Molecular hydrogen H2 is an alternative energy carrier to traditional fossil fuels, gas or oil. It meet the current energy and environmental challenges, i.e. the need to store greenhouse gases free energy produced by intermittent means such as wind turbines or solar panel. Nevertheless, its safe storage and transportation is one of the keys to its use. The containers or pipes that carry the hydrogen must be leaktight and maintain their integrity over time, for both economical and safety reasons. Understanding and predicting the behavior of hydrogen in container/pipeline alloys and the associated mechanical degradation – such as embrittlement – is therefore crucial for the development of the hydrogen industry. These issues are also generic to all alloys exposed to a source of hydrogen, in corrosion or in the metallurgical industries where the hydrogen simply comes from contact with water, or in the oil&gas industry where hydrogen comes from hydrogen sulphides present in hydrocarbons.

If many experimental works have identified hydrogen embrittlement as the origin of the degradation of alloys exposed to hydrogen, large gray areas still remain on the mechanisms at work due to experimental difficulties and the great variability of the observed phenomena. In addition, the transport and trapping of hydrogen prior to mechanical degradation are poorly known and poorly documented at the nanoscale.

The objective of the thesis is to explore the mechanisms of hydrogen trapping / transport in austenitic materials, as well as its distribution in volume, prior to cracking in order to be able to report and explain the experimental observations.
To achieve this objective, the thesis work will be dedicated to the study of pure nickel, a model system for the austenite phase. The study will be carried out in three stages: (i) thermodesorption measurements and (ii) atomic scale simulations using molecular dynamics, both feeding chemical kinetics modeling coupled with Fick's law at the mesoscopic scale.