Pore size distribution is a key metric in materials research and development (R&D), underlying a range of critical performance properties. Though intrinsically linked to total pore size and overall porosity, the distribution of pores within a solid body is unique in that it indicates structural complexity in much greater detail.
Most bulk solids comprise some empty spaces (apertures, cavities, voids, etc.) which often manifest in an interconnected network. When measuring pore size distribution and other important metrics of porosity, researchers only consider an accessible, contiguous open space within the sample. Isolated pockets within solids (i.e. vesicles), therefore, are not considered part of the porous structure.
This distinction is important for two primary reasons. Firstly, the accessibility of porous structures is fundamental to their functionality/performance. Secondly, most methods of measuring porosity involve fluidic intrusion.
Mercury Intrusion Porosimetry (MIP): The Basics
Pore size distribution is often calculated as a function of total pore size, which is measured using a porosimeter. The most common technique is known as mercury intrusion porosimetry (MIP), where the size of empty space within a solid is calculated as a function of the pressure regime required for a non-wetting fluid – such as mercury (Hg) – to penetrate the porous structure.
This is ideal for measuring individual pores and for acquiring the total pore volume by incrementally increasing the applied pressure. However, using MIP to determine pore size distribution requires speculative calculations that may overlook the true geometric variety of empty interconnected spaces in the solid.
Tomography: Measuring Pore Size Distribution
Tomographic imaging is preferable for measuring pore size distribution as it utilizes a true visualization of the internal pore network in a cross-sectional plane. X-rays pass through the sample and generate a picture of the amount of gas, or liquid, contained within the solid at microscale levels of resolution. This provides the most accurate insights into the structural empty space within solid samples without relying on arbitrary definitions or tenuous calculations.
At MIPAR, we specialize in fully-automated image analysis software designed to help you map and measure samples with absolute certainty. If you are using X-ray tomography to probe the empty spaces in catalysts, industrial powders, soil samples, or any other materials of interest, we can provide you with an intuitive solution for rapid and reliable data acquisition. Directly visualize and measure the closed and open porous networks of your samples with confidence, using our unprecedented image analysis engine.