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.
Highlights
Defect sinks, such as grain boundaries and phase boundaries, have been widely accepted to improve the irradiation resistance of metallic materials
As-prepared NP Ag was transparent to the electron beam and had discrete islands which were mostly connected by ligaments (See supplementary Fig. S1a)
NP Ag is basically free from obvious defect clusters prior to radiation (Fig. 1a9)
Summary
Defect sinks, such as grain boundaries and phase boundaries, have been widely accepted to improve the irradiation resistance of metallic materials. Metallic nanoporous (NP) materials with large surface-to-volume ratios have applications for energy storage, catalysts, filters and gas sensors[22] Their mechanical, catalytic and optical properties have been widely investigated[23,24,25]. We performed the first in situ Kr ion irradiation on CG and NP Ag and directly revealed superior radiation tolerance of NP Ag. In situ video captured the migration and removal of irradiationinduced various types of defect clusters by free surface in NP Ag. We determined the significant difference in global and instantaneous diffusivity of defect clusters in CG and NP Ag under irradiation. Our findings provide unambiguous evidence for understanding the significance of free surface on defect removal and migration kinetics in irradiated metallic materials, and offer new insight on design of radiation tolerant advanced materials by tailoring nanoscale porosity
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