C - Lublin

- pores available from two sides (two-side open),
- connected pores,
- pore nets or clusters – systems of interconnected pores (channels, voids,
cavities).
The shape of natural pores is usually nonuniform. Their complicated build-up
for calculation purposes is usually approximated by selected geometrical models.
Among many models (slit-like, ink-bottle, conical, globular etc.) the most
frequently used is a cylindrical pore model.
According to the dimension of pores, that is connected with the method of their
measurement, one distinguishes:
From point of view of capillary condensation process, Dubinin proposed the
following classification:
- macropores: more than 200 nm in radius; in such pores no capillary condensation
occurs but they may be important in diffusion transport of molecules,
- mesopores: 2 - 200 nm in radius; in these pores capillary condensation occurs,
- micropores: less than 2 nm in radius; in these pores no capillary condensation
occurs, but volumetric filling with adsorbate vapor.
A popular soil science classification (Luxmoore) is based on water retention
(pF curve) in soils and is related to plant water availability. One distinguishes
capillary and noncapillary (aeration) pores. The boundary between the above is 20
µm in diameter (pF = 2,2). In pores larger than 20 µm (macropores) the water is
passed through with gravitational force.
Less than 20 µm, capillary pores are divided on criteria of water availability for
plants:
- storing easily available water, d = 20 - 3 µm (pF = 2,2 - 3)
- storing difficult available water, d = 3 - 0,2 µm (pF = 3 - 4,2)
- storing unavailable water, microcapilary pores, d < 0,2 µm (pF > 4,2).
Smart classified pores according to image resolution:
- for an eye - larger than 200 µm
- for microphotography – larger than 6 µm
- for optical microscopy – larger than 0,2 µm.
Geenland had distinguished:
- bonding pores (