The Effect of Confinement on Capillary Phase Transition In Granular Aggregates

TL;DR

This study uses a 3D mean-field lattice-gas model to investigate how confinement affects capillary phase transitions in granular and porous materials, revealing less pronounced effects in granular aggregates and identifying a second-order transition in porous structures.

Contribution

It demonstrates that confinement effects are less significant in granular aggregates and links the phase transition universality class to the 3D random field Ising model.

Findings

Confinement effects are weaker in granular aggregates than in porous structures.

The phase transition is of second order near the capillary critical temperature.

Transition belongs to the 3D random field Ising model universality class.

Abstract

Utilizing a 3D mean-field lattice-gas model, we analyze the effect of confinement on the nature of capillary phase transition in granular aggregates with varying disorder and their inverse porous structures obtained by interchanging particles and pores. Surprisingly, the confinement effects are found to be much less pronounced in granular aggregates as opposed to porous structures. We show that this discrepancy can be understood in terms of the surface-surface correlation length with a connected path through the fluid domain, suggesting that this length captures the true degree of confinement. We also find that the liquid-gas phase transition in these porous materials is of second order nature near capillary critical temperature, which is shown to represent a true critical temperature, i.e. independent of the degree of disorder and the nature of solid matrix, discrete or continuous. The critical exponents estimated here from finite-size scaling analysis suggest that this transition belongs to the 3D random field Ising model universality class as hypothesized by P.G. de Gennes, with the underlying random fields induced by local disorder in fluid-solid interactions.