DIFFUSION FIELD AROUND A DENDRITE GROWING UNDER MICROGRAVITY

The Ivantsov diffusion field is tested for a free dendrite growing under microgravity. We made an in situ measurement of concentration distribution around the tip of a steady-state dendrite of NH4Cl growing from an aqueous solution by means of interferometry, where the supersaturation was set by pressure control. The experimental data on the concentration diffusion field can be fitted very well by the Ivantsov solution with two parameters, the diffusion length and the supersaturation. The best fit values for the two show very good agreement with values independently estimated. This means that the tip is approximately at equilibrium, i.e., no sign of a kinetic effect is detected in the concentration at the tip. © 1995 The American Physical Society.