Analysis by DTA

Apart from the additional information on heat release and phase changes given by DTA, the apparent discrepancy in the black powder 

Black powder 95 200 Endotherm - overlapping peaks from crystalline transition of KNO3, transition and fusion of sulfur and vaporisation of volatile matter from charcoal. 

KNO3 128 200 Endotherm - rhombic - trigonal crystal transition. 

Sulfur 105 110 Endotherm - rhombic-monoclinic crystal transition. 

Apart from the additional information on heat release and phase changes given by DTA, the apparent discrepancy in the black powder ignition temperatures as determined by DTA and TG is explained by the fact that in DTA, the curves are plotted as a function of sample 

Substance Mass loss FromCQ TofC) Thermal events 

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Porta et al. have reported on the structure of MA containing Zn and its stability. The phases present for precursors of Cu-ZnO catalyst were determined from the quantitative analysis by DTA and XRD. The results shown in Table 2 have demonstrated that at least up to 15 percent of zinc mono-phasic precursors with a MA structure are formed. For the precipitates with zinc content higher than 15 percent, a new phase richer in zinc, i.e., AU, starts to segregate. However, the increasing zinc concentration permits further solubility of zinc into the MA lattice. As shown in Figure 7, the decrease of the MA unit cell volume is evident up to about 30 percent of zinc, a value that may be estimated as the limit of solubility of zinc in MA. 

Crystallization, Crystallinity, and First and Second Order Transition Behaviour. Nylon 3 has been subjected to analysis by DTA and the crystallinity has been shown to increase on heating. Branching has been shown to affect the DTA trace observed and this is correlated with structural features. 

The heavy metal salts, ia contrast to the alkah metal salts, have lower melting points and are more soluble ia organic solvents, eg, methylene chloride, chloroform, tetrahydrofiiran, and benzene. They are slightly soluble ia water, alcohol, ahphatic hydrocarbons, and ethyl ether (18). Their thermal decompositions have been extensively studied by dta and tga (thermal gravimetric analysis) methods. They decompose to the metal sulfides and gaseous products, which are primarily carbonyl sulfide and carbon disulfide ia varying ratios. In some cases, the dialkyl xanthate forms. Solvent extraction studies of a large number of elements as their xanthate salts have been reported (19). 

Chemical analysis of the investigated samples has been carried out using standard methods [4]. The combined water content was determined by DTA and Infrared spectral studies in the range of 200 - 4000 cm 1. X - ray diffraction analysis was carried out with Dron - 3 using MoK radiation. 

The parent siliceous materials of the SBA-15 and MLV types were synthesised after typical procedures [2], The carbon replicas were prepared via polymerisation, catalysed by ferric chloride, of pyrrole introduced into the mesopores of matrices [3]. The products were characterised by the nitrogen adsorption, TEM, and thermal analysis (DTG, DTA). The nitrogen content in carbons was determined using elemental analysis, XPS, and EDX, while the Si and Fe contents, with XPS. The replicas of SBA-15 and MLV-0.75 are denoted as CMK-3Nx and OCM-.Nx, respectively, were x refers to the number of g of FeCl3 per 1 g of silica used for preparations. 

Probably the main weakness of DTA as a method of analysis remains the difficulty of linking the thermal changes shown on the thermogram, with the actual thermal processes taking place. It should be noted that data obtained by DTA are often similar to those available for differential scanning calorimetry. Indeed the two techniques overlap extensively and may be seen as complementary. A comparison of the two techniques is made at the end of the next section. 

The end product of the dehydroxylation of pure phases is, in all cases, hematite, but with lepidocrocite, maghemite occurs as an intermediate phase. The amount of water in stoichiometric FeOOH is 10.4 g kg , but adsorbed water may increase the overall amount released. Thermal dehydroxylation of the different forms of FeOOH (followed by DTA or TG) takes place at widely varying temperatures (140-500 °C) depending on the nature of the compound, its crystallinity, the extent of isomorphous substitution and any chemical impurities (see Fig. 7.18). Sometimes the conversion temperature is taken from thermal analysis data (e. g. DTA), but because of the dynamic nature of the thermoanalysis methods, the temperature of the endothermic peak is usually higher than the equilibrium temperature of conversion. 

