Dissertations / Theses on the topic 'Matériaux composites magnétiques'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Matériaux composites magnétiques.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
Talbot, Philippe. "Introduction à l'étude des matériaux magnétiques composites." Brest, 1993. http://www.theses.fr/1993BRES2010.
Full textRudenko, 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.
Full textL'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.
Galicia, Alberto. "Matériaux composites : association de gels polymères et de nanoparticules magnétiques." Paris 6, 2003. http://www.theses.fr/2003PA066377.
Full textRudenko, 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.
Full textParametric 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
Dudek, Christophe. "Étude de matériaux hyperfréquences innovants : des microfils nanocristallisés aux composites magnétiques artificiels." Tours, 2006. http://www.theses.fr/2006TOUR4011.
Full textThis thesis concerns the development of new concepts in the microwave's magnetic materials field. Based on a multiple approach of the dynamic permeability, several attempts have been carried out. On the one hand, the study of nanocrystallized ferromagnetic glass-coated microwires has led, for the first time, to significant permeability levels up to 4 GHz at 350°C. On the other hand, a new type of metamaterial made of ferromagnetic core combined with copper helices has exhibited a large band microwave permeability. Eventually, the analysis of the magnetic response of magnets as part of mechanical systems has evidenced the concept of vibrating inductor in a magnetic field. This new technology seems to offer great potential gains
Cyr, Charles. "Modélisation et caractérisation des matériaux magnétiques composites doux utilisés dans les machines électriques." Phd thesis, Université Laval, 2007. http://pastel.archives-ouvertes.fr/pastel-00003791.
Full textFang, Weiqing. "Elaboration de matériaux composites nanofils magnétiques/polymères pour la fabrication d'aimants permanents." Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-01070641.
Full textChevalier, Alexis. "Etude expérimentale, élaboration et modélisation de matériaux composites à base de poudres magnétiques douces." Brest, 1998. https://tel.archives-ouvertes.fr/tel-00484041.
Full textMorin, Victor. "Elaboration de composites multiférroïque et caractérisation de l'effet magnétoélectrique." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLN030/document.
Full textThe magnetoelctric (ME) response consists in the modification of the electric polarization by an applied magnetic field (direct effect) or the modification of the magnetic polarization by an applied electric field (inverse effect). Intrinsic multiferroics are rather uncommon and the effect is often weak at room temperature. An alternative route to achieve ME effect, consists in using magnetostrictive and piezoelectric materials and coupling the two phases by mechanical stress. We draw (theoretically and experimentally) some material characteristics to achieve an importantME effect, which justify the use of ferrite and PZT. We describe the production process of the two studied connectivity schemes (stack of layers or inclusion of a phase in another). We focus on the sintering by Spark Plasma Sintering as a potential improvement of the mecanical bonding. We devoted a part of our work on multilayer composite and showed the importance of some factors such as the demagnetizing effect or the symmetry of the structure. We introduce a current sensor prototype suitable for electrical engineering application. We showed its good linearity and sensitivity but also some effects of its bandwidth
Deprot, Sylvie. "Élaboration de micro-filaments composites : des caractéristiques physico-chimiques aux propriétés magnétiques." Tours, 2003. http://www.theses.fr/2003TOUR4004.
Full textAdvances in the elaboration, understanding and engineering of the static and dynamic magnetic properties of amorphous glass-coated ferromagnetic microwires are presented. The control of the geometric characteristics of the microwires has been obtained through a careful parametric elaboration process study. That led to propose innovative modifications of the production apparatus to reach a continuous process. The magnetic anisotropy of these wires is mainly due to a magneto-elastic behavior. This has been evidenced through the experimental demonstration of the effects of the alloy composition and of the stress state of the ferromagnetic core on the static magnetic properties. Microwave properties of the ferromagnetic microwires were studied through their permeability spectra. They were described using a gyromagnetic model taking into account skin effect. The understanding of their static magnetic properties led to the engineering of the dynamic properties of the ferromagnetic microwires
Tchangoulian, Ardaches. "Utilisation de matériaux composites magnétiques à nanoparticules pour la réalisation de composants passifs non réciproques micro-ondes." Thesis, Saint-Etienne, 2014. http://www.theses.fr/2014STET4016/document.
Full textIn telecommunications systems, many studies have been undertaken to integrate non-reciprocal passive components. The proper functioning of circulators often requires large and heavy magnets that ensure a uniform orientation of the magnetic moments of the ferrite material. To work towards the integration and miniaturization of circulators, nanotechnology can offer interesting solutions. The aim of this thesis was to develop a self-biased coplanar circulator. The approach is based on the production of composite substrates "ferrimagnetic nanowire." It consists in a magnetophoresis or a dip-coating deposition of cobalt ferrite nanoparticles in porous alumina membranes and orienting them in a magnetic field uniformly. Magnetic composite substrates were made from CoFe2O4 nanoparticles dispersed in a matrix of silica sol-gel using the dip-coating technique with and without an applied magnetic field. Many studies have been made to study the magnetic and dielectric behavior of these substrates: VSM, spectral polarimetry, MFM and others. The hysteresis loops show a strong difference in the values of coercive fields (μ0Hc) and persistent (Mr / Ms) if, during the fabrication, a magnetic field is applied or not, therefore showing the orientation (or not) of nanoparticles. This nano-composite is an interesting candidate for the fabrication of circulators even if the concentration and the particle orientation are insufficient. Circulators were designed, modeled and simulated using the HFSS software. Following the interesting results of simulation; a first prototype was fabricated and characterized at high frequencies. The measurement results showed a circulation phenomenon, which is very low due to the small percentage of magnetic nanoparticles in the composite and their imperfect orientation. Technological barriers have been clearly identified and do not allow for the time to achieve an operational circulator
Camus, Olivier. "Modélisation des propriétés magnétiques de matériaux ferrite et de composites à base de ferrite absorbant le rayonnement électromagnétique." Vandoeuvre-les-Nancy, INPL, 1996. http://www.theses.fr/1996INPL022N.
