This subject combines the concepts of surface engineering and those of multi-physical characterization to develop new functional properties on the surface of materials. The “Radiation and heat transfer on the nanometric scale” action addressed the possibility of improving the thermal emissivity of materials by combining surface texturing techniques on the nanometric scale and specific thermal characterizations and simulations. A doctoral thesis and a post-doc studied the optimization of 1D micrometric networks governed by polar materials which support surface phononpolaritons. By exploiting the experimental data of the dielectric functions at different temperatures, this action made it possible on the one hand to obtain coherent thermal sources and on the other hand to optimize the radiative cooling structures.
In the field of materials science, this subject also made it possible to explore (i) nanomechanical engineering of monocrystalline surfaces and the scale transition in metallic foams (in collaboration with the University of Houston), (ii ) knowledge of atomic structures on the free surface of crystalline materials. This last question presents a major challenge to confer new relevant physical properties to materials, for example by controlling atomic reconstructions or nanostructures. In this context, it has been demonstrated both experimentally and by molecular dynamic simulations that the chevron pattern in Au (111) strongly depends on the width of the atomic terrace and that the emergence of dislocations on the free surface can destabilize its organization. Surface texturing is also a way to reduce friction in lubricated contacts. Several surface textures have been designed to achieve this type of wetting regime on an initially hydrophobic material (PTFE). Some of them have been successfully machined with FIB and with a femtosecond laser and have been found to be super hydrophobic. The characterization of the slip length and the friction behavior under lubrication conditions used a newly designed tribometer and the results were compared to theoretical simulations based on the Reynold equation.
Finally, this topic has also been opened to studies outside the usual spectrum of the Pprime Institute: the benefits of texturing for electrocatalysis were the subject of a post-doc, which functionalized 2D titanium carbide plates (say MXenes), in close collaboration between the Pprime Institute and the IC2MP (University of Poitiers). This work focused on the synthesis and characterization of MXene composites to control their functionalization, understand their heterogeneities of crystalline hydration and synthesize them.