page_title: Capillary condensation
section_title: Sintering
hierarchical_section_title: Capillary condensation / Real-world applications and problems / Sintering
caption_attribution_description: English: This image describes the adsorption profile for a porous structure if the pore radii were in a uniform distribution(same) or a normal distribution(evenly different sizes).
context_page_description: Capillary condensation is the "process by which multilayer adsorption from the vapor [phase] into a porous medium proceeds to the point at which pore spaces become filled with condensed liquid from the vapor [phase]." 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 meniscus, 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.
context_section_description: Sintering is a common practice used widely with both metals and ceramic materials. Sintering is a direct application of capillary condensation, because of the adhesion effects of dust and powders. This application can be seen directly in sol-gel thin film synthesis.  The sol-gel is a colloid solution which is placed on a substrate, usually through a dip-coating method. After being placed onto the substrate, a source of heat is applied to evaporate all undesired liquid. While the liquid is evaporating, the particles that were once in solution adhere to each other, thus forming a thin film.
caption: Figure 7: Capillary condensation profile showing a sudden increase in adsorbed volume due to a uniform capillary radius (dashed path) among a distribution of pores and that of a normal distribution of capillary radii (solid path)
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