Mercury porosimetry uses mercury’s non-wetting properties to reveal key porous characteristics in solid materials. These include porosity, pore volume, pore size distribution, and apparent density. During a typical analysis, we fully submerge the sample in mercury and apply a pressure cycle. Because mercury resists wetting surfaces, higher pressure is needed to force mercury into smaller pores. It enters larger pores at lower pressures.
We apply pressures from vacuum up to 400 MPa, enabling measurement of a broad range of pore sizes. The Washburn equation translates the applied pressure into pore diameter. It incorporates mercury’s surface tension and the contact angle for accuracy. This technique allows mercury porosimetry to measure pore sizes from 4 nanometers (at 400 MPa) up to around 800 micrometers (at vacuum).
Mercury porosimetry works well for materials with broad pore size distributions or macropores. These include granules, extrudates, or larger particle-size materials. At Delft Solids Solutions, we also measure mercury’s contact angle with samples, enhancing pore size calculations for more precise results.
Comprehensive Analysis of Porosity and Density Using Mercury Porosimetry
Before mercury porosimetry analysis, we use vacuum or flow degassing to remove moisture from the material’s porous structure. This preparation step ensures accurate measurements. Mercury porosimetry not only reveals porosity within a solid (intra-particle porosity) but also provides data on the void spaces between particles (inter-particle porosity). This information helps determine various density types, including bulk density, apparent density, and, if all pores are accessible, true density. Although mercury porosimetry can estimate specific surface area, BET gas adsorption is more reliable for surface area measurements.
Low and high-pressure mercury intrusion measurements are conducted using devices like the CE Instruments Pascal 140 and 440 analyzers or the Micromeritics Autopore IV 9505 porosimeter. The typical results include a graphical representation of mercury intrusion and extrusion curves, along with data on pore size distribution, pore volume, density, and overall porosity. Analyzing the shape of these curves closely can reveal additional insights into the pore network, enhancing the depth of mercury porosimetry studies.
