Nanoscale lattice strains in self-ion implanted tungsten

Abstract

Developing a comprehensive understanding of the modification of material properties by neutron irradiation is important for the design of future fission and fusion power reactors. Self-ion implantation is commonly used to mimic neutron irradiation damage, however an interesting question concerns the effect of ion energy on the resulting damage structures. The reduction in the thickness of the implanted layer as the implantation energy is reduced results in the significant quandary: Does one attempt to match the primary knock-on atom energy produced during neutron irradiation or implant at a much higher energy, such that a thicker damage layer is produced? Here we address this question by measuring the full strain tensor for two ion implantation energies, 2 MeV and 20 MeV in self-ion implanted tungsten, a critical material for the first wall and divertor of fusion reactors. A comparison of 2 MeV and 20 MeV implanted samples is shown to result in similar lattice swelling. Multi-reflection Bragg coherent diffractive imaging (MBCDI) shows that implantation induced strain is in fact heterogeneous at the nanoscale, suggesting that there is a non-uniform distribution of defects, an observation that is not fully captured by micro-beam Laue diffraction. At the surface, MBCDI and high-resolution electron back-scattered diffraction (HR-EBSD) strain measurements agree quite well in terms of this clustering/non-uniformity of the strain distribution. However, MBCDI reveals that the heterogeneity at greater depths in the sample is much larger than at the surface. This combination of techniques provides a powerful 1

Annealing of focused ion beam damage in gold microcrystals: an in situ Bragg coherent X-ray diffraction imaging study

“…Thus, we establish a 40 Â 40 Â 40 voxel volume centred on the bulk ROI's ( Fig. 9) centre of mass, a region relatively unaffected by FIB-induced strain, as the strain reference for every reconstruction (Phillips et al, 2020). The amplitude threshold is 0.30 for all reconstructions.…”

Three-dimensional strain dynamics govern the hysteresis in heterogeneous catalysis

“…The strain sensitivity is of the order of~2 × 10 −4 due to the strong sensitivity of X-rays to the crystal lattice spacing. Such a strain sensitivity is nowadays routinely achieved using BraggCDI methods as reported by [28][29][30][31] . It is most pronounced at edges {110} and corner sites {111}, in the case of the gold cube.…”

“…Indeed, to determine the full strain tensor, at least three or more non-parallel reflections must be collected. Multiple reflections from a single particle have been measured previously using BraggCDI 29,31,34 but such a study could not be carried out in this work due to the in situ experimental limitations of the operando cell. However, the 111 component is also sensitive to 100, 110 latice distortions, and so used throughout as a signature of the phenomenon occurring at the surface of the nanocrystal during the catalytic process, to image their elastic response 35 .…”

Characterising Ion-Irradiated FeCr: Hardness, Thermal Diffusivity and Lattice Strain

“…The discrepancy may be partially accounted for by the loss of defect loops to the surface of TEM samples. Another factor to consider is contributions from defects below the sensitivity limit of TEM [70]. One point that supports this is that in TEM measurements, the density of defects increases as (dpa) n with 1 ≤ n ≤ 2 [11], whereas the defect density calculated from strain measurements is proportional to the natural logarithm of damage.…”