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Laamyem, Abdessadeq. "Chloroadamantane-bromoadamantane : deux exemples de transitions de phase ordre-désordre". Lille 1, 1986. http://www.theses.fr/1986LIL10077.
Stephan, Baptiste. "Etude cinétique et microstructurale de la transformation ordre-désordre dans les alliages Ni2Cr à faible teneur en fer". Thesis, Lille 1, 2018. http://www.theses.fr/2018LIL1R004/document.
Chemical ordering in Ni-Cr alloys modifies their mechanical properties and is a potential issue for their use in pressurized water reactors. In this work, ordering kinetics have been determined by accelerated ageing on model alloys with low iron content. The Ni2Cr ordered phase appearance induces a hardness increase. Furthermore, thermoelectric power measurements have been revealed very sensitive to ordering. The iron content does not affect ordering kinetics at low temperatures (<450 °C), contrary to thermal treatments practiced on the alloys. Our results have been extrapolated to the industrial case, where the iron content is higher: ordering incubation time is estimated at 140 years at 325 °C. The nanometric size of ordered domains together with their small difference in chemical composition with the disordered matrix make their study difficult. We used advance characterizations with transmission electron microscopy to progress in their description. Thanks to the coupling of image analysis with orientation mappings, the surface proportion of ordered domains has been estimated on a control sample. Energy loss chemical maps reveal that the iron is partly segregated around ordered domains. This questions the state of order of the Ni2Cr phase, which is corroborated by quantitative microdiffractions achieved on ordered domains. At the atomic scale, analyzes show that iron substitutes preferentially for chromium in the ordered phase
Stephan, Baptiste. "Etude cinétique et microstructurale de la transformation ordre-désordre dans les alliages Ni2Cr à faible teneur en fer". Electronic Thesis or Diss., Université de Lille (2018-2021), 2018. http://www.theses.fr/2018LILUR004.
Chemical ordering in Ni-Cr alloys modifies their mechanical properties and is a potential issue for their use in pressurized water reactors. In this work, ordering kinetics have been determined by accelerated ageing on model alloys with low iron content. The Ni2Cr ordered phase appearance induces a hardness increase. Furthermore, thermoelectric power measurements have been revealed very sensitive to ordering. The iron content does not affect ordering kinetics at low temperatures (<450 °C), contrary to thermal treatments practiced on the alloys. Our results have been extrapolated to the industrial case, where the iron content is higher: ordering incubation time is estimated at 140 years at 325 °C. The nanometric size of ordered domains together with their small difference in chemical composition with the disordered matrix make their study difficult. We used advance characterizations with transmission electron microscopy to progress in their description. Thanks to the coupling of image analysis with orientation mappings, the surface proportion of ordered domains has been estimated on a control sample. Energy loss chemical maps reveal that the iron is partly segregated around ordered domains. This questions the state of order of the Ni2Cr phase, which is corroborated by quantitative microdiffractions achieved on ordered domains. At the atomic scale, analyzes show that iron substitutes preferentially for chromium in the ordered phase
Chafi, Allal. "Les phonons : un 'mésoscope' naturel pour l'étude du désordre d'alliage". Thesis, Metz, 2008. http://www.theses.fr/2008METZ034S/document.
We demonstrate how to overcome serious problems of understanding and classifcation of vibration spectra in semiconductor alloys, following from traditional use of the Virtual Cristal Approximation (VCA). We show that such different systems as InGaAs (1- bond!1-phonon behavior), InGaP (modifed 2-phonon) and ZnTeSe (2-bond 1-phonon) obey, in fact, the same phonon mode behavior, hence probably a universal one, of a percolation type (1-bond!2-phonon, developed in our group). The change of paradigm from the VCA (macroscopic scale) to the Percolation (mesoscopic scale) reveals a specificity of zone-center phonons, that is to provide natural insight into the alloy disorder at the unusual mesoscopic scale. In fact, we introduce a terminology, and say that these phonons behave as a true 'MESOSCOPE'. In particular, this opens up new perspectives for studying the effects of long-range spontaneous organization in mixed crystals, ranging from segregation (InGaP2) to anti-segregation (GaInAsN)
Leduc, François-Xavier. "Etude du processus de mise en ordre des tétratèdres ZnCl4, en corrélation avec la séquence de transitions de phases modulées dans K2ZnCl4". Lille 1, 1997. http://www.theses.fr/1997LIL10106.
