Generalised kinetics of overall phase transition useful for glass crystallisation when assuming non-isothermal conditions

The modelling of reaction kinetics is a fashionable subject of publications. We developed an analogue of the KJMA equation under non-isothermal conditions α(T)=1−exp(−(T/θ)N) that describes the dependence of degree of transformation α(T) at a constant rate, q, of heating with characteristic temperature θ(q) and power N, proportional to the Avrami parameter, n. This equation is valid even when the activation energy of the process is not constant. We demonstrate that reliable information about the activation energy is obtained when the experimental data are plotted in coordinates: logq (heating rate) against logTp (peak temperature).

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Research on Pyrolysis Kinetics of Shenhua Coal and Direct Liquefaction Residue

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.550-553.2758 ◽

2012 ◽

Vol 550-553 ◽

pp. 2758-2762 ◽

Cited By ~ 2

Author(s):

Xi Jie Chu ◽

Yong Gang Wang ◽

Li Hong Zhao

Keyword(s):

Experimental Data ◽

Activation Energy ◽

Kinetic Parameters ◽

Heating Rate ◽

Coal Pyrolysis ◽

Pyrolysis Kinetics ◽

Differential Heating ◽

Pyrolysis Behavior ◽

Direct Liquefaction ◽

Kinetics Of

The pyrolysis tests of Shenhua coal and Shenhua direct liquefaction residue have been carried out using thermogravimetric at the differential heating rate. The kinetic parameters k and E were calculated using DAEM method. Results show DAME model can describe the pyrolysis behavior of Shenhua coal within the range of 20% to 95%, the activation energy of coal pyrolysis ranges from 53.98 to 279.38 kJ/mol, and DAME model can describe the behavior of Shenhua direct liquefaction residue within the range of 10% to 80%, the activation energy of residue pyrolysis is about 170 kJ/mol. The results of which are basically consistent with the experimental data.

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Effect of ionizing radiation on the kinetics of hydrogenation on the Ni-MgO mixed catalyst

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19821780 ◽

1982 ◽

Vol 47 (7) ◽

pp. 1780-1786 ◽

Cited By ~ 2

Author(s):

Rostislav Kudláček ◽

Jan Lokoč

Keyword(s):

Experimental Data ◽

Activation Energy ◽

Liquid Phase ◽

Ionizing Radiation ◽

Oxide Catalyst ◽

Absorbed Dose ◽

Hydrogenation Rate ◽

Solution Composition ◽

Mixed Catalyst ◽

Kinetics Of

The effect of gamma pre-irradiation of the mixed nickel-magnesium oxide catalyst on the kinetics of hydrogenation of maleic acid in the liquid phase has been studied. The changes of the hydrogenation rate are compared with the changes of the adsorbed amount of the acid and with the changes of the solution composition, activation energy, and absorbed dose of the ionizing radiation. From this comparison and from the interpretation of the experimental data it can be deduced that two types of centers can be distinguished on the surface of the catalyst under study, namely the sorption centres for the acid and hydrogen and the reaction centres.

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Drying Kinetics of Noni Seeds

Journal of Agricultural Science ◽

10.5539/jas.v11n5p250 ◽

2019 ◽

Vol 11 (5) ◽

pp. 250 ◽

Cited By ~ 2

Author(s):

Wellytton Darci Quequeto ◽

Osvaldo Resende ◽

Patrícia Cardoso Silva ◽

Fábio Adriano Santos e Silva ◽

Lígia Campos de Moura Silva

Keyword(s):

