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interstices or capillaries between the structural elements of a solid. Open pore canals, which permeate the entire volume of a porous body, are differentiated from closed pore cells. The first are characteristic of adsorbents, catalysts, and various filtering materials; the second are prevalent in such substances as foam materials and volcanic glass.

According to the classification system developed by M. M. Dubinin, pores are classed by size into micropores (mean effective radius r < 15–16 Å), intermediate poreso (16–20 < r < 2,000 À), and macropores (from r > 2,000 Á to a pore size visible to the naked eye). There are two types of micropores: fine (r > 6–7 A), as in zeolites and activated carbon, and large (6–7 < r < 15–16 Å), as in certain silica gels. Each pore class has its own principles of adsorption and of other physical phenomena. Micropores correspond to the sizes of molecules or atoms in a solid and do not disturb its homogeneity. For example, the absorption of gases or liquids by microporous sorbents involves permeating the pores of these sorbents; in many way such absorption is similar to diffusion.

Macropores and intermediate pores, found in typically heterogenous materials, substantially exceed molecular size. In polymers, they exceed the size of monomer units in the macromolecule. A reduction in pressure causes a viscous, mass flow of liquids and gases in connecting macropores, whereas only diffusion is possible in micropores.

The aggregate of the size and number of pores in a body, that is, the total space occupied by pores, is termed porosity. Porosity is expressed by the volume of pores per unit volume or mass of the porous body, as well as by the body’s specific surface. Controlled and natural porous substances are widely used in technology. The porosity of rocks and soils determines the intensity and nature of many processes associated with heat and mass exchange in the earth’s crust and on the earth’s surface.


Gregg, S., and K. Sing. Adsorbtsiia, udel’naia poverkhnost’ poristost’, Moscow, 1970. (Translated from English.)
Dubinin, M. M. “Porous Structure and Adsorption Properties of Active Carbons.” In Chemistry and Physics of Carbon, vol. 2. New York, 1966. Page 51.


References in periodicals archive ?
A jelly Inside the pores turns out to be a highly efficient proton conductor.
Sun exposure damages the elasticity of the skin by affecting the collagen and elastin fibres leading to enlarged pores.
For this reason, the pore sizes in the 3D model may be a little exaggerated compared to the actual sizes of the corresponding pores.
2]] X Number of pores of area i)/Total area [[micro][m.
The conventional system had more small pores spread more evenly through the entire aggregate.
Following the same trend of random changes in total porosity in LVAd, the pore number also changed with the occurrence of rainfall, ranging from 390 pores at T0 to 545 at T3, 253 at T5 and 364 at T10 (Table 2).
In this study we describe the morphology (pore distribution and arrangement) and meristics (pore count) of the sensorial cephalic pores in Chilean Galaxiidae.
Pores may be more prominent on the nose, cheeks and chin where one has most oil glands.
The kit claims to reduces pore appearance by 25% after just one use.
We've developed the first membrane that consists of a high density of sub-nanometre-scale pores in an atomically thin, single sheet of graphene," said graduate student Sean O'Hern of MIT, who is working on the research along with Rohit Karnik, associate professor of mechanical engineering.
Anodising at 15[degrees]C led to the larger pores diameter which is around 92 nm and the pores were uniformly distributed on the substrate surface.
It made large pores around my nose and cheeks noticeably less visible.