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Elaboration de poudres inorganiques nanostructurées en milieux fluides supercritiques

Abstract : Since 1980, new materials elaboration processes are developed using supercritical fluids. This work deals with a new route of fine particles synthesis based on the thermal decomposition of precursors in supercritical conditions. Firstly, we review the different processes concerning materials elaboration in supercritical fluids. Then, we present two new ways of powder synthesis : a batch process and a continuous process. The control of some parameters (as the solvent nature, the initial precursor concentration, the reactional medium viscosity, the residence time) permits to get a wide range of materials (Cu3N, Cu2O, Cu) with different size, shape and structure. Our results allow to develop a model of particle growth, in supercritical conditions, from the metallic nuclei birth to the micronic particles formation. This model is validated by a numerical simulation developed during this work. It confirms that the growth is based on the Brownian coalescence between two particles. In a second part, we present a new promising process of coating powder in supercritical conditions which is illustrated by two examples of core-shell structures elaboration. The coating of nickel particles by copper reveals the influence of the copper layer on the magnetic properties of the core materials. The second example deals with the realization of SmCo5/Cu structure in order to develop new magnetic recording supports. In a first part, the elaboration of the initial SmCo5 particles by mechanical grinding is described. The influence of both the milling time and the milling speed on the SmCo5 properties are studied. In a second part, the coating of the milled SmCo5 particles is presented and the magnetic properties of the new SmCo5/Cu are discussed.
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https://tel.archives-ouvertes.fr/tel-00003497
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Submitted on : Tuesday, October 7, 2003 - 6:27:00 PM
Last modification on : Thursday, January 11, 2018 - 6:15:07 AM
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  • HAL Id : tel-00003497, version 1

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Vincent Pessey. Elaboration de poudres inorganiques nanostructurées en milieux fluides supercritiques. Autre. Université Sciences et Technologies - Bordeaux I, 2000. Français. ⟨tel-00003497⟩

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