I have an unknown sample to characterize using different techniques (mainly pore size distribution):
-X-ray computed tomography
-Mercury intrusion porosimetry
-Gas porosimetry
-BET tests for the surface area.
how would you proceed to make a perfect analysis (taking into consideration the time/money/precision factor)?
Any explanation, recommendation and/or articles for comparative studies would be a perfect help. Thank you in advance.
Moustafa
Dear Moustafa Sebaa, to quote SEM and BET. Staining sometimes helps effectively and improves microscopy. Some additional tools are dependent on whether you are organic, inorganic or an hybrid material. My Regards
Hi;
The pore structure parameters are determined indirectly from properties such as adsorptive capacity (Gaz adsorption). Direct methods produce a direct image of the microstructure (Optical microscopy).
With my best regards
Dear moustafa, I suggest you to firstly take N2 adsorption-desorption isotherm of your material, then measure pore sizes by BJH method, although you can figure out the type of the pores (micropore, mesopore, and macropore) form the type of the isotherm. Consequently, if you have a mesporous material (2nm50nm) therefore I suggest to use SEM.
For unknown materials, a BET surface area analysis (by gas adsorption) is a good place to start... this at least will reveal how much gas accessible surface there is and one can make certain inferences about the extent of meso and microporosity by combing the BET calculation with the t-plot method. A complete description of (gas accessible) micropore space requires low relative pressure gas adsorption isotherms and appropriate mathematical models (DFT, not BJH for micropores). Remember that gas molecular/atomic size plays a role in accessing the smallest of micropores; CO2 at 273K can access smaller pores than can N2 at 77K for example. Mesopore and small macropore size distribution can be done by gas adsorption up to a few hundred nm pore diameter. Gas adsorption isotherm hysteresis can reveal something about the connectivity of pores. Larger macropores are quickly evaluated using mercury intrusion porosimetry... up to ~1mm in diameter. The value of these fluid-based methods (gas adsorption and mercury intrusion) is that pore volume can be known directly, unlike diffraction and microscopy techniques. They still have a role to play of course to understand the underlying solid structure that is giving rise to the porosity. CAT scans can be useful in the meso/macro scale but cannot easily give quantitative values and of course rely on good X-ray contrast. Small angle scattering techniques really come into their own for amorphous and soft materials.
Abdelkader BOUAZIZ , Alireza Charmforoushan and Martin A Thomas , thank you for your time sharing your expertise and knowledge - This is so nice of you.
Actually Martin A Thomas has very well understood my inquiry and replied perfectly to my question.
I have just started my career in this field, and if you all do not mind, I would love to keep in touch with you for future exchange and collaboration.
Many thanks with best regards,
Moustafa
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