A Method for Determining Crystallization Kinetic Parameters from one Nonisothermal Calorimetric Experiment

2000 ◽  
Vol 15 (4) ◽  
pp. 1000-1007 ◽  
Author(s):  
Haoyue Zhang ◽  
Brian S. Mitchell
Keyword(s):  
Kinetic Equation ◽  
Kinetic Parameters ◽  
Crystallization Kinetic ◽  
Frequency Factor ◽  
Nucleation Site ◽  
Avrami Equation ◽  
Transformation Rate ◽  
Isothermal Process ◽  
Electronic Microscopy ◽  
New Equation

A new equation was developed for evaluating kinetic parameters in the isokinetic range of a phase transformation using nonisothermal calorimetric techniques. The Johnson–Mehl–Avrami equation was extended by considering that the transformation rate in an isothermal process can be translated into the nonisothermal transformation in an isokinetic range. The Avrami exponent, n, activation energy, E, and frequency factor, K0, were calculated from only one nonisothermal experiment by using the new kinetic equation for amorphous Se (a-Se), polysilane/polycarbosilane (PS/PCS), and lithium disilicate (LiO2 · 2SiO2 or LS2) samples with nucleation site saturation. The values of E and K0 calculated using the new kinetic equation agree well with those obtained by the Kissinger equation for the prenucleated a-Se, PS/PCS, and LS2 samples. The values of n indicate that volume crystallization is dominant in the bulk a-Se and LS2 samples, whereas surface crystallization is dominant in the powdered PS/PCS sample. These results for a-Se were confirmed by scanning and transmission electronic microscopy.

Study on Non-Isothermal Crystallization Kinetic of Tundish Covering Fluxes

2011 ◽  
Vol 266 ◽  
pp. 102-105
Author(s):  
Li Feng Sun ◽  
Hong Po Wang ◽  
Chun Lai Liu ◽  
Yong Zou ◽  
Mao Fa Jiang
Keyword(s):  
Isothermal Crystallization ◽  
Heat Insulation ◽  
Crystallization Kinetic ◽  
Avrami Equation ◽  
Crystallization Time ◽  
Resistance Furnace ◽  
Crystallization Behaviors ◽  
Good Heat ◽  
Casting Production ◽  
Electrical Resistance Furnace

Basic tundish covering flux is widely used in continuous casting production of high quality steel because of good heat insulation function and the properties of absorbing inclusions. However, there is a serious problem of incrustation caused by basic tundish covering flux in process of pouring and it could be dramatically influenced by the crystallization behaviors of covering flux. In the paper, the crystallization time and ratio of basic tundish covering fluxes were investigated by high temperature electrical resistance furnace and single hot thermocouple apparatus. Based on the crystallization kinetic knowledge and experimental results, Avrami equation was modified, the non-isothermal crystallization equation that could quantitatively describe the crystallization behaviors of basic tundish covering fluxes was established.

scholarly journals Pyrolysis Kinetic Parameters of Omari Oil Shale Using Thermogravimetric Analysis

Energies ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 4060
Author(s):  
Ziad Abu El-Rub ◽  
Joanna Kujawa ◽  
Samer Al-Gharabli
Keyword(s):  
Activation Energy ◽  
Thermogravimetric Analysis ◽  
Kinetic Parameters ◽  
Oil Shale ◽  
Arrhenius Plot ◽  
Frequency Factor ◽  
Coefficient Of Determination ◽  
Assay Method ◽  
Temperature Integral ◽  
Integral Approximation

Oil shale is one of the alternative energies and fuel solutions in Jordan because of the scarcity of conventional sources, such as petroleum, coal, and gas. Oil from oil shale reservoirs can be produced commercially by pyrolysis technology. To optimize the process, mechanisms and rates of reactions need to be investigated. Omari oil shale formation in Jordan was selected as a case study, for which no kinetic models are available in the literature. Oil shale was analyzed using the Fischer assay method, proximate analysis (moisture, volatile, and ash), gross calorific value, elemental analysis (CHNS), and X-ray fluorescence (XRF) measurements. Non-isothermal thermogravimetric analysis was applied to study the kinetic parameters (activation energy and frequency factor) at four selected heating rates (5, 10, 15, and 20 °C/min). When oil shale was heated from room temperature to 1100 °C, the weight loss profile exhibited three different zones: drying (devolatilization), pyrolysis, and mineral decomposition. For each zone, the kinetic parameters were calculated using three selected methods: integral, temperature integral approximation, and direct Arrhenius plot. Furthermore, the activation energy in the pyrolysis zone was 112–116 kJ/mol, while the frequency factor was 2.0 × 107 − 1.5 × 109 min−1. Moreover, the heating rate has a directly proportional relationship with the rate constant at each zone. The three different methods gave comparable results for the kinetic parameters with a higher coefficient of determination (R2) for the integral and temperature integral approximation compared with the direct Arrhenius plot. The determined kinetic parameters for Omari formation can be employed in developing pyrolysis reactor models.

