Rozprawy doktorskie na temat „Anisotropie de croissance”
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Moreau, Nicolas. "Croissance et magnétisme de nano-alliages CoxPt1-x supportés". Paris 6, 2010. http://www.theses.fr/2010PA066648.
Pełny tekst źródłaBorme, Jérôme. "Alliage antiferromagnétique MnPt : croissance, propriétés magnétiques et structurales". Phd thesis, Grenoble 1, 2006. http://www.theses.fr/2006GRE10124.
Pełny tekst źródłaMolecular-beam epitaxy growth of MnPt/Pt (100) has been studied. The MnPt alloy, chemically-ordered with L10 structure, has beeen elaborated by codeposition and by a multilayer method. The codeposition leads to a twinned structure with in-plane tetragonal axis. The multilayer method gives rise to a favoured out-of-plane orientation of the tetragonal axis. The magnetic structure of each of the two deposited alloys has been characterized. Exchange-coupled Fe/MnPt and FeNi/MnPt bilayers have been elaborated. Due to the competition between intrinsic anisotropies and exchange anisptropy, the angular behaviour of magnetic properties (coercive field and exchange bias) of the ferromagnetic layer shows a complex evolution and an induced anisotropy. A model of total energy has been used to interpret the experimental data. In-field magnetic-force microscopy study of the magnetization shows distinct reversal mechanisms according to the respective orientation of the field and anisotropies. At a low scale, anisotropy competition leads to the appearance of magnetic ripples. The latter have been observed and modelled. The effect of light ion irradiation on the structure has also been investigated
Borme, Jérôme. "Alliage antiferromagnétique MnPt : croissance, propriétés magnétiques et structurales". Phd thesis, Université Joseph Fourier (Grenoble), 2006. http://tel.archives-ouvertes.fr/tel-00159060.
Pełny tekst źródłaBonilla, Francisco Javier. "Nanofils ferromagnétiques auto-assemblés de Co, Ni et d’alliages CoNi : croissance, structure et propriétés magnétiques". Paris 6, 2013. http://www.theses.fr/2013PA066244.
Pełny tekst źródłaThis thesis reports on the study of self-assembled ferromagnetic nanowires of Co, Ni and CoNi alloys embedded in a CeO2/SrTiO3(001) matrix. These systems are grown by pulsed laser deposition. The nanowires have diameters in a 1. 5 -7 nm range, depending on the growth conditions, and densities above 1 Tb/inch2. For each type of nanowires (NWs) assembly (Co, Ni, CoNi alloys), the composition, morphology, crystalline structure and magnetic properties were studied using a combination of techniques (X-ray absorption spectroscopy, transmission electron microscopy, X-ray diffraction, magnetometry). Co-NWs are textured and anisotropic, with an easy axis along the wire axis. The correlation between the magnetic response and the structure is evidenced and corroborated by means of a model for the mechanism of magnetization reversal. Ni-NWs are monocrystalline and epitaxied with the surrounding matrix. Contrary to Co-NWs, the Ni-NWs are not anisotropic. Structural studies reveal an axial deformation of the Ni lattice. This introduces a magnetoelastic anisotropy term competing with the wires shape anisotropy. The compensation of the different anisotropies in the Ni-NWs is further supported by of micromagnetic simulations. Based on these results, some alternatives to tune the magnetic anisotropy in Ni-NWs are presented. CoxNi1-x alloy NWs, obtained from a combinatorial growth method, are monocrystalline, epitaxied and anisotropic. It is shown that the total magnetic anisotropy of the system can be tuned by controlling the Co content in alloy NWs. Finally, perspectives issued from this work are sketched
Maillard, Mathieu. "Synthèse, organisation et anisotropie optique de nanocristaux d'argent". Paris 6, 2002. http://www.theses.fr/2002PA066436.
Pełny tekst źródłaCalifano, Valeria. "Étude structurale de verres d'oxydes pour l'optique non linéaire : croissance de nanostructures et effet d'un champ électrique ('poling')". Lyon 1, 2005. http://www.theses.fr/2005LYO10103.
Pełny tekst źródłaGéminard, Jean-Christophe. "Croissance libre de la phase colonnaire hexagonale d'un cristal liquide discotique". Lyon 1, 1993. http://www.theses.fr/1993LYO10128.
Pełny tekst źródłaMougin, Alexandra. "Nanosystèmes magnétostrictifs de TRFe2(110) (TR=terre rare) : croissance, morphologie et propriétés magnétiques". Nancy 1, 1999. http://docnum.univ-lorraine.fr/public/SCD_T_1999_0122_MOUGIN.pdf.
Pełny tekst źródłaJubert, Pierre-Olivier. "Croissance et propriétés magnétiques de nanostructures épitaxiées auto-assemblées : le système Fe/Mo(110)". Phd thesis, Université Joseph Fourier (Grenoble), 2001. http://tel.archives-ouvertes.fr/tel-00004054.
Pełny tekst źródłaRohart, Stanislas. "Croissance et magnétisme de nanostructures organisées sur surfaces cristallines". Phd thesis, Université Paris-Diderot - Paris VII, 2005. http://tel.archives-ouvertes.fr/tel-00010738.
