2020 Volume 35 Issue 3 Pages 200-207
Recent manufacturing processes for high performance crystal particles require the advanced control technologies of crystal structure and morphology. In order to positively control nucleation and crystal growth, it is important to understand the crystallization behavior in the solution from a microscopic viewpoint. We have studied the crystallization behavior of aqueous micro-droplet of potassium iodide (KI) solution using electrodynamic balance (EDB), where a charged droplet could be electrically levitated in space over the periods of hours. It enabled us in situ observation of crystallization behavior in a levitated micro-droplet with enough spatial and time resolutions. In this study, we investigated the final morphology and the crystallization behavior of the produced particle from evaporation of single levitated microdroplet of aqueous KI solution using EDB coupled with optical microscope. IDG (Ink-jet Droplet Generator) or DPI (Direct Particle Injection) method was adopted for trapping the droplet in EDB. The morphologies of produced crystal particle depended on the initial droplet diameter. Multilayer crystal particle was obtained from crystallization of the large droplet (80–140 μm) and the cuboid crystal with lack of one edge was observed for the small droplet (20–40 μm). We also observed the multi-crystalline particle with cascade structure of cuboid crystals or the irregular spherical particle with shell-like structure which was produced from the small droplet with high supersaturation in the case of IDG trapping method.
