Inclusion of line tension effect in classical nucleation theory for heterogeneous nucleation: A rigorous thermodynamic formulation and some unique conclusions

2015 ◽  
Vol 142 (10) ◽  
pp. 104706 ◽  
Author(s):  
Sanat K. Singha ◽  
Prasanta K. Das ◽  
Biswajit Maiti
Keyword(s):  
Heterogeneous Nucleation ◽  
Line Tension ◽  
Nucleation Theory ◽  
Classical Nucleation Theory

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

Materials ◽  
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.

Molecular Dynamics Simulation of Nano Cluster-Seed Effects on Heterogeneous Nucleation

2009 ◽  
Author(s):  
Donguk Suh ◽  
Seung-chai Jung ◽  
Woong-sup Yoon
Keyword(s):  
Molecular Dynamics ◽  
Heterogeneous Nucleation ◽  
Three Dimensional ◽  
Seed Mass ◽  
Nucleation Theory ◽  
Dynamics Simulation ◽  
Classical Nucleation Theory ◽  
Supersaturation Ratio ◽  
Order Of Magnitude ◽  
Nano Cluster

A three-dimensional heterogeneous nucleation is simulated by classical molecular dynamics, where the Lennard-Jones gas and solid nano cluster-seed molecules have argon and aluminum properties, respectively. All dimensions of the wall are periodic and a soft core carrier gas within the system controls the temperature rise induced by latent heat of condensation. There are three shapes of cluster-seeds being cube, rod, and sphere, three classes of masses, and the simulation took place under nine supersaturation ratios, making a total of 81 calculations. An analysis of variance was performed under a three-way layout to analyze the cluster-seed and supersaturation ratio effects on the system. For supersaturation ratios above the critical value nucleation rates were evaluated, below growth rates, and overall liquefaction rates were each defined and calculated. Results show that the supersaturation ratio dominantly controls all rates, but seed characteristics are important for the growth of the largest cluster under the critical supersaturation ratio. Overall liquefaction increases subject to an escalation of supersaturation ratio and seed mass. However, the significance of the supersaturation ratio for overall liquefaction suggests that thermal diffusion is more dominant than mass interactions for this system. Homogeneous characteristics are also compared with the heterogeneous system to find that though nucleation may occur for an insufficient supersaturation ratio when a seed is within the system, the addition of a seed does not in fact facilitate the increase in rates of the phenomena at high supersaturation ratios. Finally a comparison with the classical nucleation theory asserts a 3 to 4 order of magnitude difference, which is within the lines of deviation when it comes to theory and molecular simulations.

Atomistic Simulation of Pore Formation in Lipid Bilayers in the Presence of Dimethylsulfoxide: Further Evidence for Entropic Driven Pore Formation

2008 ◽  
Author(s):  
Raghava Alapati ◽  
Dorel Moldovan ◽  
Ram Devireddy
Keyword(s):  
Lipid Bilayer ◽  
Lipid Bilayers ◽  
Pore Formation ◽  
Configurational Entropy ◽  
Line Tension ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Pore Shape ◽  
Dmso Concentration ◽  
Pore Nucleation

In a recent study, Moldovan et al [1] have demonstrated that in the presence of 11.3 mol% dimethylsulfoxide (DMSO) a pore can nucleate and grow spontaneously in a lipid bilayer even in the absence of an externally applied stresses or electric field. The authors rationalized the spontaneous pore nucleation, in the absence of any external driving force, by considering the combined effect of the entropy of pore shape fluctuation and the significant decrease of the bilayer line tension in the presence of DMSO. Building on the classical nucleation theory developed three decades ago by Lister [2] the authors propose a new formulation for the bilayer free energy that incorporates the pore shape configurational entropy. According to this study, in the presence of DMSO, the pore nucleates spontaneously and grows provided the bilayer line tension decreases below a threshold value, λ. In this study we report our recent simulation results on the effect of DMSO concentration on both bilayer line tension and bilayer structural stability with respect to pore nucleation. The lipid bilayer systems investigated in this study by molecular dynamics (MD) consists of 96 molecules (48 in each leaflet) of dimyristoylphosphatidylcholine (DMPC) immersed in DMSO-water solutions at various concentrations. In all MD simulations reported the bilayer systems were followed over 100 ns. Our simulations results indicate the existence of a critical DMSO concentration below which there are no pores nucleated in the lipid bilayers. Our findings corroborate and complement the entropy-based pore nucleation model proposed earlier by Moldovan et al. [1].

