Berlin 2024 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 23: Topical Session: Hydrogen in Materials: from Storage to Embrittlement III
MM 23.5: Vortrag
Dienstag, 19. März 2024, 13:00–13:15, C 130
Unprecedented switchable rigidity in a nanoporous Pd alloy-hydrogen solid solution near critical point — •Sambit Bapari1 and Jörg Weissmüller1,2 — 1Institute of Materials Physics and Technology, Hamburg University of Technology, Hamburg, Germany — 2Institute of Materials Mechanics, Helmholtz-Zentrum Hereon, Geesthacht, Germany
A remarkable prediction due to Larché and Cahn is deformation at no cost of energy at the critical point for open systems with miscibility gaps. Bulk nanoporous palladium is an ideal system for studying open system elasticity as palladium with randomly oriented nanometer size ligaments affords rapid equilibration of hydrogen between an environment and the materials bulk. In this work, nanoporous Pd-Pt (5 at%) alloy with residual Cu (13 at%) was prepared by electrochemical dealloying to experimentally verify the prediction for a wide solute-concentration range. The average ligament size of the as dealloyed nanoporous alloy is ~ 4 nm, facilitating fast equilibration with the acidic electrolyte present in the open pores under applied potential. Hydrogen solubility isotherms show near critical point behavior in the Pd-Cu-Pt-H solid solution at room temperature. Solute susceptibility and concentration-strain coefficient were determined to estimate the difference in stiffness between open and closed systems. In-situ dynamic mechanical tests show an unprecedented 50% drop in the storage modulus owing to simultaneous mechanical and chemical equilibration near critical point.
Keywords: naoporous; palladium; open system elasticity; miscibility gap; critical point