Pełny tekst źródłaEl, Beainou Raya. "Relations structure - propriétés de conduction dans des films W-Cu nanostructurés". Thesis, Bourgogne Franche-Comté, 2019. http://www.theses.fr/2019UBFCD004/document.
Pełny tekst źródłaW and W-Cu thin films were deposited by the GLAD co-sputtering technique from two opposite targets: W and Cu. Each target was focused on the center of the substrate with a tilt angle of α = 80 °. Several series were prepared changing some experimental parameters: the sputtering pressure, the film’s thickness as well as the target currents. The nature of as-deposited films and their morphological properties were studied in order to understand the correlations between some structural characteristics and electrical behaviors of these structured films. The experimental parameters play a key-role on the shape of the columns, their angle of inclination, and the elemental composition of these W-Cu films. The influence of these parameters on the films morphology was demonstrated and related to the electronic transport properties in these columnar films. The copper was chemically etched in order to obtain a more porous structure, with the aim of improving the electrical anisotropy. A theoretical model was also developed in order to understand the electrical conductivity mechanism in these columnar films taking into account the anisotropic structure of the columns. This model was applied to W, as-deposited W-Cu and etched W-Cu films
Schuler, Vivien. "Nanofils ferromagnétiques auto-assemblés en matrice d'oxyde : croissance, épitaxie verticale et propriétés magnétiques". Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066263/document.
Pełny tekst źródłaIn this PhD thesis, we study the growth and the properties of ferromagnetic nanowires made of cobalt, nickel and cobalt-nickel, embedded in a matrix made of of strontium and baryum titanate. The nanowires are grown taking advantage of self-assembly processes occurring during sequential pulsed laser deposition. First, we model the growth with a kinetic Monte-Carlo code to highlight the parameters that control the diameter and the density of the nanowires. Then, it is shown that the nanowires are strained along their axis, and relaxed perpendicular to it. The origin of the strained state is explained in the framework of the Frenkel-Kontorova model, and its inhomogeneities are described through analysis of mappings of the reciprocal space. Furthermore, it is shown that the strain is high enough to shift the magnetic easy axis of the nickel nanowires, through magneto-elastic coupling. Finally, for Co0.4Ni0.6 nanowires with a diameter greater than four nanometers, the blocking temperature of the assembly is above room temperature and the energy barrier for the magnetic reversal of the nanowires is of the order of one electronvolt. This is interesting for potential applications in data storage, for example
Meunier, Anthony. "Epitaxie de systèmes métalliques sur si(001) : croissance du cuivre et structures à anisotropie magnétique perpendiculaire (Cu/Ni et FePd)". Grenoble 1, 2005. http://www.theses.fr/2005GRE10012.
Pełny tekst źródłaThis work focus on the epitaxial growth of thin metallic layers on Si(001). An experimental study of copper growth at room temperature is first presented. For the first time we experimentally demonstrate the important role of preliminary surface hydrogenation on interdiffusion properties. Surface hydrogenation inhibits interdiffusion and results in the controlled formation of an 2 nm thick silicide quasi continuous layer. Chemical and structural nature of the interface have been deduced from a large field of experiments : RHE ED, AES, TEM and GIXRD. This silicide is not the h-Cu3Si phase usually reported but is a centred cubic phase close to the b-CuO. 83SiO. 17 phase with a lattice parameter a = 0,288 nm. Following metallic copper growth on this seed layer has been studied through STM and TEM experiment Copper layer is highly {001} textured and show columnar pseudo grains with an homogeneous lateral size increasing with thickness. The last part of this work deals with the growth of perpendicular magnetic anisotropy systems, Cu/Ni and FePd on Si(001). Ln Cu/Ni system, it is shown that interdiffusion occurs during Ni layer growth based on auger spectroscopy experiments and a copper segregation mode!. This mixing at the Cu/Ni interface mainly explain the decrease of magnetic properties measured for thin Ni layers. We finally repor for the first time the growth of a template structure based on the use of a thin silicide (Cu-Si or FeSi2) seed layer for FePd alloy epitaxy or SI(001). Structural and magnetic measurements reveal a weil ordered FePd layer and a high perpendicular magnetic anisotropy
Schuler, Vivien. "Nanofils ferromagnétiques auto-assemblés en matrice d'oxyde : croissance, épitaxie verticale et propriétés magnétiques". Electronic Thesis or Diss., Paris 6, 2015. http://www.theses.fr/2015PA066263.
Pełny tekst źródłaIn this PhD thesis, we study the growth and the properties of ferromagnetic nanowires made of cobalt, nickel and cobalt-nickel, embedded in a matrix made of of strontium and baryum titanate. The nanowires are grown taking advantage of self-assembly processes occurring during sequential pulsed laser deposition. First, we model the growth with a kinetic Monte-Carlo code to highlight the parameters that control the diameter and the density of the nanowires. Then, it is shown that the nanowires are strained along their axis, and relaxed perpendicular to it. The origin of the strained state is explained in the framework of the Frenkel-Kontorova model, and its inhomogeneities are described through analysis of mappings of the reciprocal space. Furthermore, it is shown that the strain is high enough to shift the magnetic easy axis of the nickel nanowires, through magneto-elastic coupling. Finally, for Co0.4Ni0.6 nanowires with a diameter greater than four nanometers, the blocking temperature of the assembly is above room temperature and the energy barrier for the magnetic reversal of the nanowires is of the order of one electronvolt. This is interesting for potential applications in data storage, for example
Moreau, Nicolas. "Croissance et magnétisme de nano-alliages Co(x)Pt(1-x) supportés". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2010. http://tel.archives-ouvertes.fr/tel-00574364.
