Porometry

Porometry is a class of techniques used to characterize pore size distribution and related transport properties of porous materials by measuring how gases or liquids move through the pores. It is widely applied to filtration membranes, catalysts and catalyst supports, adsorbents, textiles, and pharmaceutical packaging to assess pore throat sizes and flow characteristics.

There are two primary families of porometry. Gas permeation porometry measures the flow of a non-wetting gas across a wetted sample as differential pressure is applied. By recording gas flow versus applied pressure and applying transport models, a pore size distribution and related parameters such as porosity and mean pore size can be inferred. This method provides information over a broad pore range and is suitable for materials with relatively open porosity.

Capillary flow porometry, also known as liquid displacement porometry, fills pores with a wetting liquid and then applies gas pressure on the opposite side. As pressure increases, the gas displaces the liquid from the largest pores first, producing a measurable flow. The largest pore diameter corresponding to a given breakthrough pressure is commonly estimated by D ≈ 4 γ cos θ / P, where γ is the liquid–gas surface tension, θ is the contact angle between the liquid and the pore surface, and P is the applied pressure. Repeating this across a series of pressures yields a pore size distribution focused on capillary pores.

Outputs from porometry typically include pore size distributions, cumulative porosity, and pore throat diameters. Interpretations assume certain pore geometries (often cylindrical) and consistent wetting behavior; deviations from these assumptions can affect accuracy. Porometry complements other methods such as mercury intrusion porosimetry and provides practical pore-size information for quality control and material development.