Evaporation and crystallization process for sessile saline droplets during depressurization

Area of Science:

• Physical Chemistry
• Materials Science

Background:

• Sessile saline droplets undergo complex evaporation and crystallization during pressure changes.
• Understanding crystallization patterns is crucial for various applications, including materials processing and environmental science.

Purpose of the Study:

• To experimentally investigate the evaporation and crystallization of sessile saline droplets under depressurization.
• To elucidate the relationship between ambient pressure and resulting crystallization patterns.

Main Methods:

• Experimental study of sessile saline droplet evaporation and crystallization.
• Analysis of contact angle fluctuations during the crystallization process.
• Introduction and application of the Peclet number (Pe) to analyze ion transport dynamics.

Main Results:

• Low ambient pressure leads to salt particle formation at the droplet contact line.
• High ambient pressure (similar to atmospheric) promotes internal cubic crystal formation.
• Cubic crystal growth under high pressure or low concentration causes significant liquid-gas interface deformation and contact angle fluctuation.

Conclusions:

• Ambient pressure is a critical factor controlling saline droplet crystallization morphology.
• The Peclet number effectively quantifies the interplay between advection and diffusion, explaining pressure-dependent crystallization behaviors.
• External mass transfer dominates at low pressure, while internal diffusion is more significant at high pressure.