Thermodynamic and kinetics investigation of homogeneous and heterogeneous nucleation

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Atefeh Khaleghi ◽  
Seyed Mojtaba Sadrameli ◽  
Mehrdad Manteghian
Keyword(s):  
Nucleation Rate ◽  
Heterogeneous Nucleation ◽  
Review Paper ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Homogeneous Part ◽  
Future Studies ◽  
Fundamental Process

AbstractNucleation is a fundamental process widely studied in different areas of industry and biology. This review paper comprehensively discussed the principles of classical nucleation theory (primary homogeneous), and heterogeneous nucleation. In the homogeneous part, the nucleation rate in the transient and intransient state is monitored and also heterogeneous nucleation is covered. Finally, conclusions have been deduced from the collected works studied here, and offers for future studies are proposed.

scholarly journals Heterogeneous Crystal Nucleation from the Melt in Polyethylene Oxide Droplets on Graphite: Kinetics and Microscopic Structure

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 924
Author(s):  
Muhammad Tariq ◽  
Thomas Thurn-Albrecht ◽  
Oleksandr Dolynchuk
Keyword(s):  
Optical Microscopy ◽  
Polyethylene Oxide ◽  
Heterogeneous Nucleation ◽  
Polarized Light ◽  
Contact Angles ◽  
Nucleation Theory ◽  
Crystal Nucleation ◽  
Classical Nucleation Theory ◽  
Graphite Substrate ◽  
Nucleation Kinetics

It is well known that the crystallization of liquids often initiates at interfaces to foreign solid surfaces. In this study, using polarized light optical microscopy, atomic force microscopy (AFM), and wide-angle X-ray scattering (WAXS), we investigate the effect of substrate–material interactions on nucleation in an ensemble of polyethylene oxide (PEO) droplets on graphite and on amorphous polystyrene (PS). The optical microscopy measurements during cooling with a constant rate explicitly evidenced that the graphite substrate enhances the nucleation kinetics, as crystallization occurred at approximately an 11 °C higher temperature than on PS due to changes in the interactions at the solid interface. This observation allowed us to conclude that graphite induces heterogeneous nucleation in PEO. By employing the classical nucleation theory for analysis of the data with reference to the amorphous PS substrate, the obtained results indicated that the crystal nuclei with contact angles in the range of 100–117° were formed at the graphite interface. Furthermore, we show that heterogeneous nucleation led to a preferred orientation of PEO crystals on graphite, whereas PEO crystals on PS had isotropic orientation. The difference in crystal orientations on the two substrates was also confirmed with AFM, which showed only edge-on lamellae in PEO droplets on graphite compared to unoriented lamellae on PS.

Line tension effects in heterogeneous nucleation theory

1981 ◽  
Vol 75 (5) ◽  
pp. 2441-2446 ◽  
Author(s):  
G. Navascués ◽  
P. Tarazona
Keyword(s):  
Heterogeneous Nucleation ◽  
Line Tension ◽  
Nucleation Theory

Molecular Dynamics Simulation of Three-Dimensional Heterogeneous Nucleation

2011 ◽  
Author(s):  
Donguk Suh ◽  
Kenji Yasuoka
Keyword(s):  
Molecular Dynamics ◽  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Three Dimensional ◽  
Nucleation Theory ◽  
Dynamics Simulation ◽  
Classical Nucleation Theory ◽  
Supersaturation Ratio ◽  
Seed Growth ◽  
Thermodynamic Conditions

