Vapor-gas/liquid nucleation experiments: A review of the challenges

摘要

The formation of new phase embryos is described by nucleation theory. However, nucleation is not yet fully understood. The goal of this review is to summarize measurement methods and recent experimental results for vapor/liquid nucleation. Substantial inconsistencies have been reported among experimental data that may originate from the use of different experimental approaches. These inconsistencies lead to the hypothesis that typical vapor/liquid nucleation rate measurements include an uncontrolled parameter. One such parameter might be the carrier gas that can be considered as an independent nucleation component for vapor-gas/liquid systems. Mass-spectrometry measurements suggest this possibility. The most commonly applied theories suggest a variety of responses of nucleation rates to nature and pressure of the carrier gas. Some approaches to interpret vapor-gas/liquid nucleation experiments consider nuclei formation from the vapor-gas system as a binary process. This approach can be considered in terms of converting the line that originates from isothermal nucleation of a single component system to a surface representing the isothermal nucleation of a binary system. In the binary approximation, adjusted nucleation conditions (i.e. consistent trajectories for nucleation parameters) are needed to obtain consistent data for nucleation rates across the nucleation rate surface. This framework provides an opportunity to resolve the data inconsistencies. Recommendations for future vapor-gas/liquid nucleation research can then be formulated. Experimental detection of singularities in the nucleation rate surface and phase transitions in a condensed phase are reviewed. The assumptions needed for the interpretation of the empirical parameters are analyzed. The experimental data inconsistencies make it currently impossible to suggest a standard system that would permit testing the performance of measuring systems for vapor-gas/liquid nucleation.