Experimental Data ◽

Activation Energy ◽

Diffusion Coefficient ◽

Moisture Content ◽

Mathematical Models ◽

Effective Diffusion Coefficient ◽

Effective Diffusion ◽

Information Criterion ◽

Drying Kinetics ◽

Kinetics Of

Noni seeds have been used for years as an important medicinal source, with wide use in the pharmaceutical and food industry. Drying is a fundamental process in the post-harvest stages, where it enables the safe storage of the product. Therefore, the present study aimed to fit different mathematical models to experimental data of drying kinetics of noni seeds, determine the effective diffusion coefficient and obtain the activation energy for the process during drying under different conditions of air temperature. The experiment used noni seeds with initial moisture content of 0.46 (decimal, d.b.) and dehydrated up to equilibrium moisture content. Drying was conducted under different controlled conditions of temperature, 40; 50; 60; 70 and 80 ºC and relative humidity, 24.4; 16.0; 9.9; 5.7 and 3.3%, respectively. Eleven mathematical models were fitted to the experimental data. The parameters to evaluate the fitting of the mathematical models were mean relative error (P), mean estimated error (SE), coefficient of determination (R2), Chi-square test (c2), Akaike Information Criterion (AIC) and Schwarz’s Bayesian Information Criterion (BIC). Considering the fitting criteria, the model Two Terms was selected to describe the drying kinetics of noni seeds. Effective diffusion coefficient ranged from 8.70 to 23.71 × 10-10 m2 s-1 and its relationship with drying temperature can be described by the Arrhenius equation. The activation energy for noni seeds drying was 24.20 kJ mol-1 for the studied temperature range.

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Mathematical models to describe the drying process of Moringa oleifera leaves in a convective-air dryer

Czech Journal of Food Sciences ◽

10.17221/257/2020-cjfs ◽

2021 ◽

Author(s):

Kivaandra Dayaa Rao Ramarao ◽

Zuliana Razali ◽

Chandran Somasundram

Keyword(s):

Activation Energy ◽

Mathematical Models ◽

Moringa Oleifera ◽

Effective Diffusivity ◽

Drying Process ◽

Constant Rate ◽

Rate Period ◽

Moringa Oleifera Leaves ◽

Air Dryer ◽

Kinetics Of

Drying kinetics of Malaysian Moringa oleifera leaves was investigated using a convective-air dryer. The drying parameters were: temperature (40, 50, 60, 70 °C), air velocity (1.3 m s–1, 1.7 m s–1). The drying process took place in the falling rate period and there was an absence of a constant rate period in this experiment. Six mathematical models (Lewis, Henderson and Pabis, Wang and Singh, Peleg, Page, and logarithmic) were selected for the description of drying characteristics of the leaves. The Wang and Singh model was determined as the best model based on the highest overall coefficient determinant (R2) and the lowest overall root mean square error (RMSE). The effective diffusivity (Deff ) was also calculated which was in the range of 3.98 × 10–11 m2 s–1 to 1.74 × 10–10 m2 s–1. An Arrhenius relation was constructed to determine the activation energy for the samples in the convective air dryer. The activation energy for M. oleifera leaves was 39.82 kJ mol–1 and 33.13 kJ mol–1 at drying velocities of 1.3 m s–1 and 1.7 m s–1, respectively.

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Study of Donor Centres in n-InSb due to the Temperature Annealing

Materials Science Forum ◽

10.4028/www.scientific.net/msf.480-481.197 ◽

2005 ◽

Vol 480-481 ◽

pp. 197-200

Author(s):

Y. Sayad ◽

A. Nouiri

Keyword(s):

Experimental Data ◽

Activation Energy ◽

Annealing Time ◽

Annealing Temperature ◽

Theoretical Study ◽

Donor Concentration ◽

Model Based ◽

Proposed Model ◽

Kinetics Of ◽

Best Fit

An increasing of donor centres has been detected in n-InSb when it was submitted to anneal/quench with various annealing temperature (450 °C - 850 °C) and various annealing time (5 - 100 hours). A theoretical study of the kinetics of the conduction conversion of n-InSb at temperature annealing above 250 °C has been made. The present analysis indicates that the donor concentration increases with increasing of annealing time. In order to study this variation and to give a model for donor centres generated, a proposed model based on the simple kinetic is used to fit the variation of donor concentration as a function of annealing time. However, from the best fit of experimental data using the proposed model, the activation energy is determined.

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Drying kinetics of baru flours as function of temperature

Revista Brasileira de Engenharia Agrícola e Ambiental ◽

10.1590/1807-1929/agriambi.v22n10p713-719 ◽

2018 ◽

Vol 22 (10) ◽

pp. 713-719 ◽

Cited By ~ 2

Author(s):

Douglas R. Reis ◽

Fabrício B. Brum ◽

Eduardo J. O. Soares ◽

Jessiana R. Magalhães ◽

Fabrício S. Silva ◽

...