Full textHallynck, 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.
Full textIn 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
Lapointe, Philippe. "Développement d'un composite magnétique doux avec revêtement de ferrite nanométrique." Master's thesis, Université Laval, 2010. http://hdl.handle.net/20.500.11794/21343.
Full textElectric motors, transformers, electromagnets and many other electric devices require materials that can provide a path for magnetic field lines while minimizing losses that they generate. Materials used for these applications are called soft magnetic materials. One way to minimize losses in such materials is to increase their resistivity. In order to do so, highly resistive materials are coupled with ferromagnetic materials. These are called soft magnetic composites. For more than one hundred years, the most common type of soft magnetic composite was made by stacking sheets of rolled iron separated by a thin layer of insulating materials. These were very simple and efficient but also had their share of drawbacks. During the last decades, a new technique based on powder metallurgy was developed. It consists in coating iron particles with an isolating material prior to compaction. This type of materials can be highly resistive. The objective of this project was to develop a soft magnetic composite using metal powders in which the insulating materials would be nanometric NiZn ferrite. Two different techniques were studied in order to achieve this goal. The first one consists in coating iron powders with NiZn ferrite using ferrite plating and the second one consists adding nanoparticles to iron powder. The results obtained throughout this study showed that these two techniques could certainly be used to develop metal powder based soft magnetic composites. More specifically, magnetic weight losses of 11,9 W/kg and 93 W/kg were obtained at 60 Hz and 400 Hz respectively for components prepared using the ferrite plating technique while losses of 13,5 W/kg and 137 W/kg were obtained at 60 Hz and 400 Hz respectively for components prepared by adding ferrite nanoparticles.
Sahraoui, Yosra. "Électrodes modifiées par des matériaux composites fonctionnalisés pour application capteurs et biocapteurs." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10071.
Full textThe objective of the study consists in the development of modified electrodes, based on nanomaterials for electroanalytical applications. In this aim, different methods of modification of the electrodes have been proposed: chemical functionalization, adsorption and electropolymerization, using the electrostatic and covalent interactions between electrode surfaces and nanomaterials (magnetic nanoparticles, gold nanoparticles, polyoxometallates and carbon nanotubes). The prepared modified electrodes have allowed the obtaining of detection devices (sensors and biosensors) characterized for their interesting analytical performances in terms of sensitivity and detection limit. Urea biosensors, based on semi-conducting electrodes, functionalized with magnetic nanoparticles coated with urease enzyme, have allowed the sensitive detection of urea. Chemical sensors for the sensitive detection of nitrite ion have been obtained through functionalization of glassy carbon electrodes and boron doped diamond electrodes with polyoxometallates. The combination of both types of nanomaterials (carbon nanotubes and hybrid polyoxometallates) have allowed the obtaining of an original structure that presents conductive properties of nanotubes and electrocatalytic properties of polyoxometallates. These original structures have allowed the fabrication of enzymatic biosensors with a high sensitivity for the detection of glucose and catechol
Neige, Julien. "Elaboration, caractérisation et modélisation d'un composite à base de pétales ferromagnétiques pour des appications hyperfréquences." Thesis, Tours, 2013. http://www.theses.fr/2013TOUR4040/document.
Full textResearch on new microwave absorbing materials has become a major issue with the growing development of wireless communications and, accordingly, the need to shield effectively from the electromagnetic "pollution" (protection of equipment and persons).In this manuscript, we focus on an anisotropic composite consisting of aligned ferromagnetic flakes embedded in a nonmagnetic matrix. There is currently a growing interest for this kind of composite in the community due to the many benefits it provides (adjustment of the absorption band as a function of both nature and flakes aspect ratio, thin composite coating). The scope of this study was deliberately relatively large in order to get an overview of issues related to these flakes composites at several scales. At first, an original study was conducted on a single flake. After preliminary work on the development of flakes and their morphological properties, static and dynamic magnetic characterizations were performed on a single flake. The permeability spectrum obtained shows three resonances. A complementary study on objects of the same size, produced by PVD and structured by FIB has, by analogy, attributed these three resonances to respectively, domains, domains wall and an embedded vortex (vortex linked with several domains walls).In a second step, the evolution of the shorted microstrip permeametry technique made possible the detailed and complete characterization of thick composites with or without a static magnetic field applied in different directions and for various pumping directions. This confirmed the origin of the different resonances despite the characteristic structural disorder of composite media.Finally, an applicative study was conducted establishing the strong link between the microstructure (porosity, particle size and orientation) and the electromagnetic properties of the composite. Taking into consideration both elaboration and performance point of views, the industrial potential of this composite has been demonstrated
Schoenstein, Frédéric. "Elaboration et caractérisation de composites à base de couches minces ferromagnétiques pour les applications hyperfréquences." Orléans, 2003. http://www.theses.fr/2003ORLE2021.
Full textAlhassoun, Yasser. "Étude et mise en oeuvre de machines à aimantation induite fonctionnant à haute vitesse." Toulouse, INPT, 2005. https://hal.science/tel-04587281.
Full textActually, electromechanical machines are characterized by their low cost and reducedmaintenance. Therefore, new types of magnetic materials such as soft magnetic composites (SMC), have to be considered not only for multiple applications (small motors for automotive) for cost reduction, but also when considering other special requirements such as high speed drive (aircraft and space applications). Our report of thesis is articulated around four chapters: The first chapter show the various types of magnetic interactions used in the electromagnetic actuators. The second chapter is devoted to the modelling of the induced magnetic machines by analytical resolution of equations of the field in two dimensions. The third chapter presents the four configurations prototypes of switched reluctance machine which mix the exploitation of laminated materials and the soft magnetic powders. The fourth chapter discusses the critical conditions of this machines operating at high speed. We conclude, insisting on the efforts carried out in term of analytical modelling of the induced magnetization machines for their dimensions and exploited in this same structure, the soft magnetic composite materials. The results show the potential of soft magnetic powders when considering in particular the high frequency losses and their ability to favour the heat dissipation in this structure
Colis, Silviu-Mihail. "Magnétisme, transport et structure des systèmes de type "spin-valve" utilisant comme couche magnétique dure un sandwich couplé antiferromagnétiquement à base d'iridium." Université Louis Pasteur (Strasbourg) (1971-2008), 2001. http://www.theses.fr/2001STR13103.
