High energy particle radiations induce severe microstructural damage in metallic materials. Nanoporous materials with a giant surface-to-volume ratio may alleviate radiation damage in irradiated metallic materials as free surface are defect sinks. Here we show, by using in situ Kr ion irradiation in a transmission electron microscope at room temperature, that nanoporous Au indeed has significantly improved radiation tolerance comparing with coarse-grained, fully dense Au. In situ studies show that nanopores can absorb and eliminate a large number of radiation-induced defect clusters. Meanwhile, nanopores shrink (self-heal) during radiation, and their shrinkage rate is pore size dependent. Furthermore, the in situ studies show dose-rate-dependent diffusivity of defect clusters. This study sheds light on the design of radiation-tolerant nanoporous metallic materials for advanced nuclear reactor applications.

Key challenges limiting the adoption of metallic plasmonic nanostructures for practical devices include structural stability and the ease of large scale fabrication. Overcoming these issues may require novel metamaterial fabrication with potentials for improved durability under extreme conditions. In this work, we report a self-assembled growth of a hybrid plasmonic metamaterial in thin-film form, with epitaxial Ag nanopillars embedded in TiN, a mechanically strong and chemically inert matrix. One of the key achievements lies in the successful control of the tilt angle of the Ag nanopillars (from 0° to 50°), which is attributed to the interplay between the growth kinetics and thermodynamics during deposition. Such an anisotropic nature offered by the tilted Ag nanopillars in TiN matrix is crucial for achieving broadband, asymmetric optical selectivity. Optical spectra coupled with numerical simulations demonstrate strong plasmonic resonance, as well as angular selectivity in a broad UV-visible to near-infrared regime. The nanostructured metamaterials in this work, which consist of highly-conductive metallic nanopillars in a durable nitride matrix, have the potential to serve as a novel hybrid material platform for highly-tailorable nanoscale metamaterial designs, suitable for high temperature optical applications.

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