I've noticed that each time I run blank sample for TGA (cleaning process), it always shows a weight gain. Is that possible my Sample Pan has been contaminated? If yes, is that possible it was metal element? Because I'm planning to send my sample pan for EDX to see whether got any metal element or not on the Sample Pan.
FYI, I'm using Purified Nitrogen gas. (HiQ from Linde)
Brand: Mettler Toledo
Model: TGA/DSC1
The is something I don't understand: is this mass increase happening
1) when you perform a blank measurement, and subsequently your sample measurement, using the blank subtraction, having a look at your sample's curve?
or
2) when you are running a blank measurement, and having a look at the blank curve?
If this weight gain in the blank measurement is symmetrical (at the end of the measurement it decreases to the starting level) and looks like in the attached link, then it is completely normal. It is called the buoyancy effect. If it does not look similar to that, you might have a problem with the sample pans. You should also check that the sample pan is nicely centered on the sample carrier etc.
https://www.cementscience.com/wp-content/uploads/2013/04/correction.jpg
I totally agree with Birgit Maaten. The similar phenomenon was also observed in my TGA experiments. Actually, this is attributed to the 'buoyancy effect' which is caused by the decrease of gas density at the beginning of temperature rising. Therefore, i think that the decrease of the pan's buoyancy is an important factors for the weight gain.
Hello
Try running a blank (an empty pan) and record the data. Afterwards, when you run your sample, subtract the blank from your actual sample. Hopefully, this should solve your problem.
All the best
Hi,
Please try to clean the sample holder and run blank at higher temperature than the sample profile. Possibly, it may be due to contamination or it may be chemical change in the sample due to oxidation.
Good luck
It will be very useful to know the temperature range of your analysis, the buoyancy effect increases with the temperature range, if it's a cleaning process for sure the temperature range could be very wide (30ºC to 1000ºC, or something similar).
If you need to publish your data or you need high accuracy in the measure it's mandatory to run a blank and subtract it for each different experiment.
Other possibility is you have been use dirty crucibles, you can reuse the alumina crucibles but you must clean them in every experiment at a higher temperature of the maximum of your TGA (around 1200ºC), but this issue is more related with decrease of mass.
Possible reasons for weight gain detection in TGA were discussed elsewere at this forum:
https://www.researchgate.net/post/Why_my_TGA_graph_shows_a_weight_gain https://www.researchgate.net/post/What_is_the_process_to_get_a_weight_Gain_in_TGA https://www.researchgate.net/post/What_are_the_reasons_for_weight_gain_in_TG_curve_My_sample_is_Cement_and_the_weight_gain_is_in_the_temp_range_of_400_to_650_degree
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