Full textLa, Barrière Olivier de. "Modèles analytiques électromagnétiques bi et tri dimensionnels en vue de l'optimisation des actionneurs disques : étude théorique et expérimentale des pertes magnétiques dans les matériaux granulaires." Thesis, Cachan, Ecole normale supérieure, 2010. http://www.theses.fr/2010DENS0032/document.
Full textThe axial flux actuators are potentially an attractive solution for demanding automotive applications such as hybrid vehicles. However, the design of these actuators for such applications encounters some difficulties: the specifications in terms of torque and speed are complex, conflicting criteria to minimize, such as mass and losses. One solution is to use systematic optimization algorithms. To use these algorithms, flexible models are needed, both accurate and fast. This thesis focuses on developing analytical models based on the formal resolution of Maxwell's equations, which allows a good compromise between computation time and accuracy, if some simplifying assumptions such as linearity of magnetic materials are accepted. The first part concerns the electromagnetic two-dimensional models, developing the axial flux structure at its mean radius. For these models, particular attention was paid to modeling of the salience as well as the rotor stator. It is especially shown that the approximation of the Carter coefficient can effectively determine the average torque of the machine with precision. However, if we want to determine the inductions into the iron parts so as to calculate the magnetic losses, a model of stator slotting is required. In a second step, three-dimensional analytical models were developed to calculate the no-load flux in the actuator, taking into account the edges effects and the curvature effect. It is shown that taking into account the edges effects is important in the modeling of the actuators. A study on the curvature effect of the machine shows that the development of the actuator to the mean radius, provided 3D models are used, is not so wrong. A second point concerns the study of magnetic losses in isotropic composite materials, composed of particles of pure iron insulated from each other, put in a binder, and then compressed. Indeed, these materials are very promising in electric machine design, allowing three-dimensional magnetic flux paths and a thermal isotropy, despite their relatively low magnetic permeability. Two materials of the Swedish company Hoganas (one dedicated to electric machines, the other to power electronics, with grains of smaller size) were characterized in terms of magnetic losses in a wide frequency range . A classical loss model was formulated, based on microscopic observations of samples of materials. With this estimate of the classical losses component, the procedure of loss separation can be carried out. The calculation of the excess loss component revealed some specific magnetization mechanisms in these granular materials, in which grains are independent of each other. Unlike laminated materials that have a number of active magnetic objects relatively low on their section at zero field, (eddy currents allow homogenization of the magnetic behavior when the frequency increases), the granular materials appear to exhibit a totally different behavior, with at least one active magnetic object at zero excess field. This changes the dependence of excess losses as a function of frequency (the excess losses are then proportional to the frequency f, while we remember that they are proportional to f ^ 0.5 in most laminated materials). Finally a pre-optimization has been carried out, with just two-dimensional electromagnetic models, and conventional laminated materials. Various studies, as the control law, or the residual induction of the magnets, have been done. This work finishes with an analysis of the influence of a power constraint on the geometry of the electrical machine
Niamien, Manouan Aka Constant. "Antennes miniatures VHF/UHF à base de matériaux magnéto-diélectriques : théorie, conception et expérimentation." Rennes 1, 2010. http://www.theses.fr/2010REN1S146.
Full textThis thesis is a contribution to the NAOMI project led by the National Research Agency (ANR) through the telecom scheme. This work deals with three major parts : in the first part the possibilities offered by magneto-dielectric materials in antenna miniaturization, as well as their impact on printed antennas performances (Q factor, bandwidth, radiation efficiency etc. ) are investigated theoretically, numerically and experimentally. In the second part, some new architecture of ultra-miniature antennas using magneto-dielectric materials are designed, fabricated and measured for mobile TV reception in the DVB-H/DVB-T band (470-862MHz). The third part gives a new approach for modelling receiving antennas to evaluate accurately both the absorbed (received) power and the scattered (re-radiated) power. Based on this approach, a new equivalent circuit for receiving antennas is proposed which is validated by electromagnetic simulations
Chevalier, Alexis. "ETUDE EXPERIMENTALE, ELABORATION ET MODELISATION DE MATERIAUX COMPOSITES A BASE DE POUDRES MAGNETIQUES DOUCES." Phd thesis, Université de Bretagne occidentale - Brest, 1998. http://tel.archives-ouvertes.fr/tel-00484041.
Full textTardieu, Simon. "Fils conducteurs composites (microfils d'argent - cuivre) pour application en champs magnétiques intenses." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30186.
