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Pressure dependence of the contact angle
1Thermodynamics and Kinetics Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Canada M5S 3G8.
The Journal of Physical Chemistry. B
|May 15, 2007
Summary
The contact angle between liquids and surfaces changes with pressure, a finding supported by new thermodynamic models and experiments. This research offers insights into contact angle hysteresis on smooth, homogeneous surfaces.
Area of Science:
- Thermodynamics
- Surface Science
- Physical Chemistry
Background:
- Gibbsian thermodynamics dictates contact angle dependence on pressure at the three-phase line in isothermal systems.
- A novel adsorption isotherm for solid-vapor interfaces is introduced.
- The liquid-vapor interface is modeled as spherical within a cylindrical system.
Purpose of the Study:
- To explicitly define the relationship between contact angle and pressure.
- To investigate the prediction that contact angle increases with pressure.
- To explore a potential explanation for contact angle hysteresis.
Main Methods:
- Combining a proposed adsorption isotherm with equilibrium conditions.
- Approximating the liquid-vapor interface as spherical in a cylinder.
- Experimental investigation of the predicted contact-angle-pressure dependence under thermodynamic equilibrium.
Main Results:
- A range of contact angles can be observed on smooth, homogeneous surfaces by altering pressure.
- Negative adsorption at the solid-liquid interface is indicated.
- Experimental measurements align with the predicted pressure dependence of the contact angle.
Conclusions:
- The study validates the theoretical prediction of contact angle dependence on pressure.
- Negative adsorption at the solid-liquid interface is a key factor.
- The findings offer a plausible explanation for the phenomenon of contact angle hysteresis.
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