Experimental Studies of the Crystallization of Supercooled Water

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Abstract
The crystal fabric of ice formed by the freezing of supercooled water was examined in polarized light. Drops of radius 0.1 cm were frozen by homogeneous nucleation at −33C, by various foreign particles in suspension, or by impaction on a plane single crystal ice substrate. Bulk water, volume about 1.0 cm3, was frozen by the insertion of a single crystal of ice. Between 0 and −5C crystals invariably grew with a single orientation, identical with the nucleating crystal. With decrease of temperature increasing numbers of crystals with new orientations appeared, there being several hundred per drop when nucleation took place at −33C. Drops impacting on a substrate with vertical ‘c’ axis froze with horizontal ‘c’ axis in the temperature interval −5 to −15C. When the substrate was heated to 0C, drops always took the substrate orientation, even when supercooled to −22C. Measurements of the growth rate component parallel to the basal plane of dendrites growing in water at supercooling (ΔT) down to 20C followed the relation: U=0.08ΔT1.9 cm sec −1. Dendrite arm width and spacing decreased with increase of supercooling, both following the relation 10−2/ΔT cm. Below −8C the envelope of dendrite tips in the basal plane became hexagonal and by −16C growth rate perpendicular to the basal plane became comparable with that parallel to the basal plane. Results are interpreted in terms of different kinetic processes on different crystal faces.

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