THE ACTIVITY OF SUBSTRATES IN THE CATALYZED NUCLEATION OF UNDERCOOLEDMELTS AND AQUEOUS AEROSOLS

The aim of the present contribution is to analyze and to correlate the experimental evidence on the catalyzed nucleation in the crystallizat ion of undercooled melts. This is done by using a new, generalized the oretical approach accounting for both the thermodynamics of adhesion ( i.e. the interface bonding) and for correcting structural factors. Bes ide the usually considered lattice discrepancy substrate/overgrowing c rystal in the present contribution as an additional structural correct ive is introduced the polarizability of the building units of both int erface constituents. It is shown that such a combined approach gives f or the first time a way to correlate quantitatively-experiment and the ory in the case both of heterogeneous meteorolgical important nucleati on catalysis and in the crystallization of glassforming organic and in organic polymer melts. This approach leads to the possibility of predi cting further promising nucleation catalysts and especially appropriat e substrates in the induced crystallization of ice from undercooled wa ter. An additional advantage of the theoretical concept derived here i s that it allows also the determination of nucleation activity, Phi, o f amorphous substrates or of crystallization cores with distorted stru cture - i.e. in cases, where the lattice discrepancy approach is impos sible from the very beginning. Two main sources of experimental data a re used: crystallization of aqueous aerosols induced by various crysta llization cores and the heterogeneous crystallization of undercooled g lassforming melts. Thus a new solution of a classical problem is attem pted which may be of use in both meteorology and in the technical appl ications of induced nucleation by using foreign substrates.