|M.Sc Student||Yarom-Reuveni Michal|
|Subject||The Kelvin Equation for Three-Phase Systems|
|Department||Department of Chemical Engineering||Supervisor||Professor Emeritus Abraham Marmur|
|Full Thesis text|
Nucleation is the process of new phase formation, beginning with the development of a distinct nucleus of a new phase from the continuous phase. The thermodynamic stability of a nucleating system has significant practical and theoretical consequences. Nucleation can be defined as two phase or three phase nucleation. The former refers to a phase change with no external site, while the latter refers to phase change on specific nucleating sites (such as solids). The subject of two-phase nucleation stability, as well as the stability for several three-phase systems, has been partially discussed in the past. However, the effect of the presence of a solid has not been completely explored.
The focus of this research is the equilibrium (Kelvin equation), stability and energy barrier of nucleating three-phase systems (solid-liquid-gas).
In this thesis we attempt to complete the solid geometry effect by studying the Gibbs formation energy of systems with various compositions in contact with solids of different geometries. The solid geometries include a plane surface, a curved, spherical surface and a conical capillary. The compositions studied include a pure component system, a simple, binary system, and a special case of a binary system containing a component present in the nucleating phase alone. The equilibrium is defined by the Kelvin equation, a basic equation in surface science relating the radius of curvature to the equilibrium vapor pressure. The stability is determined by the energy function extremum type.
Our results show that the presence of a solid can affect the critical radius size, plays a role in reducing the energy barrier, and even in stabilizing the system, in cases of capillary nucleation. The results include a thermodynamic investigation of stable boiling inside a capillary at equilibrium with a vapor pressure above the saturation pressure and a convex vapor-liquid interface. We also propose a system with a composition which has not, to our knowledge, been explored - boiling of a solution with an insoluble gas, which displays a stable equilibrium, much like the Kohler drop system.