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Introduction TG is a relatively straightforward and basic technique. It uses a balance and a furnace to study the effects of temperature on the mass of a sample. TG determination of decomposition temperature is a valuable

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DTA/TG coupling

Applications in the field of superconducting materials with high critical temperature

Journal of Thermal Analysis and Calorimetry
Author: J. L. Jorda

With the discovery of high temperature superconductivity an extraordinary field for investigations on new materials containing up to (more than) 8 or 9 components has been open. But, in addition to problems specifically related to superconductivity, we are faced with a prelimary difficulty: the preparation of well defined compounds which may have reproducible properties. This difficulty is smoothed out when the phase relations in the relevant systems are known. Differential Thermal Analysis (DTA) contributes to their establishment. However, in multicomponent systems, an isopletic line is expected to intercept various boundary surfaces and the analysis is obviously complicated, compared to low order systems. In addition, by the nature of high temperature superconductors the oxygen partial pressure used for their preparation is an important thermodynamic parameter which contributes to fix the oxygen content in the solid state. During heat treatments, the composition of the systems may change, due to oxygen or volatile oxides (Tl2O3, PbO2 or HgO) release. A permanent composition control then requires thermogravimetric (TG) measurements associated to DTA.

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Journal of Thermal Analysis and Calorimetry
Authors: P. Gallagher, R. Blaine, E. Charsley, N. Koga, R. Ozao, H. Sato, S. Sauerbrunn, D. Schultze, and H. Yoshida

Abstract  

Magnetic transition temperatures, Tc, are measured by simultaneous TM/DTA for Alumel, cobalt, nickel, and three alloys of Ni and Co. The observed values of Tc are corrected using the values for the melting temperatures of pure metals used to define the International Temperature Scale. These corrections are based on the simultaneous melting of these pure metals alongside, but separate from, the magnetic sample. Nine investigators, using a wide variety of instrumentation, have made these measurements utilizing a standard protocol. The results are compared for several heating rates. It is planned to make these same magnetic materials ultimately available to the public for calibration of temperature of their TG instruments.

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known that diffusion rate in oxide ceramics under such low temperatures is extremely small. TG researches have shown that the powder ferrite mass remained practically a constant at heating from 300 up to 700 K. Therefore, it is impossible to analyze the

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Abstract  

Thermogravimetry (TG), thermogravimetry coupled with mass spectroscopy (TG-MS) and thermogravimetry coupled with Fourier transform infrared spectroscopy (TG-FTIR) were used to characterise the thermo-oxidative behaviour of two intumescent coating materials. The temperature dependence, the corresponding volatile products and the amount of residue of the different processes were determined. Using both TG-MS and TG-FTIR results in an unambiguous interpretation of the volatile products. Characteristics such as the influence of endothermic reactions, the release of non-flammable gases, the dehydrogenation enhancing the char formation and the stability of the cellular char were discussed in detail. It was demonstrated, that TG, TG-MS and TG-FTIR are powerful methods to investigate mechanisms in intumescent coatings and that they are suitable methods in respect to quality assurance and unambiguous identification of such materials.

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Soot oxidation kinetics from TG experiments

Can they be used reliably in diesel particulate filter modelling tools?

Journal of Thermal Analysis and Calorimetry
Authors: Maria Kalogirou and Zissis Samaras

Abstract  

Thermogravimetric analysis (TG) has been used extensively for soot oxidation studies. Its known experimental and computational difficulties, however, have led to extended criticism concerning the reliability of the extracted kinetics and their potential for reliable reaction modelling. This study explores if TG kinetics could lead to successful simulation results notwithstanding the related disputes. For this, TG and mini-scale soot oxidation experiments with oxygen (O2) were conducted. The TG kinetics reliability was controlled through comparison with the corresponding mini-scale results and by the satisfactory simulation of the mini-scale experiments.

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powerful tool in the characterization of MAP, as structural water (H 2 O(s)) and ammonium ions (NH 4 + ) are readily evolved on heating. Previous studies using thermogravimetric analysis (TG) and differential thermal analysis (DTA) revealed endothermic

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Abstract  

Characterization of the solid-state form (hydrate or polymorph) of a pharmaceutical active is a key scientific and regulatory requirement during development of and prior to seeking approval for marketing of the drug product. A variety of analytical methods are available to perform this task. By nature of the fundamental information it provides, TG-DTA offers advantages over other methods in regards to monitoring and quantitation of hydration state changes. In a single experiment with only a few milligrams of sample, TG-DTA perceives minor changes in phase, quantitates total water content and percent conversion, and illustrates hydrate type. All of this is accomplished without the necessity of generating time-consuming standard curves representing the differing ratios of hydrated to anhydrous forms. This study describes the use of TG-DTA to monitor and quantitate humidity induced solid–solid phase conversion of nitrofurantoin and risedronate. Percent conversion was qualitatively observed by both TG and DTA signals and quantitated by the TG.

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Kinetic analyses using simultaneous TG/DSC measurements

Part II: Decomposition of calcium carbonate having different particle sizes

Journal of Thermal Analysis and Calorimetry
Authors: J. P. Sanders and P. K. Gallagher

Summary  

The thermal decomposition of CaCO3was studied using simultaneous TG/DSC for two different ranges of particle size from the same source and a physical mixture of each. The difference in kinetic behavior was as expected qualitatively, but significantly different quantitatively. In addition, the mixture did not behave as a simple combination of its end members. These discrepancies are attributed to the problems associated with mass and thermal transport. The TG data again proved easier to fit than the DSC data.

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Abstract  

A thermogravimetric method has been developed and is suggested for both the qualitative and quantitative phase analyses of high-calcium lime and calcium speciation as well. Two complementary TG measurements are proved to be satisfactory for the determination of moisture, calcium oxide, calcium hydroxide and calcium carbonate contents as well as total mineral impurities in high-calcium limes: quicklime, hydrated lime and limestone.

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