Thermodynamics and kinetics of nucleation in binary solutions

TL;DR

This paper introduces a combined thermodynamic and kinetic approach to study nucleation in binary solutions, covering both liquid and solid phases, and extends classical nucleation theory to account for surface effects and non-ideal solutions.

Contribution

It presents a novel integrated framework for nucleation analysis that incorporates surface effects and extends beyond classical nucleation theory for binary solutions.

Findings

Derived equations for equilibrium of critical nuclei.

Calculated steady-state nucleation rates using the new approach.

Extended classical nucleation theory to include surface and non-ideal solution effects.

Abstract

A new approach that is a combination of classical thermodynamics and macroscopic kinetics is offered for studying the nucleation kinetics in condensed binary solutions. The theory covers the separation of liquid and solid solutions proceeding along the nucleation mechanism, as well as liquid-solid transformations, e.g., the crystallization of molten alloys. The cases of nucleation of both unary and binary precipitates are considered. Equations of equilibrium for a critical nucleus are derived and then employed in the macroscopic equations of nucleus growth; the steady state nucleation rate is calculated with the use of these equations. The present approach can be applied to the general case of non-ideal solution; the calculations are performed on the model of regular solution within the classical nucleation theory (CNT) approximation implying the bulk properties of a nucleus and constant surface tension. The way of extending the theory beyond the CNT approximation is shown in the framework of the finite-thickness layer method. From equations of equilibrium of a surface layer with coexisting bulk phases, equations for adsorption and the dependences of surface tension on temperature, radius, and composition are derived. Surface effects on the thermodynamics and kinetics of nucleation are discussed.