Heterogeneous nucleation on rough surfaces: Generalized Gibbs' approach.

Area of Science:

• Thermodynamics
• Surface Science
• Physical Chemistry

Background:

• Heterogeneous nucleation is crucial for phase transitions in various natural and industrial processes.
• Understanding nucleation on defective surfaces is key to controlling condensation phenomena.
• The van der Waals equation of state and generalized Gibbs approach are fundamental in describing vapor-liquid systems.

Purpose of the Study:

• To investigate heterogeneous nucleation of liquid droplets from vapor on a defective solid surface.
• To analyze the influence of surface roughness, specifically a conic void, on nucleation kinetics.
• To determine the effect of vapor overcooling on nucleation parameters like contact angle and catalytic factor.

Main Methods:

• Modeling vapor condensation using the van der Waals equation of state.
• Applying the generalized Gibbs approach to account for droplet size-dependent parameters.
• Analyzing nucleation on a model defective surface: a conic void.
• Comparing nucleation rates on defective versus planar surfaces.

Main Results:

• Nucleation rate increases significantly on a hydrophilic conic void compared to a planar surface.
• Surface roughness and vapor overcooling affect contact angle and catalytic factor.
• The presence of a conic void shifts the spinodal to lower supersaturation.
• Decreasing the void cone angle reduces the metastability region.

Conclusions:

• Defective surfaces, particularly hydrophilic conic voids, act as potent sites for enhanced heterogeneous nucleation.
• Surface geometry and material properties (hydrophilicity) critically influence nucleation pathways and rates.
• The study provides insights into controlling condensation by manipulating surface defects and operating conditions.