Grain boundary effects on defect production and mechanical properties of irradiated nanocrystalline SiC

Abstract

Grain boundaries (GBs) are known to play an important role in determining the mechanical and functional properties of nanocrystalline materials. In this study, we used molecular dynamics simulations to investigate the effects of damaged GBs on the mechanical properties of SiC that is irradiated by 10 keV Si atoms. The results reveal that irradiation promotes GB sliding and reduces the ability of GBs to block dislocations, which improves the deformation ability of nanocrystalline SiC. However, irradiation causes local rearrangements in disordered clusters and pinning of dislocations in the grain region, which restrains its deformation. These two mechanisms arise from the irradiation effects on GBs and grains, and these mechanisms compete in nanocrystalline SiC during irradiation. The irradiation effects on GBs dominate at low irradiation doses, and the effects on grains dominate at high doses; the result of these combined effects is a peak ductility of 0.09 dpa in nanocrystalline SiC.

Grain boundary resistance to amorphization of nanocrystalline silicon carbide

“…As a result, the shape of grains changed and the nano-columns became narrow under irradiation. The amorphization processes of our present simulations are in good agreement with these experimental observations, and consistent with the molecular dynamics (MD) simulations of irradiated nanocrystalline SiC by Niu et al 13 who found the same trend of damage accumulation processes in irradiation-induced amorphization. Cascade simulations in nanocrystalline SiC have showed that the number of defects produced in a cascade primarily depends on the volume fraction of GB and more defects are produced along the GB due to the lower threshold displacement energies 14 .…”

Effects of irradiation on the mechanical behavior of twined SiC nanowires

“…Previous researches have also found that grain boundary is an effective sink for atomic defects introduced by irradiation in zinc-blend SiC. [27][28][29] The defect density distribution along the radial direction is defined by the number of rings in a hollow cylinder with the same axis as the nanowires divided by its volume (inset in Fig. 3(d)).…”

Study of the Ion‐Irradiation Behavior of Advanced SiC Fibers by Raman Spectroscopy and Transmission Electron Microscopy

“…However, nc‐SiC with grains sizes in the range 30–50 nm did not show significant differences with respect to single crystals under ion‐irradiation at RT . Also, even though in many materials GBs strongly interact with the displacement cascades, many studies indicate that there is no direct effect of the GBs on the primary defect production in SiC …”

“…54 Also, even though in many materials GBs strongly interact with the displacement cascades, 55 many studies indicate that there is no direct effect of the GBs on the primary defect production in SiC. [56][57][58] As discussed by Jiang et al, 49 disorder accumulation in a crystalline grain cannot be avoided unless the point defects produced during irradiation are completely recovered before the next displacement event in the crystallite. A rough estimation of the mean diffusion length (l D ), for Si and C interstitials and vacancies at 200°C can be calculated using the expression l D ¼ ffiffiffiffiffiffiffiffi 2Dt p , being D the diffusion coefficient for the desired point defect, and t the time between two consecutive displacement events.…”