Transient and Athermal Nucleation of Solids in Rapidly Quenched Liquid Si

1995 ◽  
Vol 398 ◽  
Author(s):  
Vikas V. Gupta ◽  
James S. Im
Keyword(s):  
Supercooled Liquid ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Equilibrium Conditions ◽  
Common Notion ◽  
Athermal Nucleation ◽  
The Common ◽  
Transient Nucleation ◽  
Solid Nucleation ◽  
Kinetics Of

ABSTRACTWe have theoretically investigated the nature and kinetics of solid nucleation in supercooled liquid Si within the framework of the classical nucleation theory, and corresponding to the cases in which the liquids are quenched at extremely high quenching rates (from 109 to 1011 K/s). In doing so, we identify and draw a general conclusion that in addition to the well-treated phenomenon of transient nucleation, one must also consider the mechanism of athermal nucleation in order to properly elucidate the situations that are encountered at such high quenching rates. Moreover, contrary to the common notion that the transient effect is relevant at low temperatures where sluggish kinetics prevail, it is noted that the effect can also become prominent at near-equilibrium conditions due to the increase in the time needed by the embryos to reach the exceedingly large critical size.

The Effects of Si on the Nucleation Kinetics of Ferrite in Dual Phase Steels

2007 ◽  
Vol 26-28 ◽  
pp. 1307-1310 ◽  
Author(s):  
Sang Hwan Lee ◽  
Kyung Jong Lee
Keyword(s):  
Free Energy ◽  
Interfacial Energy ◽  
Free Energy Change ◽  
Nucleation Theory ◽  
Energy Change ◽  
Classical Nucleation Theory ◽  
Nucleation Kinetics ◽  
Kinetics Of ◽  
Volume Free Energy Change ◽  
Thermodynamic Factors

It is generally accepted that Si promotes kinetics of polygonal ferrite due to thermodynamic factors such as Ae3 and maximum amount of ferrite formed. However, in this study, it was found that the difference between the measured rates of ferrite formation in C-Mn steel and Si added steel was much larger than that expected considering only thermodynamic factors. The classical nucleation theory with pillbox model was adopted to figure out what is the most controlling factor in formation of ferrite. The volume free energy change was calculated by use of the dilute solution model. The diffusivity of carbon (DC) was formulated as functions of C, Mn and Si by using experimental data. It was found that the volume free energy change was still predominant but the kinetic factors such as interfacial energy and the diffusivity of carbon by addition of Si were not negligible at lower undercooling. However, with increasing undercooling, the diffusivity of C was the most effective on the ferrite kinetics, though the ambiguity of treating interfacial energy was not yet clear.

A study to investigate phase transitions and nucleation kinetics of nickel and copper

2016 ◽  
Vol 30 (11) ◽  
pp. 1650129 ◽  
Author(s):  
F. A. Celik ◽  
A. K. Yildiz
Keyword(s):  
Molecular Dynamics ◽  
Orientational Order ◽  
Nucleation Theory ◽  
Dynamics Simulation ◽  
Classical Nucleation Theory ◽  
Structural Development ◽  
Nucleation Kinetics ◽  
Embedded Atom ◽  
Bond Orientational Order ◽  
Kinetics Of

In this study, we investigate the homogeneous nucleation kinetics of copper and nickel system during cooling process using molecular dynamics simulation (MDS). The calculation is carried out for a different number of atoms consisting of 500, 2048, 8788 and 13,500 based on embedded atom method (EAM). It is observed that the melting points for the both model increases with increasing the size of systems (i.e. the number of atoms) as expected from Parrinello and Rahman MD method. The interfacial free energies and critical nucleus radius of nickel and copper are also determined by molecular dynamics, and the results are consistent with the classical nucleation theory. The structural development and phase transformation are also determined from the radial distribution function (RDF) and local bond orientational order parameters (LBOO).

