Good day! I need ur help seriously plz share ur idea with me.
my question is,
as far as I know there are several gases used in TGA; argon, nitrogen, oxygen and air.
I understand the reason argon and nitrogen are used is they're inert gases, therefore, showing the effect of heat degradation including carbonization.
I'm so confused about the usage of oxygen, I think oxygen gas is utilized because it can react with some components and get rid of the original specimens by disappearing into the air.
(Is that right? I wonder this answer.)
I don't figure out why air is used as a kind of gas for TGA. I guess the same condition that surrounds us is the air. That's why I guess air is sometimes employed. (is my guess right?? , if not, plz, what's the reason? )
Thank u fur ur attention and answers ! I'll study hard to give and help other people in my field!
Hello. Air and oxygen are used, for example, when you want to exactly quantify the amount of an organic species adsorbed onto a substrate (i.e. an inorganic oxide that is thermal resistant) by completely burning the organic species. In an inert gas, many organic compounds decompose forming solid carbon which can partially sublime at high temperatures ( ~1000 °C). Another reason to use both air and oxygen would be if you want to study an oxidation reaction at high temperature and the influence of the oxygen concentration.
Combustion studies are mostly performed using air (not oxygen) due to air being cheaper and less corrosive on your experimental setup.
Hello Jason,
I have worked extensively with TGA analysis. My colleagues and I ran tests in an Air environment to study the behavior of our materials in the functional environment they would be used in (the atmosphere). We utilized Nitrogen to isolate the effects of degradation and avoid any misleading oxidation reactions affecting our data.
Hope this helps.
All the best,
Eduard Fidler
There are two kind of degradation thermal and chemical. Some polymers will degrade even in the absence of oxygen just because heat breaks up their structure. In others, oxygen in air is an active ingredient in degradation mechanism, e.g. in olefins. So test environment matters.
In air some material undergo partial combustion forming char which can affect results. In Oxygen environment most organic material will go through complete combustion. Oxygen is used when you want to determine say amount of carbon in formulation.
In studying effect of stabilizers, oxygen is used to estimate Oxygen induction time (OIT). But mostly DSC is used and not TGA.
I do not use pure oxygen as much as it will destroy equipment faster.
Hello. Beyond that what was spoken until now, when you want determine the OIT (Oxidation induction team) should melting the sample in a nitrogen atmosphere and then put the oxygen. The OIT measure the onset of oxidation in the atmosphere of oxygen. By Derval
The suitable answers are given by almost everybody. Air is used as the degradation is moderate but represent actual environment. Oxygen is used mostly for avoiding dilution and any complexity during degradation. For inorganic-organic hybrid material the inorganic is mostly collected as oxide char yield and therefore, oxygen is the preferred one. Further, using pure oxygen at high temperature has its own degrading effect on instrument.
In addition to the answers listed above, heat transfer coefficient of various gases must also be considered. thanks
Hi all,
So if we want to study the amount of surface modification of some particle by some chemicals, which gas we should use for TGA?(N2 or air)
Thanks
It is correct that Nitrogen and argon gases are used so that it does not interfere during degradation. However, this is not so for some inorganic compounds, which can form nitrides.
Coming back to use of oxygen and also air, it is desired in some cases to mimic the use environment for getting exact behavior. Otherwise, for complete degradation in oxidative environment, oxygen is used. Also, without oxygen soots (Carbon particles) are left behind in sample pan. With oxygen it is completely oxidized to gaseous carbon compounds, which gives exact char yield (may be metal oxides).
hello, for example I want to burn a special material in my sample. O2 in air is needed to do the combustion reaction. I can see the weight loss in product to understand the total amount of the burnt material.
It depends on the the study, oxygen and air are for thermal degradaction accompanied by oxidation. So if you have oraganic materials with metal framework, you get oxides as a residue. But by heating the same precu in an inert atmosphere you get carbides at low temperatures and alloys or metals at higher ones. Carbonization is done in an inert atmosphere using organic precursor. In some cases you do oxidation for metal t calculate the molar mass. TGA is used for several purposes such as estimaction of carbon or oxygen contents.
Best
Hi, Asit Baran Samui what do you mean by "Further, using pure oxygen at high temperature has its own degrading effect on instrument" is it safe to apply thermal scan from 30 to 995 degrees celsius under O2 at an increasing rate of 20 °C/min ?
The heating at high temperature in presence of oxygen is likely to oxidize container and the highly oxidized products may degrade the sample cell. It is advised to restrict the temperature up to 800 degree C.
Air (or oxygen) usually is used in material science for performing oxidative studies. Also, switching the atmosphere from inert to reactive (i.e. oxygen, air) is a simple way to identify the percent carbon in a material.
Thanks all,
so to estimate the organic weight loss in hybrid materials its better to use air ???
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