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Caractérisation optique et géométrique des agrégats submicroniques multi-échelles de particules sphériques très diffusantes

Abstract : Multiscale aggregates (zinc sulfide: ZnS, ...) havephysical and physicochemical properties of great industrial interest (e.g. pharmaceutical industriy, material, environment). The overall objective of this thesis is to characterize these multiscale aggregates by an optical method on the one hand, and a geometric study of the other. The goal is to find simple relations between optical and geometrical properties. The results presented are valid for any material with high refractive index.The first step of this work is to build in a simple way the multiscale aggregate (like ordered arrangement of spherical elementary particles). Different aggregates are then geometrically modeled thanks to predefined design parameters (e.g. particles radius, aggregates overall volume). A preleminary analysis of optical and geometrical analysis is then performed to determine the relevant parameters: the average scattering cross section (...), calculed using a generalization of the Mie theory (GMM for Generalized Multiparticle Mie) developped by Y.L. Xu, and specific geometric values features. An analysis of the behavior of the optical parameter and the geometrical characteristic (e.g. compactness, volume of matter...), with respect to the construction parameters of the aggregates, is then performed.A second step is to study variations of ... value versus the variation of the geometrical parameter of aggregates. Mathematical relations characterizing these variations are established. Finally, a study on the approximation of the ... value is carried out. A power law is proposed which is basedon previous optical approximate methods and on the selection of geometrical characteristics of the aggregates. The optical properties and geometrical characteristics of the clusters are fairly extensive and contrasted to give a general groundwork to this study. The work done opens various perspectives such as the confrontation of the theorical mathematical model obtained, with experiment.
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Marthe Lagarrigue. Caractérisation optique et géométrique des agrégats submicroniques multi-échelles de particules sphériques très diffusantes. Autre. Ecole Nationale Supérieure des Mines de Saint-Etienne, 2011. Français. ⟨NNT : 2011EMSE0607⟩. ⟨tel-00715897⟩

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