An alternative Avrami equation to evaluate kinetic parameters of the interaction of Hg(II) with thin chitosan membranes

2003 ◽  
Vol 263 (2) ◽  
pp. 542-547 ◽  
Author(s):  
Elaine C.N. Lopes ◽  
Fernanda S.C. dos Anjos ◽  
Eunice F.S. Vieira ◽  
Antonio R. Cestari
Keyword(s):  
Kinetic Parameters ◽  
Avrami Equation ◽  
Chitosan Membranes

scholarly journals Determination of Crystal Growth Geometry Factors and Nucleation Site Densities of Electrodeposited Ferromagnetic Cobalt Nanowire Arrays

Crystals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 142 ◽  
Author(s):  
Ryusei Saeki ◽  
Takeshi Ohgai
Keyword(s):  
Crystal Growth ◽  
Electrochemical Reduction ◽  
Spontaneous Magnetization ◽  
Frequency Factor ◽  
Nucleation Site ◽  
Nanowire Arrays ◽  
Crystal Nucleation ◽  
Anodized Aluminum ◽  
Cobalt Electrodeposition ◽  
Ferromagnetic Cobalt

The time-dependence of electrochemical reduction current, which was observed during the one-dimensional (1-D) crystal growth of ferromagnetic cobalt nanowire arrays, was analyzed by Johnson–Mehl–Avrami–Kolmogorov (JMAK) theory. Textured hcp-Co nanowire arrays were synthesized by potentio-static electrochemical reduction of Co2+ ions in anodized aluminum oxide (AAO) nanochannel films. Crystal growth geometry factor n in the JMAK equation was determined to be ca. 1. Hence, the electrochemical crystal growth process of a numerical nanowires array can be explained by 1-D geometry. The crystal nucleation frequency factor, k in JMAK equation was estimated to be the range between 10−4 and 10−3. Our experimental results revealed that the crystal nucleation site density Nd increased up to 2.7 × 10−8 nm−3 when increasing the overpotential for cobalt electrodeposition by shifting the cathode potential down to −0.85 V vs. Ag/AgCl. The (002) crystal orientation of hcp-Co nanowire arrays was, remarkably, observed by decreasing Nd. Spontaneous magnetization behavior was observed in the axial direction of nanowires. By decreasing the overpotential for cobalt electrodeposition, the coercivity of the nanocomposite film increased and reached up to 1.88 kOe, with a squareness of ca. 0.9 at room temperature.

Study on Combustion Characteristics of Impurity Coal Based on TG-DTG-DTA

2012 ◽  
Vol 568 ◽  
pp. 360-363
Author(s):  
Zhan Wen He ◽  
Chuan Cheng Zhang
Keyword(s):  
Kinetic Equation ◽  
Kinetic Parameters ◽  
Heating Rate ◽  
Ignition Temperature ◽  
Combustion Process ◽  
Combustion Characteristics ◽  
Diffusion Kinetic

Abstract.Based on TG-DTG-DTA, combustion characteristics and kinetic parameters of impure coal in the 10 °C / min heating rate were studied. The results showed that with the increase in the proportion of impurities, ignition temperature, burned temperature significantly improved; combustion characteristics of index clearly decreased; combustion process can be described by a diffusion kinetic equation

Theory of nucleation in solid state reactions

1968 ◽  
Vol 46 (2) ◽  
pp. 111-116 ◽  
Author(s):  
A. R. Allnatt ◽  
P. W. M. Jacobs
Keyword(s):  
Solid State ◽  
Approximate Model ◽  
Single Step ◽  
Solid State Reactions ◽  
Avrami Equation ◽  
Nucleation Process ◽  
Special Cases ◽  
New Equation ◽  
Kinetics Of ◽  
Short Times

The theory of nucleation in solid state reactions is formulated in a general way and a solution to the problem of multi-step nucleation obtained. Two special cases of the general formulation are considered: the second of these corresponds to Bagdassarian's approximate model and some corrections to his treatment are pointed out. A new equation describing the kinetics of a solid state reaction, which involves multi-step nucleation followed by a constant and isotropic rate of growth, is derived. This equation is termed the generalized Avrami equation since it removes the restriction, in Avrami's treatment, of a single-step nucleation process. Erofeev's analysis of the problem is shown to be valid only in the limit of short times: the generalized Avrami equation reduces to Erofeev's equation in this limit.

