Nanoporous materials such as gold (np-Au) exhibit intriguing properties related to their nanoscale ligament size and high surface-area-to-volume ratio, such as elevated levels of equivalent strength and the ability to shed radiation damage to ligament surfaces. This talk will cover the behavior of np metals subjected to irradiation and to deformation, including in-situ observations of how these materials respond to such stimuli in an electron microscope.
Nanoporous metals are potentially advantageous in radiation environments, due to the high amount of ligament surface area that can act as a sink for defects produced during irradiation. Additionally, the nanoscale ligament sizes of np-Au and np-Nb lead to size effects in mechanical behavior, due to the confined deformation volumes within ligaments. In-situ TEM experiments were performed on np-Au and np-Nb samples during ion irradiation at different energies and varying total ion dose. The resulting changes in defect structure within ligaments, as well as changes in the overall porous network structure, were observed. Effects of ion irradiation were also investigated by nanoindentation of samples before and after irradiation, providing a link to mechanical properties.
The deformation of np-Au is complicated, due to the interconnected nanoscale ligaments that constitute the network configuration. Structural models have been developed to describe the deformation of materials with micron-scale porosity, but these have met limited success describing np-Au, as they assume simple modes of loading and deformation of individual ligaments. To better understand the deformation of networked np-Au, we employed scanning nanobeam diffraction to track the deformation of ligaments within a region comprising multiple ligament-pore cells, during in-situ tension testing in the TEM. Post-processing of deformation videos allowed the determination of strain fields during tensile loading and crack propagation, shedding light on the coordinated deformation of connected ligaments within a single-layer np-Au thin film.