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Abstract  

The thermal transformations of Pr and La carbonates, La, Ce, Pr, Nd, Sm, Eu and Gd fluorocarbonates, and La, Nd, Dy and Ho fluorooxalates were investigated. A Derivatograph Q-1000 (MOM, Hungary) was used for thermal analysis. The kinetics of the processes was studied in a flow reactor. The activation energies and preexponential factors for dehydration and decarbonization were calculated. Samples of Pr fluorocarbonate, Ho fluorooxalate, and Pr and La carbonates were exposed to γ-irradiation (dose from 6.2·106 to 6.1·107 rad). The influence of the irradiation dose upon the kinetic parameters (E a andA) of the processes was investigated.

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Abstract  

Study of the gypsum-hemihydrate-soluble anhydrite transitions by thermal, X-ray and IR methods showed differences in the intensity of the ∼3493 cm−1 IR absorption peak of the gypsum samples and differences in the peak ratios of the DTA curve at the gypsum-hemihydrate transition. There were also differences in the temperature and rate of the γ−β anhydrite transition. This suggests that different gypsum species occur, specially among synthetic gypsum. Fifteen equations were tested in order to find models which fitted the gypsum-hemihydrate and the hemihydrate-anhydrite transitions. No model fitted all the samples. The best fit for the gypsum-hemihydrate transition in three samples was an order of reaction equation while for the hemihydrate-anhydrite transition the best fit in four samples was a power law. Differences in crystallite characteristics appear to be one of the main reasons for the differences in kinetics between the samples.

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The thermal stability of lithium-ion battery cathode could substantially affect the safety of lithium-ion battery. In order to disclose the decomposition kinetics of charged LiCoO2 used in lithium ion batteries, thermogravimetric analyzer (TG) and C80 microcalorimeter were employed in this study. Four stages of mass losses were detected by TG and one main exothermic process was detected by C80 microcalorimeter for the charged LiCoO2. The chemical reaction kinetics is supposed to fit by an Arrhenius law, and then the activation energy is calculated as E a=148.87 and 88.87 kJ mol−1 based on TG and C80 data, respectively.

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Abstract  

The kinetics of the thermal decomposition of Co3O4 has been examined in the 1123–1200 K temperature and 2.66–20.73 kPa oxygen pressure range. The kinetics of this process has been deseribed in terms of a mixed-control model of reaction. The values of activation energies of diffusion and chemical reaction as well as the observed activation energy have been given. The strong dependence of the decomposition rate on temperature and oxygen pressure has been explained.

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Results are presented on the thermal behaviour of [Fe(III)2Cu(C2C4)2(OH)4(H2O)2] precursor of copper ferrite. An investigation of the decomposition steps and intermediates was followed by a non-isothermal kinetic analysis of the processable steps.

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Abstract  

Copper(II), zinc(II) and cadmium(II) complexes of the Schiff base, fluorenone anthranilic acid were prepared and characterized by elemental analysis, magnetic measurements, conductivity experiments and electronic and infrared spectral studies. The thermal decomposition kinetics and mechanism of these chelates was studied from TG data.

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Abstract  

The thermal decomposition of Eu2(BA)6(bipy)2 (BA=C2H5N 2, benzoate; bipy=C10H8N2, 2,2'-bipyridine)and its kinetics were studied under the non-isothermal condition by TG-DTG, IR and SEM methods. The kinetic parameters were obtained from analysis of the TG-DTG curves by the Achar method, the Madhusudanan-Krishnan-Ninan (MKN) method, the Ozawa method and the Kissinger method. The most probable mechanism function was suggested by comparing the kinetic parameters. The kinetic equation for the first stage can be expressed as: dα/dt=Aexp(–E/RT)3(1–α)2/3.

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Abstract  

A modified first-order kinetic law which takes into account defect decay during an ordering process was employed to predict the short-range-order kinetics of a quenched and a quenched-deformed Cu—5 at.% Zn alloy, in conjunction with experiments performed by isothermal calorimetry. The effective activation energy of point defect migration and its temperature dependence strongly suggest the contribution of bound vacancies to the ordering process. An estimate of 91.2 kJ mol–1 was made for the activation energy of solute—vacancy migration by applying an effective rate constant, a value in very good agreement with that obtained from previous non-isothermal experiments. The isothermal curves were utilized to determine the ordering energy: w=–2.90 kJ mol–1. In conjunction, a parametric study of the defect sink density was performed in order to assess its influence on the calculated isothermal curve profiles.

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Abstract  

A micro DSC analyzer fitted with special high-pressure vessels was used to investigate the kinetics of methane hydrate formation in the water phase dispersed as a stable emulsion in deep offshore drilling fluids. At high sub-cooling conditions, the peak of hydrate formation is perfectly visible and regular-shaped, and could be fitted by a Gaussian law. The average time for hydrate crystallization of the water droplets’ population was represented as a logarithmic function of the inverse of absolute temperature. At low sub-cooling conditions, the formation appears confused with the baseline; the amount of hydrate formed was thus measured from its enthalpy of dissociation, after periods of formation of variable duration.

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Abstract  

Thermogravimetry (TG) has been used to study the oxidation of a commercial silicon nitride bonded silicon carbide (SNBSC) ceramic. The oxidation was studied in air and carbon dioxide atmospheres between 800 and 1300°C. TG/mass spectrometry (MS) shows that the silicon nitride bonding phase oxidises first. The kinetics follow a multi-stage mechanism with diffusion control. Carbon dioxide was found to be a more powerful oxidant than air at temperatures above 1050°C.

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