Porosimetry – Porosity Measurement
What is the porosity of a sample?
The porosity of a solid is the proportion of “empty” spaces in relation to its overall volume. The empty spaces can be filled with gas or liquid and may or may not lead to the outside of the solid. As a physical quantity, porosity is the ratio of the volume of the pores to the total volume of the material: it therefore varies between 0 and 1.
How to measure the porosity of a solid sample?
A porosimetry study makes it possible to quantify the porosity of a solid, but also to characterize the distribution of its pores. One of the techniques widely used for this type of study is mercury intrusion porosimetry. This destructive technique involves placing the sample in mercury at different pressures. The higher the mercury pressure, the more it reaches small diameter pores. The measurement of the volume of mercury included at each pressure makes it possible to obtain the distribution of the sizes of the pores of the solid.
Mercury intrusion porosity measurements are often preceded by a treatment/drying step at more or less high temperature and under vacuum in order to eliminate the volatiles present in the pores.