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Quantification et correction des biais inhérents à l'analyse par sonde atomique tomographique des nano-particules d'un acier ODS : Application à l'étude de leur formation et de leur comportement sous irradiation

Abstract : ODS (Oxide Dispersion Strenghtened) steels are promising candidates for future nuclear reactors, thanks in part to the thin dispersion of nanoparticles they contain. This study is part of the CPR ODISSEE, whose objective is to federate the theoretical and experimental investigation methods of different French laboratories, from the atomic scale to the mechanical properties, around the same ODS steel, to optimize its microstructure and to understand its properties and behavior. Until now, there was no consensus on the nature of the nanoparticles because of their analysis pushing the techniques to their limits. The first objective of this thesis was to understand the biases inherent in the analysis of these particles by atom probe tomography (APT) in order to determine their characteristics. Coupling APT with transmission electron microscopy and numerical simulation of field evaporation was used. An analytical model, developed during this work, corroborated experimentally and by simulation, has made it possible to correct the biases inherent in the APT analysis of ODS steel particle. The corrected data indicate that these particles are yttrium and titanium oxides, of cubic form, with a pyrochlore structure, whose stoichiometry evolves with size. They are surrounded by a shell enriched with Cr. The studied steel is obtained by mechanical alloying of powders and then hot extruded (1100° C). The second objective of this thesis was to study the formation of nanoparticles during the elaboration stagesand then their stability in temperature and under irradiation. All the Y, Ti and O atoms are in solid solution after mechanical alloying. A thin and dense dispersion of oxides precipitates during the hot extrusion step. These oxides are stable during an annealing of 1 h at 1050 ° C. The particles are also stable under low dose (50dpa) ion irradiation at 500 and 700 ° C. At high temperature (700 ° C) and high dose (270dpa), it is observed a dissolution of particles of less than 2 nm. The remaining particles are yttrium oxides with a Cr-rich shell. Operated by the University of Rouen Specialty Physics-Materials Science Quantification and correction of the bias inherent in tomographic atomic probe analysis of nano-particles of an ODS steel: Application to the study of their formation and their behavior under irradiation Presented and publicly supported by Constantinos HATZOGLOU Thesis directed by Pr. Philippe PAREIGE, co-supervised by Dr. Bertrand RADIGUET
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Constantinos Hatzoglou. Quantification et correction des biais inhérents à l'analyse par sonde atomique tomographique des nano-particules d'un acier ODS : Application à l'étude de leur formation et de leur comportement sous irradiation. Science des matériaux [cond-mat.mtrl-sci]. Université de rouen, 2015. Français. ⟨tel-02108104⟩

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