Curing Reaction and Kinetic Parameters of Diallyl Orthophthalate Resin with Initiator Dicumyl Peroxide

2010 ◽  
Vol 160-162 ◽  
pp. 1366-1371
Author(s):  
Xiao Qin Yue ◽  
Qi Lin Mei ◽  
Zhi Xiong Huang ◽  
Peng Wen ◽  
Ling Huang
Keyword(s):  
Kinetic Parameters ◽  
Frequency Factor ◽  
Treatment Temperature ◽  
Curing Temperature ◽  
Dicumyl Peroxide ◽  
Scanning Calorimetry ◽  
Thermal Treatment Temperature ◽  
Reaction Heat ◽  
Curing Reaction ◽  
Gel Temperature

The curing reaction of diallyl orthophthalate(DAOP) resin, which was initiated by dicumyl peroxide(DCP), was studied by Fourier transform infrared spectroscopy(FTIR). Differential scanning calorimetry(DSC) was used to determine the curing behavior and kinetic parameters of dicumyl peroxide (DCP) / diallyl orthophthalate (DAOP) system. The results clarified that the curing reaction of DAOP resin could be initiated by DCP at 150-180°C and the reaction heat diffused slowly in curing process. The gel-temperature, curing temperature and thermal treatment temperature of the DCP(3%)/DAOP system were 145.46°C, 166.03°C and 173.83°C. The apparent activation energy, frequency factor and reaction order were 130.200kJ/mol, 5.231×1010 and 0.9455, respectively.

scholarly journals Effect of Substitutions on Thermal Behavior of Symmetric Doubleschiff Bases of 1,1’-Bis(4-Amino Phenyl)Cyclohexane

2016 ◽  
Vol 63 ◽  
pp. 145-149
Author(s):  
Bhavesh J. Gangani ◽  
Parsotam H. Parsania
Keyword(s):  
Thermal Properties ◽  
Thermal Behavior ◽  
Kinetic Parameters ◽  
Schiff Bases ◽  
Frequency Factor ◽  
Entropy Change ◽  
Nitrogen Atmosphere ◽  
Energy Of Activation ◽  
Thermo Gravimetric ◽  
Degradation Kinetic

Thermo gravimetric analyses of some symmetric double Schiff bases of 1, 1’- bis (4-amino phenyl) cyclohexane (SDSB-1 to SDSB-6) was carried out at 100C/min in nitrogen atmosphere. Schiff bases are thermally stable up to 200-285°C and followed two step degradation kinetic. Various kinetic parameters such as order of degradation (n), energy of activation (Ea), frequency factor (A) and entropy change (ΔS) were derived accordingly Anderson-Freeman method interpreted in light of nature of the substituents. The nature, size and position of substituents affected thermal properties of the Schiff bases.

Mathematical research of the phase transformation kinetics of alloyed steel

2019 ◽  
Vol 85 (12) ◽  
pp. 25-32
Author(s):  
A. S. Kurkin
Keyword(s):  
Experimental Data ◽  
Martensitic Transformation ◽  
Phase Transformations ◽  
Diffusion Processes ◽  
Kinetic Equations ◽  
Transformation Process ◽  
Avrami Equation ◽  
Published Data ◽  
Transformation Rate ◽  
Kinetics Of

Regulation of the process parameters allows obtaining the desired properties of the metal. Computer simulation of technological processes with allowance for structural and phase transformations of the metal forms the basis for the proper choice of those parameters. Methods of mathematical modeling are used to study the main diffusion and diffusion-free processes of transformations in alloyed steels during heating and cooling. A comparative analysis of the kinetic equations of phase transformations including the Kolmogorov – Avrami and Austin – Rickett equations which describe in different ways the time dependence of the diffusion transformation rate and attained degree of transformation has been carried out. It is shown that the Austin – Rickett equation is equivalent to the Kolmogorov – Avrami equation with a smooth decrease of the Avrami exponent during the transformation process. The advantages of the Kolmogorov – Avrami equation in modeling the kinetics of ferrite-pearlite and bainite transformations and validity of this equation for modeling the kinetics of martensite transformations during tempering are shown. The parameters for describing the tempering process of steel 35 at different temperatures are determined. The proposed model is compared with equations based on the Hollomon – Jaffe parameter. The diagrams of martensitic transformation of alloyed steels and disadvantages of the Koistinen – Marburger equation used to describe them are analyzed. The equations of the temperature dependence of the transformation degree, similar to the Kolmogorov – Avrami and Austin – Rickett equations, are derived. The equations contain the minimum set of the parameters that can be found from published data. An iterative algorithm for determining parameters of the equations is developed, providing the minimum standard deviation of the constructed dependence from the initial experimental data. The dependence of the accuracy of approximation on the temperature of the onset of transformation is presented. The complex character of the martensitic transformation development for some steels is revealed. The advantage of using equations of the Austin – Rickett type when constructing models from a limited amount of experimental data is shown. The results obtained make it possible to extend the approaches used in modeling diffusion processes of austenite decomposition to description of the processes of formation and decomposition of martensite in alloyed steels.

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