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Abstract  

Two glasses, the first one with the composition of Li2O·2SiO2 and the second one with the addition of CaO, P2O5 and CaF2 in the stoichiometric ratio corresponding to fluoroapatite were prepared and their tendency to crystallize has been studied by non-isothermal DTA analysis. The values of kinetic parameters calculated using the isoconversional integral method have been used to determine the temperature dependencies of both the length of isothermal induction period and the length of overall isothermal crystallization for both glasses. The estimated dependencies indicate that the glass containing CaO, P2O5 and CaF2 has a lower thermal stability.

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Isoconversional analysis of solid state transformations

A critical review. Part II. Complex transformations

Journal of Thermal Analysis and Calorimetry
Authors: J. Farjas and P. Roura

Introduction The second part of this review is devoted to the analysis of complex transformations. In particular, we will describe the use of the isoconversional methods introduced in the first part of this review (Part I [ 1

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Isoconversional analysis of solid-state transformations

A critical review. Part III. Isothermal and non isothermal predictions

Journal of Thermal Analysis and Calorimetry
Authors: J. Farjas and P. Roura

Introduction Kinetic methods are routinely employed to determine the kinetic parameters of solid-state transformations from thermal analysis experiments. In particular, there are isoconversional methods which are model-free, i

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Thermal decomposition kinetics of some aromatic azomonoethers

Part II. Non-isothermal study of three liquid crystals in dynamic air atmosphere

Journal of Thermal Analysis and Calorimetry
Authors: A. Rotaru, Anna Kropidłowska, Anca Moanţă, P. Rotaru, and E. Segal

Abstract  

Thermal analysis of three azomonoether dyes, exhibiting liquid-crystalline properties, was performed in dynamic air atmosphere. Thermal stability studies and the evaluation of the kinetic parameters of each physical or chemical transformations are essential for a full characterization, before attempting accurate thin films’ depositions of such materials used in non-linear optical applications. New synthesized dyes with general formula:

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where R is a nematogenic group: CN, CF3 or a highly polarizable group: NO2 were investigated using TG, DTG, DTA and DSC techniques, under non-isothermal regime. The evolved gases were analyzed by FTIR spectroscopy. The activation energies of the first decomposition step were evaluated for each compound, the obtained results revealing complex mechanisms.

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Kinetics of thermal degradation of polymers

Complementary use of isoconversional and model-fitting methods

Journal of Thermal Analysis and Calorimetry
Author: K. Chrissafis

Abstract  

The thermal degradation of polymers has been studied quite extensively using thermogravimetric measurements. For the kinetic description, most of the times single rate heating data and model-fitting methods have been used. Since the thermal degradation of the polymers is a very complex reaction, the choice of a reliable model or a combination of kinetic models is very important. The advantages or the disadvantages of using a single heating rate or multiple heating rates data for the determination of the kinetic triplet have been investigated. Also, the activation energy has been calculated with the isoconversional and model-fitting methods. The reaction model was determined with the model-fitting method. The limits of all these procedures were investigated with experimental data of the thermal degradation of the poly(ethylene adipate) (PEAd).

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the extent of conversion, was evaluated by the Kissinger–Akahira–Sunose (KAS), Ozawa–Flynn–Wall (OFW), Starink, Tang, and Vyazovkin isoconversional methods. The Avrami exponent “ n ” of the crystallization process was also evaluated using the Ozawa

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Journal of Thermal Analysis and Calorimetry
Authors: Gurdip Singh, A. K. Shrimal, Inder Pal Singh Kapoor, Chandra Prakash Singh, Dinesh Kumar, and Manan S. Mudi

Kinetics of thermolysis is evaluated from isothermal TG data using model-fitting as well as model-free isoconversional method [ 25 ]. The following equation was found to be hold under isothermal condition: where, α is the extent of conversion, E is

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fraction, α, that depends on the reaction model, Q α is the activation energy. There are many methods for determining the activation energy from experiments under non-isothermal condition and a linear heating rate. Isoconversional methods, which permit

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with acrylic–divinylbenzene matrix, evaluated the kinetic parameters by means of isoconversional methods, and observed that the apparent kinetic parameters are dependent on the cross-linking degree, granulation, exchange capacity, and heating rate

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