Interface morphology evolution of azobenzene from the unsteady to steady state under directional solidification

Abstract

In this work, the melt-crystal interface of azobenzene at the unsteady and the steady state was in-situ investigated via directional solidification. The experimental results show that, at the unstable stage, interface morphology transforms from planar to zigzag facets at low growth rates and then to faceted dendrites at high growth rates, and the corresponding apex angles change from multiple values to one unified. At the steady state, the interface morphology of azobenzene can maintain planar or zigzag facets or faceted dendrites, and 115° is reserved in the zigzag interface or 50° in the faceted dendrites. Besides, the disappearance of fast-growing planes and the retaining of slow-growing planes contribute to the variation of apex angles from 115° to 50°. Our in-situ observation promotes further understanding of the solidification process in faceted materials.