SINGLE-STEP AND 2-STEP CALORIMETRIC STUDIES OF CRYSTALLIZATION KINETICS IN SIMPLE IONIC GLASS-FORMING LIQUIDS .1. CA(NO3)2-KNO3 SYSTEM

Isothermal calorimetric studies of crystal nucleation and growth processes in the aqueous LiCl-H2O system and the model glass-forming ionic system Ca(NO3)2-KNO3 have been investigated. For LiCl-H2O it is demonstrated that the results obtained by using emulsion samples, which protect against heterogeneous nucleation artifacts, can be reproduced by using bulk samples. For the Ca(NO3)2-KNO3 system some interference from heterogeneous nucleation is observed, but results of character rather similar to those in LiCl-H2O are obtained. These are refined by the use of two different two-step observation schedules which probe the relation between nucleation-dominated and growth-dominated regimes. The results make it possible to compare the crystallization kinetics in aqueous solutions and ionic melts and contrast them with molten fluoride systems of previous studies.