Particular attention should be paid to both the stability in solution and the thermal stability. The condesation-hydrolysis equilibria of heteropolyanions in aqueous media are shown in Fig. 8. Each heteropolyanion is stable only at pH values lower than the corresponding solid line (55). Some solid heteropolyacids are thermally stable and applicable in reactions with vapor-phase reactants conducted at high temperatures. The thermal stability is measured mainly by X-ray diffraction (XRD), thermal gravimetric analysis, and different thermal analysis (TG-DTA) experiments. According to Yamazoe et al. (56), the decomposition temperatures of H3PM012O40 and its salts depend on the kinds of cations Ba2 +, Co2+ (673 K) < Cu2+, Ni2+ (683 K)[Pg.127]

All products were characterized by DTA, DTG analysis, infrared and x-ray spectra. The pressure was varied between 50 and 1,000 atm. Copolymerization with other monomers, vinyl methyl ether, propylene, and hexavinylbenzene gave products with chlorine contents of 2-15 Vinyl chloride and vinylidene chloride gave only homopolymers. 

Combustion of a pyrotechnic mixture of the two materials (studied by DTA and temperature profile analysis) attains a temperature of about 1700°C in 0.1—0.2 s. 

The thermal decomposition of 5-aminotetrazole, l-methyl-5-aminotetrazole, 1,5-diaminotetrazole, poly-l-vinyl-5-aminotetrazole, and the sodium salt of 5-aminotetrazole have been studies by thermogravimetry, thermal volumetric analysis (DSC, DTA, TVA), and EGA (Tables 19 and 20) <2002THE233>. 

The applications of simultaneous TG-FTIR to elastomeric materials have been reviewed in the past. Manley [32] has described thermal methods of analysis of rubbers and plastics, including TGA, DTA, DSC, TMA, Thermal volatilisation analysis (TVA), TG-FTIR and TG-MS and has indicated vulcanisation as an important application. Carangelo and coworkers [31] have reviewed the applications of the combination of TG and evolved gas analysis by FTIR. The authors report TG-FTIR analysis of evolved products (C02, NH3, CHjCOOH and olefins) from a polyethylene with rubber additive. The TG-FTIR system performs quantitative measurements, and preserves and monitors very high molecular weight condensibles. The technique has proven useful for many applications (Table 1.6). Mittleman and co-workers [30] have addressed the role of TG-FTIR in the determination of polymer degradation pathways. 

Differential Thermal Analysis. The unfractionated graft copolymers showed transitions between those of the homopolymers when examined by DTA. Two transitions were found for each copolymer examined. As shown in Figures 2 and 3, the Tgs decreased and the Tms increased as the percent by weight of PTHF increased. 

Mal tseva et al. investigated the decomposition of Ca(AlH4)2 by DTA experiments which showed several exothermic and endothermic reactions associated with hydrogen evolution [182]. From in situ X-ray diffraction studies and DSC analysis of solvent-free Ca(AlH4)2, it is evident that the decomposition proceeds in three steps (Eqs. (5.37)-(5.39)) [76] ... 

The type of the self-healing behavior of a self-healing powdery chemical is closely related to the pattern of the thermogravimctry-diffcrcntial thermal analysis (TG-DTA) curve which the chemical affords. In other words, it is possible, in principle, to infer the self-healing behavior of a self-healing powdery chemical to be either of the TD type or of the quasi-AC type by glancing over the TG-DTA cuiwe of the chemical, so that it is also possible to infer the equation of the thermal explosion theory applied to calculate the of the chemical to be either the Semenov equation, i.e., Eq. (17) presented in Section 1.2, or the F-K equation, i.e., Eq. (29) presented in Section 1.3, or neither equation. 

Figure 10.7 summarizes the major polymer voperties that can be measured or explored by DTA/DSC analysis (6). 

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