Dissolution and Growth Kinetics of Small Crystals in Liquids

1991 ◽  
Vol 238 ◽  
Author(s):  
Michael J. Uttormark ◽  
Michael O. Thompson ◽  
Paulette Clancy
Keyword(s):  
Molecular Dynamics ◽  
Melting Point ◽  
Driving Force ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Equilibrium Melting Point ◽  
Small Crystals ◽  
Dynamics Simulations ◽  
Kinetics Of ◽  
Nucleation Phenomenon

ABSTRACTMolecular Dynamics simulations of the melting of small crystalline clusters (≃800 atoms) in the liquid have been performed at various temperatures above the equilibrium melting point. The melting rates as functions of size and temperature are derived and compared to that predicted by Classical Nucleation Theory. It is found that the driving force for the melting of clusters does not follow the form assumed in the theory, and that this difference is most apparent for clusters containing less than 300 atoms. The implications of these findings on nucleation phenomenon and possible sources for the discrepancies are discussed.

scholarly journals Нуклеация и рост зародышей новой фазы в гетерогенных реакциях

2019 ◽  
Vol 61 (12) ◽  
pp. 2412
Author(s):  
Н.М. Корценштейн
Keyword(s):  
Complex Systems ◽  
Condensed Phase ◽  
Growth Rates ◽  
Heterogeneous Reaction ◽  
Nucleation And Growth ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Definite Kind ◽  
Kinetics Of ◽  
Development Mechanism

Abstract Expressions for the nucleation and growth rates for condensed particles in a heterogeneous reaction of a definite kind have been derived, which allows the kinetics of the formation of the condensed phase in some complex systems to be described. Methods of the classical nucleation theory and an assumption about the reaction development mechanism were used.

Impurity Induced Slowing oF Nucleation in Emulsified Liquids

1998 ◽  
Vol 543 ◽  
Author(s):  
Amy Herhold ◽  
Deniz Ertaş ◽  
Alex J. Levine ◽  
H. E. King
Keyword(s):  
Excellent Agreement ◽  
Careful Consideration ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Emulsion Droplet ◽  
Dynamic Generation ◽  
Liquid To Solid Transition ◽  
Kinetics Of ◽  
Existing Data

AbstractWe report detailed nucleation studies on the liquid -to -solid transition of hexadecane using nearly monodisperse hexadecane -in -water emulsions. A careful consideration of the kinetics of isothermal and nonisothermal freezing show deviations from predictions of classical nucleation theory, if one assumes that the emulsion droplet population is homogeneous. Similar deviations have been observed previously [3]. As an explanation, we propose a novel argument based on the dynamic generation of droplet heterogeneity mediated by mobile impurities. This proposal is in excellent agreement with existing data.

The initiation of crystal growth in glasses

1970 ◽  
Vol 37 (291) ◽  
pp. 741-758 ◽  
Author(s):  
P. S. Rogers
Keyword(s):  
Phase Separation ◽  
Crystal Growth ◽  
Nucleation And Growth ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Nucleating Agents ◽  
Metastable Liquid ◽  
The Third ◽  
Kinetics Of ◽  
Liquid Liquid Phase Separation

SummaryThe application of classical nucleation theory to the initiation of crystal growth in glasses is discussed. Its application to experimental results obtained for the rate of nucleation in three types of glass, one showing nucleation separately from crystal growth, another showing simultaneous nucleation and growth, and the third showing crystal growth after metastable liquid/liquid phase separation, is then described. Recent work on the kinetics of unmixing in glasses is outlined. The influence of so-called ‘nucleating agents’ in the glasses described appears to be exerted through changes in the anionic structure.

Microstructural evolution during decomposition and crystallization of the Cu60Zr20Ti20 amorphous alloy

2004 ◽  
Vol 19 (2) ◽  
pp. 505-512 ◽  
Author(s):  
A. Concustell ◽  
Á. Révész ◽  
S. Suriñach ◽  
L.K. Varga ◽  
G. Heunen ◽  
...  
Keyword(s):  
Amorphous Matrix ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Continuous Heating ◽  
Liquid Region ◽  
Scanning Calorimetry ◽  
Isothermal Heat Treatments ◽  
Crystallization Stage

The effect of continuous heating and isothermal heat treatments on ductile Cu60Zr20Ti20 amorphous ribbons was monitored by differential scanning calorimetry, x-ray diffraction, synchrotron radiation transmission, and high-resolution transmission electron microscopy. Upon continuous heating, the alloy exhibited a glass transition, followed by a supercooled liquid region and two exothermic crystallization stages. Decomposition of the amorphous phase was also observed. The first crystallization stage resulted in the formation of a nanocomposite structure with hexagonal Cu51Zr14 particles embedded in the amorphous matrix, while in the second crystallization stage hexagonal Cu2TiZr-like phase was precipitated. The released enthalpies were 19 J/g and 30 J/g for each crystallization stage. Crystallization kinetics was studied by the classical nucleation theory. Deviations from the Johnson–Mehl–Avrami–Kolmogorov theory may be explained by the contribution of the decomposition of the amorphous matrix.