Full textLNCMI-Toulouse produces some of the most intense non-destructive pulsed magnetic fields in the world (98.8 T). The wires used in coils which generate these magnetic fields require high ultimate tensile strength (UTS) in order to resist the Lorentz forces. Moreover, to obtain the longest possible pulse duration, these wires must have an electrical resistivity closest to that of pure Cu. LNCMI and CIRIMAT explore the design and preparation of Cu-based nanocomposite wires obtained by a combination of powder metallurgy, Spark Plasma Sintering (SPS) and wire-drawing. Composite powders with low Ag contents (< 10 % vol. Ag) are prepared by dispersing Ag microwires (diameter 200 nm, length 30 µm) synthesized at CIRIMAT in a commercial spherical Cu powder (diameter 0.5-1 µm). The so-obtained composite powders are consolidated by SPS in the form of cylinders. These cylinders are drawn, without breaking, in the form of fine wires (1 - 0.2 mm). The microstructure of the wires is made up of Cu ultrafine grains (200 - 400 nm) elongated over several micrometers in the drawing direction. Ag microwires are dispersed along the grain boundaries of Cu. The measurement of the electrical resistivity and the UTS of the wires (at 293 K and 77 K) shows that the wires containing only 1 vol. % Ag present the best compromise between high UTS and low electrical resistivity (1100 MPa / 0.49 µÔmega.cm at 77 K). The formation of Cu/Ag alloys during the SPS cycle significantly increases the resistivity of the wires and thus must be avoided. A Cu matrix with a bimodal grain size distribution makes it possible to reduce the electrical resistivity of the wires while keeping high UTS (1080 MPa / 0.45 µÔmega.cm at 77 K). Ag-Cu nanocomposite wires present high UTS, equivalent to that of Cu/Ag alloy wires containing about 20 times more Ag produced by melting and solidification, but their electrical resistivity is about 1.5 times lower
Nong, Thi Thanh Huyen. "Electric control of magnetic behavior in artificial multiferroic composites." Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCD070.
Full textMultiferroic materials present several ferroic orders, i.e. ferromagnetic, ferroelectric and/or ferroelastic. The coupling between these ferroic orders allow the control of the magnetic properties by applying an electric field and vice versa. In order to use their multifunctionality in new applications, this coupling must be efficient at room temperature. This thesis concentrates on materials artificially coupling together a ferromagnetic/ magnetostrictive phase with a ferroelectric/piezoelectric one. The coupling between these two phases is called magnetoelectric (ME). The first chapter describes the state of the art of this ME coupling for different multiferroic composite structures. Characterization techniques and micromagnetic simulation tools are presented in the second chapter. In the third chapter, a hetero-structure given by a magnetostrictive film/flexible substrate/piezoelectric actuator (FeCuNbSiB/Kapton/PE) is studied. The magnetic domains of FeCuNbSiB as well as their orientation are controlled by applying an electric field and studied by local microscopy (MFM). The fourth chapter focuses on a nanocomposite material including magnetostrictive nanoparticles in a flexible piezoelectric matrix (PVDF polymer). The effect of these inclusions (nanoparticles) on the local piezoelectric response of the PVDF is studied by piezoeponse microscopy (PFM). Symmetrically, the influence of the piezoelectric matrix on the static magnetic properties of the nanoparticles is analyzed. In the last chapter, the optimization of the magnetic properties of a set of anisotropic nanoparticles (cobalt nanowires) is studied as fonction of their structure, shape and mutual interactions. This experimental study is corroborated by simulations and targets new composites ME materials including the anisotropic nanoparticles in a flexible piezoelectric matrix
Delma, Ouendpouire Jude. "Étude des matériaux magnétiques composites à particules lamellaires - application à la conception des machines à flux transverse Clawpole à Stator Hybride." Thesis, Université Laval, 2009. http://www.theses.ulaval.ca/2009/26424/26424.pdf.
Full textChausson, Sophie. "Synthèse et utilisation de matériaux hybrides lamellaires pour l'élaboration et la caractérisation de nanocomposites polymères." Caen, 2009. http://www.theses.fr/2009CAEN2047.
Full textThe aim of this work is to elaborate original lamellar hybrid materials and disperse them in a polymer matrix to obtain nanocomposites. They have been prepared using two different matrixes, one apolar (polyethylene) and one polar (polyamide-12). The two lamellar hybrid systems have been dispersed in these matrixes and studied as part of the hybrid nature. The first one, the lamellar oxide KTiNbO5, has been chemically modified with alkylamines having different carbon chain lengths in order to be compatible with the different polymer matrixes. The dispersion of such materials has allowed improving several properties like thermal stability, mechanical resistance and fire resistance. The second family studied is the copper alkylphosphonate one. They have been prepared with different alkyl chain lengths. The aim of this study is to prepare a hybrid material with a transition metal and to disperse it in the polymer matrixes. A deep structural study of the homologue series has revealed two types of compounds: hydrated for the short alkyl chains (number of carbon atoms≤10) and dehydrated for the alkyl chains with n≥10. These two structural types have shown different magnetic behaviours. Finally, the incorporation of these fillers in polyethylene and polyamide-12 has revealed that the chemical nature of the bond which links the organic part to the inorganic one of the hybrid does not allow obtaining an efficient exfoliation mechanism
Garnero, Cyril. "Synthèse organométallique de nanoparticules de FeCo pour l'intégration sur inductance." Thesis, Toulouse, INSA, 2016. http://www.theses.fr/2016ISAT0032/document.
