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Etude des mécanismes de montée capillaire du silicium liquide au sein d'une préforme en carbure de silicium

Abstract : The development of aeronautic engines increased the need in high temperature SiC/SiC composite researches. A standard way to proceed is to infiltrate the matrix by chemical vapor infiltration. Due to their high porosity, their thermal conductivity is generally low. This could lead to strong thermal gradients and an early failure in a harsh environment. To reduce porosity, an alternative process can be used: the infiltration of molten silicon (MI: Melt Infiltration). The aim of this work is to understand all mechanisms occurring during the infiltration of silicon in a fibrous preform composed of SiC Hi-Nicalon S fibers. This process needs a first step which consists in the introduction of SiC particles into the preform before the MI process.First, this work focused on the definition of the porous structure of studied materials and capillarity tests using wetting organic solvent. With the use of Washburn’s law, it was possible to identify pore sizes within the fibrous preform and the granular matrix, and so to predict the capillarity ascent graphs of molten silicon into our material. A second part was devoted to the conception of an infiltration furnace which allows in situ following of the samples weight gain. The correlation between graphs obtained with the Washburn model and the experimental process could be established. Finally, the last part of this work presents partial infiltrations of molten silicon into studied materials which permit to identify capillary mechanisms occurring during the MI process.
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  • HAL Id : tel-03196599, version 1

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Alexandre Marchais. Etude des mécanismes de montée capillaire du silicium liquide au sein d'une préforme en carbure de silicium. Chimie-Physique [physics.chem-ph]. Université de Bordeaux, 2016. Français. ⟨NNT : 2016BORD0025⟩. ⟨tel-03196599⟩

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