Among the diversity of energetic materials existing nowadays, nanothermites are widely studied and used thanks to their principal characteristic, the capacity to produce a great quantity of energy by the combustion of a small quantity of material. We chose to work with nanothermites as a stacking of aluminum and copper oxide nanofoils in order to maximize this energy density (theoretical value: 21 kJ/cm3) and then optimize the energetic yielding of the material for industrial applications. This multilayer arrangement is realised by a PVD process of sputtering type, classical or reactive. The Al and CuO layers being formed alternatively, one can always observe the formation of intermixing layers located at the interfaces, where the material is deposited directly on contact with the previous layer. These mixing zones are well identified visually but not chemically characterized: they are composed of aluminum, copper and oxygen in unknown proportions. These barrier layers are both a physical barrier to the species interdiffusion, key mechanism of the exothermic reaction, and a loss of reactive material. Thus the nanothermite has an increased stability in spite of its energetic performances, which is a problem for the reliability and reproducibility of the final material. Mastering the formation of these barrier layers, by understanding the mechanisms at play during the deposition process, is then an important stake towards the control of the reactivity of the Al/CuO multilayer nanothermites. In order to understand the progress of the mixing at the interfaces and to deduce the resulting structure of the mixed layer, we chose to use a modeling method, allowing us to study the matter at time and space scales experimentally unattainable. The present thesis is a work of multiscale modeling in the form of a two-part study, each corresponding to a different physical scale. We first consider the reactivity of an aluminum surface towards deposited copper oxide with the VASP code using the Density Functional Theory (DFT). Then we utilize these atomic-scale results for the construction of a mesoscopic-scale simulator of the kinetic Monte-Carlo type. The simulator thus constructed is able to deposit a layer of matter onto a pure Al(111) surface and allows us to notice an early mixing between the species during the first steps of the deposition process. The first bricks of the simulator being laid, this work is the beginning of a more ambitious study towards the construction of a predictive tool for the structure and composition of the barrier layers depending on the experimental process conditions (temperature, partial pressures of the gazeous phase, experiment time). This tool should allow, in a long-term vision, to do inverse nanoingineering, i.e adapt the fabrication conditions of the nanothermites depending on the final performances required.
Modélisation multiéchelle de la structuration des interfaces dans les nanothermites multicouches Al/CuO déposées en phase vapeur