The use of DSC to study the kinetics of heterogeneous and homogeneous nucleation of ice in aqueous systems

Abstract

Differential scanning calorimetry (DSC) combined with sample dispersal in the form of an emulsion can be successfully used as a tool for studying kinetics of both homogeneous and heterogeneous nucleation of ice in an aqueous sample. Adding freeze-dried Pseudomona syringae as an ice nucleant into the filtered aqueous system before preparing the emulsion proved to be a method for inducing uniform controllable heterogeneous nucleation. Exotherms associated with the heterogeneous and homogeneous events in scanning occur at characteristic temperatures. The kinetics of both heterogeneous and homogeneous nucleation in the same sample have been studied by an isothermal hold procedure. Kinetic analysis of the individual peaks yields consistent kinetic constants. The parameters describing the temperature dependence of the nucleation kinetics are different for the heterogeneous and homogeneous nucleation processes. There is a linear relationship between freezing point depression and the reduction of nucleation temperatures associated with sucrose addition.