Crystal growth in nano-confinement: Subcritical cavity formation and viscosity effects

TL;DR

This paper models crystal cavity formation under nano-confinement, revealing how van der Waals forces and viscosity influence cavity formation, with implications for materials like calcite and sucrose.

Contribution

It introduces a continuum thin film model that captures the effects of nanoscale confinement, van der Waals forces, and viscosity on cavity formation during crystal growth.

Findings

Cavity formation becomes discontinuous with attractive van der Waals forces.

A minimum supersaturation is required for cavity formation.

High viscosity can prevent cavity formation at nanoscale confinement.

Abstract

We report on the modeling of the formation of a cavity at the surface of crystals confined by a flat wall during growth in solution. Using a continuum thin film model, we discuss two phenomena that could be observed when decreasing the thickness of the liquid film between the crystal and the wall down to the nanoscale. First, in the presence of an attractive van der Waals contribution to the disjoining pressure, the formation of the cavity becomes sub-critical, i.e., discontinuous. In addition, there is a minimum supersaturation required to form a cavity. Second, when the thickness of the liquid film between the crystal and the substrate reaches the nanoscale, viscosity becomes relevant and hinders the formation of the cavity. We demonstrate that there is a critical value of the viscosity above which no cavity will form. The critical viscosity increases as the square of the thickness of the liquid film. A quantitative discussion of model materials such as Calcite, Sodium Chlorate, Glucose and Sucrose is provided.