Full textThe continuous development of telecommunication requires permanent enhancement of electronic component performances. Among them, common mode filters play a key role to cancel perturbations and thus noise in electrical transmissions. For telephony purposes, these filters must exhibit optimized properties up to high frequency ranges (GHz). These properties depend strongly on the constitutive inductors, and therefore can be significantly enhanced by the addition of a soft magnetic layer, providing that the magnetic material chosen is insulating with a high magnetic permeability and a ferromagnetic resonance frequency above the GHz.In the framework of the project “Investissement d’Avenir TOURS 2015” initiated by STMicroelectronics, we prepared composite materials loaded with FeCo nanoparticles (NPs). We developed a new chemical synthesis of FeCo NPs based on the decomposition of organometallic precursors ([Fe(N(Si(CH3)3)2)2]2 and Co(N(Si(CH3)3)2)2,THF). NP’s size (1 to 80 nm), shape (sphere, cube, and octahedron) and composition (50< Fe %< 70) can be tuned by adjusting the reaction conditions. Without requiring any annealing treatment, these FeCo NPs are highly crystalline in the body centered cubic structure and exhibit magnetic properties close to the bulk ones. A careful study, combining EELS, Mössbauer spectoscopy, zero field 59Co NMR and XRD with anomalous dispersion effect, evidenced the stabilization of the chemically ordered FeCo B2 structure under specific reaction conditions. This is the first time that such ordered structure is reported in chemically synthesized nanoparticles.In order to significantly enhance the inductors properties, a sandwich structure has been designed where the inductors are integrated on a mesoporous silicium substrate filled with FeCo NPs while an epoxy resin/FeCo Nps composite materials is deposited on top. In this aim, two FeCo nanoparticles based composite materials has been developed: - mesoporous silicium substrate exhibiting a loading of 10.1 gFeCo.m-2 were obtained through colloidal solution impregnation. The nanoparticles filled the 25-30 nm pores all along their 18 μm depth. - epoxy resin filled with nanoparticles (30% in mass) were prepared. SEM and TEM analysis confirmed that the nanoparticles are well dispersed in the polymer. After integration onto planar inductors, an increase of 17 % of the inductance value has been observed.During this project, exotic shape NPs such as FeCo octapods could be obtained. Their 3D structure, characterized by electron tomography leads to exotic magnetic configurations which were studied by electron holography
Garrido, Pacheco Mariano. "Electromagnetic processing of molten light alloys reinforced by micro/nanoparticles." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI010/document.
Full textImprovement in mechanical properties of pure metals and alloys can be achieved by the introduction of ceramic particles appropriately dispersed within the material. These particles can act as nucleation sites enhancing the reduction of the crystallite (grain) size. The dispersion of these nucleant materials presents challenges due to their tendency to sediment and to agglomerate. Particles of nanometric size can also produce the improvement of mechanical properties by several reinforcement mechanisms such as Orowan or grain boundary strengthening. The use of electromagnetic stirring can provide a method to disperse particles and produce changes in the microstructure of the material. The induced stirring can increase the number of nucleation points available during solidification breaking the arms of the new formed dendrites at the solidification front. The temperature field in the molten material can be also homogenized by the action of the electromagnetic stirring. The small temperature gradient produced in the liquid metal can promote the growing of equiaxed dendrites. In this study a Bridgman type furnace has been used to produce materials containing grain refiners and reinforcement particles. The furnace has been equipped with a Bitter coil electromagnet capable to produce a travelling magnetic field (TMF). The electromagnetic stirring provides an induced flow which is used to disperse the particles and produced measurable changes in the microstructure of the materials studied. The experiments carried out were supported with numerical simulations performed by University of Greenwich and Simap laboratory. Experiments performed dispersing SiC microparticles into pure magnesium matrix showed that particle concentration patterns in the material are strongly governed by the vertical orientation of the magnetic field applied (upwards vs downwards). The observed patterns of dispersion obtained from the experiments presented a good agreement with the patterns predicted by the numerical simulation. The effects of the electromagnetic stirring in the grain refining of pure aluminium showed positive results whereas the alloys subjected to stirring presented grain growth. The TMF was used to disperse particles of micrometric and nanometric size. The dispersion of microparticles in magnesium and aluminium alloys did not produce improvements in either grain refinement or mechanical properties. However, the experiments performed dispersing nanoparticles in magnesium alloy showed the improvement of creep resistance
Ren, Xiaotao. "Modélisation semi-analytique des pertes par courants de Foucault dans les matériaux composites." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS159/document.
Full textComposite materials have been widely used in Electrical Engineering, and they have stimulated a growing number of scientific research, especially when it comes to energy savings. Soft Magnetic Composites (SMC) incorporate the attributes of different constituents. They can be designed to exhibit high permeability and to dissipate low Eddy Current (EC) losses compared to more conventional structures such as laminated steel. Nevertheless, electromagnetic properties of SMC are not easily determined. Numerical tools such as finite element method (FEM) are usually employed to provide a full-field description of SMC. As the microstructure has to be finely meshed, it brings significant numerical burden and instabilities. To overcome this restriction, semi-analytical homogenization methods are adapted and applied here. They consist in developing a complex permeability model. In the complex permeability model for SMC, the static magnetic permeability and EC losses are integrated respectively as the real and imaginary part of the complex permeability. Classical estimates are applied to determine the macroscopic effective magnetic permeability. A correct determination of the effective permeability, i.e. the real part of the complex permeability, is crucial for the estimate of EC losses. EC losses formulas are derived for SMC with periodic microstructure in 2D and 3D cases. Furthermore, different approaches of field averaging are employed to obtain lower and upper bounds on the EC losses in SMC. The complex permeability model is then applied to analyze a transformer structure. The magnetic field and EC losses distribution can be obtained on the equivalent homogenized transformer. The results are compared to the full-field calculations on the heterogeneous transformer. A good consistency is observed. Finally, the effect of mechanical stress on the magnetic permeability and loss property of SMC is studied, which leads to a coupled formula of EC loss density as a function of macroscopic stress and magnetic field
Abdelli, Wassim. "Modélisation du rayonnement électromagnétique de boîtiers de blindage par sources équivalentes : application aux matériaux composites." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112093.
