Real-time study of thin and bulk eutectic growth in succinonitrile–(d)camphor alloys

We study the directional-growth patterns of the transparent nonfaceted alloy succinonitrile–(d)camphor (SCN–DC) at eutectic concentration in thin and bulk samples using real-time observation methods. We measure in situ   the minimum-undercooling spacing λmλm and the small-spacing stability limit λcλc of the thin, quasi-lamellar patterns. We find λm2V≈10.2μm3s-1 and λc≈0.65λmλc≈0.65λm. This last result is contrary to the common conjecture that λc=λmλc=λm in lamellar patterns, but in agreement with previous experimental and numerical studies in the CBr4–C2Cl6 eutectic. In bulk samples, we observe the growth of rod-like patterns in real time. We show that these patterns do not usually achieve long-range hexagonal order after long solidification times, although their average spacing reaches a constant value, which is close to λmλm, after a relatively short transient.