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Compaction conventionnelle et compaction grande vitesse (CGV) de céramiques : influence du procédé de compactage sur le frittage

Abstract : The properties enhancement of ceramic compacts can be reached with a better understanding of phenomena that occur during compression and sintering. Ceramic compacts are classically formed by quasi-static uniaxial pressing (conventional pressing) in steel or carbide die. But an impact forming method, High Velocity Compaction (HVC), used for elaboration of ceramic tablets brings different results in term of microstructural properties. The aim of our study is to identify the origin of observed microstructural differences between these two processes. Formulated alumina powders have been tested to identify the more influent parameters on microstructural and microstructural properties of green ceramic tablets formed by HVC or conventional pressing. The powder fineness, the nature and the amount of organic phases are identified as influent parameters on tablets properties; but a greater compression velocity brings significant enhancements to compacts in term of density and reduced pore size. Moreover, a phenomenological study of compaction allows estimating the intensity of fragmentation, plastic strain and porosity elimination velocity phenomena. Plastic deformation and porosity elimination velocity of spray-dried particles is enhanced with HVC. The elaboration of ceramic items with a complex form has allowed a more detailed study of granular moving. Despite of a very short compression time (3 ms), there are not only vertical movements of grains, some lateral movements also occur; and wall-friction phenomena must be taken in account in items periphery. Tablets elaborated with each forming process are then sintered. The aim is to observe how the initial microstructure of a compact can influence on items sintering behaviour and on their quality in term of density homogeneity and grains size, with consideration of various geometries (form and dimension). It is shown that a more important presence of small size pore is originally of a better densification and a finer microstructure. Sintering results are then linked to the forming process type and reveal positive aspect of HVC on sintered items quality.
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Submitted on : Monday, June 7, 2010 - 11:52:54 AM
Last modification on : Friday, October 23, 2020 - 4:38:37 PM
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  • HAL Id : tel-00489885, version 1

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David Souriou. Compaction conventionnelle et compaction grande vitesse (CGV) de céramiques : influence du procédé de compactage sur le frittage. Mécanique [physics.med-ph]. Ecole Nationale Supérieure des Mines de Saint-Etienne, 2007. Français. ⟨tel-00489885⟩

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