Pełny tekst źródłaZhu, Kangying. "Etude des mécanismes de déformation et de recristallisation dans un alliage de zirconium". Paris 13, 2006. http://www.theses.fr/2006PA132021.
Pełny tekst źródłaOderno, Vincent. "Croissance de couches minces épitaxiées de phases de Laves TR-Fe2 (TR=Y, Tb, Dy et Er) : influence des déformations épitaxiales sur l'anisotropie magnétique". Vandoeuvre-les-Nancy, INPL, 1996. http://www.theses.fr/1996INPL072N.
Pełny tekst źródłaMechehoud, Fayçal. "Croissance par voie électrochimique et propriétés magnétiques et topographique de couches minces de Co sur Si(111)". Thesis, Mulhouse, 2016. http://www.theses.fr/2016MULH7833/document.
Pełny tekst źródłaWe have deposited thin layers of Co on a semiconductor substrate Si(111), by electrochemical method, in potentiostatic and galvanostatic mode, and we have studied their topographic properties (AFM, MEB) and magnetic (RMN, effet Kerr, SQUID). Thanks to these different techniques, we could relate these properties to the growth modes and to the a priori identical deposition conditions, which lead to different morphologies and therefore different magnetic properties. We have developed a rigorous approach with a systematic control of the quality of the substrate in order to clarify the nucleation and growth modes as a function of the potential applied in chronoamperometry. A transition from an instantaneous nucleation mode to a progressive nucleation mode as a function of the applied potential is highlighted. Modeling with Scharifker-Hills model of nucleation and growth modes is consistent with AFM topography images. The growth is three-dimensional of a Volmer-Weber type and the magnetization is oriented in the plane. By NMR and also X-Ray Photoemission Spectroscopy (XPS), we could show that a layer of magnetically dead cobalt hydroxide layer forms at the interface with Si. In galvanostatic mode, grains with perfectly crystallized facets have magnetic domains located in most of the islands. We have also carried out a very critical study of the deposition / tearing techniques used in the literature showing that they are unsuitable for semiconductor substrates, a deposit remaining on the surface whatever the tearing technique chosen
Lu, Lili. "Mécanisme de croissance et propriétés physiques de couches minces à base de composés analogues du bleu de Prusse". Phd thesis, Ecole Polytechnique X, 2014. http://pastel.archives-ouvertes.fr/pastel-01058915.
Pełny tekst źródłaMorin, Léo. "Influence des effets de forme et de taille des cavités, et de l'anisotropie plastique sur la rupture ductile". Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066230/document.
Pełny tekst źródłaDuctile fracture of metallic alloys occurs by the nucleation, growth and coalescence of microvoids. In a first step, we study the influence of void shape effects and plastic anisotropy on the growth phase. we implement numerically in a finite element code the void growth model of madou and leblond for ellipsoidal voids embedded in an isotropic material, in order to apply the model to ductile fracture problems involving important void shape effects. We show that the consideration of void shape effects is necessary in order to reproduce shear-dominant ductile fracture. This model is then extended to plastic anisotropy, in the spirit of the models of monchiet and benzerga. In particular, we derive a macroscopic criterion for anisotropic materials containing general ellipsoidal voids, which is assessed by finite element limite analyses. In a second step, we study the effects of void size on the ductile fracture of nanoporous materials contenant spherical or spheroidal voids. The last part of the thesis is dedicated to the study of void shape effects and plastic anisotropy on the coalescence phase. We derive two new criteria of coalescence by internal necking, which are assessed numerically. Then, we derive a new criterion that permits to unify the growth and coalescence phases. Finally we study the influence of plasticy anisotropy on coalescence by internal necking
Berling, Dominique. "Corrélation entre structure – morphologie – anisotropies magnétique et magnéto-optique de couches minces de Fer épitaxiées sur Silicium". Habilitation à diriger des recherches, Université de Haute Alsace - Mulhouse, 2006. http://tel.archives-ouvertes.fr/tel-00194016.
Pełny tekst źródłaLa fonction d'énergie d'anisotropie magnétique des couches minces a été étudiée à l'aide d'une nouvelle méthode de mesure par effet Kerr magnéto-optique : la méthode TBIIST (Transverse Bias Initial Inverse Susceptibility and Torque) intégrant de plus une détermination des différentes contributions magnéto-optique non linéaire en aimantation au signal Kerr. Ces dernières reflètent et traduisent la symétrie cristallographique du système étudié ainsi que les brisures de symétrie liées à la morphologie des surfaces – des interfaces (croissance d'îlots asymétriques) induites par les conditions d'élaboration des couches épitaxiées. Les propriétés d'anisotropie magnétique et magnéto-optique observées et les interprétations expérimentales ont été confortées par des modélisations, des calculs et des simulations à partir des images de topologie STM.
