The development of multifunctional materials with specific surface / interface properties is a “core” research axis of INTERACTIVES. The physical and mechanical properties of the surface can be controlled by adding new phases, modifying the microstructure, or texturing the surface on a nano / micrometric scale. Small changes in the surface can indeed cause dramatic changes in gross behavior. INTERACTIFS is based on several advanced surface engineering technologies: texturing and etching by ion bombardment, ion implantation, deposition. These techniques are based on the interaction of matter with ions which are either sprayed or deposited on the surface, or implanted below. Particular attention is paid to the effects induced by these ion-matter interactions in order to avoid any modification of physical properties or production of undesired defects during the treatment of the surface. For this, the complete characterization of the microstructure of the treated surface must be carried out by conventional microscopy techniques (MEB-FEG, EBSD, MET, AFM, STM) before measuring physical properties.
The difficulty comes from low scales which require the development of tools for developing and transforming very specific surfaces as well as associated small-scale metrology. Mastering these tools is a major issue with a wide scope in terms of scientific and application developments. If we are able to model / master the structure of the first atomic layers, we can consider piloting the mechanisms that develop in this area and which condition the properties of the surface.
Theme 1 is divided into 3 research themes:
Action 1.1.The first deals with the role of internal stresses and surfaces on the elastic and plastic response of materials.
Supervisors: Anne Joulain / Joël Bonneville
This research is interested in the phenomena which have their sources in the material near the fluid-solid interface.This introduces a characteristic length of the order of a few nanometers which generate specific responses of the material.The induced scale effects are at the source of the problem and influence both elasticity and the early stages of plasticity in crystals.The challenges are to understand these scale effects both from an experimental point of view and in terms of modeling..
Action 1.2.The second is related to the plasticity / damage transition and the interaction between surface defects and the environment.
Supervisors: Yves Nadot / Gilbert Henaff
A complementary component to the knowledge of the first stages of plasticity on the surface relates to the scenarios which will lead to the initiation of the damage to the material.In this plasticity / damage transition scenario, environmental effects play a major role.Certain fluid elements can cross the interface, penetrate the solid and modify the deformation mechanisms.
Action 1.3.The third can be considered as a “toolbox” for experiments at the nano / micro scale.The objective is to develop measurement devices and protocols, as precise as possible, in order to be able to avoid artefacts in quantification at the micro scale.
Supervisors: Valéry Valle / Pascal Doumalin
These three actions are associated with scientific questions on different scales, from nanometric to macroscopic behavior.Their combination aims at an understanding / prediction / control of the physical and mechanical phenomena involved in the behavior of surfaces / interfaces.This multi-scale and multi-physical scheme is illustrated by the figure below.
Nano-engineering of surfaces: scientific challenges in physics and mechanics of surfaces from elasticity to damage.