UD3formation on uranium: evidence for grain boundary precipitation

The formation of UD3 on the surface of annealed uranium was induced at 320°C and 500 mbar pressure. The location of the deuteride (UD3) precipitates with respect to metal grain boundaries at the sample surface was studied by secondary ion mass spectrometry (SIMS) and focused ion beam (FIB) methods. Ion etching was used to remove the passive oxide layer on the sample surface and reveal the underlying structure of the metal grains. There is strong evidence for the formation of UD3 phases along the metal grain boundaries at the uranium surface.