Han, Liuyang. "Croissance et caractérisations complètes de structures ferroics artificielles à base de matériaux ferroélectrique et anti ferroélectrique : comparaison des performances en termes de coefficient de couplage magnétoélectrique et de l'accordabilité de la perméabilité". Thesis, Valenciennes, Université Polytechnique Hauts-de-France, 2019. http://www.theses.fr/2019UPHF0006.
Pełny tekst źródłaThe magnetoelectric (ME) coupling effect, a coexistence of electrical polarization and magnetization in multiferroic materials, has been widely investigated, both from a fundamental science perspective and an application point of view. Many researchers have devoted their efforts to realize electric field (E) control of magnetism, instead of a magnetic field (H), i.e., converse magnetoelectric (CME) coupling effect. The CME effect can be realized in ferromagnetic (FM)/ferroelectric (FE) composites with an elastic strain mediation, which enables the development of novel multiferroic devices such as information storage, microwave tuning, and multi-function electronic devices. FE materials have been intensively used in multiferroic composites to obtain a significant CME coupling effect. The FM/FE composites have achieved significant advancements because of the considerable E-induced strain in FE phases. The antiferroelectric (AFE) materials also undergo large deformation under the application of E, and large E-induced strain is generated. However, very few works have reported the CME coupling effect in AFE-based multiferroic composites. In our work, a series of ME heterostructures were investigated for the fundamental understanding of AFE-based multiferroic heterostructures and the differences in the performances of AFE- and FE-based multiferroic heterostructures. The AFE ceramic and FE ceramic, (Pb, La)(Zr, Sn, Ti)O₃ (PLZST) and Pb(Mg, Nb)O₃-Pb(Zr, Ti)O₃ (PMN-PZT), were prepared as substrates to deposit FM films. Then the NiMnGa (NMG) alloys, the ferrite Y₃Fe₅O₁₂ (YIG) film, and uniaxial [(TbCo₂)/(FeCo)]₂₀ (TCFC) films were used to couple with AFE and FE materials. The work first included a study of the strain-mediated CME coupling manipulation in NMG/PLZST/NMG heterostructure. The NMG/AFE heterostructures have been reported several times, but the E control of magnetization has never been reached. Here, the CME coupling effect in AFE-based heterostructure has been first revealed. The magnetization of NMG film changes rapidly at the switching fields of PLZST. At 0 Oe, the magnetization change of NMG film reaches the maximum (15%). Secondly, the ferrite YIG films deposited on PLZST and PMN-PZT ceramic substrates were studied. The CME coupling effect in YIG/PLZST and YIG/PMN-PZT was carried out, and the differences of CME performance in AFE- and FE-based ME heterostructure were revealed. The considerable E-induced strain in AFE substrate leads to maximum in-plane CME coefficient (αCME =11.6 × 10⁻⁸ s/m) at 0 Oe and a maximum of in-plane relative magnetic susceptibility change (∆χ/χ0 =33%) with a low magnetic field of 10 Oe in YIG/Pt/PLZST/Pt heterostructure. The maximum of in-plane αCME (18.15 × 10⁻⁸ s/m) is observed when H = 25 Oe. The part of work demonstrated the electric-field induced strain plays a crucial role in the CME coupling effect. The different strain evolutions of substrates favors the difference in the CME coupling effect of YIG/AFE and YIG/FE. Thirdly, we investigated the CME coupling effect of uniaxial TCFC films on PLZST and PMN-PZT substrates along different axes. A significant manipulation by E can be realized along the hard axis of TCFC film, and a reverse transition of M-E curves occurs. In TCFC/PLZST, the maximum of αCME is at 500 Oe with a value of 12.7×10⁻⁸ s/m. In TCFC/PMN-PZT, the maximum of αCME reaches 136.6 ×10⁻⁸ s/m with a bias H = 300 Oe. Along the easy axis and out-of-plane direction, the CME coupling effect has also been discussed. Finally, the YIG/AFE and YIG/FE heterostructures have been prepared in the full thin-film form to explore the CME coupling effect. The results indicate that a FM phase with a strong magnetic response along OOP direction is needed for Magnetic Force Measurement (MFM) to evaluate the ME performance of these structures
Dongmo, Keumo Jiazet Joël Hans. "Acclimatation des arbres au changement des sollicitations mécaniques induites par le vent suite à une éclaircie dans un peuplement de Hêtre". Electronic Thesis or Diss., Paris, AgroParisTech, 2022. http://www.theses.fr/2022AGPT0014.
Pełny tekst źródłaWhile the tree growth potential is mainly determined by access to resources such as light or water, the distribution of produced biomass is under strong biomechanical control. The tree response to mechanical stimuli such as those induced by wind is called thigmomorphogenesis. This response has been mainly studied on very young trees under controlled condition, and only rarely in natural condition. This is the first study dealing with the tree growth in a broadleaf stand aiming to quantify the importance of thigmomorphogenetic effect as a growth factor in the silvicultural context. The experimental set-up includes forty trees divided into four groups of ten trees selected in a dense 35yrs old F. sylvatica L .stand. Each group was submitted to one of following treatments: thinning without guying, thinning with guying, guying only and controls.Considering the thigmomorphogenetic effect on the biomass allocation inside the tree, our results show that 45% of the stem volume growth and 61% of the root radial growth of thinned trees are due to wind-induced mechanical stimuli. Further, the distribution of tree ring area along the tree stem is under strong mechanosensitive control. In contrast, no effect of mechanical stimuli or thinning was observed on axial growth. Considering the explanation of the circumferential growth anisotropy, our results do not highlight a thigmomorphogenetic effect despite the identification of dominant sectors for strong winds and strains. The hypothesis put forward is that the directional variability of perceived strains is too high to induce a strongly directional growth response as it is usually the case under controlled conditions
Démoulin, Damien. "Les billes magnétiques comme capteurs de force : application à la pression de croissance de filaments d'actine". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2012. http://pastel.archives-ouvertes.fr/pastel-00733095.
