Thin film modeling of crystal dissolution and growth in confinement

TL;DR

This paper develops a continuum model for crystal dissolution and growth in confined environments, revealing how different surface interactions influence contact shape and dissolution rates under load.

Contribution

The study introduces a novel lubrication-based continuum model that incorporates disjoining pressure and surface tension to analyze crystal-surface interactions.

Findings

Diverging repulsions lead to flat contacts with increasing dissolution rates under load.

Finite exponential repulsions produce sharp contacts with load-independent dissolution rates.

Viscosity and surface tension prevent the crystal from ever touching the substrate in steady-state.

Abstract

We present a continuum model describing dissolution and growth of a crystal contact confined against a substrate. Diffusion and hydrodynamics in the liquid film separating the crystal and the substrate are modeled within the lubrication approximation. The model also accounts for the disjoining pressure and surface tension. Within this framework, we obtain evolution equations which govern the non-equilibrium dynamics of the crystal interface. Based on this model, we explore the problem of dissolution under an external load, known as pressure solution. We find that in steady-state, diverging (power-law) crystal-surface repulsions lead to flat contacts with a monotonic increase of the dissolution rate as a function of the load. Forces induced by viscous dissipation then surpass those due to disjoining pressure at large enough loads. In contrast, finite repulsions (exponential) lead to sharp pointy contacts with a dissolution rate independent on the load and on the liquid viscosity. Ultimately, in steady-state the crystal never touches the substrate when pressed against it, independently from the nature of the crystal-surface interaction due to the combined effects of viscosity and surface tension.