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Development of nanocomposite materials for applications in thermoelectric devices

ECO-device THERMOELECtric

PhD - Development of nanocomposite materials for applications in thermoelectric devices

Laboratories and people involved :
Laboratory 1 : ICG/Montpellier
Supervisor : Mickaël Beaudhuin (mickael.beaudhuin umontpellier.fr)

Laboratory 2 :
CIRIMAT/Toulouse -
Supervisors : Emmanuel Flahaut (flahaut chimie.ups-tlse.fr), David Mesguich (mesguich chimie.ups-tlse.fr)

Key words
Energy, Thermoelectricity, Nanocomposite, Spark Plasma Sintering (SPS), Synthesis, Characterization

This PhD project is part of an environmental and economic concern. Fossil and fissile resources for energy production being not sustainable, it is necessary to find new ways of producing and / or recovering energy. Thermoelectric materials could participate to this effort, especially in transport, by converting lost heat to electricity (Seebeck effect). Thermoelectric modules were observed to show large durability (ex : Voyager I and II probes which are still working after more than 30 years). However, the main parameters that limit their large-scale application in the temperature range 500 -900 K are their low efficiency and the use of highly toxic elements such as tellurium, lead or selenium. The aim of this project is to develop thermoelectric materials that are both efficient and environmentally friendly in the perspective of a large-scale production. To succeed, we selected silicides using abundant elements with low environmental impact and high optimization potential. Thermoelectric silicides could overcome such limitations but further efforts are needed in order to improve the efficiency of the modules.

A way to increase the thermoelectric conversion efficiency is to improve the electronic properties by decreasing the dimensionality of the system, by adding dopants or by modifying the interfaces. A decrease of the dimensionality also makes it possible to increase the phonon scattering (at the interfaces), which is favorable to a decrease of the thermal conductivity. The addition of carbon-based nano-objects could make it possible to multiply the interfaces and thus to limit the thermal conductivity, while contributing to nanostructuration during sintering.
The objectives of this project follow these guidelines and will be :
• to synthesize transition metal silicides (bulk and nano-objects) ; conventional or original synthesis techniques will be used (crystal growth, mechanical milling/alloying…).
• to prepare nanocomposites with different mixing methods,
• to sinter the nanocomposites and to control the nanostructure (Spark Plasma Sintering),
• to characterize the alloys chemically, structurally (XRD), microstructurally (SEM, TEM…), to characterize their electronic properties (Hall, Van der Paw, Seebeck coefficient…), their thermal properties (3 omega, laser Flash, DSC) and their lattice dynamics (Raman, IR, Neutron…).
• to build a prototype and to characterize its performances.

Candidate profile :
The candidate should have a background in materials science, chemistry, physics or solid-state chemistry and a strong motivation for experiments. French language is not required and will be improved in the laboratory. However, fluent English (spoken, read, written) is mandatory for foreign candidates.

Location :
The work is part of a cooperation between Montpellier and Toulouse and is funded by the Institute Carnot Chimie Balard Cirimat. It will be mainly held at the Institute Charles Gerhardt Montpellier (ICGM) with chemists, physicists and metallurgists and at the Centre Inter-universitaire de Recherche et d’Ingénierie des Matériaux (CIRIMAT) in Toulouse.

To apply : Send your resume, cover and recommendation letter (or references) to mickael.beaudhuin umontpellier.fr before 2018, June 14th