Capillary condensation is the "process by which multilayer adsorption from the vapor into a porous medium proceeds to the point at which pore spaces become filled with condensed liquid from the vapor ." The unique aspect of capillary condensation is that vapor condensation occurs below the saturation vapor pressure, Psat, of the pure liquid. This result is due to an increased number of van der Waals interactions between vapor phase molecules inside the confined space of a capillary. Once condensation has occurred, a meniscus immediately forms at the liquid-vapor interface which allows for equilibrium below the saturation vapor pressure. Meniscus formation is dependent on the surface tension of the liquid and the shape of the capillary, as shown by the Young-Laplace equation. As with any liquid-vapor interface involving a menisci, the Kelvin equation provides a relation for the difference between the equilibrium vapor pressure and the saturation vapor pressure. A capillary does not necessarily have to be a tubular, closed shape, but can be any confined space with respect to its surroundings.
Capillary condensation is an important factor in both naturally occurring and synthetic porous structures. In these structures, scientists use the concept of capillary condensation to determine pore size distribution and surface area though adsorption isotherms. Synthetic applications such as sintering of materials are also highly dependent on bridging effects resulting from capillary condensation. In contrast to the advantages of capillary condensation, it can also cause many problems in materials science applications such as Atomic Force Microscopy and Microelectromechanical Systems.
Other articles related to "capillary condensation, condensation, capillary":
... the bottom of a glass cup on a wet counter top, will help to explain the idea of how capillary condensation causes two surfaces to bridge together ... Kelvin equation, where relative humidity comes into play, condensation that occurs below Psat will cause adhesion ... particle surfaces are not smooth on the molecular scale, therefore condensation only occurs about the scattered points of actual contacts between the two spheres ...
... indicates that as Pv/Psat increases inside a capillary, the radius of curvature will also increase, creating a flatter interface ... larger radii of curvature result in more vapor condensation ... angle below.) Figure 2 above demonstrates this dependence in a simple situation whereby the capillary radius is expanding toward the opening of the capillary and thus vapor condensation occurs smoothly ...
Famous quotes containing the word condensation:
“Entification begins at arms length; the points of condensation in the primordial conceptual scheme are things glimpsed, not glimpses.”
—Willard Van Orman Quine (b. 1908)