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Radiation tolerance of nanocrystalline ceramics: insights from Yttria Stabilized Zirconia.

Dey S, Drazin JW, Wang Y, Valdez JA, Holesinger TG, Uberuaga BP, Castro RH - Sci Rep (2015)

Bottom Line: Nanocrystalline materials have been reported to present exceptionally high radiation-tolerance to amorphization.In principle, grain boundaries that are prevalent in nanomaterials could act as sinks for point-defects, enhancing defect recombination.Concomitant radiation-induced grain growth was observed which, as a consequence of the non-uniform implantation, caused cracking of the nano-samples induced by local stresses at the irradiated/non-irradiated interfaces.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical Engineering and Materials Science &NEAT ORU, University of California, Davis, CA 95616, USA.

ABSTRACT
Materials for applications in hostile environments, such as nuclear reactors or radioactive waste immobilization, require extremely high resistance to radiation damage, such as resistance to amorphization or volume swelling. Nanocrystalline materials have been reported to present exceptionally high radiation-tolerance to amorphization. In principle, grain boundaries that are prevalent in nanomaterials could act as sinks for point-defects, enhancing defect recombination. In this paper we present evidence for this mechanism in nanograined Yttria Stabilized Zirconia (YSZ), associated with the observation that the concentration of defects after irradiation using heavy ions (Kr(+), 400 keV) is inversely proportional to the grain size. HAADF images suggest the short migration distances in nanograined YSZ allow radiation induced interstitials to reach the grain boundaries on the irradiation time scale, leaving behind only vacancy clusters distributed within the grain. Because of the relatively low temperature of the irradiations and the fact that interstitials diffuse thermally more slowly than vacancies, this result indicates that the interstitials must reach the boundaries directly in the collision cascade, consistent with previous simulation results. Concomitant radiation-induced grain growth was observed which, as a consequence of the non-uniform implantation, caused cracking of the nano-samples induced by local stresses at the irradiated/non-irradiated interfaces.

No MeSH data available.


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STEM DF images for small grain samples.STEM DF images obtained from irradiated 38 nm (a) and 25 nm (b) 10YSZ sample. Arrows indicate intergranular cracks caused by grain coarsening in the irradiated zone.
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f4: STEM DF images for small grain samples.STEM DF images obtained from irradiated 38 nm (a) and 25 nm (b) 10YSZ sample. Arrows indicate intergranular cracks caused by grain coarsening in the irradiated zone.

Mentions: Figure 3 shows a cross-sectional STEM Dark Field (DF) image of the irradiated 220 nm sample. The image is oriented such that the left side is the surface that was directly exposed to the beam. Two clear damage zones could be identified: an area showing small regions of brighter and darker contrast corresponding to irradiation damage, followed by an undamaged region at a depth of >230 nm. Figure 4 and 5 show cross-sectional STEM DF images for 25 nm and 38 nm grained 10YSZ samples, respectively. Beginning from the surface, the micrographs reveal an increase in grain size in the irradiated region, consistent with GIXRD data, followed by a severely-damaged region containing giant inter-granular cracks (that extended longitudinally throughout the sample), and an undamaged region at deeper regions. The grain size in the irradiated zone increased from 25 nm to 34.4 nm, and from 38 nm to 44.5 nm respectively, consistent with the measurements from GIXRD. Interestingly, the edge of the irradiated zone for both nanograined samples show much cleaner grains as compared to the large grained one, which is indicative of a smaller defect cluster concentration.


Radiation tolerance of nanocrystalline ceramics: insights from Yttria Stabilized Zirconia.

Dey S, Drazin JW, Wang Y, Valdez JA, Holesinger TG, Uberuaga BP, Castro RH - Sci Rep (2015)

STEM DF images for small grain samples.STEM DF images obtained from irradiated 38 nm (a) and 25 nm (b) 10YSZ sample. Arrows indicate intergranular cracks caused by grain coarsening in the irradiated zone.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4291567&req=5

f4: STEM DF images for small grain samples.STEM DF images obtained from irradiated 38 nm (a) and 25 nm (b) 10YSZ sample. Arrows indicate intergranular cracks caused by grain coarsening in the irradiated zone.
Mentions: Figure 3 shows a cross-sectional STEM Dark Field (DF) image of the irradiated 220 nm sample. The image is oriented such that the left side is the surface that was directly exposed to the beam. Two clear damage zones could be identified: an area showing small regions of brighter and darker contrast corresponding to irradiation damage, followed by an undamaged region at a depth of >230 nm. Figure 4 and 5 show cross-sectional STEM DF images for 25 nm and 38 nm grained 10YSZ samples, respectively. Beginning from the surface, the micrographs reveal an increase in grain size in the irradiated region, consistent with GIXRD data, followed by a severely-damaged region containing giant inter-granular cracks (that extended longitudinally throughout the sample), and an undamaged region at deeper regions. The grain size in the irradiated zone increased from 25 nm to 34.4 nm, and from 38 nm to 44.5 nm respectively, consistent with the measurements from GIXRD. Interestingly, the edge of the irradiated zone for both nanograined samples show much cleaner grains as compared to the large grained one, which is indicative of a smaller defect cluster concentration.

Bottom Line: Nanocrystalline materials have been reported to present exceptionally high radiation-tolerance to amorphization.In principle, grain boundaries that are prevalent in nanomaterials could act as sinks for point-defects, enhancing defect recombination.Concomitant radiation-induced grain growth was observed which, as a consequence of the non-uniform implantation, caused cracking of the nano-samples induced by local stresses at the irradiated/non-irradiated interfaces.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical Engineering and Materials Science &NEAT ORU, University of California, Davis, CA 95616, USA.

ABSTRACT
Materials for applications in hostile environments, such as nuclear reactors or radioactive waste immobilization, require extremely high resistance to radiation damage, such as resistance to amorphization or volume swelling. Nanocrystalline materials have been reported to present exceptionally high radiation-tolerance to amorphization. In principle, grain boundaries that are prevalent in nanomaterials could act as sinks for point-defects, enhancing defect recombination. In this paper we present evidence for this mechanism in nanograined Yttria Stabilized Zirconia (YSZ), associated with the observation that the concentration of defects after irradiation using heavy ions (Kr(+), 400 keV) is inversely proportional to the grain size. HAADF images suggest the short migration distances in nanograined YSZ allow radiation induced interstitials to reach the grain boundaries on the irradiation time scale, leaving behind only vacancy clusters distributed within the grain. Because of the relatively low temperature of the irradiations and the fact that interstitials diffuse thermally more slowly than vacancies, this result indicates that the interstitials must reach the boundaries directly in the collision cascade, consistent with previous simulation results. Concomitant radiation-induced grain growth was observed which, as a consequence of the non-uniform implantation, caused cracking of the nano-samples induced by local stresses at the irradiated/non-irradiated interfaces.

No MeSH data available.


Related in: MedlinePlus