Homogeneous and Heterogeneous Nucleation of Oxygen in Si-CZ

2011 ◽  
Vol 178-179 ◽  
pp. 495-500
Author(s):  
Josef Kubena ◽  
Alan Kubena ◽  
Ondřej Caha ◽  
Mojmir Meduna
Keyword(s):  
Homogeneous Nucleation ◽  
Annealing Temperature ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Nucleation Kinetics ◽  
Czochralski Silicon ◽  
Oxygen Precipitate ◽  
Different Populations ◽  
The Impact ◽  
Kinetics Of

We present numerical simulations of nucleation kinetics of vacancies and interstitials during RTA and we study the impact of annealing temperature on bulk micro defect concentration. Since the concentration of vacancies and oxygen and also its diffusion kinetics are significantly different inside Czochralski silicon, we assume the nucleation of vacancies and oxygen independent on each other. We show that different populations of voids formed during RTA can influence formation of oxygen precipitate nuclei. According to classical nucleation theory the homogeneous nucleation dominates around temperatures 500 °C while the calculation of oxygen diffusion into the voids shows that the oxygen clusters over the critical size can be formed above temperatures 700 °C. The nuclei concentration of BMD is thus the superposition of homogeneous nucleation below 700 °C and heterogeneous one prevailing above 700 °C.

scholarly journals Effects of Various Inhibitors on the Nucleation of Calcium Oxalate in Synthetic Urine

Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 333
Author(s):  
Yu-Chao Hsu ◽  
Yi-Hsuan Lin ◽  
Lie-Ding Shiau
Keyword(s):  
Calcium Oxalate ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Magnesium Citrate ◽  
Calcium Oxalate Crystals ◽  
Nucleation Kinetics ◽  
Synthetic Urine ◽  
Preferential Nucleation ◽  
Kinetics Of ◽  
Scanning Electron

A new synthetic urine was adopted in this work to study the nucleation kinetics of calcium oxalate using a batch crystallizer for various supersaturations at 37 °C. In the studied new synthetic urine, three additional components (urea, uric acid and creatinine) within the normal physiological ranges were added to the commonly-used synthetic urine to simulate human urine more closely. The interfacial energy for the nucleation of calcium oxalate was determined based on classical nucleation theory using the turbidity induction time measurements. The effects of various inhibitors, including magnesium, citrate, hydroxycitrate, chondroitin sulfate, and phytate, on the nucleation of calcium oxalate were investigated in detail. Scanning electron microscopy was used to examine the influences of these inhibitors on the preferential nucleation of the different hydrates of calcium oxalate crystals.

A New Experimental Method for Investigating the Nucleation Kinetics of Solids in Supercooled Liquid Si

1995 ◽  
Vol 398 ◽  
Author(s):  
H. Jin Song ◽  
James S. Im
Keyword(s):  
Thin Film ◽  
Experimental Method ◽  
Supercooled Liquid ◽  
Isothermal Transformation ◽  
Frequency Range ◽  
Nucleation Kinetics ◽  
Detection Techniques ◽  
Wide Range ◽  
Solid Nucleation ◽  
Kinetics Of

ABSTRACTIn this paper, we first describe and then demonstrate the soundness of a new experimental method that is designed to deliver a wide range of accurately measured nucleation rates of solids in supercooled liquid Si. The method utilizes thin-film processes, as well as laser-quenching and detection techniques, in order to first induce isothermal transformation and then extract the corresponding solid nucleation rates over a frequency range potentially greater than ten orders of magnitude. The technological and scientific gains that can result from acquiring such information are discussed.

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