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MM: Fachverband Metall- und Materialphysik
MM 55: Liquid and Amorphous Materials II
MM 55.6: Vortrag
Donnerstag, 21. März 2024, 11:30–11:45, C 230
Interplay of capillary pressure and Bangham effect during imbibition in nanopores — •Juan Sanchez1,2, Lars Dammann1,2, Zhuoquing Li1,2, Laura Gallardo1,2, Robert Meissner1, Howard Stone3, and Patrick Huber1,2 — 1Hamburg University of Technology (TUHH) — 2Deutsches Elektronen-Synchrotron (DESY) — 3Princeton University
We conducted water imbibition experiments in mesoporous silica glass (Vycor) using optical imaging and high-resolution dilatometry. The interplay between surface stress release (Bangham effect) and tensile Laplace pressures on the nanopore walls led to two distinct deformation regimes. Capillary filling followed the Lucas-Washburn law, exhibiting continuous expansion of the mesoporous matrix with square-root-of-the-time dynamics. Complete pore filling resulted in the sudden matrix expansion due to the disappearance of Laplace pressure. This behavior was quantitatively described by a continuum mechanical model, considering the interplay of Bangham and Laplace pressure effects in a 3D network of cylindrical pores.
We further explored the Laplace pressure contribution by conducting imbibition experiments on unsealed porous monoliths under low humidity. In this scenario, both inward (imbibition) and outward (evaporation) flows occurred simultaneously. As the in- and out-flow rates balanced, a dynamic equilibrium (artificial tree configuration) with highly curved menisci at the liquid-gas interface was observed. As a result, there is no observable disappearance of the Laplace pressure during the dilatometry experiments.
Keywords: imbibition; evaporation; strain; porous media; nanopores