Pore Size Distribution - Porosimetry

Gas Adsorption Isotherms & Mercury Porosimetry

 

     Home

     Analytical Services

     Pore size distribution by 
     Gas Adsorption 
     Isotherms

     Pore size distribution by
     Mercury Porosimetry

     Density Analysis

     Contact 
Pore sizes and porosity are usually quoted in the terms of micropore, mesopore and macropore. 

The most common techniques for porosimetry analysis are Mercury Porosimetry (for the meso and macro pore range) and Gas Adsorption Isotherms (for the micro and meso pore range). More about these techniques and our analysis services is given below and on the respective pages through the links on the left. 

No single porosimetry technique can determine pore size distribution, pore volume or porosity of a sample throughout the entire range of pore sizes. 

The table below provides a guide for the categorisation of pore diameters. 

Classifications of Pore size distribution [1]

Classification

Pore diameter* range (nm)

Pore diameter* range (μm)

Pore diameter* range (Å)

Micropores

< 2.0

< 0.002

< 20

Mesopores

2 – 50

0.002 – 0.05

20 – 500

Macropores

> 50

> 0.05

> 500

 [1] Pure and Applied Chemistry, 57, No 4, (1985), 603-619.

*These ranges refer to the diameter of a cylindrical pore or the width of a slit-shaped pore. 

MCA Services offers both porosimetry techniques for the determination of the pore size distribution, pore area and pore volume distribution and the measurement of sample porosity. The choice of  technique is dependent on the expected pore sizes within the sample.


For microporous and mesoporous materials the gas adsorption technique is applied using our  Micromeritics TriStar 3020 apparatus. The pore size range covered by this technique is typically 0.55 nm to 360 nm and this forms our SC3 test from which pore size, pore area and pore volume data is reported together with surface area.

porosity testing by nitrogen gas porosimetry showing pore size distribution and pore volume measurement

Porosimetry using nitrogen gas adsorption

For materials having larger pore sizes mercury porosimetry is recommended and covers the approximate range 0.007 μm to about 600 μm (mesoporous to macroporous materials), depending on the nature of the material. This is conducted using a Micromeritics AutoPore mercury porosimeter and forms our SC11 test from which pore size, pore area and pore volume data is reported. Furthermore, this test can be extended to density and porosity measurement.

An alternative method for the determination of the total pore volume of a sample is by the combination of mercury pycnometry and helium pycnometry. A description of this technique is provided on our density analysis pages under our SC8 analysis for porosity testing. 

Naturally, each test can be conducted independently of the other, or both can be applied to a sample in order to gain data on a more complete range of pore sizes.

porosity medasurement by mercury porosimetry showing pore size distribution, pore sizes and pore volume

Porosimetry by mercury intrusion porosimetry

For further information on each technique and the data provided as part of our standard report packages please follow the links below. Alternatively the staff at MCA Services may be contacted to discuss and advise on suitable techniques for the analysis of client samples.