Thermogravimetric analysis, oxidation

Mixtures can be identified with the help of computer software that subtracts the spectra of pure compounds from that of the sample. For complex mixtures, fractionation may be needed as part of the analysis. Commercial instmments are available that combine ftir, as a detector, with a separation technique such as gas chromatography (gc), high performance Hquid chromatography (hplc), or supercritical fluid chromatography (96,97). Instmments such as gc/ftir are often termed hyphenated instmments (98). Pyrolyzer (99) and thermogravimetric analysis (tga) instmmentation can also be combined with ftir for monitoring pyrolysis and oxidation processes (100) (see Analytical methods, hyphenated instruments). 

The thermal degradation of TsHs and other TsRs species (R = Me, /Bu, nCsHiy, Ph) in air and an inert atmosphere has been studied by thermogravimetric analysis and shows that for TsHs incomplete sublimation tends to occur, and, in air, oxidation competes with volatalization. ... 

Typical characterization of the thermal conversion process for a given molecular precursor involves the use of thermogravimetric analysis (TGA) to obtain ceramic yields, and solution NMR spectroscopy to identify soluble decomposition products. Analyses of the volatile species given off during solid phase decompositions have also been employed. The thermal conversions of complexes containing M - 0Si(0 Bu)3 and M - 02P(0 Bu)2 moieties invariably proceed via ehmination of isobutylene and the formation of M - O - Si - OH and M - O - P - OH linkages that immediately imdergo condensation processes (via ehmination of H2O), with subsequent formation of insoluble multi-component oxide materials. For example, thermolysis of Zr[OSi(O Bu)3]4 in toluene at 413 K results in ehmination of 12 equiv of isobutylene and formation of a transparent gel [67,68]. 

The 4 1 5 phase was shown by thermogravimetric analysis to dissociate at about 160 °C to zinc oxide and the 1 1 2 phase, a process which was verified using X-ray diffraction (Sorrell, 1977). Once the 1 1 2 phase was formed it underwent characteristic dissociation at temperatures above 160 °C. 

Figure 6. Thermogravimetric analysis (TGA) of free 55 K PVP and 7.1 nm Pt-PVP nanoparticles in oxygen. Oxidative decomposition of free PVP begins at 573K, while significant weight loss due to the catalyzed oxidation of PVP on PVP-protected Pt nanoparticles occurs at 473 K. It appears that PVP layer is not a complete monolayer or the entanglement of PVP chains causes a porous polymer layer enabling oxygen diffusion to the nanoparticle surface [17]. (Reprinted from Ref [17], 2006, with permission from Springer.)...

Poly(N-phenyl-3,4-dimethylenepyrroline) had a higher melting point than poly(N-phenyl-3,4-dimethylenepyrrole) (171° vs 130°C). However, the oxidized polymer showed a better heat stability in the thermogravimetric analysis. This may be attributed to the aromatic pyrrole ring structures present in the oxidized polymer, because the oxidized polymer was thermodynamically more stable than the original polymer. Poly(N-phenyl-3,4-dimethylenepyrroline) behaved as a polyelectrolyte in formic acid and had an intrinsic viscosity of 0.157 (dL/g) whereas, poly(N-pheny1-3,4-dimethylenepyrrole) behaved as a polyelectrolyte in DMF and had an intrinsic viscosity of 0.099 (dL/g). No common solvent for these two polymers could be found, therefore, a comparison of the viscosities before and after the oxidation was not possible. 

Current from reaction 16 is proportional to the total Cu in the sample. Current from reaction 15 is proportional to (Cu2 + 2Cus+), since Cus+ oxidized twice as much iodide as Cu2+. The relative currents from reactions IS and 16 can be used to deduce the fraction of Cu in the Cus+ state. A sample whose composition was YBa2Cus0699 by reductive thermogravimetric analysis appeared to be YBa2CusOe 92 by the rotating ring-disk electrode. 

Among the procedures described in this chapter, reductive thermogravimetric analysis is the simplest, but not very accurate. For accurate analyses of slightly oxidized superconductors, the citrate-complexed copper titration is recommended. The difficult problem of assessing oxidation states of individual elements in Bi- and Tl-con-taining superconductors has not been addressed, and remains a significant challenge to analytical chemists. 

Improved heat-resistant UV compositions for optical fiber applications These compositions are nonurethane UV cure compositions that have neither carbamate moieties nor long-chain poly(alkylene oxide) soft segments and exhibit inherently better thermal stability measured by thermogravimetric analysis (TGA) than typical coatings for optical fibers based on urethane acrylate oligomers. 

Thermogravimetric analysis (TGA) is a suitable technique for the study of explosive reactions. In TGA the sample is placed on a balance inside an oven and heated at a desired rate and the loss in the weight of the sample is recorded. Such changes in weight can be due to evaporation of moisture, evolution of gases, and chemical decomposition reactions, i.e. oxidation. 

Transparent yellow iron oxide has the a-FeO(OH) (goethite) structure on heating it is converted into transparent red iron oxide with the a-Fe203 (hematite) structure. Differential thermogravimetric analysis shows a weight loss at 275 °C. Orange hues develop after brief thermal treatment of yellow iron oxide and can also be obtained by blending directly the yellow and red iron oxide powders. 

Thermogravimetric analysis (TG) under oxidizing atmosphere reveals a high-temperature exothermic weight loss of 1.5 wt.% for the TEA sample, compared to 6.6 and 9.3 wt.% for TPA and TBA nanoslabs, respectively. From IR and TG it is concluded that nanoslabs are formed in presence of TEA, but the lower TEA content and the lower intensity of the double five-ring vibration indicate that the solid contains also less structured silica. 

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