L'observation d'une configuration ordonnée à longue portée des tétraèdres dans les phases désordonnées est l'un des résultats les plus originaux du travail. L'analyse détaillée du profil de la diffusion diffuse a révèlé la mise en ordre locale des tétraèdres à l'intérieur de clusters distribués irrégulièrement au sein d'une matrice ordonnée, dans la phase finale du processus de mise en ordre. Un ordre à longue portée des tétraèdres a été également observé dans les phases désordonnées de Rb2ZnCl4 et Cs2ZnCl4 qui présentent un degré de désordre orientationnel moins élevé que K2ZnCl4. L'arrangement de la configuration ordonnée des tétraèdres est discuté en fonction du degré de désordre des composés, et montre que les effets de volume ne sont pas la seule origine des défauts de structure
Pochet, Pascal. "Etude expérimentale et modélisation des changements de phases sous broyage à haute énergie". Lille 1, 1997. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/1997/50376-1997-37.pdf.
Wang, Yimi. "Modélisation atomique des propriétés thermodynamiques, de la diffusion et de la mise en ordre dans les alliages Fe-Ni". Electronic Thesis or Diss., Centrale Lille Institut, 2021. http://www.theses.fr/2021CLIL0036.
We present an atomic-scale modeling of thermodynamic properties, diffusion and ordering kinetics in iron-nickel alloys of face-centered cubic structure. The model uses pair interactions that depend on temperature and local composition. These pair interactions are fitted to ab initio calculations at 0 K, and to experimental data at non-zero temperatures. The phase diagram of the system is constructed and compared to the experimental phase diagram. All known experimental diffusion coefficients are well reproduced: self-diffusion, impurity diffusion coefficients in dilute alloys, tracer and interdiffusion coefficients in concentrated alloys. The ordering kinetics in the FeNi3 alloy are studied and compared to available experiments. A good agreement is obtained for the evolution of the long-range order parameter and for the evolution of the size of the ordered domains
Roulin, Gilles. "Etude des premiers stades de mise en ordre dans les alliages martensitiques du système cuivre-aluminium". Rouen, 1997. http://www.theses.fr/1997ROUES085.
Chbihi, Abdelahad. "Etude de l'effet d'une déformation plastique préalable sur les transformations de phases dans les alliages modèles : CuCr et FePd". Phd thesis, Rouen, 2011. http://www.theses.fr/2011ROUED005.
The application of severe plastic deformation on metal alloys usually leads to the reduction of the grain size and the formation of a high density of defects (dislocations, vacancies, grain boundaries, etc. ), pushing systems far from thermodynamic equilibrium. This can affect the stability of microstructures and influence the mechanisms of phase transformations. The aim of this work is to understand the effect of prior plastic deformation on two kinds of phase transformations: precipitation and ordering. For this, two model alloys were chosen: CuCr1 and Fe50Pd50 For the CuCr1, the early stages of the Cr precipitation in Cu were first investigated in the undeformed state. Atom Probe Tomography and Transmission Electron Microscopy clearly show the coexistence of three kinds of Cr rich precipitates. Both their structure and composition were investigated in detail. The precipitation kinetic was modeled on the basis of thermodynamic arguments, taking into account the different energy terms, i. E. Driving force, elastic energy and interfacial energy, which come into competition during the Cr precipitation in Cu. The large deformation (by rolling) of the CuCr1 alloy leads to an acceleration of the precipitation kinetic due to the heterogeneous nucleation of Cr precipitates on dislocations. For the Fe50Pd50 alloy, the effect of plastic deformation by High Pressure Torsion on the ordering mechanism was investigated. Transmission Electron Microscopy observations showed that the ordering process in the ultrafine grained state is associated with the recrystallization. The ordered domains nucleate at grain boundaries and grow at the expense of non-recrystallized grains. It should be noted that, a record coercive field was obtained for this alloy in the nanostructured state
Chbihi, Abdelahad. "Etude de l'effet d'une déformation plastique préalable sur les transformations de phases dans les alliages modèles : CuCr et FePd". Phd thesis, Université de Rouen, 2011. http://tel.archives-ouvertes.fr/tel-00648671.
Belkasri, Abdelkhalek. "Antiferromagnétisme et corrélations fortes dans les supraconducteurs à haute température". Aix-Marseille 1, 1994. http://www.theses.fr/1994AIX11030.
Neacsa, Iurcut Daniela Maria. "Propriétés structurales et magnétiques de ferrites de gallium substituées par des terres rares". Thesis, Tours, 2016. http://www.theses.fr/2016TOUR4013/document.
We present an experimental contribution to the study of structural and magnetic properties for gallium ferrites substituted by rare earth elements. This work is part of the more general theme of magnetoelectric multiferroïc which includes the Ga2-xFexO3 compound ferrimagnetic and with a spontaneous polarization at room temperature. We study the influence of the substitution of gallium or iron atoms with rare earth elements (Sc, Yb, Er, Sm) on the structural parameters of Ga2-xFexO3 with 0.9 x 1.2 and the effect of the substitution by Sc and Yb on the magnetic transition temperature and the saturation magnetization. We present an experimental study of magnetism Ga0.99Yb0.01FeO3 compound, realized from alternative susceptibility and magnetization measurements as a function of magnetic field, H, and the temperature T. A wide irreversible magnetic area is observed in the phase diagram H–T. The results suggest that Ga0.99Yb0.01FeO3 is a three-dimensional Heisenberg spin glass
Bessenay, Gilles. "Mesures d'intensité diffuse sur monocristal en rayonnement synchrotron : mise en place de l'appareillage et tests, aspects structuraux et cinétiques de l'ordre local dans les alliages Au-Cu". Paris 6, 1986. http://www.theses.fr/1986PA066019.
