Tailoring poisson's ratio in nanoporous metals
Citation Link: https://doi.org/10.15480/882.19316
Publikationstyp
Doctoral Thesis
Date Issued
2026
Sprache
English
Author(s)
Advisor
Referee
Title Granting Institution
Technische Universität Hamburg
Place of Title Granting Institution
Hamburg
Examination Date
2026-10-22
TORE-DOI
Citation
Technische Universität Hamburg (2026)
Poisson’s ratio is a fundamental mechanical property that reflects volumetric deformation, yet its role in nanoporous metals has received far less attention than stiffness or strength. In particular, the dependence of Poisson’s ratio on network architecture and chemical environment in nanoscale porous solids remains poorly understood. This dissertation addresses this gap by systematically investigating Poisson’s ratio in dealloyed nanoporous metals, focusing on two complementary tuning strategies: architectural hierarchy and chemo-mechanical coupling. In the first part, hierarchical nanoporous gold with nested bicontinuous network architectures was reproducibly fabricated using a three-step dealloying–annealing–dealloying route. This approach enabled independent control of two ligament length scales while maintaining monolithic, crack-free samples. Uniaxial compression combined with in-situ digital image correlation was used to measure axial and transverse strains, allowing both elastic and plastic Poisson’s ratios to be determined. The results show that Poisson’s ratio is largely insensitive to the upper-level ligament size and is governed primarily by the effective solid fraction of the load-bearing network. A scaling law for the elastic Poisson’s ratio in hierarchical network materials is proposed and experimentally validated. In the second part, the dissertation examines reversible tuning of Poisson’s ratio through chemical control. Nanoporous palladium and palladium–gold alloys were subjected to electrochemically controlled hydrogen absorption and desorption, enabling precise adjustment of hydrogen concentration under potentiostatic, near-equilibrium conditions. In nanoporous PdAu, the elastic Poisson’s ratio is reduced by nearly 50% at intermediate hydrogen concentration, in quantitative agreement with predictions from Larché–Cahn open-system elasticity. These results provide the first experimental verification of an open-system elastic Poisson’s ratio and extend validation of open-system elasticity beyond Young’s modulus. Together, this dissertation demonstrates that Poisson’s ratio in nanoporous metals is not a fixed material constant but a tunable property that can be tailored through structural design and controlled chemical loading. By linking nanoscale architecture, solute redistribution and mechanical response, this work provides a mechanistically informed basis for understanding and controlling volumetric deformation in porous metallic networks.
Subjects
Nanoporous metals
Poisson's ratio
Hierarchical nanostructures
Open-system elasticity
Hydrogen absorption
Digital image correlation
DDC Class
600: Technology