CRYSTALLIZATION AND CRITICAL SUPERCOOLING OF DISPERSE LIQUIDS

The kinetics of isothermal crystallization of disperse liquids contain ing nucleation-active seeds are analyzed in the case of each droplet o f the ensemble giving birth to one nucleus only. Expressions are deriv ed for the time dependences of the number of crystallized droplets and the fraction of crystallized volume of the ensemble. The time t1/2 fo r half-crystallization and the critical supercooling DELTAT(c) of the disperse liquid are determined as functions of the average seed number a (or, equivalently, the volume) of the droplets. It is found that as long as a > 5, the crystallization behavior of the disperse liquid is described adequately by that of the ''average'' droplet containing a seeds. When a decreases below 5, the crystallization behavior of the d isperse liquid departs appreciably from that of the ''average'' drople t, and when a approaches In 2, t1/2 and DELTAT(c) increase dramaticall y. This conforms with experiment and implies that by diminishing the s eed concentration and/or the droplet volume, the disperse liquid can b e prevented from crystallization up to that low temperature at which h omogeneous nucleation begins. The results obtained are applicable also to devitrification and polymorphic transformation of disperse solid p hases. (C) 1994 Academic Press, Inc.