Nanoparticle growth based on three-dimensional heterogeneous nucleation was simulated by classical molecular dynamics. To collectively observe the effects of the dimension of seeds and thermodynamic conditions, seed size and system supersaturation ratio were the factors that were examined to see if they influenced the nucleation rates. Two stages were found to exist within the system, where the first stage is from the seed growth and the second from homogeneous nucleation. The Yasuoka-Matsumoto method was used to calculate the rates. The homogeneous nucleation characteristics coincided with the classical nucleation theory, but heterogeneous nucleation showed an irregular form, which at the current state cannot not be fully understood. Kinetic analysis was also performed to calculate the critical nucleus size and better understand the seed growth characteristics. All in all, the seed effects were insignificant to the overall nucleation characteristics for this system.

scholarly journals Formation of ice particles through nucleation in the mesosphere

2021 ◽  
Author(s):  
Kyoko K. Tanaka ◽  
Ingrid Mann ◽  
Yuki Kimura
Keyword(s):  
Heterogeneous Nucleation ◽  
Amorphous State ◽  
Nucleation Theory ◽  
Molecular Cluster ◽  
Classical Nucleation Theory ◽  
Numerical Density ◽  
Nucleation Process ◽  
Dust Grains ◽  
Atmospheric Conditions ◽  
Ice Particles

Abstract. Observations of polar mesospheric clouds have revealed the presence of solid ice particles in the upper mesosphere at high latitudes; however, their formation mechanism remains uncertain. In this study, we investigated the formation process of ice particles through nucleation from small amounts of water vapor at low temperatures. Previous studies that used classical nucleation theory have shown that amorphous solid water particles can nucleate homogeneously at conditions that are present in the mesosphere. However, the rate predictions for water in classical nucleation theory disagree with experimental measurements by several orders of magnitude. We adopted a semi-phenomenological model for the nucleation process, which corrects the evaluation of the molecular cluster formation energy using the second virial coefficient, which agrees with both experiments and molecular dynamics simulations. To calculate the nucleation process, we applied atmospheric conditions for the temperature, pressure, numerical density of dust grains, and cooling rate. The results indicate that homogeneous water nucleation is extremely unlikely to occur in the mesosphere, while heterogeneous nucleation occurs effectively. Dust grains generated by meteor ablation can serve as nuclei for heterogeneous nucleation. We also showed that the ice can form directly in a crystalline state, rather than an amorphous state.

scholarly journals A New Atomistic Mechanism for Heterogeneous Nucleation in the Systems with Negative Lattice Misfit: Creating a 2DTemplate for Crystal Growth

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 478
Author(s):  
Zhongyun Fan ◽  
Hua Men ◽  
Yun Wang ◽  
Zhongping Que
Keyword(s):  
Heterogeneous Nucleation ◽  
Twist Angle ◽  
Lattice Misfit ◽  
Md Simulations ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Dislocation Network ◽  
Layer By Layer ◽  
Electron Microscopic ◽  
Spherical Cap

Heterogeneous nucleation is a widespread phenomenon in both nature and technology. However, our current understanding is largely confined to the classical nucleation theory (CNT) postulated over a century ago, in which heterogeneous nucleation occurs stochastically to form a spherical cap facilitated by a substrate. In this paper, we show that heterogeneous nucleation in systems with negative lattice misfit completes deterministically within three atomic layers by structural templating to form a two-dimentional template from which the new phase can grow. Using molecular dynamics (MD) simulations of a generic system containing metallic liquid (Al) and a substrate of variable lattice misfit (fcc lattice with fixed Al atoms), we found that heterogeneous nucleation proceeds layer-by-layer: the first layer accommodates misfit through a partial edge dislocation network; the second layer twists an angle through a partial screw dislocation network to reduce lattice distortion; and the third layer creates a crystal plane of the solid (the 2D nucleus) that templates further growth. The twist angle of the solid relative to the substrate as a signature of heterogeneous nucleation in the systems with negative lattice misfit has been validated by high resolution transmission electron microscopic (HRTEM) examination of TiB2/Al and TiB2/α-Al15(Fe, Mn)3Si2 interfaces in two different Al-alloys.

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