Abstract
The growth dynamics of D(2)O ice in liquid H(2)O in a microfluidic device were investigated between the melting points of D(2)O ice (3.8 °C) and H(2)O ice (0 °C). As the temperature was decreased at rates between 0.002 °C/s and 0.1 °C/s, the ice front advanced but retreated immediately upon cessation of cooling, regardless of the temperature. This is a consequence of the competition between diffusion of H(2)O into the D(2)O ice, which favors melting of the interface, and the driving force for growth supplied by cooling. Raman microscopy tracked H/D exchange across the solid H(2)O-solid D(2)O interface, with diffusion coefficients consistent with transport of intact H(2)O molecules at the D(2)O ice interface. At fixed temperatures below 3 °C, the D(2)O ice front melted continuously, but at temperatures near 0 °C a scalloped interface morphology appeared with convex and concave sections that cycled between growth and retreat. This behavior, not observed for D(2)O ice in contact with D(2)O liquid or H(2)O ice in contact with H(2)O liquid, reflects a complex set of cooperative phenomena, including H/D exchange across the solid-liquid interface, latent heat exchange, local thermal gradients, and the Gibbs-Thomson effect on the melting points of the convex and concave features.