From the peculiarities of Temperature-programmed reduction (TPR) method and using the Sestak–Berggren conversion function, we describe first the TPR curve simulation procedure. The influence of the Sestak–Berggren exponents on the TPR peak maximum and shape is demonstrated, by analyzing several synthetic TPR profiles. Finally, the kinetic parameters of Au/CeO2 promoted with yttrium as well as those of Au/CeO2–Al2O3 promoted with V2O5 are discussed.

The authors present their results concerning the decomposition in air of the homopolynuclear coordination compound [CoC2O4·2.5H2O] n . In the temperature range 20–300 °C, the heating curves TG, DTG and DTA allowed to evidence three decomposition steps. The kinetic analysis was performed on the second step which proved to be the only workable one. The application of nonlinear regression procedure shows that this is a complex process consisting in three successive steps. The checking of the mechanism and corresponding kinetic parameters for quasi-isothermal data (T = 150 °C) shows that the obtained results could be used for prediction of the thermal behaviour of the investigated compound in both isothermal and non-isothermal conditions.

The homopolynuclear coordination compound [CoL · 2.5H2O]n with L=C2O4 2− was synthesized by a new unconventional method. It consist in the redox reaction between 1,2-ethanediol and cobalt nitrate in presence of nitric acid. The coordination compound was characterized by chemical analysis, electronic and vibrational spectra respectively, thermal analysis. In the coordination compound the Co(II) ion exists in a high spin octahedral configuration and oxalate anion acts as double-bridge ligand, tetradentate, similar as in CoC2O4 · 2H2O obtained by the classical method. Nonstoichiometric oxide, Co3O4+0.25 with deficit in cobalt and normal spinel Co3O4 where identified as thermal decomposition intermediates. As final product of decomposition, the oxide CoO was obtained.

The paper presents the experimental results of the structural investigations and thermal analysis of copper(II) oxalate, a polynuclear coordination compound, obtained by a new method, through the reaction of 1,2-ethanediol with Cu(NO3)2·3H2O.

The thermo-oxidative degradation of an epoxy resin obtained by curing of an industrially produced DGEBA mixture with 4,4′-methylene-dianiline (MDA) and used as electric insulator has been investigated by TG+DTG+DSC simultaneous analyses performed in static air atmosphere, at five heating rates. TG, DTG and DSC curves showed that, in the temperature range 25–900°C, a glass transition followed by three thermo-oxidative processes occur. The processing of the non-isothermal data corresponding to the first process of thermo-oxidation was performed by using Netzsch Thermokinetics – A Software Module for Kinetic Analysis. The dependence of the activation energy, evaluated by isoconversional methods, on the conversion degree and the relative high standard deviations of this quantity show that the investigated process is a complex one. The mechanism and the corresponding kinetic parameters were determined by multivariate non-linear regression program and checked for quasi-isothermal data. It was pointed out that the first process of thermo-oxidation of the investigated resin consists in four steps, each step having a specific kinetic triplet. The obtained results were used for prediction of the thermal lifetime of the material corresponding to some temperatures of use and the end point criterion 5% and 10% mass loss.

The possibility to determine the kinetic parameters for temperature programmed reduction of Cu/Fe3O4 using only one TPR profile is analyzed. The same data are analyzed both by Friedman’s iso-conversional method and another one previously derived and published by the authors. One shows that taking into account the experimental restrictions of Monti and Baiker, the Friedman’s method, although gives values of the activation energy smaller than the real values, indicates a very similar dependence of these on the reduction degree. On the basis of some synthetic data one shows that the errors are very large when these recommendations are neglected, being possible to determine a false dependence on the degree of reduction.

A new synthesized 4CN type azomonoether, exhibiting dying properties, crystalline nature and generating interest as a material for non-linear optical applications was investigated. Modern devices incorporating liquid crystals tend to use thin films of such materials because of their special characteristics. Thermal stability studies are indispensable before attempting any deposition experiment.

Coordination compounds may be used as efficient precursors for fabrication of semiconducting layers. Thermal stability of such a potential precursor - [Cd{SSi(O-tBu)(3)}(S2CNEt2)](2) - was investigated (tBu means tert-butyl and Et means ethyl). The kinetic study was performed by means of different multi-heating rate methods: isoconversional (Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose and Friedmann) methods associated with the criterion of the independence of the activation parameters on the heating rate. The kinetic triplet of the non-isothermal decomposition of this Cd(II) complex was established.

For the most common kinetic models used in heterogeneous reactions, the dependencies on x m = E/RT m (E is the activation energy, T m is the temperature corresponding to maximum process rate, R is the gas constant) on the relative errors (e%) in the determination of the activation energy from the slope of the Kissinger straight line ln(β / T m 2 ) vs. 1/T m (β is the heating rate) are evaluated. It is pointed out that, for x m≥10.7 and all kinetic models, ∣e%∣≤5%. Some possible cases exhibiting high values of ∣e%∣, which can be higher than 10%, are put in evidence and discussed.

The kinetic parameters (reaction order, n, activation energy, E, pre-exponential factor, A, constant rate, k) for the dehydration step due to elimination of osmotic water and hydrogen-bounded water with the carboxylic groups, and for the anhydrifying step owing to the dehydration of two neighboring (-COOH) groups, were determined under non-isothermal conditions for some carboxylic resins with acrylic-divinylbenzene (DVB) matrix. The kinetic parameters were evaluated by means of isoconversional methods from (TG/DTG) thermal analysis data. The results show a dependence of the apparent kinetic parameters on the cross-linking degree, granulation, gel/macroporous matrix nature, exchange capacity and heating rate.

