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Abstract  

The complex Mn(Nica)2Cl2 (Nica=nicotinamide) was prepared, and its decomposition was studied by means of TG and DSC. The IR spectra of the products of thermal decomposition were examined at every stage. Kinetic analysis of the first stage of thermal decomposition was performed via the TG-DTG curves, and the kinetic parameters were obtained from analysis of the TG-DTG curves with integral and differential methods. The most probable kinetic function was suggested from a comparison of the kinetic parameters. Mathematical expressions were derived for the kinetic compensation effect.

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Abstract  

Results obtained on the thermooxidative degradations of LDPE (low-density polyethylene) and NBR (nitrile-butadiene rubber) are presented. The activation energies for the thermooxidations leading to solid products were estimated. For LDPE, the activation energies obtained from non-isothermal data are in satisfactory agreement with those obtained from isothermal data. For NBR, the isothermal activation energy is ≉16% higher than the non-isothermal one. This difference is due to the morphological changes undergone by NBR during its heating at the rather high temperatures at which isothermal measurements were performed.

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Abstract  

The condensation approximation (CA) and numerical regularization procedure (RP) methods used to solve a Fredholm integral equation of the first kind describing the adsorption equilibria on a heterogeneous solid surface under isothermal conditions have been adopted in the present study to evaluate desorption energy distributions from temperature-programmed desorption (TPD) spectra. From comparisons of the computational results obtained by means of these methods on the basis of simulated TPD spectra, it follows that the CA gives stable solutions for wide desorption energy distributions and it can be used successfully for calculations from wide and clear resolved peaks in the TPD spectra. The use of the RP is more advantageous for acquisition of the distributions from closely related narrow peaks in the TPD spectra.

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Abstract  

Recently, Órfão obtained two simple equations for the estimation of the relative error in the activation energy calculated by the integral methods [2]. In this short communication, the validity of the equations has been evaluated by comparing the results calculated by the equations with the results calculated by the equation from theoretical derivation without introducing any assumption.

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Abstract  

The thermooxidative degradation of three models of oily soils was studied under non-isothermal conditions, at heating rates of 5, 10, 15 and 20�C min−1. Di-octyl-sebacate, as model for synthetic oil, was adsorbed on silica, alumina and silico-alumina, considered models for the inorganic micelle of a soil. For a kinetic analysis, the TG data were processed by three methods: Flynn-Wall-Ozawa, Friedman and NPK (Nomen-Sempere). The results indicate the NPK as the less speculative method that allows a separation of the elementary steps and at the same time a separation of the temperature, respective conversion dependent part of the reaction rate.

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Abstract  

The crystallization kinetic of the basalt glass ceramic of the oxide composition, (%): SiO2 − 50.82; Al2O3 − 12.05; Fe2O3 − 9.28; CaO − 15.48; MgO − 11.08; Na2O+K2O − 1.14; TiO2 − 0.15, with addition of 10% TiO2 as nucleating agent has been studied using thermal analysis under non-isothermal conditions. In this order, the non-isothermal DTA curves were obtained at different heating rates between 4 and 20°C min−1 in the temperature range of 25–1000°C using a Derivatograph-C (MOM, Hungary). The kinetic parameters of the crystallization process were calculated on the basis of Ozawa-Flynn-Wall, Friedman, Budrugeac-Segal and non-parametric kinetic methods.

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Abstract  

Kinetics of thermal decomposition of three structurally similar complexes Co2Cu(C2O4)3 (R-diam)2, where R is ethyl, 1,2-propyl or 1,3-propyl, was studied under non-isothermal conditions and nitrogen dynamic atmosphere at heating rates of 5, 7, 10, 12 and 15 K min−1. For data processing the Flynn-Wall-Ozawa and a modified non-parametric kinetic methods were used. By both methods the activation energy are in the range of 97–102 kJ mol−1. The formal kinetic is r=kα(1−α)2. Also a compensation effect between lnA and E was evidenced. The kinetic analysis lead to the conclusion of an identic decomposition mechanism by a single step process.

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Abstract  

The kinetics of thermal decomposition of Ca(H2PO4)2H2O under non-isothermal conditions was studied. The TG/DTG curves were obtained at five heating rates: 5, 7, 10, 12 and 20 K min–1. The kinetic analysis was performed by means of three methods: Friedman, Budrugeac–Segal and NPK by Sempere and Nomen. An important dependence of the activation energy vs. the conversion degree was observed and also a compensation effect. The decomposition consists of water loss and is due to the elimination of crystallization water and an intermolecular condensation, respectively.

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