Nucleation Catalysis in Metastable Liquids: Inborn Active Sites

Abstract

A simple formalism is developed in order to analyze the nucleation activity of inborn “week” or “strong” active sites in metastable liquids which can play in nucleation kinetics a role, similar to this of heterogeneous nucleation cores. As examples are examined the influence of Bernal holes and fluctuatively formed Frenkel voids on bubble nucleation, of athermal supercritical nuclei and heterophase fluctuations, frozen-in in the thermal prehistory of the system on any process of phase formation, and of structural defects, due to change of composition or created in redox processes on crystallization. The analysis is performed in analogy with the known treatment of the influence of heterogeneous foreign cores on nucleation kinetics. Different changes of the metastable liquid are investigated, considering both isobaric thermal quenches and change of pressure at isothermal conditions. The effect of inborn active sites on both steady nucleation rate Iss and on nucleation time lag τ# is investigated. In this way the whole kinetics of nucleation is constructed using the known approximative solutions of the more general, transient theory of nucleation.