Full textThe modeling of composite materials is a domain of study which benefits of increasingly interest. Indeed, the popularization of the use of such materials requires the development of new models in order to better understand their behavior. The automotive and aerospace industry strives to optimize material selection based on the specificities of each application in order to reduce the weight of the equipment and to provide better mechanical and thermal characteristics. Composite materials have been also presented as a potential alternative to metals for the role of electromagnetic shielding. Their generalization in this context is nevertheless hampered by a relative lack of knowledge of their electromagnetic behavior. For this purpose, it is necessary to have methodologies to evaluate the shielding effectiveness of composite enclosures and identify the different corresponding mechanisms and parameters.Moreover, the deployment of these alternative materials on a larger scale is hindered by other constraints related mainly to the difficulty of complete 3D analysis of complex systems including composite enclosures. In fact, the topological complexity of certain components greatly complicates their integration into existing electromagnetic simulation tools. Moreover, the scale ratio between the different levels (system, composite enclosures, electronic card, circuit, component) is too large ; This disparity of scale complexifies considerably the geometrical discretization of the entire system. The combination of these different constraints leads to real difficulties to which EMC engineers face. That is why it is necessary to develop efficient models to facilitate the 3D analysis of the complete host system.This work is therefore divided in two sections :- In a first time, we present a methodology to calculate shielding effectiveness of composite enclosures of electronic equipment. The goal is to evaluate the potential of these materials in terms of electromagnetic shielding and to identify the main contributing factors.- In a second time, and in order to ensure compliance of complex electronic systems incorporating composite shielding enclosures with the stringent requirements of EMC, we propose a modeling methodology of electronic devices radiation. This modeling (based on genetic algorithms) allows to replace the radiating devices and enclosures (especially composites) by a set of elementary dipoles. The equivalent model, "black box" type, is thus representative of the entire structure in terms of high frequency electromagnetic radiation and is easily integrable in the mesh of host structures. This multipolar model provides spatial and frequency predictions of the electric and magnetic field, enabling among others to calculate the shielding effectiveness of the radiating enclosure in space, thereby giving a way to quantify its disruptive impact on its environment. Moreover, this approach allow to simplify the 3D analysis of a complete system comprising composite enclosures by controlling the EM behavior at all levels: system, enclosures, cards, circuits and components
Ben, ghzaiel Tayssir. "Synthèse, caractérisation et étude des propriétés magnétiques et diélectriques de nanocomposites Polyaniline/hexaferrite pour l'absorption des micro-ondes." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLN003/document.
Full textThis thesis deals with the formulation of Polyaniline/hexaferrite nanocomposite for absorbing electromagnetic waves. The main idea is the process of composite materials based on polymers intrinsic conductors such as polyaniline that we doped with different types of acids (HCl, CSA, NSA, and ... TSA) and barium hexaferrite with magnetoplumbite structure with or without substitution according to desired stoichiometries. In the barium hexaferrite, the substitution of Fe 3+ is made by Al3+, Bi3+, Cr3+ and Mn3+ ions.The barium hexaferrite and its substitutions by different ions mentioned above were synthesized dynamic hydrothermal method by varying various parameters during the synthesis (pH, temperature, time, ratio [OH-]/[NO3-] ...).The elaboration of polyaniline/hexaferrite composite (pure or substituted) was carried out by oxidative polymerization using various synthesis techniques: Aqueous-Based Polymerisation with or without agitation (taking into account the nature of the acid used) (ABP) and Solid-Based Polymerization (SBP). The optimization of these various synthesis techniques after physicochemical (XRD, FTIR, TGA, SEM, EDX), dielectric (ε ', ε' ', σdc) and magnetic (Mr, Ms, Hc, Tc, µ', µ'') characterizations of the samples showed that the solid route is the easiest method, economical and environmentally friendly. It is also suitable for the production of composite Pani/BaFe12O19 with good structural, physical and magnetic properties.The study of the substitution of Fe 3+ in the BaFe12O19 by Al3+, Bi3+, Cr3+ and Mn3+ showed a strong dependence of the structural and magnetic properties with the distribution of these ions in the hexagonal crystal lattice. In fact, Al3+, Cr3+ and Mn3+ ions tend to occupy the tetrahedral sites, while the Bi3+ favoured the octahedral sites. An increase in Hc associated with the small crystallite size observed for particles substituted with Al and Cr and the enhancement magnetocristalline anisotropy (strong higher order term) for Bi and Mn due to their high ionic radius.The incorporation of the substituted hexaferrite in the polyaniline to obtain Pani/BaMeFe11O19 composite, where Me = Al, Bi, Cr and Mn, reveals a variation in electromagnetic properties in the frequency range from 1 to 18 GHz. In fact, these variations are due to the formation of dipoles between the substituting ion and surrounding O2- cations in the ferrite which are responsible for the ferromagnetic resonance, the magnetocrystalline anisotropy and the exchange interaction with the polymer. The composite Pani/BaFe12O19 shows absorption bands at the X-band that shift to the Ku-band with the substitution of iron, confirming the potential of these materials for microwave applications
De, La Barrière Olivier. "Modèles analytiques électromagnétiques bi et tri dimensionnels en vue de l'optimisation des actionneurs disques : étude théorique et expérimentale des pertes magnétiques dans les matériaux granulaires." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2010. http://tel.archives-ouvertes.fr/tel-00562019.
Full textDib, Radwan. "Caractérisation de couches diélectriques et magnétiques de structures multicouches par cavité résonante microonde." Thesis, Saint-Etienne, 2014. http://www.theses.fr/2014STET4014/document.
Full textThis thesis aimed at characterizing the dielectric and magnetic layers of multilayer structures by using the technique of microwave resonant cavity. Multilayer structures have specific electromagnetic properties and are becoming increasingly important in many industrial domains, such as in radio-communication systems. The electromagnetic characterization remains a priority for understanding the characteristics of electromagnetic wave propagation in such environments. The thesis proposed a new experimental approach to determine the effective dielectric properties in a bilayer structure as a function of the characteristics and thickness of each specific layer. In particular, we apply the expressions of permittivities derived from the perturbations method which are used in resonant cavities in case of a bilayer rectangular sample. The established theoretical analysis leads us to propose a new expression of simple proportionality describing a relationship between the mean dielectric properties of a bilayer material and the relative dielectric properties and thickness of the constituent layers. The presented method has been successfully applied to different bilayer materials. Particularly, it allowed the characterization of a very thin layer (YIG layer) of thickness 19.6 microns deposited by cathodic sputtering on an alumina substrate by knowing the thickness and dielectric properties of this substrate. The comparison with the experimental results revealed good agreement between theory and measurement. The analysis of the uncertainty associated to the calculation of the permittivity by the presented method showed good sensitivity. Finally, we provide the curves of variation of the effective permeability measured for a bilayer stack
Verstraete, Kévin. "Étude du multi-colaminage de matériaux différents." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS057/document.
