I need to analyze the cross-section surface of highly porous granules with the SEM but I don't know how to prepare the samples. Is there anybody who have an idea of how to flatten porous and fragile granules so that I can use electronic microscopy ?
Dear Dr. Louis Gaspard,
the granules culd be embedded in resin and kindly polished (e.g. with fine emery papers applied to suitables polishing systems) to smoothen fractures for further analysis. After ultrasonic cleaning and drying, the sample can glued on the sample holder and then sent into the coater for film coating.
If the granules are nonconductive in a vacuum chamber, no clear image could be obtained with no coating. Two kinds of coating apparatus can be used in sample preparation, namely, a gold coater and a carbon coater. When we want to observe the surface morphology of the particles, the surfaces of the sample can be coated with gold film. The obtained particle surface image result clear owing to the strong conductive property of gold film. Moreover, gold film does not affect surface morphology. When surface elements of the particles needed to be analysed by EDX probe, the samples can be coated with carbon film. The atomic number of gold is high, which means that the coverage of gold film is strong, which can interfere with detection of other elements. By contrast, carbon film meets the requirements of conductivity and does not affect detection of elements other than carbon.
Good work and best regards, Pierluigi Traverso.
Louis Gaspard
Try cutting the pellet with a razor blade. There are special knives in TEM sample preparation technology.
Dear Dr. Louis Gaspard,
the granules culd be embedded in resin and kindly polished (e.g. with fine emery papers applied to suitables polishing systems) to smoothen fractures for further analysis. After ultrasonic cleaning and drying, the sample can glued on the sample holder and then sent into the coater for film coating.
If the granules are nonconductive in a vacuum chamber, no clear image could be obtained with no coating. Two kinds of coating apparatus can be used in sample preparation, namely, a gold coater and a carbon coater. When we want to observe the surface morphology of the particles, the surfaces of the sample can be coated with gold film. The obtained particle surface image result clear owing to the strong conductive property of gold film. Moreover, gold film does not affect surface morphology. When surface elements of the particles needed to be analysed by EDX probe, the samples can be coated with carbon film. The atomic number of gold is high, which means that the coverage of gold film is strong, which can interfere with detection of other elements. By contrast, carbon film meets the requirements of conductivity and does not affect detection of elements other than carbon.
Good work and best regards, Pierluigi Traverso.
Pierluigi Traverso thank you very much for this explanation. I am just afraid that during shrinkage of the resin, granules will be crushed (they have a small compression force of around 10MPa). Indeed, they are formed with a very porous powder of aerogel. Do you think that shrinkage force of the resin would be enough to break them ?
Yuri Mirgorod thank you, I will check these knives if they can be useful for my case.
Dear Louis Gaspard ,
I work on easier samples of different types (metals with different surface layers to be analyzed, very often in section). The question you ask is quite difficult, I would try with a cold resin that has the minimum shrinkage and I would use, as a first attempt, the minimum of solvent recommended by the manufacturer. If the test doesn't work, you might try putting in a little less solvent than necessary or trying to identify a more suitable resin ....
Good luck and my best regards, Pierluigi Traverso
Pierluigi Traverso I know, that is why I am looking for help here...! But thank you for these advices, I'll try with resin of lowest shrinkage and see if it works.
Louis Gaspard
Hi
A very common method is to freeze the granules in an epoxy resin and then cut and polish and analyze it. This method prevents the granules from breaking and changing the porosity structure.
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