Pełny tekst źródłaRouag, Nadjet. "Influence de la texture cristallographique et de la spécialité des joints de grains sur l'anisotropie de migration des joints entourant un grain d'orientation (110)<001> au cours des premiers stades de la recristallisation secondaire dans les toles de Fe-3% SI en présence de précipités AIN et MnS". Paris 11, 1988. http://www.theses.fr/1988PA112364.
Pełny tekst źródłaDe, Vet Christiaan J. F. "Auto-assemblage d'un anthacène fluorescent aux échelles nano- et micrométriques par photoréaction contrôlée". Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0333/document.
Pełny tekst źródłaThe spatial and temporal control of the self-assembly of fluorescent molecules into organized nano-objects and into soft materials was achieved by photochemistry. The quantitative photodecarbonylation of the progelator dkDDOA under irradiation generates the supergelator 2,3-didecyloxyanthracene (DDOA) at room temperature and simultaneously gelates DMSO. dkDDOA is reactive under excitation withblue light due to the light sensitive alpha-diketone moiety that is added to the aromatic core.Additional colour-tuning from blue to green emission from the gel was achieved by adding a similar photoreactive 1,2-diketone-5,12-diphenyltetracene that yields a green emissive 5,12-diphenyltetracene sensitized through an efficient energy transfer. Under a microscope, focused laser irradiation enables the patterning of blue-emissive nanofibers on to a glass surface. Although the surface is non-treated, micropatterns of highly aligned DDOA nanofibers can be obtained. These surfaces emit linearly polarized blue light,as proven with polarization microscopy. The high anisotropy and the orientation of the fibers was achieved by controlling the nucleation density and the direction of scanning of the focused laser. Perpendicularly oriented micropatterns can thereby be juxtaposed on the same surface
Msellak, Khalid. "Electrodéposition métallique sous contrôle MHD : caractérisation physique et électrochimique". Reims, 2003. http://www.theses.fr/2003REIMS008.
Pełny tekst źródłaThis work analyzes the influence of a magnetic field parallel to the electrode on two electrochemical systems of industrial interest : the deposit of Cu on substrates inducing no epitaxy and deposits of Ni-Fe alloys. The characterization of the deposits was led with several physical and electrochemical techniques. The results show that : The magnetic field does not modify the nucleation of Cu on a conductive substrate (glassy C or Ti) : the only measurable results are the magneto-induced convective effects on the growth of Cu. On TiO2, a phenomenon of anisotropy confirms the existence of a transverse electric field. The phenomenon, sensitive with moderate fields, was put in evidence in a spectacular way under the intense fields available on the LMCI of Grenoble. For electrodeposition of Ni-Fe alloys, the results show that the magnetic field increases the convective rate of the ferrous ions to the electrode. These species inhibit the Ni deposit and lead to alloys considerably enriched in Fe
Favier, Stéphane, i Gilles Canova. "Contribution à l'étude de l'endommagement de matériaux métalliques contenant des particules dures : application à l'alliage d'aluminium 3004-H19". Grenoble INPG, 1995. http://www.theses.fr/1995INPG0174.
Pełny tekst źródłaMüller, Pierre. "Phase ordonnee anisotrope dans un film de langmuir : morphologie, croissance et tension de ligne". Paris 6, 1991. http://www.theses.fr/1991PA066588.
Pełny tekst źródłaAngelo, Da Silva Monique. "Tensioactifs hydroxylés comme agent de croissance pour la synthèse de nanoparticules anisotropes d’or". Rennes, Ecole nationale supérieure de chimie, 2014. http://www.theses.fr/2014ENCR0019.
Pełny tekst źródłaGold nanorods (AuNRs) have attracted great interest owing to their particular optical properties, strongly dependent on the size and aspect ratio (thickness/length), and thus their potential applications in optics and medicine (therapy, cancer diagnosis. . . ). In this context, the development of new strategies for the synthesis of anisotropic nanorods with high yields and selectivities remains a challenge towards an effective control of the size and morphology. Among the different preparation routes, the seed mediated method is most commonly used, especially in the presence of cetyltrimethylammonium bromide (CTAB) as a growth-driving agent. To our knowledge, few works have been reported in the literature in presence of other growth driving agents. In this context, we have developed a novel family of growth driving agents, N,N-dimethyl-N-cetyl-N-hydroxyalkylammonium salts (HAAX), producing gold nanorods with high yields and selectivities in water. These surfactants have good solubility in water and are easily synthesized in good yields and different structural parameters could be modulated such as : i ) the length of the lipophilic chain (C12 , C16 , C18), ii ) the nature of the counter ion by anionic metathesis (X- = F-, Cl-, Br-, I-, HCO3 - and BF4 -), and more particularly iii) the hydroxylated polar head. The gold nanoparticles obtained by the seed mediated method were characterized by UV -vis spectroscopy and transmission electron microscopy, showing the influence of the surfactant on the morphology and on the size (aspect ratio). Thus, this family of easily tunable ammonium salts allows access to various shapes and sizes of gold nanoparticles according to the desired target and opens interesting perspectives in terms of applications
Chen, Gwennaëlle. "Rôles de polygalacturonases (PG) dans le développement racinaire, chez Arabidopsis thaliana". Thesis, Amiens, 2018. http://www.theses.fr/2018AMIE0022/document.
