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Item type:Publication, Access status: with files , Relationship between structure and mechanical properties in hierarchical nanoporous gold(2026); Hierarchical nanoporosity represents a novel type of material which enables the combination of mechanical stability with a reduced solid fraction. The impact of a 2nd hierarchy level on the mechanical behavior is not yet fully understood. This thesis aims to unveil the various effects of structural parameters in hierarchical nanoporous gold on the mechanical properties. Monolithic samples of hierarchical nanoporous gold (HNPG) are produced by a three-step procedure which consists of a 1st electrochemical dealloying, a coarsening step by annealing and a 2nd electrochemical dealloying. The variation of synthesis parameters enables the independent adjustment of the ligament size and the solid fraction on the upper and the lower hierarchy level. Scanning electron microscopy (SEM) as well as small- and ultra-small-angle X-ray scattering (SAXS/USAXS) are employed for the structural analysis. In preparation for SAXS/USAXS, thin walls are cut out of the bulk material by plasma focused ion beam (PFIB). Two distinct length scales are identified for hierarchical nanoporous gold. The comparison between the ligament size or diameter determined by SEM and the ligament spacing determined by SAXS/USAXS results in a conversion factor which is dependent on the solid fraction. Furthermore, the specific surface area, which is detected on the basis of the scattering intensity, shows a good agreement with the specific surface area expected from the ligament spacing. A mechanical characterization is performed by macroscopic compression tests. Coarsening on the lower hierarchy level is accompanied by a distinct decrease of stiffness and strength if the lower level solid fraction is about 0.30, which is explained by the influence of the lower level connectivity. A reduction of stiffness and strength is detected if the ratio between the upper and the lower level ligament size is reduced to about 2. The Young's modulus is lower than expected on the basis of the modified Roberts-Garboczi-law, which is associated with the early yielding of ligaments. This assumption is supported by the general impairment of the Young's modulus by the strength. During compression, the flow stress of several HNPG variants reaches the maximum value which is estimated according to the theoretical shear strength of gold and the modified Roberts-Garboczi-law. Altogether, this thesis provides a comprehensive study on the multiple interactions between structure and mechanical behavior in hierarchical nanoporosity.Publicationtype: Doctoral Thesis50 25