In situ study of defect migration kinetics in nanoporous Ag with enhanced radiation tolerance

Abstract

Defect sinks, such as grain boundaries and phase boundaries, have been widely accepted to improve the irradiation resistance of metallic materials. However, free surface, an ideal defect sink, has received little attention in bulk materials as surface-to-volume ratio is typically low. Here by using in situ Kr ion irradiation technique in a transmission electron microscope, we show that nanoporous (NP) Ag has enhanced radiation tolerance. Besides direct evidence of free surface induced frequent removal of various types of defect clusters, we determined, for the first time, the global and instantaneous diffusivity of defect clusters in both coarse-grained (CG) and NP Ag. Opposite to conventional wisdom, both types of diffusivities are lower in NP Ag. Such a surprise is largely related to the reduced interaction energy between isolated defect clusters in NP Ag. Determination of kinetics of defect clusters is essential to understand and model their migration and clustering in irradiated materials.

Edge-on dislocation loop in anisotropic hcp zirconium thin foil

“…Such remarks have been supported by in-situ ion irradiation experiments of Fe by Prokhodtseva et al [43] and Yao et al [27]. Rapid absorption of individual dislocation loops by free surfaces is also observed during in-situ Kr ion irradiation on nanoporous Ag, and the image force on discrete dislocation loops adjacent to free surfaces provides the driving force for its migration towards free surfaces [40].…”

“…5(a) shows the loop depth effects of a prismatic 1=3〈1120〉ð1120Þ dislocation loop within ð1120Þ thin foil and a basel 1=20001ð0001Þ dislocation loop within (0001) thin foil. The r ¼ 5 nm dislocation loop is situated at d ¼ 2, 5,10,15,20,25,30,35,40,45 and 48 nm from the bottom surface of the t ¼ 50 nm thin foil, respectively. Anisotropic infinite stress of the dislocation loop is calculated by using Mura's dislocation segment integration formulas [30], and the corresponding anisotropic image displacement fields are calculated with the method of Wu et al [2,28] in Fourier space.…”

“…In order to predict and assess the material performance over a long duration in irradiation environment, it is crucial to understand the basic formation mechanisms of radiation damage at initial damage states at lower doses as well as its accumulation at higher dose levels which results in the complex features in the microstructure [8,10,40]. Ion irradiation enjoys several benefits over both neutron irradiation, and it has been proven to be an excellent tool to simulate the radiation damage process in Zr and its alloys [11,17].…”

Resilient ZnO nanowires in an irradiation environment: An in situ study

“…Free surfaces are the strongest known defect sinks and nanoporous metals have shown superior radiation tolerance [22,23]. A recent research showed helium-implanted Ni 73 P 27 metallic glass nanocylinders exhibit enhanced ductility without sacrifice in yield and ultimate tensile strength [24].…”

In situObservation of Defect Annihilation in Kr Ion-Irradiated Bulk Fe/Amorphous-Fe2Zr Nanocomposite Alloy

“…Numerous phenomena have been observed using the in situ irradiation technique, such as anisotropic void formation in Mg, [26] irradiation-induced grain growth in Fe and Zr, [27] defect absorption by triple junctions in nanocrystalline Ni, [28] defect removal by twin boundaries (TBs) and the irradiation-induced TB migrations in nanotwinned metals, [29,30] and defect migration kinetics in nanoporous metals. [31][32][33] Meanwhile several in situ mechanical testing studies on irradiated materials are also available. [34,35] Most prior studies on multilayers focused on thin films (several µ m in thickness), whereas the application in nuclear reactors typically calls for bulk nanocomposites.…”