Porenradius

Porenradius, or pore radius, is a geometric characteristic of a porous material that describes the size of its void spaces. It is commonly defined as the radius of a pore throat or, for irregular pores, the equivalent radius of a pore approximated as a cylinder. The pore radius distribution, the amount of pores at each radius, controls how fluids move, how much surface is available for adsorption, and the material’s overall transport and reaction properties.

Measurement and interpretation methods include gas adsorption (for micro- and mesopores) and the derivation of pore-size distributions using BET and BJH analyses; mercury intrusion porosimetry for larger pores; X-ray or neutron imaging and micro-CT for direct visualization; and digital pore-network modeling to interpret connectivity and transport. These techniques yield cumulative and differential pore-size distributions and related parameters such as porosity and pore surface area. Pore radius is widely used in catalysis, adsorption, filtration, energy storage materials, soil science, and construction materials.

Pore sizes are commonly classified as micropores (<2 nm), mesopores (2–50 nm), and macropores (>50 nm). This classification helps relate pore structure to material performance: micropores contribute to adsorption capacity, mesopores facilitate diffusion and reaction interfaces, and macropores provide access and flow paths.

The relationship between pore radius and capillary phenomena is described by capillary pressure, often expressed in measurements as P = 2 gamma cos theta / r, where gamma is interfacial tension and theta is the contact angle. This principle underpins many porosimetry techniques and informs interpretation of pore-size distributions. Limitations include assumptions of pore shape and connectivity, which may differ from real, complex pore geometries.