Editing Thermogravimetric analysis (section)

===Oxidation and combustion===

The simplest materials characterization is the residue remaining after a reaction.  For example, a combustion reaction could be tested by loading a sample into a thermogravimetric analyzer at [[Standard temperature and pressure|normal conditions]].  The thermogravimetric analyzer would cause ion combustion in the sample by heating it beyond its [[ignition temperature]].  The resultant TGA curve plotted with the y-axis as a percentage of initial mass would show the residue at the final point of the curve.

Oxidative mass losses are the most common observable losses in TGA.<ref name=ref11>{{cite journal | title = The Effect of Purity on High-Temperature Oxidation of Zirconium | journal = [[Oxidation of Metals]] | year = 1994 | volume = 42 | issue = 3–4 | pages = 223–237 | doi = 10.1007/BF01052024 | author1 = Voitovich, V. B. | author2 = Lavrenko, V. A. | author3 = Voitovich, R. F. | author4 = Golovko, E. I.| s2cid = 98272654 }}</ref> <!--Figure 7 shows the mass gain vs. temperature for three [[copper alloys]]. All of the mass gains of these alloys is due to oxidation. The histogram also includes the mass gain of copper alone.<ref name=ref12>{{cite journal | title = Comparison of the Oxidation Rates of Some New Copper Alloys | journal = [[Oxidation of Metals]] | year = 2003 | volume = 60 | pages = 271–291 | doi = 10.1023/A:1026019202691 | author1 = Ogbuji, L. U. | author2 = Humphrey, D. L.}}</ref> The composition of the GR-84 alloy is 8 wt.% Cu, 4 wt.% Cr and the remainder is Nb. The composition of the GC-15 alloy is copper with 0.15wt.% Al. The composition of the NAR-Z alloy is Cu-3 wt.% Al-0.5 wt.% Zr. This last alloy was the liner of the main engine of the space shuttle in 2005.<ref name=ref12>{{cite journal | title = Comparison of the Oxidation Rates of Some New Copper Alloys | journal = [[Oxidation of Metals]] | year = 2003 | volume = 60 | pages = 271–291 | doi = 10.1023/A:1026019202691 | author1 = Ogbuji, L. U. | author2 = Humphrey, D. L.}}</ref> -->

Studying the resistance to oxidation in copper alloys is very important. For example, [[NASA]] (National Aeronautics and Space Administration) is conducting research on advanced copper alloys for their possible use in [[combustion engines]]. However, oxidative degradation can occur in these alloys as copper oxides form in atmospheres that are rich in oxygen. Resistance to oxidation is significant because NASA wants to be able to reuse shuttle materials. TGA can be used to study the static oxidation of materials such as these for practical use.

Combustion during TG analysis is identifiable by distinct traces made in the TGA thermograms produced.  One interesting example occurs with samples of as-produced unpurified [[carbon nanotubes]] that have a large amount of metal [[catalyst]] present<!-- (See Figure 9)-->. Due to combustion, a TGA trace can deviate from the normal form of a well-behaved function. This phenomenon arises from a rapid temperature change.  When the weight and temperature are plotted versus time, a dramatic slope change in the first derivative plot is concurrent with the mass loss of the sample and the sudden increase in temperature seen by the thermocouple. The mass loss could result from particles of smoke released from burning caused by inconsistencies in the material itself, beyond the oxidation of carbon due to poorly controlled weight loss.

Different weight losses on the same sample at different points can also be used as a diagnosis of the sample's anisotropy. For instance, sampling the top side and the bottom side of a sample with dispersed particles inside can be useful to detect sedimentation, as thermograms will not overlap but will show a gap between them if the particle distribution is different from side to side.<ref>{{cite journal |first1=Mattia |last1=Lopresti |first2=Gabriele |last2=Alberto |first3=Simone |last3=Cantamessa |first4=Giorgio |last4=Cantino |first5=Eleonora |last5=Conterosito |first6= Luca |last6=Palin |first7=Marco |last7=Milanesio |title=Light Weight, Easy Formable and Non-Toxic Polymer-Based Composites for Hard X-ray Shielding: A Theoretical and Experimental Study| journal=International Journal of Molecular Sciences |date=January 28, 2020| volume=21 |issue=3 |page=833|doi=10.3390/ijms21030833|pmid=32012889 |pmc=7037949 |doi-access=free }}</ref><ref>{{cite journal |last1=Lopresti |first1=Mattia |last2=Palin |first2=Luca |last3=Alberto |first3=Gabriele |last4=Cantamessa |first4=Simone |last5=Milanesio |first5=Marco |title=Epoxy resins composites for X-ray shielding materials additivated by coated barium sulfate with improved dispersibility |journal=Materials Today Communications |date=20 November 2020 |volume=26 |pages=101888 |doi=10.1016/j.mtcomm.2020.101888|s2cid=229492978 }}</ref>