Thermogravimetry and DTA

Figures 4.179 and 4.180 illustrate two furnaces for TGA for different temperature ranges. The figures are self-explanatory. Several different sample holders are shown in the bottom portions of the figures. The multiple holders can be used for simultaneous thermogravimetry and DTA, the single cmcibles are used for simple thermogravimetry. The major problem for the combined thermogravimetry and DTA technique is to bring the thermocouple wires out of the balance without interference with the weighing process. Even the temperature control of the sample holder may be a major problem in vacuum experiments since the thermocouple does not touch the sample. The cmcibles are made of platinum or sintered aluminum oxide. Typical sample masses may vary from a few to several hundred milUgrams.

Figure 4.193 illustrates in its top graph the fast, explosive decomposition of ammonium picrate. At 475 K the fast, exothermic reaction takes place. The study of explosives by thermogravimetry and DTA is possible because of the small sample masses that can be used. An important branch of thermal analysis is thus the study of chemical stability of compounds that are used industrially. 

The next examples illustrate the greater detail that can be obtained when thermogravimetry and DTA are combined. The experiments can be carried out either simultaneously or successively. Figures 7.10 and 7.11 show copies of two pages from the "Atlas of Thermoanalytical Curves." The measurements were made with the Derivatograph as described in Fig. 7.6. In addition to differential thermal analysis and thermogravimetry, the derivative of the... 

Thermal analysis of metal hydrazine carboxylate hydrate complexes, M(N2H3C00)2 cH20, initially shows an endotherm due to the loss of water of hydration. This is followed by exothermic decomposition of the anhydrous salts through carbonate intermediates to the corresponding oxides, similar to anhydrous metal hydrazine carboxylates (Figure 4.3). The TG (thermogravimetry) and DTA data of some of metal hydrazine carboxylate hydrates are summarized in Table 4.3. 

The research papers which originated in the last couple of years in different countries in this field indicate that ED and Er are not generally reported and there is an emphasis on the study of comprehensive thermal behavior of explosives as a function of temperature or time by means of different thermal analytical techniques. Most commonly used methods of thermal analysis are differential thermal analysis (DTA), thermogravimetric analysis (TGA) or thermogravimetry and differential scanning calorimetry (DSC). 

Figure 14 shows typical differential thermometry and thermogravimetry curves (DTA and TGA) of DSP and crystalline poly-DSP in a helium current64. ... 

The differential calorimetric curves (DSC) of the various crystalline forms of triamterene grown from organic solutions containing water and from absolute organic solutions, and the DSC curves of triamterene crystals dried under reduced pressure have been described. The differential thermal analysis-thermogravimetry analysis (DTA-TG) thermograms are also given. 

The stability of the polyyne-type polymers can be examined by thermogravimetry and differential thermal analysis (TG/DTA). From the DTA curves in Figure 10.5, an exothermic peak is observed in all cases. The very broad peak for PpPE is observed around at 350°C, while the sharp peak is observed at 207°C for PpPB and at 138 C for PpPO, respectively. The exothermic peak temperature should be related with thermal stability of the polyyne-type polymers, thus it is concluded that the most stable is PpPE... 

As with the technique of thermogravimetry, the DTA curve is dependent on two general categories of variables (1) instrumental factors and (2) sample characteristics. The former category includes ... 

Data Recording Unit 4.3 Temperature Calibration 4.4 Sample 4.5 Atmosphere 4.6 Heating Rate 4.7 Classification of TG Curves 4.8 Calculation of Mass Change Rates 4.9 Derivative Thermogravimetry (DTG) 4.10 Intercomparison of TG and DTA 4.11 TG Reports 4.12 References 5... 

Figure 19. Thermogravimetry (TG) and DTA curves of eeramie powders in as received condition (a) kaolin (b) pottery mixture (c) brick clay (d) fly ashd ...

Thermal analysis iavolves techniques ia which a physical property of a material is measured agaiast temperature at the same time the material is exposed to a coatroUed temperature program. A wide range of thermal analysis techniques have been developed siace the commercial development of automated thermal equipment as Hsted ia Table 1. Of these the best known and most often used for polymers are thermogravimetry (tg), differential thermal analysis (dta), differential scanning calorimetry (dsc), and dynamic mechanical analysis (dma). 

The techniques referred to above (Sects. 1—3) may be operated for a sample heated in a constant temperature environment or under conditions of programmed temperature change. Very similar equipment can often be used differences normally reside in the temperature control of the reactant cell. Non-isothermal measurements of mass loss are termed thermogravimetry (TG), absorption or evolution of heat is differential scanning calorimetry (DSC), and measurement of the temperature difference between the sample and an inert reference substance is termed differential thermal analysis (DTA). These techniques can be used singly [33,76,174] or in combination and may include provision for EGA. Applications of non-isothermal measurements have ranged from the rapid qualitative estimation of reaction temperature to the quantitative determination of kinetic parameters [175—177]. The evaluation of kinetic parameters from non-isothermal data is dealt with in detail in Chap. 3.6. 

Recently we investigated ferromagnetic properties of CoPt bimetallic nanoparticles [232,233]. CoPt3 nanoparticles can be prepared by a two-step reduction using NaBH4 as a reductant. The bimetallic nanoparticles were characterized by thermogravimetry (TG) and differential thermal analysis (DTA), FT-IR, TEM) and XRD. Structural and spectroscopic studies showed that the bimetallic nanoparticles adopt an fee crystalline structure with an average particle size of 2.6 nm. SQUID studies revealed... 

Shurygina EA, Larina NK, Chubarova MA, Kononova MM. Differential thermal analysis (DTA) and thermogravimetry (TG) of soil humus substances. Geoderma 1971 6 169-177. 

The number of experimental factors which influence the results increases considerably when thermogravimetry is combined with other techniques such as DTA, gas chromatography46, mass spectrometry, X-ray etc. A systematic discussion of all these additional factors would lead too far, therefore only a representative example will be discussed here. One of the often-applied multiple techniques is the combination TG-DTA. Besides the actual thermal reactions of the sample, the important factors in DTA are the heat capacity and the thermal conductivity of the sample. Optimum heat transfer is required for such thermoanalytical measurements therefore the shape of the sample and its contact with the crucible is of special importance. 

This is another example of the application of thermogravimetry for determination of equilibrium temperatures in dissociation studies. This also enables one to calculate the heat of dissociation from the linear relation between log of dissociation pressure and 1/T. Determination of the specific heat by means of DTA was used afterwards for conversion of the heat of dissociation into the standard values of formation at 298 °K. Ba02 was chosen for these investigation56 because it has been investigated in the past by calorimetric methods and therefore gives a possibility for comparing those values obtained from static methods with those obtained from values from dynamic methods. 

Thermal analytical techniques such as thermogravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC) have all been successfully employed in studying the pyrotechnic reactions of energetic materials such as black powder, as well as of binary mixtures of the constituents. 

Differential thermal analysis (DTA) was performed in air with an OD-102 Derivatograph (MOM, Hungary) using 100 mg samples at a heating rate of 10°C/min. Differential thermogravimetry (DTG) and thermogravimetry... 

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