Homogeneous and Heterogeneous Nucleation of Oxygen in Si-CZ

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.

Download Full-text

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

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.26-28.1307 ◽

2007 ◽

Vol 26-28 ◽

pp. 1307-1310 ◽

Cited By ~ 1

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.

Download Full-text

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

Modern Physics Letters B ◽

10.1142/s0217984916501293 ◽

2016 ◽

Vol 30 (11) ◽

pp. 1650129 ◽

Cited By ~ 1

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).

Download Full-text

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

Crystals ◽

10.3390/cryst10040333 ◽

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.

Download Full-text

Temperature-dependent nucleation kinetics of Guinier-Preston zones in Al–Cu alloys: An atomistic kinetic Monte Carlo and classical nucleation theory approach

Acta Materialia ◽

10.1016/j.actamat.2019.08.032 ◽

2019 ◽

Vol 179 ◽

pp. 262-272 ◽

Cited By ~ 5

Author(s):

Hiroshi Miyoshi ◽

Hajime Kimizuka ◽

Akio Ishii ◽

Shigenobu Ogata

Keyword(s):

Monte Carlo ◽

Kinetic Monte Carlo ◽

Nucleation Theory ◽

Classical Nucleation Theory ◽

Theory Approach ◽

Nucleation Kinetics ◽

Temperature Dependent ◽

Cu Alloys ◽

Kinetics Of

Download Full-text

Nucleation Behavior of a Single Al-20Si Particle Rapidly Solidified in a Fast Scanning Calorimeter

Materials ◽

10.3390/ma14112920 ◽

2021 ◽

Vol 14 (11) ◽

pp. 2920

Author(s):

Qin Peng ◽

Bin Yang ◽

Benjamin Milkereit ◽

Dongmei Liu ◽

Armin Springer ◽

...

Keyword(s):

Cooling Rate ◽

Rapid Solidification ◽

Heterogeneous Nucleation ◽

Nucleation Theory ◽

Classical Nucleation Theory ◽

Solidification Behavior ◽

Nucleation Kinetics ◽

Nucleation Behavior ◽

Nucleation Undercooling ◽

Primary Si

Understanding the rapid solidification behavior characteristics, nucleation undercooling, and nucleation mechanism is important for modifying the microstructures and properties of metal alloys. In order to investigate the rapid solidification behavior in-situ, accurate measurements of nucleation undercooling and cooling rate are required in most rapid solidification processes, e.g., in additive manufacturing (AM). In this study, differential fast scanning calorimetry (DFSC) was applied to investigate the nucleation kinetics in a single micro-sized Al-20Si (mass%) particle under a controlled cooling rate of 5000 K/s. The nucleation rates of primary Si and secondary α-Al phases were calculated by a statistical analysis of 300 identical melting/solidification experiments. Applying a model based on the classical nucleation theory (CNT) together with available thermodynamic data, two different heterogeneous nucleation mechanisms of primary Si and secondary α-Al were proposed, i.e., surface heterogeneous nucleation for primary Si and interface heterogenous nucleation for secondary α-Al. The present study introduces a practical method for a detailed investigation of rapid solidification behavior of metal particles to distinguish surface and interface nucleation.

Download Full-text

Analysis of isothermal and cooling rate dependent immersion freezing by a unifying stochastic ice nucleation model

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-13109-2015 ◽

2015 ◽

Vol 15 (9) ◽

pp. 13109-13166

Author(s):

P. A. Alpert ◽

D. A. Knopf

Keyword(s):

