Probing Patchy Saturation of Fluids in Nanoporous Media by Ultrasound

TL;DR

This paper demonstrates that ultrasound measurements, analyzed through Biot's theory, can effectively probe the spatial distribution of fluids within nanoporous materials, revealing patch sizes during adsorption and desorption.

Contribution

The study introduces a method to analyze ultrasonic data to estimate fluid patch sizes in nanoporous media using Biot's theory, providing new insights into fluid distribution.

Findings

Patch size during adsorption is 10-20 pore diameters.

Patch size during desorption is comparable to the entire sample.

Ultrasound can be used to assess fluid distribution uniformity.

Abstract

Nanoporous materials provide high surface area per unit mass and are capable of fluids adsorption. While the measurements of overall amount of fluid adsorbed by a nanopororus sample are straightforward, probing the fluid spacial distribution is non-trivial. We consider published data on adsorption and desorption of fluids in nanoporous glasses reported along with the measurements of ultrasonic waves propagation. We analyse these using Biot's theory of dynamic poroelasticity, approximating the patches as spherical shells. Our calculations show that on adsorption the patch diameter is on the order of 10-20 pore diameters, while on desorption the patch size is comparable to the sample size. Our analysis suggests that one can employ ultrasound to probe the uniformity of fluid spatial distribution in nanoporous materials.