Pełny tekst źródłaPlant cell wall structure is modified to control its stiffness or flexibility according to plant’s requirements. The cell wall is a complex structure, composed of cellulose, hemicelluloses and pectins. Pectin modifications during cellular elongation are not very well characterized. In this context, the aim of this project is to study the roles of two polygalacturonases (PG) in the root development on the model plant A. thaliana. PG are homogalacturonans (HG) degradation enzymes, HG being the major pectic component of the primary cell wall. This degradation would lead to a local parietal relaxation, allowing anisotropic growth of the cells. Our results show that the two studied PG, named PG ROOT APICAL MERISTEM (PG RAM) and PG ROOT (PG R), are expressed in complementary areas of the root, either in the root apical meristem (PG RAM) or in the elongated and differenciated root tissues (PG R). Furthermore, the over-expression of PG R results in longer etiolated hypocotyls and increases root density when compared to wild-type, demonstrating its function in root development and in cell elongation. Finally, we demonstrated that expression of these two PG genes is under the control of PLETHORA (PLT) family transcription factors, by differentially ways
Génevaux, Jean-Michel. "Le fluage à température linéairement croissante : caractérisation des sources de viscoélasticité anisotrope du bois". Phd thesis, Institut National Polytechnique de Lorraine - INPL, 1989. http://tel.archives-ouvertes.fr/tel-00354640.
Pełny tekst źródłaAppliquée à trois essences de bois (peuplier, douglas et hêtre), de la pâte à papier et du hêtre acéthylénisé, l'expérience met en évidence des anisotropies différées du bois supérieures à l'anisotropie élastique. Un accroisssement d'humidité modifie la cinétique des mécanismes. Les anisotropies et les influences des taux d'humidité induisent des hypothèses quant à la localisation des sourcres de fluage dans la matrice, les renforts ou les interfaces de ce composite.
Genevaux, Jean-Michel. "Le fluage à température linéairement croissante : caractérisation des sources de viscoélasticité anisotrope du bois". Vandoeuvre-les-Nancy, INPL, 1989. http://www.theses.fr/1989NAN10017.
Pełny tekst źródłaGenevaux, Jean-Michel. "Le Fluage à température linéairement croissante caractérisation des sources de viscoélasticité anisotrope du bois /". Grenoble : ANRT, 1989. http://catalogue.bnf.fr/ark:/12148/cb37613801v.
Pełny tekst źródłaMc, Grath Oran F. K. "Structural and magnetic properties of epitaxial W/Fe/W and Gd/Fe films grown by pulsed laser deposition". Université Joseph Fourier (Grenoble), 1994. http://www.theses.fr/1994GRE10209.
Pełny tekst źródłaEl, Haj Kacem Maher. "Visco-plasticité de transformation de phase diffusive : modélisation numérique et caractérisation des effets de la viscosité". Thesis, Rouen, INSA, 2016. http://www.theses.fr/2016ISAM0007.
Pełny tekst źródłaIn this study, the mechanical consequences of phase transformations in steel, particularly, the TRansformation Induced Plasticity TRIP as well as the elasto-viscoplastic behavior has been analyzed. This transformation plasticity, due to the Greenwood-Johnson mechanism, is often described with the model of Leblond with the assumption of an elastoplastic behavior. Moreover, in the majority of experimental analysis or numerical finite elements modeling FEM or phase field modeling PFM, the viscous criteria were not considered. However, several recent studies have demonstrated that both phases (parent and product) show high strain-rate sensitivity at elevated temperatures. Hence, the principal interests using the FEM modeling to extend these main reference models of [Leblond, 89] and [Taleb-Sidoroff, 2003], with taking into account the viscous effects, which are present during some phase transformations, especially at high temperatures. To do this, the behavior of each phase is described by an elasto-viscoplastic law with mixed hardening associated to the Norton law. The transformation kinetics is imposed and the problem of mechanical interactions between phases is processed by the finite element method. On the one hand, the contribution from viscosity to TRIP was quantified for different strain-rate during phase transformation. On the other hand, the effect of an arbitrarily-set of transformation-rate in the FEM simulations was evaluated and characterized. An extension of the existing models (for periodic and random kinetics) is proposed. It consists at first in studying and in evaluating the effect of both the morphology of nuclei and the growth anisotropy, on the prediction of TRIP. Then, an improvement with non-isothermal model, based on existing experimental measures, was introduced. It consists mainly in taking into account the variation of the mechanical properties of the mixture of both phases, according to the temperature. The predictions show that in such cases, the consideration of the viscosity can lead to major changes of the estimated TRIP compared with results obtained from a classic plastic model. Also, the prediction of TRIP can be significantly influenced by the choice of the morphology of germs and by the type of growth: isotropic or anisotropic. These improvements, particularly with the non-isothermal configuration, show a good agreement with experimental measures of TRIP on the 10006 steel during pearlite phase transformation [Tahimi, 2012]. This study allows besides, releasing obvious trends in the relations between the TRIP and the history of the phase transformation: mechanical loading and kinetics of transformation, morphology of nuclei and growth anisotropy. These results can contribute to the elaboration of a simple analytical model taking into account the viscous criteria
Ung, Diane. "Nanoparticules métalliques anisotropes synthétisées par voie chimique : fils, plaquettes et particules hybrides de cobalt-nickel, propriétés structurales et magnétiques ; fils d'argent auto-organisés". Phd thesis, Université Paris-Diderot - Paris VII, 2005. http://tel.archives-ouvertes.fr/tel-00202393.
