Sujet 91-2 Proposés Pour Une Allocation De Recherche 2003

ECOLE DOCTORALE SI-MMEA (http://simmea.ed.univ-poitiers.fr/)

2015 Doctoral research projects for PhD recruitment

I- General information :

VILLE, LABORATOIRE Poitiers (FR) : x P’D1* P’D2* P’D3* Town, Laboratory Limoges (FR) : SPCTS* GEMH* La Rochelle (FR) : LaSIE* Etablissement X UP* ENSMA* UL* ENSCI* Institution ULR* TITRE en français Etude de la résistance à l’oxydation à haute température French title de phases MAX TITRE en anglais HIGH-TEMPERATURE OXIDATION RESISTANCE OF MAX PHASES English title Directeur(s) de thèse (HDR) Nom 1 : DUBOIS Prénom 1 : Sylvain % : 33 Supervisor(s) Taux d’encadrement prévu (%) Supervising rates (%) Nom 2 : Prénom 2 : % : Co-encadrant(s) Nom 1 : CHARTIER Prénom 1 : Patrick HDR : non Co-supervisor(s) % : 33 Taux d’encadrement prévu (%) Supervising rates (%) Nom 1 : BRUNET Prénom 1 : Véronique HDR : non % : 33 Nom : DUBOIS Prénom : Sylvain Contact pour informations Contact for information Tel : +33 5 49 49 67 49 Email : [email protected] Compétences requises Pre requisite Sciences des matériaux *Sigle : P’D1, P’D2 et P’D3 : Départements D1, D2 et D3 de l’institut P’ : http://www.pprime.fr/; SPCTS : http://www.unilim.fr/spcts/; GEMH : http://www.avrul.fr/spip.php?rubrique39; LaSIE : http://www.univ-larochelle.fr/LaSIE, UP http://www.univ-poitiers.fr/, ENSMA http://www.ensma.fr/, UL : http://www.unilim.fr/, ENSCI : http://www.ensci.fr/, ULR : http://www.univ-larochelle.fr/.

II- Description of the 3 year doctoral research project (please make a complete description of the doctoral research project. Do not forget to mention when the contract will start and to give an estimation of the net salary per month)

Mn+1AXn phases (with n=1, 2 or 3) form a class of nanolaminated ternary carbides or nitrides, where M stands for an early transition metal, A for a group A-element and X for carbon or nitrogen. The hexagonal nanolaminated crystal structure of these so-called MAX phases consists of edge-sharing M6X octahedra (characterized by mostly strong metallic M-X bonds) intercalated with layers of pure A group element (through weak M-A bonds). This inherent nanolayered structure provides a unique combination of metal-like (good electrical and thermal conductivity, damage tolerance, low hardness, machinability …) and ceramic-like properties (low density, refractory, good oxidation resistance, high stiffness …) which opens a way to diverse potential applications: tribology, electronic, structural (aerospace, heat exchanger …).

These hexagonal structures present a high (c/a) ratio, that induces a strong crystal anisotropy and augurs an anisotropy of the properties such as electronic transport, mechanical properties and oxidation resistance.

Within the frame work of potential applications in the field of high-temperature structural materials, the relationship between microstructure and oxidation resistance has to be investigated. Preliminary results show that the grains size and grain orientation play a major role during the high temperature oxidation of such materials.

During the Master research internship, MAX phases bulk samples and powders (Ti3AlC2, Ti2AlC and

V2AlC) will be synthesized using powder metallurgy processes. The bulk samples will be produced by pressure-assisted reactive sintering from elemental powders using the so-called Hot Isostatic Pressing (HIP) process; Flash sintering densification method such as Spark Plasma Sintering (SPS) will also be used to densify MAX phase powders. These two processes will provide samples with different grain sizes.

Within the frame of the “Maxycrist” ANR project, V2AlC single crystals will be used as model materials for studying the oxidation process of one grain. The oxidation kinetics and the corresponding oxidation mechanisms of MAX phases will be studied, as a function of microstructure, using thermogravimetric analyses.

The different technics used in this study are: powder metallurgy synthesis methods for samples production, X-ray diffraction and scanning electron microscopy for samples characterization and thermogravimetric analysis for the oxidation kinetics study.