By Paul Webb, Micromeritics
Mercury intrusion porosimetry is one of only a few analytical techniques that permits an analyst to acquire data over such a broad dynamic range using a single heoretical model. Mercury porosimetry routinely is applied over a capillary diameter range from 0.003 µm to 360 µm— five orders of magnitude! This is equivalent to using the same tool to measure with accuracy and precision the diameter of a grain of sand and the height of a 30-story building.
Not only is mercury porosimetry applicable over a wide range of pore sizes, but also the fundamental data it produces (the volume of mercury intruded into the sample as a function of applied pressure) is indicative of various characteristics of the pore space and is used to reveal a variety of physical properties of the solid material itself.
The information that follows falls into three main categories: I) instrument theory and its application in data collection, II) information derived from reduced data, and III) presentation of the information. A glossary of terms also is included.
Understanding how a fluid behaves under specific conditions provides insight into exactly how a mercury porosimeter probes the surface of a material and moves within the pore structure. This allows one to better understand what mercury intrusion and extrusion data mean in relation to the sample under test and allows one to understand the data outside of the bounds of the theoretical model. It also allows one to make an educated comparison between similar data obtained using other measurement techniques and theoretical models.
The information contained herein pertains for the most part to the general technique of mercury porosimetry without regard to a specific instrument manufacturer or model. However, Micromeritics' AutoPore series of porosimeters is used as a reference, particularly when examples are required and details of data reduction are presented.
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