Pełny tekst źródłaPour le système cobalt-nickel, l'analyse des différents paramètres de la réduction en milieu polyol indique que la concentration de soude et la composition cobalt-nickel sont des facteurs clefs pour contrôler la morphologie des particules. Différentes formes ont été synthétisées : des fils nanométriques de 8 nm de diamètre, des plaquettes mais aussi des particules de formes plus originales telles que des haltères. Les variations de morphologie sont marquées par des modifications structurales et des différences de compositions chimiques locales. Les fils se développent suivant l'axe c de la structure hexagonale et les extrémités des particules sont souvent enrichies en nickel. Les études magnétiques de ces particules montrent que les variations des propriétés magnétiques sont intimement liées à leur forme. L'analyse du système avant réduction révèle que l'origine de ces formes résulte d'une différence de réactivité du cobalt et du nickel dans le milieu.
En ce qui concerne la formation induite par un template, des fils métalliques de 6 nm et de longueurs microniques alignés en 2D ont pu être synthétisés un milieu biphasique polyol/toluène. Ils proviennent certainement d'une organisation et d'une coalescence orientée de particules d'argent le long des fibres de thiolate d'argent.
Ung, Diane. "Nanoparticules métalliques anisotropes synthétisées par vie chimique : fils, plaquettes et particules hybrides de cobalt-nickel, caractérisations physico-chimiques et propriétés magnétiques : fils d'argent auto-organisés". Paris 7, 2005. https://tel.archives-ouvertes.fr/tel-00202393.
Pełny tekst źródłaSaliba, Sarmenio. "Thermotropic and lyotropic liquid crystals for the formation of zinc oxide nanohybrids". Toulouse 3, 2011. http://thesesups.ups-tlse.fr/1598/.
Pełny tekst źródłaThe work presented in this manuscript describes the incorporation of inorganic materials inside organic hosts. Our ambition was to successfully hybridize ZnO nanostructures with liquid crystals. This was achieved using different strategies, the choice of which depended on the desired properties of the final material. The objective was not only the synthesis and stabilization of the nanoparticles within, but also their organization in the LC medium. One approach was the functionalization of preformed ZnO spherical nanoparticles by thermotropic LC ligands. This was made possible using a ligand exchange mechanism. Due to a dynamic equilibrium at the surface of ZnO NPs, the mesogenic molecules could exhibit order at the molecular level, giving rise to novel LC/NP hybrids with enhanced LC properties. The organization of NPs could also be induced by the use of lyotropic liquid crystals. In this case, the NPs were not simply doped into a LC material, but synthesized directly inside the lyotropic phases. The synthesis of ZnO was therefore confined to domains of defined size and shape which can directly control the organization of the nanostructures growing within. Apart from organization of NPs, our constant objective was the fabrication of anisotropic nanoobjects via LC-assisted synthesis. Thermotropic liquid crystals consisting of novel low molecular weight branched mesogens have proved to be remarkable templates for anisotropic growth of ZnO nanocrystals. This anisotropic growth was also found to be influenced by the size of the LC molecules as observed with the fabrication of ZnO inside LC polymers. This work has shown the possibility of integrating inorganic material in LCs providing that the two constituents are able to sufficiently interact with one another
Moukarzel, Waêl. "Synthèse et caractérisation de glycosilicones et leur application à la préparation et stabilisation de nanoparticules d'or". Toulouse 3, 2011. http://thesesups.ups-tlse.fr/1628/.