Guengard, Hélène. "Transitions de phases structurales dans des elpasolites fluorées". Phd thesis, Université Sciences et Technologies - Bordeaux I, 1994. http://tel.archives-ouvertes.fr/tel-00140033.
Andriamiharintsoa, Tsiky Hasiniaina. "Etude de la tendance à l'ordre dans les nanoalliages métalliques à partir de leur structure électronique". Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAE032/document.
The purpose of this thesis work is to determine, by using the tight-binding formalism, the link between atomic, chemical and electronic structures of nanoalloys focusing on two systems, characteristic on one hand of a strong order tendency (cobalt-platinum, CoPt) and, on the other hand, of a strong tendency to phase separation (iridium-palladium, IrPd). For both CoPt and IrPd, the evolution of the local densities of states (LDOS) as a function of the site coordination (structural effect), the chemical environment (alloy effect) and the size of the systems has been analyzed in detail. CoPt and IrPd have a same behavior concerning the d band shifts which is explained by a rule of charge preserving per species, per site and per orbital between mixed systems and corresponding pure systems. In pure Ir and Pd nanoalloys, the d band centers are found to vary linearly with the site coordination. In IrPd, a linear behavior is also observed, the corresponding line being only rigidly shifted with regards to the pure materials. This decoupling between structural and chemical effects, already observed for CoPt nanoalloys, is here generalized since it applies regardless the tendency of the system to order or to phase separate. Concerning the chemical tendency, CoPt remains a system with order tendency whatever the atomic configuration. In the same way, IrPd remains a system with a tendency to phase separation on the whole range of studied configurations although not so clearly defined in the dilute alloys. We have therefore investigated another dilute systems based on AuNi. In this case, a change of trend is observed going from phase separation for concentrated systems to order tendency for dilute systems, including thin layers at surfaces. Complementary structural studies have been performed by using Monte Carlo simulations, first on a rigid lattice and then including atomic displacements. The results show that nanoparticles of IrPd are core-shell with a strong Pd segregation at the surface. The core of nanoparticle is generally off-centered despite the very small atomic size effect between Pd and Ir atoms
Combet, Jérôme. "Désordre moléculaire dans les composés d'inclusion du tano : une approche par diffusion des rayons X et diffusion quasi élastique incohérente des neutrons". Université Joseph Fourier (Grenoble ; 1971-2015), 1997. http://www.theses.fr/1997GRE10185.
Vernyhora, Iryna. "Modélisation à l'échelle atomique de l'évolution microstructurale dans les alliages Ni-Fe : corrélation entre les propriétés magnétiques et structurales". Phd thesis, Rouen, 2009. http://www.theses.fr/2009ROUES022.
Fe-Ni alloys are widely used due to their interesting fundamental properties which arise from the coexistence of the chemical and magnetic order. The aim of this work was to understand the mutual influence of these two types of ordering on the thermodynamic and kinetic processes in Permalloys (Ni3Fe). From Monte Carlo and Mean Field simulations the effect of the magnetic interactions on the order/disorder transition temperature has been observed, and reciprocally the influence of the chemical interactions on the Curie temperature. The kinetics of the precipitation has been studied by means of the Onsager microdiffusion equation using parameters extracted from ab-initio calculations. These simulations have evidenced the influence of the magnetic interactions on the formation of the stable L12 particles. Both thermodynamic and kinetic investigations have confirmed the importance of taking into account simultaneously both magnetic and chemical interactions. The obtained results agree well with the available experimental data
Vernyhora, Iryna. "Modélisation à l'échelle atomique de l'évolution microstructurale dans les alliages Ni-Fe : Corrélation entre les propriétés magnétiques et structurales". Phd thesis, Université de Rouen, 2009. http://tel.archives-ouvertes.fr/tel-00430789.
Atmani, Hassane. "Investigations dans le domaine des comportements thermiques de matériaux désordonnés : application au sélénium et aux mélanges Se-Bi à faible concentration en bismuth". Rouen, 1988. http://www.theses.fr/1988ROUES009.
Pouget, Stéphanie. "Contribution à l'étude de l'influence de la dilution sur les propriétés magnétiques de composés isolants frustrés". Toulouse, INSA, 1993. http://www.theses.fr/1993ISAT0039.