta, My Ahmed. "Contribution au calcul par éléments finis des pertes dans les ferrites". Lyon 1, 1994. http://www.theses.fr/1994LYO10117.
Testo completoChassaing, Isabelle. "Elaboration, caractérisation de fines particules et de couches minces de ferrites spinelles lacunaires cobalt-manganèse en vue de leur application à l'enregistrement magnéto-optique". Toulouse 3, 1993. http://www.theses.fr/1993TOU30094.
Testo completoEl, Harrous Abderrahim. "Le suivi en temps ŕéel de la transformation d'un matériau sous champ microonde". Toulouse, INPT, 1998. http://www.theses.fr/1998INPT027H.
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