Mercuryintrusionporosimetri

Mercuryintrusionporosimetri, also known as mercury intrusion porosimetry (MIP), is a porosimetric technique used to determine pore size distribution and porosity of solid materials by measuring the volume of mercury intruded into a sample as pressure is progressively increased. Mercury is a non-wetting liquid, so it does not spontaneously enter pores; external pressure is required to overcome capillary entry.

The method relies on the Washburn equation, which relates intrusion pressure to pore throat radius. A typical form is r = −2 γ cos θ / P, where γ is the surface tension between mercury and air, θ is the contact angle of mercury with the pore surface, and P is the applied pressure. With common values γ ≈ 0.484 N/m and θ ≈ 140°, the pressure sequence probes progressively smaller pores, from roughly a few nanometers up to tens or hundreds of micrometers. Data are collected as intrusion volume versus pressure, yielding a cumulative porosity curve and, by differentiation, a pore size distribution. Results can be influenced by assumed pore geometry (often modeled as cylindrical capillaries) and sample preparation.

Applications span ceramics, cements, soils, rocks, catalysts, polymers, and composites, where knowledge of pore structure, connectivity, and total porosity is important for performance. The technique is powerful for wide-range pore sizing but is destructive and relies on mercury, a toxic material requiring careful handling and waste management. Limitations include inaccessible pores, pore shapes that deviate from capillary models, and potential sample damage at high pressures. Standards from ASTM and ISO provide guidelines for procedures and reporting.