(160g) Simple Algebraic Formulas for the Practical Interpretation of Mercury Porosimetry Data

Mercury porosimetry is a standard laboratory characterization technique for porous materials. It is used to probe microstructure information of such materials, notably their pore-size distribution. The porous sample, first evacuated in a vacuum, is exposed to mercury under quasistatically increasing pressure, causing mercury to progressively intrude into the pore space of the sample due to capillary effects. Subsequently, the pressure can be quasistatically reduced, leading to mercury extrusion. We record the volume of mercury in the sample as a function of the imposed pressure, which often follows distinct paths for intrusion and extrusion. In practice, mercury porosimetry experiments are commonly interpreted using the “Washburn equation” [1], which uses the intrusion data alone to derive a pore-size distribution, hence disregarding the hysteretic nature of the measurements. Pore-network simulations are based on more realistic pore-scale models and predict hysteresis, but are arguably too sophisticated for the routine analysis of porosimetry data. In this work, we propose a set of simple algebraic formulas for interpreting hysteretic intrusion-extrusion porosimetry data. The model is intended as an incremental improvement over Washburn’s approach. It contains three physically meaningful fitting parameters, which captures connectivity effects, contact-angle hysteresis, and mercury entrapment in a minimal fashion. We show the model is easy to apply in practical applications, leads to better estimates of the pore-size distribution, and readily reveals qualitative features of the porous material.

[1] E. W. Washburn, Note on a method of determining the distribution of pore sizes in a porous material, P. Natl. Acad. Sci. USA (1921) 115-116.