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Theses

De la nucléation aux interfaces : croissance de phases intermétalliques complexes sur substrats cristallins

Abstract : Complex metal alloys (CMA) refer to intermetallic compounds with large to giant unit cell (even "infinite" for quasicristals), presenting a sub-structure in aggregates assembled according to precise rules. CMA exhibit physical and chemical properties, in particular of the surface, which may be of interest for a certain number of laboratory and industrial applications. We will mention for example the catalytic, tribological and anticorrosive properties. To functionalize these materials, it is necessary to process them in the form of thin layers or in composites. The quality of the surfaces but also of the interfaces between these CMA and the crystal lattice of the substrate or of the matrix is then essential.In our studies, we have followed, at the nanometer scale, the formation of complex intermetallic phases, with specific surface properties, by Fe deposition on unary Al(100) and binary Al9Co2(001) substrates. The resulting systems are characterised by experimental surface techniques (low energy electron diffraction, scanning tunneling microscopy, X-ray photoemission spectroscopy). From these analyses, it follows that the phases formed are stabilized by epitaxy. This includes the metastable Al9Fe2 phase, the high temperature Al8Fe5 phase, the mixed Al9(Fe,Co)2 phase and the Al13Fe4 quasicrystal approximant. We have characterised the structures and properties of the interfaces formed between the CMA and the substrates by high-resolution transmission electron microscopy in order to obtain an atomic description of the interface. These results have been supplemented by ab initio calculations using density functional theory. We have also attempted the direct synthesis of the metastable intermetallic Al9Fe2 by arc melting and melt spinning and then characterised the phases obtained during these processes by X-ray diffraction, scanning and transmission electron microscopies.
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Submitted on : Thursday, May 12, 2022 - 5:12:13 PM
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  • HAL Id : tel-03666821, version 1

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Dominique Dubaux. De la nucléation aux interfaces : croissance de phases intermétalliques complexes sur substrats cristallins. Science des matériaux [cond-mat.mtrl-sci]. Université de Lorraine, 2021. Français. ⟨NNT : 2021LORR0235⟩. ⟨tel-03666821⟩

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