Some features of the properties of porous and composite materials

A semioctahedral model of the structure of low-porosity materials is proposed. Using this model, the percolation thresholds (critical porosities) for the permeability and the conductivity of these materials are determined. Expressions for the tortuosity of the pore space of granular and cavernous media are refined throughout the range of the permeable porosity, with the critical porosity taken into account. It is shown that porous materials and composites that are partially filled with a liquid are natural gradient materials. It is demonstrated that the properties of filters and membranes can be controlled both by varying the thickness of the permeable material and by modifying (compacting) the surface layer.