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Catalycité et vieillissement des matériaux à haute technicité. Etude des barrières de diffusion vis-à-vis de l'oxygène

Abstract : During the atmospheric re-entry phase, the thermal protection of a spacecraft vehicle is submitted to air plasma. The transfer of the kinetic energy of the gases to the surface leads to an important heating of the nose cap and leading edges. The energy released from the recombination of oxygen atoms on the surface produces an additional amount of heat, increasing further the temperature. This excess of heat can damage the protection materials. This study aims to understand the materiel transfer (recombination coefficient γ) and heat transfer (accommodation coefficient β) induces by the atmospheric re-entry. These phenomena are quantified by measuring the catalycity. These measures will be carried out on oxide semiconductor n-type up to 1100 K, with the aim of reducing the atomic oxygen recombination. This leads to surface oxidation and accelerated aging of the surface. In fact, with the use of isotopic oxygen coupled with mass spectrometry, the oxidation (active and passive), ablation and diffusion of oxygen in the bulk of material have been identified. By using SIMS analysis, kinetics of oxygen diffusion will be established in such a layer to test their barrier effect. A new type of deposit (UHTC) possessing resistance to oxidation and diffusion barrier will also be subjected to different thermal treatments (up to 1500 K). Finally this study will be completed by simulation of atomic oxygen recombination using the computer code Chemkin ®.
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Submitted on : Thursday, September 9, 2010 - 4:56:55 PM
Last modification on : Thursday, November 18, 2021 - 4:03:07 AM
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  • HAL Id : pastel-00006059, version 1


Guillaume da Rold. Catalycité et vieillissement des matériaux à haute technicité. Etude des barrières de diffusion vis-à-vis de l'oxygène. Sciences de l'ingénieur [physics]. Chimie ParisTech, 2009. Français. ⟨pastel-00006059⟩



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