On heterogeneous nucleation in a supercooled melt

Mullite (3Al2O32SiO2) can be fabricated by transient viscous sintering using composite particles which consist of inner cores of a-alumina and outer coatings of amorphous silica. Powder compacts prepared with these particles are sintered to almost full density at relatively low temperatures (~1300°C) and converted to dense, fine-grained mullite at higher temperatures (>1500°C) by reaction between the alumina core and the silica coating. In order to achieve complete mullitization, optimal conditions for coating alumina particles with amorphous silica must be achieved. Formation of amorphous silica can occur in solution (homogeneous nucleation) or on the surface of alumina (heterogeneous nucleation) depending on the degree of supersaturation of the solvent in which the particles are immersed. Successful coating of silica on alumina occurs when heterogeneous nucleation is promoted and homogeneous nucleation is suppressed. Therefore, one key to successful coating is an understanding of the factors such as pH and concentration that control silica nucleation in aqueous solutions. In the current work, we use TEM to determine the optimal conditions of this processing.

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Simulation of heterogeneous nucleation in liquid argon with particulate matter molecular dynamics methods

Теплофизика высоких температур ◽

10.31857/s004036440003384-6 ◽

2018 ◽

Vol 56 (5) ◽

pp. 905-908

Author(s):

V. Malyshev ◽

◽

E. Moiseeva ◽

Keyword(s):

Molecular Dynamics ◽

Particulate Matter ◽

Heterogeneous Nucleation ◽

Liquid Argon ◽

Molecular Dynamics Methods

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Strain-induced variant selection in heterogeneous nucleation of α -Ti at screw dislocations in β -Ti

Physical Review Materials ◽

10.1103/physrevmaterials.2.083606 ◽

2018 ◽

Vol 2 (8) ◽

Cited By ~ 1

Author(s):

Max Poschmann ◽

Joseph Lin ◽

Henry Geerlings ◽

Ian S. Winter ◽

D. C. Chrzan

Keyword(s):

Heterogeneous Nucleation ◽

Variant Selection ◽

Screw Dislocations

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First Principle Study of TiB2 (0001)/γ-Fe (111) Interfacial Strength and Heterogeneous Nucleation

Materials ◽

10.3390/ma14061573 ◽

2021 ◽

Vol 14 (6) ◽

pp. 1573

Author(s):

Qin Wang ◽

Peikang Bai ◽

Zhanyong Zhao

Keyword(s):

Stainless Steel ◽

Heterogeneous Nucleation ◽

316L Stainless Steel ◽

Interfacial Strength ◽

Interface Energy ◽

Interface Fracture ◽

Partial Density ◽

Covalent Bonds ◽

Tib2 Particles ◽

Adhesion Work

TiB2/316L stainless steel composites were prepared by selective laser melting (SLM), and the adhesion work, interface energy and electronic structure of TiB2/γ-Fe interface in TiB2/316L stainless steel composites were investigated to explore the heterogeneous nucleation potential of γ-Fe grains on TiB2 particles using first principles. Six interface models composed of three different stacking positions and two different terminations were established. The B-terminated-top 2 site interface (“B-top 2”) was the most stable because of the largest adhesion work, smallest interfacial distances, and smallest interfacial energy. The difference charge density and partial density of states indicated that a large number of strong Fe-B covalent bonds were formed near the “B-top 2” interface, which increased the stability of interface. Fracture analysis revealed that the bonding strength of the “B-top 2” interface was higher than that of the Fe matrix, and it was difficult to fracture at the interface. The interface energy at the Ti-poor position in the “B-top 2” interface model was smaller than that of the γ-Fe/Fe melt, indicating that TiB2 had strong heterogeneous nucleation potency for γ-Fe.

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Non-Isothermal Crystallization Kinetics of Poly(Ethylene Glycol)–Poly(l-Lactide) Diblock Copolymer and Poly(Ethylene Glycol) Homopolymer via Fast-Scan Chip-Calorimeter

Polymers ◽

10.3390/polym13071156 ◽

2021 ◽

Vol 13 (7) ◽

pp. 1156

Author(s):

Dejia Chen ◽

Lisha Lei ◽

Meishuai Zou ◽

Xiaodong Li

Keyword(s):

Ethylene Glycol ◽

Heterogeneous Nucleation ◽

Isothermal Crystallization ◽

Crystallization Process ◽

Poly Ethylene Glycol ◽

Ozawa Method ◽

Isothermal Crystallization Kinetics ◽

Fast Cooling ◽

Poly Ethylene ◽

Kinetics Of

The non-isothermal crystallization kinetics of double-crystallizable poly(ethylene glycol)–poly(l-lactide) diblock copolymer (PEG-PLLA) and poly(ethylene glycol) homopolymer (PEG) were studied using the fast cooling rate provided by a Fast-Scan Chip-Calorimeter (FSC). The experimental data were analyzed by the Ozawa method and the Kissinger equation. Additionally, the total crystallization rate was represented by crystallization half time t1/2. The Ozawa method is a perfect success because secondary crystallization is inhibited by using fast cooling rate. The first crystallized PLLA block provides nucleation sites for the crystallization of PEG block and thus promotes the crystallization of the PEG block, which can be regarded as heterogeneous nucleation to a certain extent, while the method of the PEG block and PLLA block crystallized together corresponds to a one-dimensional growth, which reflects that there is a certain separation between the crystallization regions of the PLLA block and PEG block. Although crystallization of the PLLA block provides heterogeneous nucleation conditions for PEG block to a certain extent, it does not shorten the time of the whole crystallization process because of the complexity of the whole crystallization process including nucleation and growth.

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Scaling properties of induction times in heterogeneous nucleation

The Journal of Chemical Physics ◽

10.1063/1.461194 ◽

1991 ◽

Vol 95 (12) ◽

pp. 9148-9150 ◽

Cited By ~ 19

Author(s):

Vitaly A. Shneidman ◽

Michael C. Weinberg

Keyword(s):

Heterogeneous Nucleation ◽

Scaling Properties ◽

Induction Times

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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.

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