How do Porosimeters work?
Mercury porosimetry exploits the fact that mercury does not wet most solids, so it enters pores only under pressure. The Washburn equation relates the applied pressure to the pore throat diameter, D = −4γcosθ/P, using a surface tension of 485 mN/m and a contact angle of about 130°. Pressure is increased stepwise from vacuum to 400 MPa while the intruded volume is recorded by a capacitance dilatometer, and extrusion on depressurization shows pore connectivity. Capillary flow porometry instead wets the sample with a low surface tension liquid and records the gas pressure needed to blow liquid from pores, giving through-pore size. Gas permeability systems measure flow through a sample at a known pressure difference, and helium pycnometers determine skeletal volume.
Which Porosimeters variants are available?
- High-Pressure Mercury Intrusion Porosimeter (up to 400 MPa) — A mercury porosimeter combining a low-pressure station and a high-pressure intensifier to cover pore throat sizes from about 3.6 nm to 400 µm.
- Low-Pressure Mercury Porosimeter for Macropore Analysis — A compact mercury porosimeter limited to about 0.2 MPa that measures macropores from roughly 7 µm to 400 µm plus bulk density.
- Capillary Flow Porometer for Membrane and Filter Pore Size — An automated instrument that wets a sample with a low surface tension liquid and measures gas flow versus pressure through wet and dry states.
- Gas Permeability Tester for Porous Ceramics and Rocks — A test system that forces gas through a cylindrical core or ceramic sample at controlled confining and differential pressure, then calculates Darcy permeability from flow rate.
- Helium Pycnometer for True Density and Closed Porosity — A gas displacement instrument that uses helium expansion between a sample chamber and a reference chamber to measure skeletal volume and true density.
How do I choose the right variant?
Choose by pore size range, sample form and the quantity that the specification reports. Mercury intrusion covers a broad span, about 3.6 nm to 400 µm, and suits rigid ceramics, rocks, cement and catalysts pellets. It is unsuitable for compressible or amalgamating samples and requires mercury handling controls. Capillary flow porometers suit membranes and filters where through-pore bubble point and mean flow pore size are required. Gas permeability testers give Darcy permeability of rocks and ceramics. Helium pycnometers supply true density and closed porosity. Check the number of high-pressure ports, maximum pressure, penetrometer volume options, automation, and whether reporting follows ISO 15901-1, ASTM D4284 or ASTM F316.
Where are Porosimeters used?
Porosimeters are specified in ceramic and refractory pore analysis, filter and membrane pore size testing, catalyst pellet macropore distribution, rock and reservoir core characterization and battery electrode porosity.
Which standards and certifications apply?
Work with Porosimeters is commonly governed by ISO 15901-1, ASTM D4284, ASTM D4404, ASTM F316 and ASTM D6226. Instrument certifications such as CE marking are confirmed per configuration and never assumed.
What are the key considerations before purchase?
Mercury instruments need containment for vapor and spills, a dedicated sink or waste procedure, and staff training under local regulations. Samples must be dried and sized to fit penetrometers, and results depend on the assumed contact angle and surface tension. Correct for mercury compression and penetrometer expansion with blank runs. Calibrate pressure transducers annually and verify with a reference material of known pore size. Capillary flow systems need wetting liquids with documented surface tension and clean, dry gas. Place high-pressure units on a rigid bench and follow pressure vessel inspection rules.
