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Modélisation globale de l'infiltration chimique en phase vapeur (CVI) et étude de la chimie du dépôt de pyrocarbone en CVD/CVI

Abstract : This dissertation deals with the modelling of the chemical vapor infiltration (CVI) process which is used to manufacture thermostructural composite materials such as carbon-carbon (C/C). Two issues are addressed : the first one deals with the development of a global simulation tool of the process, the second one with the determination of a chemical model suitable for a realistic description of pyrocarbon deposition, yet simple enough to be used in a global simulation. The global modelling includes a detailed mathematical description of mass (convection and multicomponent diffusion) and heat transfers, homogeneous and heterogeneous chemical reactions, and interfacial relations between free medium (the chamber) and porous medium (the preform). Then, a global computational tool was developed with coupled resolutions of the two problems (free medium / porous medium). Potentialities of this quantitative approach are illustrated through a modelling study of the CVI of silicon carbide, with variation of the reactive gas flow rate and the reactor diameter. A chemical model for pyrocarbon deposition from propane is then proposed, featuring two light average species leading to smooth laminar pyrocarbon and one heavier average species (PAH) leading to rough laminar pyrocarbon. It agrees with experimental CVD results. In order to identify it also in CVI cases, model porous media made of quasi-compact stacks of filaments have been elaborated, densified and characterized. It has been necessary to refine the chemical model in order to obtain an agreement with these CVI experimental results. Finally, a comparison between results of CVD and CVI experiments in various conditions and the modelling frame allowed to a better interpretation of the former : the presence of a new deposition mode of highly anisotropic pyrocarbon has been confirmed.
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Contributor : Nicolas Reuge <>
Submitted on : Sunday, November 16, 2003 - 6:40:19 PM
Last modification on : Saturday, December 21, 2019 - 1:39:08 AM
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Nicolas Reuge. Modélisation globale de l'infiltration chimique en phase vapeur (CVI) et étude de la chimie du dépôt de pyrocarbone en CVD/CVI. Matériaux. Université Sciences et Technologies - Bordeaux I, 2002. Français. ⟨tel-00003765⟩

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