Within the work of our research group, the creation of aerogels is a new step, so we would like to characterize them as fully as possible. So, my question is: which difficulties may I face if I have to perform nanoindentation on aerogels, particularly polyurea aerogels?
In general, here are a few challenges on performing nanoindentation on hydro/aerogels.
1) Gels must typically be kept under a constant moisture, typically properties change between the wet and dry state.
1b) One simple way is to add a droplet of liquid medium with an eyedropper or to maintain sample immersed in liquid during the test.
2) A fluid cell tip may aid in either scenario, but is critical if performing test while immersed.
3) If gel is very soft, you may get adhesion forces especially upon removal of the load (tip withdrawal)
4) Focusing the sample can be tricky with transparent gels and if done incorrectly will lead to inaccurate "zero" point and inaccurate measurements.
Hope that helped, good luck.
The tested type of aerogel is not transparent but yes, very sensitive to moisture. And, of course i had difficulties during mounting it via normal procedure offered by Agilent using hot melt glue cause material suck the glue in and got bent. So, now I am thinking to glue it to the microscope glass first but don't know with what yet. Do you have any other suggestions how to mount it?
We have standard equipment from Agilent G200 with CSM and Berkovich tip, so I have no other options but to use it...
1) You might want to try to just simply place it on a glass slide without any adhesive. The loads you will be using are probably very small, that you dont have to worry about the sample moving laterally etc, if something does happen you should see it on load-displacement curve.
2) You can try to adhere it to glass slide with double sided tape, though if fully immersed adhesion won't last long.
3) With regular Berkovich tip you should probably test them either in dry environment, or with just a few drops of moisture.
First, be sure that your nanoindenter is suitable for this kind of experiments. Whereas most nanoindenters can apply rather high forces but allow a very small displacement of the indentation tip, you need the opposite here, i.e. you need to measure ultralow forces at high displacements. Not many apparatuses allow this. Additionally, as wet gels are very soft materials, a hemispherical tip is much preferred, not a Berkovich one.
Alain
Nanoindentation on aerogels is much difficult than hydrogels. However, there are two options to perform. If we can control pore size, below options can be helpful.
1. Tip diameter should be as small as small (approx 10 nm)
2. Use cylindrical indenter which covers the more area.
3. Do not apply larger depth of penetration. We can go up to (100 nm) which is calibrated depth.
Go through below links. It might be helpful.
http://onlinelibrary.wiley.com/doi/10.1002/app.43532/full
http://www.sciencedirect.com/science/article/pii/S0032386116301227
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