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Abstract  

The thermal stabilities of bis salicylidene adipic dihydrazone derivatives and their complexes with divalent Mn, Co, Ni, Cu and Zn were studied and discussed in terms of structure and type of metal ions. TG curves display mostly four steps of thermal decomposition. The first step is due to dehydration, then the elimination of the acetate anions followed by the decomposition of the ligand in two interacting steps. The activation energies E a were evaluated and discussed in accordance with the structure of the complexes which have been previously characterized by elemental analysis and IR spectra. It was found that the activation energies of the complexes based on bis salicylidene adipic dihydrazone were higher than those of the dihydroxy derivative.

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Abstract  

The imidazolinium and benzimidazolium bromide salts with pentafluor substituents on N atom were synthesized. The structures of imidazolinium and benzimidazolium bromide salts obtained were conformed by 1H and 13C NMR, 19F NMR and elemental analysis. It was found that pyrolytic decomposition occurs with melting in salts. The imidazolinium and benzimidazolium bromide salts were studied by TG-DTG and DTA from ambient temperature to 1000°C in nitrogen atmosphere. The decomposition occurred mainly in one stage and the values of activation energy E, frequency factor A, reaction order n, enthalpy change ΔH #, entropy change ΔS # and Gibbs free energy ΔG #, of the thermal decomposition were calculated by means of Coats-Redfern (CR), MacCallum-Tanner (MC) and van Krevelen (vK) methods. The activation energy value obtained by CR and MC methods were in good agreement with each other while those obtained by vK were found to be 10–12 kJ mol−1 larger.

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Abstract  

The example of the sequence of reactions

\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $${\text{A}}\xrightarrow{{k_1 }}{\text{B}}\xrightarrow{{k_2 }}{\text{C}}$$ \end{document}
and the steady-state approximation are used to present a demonstration of the fact that the evolution of the reaction rates under non-isothermal conditions depends on the ratio of the activation energies and on the heating rate. At the same time, it is shown that, under isothermal conditions, the ratio of the activation energies plays no role.

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Abstract  

A two-pack polyurethane coating was analyzed using thermoanalytical techniques. The curing reaction, monitored using pressure differential calorimetry (PDSC), rheometry and dynamic mechanical analysis (DMA) shows the temperature dependency of activation energy and hence rate of curing. In-situ ATR-FTIR shows the formation of urethane linkage over time. The decomposition behavior carried out under non-isothermal mode using thermogravimetric analysis (TGA) shows bimodal behavior. The activation energies of the initial step (10% decomposition) from both iso and non-isothermal experiments are in very good agreement with each other. The use of dynamic mechanical analysis (DMA) shows the difference in glass transition behavior (T g) and elastic modulus (E') due to the different state of cure. Also the coating exhibits a very broad loss modulus peak (E'') indicating higher energy dissipation with deformation.

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Abstract  

In this study, four oil-shale samples (Niğde-Ulukışla) excavated from Central Anatolia Turkey were analyzed where this region is believed to have a high potential of oil in its shale rich outcrops. The samples (∼40 g) were combusted at 50 psi gas injection pressure, at an air injection rate of 1.5 L min−1 in a combustion-reaction cell. All the experiments were conducted up to 600°C. The percentages of oxygen consumption and carbon monoxide and carbon dioxide production were obtained instantaneously with respect to time. The combustion periods and relative reaction rates were determined by examining the effluent gas concentration peaks. Activation energies of the samples were determined using Weijdema’s approach. It was observed that the activation energies of the samples are varied between 22–103 kJ mol−1.

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Abstract  

The influence of aliovalent ions such as Mn, Cr, Fe, Mo, and V on the temperature and kinetics of anatase to rutile phase transformation in TiO2 heated in microwave field was studied in this work. The results indicated that heat treatment method and dopants considerably affected the anatase-to-rutile phase transition temperature and kinetics of transformation. The activation energy for anatase to rutile transformation of TiO2 derived from the isothermal data was found to be 328.4 kJ mol-1, which was considerably reduced by the addition of dopants in TiO2 matrix. The activation energy for Mo, Mn and V doped samples was 252.0, 101.3 and 96.4 kJ mol-1, respectively.

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Abstract  

Translational diffusion of poly-2,5-(1,3-phenylene)-1,3,4-oxadiazole (PMOD) in solution in 96% sulphuric acid was studied, and intrinsic viscosity was measured at different stages of thermal degradation. Polymer solution has previously been subjected to heating at temperature ranging from 75 to 104C and then investigated at 26C. A monotonic decrease in intrinsic viscosity and the molecular mass, M, of degraded products with increasing degradation temperature was detected. The rate constant of the degradation process has been obtained from the change in M of the degradation products with time at a fixed solution temperature, and the activation energy of the process was calculated by using the temperature dependence of the rate constant. The activation energy (E =1028 kJ–1 ) is close to that obtained previously for the hydrolysis of poly-2,5-(1,4-phenylene)-1,3,4-oxadiazole (PPOD) in sulphuric acid (106 kJ–1 ), the rate constant being approximately twice in the value.

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Abstract  

In this research, thermal characterization and kinetics of Karakus crude oil in the presence of limestone matrix is investigated. Thermogravimetry (TG/DTG) is used to characterize the crude oil in the temperature range of 20-900C, at 10C min -1 heating rate using air flow rate of 20 mL min -1. In combustion with air, three distinct reaction regions were identified known as low temperature oxidation (LTO), fuel deposition (FD) and high temperature oxidation (HTO). Five different kinetic methods used to analyze the TG/DTG data to identify reaction parameters as activation energy and Arrhenius constant. On the other hand different f(α) models from literature were also applied to make comparison. It was observed that high temperature oxidation temperature (HTO) activation energy of Karakus crude oil is varied between 54.1 and 86.1 kJ mol -1, while low temperature oxidation temperature (LTO) is varied between 6.9 and 8.9 kJ mol -1.

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The influence of pressure on the polyphenacylmethacrylate [poly(PAMA)] was investigated using thermal and scanning electron microscopical (SEM) methods. It is observed that the application of pressure reduces 10% of the initial glass transition temperature. A part from each of the sample was taken for thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). The activation energies were calculated by Ozawa method and significant changing was observed due to this calculation justified the effect of applying pressure.

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Abstract  

The thermal stability of push-pull 5-substituted-4-oxothiazolidines was studied by DSC, IC and X-ray diffraction techniques. It was shown that the compounds are stable in the temperature range from room temperature to melting point. The melting is combined with breaking crystal structure and forming glass material as a new phase that forms crystals by cooling it very slowly. The rate constant, activation energy as well as activation parameters of process were determined.

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