We report experimental results on quasi-two-dimensional diffusion limited
growth in directionally solidified succinonitrile with small amounts of
poly(ethylene oxide), acetone, or camphor as a solute. Seaweed growth, or dense
branching morphology, is selected by growing grains close to the {111}
plane, where the in-plane surface tension is nearly isotropic. The observed
growth morphologies are very sensitive to small anisotropies in surface tension
caused by misorientations from the {111} plane. Different seaweed
morphologies are found, including the degenerate, the stabilized, and the
strongly tilted seaweeds. The degenerate seaweeds show a limited fractal
scaling range and, with increased undercooling, suggests a transition from
"fractal" to "compact" seaweed. Strongly tilted seaweeds demonstrate a
significant twofold anisotropy. In addition, seaweed-dendrite transitions are
observed in low anisotropy growth.Comment: 12 pages, 17 figures, submitted to Phys. Rev. E, reduced image
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