Growth of Solutal Ice Dendrites Studied by Optical Interferometry

Abstract

Optical interferometry was used to study ice dendrite growth in a homologous series of sugar solutions, chosen in order to probe the effect of solute diffusion coefficient on solutal ice dendrite growth. Solute concentration fields, three-dimensional dendrite morphologies, and dendrite growth velocities were measured, and the results were compared with predictions from the modified Ivantsov and solvability theories of dendrite growth. The dendrites were not axially symmetrical but had a parabolic profile parallel to the basal plane and were surrounded by a paraboloidal solute concentration field, in accordance with the Ivantsov predictions combined with anisotropic growth kinetics. Solvability theory, for a system governed by solute diffusion, accounted for the relation between the dendrite tip morphology and the growth velocity, with a value of 0.006 ± 0.001 measured for the stability parameter, σ*, from the basal tip radius. Different values were measured when the dendrites were formed in an imposed temperature gradient, which was ascribed to the increased importance of nonequilibrium effects in these cases.