Pełny tekst źródłaCoupling a siloxane chain with various functional groups leads to polymers with new properties combining the flexibility of the chain with the properties of the functional groups. Accordingly, we wanted to study the grafting of saccharide groups on polysiloxane polymers. In the first part of this thesis, a new, smooth, efficient and fast method has been developed for the preparation of linear or hyperbranched polysiloxanes with lateral or terminal sugar groups. The preparation is done without the use of protecting groups for sugars. It avoids the use of acid or alkaline conditions for the deprotection thus preventing the decomposition of the siloxane chains before and after grafting the sugars. The polymers were characterized by 1H, 13C, 29Si NMR, IR and Size Exclusion Chromatography. These "glycosilicones" with grafting rate and weights adjustable at will, were subsequently used to efficiently stabilize preformed gold nanoparticles in aqueous solution even at high ionic strengths. The reducing properties of amino sugars used in this thesis for the synthesis of glycosilicones were used for a direct synthesis of nanoparticles under milder conditions than in conventional synthesis methods (such as reducing the gold salt with sodium borohydride). These amino sugars (glucosamine, glucamine) play the role of both reducing agents and stabilizers in aqueous media. The advantage of this method lies in the use of a single nontoxic reagent which can be useful for using these nanoparticles in biological tests. The one pot synthesis occurs at room temperature and leads to the formation of spherical nanoparticles with a good yield, but also induces anisotropic growth leading to the production of star shaped or multi-branched nanoparticles with very high yields. The size and number of branches of nano-stars were modulated by adjusting the experimental conditions. They were characterized regarding to their morphology, stability and optical properties by electron microscopy and UV spectroscopy
Acher, Olivier. "Mise en oeuvre de la reflectance anisotrope spectroscopique pour l'etude in situ de la croissance des semiconducteurs 3-5 par la methode des organometalliques en phase vapeur". Paris 11, 1990. http://www.theses.fr/1990PA112140.
Pełny tekst źródłaAchkar, Charbel. "Etudes de nanostructures magnétiques auto-organisées et épitaxiées par synthèse organométallique en solution sur des surfaces cristallines". Thesis, Toulouse, INSA, 2014. http://www.theses.fr/2014ISAT0037/document.
Pełny tekst źródłaThe elaboration of this thesis aims to characterize the magnetic and structural properties of magnetic nanostructures obtained by a new mixed physical / chemical synthesis method, called hybrid growth. The first part of the work consists in the development of thin metal films on substrates by cathode sputtering. Furthermore, the chemical synthesis conducted by organometallic chemistry on those thin films, results in an array of ultra-dense Co monocristallins hcp nanowires, or nanostructured Fe films. Additionally, The SEM/TEM observations and the X-ray diffraction measurements conducted on the substrates and induced by the crystlalline structure of the thin film, show the high impact on the magnetic nanostructures morphology and growth direction.Moreover, the magnetic measurements executed on the Co nanowires array show a strong magnetic anisotropy perpendicular to the substrate. This observation is obtained due to the magnetocrystalline anisotropy acting along the nanowire axis (Co hcp structure with the c axis parallel to the nanowire axis) in the same direction of the nanowires shape anisotropy. The magnetization within these structures is thermally stable. It follows a coherent magnetization reversal mode that has not been observed in the polycrystalline structures up to now. Finally, the self-organization of the nanowires as well as their high density and stable magnetization nominate this system for their application in high density magnetic storage devices
Courtois, Pierre. "Elaboration en creuset froid sous champ magnétique intense de quelques matériaux magnétiques en vue de leur texturation". Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10124.
Pełny tekst źródłaMeunier, Anthony. "EPITAXIE DE SYSTEMES METALLIQUES SUR Si(001) : Croissance du cuivre et structures à anisotropie magnétique perpendiculaire (Cu/Ni et FePd)". Phd thesis, 2005. http://tel.archives-ouvertes.fr/tel-00238555.
Pełny tekst źródłaLa dernière partie de ce rapport présente deux études de systèmes à anisotropie magnétique perpendiculaire épitaxiés sur Si(001) : Cu/Ni et FePd. Dans le système Cu/Ni, nous montrons à partir d'expériences de AES et d'un modèle de ségrégation la présence d'une zone d'interdiffusion de 1 à 2 nm qui explique en grande partie la diminution du moment magnétique mesuré sur des couches de nickel de faible épaisseur. Finalement, à partir de la formation contrôlée d'un siliciure de cuivre ou de fer, nous rapportons pour la première fois la possibilité d'épitaxier sur Si(001) des couches d'alliage ordonné L10-FePd(001) présentant une forte anisotropie magnétique perpendiculaire.
Amstatt, Benoît. "Croissance d'hétérostructures non-polaires de GaN/AlN plan m sur 6h-SiC plan m". Phd thesis, 2008. http://tel.archives-ouvertes.fr/tel-00336401.
Pełny tekst źródłaNous avons tout d'abord étudié les couches épaisses d'AlN et de GaN. Les conditions de croissance de ces couches sont optimales en conditions riche métal. Toutes deux présentent des morphologies de surface anisotropes mais différentes l'une de l'autre avec une morphologie de type « tôle ondulée » pour l'AlN et « toît de tuiles » pour le GaN.
Nous nous sommes ensuite intéressés à la croissance d'hétérostructures de GaN/AlN. Nous avons démontré que la croissance de GaN en conditions riche N aboutit à la formation de puits quantiques de GaN tandis que la croissance en conditions riche Ga permet de former des fils ou des boîtes quantiques par le mode de croissance Stranski-Krastanow. Nous avons démontré que cette différence de morphologie pour les nanoobjets de GaN était liée à l'état de relaxation de la couche tampon d'AlN. Des études optiques ont mis en évidence une forte réduction du champ électrique interne dans les hétérostructures de GaN/AlN plan m.
Pour finir, nous avons étudié l'évolution de la morphologie des fils et des boîtes en fonction de la quantité de GaN déposée. Nous avons démontré l'existence d'une transition de forme ''boîtes-fils'' lorsque l'aire des boîtes excède une taille critique. Cette aire peut être contrôlée par la quantité de matière déposée mais également par la réalisation de superréseaux.