Effects of Oxides on Hydrogen Uptake and Release in Dispersion-Strengthened Tungsten*

To further our understanding of hydrogen (H) retention in PFCs, it is important to consider tungsten-oxide systems. Oxides form naturally on the surface of tungsten (W) due to the strong chemical affinity. This effect becomes more prominent in extreme environments e.g., in fusion reactors. As materials are exposed to the plasma, they will experience erosion and re-deposition, which could significantly modify fuel retention. Therefore, the topic of oxidative mechanisms for hydrogen retention warrants further discussion. In collaboration with Sandia National Lab, we will elucidate how both the partial coverage of oxygen (O), as well as the presence of oxide thin films, affects H chemisorption and uptake in dispersion-strengthened tungsten (DS-W) samples. We will be using W-1%ZrC, W-5%TiC, and W-10%TiC to compare the effects of different dispersoids on O and H interactions in W. We will apply low energy ion scattering (LEIS) and direct recoil spectroscopy (DRS) to investigate how the partial coverage of O affects H chemisorption on the surface, as well as x-ray photoelectron spectroscopy (XPS) and Auger spectroscopy to characterize both the material’s chemical and elemental composition before and after dosing. We will then grow oxide films on the materials to further investigate the effects of oxides on these surfaces. Subsequently, we will perform ellipsometry in-situ with deuterium (D) plasma exposure to obtain optical properties in real time. Finally, we will use LEIS and DRS again to quantify the chemisorbed H and D under the presence of these thicker oxide layers.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.