Full textThe Accumulative Roll Bonding (ARB), consisting in a repetition of roll bonding, is known as a suitable process to work out composite with tailored properties and higher mechanical strength. The present study aimed to develop two functional composites at room and hot temperatures: AA6061/AA5754 and AA6061/IF steel. The first one was developed with both ARB and Cross-ARB (CARB). The Cross-ARB changes the rolling direction by 90° between each pass. As a result, the second process showed higher strength at room temperature. A hotter temperature of process prevented a further enhancement of the strength. According to the temperature of the process, different architectures were obtained. Indeed, ARB at room temperature led to the necking then to the fragmentation of the hard phase and, as a consequence to the collapse of the strength of the composite AA6061/IF steel. The temperature preserved the stratification in the AA6061/AA5754 composite but favored the appearance of intermetallic phase in the AA6061/ IF steel composite. Eventually, the first composite was able to resist to the hot cracking while the second showed magnetic shielding effectiveness
Veiller, Laurent. "Etude de multicouches fer/terbium : simulation numérique Monte Carlo de propriétés magnétiques et analyse structurale par sonde atomique." Rouen, 1998. http://www.theses.fr/1998ROUES051.
Full textMarteau, Antoine. "Modèles multi-échelles pour les problèmes électromagnétiques transitoires non linéaires avec courants induits confinés." Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALT019.
Full textHeterogeneous materials and structures, such as coils, laminations and soft magnetic composites (SMCs), are widespread in electrical engineering. They have the characteristic of being made up of many elements smaller than their own size, making their numerical simulation difficult.This thesis investigates multiscale modeling techniques of electromagnetic field used for the numerical resolution of transient 3D nonlinear problems with strong electromagnetic couplings, on heterogeneous structures or materials with periodic geometries. The numerical method used is the Heterogeneous Multiscale Method (HMM). It is based on a scale separation hypothesis, enabling the homogenization of the material. The equivalent constitutive law is calculated on representative volumes elements with independent behaviors, solved in parallel at the macroscopic points where it is necessary.The main contribution of this work is to introduce a new homogenization formula for the field H, with several numerical implementations. The method is robust to the presence of strong locally confined currents. These developments are necessary for the use of the B-conform formulation at high frequencies. Indeed, these currents create additional magnetization which is responsible for dynamic hysteresis in the macroscopic magnetic constitutive law. The model is validated on linear and non-linear 3D problems
Smaili, Arezki. "Développement de matériaux composites pour la réfrigération magnétique." Thèse, Université du Québec à Trois-Rivières, 1998. http://depot-e.uqtr.ca/6846/1/000642386.pdf.
Full textAmmar, Mehdi. "Étude du magnétisme de composites métal-oxyde et métal-diélectrique nanostructurés pour composants passifs intégrés." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2007. http://tel.archives-ouvertes.fr/tel-00371362.
Full textZadoina, Lacramioara. "Composites polymère mésomorphe/nanoparticules magnétiques : vers un matériau magnéto-stimulable." Toulouse 3, 2010. http://thesesups.ups-tlse.fr/920/.
Full textThe topic developed in this manuscript aims at obtaining a magnetic-responsive material by inserting magnetic nanoparticles into a liquid crystal polymer matrix. This work was accomplished in partnership of three laboratories of Toulouse, IMRCP, LCC and LPCNO, as part of a Marie Curie EST European network (Early Stage Research Training) called Nanotool. Two methods of creation of this type of material were examined: either by direct in situ synthesis of magnetic nanoparticles, into the medium containing the liquids crystals, or by ex-situ synthesis of magnetic nanoparticles and their incorporation into a liquid crystal polymer matrix. The synthesized materials were characterized by different techniques of analysis (calorimetric measurements (DSC), optical microscopy (POM), electronic microscopy (TEM, HRTEM), and magnetic measurements (SQuID)), characterizations which proved that the polymeric matrix become magnetic by both methods of synthesis, while keeping the liquid crystal properties. The magnetic liquid crystal polymer material exhibited very good answers to a magnetic field
Noutehou, Nathan. "Conception de circulateurs et isolateurs pour des applications spatiales : nouvelles technologies d'intégration." Thesis, Brest, 2019. http://www.theses.fr/2019BRES0033/document.
Full textThe goal of this PhD thesis is to explore new technologies that make possible to improve the integration of isolators in radiofrequency chain of satellites. These components are especially used to control matching of amplifiers.We propose two ways of producing these isolators. At first, ferricomposite materials are studied to design low-cost isolators at Kuband.Then, we studied pre-oriented strontium or barium hexaferrites to design self-biased components (without magnets) for Q and Ka band frequencies
BARRE, Olivier. "Contribution à l'étude des formulations de calcul de la force magnétique en magnétostatique, approche numérique et validation expérimentale." Phd thesis, Université des Sciences et Technologie de Lille - Lille I, 2003. http://tel.archives-ouvertes.fr/tel-00005921.
Full textSalahun, Erwan. "Étude et réalisation de dispositifs microondes agiles à commande magnétique utilisant des composites ferromagnétiques." Brest, 2002. http://www.theses.fr/2002BRES2024.
Full textMichaud, Bernard. "Etude de l'orientation de fibres céramiques sous champ magnétique : application à l'élaboration de matériaux composites à matrice métallique." Phd thesis, Université Sciences et Technologies - Bordeaux I, 1998. http://tel.archives-ouvertes.fr/tel-00169119.
