I have coated my adsorbent with SiO2 layer using Stober's method. I have performed the TGA for both the samples and as you can see from the images attached, they are completely different. From image 2, it is clear that the decomposition temperature is 290 degrees C but for the second image there is no degradation in the same range. So, I'm confused what should I interpret from it.
Dear Saif Mehdi,
In fact, the curves obtained appear to be from different samples. Repeat the test, under the same conditions. Were these curves obtained in an inert atmosphere (N2)? If so, I suggest that you also do it in an oxidizing atmosphere (air), to confirm whether the decomposition is influenced by fragments of the sample itself.
Check the cleanliness of the oven. Run a blank race up to 800ºC.
I look forward to your results to help you.
Yes, they are of different samples. The one in figure 1 is coated with SiO2 layer and the one in figure 2 is not coated. Both of them have been performed under inert atmosphere
Hello Saif Mehdi ,
How did you ensure that the silica coat was there? Did you perform SEM or TEM measurements?
By your TG analysis we could say that silica has a role on encapsulate the adsorbent, making it difficult to break the silica barrier, and noticing no mass loss in the TG. It could be that?
You had to perform more sensitive tests to understand what is happening there, including doing the same analysis again.
Hope it was helpful.
Regards,
Gustavo.
Saif Mehdi we have to know what's your adsorbent that you've coated. If I don't know the chemicals I'm looking at, it's impossible to guess the behaviour.
And please tell us the amount as well, because if you're using a proportion of 90% silica and 10% of an adsorbent that might decompose, you might have some problems with the sensibility of your equipment, for example.
Gustavo Henrique de Magalhães Gomes brought an important question as well: esuring that you have just a coat, or a major composite made of silica. However I don't believe this is an encapsulation problem, as your methodology leads to a high porosity silica that densifies at high temperatures (~900 ºC)
My first guess is that you're analyzing mainly silica (in mass proportions), but without details, it's impossible to be sure.
Gustavo Henrique de Magalhães Gomes I did an XRD and the adsorbent which was crystalline in nature had after coating with SiO2 showed amorphous nature as all the previous peaks had disappeared and only one broad peak at 2theta of 22 degrees.
Here is a paper where they have similarly performed SiO2 layer addition on the adsorbent.
Article Exploring a thiol-functionalized MOF for elimination of lead...
The second figure shows different stage of decomposition, but after being coated, the SiO2 slows down this decomposition. Other analyzes should be made to confirm or refute this interpretation
Abdenacer Benhammada what other analysis is required to confirm the interpretation? Will SEM and EDAX help?
Saif Mehdi the analyses of the remaining solid products (ftir... Per example) may help you to confirm the decomposition of your coated matrix.
Saif Mehdi ,
Some points were discussed here that needs attention, since you coated with SiO2 layers, it is possible that in the process you degraded the adsorbent? Did you perform calcination in your coated sample?
The XRD is expected to have those broadbands, due to the presence of amorphous silica. Another analysis is SEM with EDX mapping, you will be able to see where is the carbon and silica in your matrix and confirm the presence of your adsorbant.
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