Local mean-field study of capillary condensation in silica aerogels

TL;DR

This study uses local mean-field theory to analyze how porosity affects capillary condensation and hysteresis in fluids within silica aerogels, revealing disorder-induced phase transitions and differing adsorption/desorption behaviors.

Contribution

It introduces a lattice model combined with diffusion-limited cluster aggregation to explore porosity effects on fluid behavior in disordered silica aerogels.

Findings

Hysteresis loop shape changes from smooth to rectangular with increasing porosity.

Disorder induces out-of-equilibrium phase transitions during adsorption and desorption.

Results offer insights into helium behavior in silica aerogels.

Abstract

We apply local mean-field (i.e. density functional) theory to a lattice model of a fluid in contact with a dilute, disordered gel network. The gel structure is described by a diffusion-limited cluster aggregation model. We focus on the influence of porosity on both the hysteretic and the equilibrium behavior of the fluid as one varies the chemical potential at low temperature. We show that the shape of the hysteresis loop changes from smooth to rectangular as the porosity increases and that this change is associated to disorder-induced out-of-equilibrium phase transitions that differ on adsorption and on desorption. Our results provide insight in the behavior of $^4$He in silica aerogels.