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Permeation
In physics and engineering, permeation (also called imbuing) is the penetration of a permeate (such as a liquid, gas, or vapor) through a solid. It is directly related to the concentration gradient of the permeate, a material's intrinsic permeability, and the materials' Mass diffusivity. Permeation is modeled by equations such as Fick's laws of diffusion, and can be measured using tools such as a minipermeameter.
== Description ==
The process of permeation involves the diffusion of molecules, called the permeant, through a membrane or interface. Permeation works through diffusion; the permeant will move from high concentration to low concentration across the interface. A material can be semipermeable, with the presence of a semipermeable membrane. Only molecules or ions with certain properties will be able to diffuse across such a membrane. This is a very important mechanism in biology where fluids inside a blood vessel need to be regulated and controlled. Permeation can occur through most materials including metals, ceramics and polymers. However, the permeability of metals is much lower than that of ceramics and polymers due to their crystal structure and porosity.
Permeation is something that must be regarded highly in various polymer applications, due to their high permeability. Permeability depends on the temperature of the interaction as well as the characteristics of both the polymer and the permeant component. Through the process of sorption, molecules of the permeant can be either absorbed or adsorbed at the interface. The permeation of a material can be measured through numerous methods that quantify the permeability of a substance through a specific material.
Permeability is measured in units of area, commonly meters squared. It can be measured in a darcy or millidarcy popularized by Henry Darcy. They are not official SI units, however they are widely used. The permeability coefficient can be calculated in Barrers. Standard SI units for temperature, time, distance and pressure are used for the gasses and diffusion coefficients used to calculate permeability.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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