The application of the formalism of dispersive kinetics for investigation of the isothermal decomposition of zinc leach residue in an inert atmosphere

Janković, Bojan; Stopić, Srečko; Güven, Aybars; Friedrich, Bernd

doi:10.1016/j.tca.2012.07.012

Cited by 4 publications

(2 citation statements)

References 49 publications

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“…The KJMA exponent, n , is defined to contain contributions from the growth dimensionality, λ, and the nucleation type, β, with limiting cases of 0 for instantaneous nucleation (pre-existing nuclei) and 1 for continuous nucleation. − ,, Thus, n = λ + β where 0 ≤ β ≤ 1 and λ = 1, 2, or 3 for 1-, 2-, or 3-D growth, respectively. Given such a specific definition for the KJMA exponent, numerous publications detail reaction mechanisms for crystallization transformations based solely on the KJMA exponent, although many reports caution that kinetic exponents may not reflect the reaction mechanism. ,,,− Numerous experimental manuscripts demonstrate variation of the KJMA exponent with isothermal crystallization temperature, , time, ,,− heating/cooling rate, , and preannealing temperature. − These often are used as evidence that the crystallization mechanism changes over the course of a reaction. While change of mechanism during crystallization is unlikely for congruently melting systems, ,,, such may be possible for noncongruently melting systems where the composition at the crystallization front changes with time. , Consensus has not been reached as to the physical significance of or the consistent conditions under which the KJMA exponent can be correctly interpreted.…”

Section: Introductionmentioning

confidence: 99%

Crystal Growth Simulations To Establish Physically Relevant Kinetic Parameters from the Empirical Kolmogorov–Johnson–Mehl–Avrami Model

2013

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A series of simulations was performed to enable interpretation of the material and physical significance of the parameters defined in the Kolmogorov, Johnson and Mehl, and Avrami (KJMA) rate expression commonly used to describe phase boundary controlled reactions of condensed matter. The parameters k, n, and t 0 are shown to be highly correlated, which if unaccounted for seriously challenge mechanistic interpretation. It is demonstrated that rate measurements exhibit an intrinsic uncertainty without precise knowledge of the location and orientation of nucleation with respect to the free volume into which it grows. More significantly, it is demonstrated that the KJMA rate constant k is highly dependent on sample size. However, under the simulated conditions of slow nucleation relative to crystal growth, sample volume and sample anisotropy correction affords a means to eliminate the experimental condition dependence of the KJMA rate constant, k, producing the material-specific parameter, the velocity of the phase boundary, v pb .

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Section: Introductionmentioning

confidence: 99%

Crystal Growth Simulations To Establish Physically Relevant Kinetic Parameters from the Empirical Kolmogorov–Johnson–Mehl–Avrami Model

2013

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“…The KJMA model is commonly expressed as α ( t ) = 1 − exp { − false[ k ( t − t 0 ) false] n } with rate constant k , nucleation time t 0 , and dimensionality n . These kinetic parameters, particularly the dimensionality, are often used to infer mechanistic detail − in spite of the growing body of literature demonstrating that they are empirical, ,− significantly affected by experimental factors, − and do not necessarily reflect the true reaction mechanism. − …”

Section: Introductionmentioning

confidence: 99%

Experimental Determination of the Crystallization Phase-Boundary Velocity in the Halozeotype CZX-1

et al. 2013

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Isothermal crystallization experiments were performed on the halozeotype CZX-1 with 2D temperatureand time-resolved synchrotron X-ray diffraction (TtXRD) and differential scanning calorimetry (DSC). These crystallization experiments demonstrate that the fundamental materials property, the velocity of the phase boundary of the crystallization front, v pb , can be recovered from the Kolmogorov Johnson and Mehl and Avrami (KJMA) model of phase-boundary controlled reactions by introducing the sample volume into the KJMA rate expression. An additional corrective term is required if the sample volume of the crystallization measurement is anisotropic. The concurrent disappearance of the melt and appearance of the crystalline phase demonstrate that no intermediates exist in the crystallization pathway. The velocity of the phase boundary approaches 0 as the glass transition (T g ≈ 30°C) is approached and at about 10°below melting point (T m = 173°C). The velocity of the phase boundary reaches a maximum of 30 μm s −1 at 135°C. Single or near-single crystals are grown under conditions where the v pb is much greater than the rate of nucleation.

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The geometry of closed sets in the state of chemical transformation

Klyucharev

Klyuchareva

2015

J Therm Anal Calorim

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The application of the formalism of dispersive kinetics for investigation of the isothermal decomposition of zinc leach residue in an inert atmosphere

Cited by 4 publications

References 49 publications

Crystal Growth Simulations To Establish Physically Relevant Kinetic Parameters from the Empirical Kolmogorov–Johnson–Mehl–Avrami Model

Crystal Growth Simulations To Establish Physically Relevant Kinetic Parameters from the Empirical Kolmogorov–Johnson–Mehl–Avrami Model

Experimental Determination of the Crystallization Phase-Boundary Velocity in the Halozeotype CZX-1

The geometry of closed sets in the state of chemical transformation

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