Cooling Rate ◽

Surface Area ◽

Ice Nucleation ◽

Rate Dependence ◽

Nucleation Theory ◽

Freezing Process ◽

Nucleation Kinetics ◽

Rate Dependent ◽

Immersion Freezing ◽

The Impact

Abstract. Immersion freezing is an important ice nucleation pathway involved in the formation of cirrus and mixed-phase clouds. Laboratory immersion freezing experiments are necessary to determine the range in temperature (T) and relative humidity (RH) at which ice nucleation occurs and to quantify the associated nucleation kinetics. Typically, isothermal (applying a constant temperature) and cooling rate dependent immersion freezing experiments are conducted. In these experiments it is usually assumed that the droplets containing ice nuclei (IN) all have the same IN surface area (ISA), however the validity of this assumption or the impact it may have on analysis and interpretation of the experimental data is rarely questioned. A stochastic immersion freezing model based on first principles of statistics is presented, which accounts for variable ISA per droplet and uses physically observable parameters including the total number of droplets (Ntot) and the heterogeneous ice nucleation rate coefficient, Jhet(T). This model is applied to address if (i) a time and ISA dependent stochastic immersion freezing process can explain laboratory immersion freezing data for different experimental methods and (ii) the assumption that all droplets contain identical ISA is a valid conjecture with subsequent consequences for analysis and interpretation of immersion freezing. The simple stochastic model can reproduce the observed time and surface area dependence in immersion freezing experiments for a variety of methods such as: droplets on a cold-stage exposed to air or surrounded by an oil matrix, wind and acoustically levitated droplets, droplets in a continuous flow diffusion chamber (CFDC), the Leipzig aerosol cloud interaction simulator (LACIS), and the aerosol interaction and dynamics in the atmosphere (AIDA) cloud chamber. Observed time dependent isothermal frozen fractions exhibiting non-exponential behavior with time can be readily explained by this model considering varying ISA. An apparent cooling rate dependence ofJhet is explained by assuming identical ISA in each droplet. When accounting for ISA variability, the cooling rate dependence of ice nucleation kinetics vanishes as expected from classical nucleation theory. The model simulations allow for a quantitative experimental uncertainty analysis for parameters Ntot, T, RH, and the ISA variability. In an idealized cloud parcel model applying variability in ISAs for each droplet, the model predicts enhanced immersion freezing temperatures and greater ice crystal production compared to a case when ISAs are uniform in each droplet. The implications of our results for experimental analysis and interpretation of the immersion freezing process are discussed.

Download Full-text

Nucleation rates and the kinetics of particle growth II. The birth and death process

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1964.0014 ◽

1964 ◽

Vol 277 (1369) ◽

pp. 167-182 ◽

Cited By ~ 39

Keyword(s):

Steady State ◽

Homogeneous Nucleation ◽

Time Lag ◽

Particle Growth ◽

Statistical Problem ◽

Death Process ◽

Birth And Death Process ◽

Growth Mechanisms ◽

Nucleation Kinetics ◽

Kinetics Of

The model considered in part I is generalized to include growth mechanisms in which the chemical reaction which proceeds at the particle-atm osphere interface is reversible, so that molecules may evaporate from a particle as well as condense upon it. The Becker-Döring-Zeldovich-Frenkel theory of homogeneous nucleation kinetics is then reviewed in the light of the known statistical problem of the birth -and -death process, and an improved approximation is introduced which significantly alters the calculated results. Both steady-state nucleation kinetics and the time lag problem are discussed.

Download Full-text

Nucleation and Glass Formation

MRS Proceedings ◽

10.1557/proc-57-99 ◽

1985 ◽

Vol 57 ◽

Cited By ~ 1

Author(s):

D. R. Uhlmann ◽

M. C. Weinberg

Keyword(s):

Glass Formation ◽

Nucleation Theory ◽

Crystal Nucleation ◽

Oxide Glass ◽

Classical Nucleation Theory ◽

Nucleation Kinetics ◽

Formation Behavior ◽

Homogeneous Crystal ◽

Exponential Factors

AbstractThe role of nucleation kinetics in affecting glass formation behavior is discussed. Also considered are measurements of homogeneous crystal nucleation in a variety of liquids. For a number of oxide glass-forming liquids, available data indicate pre-exponential factors which are larger than those predicted from classical nucleation theory by factors of 1017 to 1049. Possible sources of this discrepancy are discussed.

Download Full-text