In the TGA of my sample , it happen to be increase in weight around 300 degree Celsius, the reason for which i found is oxidation. My question how can oxygen be present if the TGA is carried under the flow of nitrogen.
https://www.researchgate.net/post/Should_I_use_Ar_or_N2_as_atmosphere_in_DSC
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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
Ankita Singh,
The mass gain you are observing in nitrogen atmosphere is due to Archimedes' effect. Archimedes' principle states that the fluid in which a body under consideration is hanged will force the body to move upward. This weight gain is actually due to the decrease in the gas density utilized as a sample-atmosphere.
When you place your sample in nitrogen atmosphere, before starting analysis, the nitrogen gas applies upward forces on the sample and there you have to use tare command due to the deviation in weight. After taring and starting analysis, the nitrogen gas becomes less dense due to the elevation in temperature and as a result the sample hanging in nitrogen gas starts moving downward because now the gas is less dense so the sample experiences less buoyant lift and this appears as a weight gain by the sample.
The attached file also explains the same reason. I Hope it would be helpful for you.
Regards
-Umer Abid
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