Non-isothermal transformation kinetics: Application to metastable phases

Meisel, L. V.; Côté, Paul J.

doi:10.1016/0001-6160(83)90201-8

Cited by 73 publications

(26 citation statements)

References 21 publications

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“…(Note that this early method by Vyazovkin is different from a later model [27,28] derived by him. Note also that various authors [21,29] have in the past derived Eq. (10) using a specific reaction model, but, as shown above and elsewhere [4,10,15], this limiting assumption is not required.…”

Section: Type B: P(y)-isoconversion Methodsmentioning

confidence: 98%

“…This paper focuses on the accuracy of methods for obtaining the activation energy from experiments at constant heating rate, β. Over the past decades a bewildering range of such methods have been proposed (a selection of methods can be found in [6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21]). Some of these methods have been shown to be very inaccurate, which has fuelled doubts about the accuracy and validity of nonisothermal methods in general [22].…”

Section: Introductionmentioning

confidence: 99%

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

2003

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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.

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Section: Type B: P(y)-isoconversion Methodsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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

2003

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“…For this activation energy analysis, a large number methods have been proposed (a selection of methods can be found in Refs. 129,131,[133][134][135][136][137][138][139][140][141][142][143][144][145][146][147]. The aim of the present section is to describe the main features and accuracies of these methods, and provide recommendations about which methods are best suited for analysis of particular DSC data.…”

Section: Activation Energy Determinationmentioning

confidence: 99%

Analysis of aluminium based alloys by calorimetry: quantitative analysis of reactions and reaction kinetics

Starink¹

2004

International Materials Reviews

286

108

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Differential scanning calorimetry (DSC) and isothermal calorimetry have been applied extensively to the analysis of light metals, especially Al based alloys. Isothermal calorimetry and differential scanning calorimetry are used for analysis of solid state reactions, such as precipitation, homogenisation, devitrivication and recrystallisation; and solid-liquid reactions, such as incipient melting and solidification, are studied by differential scanning calorimetry. In producing repeatable calorimetry data on Al alloys, sample preparation, reproducibility and baseline drift need to be considered in detail. Calorimetry can be used effectively to study the different solid state reactions and solid-liquid reactions that occur during the main processing steps of Al based alloys (solidification, homogenisation, precipitation). Also, devitrivication of amorphous and ultrafine grained Al based powders and flakes can be studied effectively. Quantitative analysis of the kinetics of reactions is assessed through reviewing the interrelation between activation energy analysis methods, equivalent time approaches, impingement parameter approaches, mean field models for precipitation, the Johnson-Mehl-Avrami-Kolmogorov model, as well as novel models which have not yet found application in calorimetry. Differential scanning calorimetry has occasionally been used in attempts to measure the volume fractions of phases present in Al based alloys, and attempts at determining volume fractions of intermetallic phases in commercial alloys and amounts of devitrified phase in glasses are reviewed. The requirements for the validity of these quantitative applications are also reviewed.Keywords: Differential scanning calorimetry, Precipitation, Aluminium, Modelling, Transformation IMR/419 IntroductionCalorimetry is an analysis technique that is part of a group of techniques collectively known as thermal analysis methods. In its broadest sense, thermal analysis refers to the measurement of changes in properties of substances under a controlled temperature program. Thermal analysis techniques can be classified according to the type of temperature program that the sample is subjected to and the measured (output) signal. The most commonly used temperature programs are either isothermal hold or heating (scanning) at constant rate, while more recently, temperature modulated scanning and reaction controlled heating have also found application. The signals measured in thermal analysis can include heat flows, temperature changes, mass, evolved gasses, length changes, elastic modulus, and many other properties that characterise properties or reactions of interest. Calorimetry refers to thermal analysis methods that measure the heat evolution from a sample under a controlled temperature program. The two most often applied calorimetry techniques are isothermal calorimetry and differential scanning calorimetry (DSC), which, as the name suggests, is by definition non-isothermal (i.e. a temperature scan). Apart from the more common applications to polymers,...

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“…In comparison although the curves in FIG 6 (b) scale well with one another there is deviation from the expected straight line at ln(t/τ)~0.5, suggesting a breakdown in the JMAK theory at longer annealing times, a process similar to non-isothermal kinetics at higher temperatures 29 . A straight line yields an Avrami exponent of n = 2.02(6).…”

Section: Comentioning

confidence: 79%

Time-resolved synchrotron x-ray diffraction studies of the crystallization of amorphous Co(80−x)FexB20

Simmons

Greig

Lucas

et al. 2014

Journal of Applied Physics

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This paper addresses the time-dependent crystallization process occurring in 'bulk' amorphous Co 80-x respectively, suggesting one-dimensional growth, with a decreasing nucleation rate. Activation energy for α-(Co,Fe) was determined to be 2.7(1) eV and 2.4(3) eV in x = 20 and 40 respectively suggesting that those alloys with a lower Co content have a stronger resistance to crystallization. Based on these results, fabrication of CoFeB magnetic tunnel junctions via depositing amorphous layers and subsequently annealing to induce lattice matching presents itself as a viable and efficient method, for increasing the giant magnetoresistance in magnetic tunnel junctions.

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Non-isothermal transformation kinetics: Application to metastable phases

Cited by 73 publications

References 21 publications

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

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

Analysis of aluminium based alloys by calorimetry: quantitative analysis of reactions and reaction kinetics

Time-resolved synchrotron x-ray diffraction studies of the crystallization of amorphous Co(80−x)FexB20

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