3-DIMENSIONAL DENDRITE-TIP MORPHOLOGY

We investigated the morphology of dendrite tips through the growth and measurement of pure succinonitrile dendrites at a fixed supercooling of 0.46 K. Many current theories of dendritic growth rely on the assum ption that the tip region can be approximated by a paraboloid of revol ution. The evidence presented here suggests that this assumption becom es invalid in regions only slightly removed from the tip and well befo re the appearance of side branches. Characterization of dendrites usin g a fourth-order polynomial, with fourfold rotational symmetry, provid es a useful description of the dendrite extending to regions up to eig ht radii from the tip. This has also enabled a more precise determinat ion of the shape and size of a dendrite tip than was heretofore possib le. This includes information about the anisotropy of the interface mo rphology.