The role of grain size in He bubble formation: Implications for swelling resistance

El-Atwani, Osman; Nathaniel, James E.; Leff, Asher C.; Muntifering, Brittany; Baldwin, J. Kevin; Hattar, Khalid Mikhiel; Taheri, Mitra L.

doi:10.1016/j.jnucmat.2016.12.003

Cited by 75 publications

(30 citation statements)

References 78 publications

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“…Nanocrystalline metals are considered candidates for severe environmental applications which require irradiation-resistant materials 1 , 2 due to a promise of enhanced mechanical properties (strength and ductility) 3 , 4 , and radiation resistance 1 , 2 , 5 – 11 due to their high grain boundary density in comparison to their bulk counterparts 3 , 4 , 12 . During applications involving radiation, such as fusion and fission reactors, materials are exposed to different energetic particles with a range of doses and dose rates, which form Frenkel defect pairs (vacancies and interstitials); a high percentage of these defects will recombine leaving a small ratio of freely migrating defects.…”

Section: Introductionmentioning

confidence: 99%

Direct Observation of Sink-Dependent Defect Evolution in Nanocrystalline Iron under Irradiation

El-Atwani

Nathaniel

Leff

et al. 2017

Sci Rep

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Crystal defects generated during irradiation can result in severe changes in morphology and an overall degradation of mechanical properties in a given material. Nanomaterials have been proposed as radiation damage tolerant materials, due to the hypothesis that defect density decreases with grain size refinement due to the increase in grain boundary surface area. The lower defect density should arise from grain boundary-point defect absorption and enhancement of interstitial-vacancy annihilation. In this study, low energy helium ion irradiation on free-standing iron thin films were performed at 573 K. Interstitial loops of a 0/2 [111] Burgers vector were directly observed as a result of the displacement damage. Loop density trends with grain size demonstrated an increase in the nanocrystalline (<100 nm) regime, but scattered behavior in the transition from the nanocrystalline to the ultra-fine regime (100–500 nm). To examine the validity of such trends, loop density and area for different grains at various irradiation doses were compared and revealed efficient defect absorption in the nanocrystalline grain size regime, but loop coalescence in the ultra-fine grain size regime. A relationship between the denuded zone formation, a measure of grain boundary absorption efficiency, grain size, grain boundary type and misorientation angle is determined.

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Section: Introductionmentioning

confidence: 99%

Direct Observation of Sink-Dependent Defect Evolution in Nanocrystalline Iron under Irradiation

El-Atwani

Nathaniel

Leff

et al. 2017

Sci Rep

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“…Similarly, it has been reported that He irradiation of Fe nanocrystals resulted in bubble accumulation dependent on crystal size with smaller crystals accumulating He bubbles at lower concentrations and with reduced irradiation hardening compared to the bulk [43]. El-Atwani et al [21,44] observed reduced bubble density in nanocrystalline W grains (<100 nm grain sizes) compared to ultrafine W (100–500 nm grain size range) which they attributed to the proximity of the grain boundary in nanocrystalline W acting as a sink for defects. These studies indicate that the effectiveness of interphases will depend on the distances defects migrate within the boundary planes and thus a shorter required distance in smaller crystals enhances the recombination of point defects at sinks.…”

Section: Resultsmentioning

confidence: 99%

Enhanced Radiation Tolerance of Tungsten Nanoparticles to He Ion Irradiation

et al. 2018

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Materials exposed to plasmas in magnetic confinement nuclear reactors will accumulate radiation-induced defects and energetically implanted gas atoms (from the plasma and transmutations), of which insoluble helium (He) is likely to be the most problematic. The large surface-area-to-volume ratio exhibited by nanoporous materials provides an unsaturable sink with the potential to continuously remove both point defects and He. This property enhances the possibilities for these materials to be tailored for high radiation-damage resistance. In order to explore the potential effect of this on the individual ligaments of nanoporous materials, we present results on the response of tungsten (W) nanoparticles (NPs) to 15 keV He ion irradiation. Tungsten foils and various sizes of NPs were ion irradiated concurrently and imaged in-situ via transmission electron microscopy at 750 °C. Helium bubbles were not observed in NPs with diameters less than 20 nm but did form in larger NPs and the foils. No dislocation loops or black spot damage were observed in any NPs up to 100 nm in diameter but were found to accumulate in the W foils. These results indicate that a nanoporous material, particularly one made up of ligaments with characteristic dimensions of 30 nm or less, is likely to exhibit significant resistance to He accumulation and structural damage and, therefore, be highly tolerant to radiation.

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“…Averages were calculated from the results in all grains. A detailed illustration of the quantification process was published in the supplemental of reference [20]. Figure 1 shows a schematic diagram of the sample, implantation conditions and overlapping ion and displacement damage distributions.…”

Section: Methodsmentioning

confidence: 99%

In-Situ Helium Implantation and TEM Investigation of Radiation Tolerance to Helium Bubble Damage in Equiaxed Nanocrystalline Tungsten and Ultrafine Tungsten-TiC Alloy

et al. 2020

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The use of ultrafine and nanocrystalline materials is a proposed pathway to mitigate irradiation damage in nuclear fusion components. Here, we examine the radiation tolerance of helium bubble formation in 85 nm (average grain size) nanocrystalline-equiaxed-grained tungsten and an ultrafine tungsten-TiC alloy under extreme low energy helium implantation at 1223 K via in-situ transmission electron microscope (TEM). Helium bubble damage evolution in terms of number density, size, and total volume contribution to grain matrices has been determined as a function of He + implantation fluence. The outputs were compared to previously published results on severe plastically deformed (SPD) tungsten implanted under the same conditions. Large helium bubbles were formed on the grain boundaries and helium bubble damage evolution profiles are shown to differ among the different materials with less overall damage in the nanocrystalline tungsten. Compared to previous works, the results in this work indicate that the nanocrystalline tungsten should possess a fuzz formation threshold more than one order of magnitude higher than coarse-grained tungsten.

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The role of grain size in He bubble formation: Implications for swelling resistance

Cited by 75 publications

References 78 publications

Direct Observation of Sink-Dependent Defect Evolution in Nanocrystalline Iron under Irradiation

Direct Observation of Sink-Dependent Defect Evolution in Nanocrystalline Iron under Irradiation

Enhanced Radiation Tolerance of Tungsten Nanoparticles to He Ion Irradiation

In-Situ Helium Implantation and TEM Investigation of Radiation Tolerance to Helium Bubble Damage in Equiaxed Nanocrystalline Tungsten and Ultrafine Tungsten-TiC Alloy

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