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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  

In the present work, the Coats-Redfern method was used to determine the kinetic parameters and the possible reaction mechanism of the thermal degradation of ultra-high molecular mass polyethene and its composites with fiber monocrystals in static air at three different heating rates − 6, 10 and 16 K min−1. The analysis of the results obtained showed that the thermal degradation process of pure ultra-high molecular mass polyethene corresponded to a diffusion controlled reaction (three-dimentional diffusion, mechanism D3), while its composites with fiber monocrystals degraded by two concurrent mechanisms (diffusion one D3 and A1,F1 mechanism). The fiber monocrystals used increased the thermal stability of the composite materials obtained. The values of the activation energy, frequency factor, the changes of entropy, enthalpy and Gibbs energy for the active complex of the composites were calculated.

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Abstract  

The non-isothermal decomposition kinetics of 4Na2SO4·2H2O2·NaCl have been investigated by simultaneous TG-DSC in nitrogen atmosphere and in air. The decomposition processes undergo a single step reaction. The multivariate nonlinear regression technique is used to distinguish kinetic model of 4Na2SO4·2H2O2·NaCl. Results indicate that the reaction type Cn can well describe the decomposition process, the decomposition mechanism is n-dimensional autocatalysis. The kinetic parameters, n, A and E are obtained via multivariate nonlinear regression. The n th-order with autocatalysis model is used to simulate the thermal decomposition of 4Na2SO4·2H2O2·NaCl under isothermal conditions at various temperatures. The flow rate of gas has little effect on the decomposition of 4Na2SO4·2H2O2·NaCl.

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The thermal decomposition process of the complex [Cu(NBOCTB)][Cu(NO3)4] H2O has been studied by TG and DTG technique, and possible intermediates of the thermal decomposition have also been conjectured from the TG and DTG curves. The results suggest that the decomposition of the complex involves five steps:

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Abstract  

The kinetics of ZnFe2 O4 and ZnCr2 O4 formation under non-isothermal conditions using DTA is discussed. It was determined activation energy and kinetic model for studied reactions in the case of used various sources of starting materials (ferric pigments, chromic oxides). The activation energies for ZnFe2 O4 are positioned in a range of 200–475 kJ mol−1 (in dependence of used ferric pigments) and in case of ZnCr2 O4 in a range of 130–160 kJ mol−1 . The autocatalytic kinetic model (Šestk-Berggren) was found to be the most convenient description of the studied processes.

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Abstract  

A new method was proposed for determining the most probable mechanism function of a solid phase reaction. According to Coats-Redfern's integral equation Eβ→0 was calculated by extrapolating β to zero using a series of TG curves with different heating rates. Similarly, Eα→0 was calculated according to Ozawa's equation. The most probable mechanism function of the solid phase dehydration of manganese(II) oxalate dihydrate was confirmed to be G(α)=(1-α)1/2 by comparing Eα→0 with Eβ→0.

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Abstract  

The gasification with carbon dioxide of residual carbons prepared from Timahdit and Tarfaya oil shale kerogens has been studied by thermal analysis techniques (TG and DTA) under heating rates varying from 5 to 48C min-1. The reactions obey first order kinetics. Activation energies have been calculated by several methods, such as Kissinger, Chen-Nuttall and Coats-Redfern methods, and are broadly comparable with literature data for similar carbons.

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The existing methods of approach to solve the integral in the Arrhenius equation (Coats-Redfern, Gorbachev, Zsakó, Balarin etc.), when the standard linearization method of the integral kinetic equation is applied in order to determine the value of the activation energyE, yield factually identical results. Hence attempts to find more accurate approaches have no practical sense.

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