Keyword(s):

Experimental Data ◽

Activation Energy ◽

Food Industry ◽

Nutritional Value ◽

Effective Diffusivity ◽

Drying Kinetics ◽

Statistical Parameters ◽

Noticeable Effect ◽

Different Temperatures ◽

Kinetics Of

ABSTRACT Several types of seeds have been initially used in the food industry due to the great potential that vegetable proteins have. Baru is a fruit commonly found in the Cerrado biome, having a high nutritional value. This paper aimed to determine and analyze the drying kinetics of whole and defatted baru almond flours at different temperatures. The flour resulting from almond milling was defatted using petroleum ether. The drying processes were performed at temperatures of 40, 50 and 60 ºC. The mathematical models of Page, Henderson and Pabis, Midilli & Kucuk, Thompson and Approximation of Diffusion were fitted to the experimental data. The results showed a noticeable effect of air temperature on the drying kinetics of whole and defatted baru almond flours. According to the statistical parameters of analysis, the models Midilli & Kucuk and Page were the ones with the best fits to the experimental data. The effective diffusivity values found ranged from 8.02 × 10–10 to 19.90 × 10–10 m2 s-1 and for the activation energy were 22.39 and 39.37 KJ mol-1 for whole and defatted almonds, respectively.

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Phase Transformation Kinetics of a FCC Al0.25CoCrFeNi High-Entropy Alloy during Isochronal Heating

Metals ◽

10.3390/met8121015 ◽

2018 ◽

Vol 8 (12) ◽

pp. 1015

Author(s):

Jun Wang ◽

Chen Wei ◽

Haoxue Yang ◽

Tong Guo ◽

Tingting Xu ◽

...

Keyword(s):

Phase Transition ◽

Activation Energy ◽

Phase Transformation ◽

High Entropy Alloy ◽

Transformation Kinetics ◽

High Entropy ◽

Phase Transformation Kinetics ◽

Diffusion Controlled ◽

Thermal Dilation ◽

Kinetics Of

The phase transformation kinetics of a face-centered-cubic (FCC) Al0.25CoCrFeNi high-entropy alloy during isochronal heating is investigated by thermal dilation experiment. The phase transformed volume fraction is determined from the thermal expansion curve, and results show that the phase transition is controlled by diffusion controlled nucleation-growth mechanism. The kinetic parameters, activation energy and kinetic exponent are determined based on Kissinger–Akahira–Sunose (KAS) and Johnson–Mehl–Avrami (JMA) method, respectively. The activation energy and kinetic exponent determined are almost constant, indicating a stable and slow speed of phase transition in the FCC Al0.25CoCrFeNi high-entropy alloy. During the main transformation process, the kinetic exponent shows that the phase transition is diffusion controlled process without nucleation during the transformation.

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Kinetics of crystallization in amorphous Se73.2Te21.1Sb5.7 under isochronal conditions: Effect of heating rate on the activation energy

Physica B Condensed Matter ◽

10.1016/j.physb.2006.08.014 ◽

2007 ◽

Vol 390 (1-2) ◽

pp. 196-202 ◽

Cited By ~ 33

Author(s):

A.A. Abu-Sehly ◽

A.A. Elabbar

Keyword(s):

Activation Energy ◽

Heating Rate ◽

Kinetics Of Crystallization ◽

Kinetics Of

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Generalized Activation Energy Spectrum Theory: A New Approach for modeling Structural Relaxation in Amorphous Solids

MRS Proceedings ◽

10.1557/proc-321-167 ◽

1993 ◽

Vol 321 ◽

Author(s):

Jung H. Shin ◽

Harry A. Atwater

Keyword(s):

Experimental Data ◽

Activation Energy ◽

Structural Relaxation ◽

Ad Hoc ◽

Amorphous Solids ◽

Nucleation Kinetics ◽

Crystal Silicon ◽

Time Resolved ◽

New Approach ◽

Kinetics Of

ABSTRACTA general approach to the dynamics of structural relaxation in amorphous solids is developed. A form of the recombination kinetics of defects is chosen which removes the ad hoc assumption made in previous theories that defects recombine only with others of identical activation energy. The generalized theory is tested quantitatively by modelling the structural relaxation of amorphous silicon, and comparing the results with the experimental data on structural relaxation. It is found that the generalized theory is necessary in order to accurately describe the time-resolved relaxation data. The generalized theory is also applied to estimate the effect of irradiation on the nucleation kinetics of crystal silicon, and is found to agree well with experimental data.

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