The growth of tubular or vermicular structures in organic monotectic systems

Abstract

Growth fronts have been examined for several transparent organic monotectic alloys based on succinnonitrile (SCN), using a temperature gradient stage. The systems include SCN with water, glycerol, benzene, and ethanol: in the first two systems, steady state growth is possible at very low rates (<1 μm s⁻¹), while in the latter pair, nonsteady state conditions apply at all growth rates (>0.1 μm s⁻¹). At higher growth rates (≿1 μm s⁻¹) all these systems exhibit a variety of tubular or vermicular morphologies, where droplets of the minor immiscible liquid phase appear to provide a diffusion path by which the reaction can occur with localized deposition of the solid product. The remarkable growth forms are discussed with reference to a series of time-lapse micrographs and the form of a typical phase diagram.