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Abstract  

Data concerning the thermal behaviour of four heteropolynuclear compounds with the general formula [CuML(CH3COO)3] whereM=Ni(II), Zn(II), Mn(II) and Co(II); LH=2-amino-5-mercapto-1,2,3-thiadiazole were obtained. For the kinetically workable decomposition steps the values of the kinetic parameters were estimated.

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Abstract  

The adsorption of n -butane on extruded cylindrical activated carbon grains is studied providing two kinds of information: the influence of the temperature and the hydrocarbon partial pressure on the adsorption dynamics (kinetic study) and on the adsorption capacities (thermodynamic study). The thermodynamic aspect could be interpreted by a Langmuir model. From a kinetic point of view, we have experimentally proved that strong temperature variations occur inside the particles during the adsorption. In this paper, a kinetic model including both mass and heat transfer phenomena is proposed. Good agreement is found between the kinetic model predictions and the experimental mass and temperature variations inside the grain during the hydrocarbon adsorption.

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Abstract  

Thermal behavior of four food dyes, i.e. tartrazine, crysoine, azorubine and amarant was studied under non-isothermal conditions, in dynamic air atmosphere and at heating rates of 5, 10, 15 and 20C min–1. The TG data were correlated to the FTIR spectra of each sample, before and after the thermal decomposition. Kinetic study by processing the TG data was performed. The main conclusion of this study is that the non-parametric kinetic method allows a separation of the steps of a complex process and that the values of the activation energy obtained by this method agree satisfactory with that of Flynn–Wall–Ozawa estimation.

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Abstract  

The topic of the present work is to study the thermal behavior of phenitoine and pharmaceuticals by means of kinetic parameters determined in non-isothermal conditions. The TG/DTG data were obtained at four heating rates. These data were processed by the following methods: Friedman (FR), Budrugeac-Segal (BS) and the modified non-parametric kinetics (Sempere-Nomen). The main conclusions of the kinetic study are The FR method is versatile, but the values of the kinetic parameters are not certain, especially by multistep processes. The BS method offer a non-variant part of the activation energy, but the kinetic description is only formal. The NPK method is able to discriminate between two or more steps of a complex process. In our case, there are a preponderant process (more than 70% of the explained variance). By the NPK method there is a non-speculative separation of the temperature, respective conversion degree dependence of the reaction rate.

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Heteroleptic cadmium(II) complex, potential precursor for semiconducting CDS layers

Thermal stability and non-isothermal decomposition kinetics

Journal of Thermal Analysis and Calorimetry
Authors: Anna Kropidłowska, A. Rotaru, M. Strankowski, Barbara Becker, and E. Segal

Abstract  

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.

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Abstract  

The thermo-oxidative degradation of poly(vinyl alcohol) (PVA) has been investigated by TG+DTG+DTA simultaneous analysis performed in static air atmosphere, at four heating rates, namely 3, 5, 10 and 15 K min−1. TG, DTG and DTA curves showed that, in the temperature range 25–700°C, four successive processes occur. The first process consisting in the loss of physical adsorbed water is followed by three processes of thermal and/or thermo-oxidative degradations. The processing of the non-isothermal data corresponding to the second process (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 Friedman’s isoconversional method on the conversion degree shows that the investigated process is complex one. The mechanism of this process and the corresponding kinetic parameters were determined by Multivariate Non-linear Regression Program and checked for quasi-isothermal experimental data. It was pointed out that the first process of thermo-oxidation of PVA consists in three consecutive steps having Avrami-Erofeev kinetic model. The obtained results can be used for prediction of the thermal lifetime of PVA corresponding to a certain temperature of use and an endpoint criterion.

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Journal of Thermal Analysis and Calorimetry
Authors: C. Ribeiro, W. de Souza, Marisa Crespi, J. Gomes Neto, and F. Fertonani

Abstract  

Tungsten carbide, WC, has shown dissimilar thermal behavior when it is heated on changeable heating rate and flow of oxidant atmosphere. The oxidation of WC to WO3 tends to be in a single and slow kinetic step on slow heating rate and/or low flux of air. Kinetic parameters, on non-isothermal condition, could be evaluated to the oxidation of WC to heating rate below 15°C min−1 or low flow of air (10 mL min−1). The reaction is governed by nucleation and growth at 5 to 10°C min−1 then the tendency is to be autocatalytic, JMA and SB, respectively.

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Abstract

A nonlinear algorithm has been suggested to increase the accuracy of evaluating the activation energy by the integral isoconversional method. A minor modification of the algorithm has made it possible to adapt the isoconversional method for an arbitrary variation of the temperature. This advanced isoconversional method allows for trustworthy estimates of the activation energy when the thermal effect of a reaction makes the temperature of a sample deviate from a prescribed heating program.

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