Several experiments have shown that inorganic salts may be decomposed to oxides by irradiating them with a continuous-wave CO2 laser. The process is characterized by an extremely high heating rate which develops within the impact region of the laser beam with the substance. For comparison, salts were also decomposed under controlled heating conditions. Knowledge of the intermediate steps stresses the importance of the positive and negative feedback mechanisms which control the laser-induced reactions. The present paper reviews results obtained by us for more complete descriptions of laser-induced reactions.

The paper presents a non-isothermal kinetic study of the decomposition of Zn acetate-based gel precursors for ZnO thin films, based on the thermogravimetric (TG) data. The evaluation of the dependence of the activation energy (E) on the mass loss (Δm) using the isoconversional methods (Friedman (FR), Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS)) has been presented in a previous paper. It was obtained that the sample dried at 125°C for 8 h exhibits the activation energy independent on the heating rate for the second decomposition step. In this paper the invariant kinetic parameter (IKP) method is used for evaluating the invariant activation parameters, which were used for numerically evaluation of the function of conversion. The value of the invariant activation energy is in a good agreement with those determined by isoconversional methods. In order to determine the kinetic model, IKP method was associated with the criterion of coincidence of the kinetic parameters for all heating rates. Finally, the following kinetic triplet was obtained: E=91.7 (±0.1) kJ mol−1, lnA(s−1)=16.174 (±0.020) and F1 kinetic model.

A series of new complexes with mixed ligands of the type M(4,4’-dipy)(C 3 H 3 O 2 ) 2 (H 2 O) y (( 1 ) M =Mn, y =2; ( 2 ) M =Ni, y =2; 4,4’-dipy: 4,4’-dipyridyl and C 3 H 3 O 2 is acrylate anion) and respectively M 2 (4,4’-dipy)(C 3 H 3 O 2 ) 4 (H 2 O) y (( 3 ) M =Cu, y =0; ( 4 ) M =Zn, y =1). The modification evidenced in IR spectra was correlated with the presence of acrylate ion as unidentate in the case of complex ( 1 ) and as bidentate for others complexes. The electronic reflectance spectra showed the d – d transition for complex ( 1 ) and ( 2 ) characteristic for the octahedral surrounding while the spectrum for complex ( 3 ) have the characteristic pattern for square-pyramidal stereochemistry. The thermal behaviour steps were investigated. The thermal transformations are complex processes according to TG and DTG curves including dehydration, acrylate ion oxidative degradation and thermolysis process of aromatic amine. The final products of decomposition are the most stable metal oxides.

The thermoreactivity of a zinc acetate non-alkoxide solution used for the preparation of ZnO-based thin films was investigated in the temperature range 20-600°C by TG-DTA, XRD and SEM data. We found that the formation in air of ZnO crystallites from the sol-gel precursor occurs above 150°C simultaneously with the decomposition of an intermediary compound, most probably carbonate hydroxide (sclarite and/or hydrozincite). At 200 °C, the crystalline structure is well defined in terms of ZnO hexagonal lattice parameters, although residual organic compounds and water were not yet fully removed and an amorphous phase coexists. A kinetic investigation on the thermal decomposition of sol-gel precursor from DTA data using Kissinger differential equation is also presented. Apparent activation energy values of about. 100 kJ mol-1 corresponding to the nonisothermal decomposition of solid precursors in the temperature range 170-250oC have been found.

Some contradictions concerning the classification of the methods to evaluate nonisothermal kinetic parameters into differential and integral ones are analyzed. Using the theorem of media for integrals, the equivalence between the methods that use the integration on low ranges of variables and the differential methods is shown. Concerning the magnitude of the range of change of variables on which the integration of the rate equation is performed, the applicability of the isoconversional methods that use approximate expressions of the temperature integral (Simpson's formula, formula based on the theorem of media for integrals) was analyzed. Our results were verified for simulated data (which are not affected by the experimental errors) as well as for the nonisothermal data for the thermal decomposition of ammonium perchlorate. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 339–344, 2006

Thermal analysis of 2-allyl-4-((4-(4-methylbenzyloxy)phenyl)diazenyl)phenol dye was performed in air flow. The compound thermal behavior was investigated using TG, DTG and DSC techniques, under non-isothermal linear regime. Kinetic parameters of the two decomposition steps were obtained by means of multi-heating rates methods. Isoconversioanl methods (KAS and FWO), Invariant Kinetic Parameters method and Perez-Maqueda et al. criterion (by means of CR and FW equations) were used.

The kinetics of crystallization of transparent and conductive high preferential c-axis oriented Al-doped ZnO thin films on Coming 1737 glass substrate from amorphous sol-gel precursor prepared using zinc acetate and aluminum chloride as cations source, 2-methoxiethanol as solvent and monoethanolamine as sol stabilizer has been investigated. The effect of preheating temperature on the values of the kinetic parameters and crystallization mechanism is discussed. Some data concerning the microstructure, the electrical and optical properties of the thin films are presented.

The paper contains an analysis of the used of Diefallah's composite integral method of kinetic parameters evaluation. It is shown that the application of this method should be preceded by the application of an isoconversional method through which the dependence of the activation energy, E, on the conversion degree,a, should be established. If Edepends ona, Diefallah's composite integral method leads to erroneous results. If Edoes not depend ona, the true kinetic model should be comprised in the pre-established set of kinetic models. These observations were checked for two sets of non-isothermal data, namely: (a) the TG curves corresponding to the dehydration of CaC2O4·H2O; (b) the TG curves corresponding to the thermal decomposition of polyvinyl chloride (PVC).

By surveying the most used methods for evaluating the kinetic parameters from non-isothermal measurements, we propose their classification scheme. As a result of the analysis we suggest a methodology to analyse the data from non-isothermal experiments and discuss several problems of non-isothermal kinetics, e.g., the validity of steady-state approximation under non-isothermal conditions and the problem of expressing the activation energy as a range of values.