Effects of the Magnitude and Crystallographic Direction of a Thermal Gradient on Droplet Migration in Solids

Abstract

The migration behavior of saturated water inclusions in KCl was determined as a function of both the magnitude and the orientation of an applied thermal gradient. A flattening of the droplet perpendicular to the thermal gradient was observed to intensify with increasing thermal gradient. A nonlinear relation between the droplet migration rate and the applied thermal gradient was attributed to direct and indirect effects of interface kinetics. Below a critical thermal gradient dependent on droplet size, the migration velocity becomes zero. The crystallographic orientation of the thermal gradient had only a small effect on the shapes and velocities of small droplets. In contrast, the orientation of the thermal gradient significantly influenced the behavior of larger droplets, causing some of them to adopt chevronlike shapes.