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Title: The multiple roles of small-angle tilt grain boundaries in annihilating radiation damage in SiC

Abstract

Lattice defects generated by radiation damage can diffuse to grain boundaries (GBs) and be annihilated at GBs. However, the precise role of GBs in annihilating the segregated defects remains unclear. Here, we employed multi-scale models to determine how interstitials are annihilated at small-angle tilt GBs (STGBs) in SiC. First of all, we found the pipe diffusion of interstitials in STGBs is slower than bulk diffusion. This is because the increased interatomic distance at dislocation cores raises the migration barrier of interstitial dumbbells. Furthermore, we found both the annihilation of interstitials at jogs and jog nucleation from clusters are diffusion-controlled and can occur under off-stoichiometric interstitial fluxes. Finally, a dislocation line model is developed to predict the role of STGBs in annihilating radiation damage. This model includes defect flux to GBs, pipe diffusion in STGBs, and the interaction of defects with jogs. The model predicts the role of STGBs in annihilating defects depends on the rate of defects segregation to and diffusion along STGBs. STGBs mainly serve as diffusion channel for defects to reach other sinks when defect diffusivity is high at boundaries. As a result, when defect diffusivity is low, most of the defects segregated to STGBs are annihilated bymore » dislocation climb.« less

Authors:
 [1];  [1];  [1]
  1. Univ. of Wisconsin, Madison, WI (United States)
Publication Date:
Research Org.:
Univ. of Wisconsin, Madison, WI (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1347521
Grant/Contract Number:
FG02-08ER46493
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 7; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; atomistic models; materials for devices; materials for energy and catalysis; structural materials

Citation Formats

Jiang, Hao, Wang, Xing, and Szlufarska, Izabela. The multiple roles of small-angle tilt grain boundaries in annihilating radiation damage in SiC. United States: N. p., 2017. Web. doi:10.1038/srep42358.
Jiang, Hao, Wang, Xing, & Szlufarska, Izabela. The multiple roles of small-angle tilt grain boundaries in annihilating radiation damage in SiC. United States. doi:10.1038/srep42358.
Jiang, Hao, Wang, Xing, and Szlufarska, Izabela. Thu . "The multiple roles of small-angle tilt grain boundaries in annihilating radiation damage in SiC". United States. doi:10.1038/srep42358. https://www.osti.gov/servlets/purl/1347521.
@article{osti_1347521,
title = {The multiple roles of small-angle tilt grain boundaries in annihilating radiation damage in SiC},
author = {Jiang, Hao and Wang, Xing and Szlufarska, Izabela},
abstractNote = {Lattice defects generated by radiation damage can diffuse to grain boundaries (GBs) and be annihilated at GBs. However, the precise role of GBs in annihilating the segregated defects remains unclear. Here, we employed multi-scale models to determine how interstitials are annihilated at small-angle tilt GBs (STGBs) in SiC. First of all, we found the pipe diffusion of interstitials in STGBs is slower than bulk diffusion. This is because the increased interatomic distance at dislocation cores raises the migration barrier of interstitial dumbbells. Furthermore, we found both the annihilation of interstitials at jogs and jog nucleation from clusters are diffusion-controlled and can occur under off-stoichiometric interstitial fluxes. Finally, a dislocation line model is developed to predict the role of STGBs in annihilating radiation damage. This model includes defect flux to GBs, pipe diffusion in STGBs, and the interaction of defects with jogs. The model predicts the role of STGBs in annihilating defects depends on the rate of defects segregation to and diffusion along STGBs. STGBs mainly serve as diffusion channel for defects to reach other sinks when defect diffusivity is high at boundaries. As a result, when defect diffusivity is low, most of the defects segregated to STGBs are annihilated by dislocation climb.},
doi = {10.1038/srep42358},
journal = {Scientific Reports},
number = ,
volume = 7,
place = {United States},
year = {Thu Feb 09 00:00:00 EST 2017},
month = {Thu Feb 09 00:00:00 EST 2017}
}

Journal Article:
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  • Interaction between grain boundaries and radiation is studied in 3C-SiC by conducting molecular dynamics cascade simulations on bicrystal samples with different misorientation angles. The damage in the in-grain regions was found to be unaffected by the grain boundary type and is comparable to damage in single crystal SiC. Radiation-induced chemical disorder in the grain boundary regions is quantified using the homonuclear to heteronuclear bond ratio ({chi}). We found that {chi} increases nearly monotonically with the misorientation angle, which behavior has been attributed to the decreasing distance between the grain boundary dislocation cores with an increasing misorientation angle. The change inmore » the chemical disorder due to irradiation was found to be independent of the type of the grain boundary.« less
  • Large depression of T{sub c} at 7{degree} [100] tilt grain boundaries was observed in bulk Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} (Bi2212) bicrystals by measuring the zero-field electrical transport properties of the grain boundaries and the constituent single crystals over an extended range of currents and voltages. The T{sub c}-depressed region was determined to be around 20 nm, comparable to the width of the strain field associated with the observed array of grain-boundary dislocations. Superconducting coupling of the grain boundaries increases sharply as temperature decreases below the grain-boundary T{sub c}{congruent}68 K. {copyright} {ital 1997 American Institute of Physics.}
  • Dislocations in crystalline materials constitute unique, atomic-scale, one-dimensional structure and have a potential to induce peculiar physical properties that are not found in the bulk. In this study, we fabricated LiNbO{sub 3} bicrystals with low angle tilt grain boundaries and investigated the relationship between the atomic structure of the boundary dislocations and their electrical conduction properties. Observations by using transmission electron microscopy revealed that dislocation structures at the (0001) low angle tilt grain boundaries depend on the tilt angle of the boundaries. Specifically, the characteristic dislocation structures with a large Burgers vector were formed in the boundary with the tiltmore » angle of 2°. It is noteworthy that only the grain boundary of 2° exhibits distinct electrical conductivity after reduction treatment, although LiNbO{sub 3} is originally insulating. This unique electrical conductivity is suggested to be due to the characteristic dislocation structures with a large Burgers vector.« less
  • Controlled development of the ceramic microstructure has produced silicon carbide (SiC) with a toughness three times that of a commercial SiC, Hexoloy-SA, coupled with > 50% improvement in strength. Al, B and C were used as sintering additives, hence the designation ABC-SiC. These additives facilitated full densification at temperature as low as 1,700 C, the formation of an amorphous phase at the grain boundaries to enhance intergranular fracture, and the promotion of an elongated microstructure to enhance crack deflection and crack bridging. Comparisons of microstructures and fracture properties have been made between the present ABC-SiC, Hexoloy-SA and other reported SiCmore » ceramics sintered with YAG or Al{sub 2}O{sub 3}. The Al-O chemistry of the amorphous phase in the ABC-SiC accounted for the intergranular fracture vs the transgranular fracture in Hexoloy-SA. An interlocking plate-like grain structure developed during the {beta} to {alpha} transformation without limiting densification. The combined microstructural developments improved both strength and toughness.« less
  • No abstract prepared.