Pore

The pore ( gr πóρος Poros " opening ", " hole" ) is a very small opening, cavity or depression. A distinction is made between micro-, meso - and macropores. The corresponding material property is the porosity.

Occurrence

Pores can be found for example in biological tissues such as leaves or skin, where they allow the permeability to air, water and solutes in a membrane. Of great importance, they are in soil science and hydrogeology, where they help to determine the water and air balance significantly. Thus, the pore volume in addition to the degree of crosslinking of the pores the most important factor in the permeability dar.

Pores are formed in metals during melting and casting operations. In the melt dissolved gases still come out as the melt solidifies, the gas bubbles are trapped and form pores in the material.

In some materials, pores are intentionally created to produce an insulating or bulky form. This sets forth foam, foamed metals (eg aluminum foam ), foam glass, cellular concrete and aerogels.

The kitchen area is for frying meat often spoken of "pores" that are to be closed by a searing, but this is factually incorrect because meat has no pores than muscle tissue per se.

Pore density

The ratio of the number n of the pores to the area A is the pore density:

It is in the unit ppi ( pores per inch ) and are used as a unit of measurement for porous materials.