The determination of activation energy from linear heating rate experiments: a comparison of the accuracy of isoconversion methods

Abstract

Model-free isoconversion methods are the most reliable methods for the calculation of activation energies of thermally activated reactions. A large number of these isoconversion methods have been proposed in the literature. A classification of these methods is proposed. Type A methods such as Friedman methods make no mathematical approximations, and Type B methods, such as the generalised Kissinger equation, apply a range of approximations for the temperature integral. The accuracy of these methods is investigated, by deriving expressions for the main sources of error which includes the inaccuracy in reaction rate measurement, approximations for the temperature integral and inaccuracies in determination of temperature for equivalent fraction transformed. Both highly inaccurate and highly accurate Type B methods are identified. In cases where some uncertainty over baselines of the thermal analysis data exists or where accuracy of determination of transformation rates is limited, type B methods will often be more accurate than type A methods.

A model for precipitation kinetics and strengthening in Al–Cu–Mg alloys

“…This activation energy should be equal to the activation energy for S phase formation, which can be derived from experiments which measure the rate of S formation at different temperatures. For the present analysis, the activation energy is obtained from DSC experiments performed on a 2024-T351 alloy at different heating rates using iso-conversion methods [57,58]. Fig.…”

“…versus T 1 [57] in Fig.5(b), where p T is the peak temperature and β is the heating rate. (In Fig.5(b) an additional data point for heating rate ~5 K/s (25°C/min) is also included).…”

Numerical simulation of a patent technology for sealing of deep-sea oil wells using nonlinear finite element method

“…Fan [4] used a new method for the derivation of activation energies is proposed by Starink [5]. It was shown [5] that this method is an order of magnitude more accurate than the Kissinger and Ozawa methods [6].…”

Activation energy determination for linear heating experiments: deviations due to neglecting the low temperature end of the temperature integral

“…It has been shown that for analysis of linear heating experiments (heating at constant rate), highly accurate and reliable activation energy analysis methods can be obtained by applying accurate approximations of the temperature integral [10]. This derivation can be formulated as follows.…”

“…Through applying a suitable approximation for the temperature integral on the right of the latter equation a range of well-known and lesser known isoconversion methods for activation energy analysis can be derived [10]. These methods include the Kissinger method [11], the Kissinger-Akahira-Sunose (KAS) method [12,13] (also termed the generalised Kissinger method), the Flynn-WallOzawa (FWO) method [14,15], a method described by Vyazovkin and co-workers [16,17] and 3 highly accurate methods developed by the present author [10,18,19].…”