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Patterns during Evaporative Crystallization of a Saline Droplet
Virkeshwar Kumar1, Susmita Dash2
1Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India.
Langmuir : the ACS Journal of Surfaces and Colloids
|August 12, 2022
Summary
Substrate wettability and crystal shape influence saline droplet evaporation patterns. Crystal orientation controls growth, forming needle-like or globular deposits based on liquid volume and surface properties.
Area of Science:
- Materials Science
- Chemical Engineering
- Physical Chemistry
Background:
- Evaporative crystallization is crucial in various natural and industrial processes.
- Understanding droplet drying behavior is key to controlling material deposition.
- Substrate properties significantly impact crystallization outcomes.
Purpose of the Study:
- To investigate how substrate wettability and crystal morphology affect saline droplet evaporation.
- To elucidate the relationship between crystal orientation and evaporative patterns.
- To determine the influence of liquid volume on crystal shape.
Main Methods:
- Controlled experiments with saline droplets (aqueous potassium nitrate) on substrates with varying wettability.
- Microscopic observation of crystal formation and pattern development during drying.
- Analysis of droplet contact angles and liquid volume effects on crystal morphology.
Main Results:
- Superhydrophilic substrates yield long, needle-shaped crystals oriented along the substrate.
- A contact angle of ~72° results in flower-shaped crystal deposit patterns.
- Crystal orientation along the triple contact line drives self-amplifying growth.
- Reduced liquid volume leads to a transition from needle-shaped to globular crystals.
Conclusions:
- Substrate wettability and initial droplet contact angle dictate crystal morphology and deposition patterns.
- Crystal arrangement relative to the substrate and droplet interface governs evaporation and growth rates.
- Controlling substrate properties offers a method to engineer salt crystal formation and patterns.
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