Phase change interface stability during isochoric solidification of an aqueous solution

The stability of solid–liquid interfaces during solidification is a physical phenomenon of fundamental interest with a wide range of practical applications, including the freezing of biological matter for medical and agricultural purposes. Much of the classical research in this field treats solidification in isobaric (constant-pressure) systems in which the phase transition typically occurs under constant atmospheric pressure. Recent research has found, however, that freezing in isochoric (constant-volume) systems in which the solidifying material is confined within a high-strength constant-volume chamber held at subfreezing temperatures gives rise to many atypical physical phenomena, and understanding of the solid–liquid interface behavior under isochoric conditions is currently lacking. In this work, we study the stability and propagation of the solid–liquid interface during isochoric freezing of aqueous solutions. Using a mathematical model of heat and mass transfer during solidification coupled with multiple criteria for predicting the emergence of interfacial instabilities based on temperature and concentration gradients in the phase transition region, we find that isochoric freezing significantly stabilizes the solid–liquid interface relative to isobaric freezing, suggesting the potential for extended growth of planar, non-dendritic interfaces.