Hi all
The question is related to TGA(Thermogravimetric analysis).
Thermal degradation easily understood but why do samples weight decrease?
altough just binding is broked, the weight of electrons is very low. So the weight should be maintained due to law of conservation of mass.
Some gas would be synthesized by nitrogen?
or I has missed critical logic?
Dear all, weight loss is due to all kinds of volatiles produced during the course of heating cycle. Even organic substances leaves carbonized char after the degradation ceases. My Regards
Dear Sherlock Bae , during thermal degradation, many chemical processes takes place, which includes dehydration, bond breaking between molecules, within the molecules to form byproducts like water, CO2, CO, hydrocarbons etc. As these byproducts being very volatile (easily evaporates), they leave the system at the onset of decomposition and at high temperatures, which gives a weight loss in TGA profile. TGA coupled with DTG, FTIR and Mass spectrometry will give indication of evolved gas. Irrespective of the gas which is used to perform TGA, N2, compressed air, Ar, the mechanism remains the same. But the residual weight (weight at temperature 800 to 1000 oC) varies depending on using inert gas or air. TGA of organics will result in zero residual weight, but materials contains metals will give a residual weight depending on its concentration in the material.
In your TGA profile, residual weight remains above zero, which means you have some metal nanoparticles since the TGA is performed in inert gas. If it is performed in air, the end products after measurement will be metal oxides. These can be analysed by performing XRD of the material after measurement.
Regards,
Anita
Dear all, weight loss is due to all kinds of volatiles produced during the course of heating cycle. Even organic substances leaves carbonized char after the degradation ceases. My Regards
Hi;
The thermogravimetry technique is based on the variations in mass of a material subjected either to a heating law defined by temperature steps as a function of time (isothermal mode) or to a law determined by a constant increase in the heating rate in a precisely controlled atmosphere. The device consisting of a microbalance and a heating system measures the gains or losses recorded, then by an acquisition system. Thermogravimetry thus makes it possible to obtain a quantification of the loss of elements constituting the materials and to monitor their thermal stability. A TGA/DSC instrument is synonymous with very high versatility because it combines TGA and DSC. It can be connected to a mass spectrometer or FTIR to identify the nature of the gaseous products emitted. A TGA/DSC instrument can even measure thermal events that do not cause mass variations, such as melting, glass transitions or solid-solid phase transitions.
With my best regards
Dear Sherlock Bae thank you for your question. As mentioned by Abdelkader BOUAZIZ the weight loss during your TGA measurement is due to the formation of volatile decomposition products of your sample. It depends on the molecular structure of your compound how many decomposition steps are observed.
To give you a good idea about the priniciples of thermogravimetric analysis, I highly recommend that you watch the following instructive YouTube video entitled
Thermogravimetric analysis - Online training course
https://www.youtube.com/watch?v=qaUAJ1RJqMU
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