Description of the project

Electrophoretic deposition (EPD) is a technique in which an electric field is applied to a colloidal suspension leading to a migration of particles towards an electrode where they assemble into a deposit. In recent years, EPD has appeared as a method of choice to generate environmental barrier coatings thanks to its ease of implementation and its ability to produce coatings of relatively large thicknesses in a single step process. Its attractivity also results from the large variability of parameters involved (applied electric field, particle concentration, viscosity of the suspension, etc…) which can be tuned to adapt the coating to each application. While this freedom in the experimental design offers a wide range of possibilities for the final properties of the deposit, finding the right combination of parameters can be an overwhelming task. Moreover, while continuum models have been proposed to relate the setup parameters with the mass and thickness of the deposit, they are usually only applicable to low concentrations of colloids (for which interparticle interactions can be neglected) and their predictive power is limited to macroscopic quantities with no information on the microstructure of the deposit. In 2016, a mesoscale particle based model has been proposed by Giera et al. (Langmuir, 33, 652, 2017) to get insights into the EPD process and properties of the resulting deposit. Recently, this Brownian dynamics method was adapted at the CIRIMAT to study rare earth particles. The obtained results are consistent with experiments and empirical laws, but the suspension and the process simulated are still very simple in comparison with experiments.

The objective of this project is to improve this mesoscale model to better take into account the experimental complexity and, as such, better understand the results obtained for materials of various natures. In particular, this project will bring be complementary experiments, conducted at the CIRIMAT, on electrophoretic deposition in aqueous suspensions. The PhD student will realise a number of mesoscopic simulations using the LAMMPS software and analyse them in order to determine, for all sets of parameters, the mass and thickness of the deposit and properties characterising its morphology (packing fraction, coordination numbers, coverage fraction, etc…). This should allow us to define the first order parameters that are the most relevant for the tuning of the coatings properties and the optimisation of environmental barrier performances, but also to adapt them to other applications. The envisioned simulations will aim to study both simple and complex geometries. One of the main challenges will be to include the effects of chemical reactions at the electrode, e.g. bubble formation, on the coating.

Work Context

This contract, financed by the French ministry MESR (net salary 1400-1500 euros/month), will be part of a project in collaboration with Safran. The host laboratory is the CIRIMAT, in Toulouse, which is a joint research unit between CNRS, UT3 and INPT with around 220 staff members including a bit more than 100 permanent staff members and around 75 PhD students. The laboratory gathers skills in Materials Science and Materials Engineering.

Additional Information

Applicant’s profile : The applicant should have (or be about to receive) a master in chemistry, materials science or physics and be interested in doing theoretical work. Some experience in programming and/or in simulations and statistical physics would be appreciated.

For any additional information on the project and/or the recruitment process, it is possible to contact Céline Merlet (celine.merlet@univ-tlse3.fr) and Sandrine Duluard (sandrine.duluard@univ-tlse3.fr). Formal applications must be sent through the SDM graduate school website https://ed-sdm.univ-toulouse.fr/.