Nanoscale Analysis of Hydrogen Interaction and Material Degradation Mechanisms Using Cryogenic Transfer Atom Probe Tomography and Correlative Transmission Electron Microscopy

The mechanistic understanding of hydrogen's role in altering the functional and structural properties of materials, as well as its involvement in material degradation mechanisms, can be enhanced by leveraging atom probe tomography to map nanoscale hydrogen segregation to defects and interfaces. However, due to hydrogen's tendency to diffuse out of most materials even at room temperature, a streamlined procedure is necessary for charging materials with hydrogen isotopes and then transferring the samples under vacuum and cryogenic conditions to the atom probe tomography. Such information when paired with the structural analysis of materials achieved using transmission electron microscopy can be key for achieving spatially resolved mapping of hydrogen to defects and interfaces in materials.<br/><br/>This presentation will showcase the state-of-the-art capabilities at the Pacific Northwest National Laboratory for seamless transfer of material samples before and after hydrogen isotope charging. Transfers are performed between a plasma-focused ion beam (PFIB—Helios Hydra), an atom probe tomography system (APT—LEAP 6000XR), and a nitrogen-containing glovebox (N2-GB) at both room and cryogenic temperatures. Using this advanced capability, we quantitatively analyzed hydrogen uptake in a model FeCrNi alloy, both with and without deformation-induced defects, and distinguished between diffusible and trapped hydrogen in the microstructure. This unique capability is also being extended to analyze the hydrogen segregation in complex oxides and in platinum group element catalysts to pinpoint the tendency for hydrogen to segregate to defects and interfaces.