2019/09/30 by Abdallah Reza, Reza, Abdallah, Hongbing Yu +5 · 4 citations
Engineering · Materials Science · #Ion-surface interactions and analysis #Advanced Materials Characterization Techniques #Nuclear Materials and Properties
paper · pdf · doi:10.48550/arxiv.1909.13612
Using transient grating spectroscopy (TGS) we measure the thermal diffusivity\nof tungsten exposed to different levels of 20 MeV self-ion irradiation. Damage\nas low as 3.2 x 10-4 displacements per atom (dpa) causes a measurable\nreduction in thermal diffusivity. Doses of 0.1 dpa and above, up to 10 dpa,\ngive a degradation of around 55% from the pristine value at room temperature.\nUsing a kinetic theory model, the density of irradiation-induced point defects\nis estimated based on the measured changes in thermal diffusivity as a function\nof dose. These predictions are compared with point defect and dislocation loop\ndensities observed in transmission electron microscopy (TEM). Molecular\ndynamics (MD) predictions are combined with the TEM observations to estimate\nthe density of point defects associated with defect clusters too small to be\nprobed by TEM. When these "invisible" defects are accounted for, the total\npoint defect density agrees well with that estimated from TGS for a range of\ndoses spanning 3 orders of magnitude. Kinetic theory modelling is also used to\nestimate the thermal diffusivity degradation expected due to TEM-visible and\ninvisible defects. Finely distributed invisible defects appear to play a much\nmore important role in the thermal diffusivity reduction than larger\nTEM-visible dislocation loops. This work demonstrates the capability of TGS, in\nconjunction with kinetic theory models, to provide rapid, quantitative insight\ninto defect densities and property evolution in irradiated materials.\n