Low Frequency Acoustic Resonance Studies of the Liquid-Vapor Transition in Silica Aerogel

TL;DR

This study investigates how silica aerogel affects the liquid-vapor phase transition of helium and neon using low frequency acoustic resonators, revealing complexities in defining the transition as an equilibrium phase change.

Contribution

It provides experimental insights into the influence of aerogel on fluid phase transitions, highlighting challenges in characterizing the transition as an equilibrium process.

Findings

Effective coexistence curves were mapped.

Transition detection was sometimes ambiguous.

Questions raised about the equilibrium nature of the transition.

Abstract

Fluid phase transitions in porous media are a powerful probe of the effect of confinement and disorder on phase transitions. Aerogel may provide a model system in which to study the effect of dilute impurities on a variety of phase transitions. In this paper we present a series of low frequency acoustic experiments on the effect of aerogel on the liquid-vapor phase transition. Acoustic resonators were used to study the liquid-vapor transition in two fluids (helium and neon) and in two different porosity aerogels (95% and 98%). While effective coexistence curves could be mapped out, the transition was sometimes difficult to pinpoint, leading to doubt as to whether this transition can be treated as an equilibrium macroscopic phase transition at all.