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Étude du séchage au CO2 supercritique pour l'élaboration de matériaux nanostructurés : application aux aérogels de silice monolithiques

Yasmine Masmoudi 1
1 CEP/Sophia
CEP - Centre Énergétique et Procédés
Abstract : Aerogel-like nanostructured materials present a wide set of potential application fields. Among these materials, silica aerogels are known in particular for their thermal super-insulation capability and their transparency in the visible range. Their integration in double-glazing should offer an energetic gain in the building sector, especially through the reduction of heat consumption. For such an application, silica gels synthesised through a sol-gel process, should be dried supercritically in order to obtain large dimensions transparent and monolithic aerogel sheets. This thesis work aims to contribute to the amelioration of the supercritical CO2 drying process efficacity while focusing particularly on the supercritical CO2 washing phase. The phenomena occurring during this phase were studied by coupling experimental and theoretical approaches. The experimental approach is based on the instrumentation of a drying system and notably the implementation of an analysis loop. This metrological tool makes it possible to monitor on line the degree of advancement of the washing phase. The theoretical approach is based on an analytical model coupling diffusion phenomena through the nanoporosity of the gels and mass transfer phenomena in the autoclave. This double approach has allowed firstly to quantify the diffusion phenomena in reference experimental conditions. The effective diffusion coefficient of a model gel nanostructure was so determined. A first estimation of the washing phase duration was also obtained. Secondly, the influence of the variation of silica aerogel nanostructure on the diffusion phenomena was studied. The obtained results have led to a first correlation between the materials permeability and the effective diffusion coefficient. This study has also underlined the interest of an aging treatment by dissolution-reprecipitation phenomena prior to drying in order to shorten the supercritical washing phase duration.
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https://pastel.archives-ouvertes.fr/pastel-00002207
Contributor : Ecole Mines Paristech <>
Submitted on : Tuesday, April 24, 2007 - 8:00:00 AM
Last modification on : Thursday, September 24, 2020 - 5:22:02 PM
Long-term archiving on: : Monday, October 22, 2012 - 4:55:17 PM

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  • HAL Id : pastel-00002207, version 1

Citation

Yasmine Masmoudi. Étude du séchage au CO2 supercritique pour l'élaboration de matériaux nanostructurés : application aux aérogels de silice monolithiques. Sciences de l'ingénieur [physics]. École Nationale Supérieure des Mines de Paris, 2006. Français. ⟨pastel-00002207⟩

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