Full textRousselle, Danièle. "Elaboration et caractérisation de matériaux composites à base de particules ferromagnétiques et d'une matrice céramique." Bordeaux 1, 1992. http://www.theses.fr/1992BOR1A670.
Full textRousselle, Danièle. "Elaboration et caractérisation de matériaux composites à base de particules ferromagnétiques et d'une matrice céramique." Bordeaux 1, 1992. http://www.theses.fr/1992BOR10676.
Full textRobbes, Anne-sophie. "Nanocomposites à base de particules magnétiques : synthèse et contribution de la dispersion des charges et de la conformation des chaines sur les propriétés de renforcement." Thesis, Paris 11, 2011. http://www.theses.fr/2011PA112201/document.
Full textThe mechanical properties of polymeric nanocomposite films can be considerably enhanced by the inclusion of inorganic nanoparticles due to two main effects: (i) the local structure of fillers dispersion and (ii) the potential modification of the chains conformation and dynamics in the vicinity of the filler/polymer interface. However, the precise mechanisms which permit to correlate these contributions at nanometric scale to the macroscopic mechanical properties of the materials are actually poorly described. In such a context, we have synthesized model nanocomposites based on magnetic nanoparticles of maghemite γ-Fe2O3 (naked or grafted with a polystyrene (PS) corona by radical controlled polymerization) dispersed in a PS matrix, that we have characterized by combining small angle scattering (X-Ray and neutron) and transmission electronic microscopy. By playing on different parameters such as the particle size, the concentration, or the size ratio between the grafted chains and the ones of the matrix in the case of the grafted fillers, we have obtained nanocomposite films a large panel of controlled and reproducible controlled filler structures, going from individual nanoparticles or fractal aggregates up to the formation of a connected network of fillers. By applying an external magnetic field during the film processing, we succeeded in aligning the different structures along the direction of the field and we obtained materials with remarkable anisotropic reinforcement properties. The conformation of the chains of the matrix, experimentally determined thanks to the specific properties of neutron contrast of the system, is not affected by the presence of the fillers, whatever their confinement, the dispersion the fillers or their chemical state surface. The alignment of the fillers along the magnetic field has allowed us to describe precisely the evolution of the reinforcement modulus of the materials with the structural reorganization of the fillers and the chains at the local scale under stretching, and thus to highlight the key role played by the fillers reorganization under stretching on the nanocomposite reinforcement mechanisms
Mallégol, Stéphane. "Caractérisation et application de matériaux composites nanostructurés à la réalisation de dispositifs hyperfréquences non réciproques." Phd thesis, Université de Bretagne occidentale - Brest, 2003. http://tel.archives-ouvertes.fr/tel-00004319.
Full textTricot, Grégory. "Compréhension du rôle des phosphates dans l'inhibition de l'oxydation catalytique des matériaux composites C/C." Lille 1, 2005. http://www.theses.fr/2005LIL10156.
Full textThe present manuscript focuses on the investigation of anti-catalytic properties of an aluminophosphate coating used for the protection of airplane brakes made of C/C composite materials. The catalytic oxidation is an important problem in aeronautic applications because of the presence of catalysts (Na, K, Mg & Ca) in De-Icer solutions used in airports. The formation of the protective coating from metallic phosphate solutions have been studied by XRD and solid state NMR. The determination of the anti-catalytic mechanisms has been achieved through the study of the reactivity between phosphate coating and catalysts. The structural characterization has been carried out using a combination of recently developed 2D sequences based on homo and heteronuclear correlations
Khalil, Chady. "Développement du procédé de soudage par impulsion magnétique pour soudage hétérogène bimétallique et pour assemblage hybride métal / composite." Thesis, Ecole centrale de Nantes, 2018. http://www.theses.fr/2018ECDN0031.
Full textReducing CO2 emissions and improving performance are still the main goals of the automotive industry. To achieve these objectives, automotive suppliers are still seeking to lighten the structures through the use of heterogeneous materials that have evolved in recent decades. We find today in one vehicle mild steels, very high strength steels, light alloys such as aluminum and magnesium alloys as well as fiber reinforces polymeric composites. The presence of dissimilar materials arises several challenges regarding both the heteregeneous metal assemblies and hybrid metal / composites assemblies. The differences in the mechanical, thermal and chemical properties of the various materials limit the use of traditional assembly techniques, i.e. mechanical assembly, fusion welding and adhesive bonding, and thus the development of new assembly solutions is required. In this context, this study aims to meet the challenges of heterogeneous metal welding and aims to develop two new original hybrid metal / composite assembly solutions using the magnetic pulse welding process
Creton, Élodie. "Élaboration d’une protection anti-oxydation pour matériaux composites SiC/SiC efficace à basse température." Thesis, Lille 1, 2009. http://www.theses.fr/2009LIL10186/document.
Full textThis work presents anti-oxidation coating (AOC) of composite materials SiC/SiC. These materials have specific properties (lightness, excellent resistance to thermal shocks, and mechanical endurance at very high temperature) due to the combination of SiC fibers and SiC matrix linked by a C interphase. This interphase oxidizes under air above 400°C, leading to fiber/matrix debonding and thus compromising the mechanical properties. In view of application in civil aeronautics, the AOC have to be operational at low temperatures (400-650°C) and for prolonged periods (of the order of thousands of hours). Two types of coatings were proposed and examined: (i) a rigid coating obtained through the thermal treatment of a mixture of aluminium phosphate solution and silica. The structure of the coating has been characterized by NMR, XRD and SEM and related to the efficiency of the protection. (ii) a dynamic coating, based on phosphate glasses formulated to present optimum viscosity characteristics. The different glasses were characterized by thermal analyses (DTA, TMA, HSM) and by NMR. A thought approach was implemented by correlation between thermal properties and structural characteristics of oxides used. These two coatings improve the material lifetime even if the expected specification was not accomplished. To conclude, the dynamic coating is more adapted to low temperature use and we suggest some improvements