Impurity Effects on the Basal Plane Solidification Kinetics of Supercooled Water

Abstract

Growth rates of ice on the basal plane from pure water and from dilute solutions of selected ionic salts, surfactants, and water‐soluble polymers were measured by an improved technique of capillary crystallization for supercoolings ranging from 0.03° to 0.2°C. The corresponding velocities ranged from 10^‐6 cm/sec to 5×10^‐4 cm/sec. Corrections for bulk mass transfer and heat transfer effects were applied to the kinetic data. The kinetic data for pure water, although in agreement with those of Hillig near supercoolings of 0.07°C, diverge from the earlier results toward lower velocities at both lower and higher supercoolings. The data nonetheless support the general conclusion of Hillig that growth of undamaged ice crystals on the basal plane proceeds by two‐dimensional nucleation. Both growth‐rate enhancements (up to a factor of about five) and retardations (up to a factor of about three) were observed during crystallization in the presence of additives. The type of effect and its magnitude were dependent on the nature of the additive, its concentration, and upon the degree of supercooling. Certain effects of ionic salts appear related to freezing potential phenomena reported by several earlier workers. Growth acceleration, found to occur to varying degrees with all classes of additive, may have been a consequence of dislocations introduced in the crystal by the additive during growth.