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Frittage par Spark Plasma Sintering de céramiques de carbure de bore : modélisation numérique du procédé et optimisation des nano-,microstructures pour l’amélioration des performances des absorbants en réacteurs à neutrons rapides

Abstract : This study aims at developing new boron carbide materials, used as neutron absorbers for fast neutron reactors. The defined strategy is to refine the microstructure to limit the anisotropic swelling of grains under irradiation, responsible for the premature deterioration of pellets. To this end, submicronic and nanometric powders were densified by Spark Plasma Sintering. Two materials were elaborated by Spark Plasma Sintering with submicronic or nanometric microstructures, allowing a reduction in grain sizes compared to the reference material historically used in fast reactors by the CEA. SPS and reference materials were characterized and compared in terms of chemical composition, mechanical and thermal properties. This study led to the selection of the submicronic material and to further investigation regarding flexural strength and thermal shock resistance. The performance was improved compared to the reference. Moreover, the creep behavior at high temperature was characterized and creep parameters were identified. Furthermore, the production of absorbent pellets require to increase the height/diameter ratio compared to classical SPS pellets. Process data necessary for this modeling were obtained using specific thermal and electrical measurements. In addition, the densification parameters of the SPS material were determined from a nonlinear viscous flow model. The thermal, electrical and mechanical phenomena numerically described were then validated by confrontation with experimental monitoring of boron carbide sintering.
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Lena Roumiguier. Frittage par Spark Plasma Sintering de céramiques de carbure de bore : modélisation numérique du procédé et optimisation des nano-,microstructures pour l’amélioration des performances des absorbants en réacteurs à neutrons rapides. Matériaux. Université de Limoges, 2019. Français. ⟨NNT : 2019LIMO0109⟩. ⟨tel-02896704⟩

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