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Abstract  

The thermal decomposition of natural iowaite of formula Mg6Fe2(Cl,(CO3)0.5)(OH)16·4H2O was studied by using a combination of thermogravimetry and evolved gas mass spectrometry. Thermal decomposition occurs over a number of mass loss steps at 60°C attributed to dehydration, 266 and 308°C assigned to dehydroxylation of ferric ions, at 551°C attributed to decarbonation and dehydroxylation, and 644, 703 and 761°C attributed to further dehydroxylation. The mass spectrum of carbon dioxide exhibits a maximum at 523°C. The use of TG coupled to MS shows the complexity of the thermal decomposition of iowaite.

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probable mechanism function g (α) of the thermal decomposition reaction was deduced from multiple rate iso-temperature method, pre-exponential factor A was calculated on the basis of E a and g (α) subsequently. The kinetic ( E a , A, mechanism) and

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coordinate to the metal cations forming different carboxylate coordination compounds. In this article, we report the synthesis of nanocrystalline nickel ferrite by the thermal decomposition of some organic precursors obtained in the reaction between

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Journal of Thermal Analysis and Calorimetry
Authors: S. Šnircová, E. Jóna, R. Janík, Ľ. Lajdová, S. Lendvayová, M. Loduhová, V. Šutinská, R. Durný, P. Lizák, and S. C. Mojumdar

. The aim of this study was to investigate the effect of different steric effect of these diamines on the type of interactions with Co(II)-montmorillonite and thermal decomposition of studied materials. Experimental

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.3 Equipment and conditions The thermal decomposition behavior was measured by using a C-500 type Calvet microcalorimeter from Setaram, France, which had a high sensitivity and equipped with two 10 mL vessels. The precision of enthalpy measurement was

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Thermal decomposition of mixed oxalates

Part I: Thermogravimetric analysis of coprecipitated zinc-copper oxalates in nitrogen

Journal of Thermal Analysis and Calorimetry
Authors: B. D. Dalvi and A. M. Chavan

The thermogravimetric analysis of several coprecipitated zinc-copper oxalates in nitrogen is reported. The thermal decompositions of these mixed oxalates show a separate single step for dehydration and decomposition in the mass loss versus temperature curve. It is found that the onset temperature decreases with composition. For example, it decreases from 380‡ for zinc oxalate to 260‡ for copper oxalate. The end-product is mixed oxides and copper metal. These studies indicate the formation of an interpenetrating structure or mixed crystals during coprecipitation. Rate parameters have been calculated for dehydration and decomposition.

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Thermal decomposition of the hydrotalcite

Thermogravimetric analysis and hot stage Raman spectroscopic study

Journal of Thermal Analysis and Calorimetry
Authors: R. L. Frost, W. N. Martens, and Kristy L. Erickson

Summary  

A combination of thermogravimetry and hot stage Raman spectroscopy has been used to study the thermal decomposition of the synthesised zinc substituted takovite Zn6Al2CO3(OH)164H2O. Thermogravimetry reveals seven mass loss steps at 52, 135, 174, 237, 265, 590 and ~780C. MS shows that the first two mass loss steps are due to dehydration, the next two to dehydroxylation and the mass loss step at 265C to combined dehydroxylation and decarbonation. The two higher mass loss steps are attributed to decarbonation. Raman spectra of the hydroxyl stretching region over the 25 to 200C temperature range, enable identification of bands attributed to water stretching vibrations, MOH stretching modes and strongly hydrogen bonded CO3 2--water bands. CO3 2- symmetric stretching modes are observed at 1077 and 1060 cm-1. One possible model is that the band at 1077 cm-1is ascribed to the CO3 2- units bonded to one OH unit and the band at 1092 cm-1is due to the CO3 2- units bonded to two OH units from the Zn-takovite surface. Thermogravimetric analysis when combined with hot stage Raman spectroscopy forms a very powerful technique for the study of the thermal decomposition of minerals such as hydrotalcites.</o:p>

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The thermal decomposition of magnesium peroxoborate was studied by means of a derivatograph. It was found that the decomposition involves a sequence of reactions: dehydration and O2 evolution. The kinetic parameters were obtained in each step of the reaction. The thermal stabilities of three kinds of metal peroxoborates are discussed.

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Conflicting results have been reported by different workers on the thermal decomposition of silver carbonate, Ag2CO3. In the present study, the decomposition mechanism was elucidated by various analytical methods; gas analysis (differential thermal gas analyses) in helium, carbon dioxide and oxygen flows with and without a P2O5 trap or a KOH trap, DTA-TG in a carbon dioxide flow and high-temperature X-ray diffraction analysis in a carbon dioxide flow.

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Journal of Thermal Analysis and Calorimetry
Authors: L. Costa, G. Paganetto, G. Bertelli, and G. Camino

The thermal decomposition of SbOCl, Sb4O5Cl2 and Sb8O11Cl2 has been studied by thermogravimetry with identification of the products resulting in the condensed phase by X-ray diffraction and infrared technique. It is shown that in nitrogen SbOCl undergoes progressive stepwise thermal disproportionation to Sb2O3 and SbCl3 with formation of Sb4O5Cl2 and Sb8O11Cl2 and as intermediates. It is thus confirmed that Sb3O4Cl, suggested to be formed instead of Sb8O11Cl2, is not an intermediate of this process. An identical mechanism is observed in air but with oxidation of Sb2O3 to Sb2O4.

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