Energy barrier effect on transient nucleation kinetics

2000 ◽  
Author(s):  
Igor L. Maksimov
Keyword(s):  
Energy Barrier ◽  
Barrier Effect ◽  
Nucleation Kinetics ◽  
Transient Nucleation

Time-Dependent Capture Numbers with Repulsive Pair Interactions: Cu/Cu(111) and Ge/Si(001)

2002 ◽  
Vol 749 ◽  
Author(s):  
J. A. Venables ◽  
H. Brune ◽  
J. Drucker
Keyword(s):  
Time Dependent ◽  
Diffusion Limit ◽  
Interpolation Scheme ◽  
Nucleation Kinetics ◽  
Diffusion Limited ◽  
Repulsive Energy ◽  
Two Systems ◽  
Transient Nucleation ◽  
Similarities And Differences ◽  
And Diffusion

ABSTRACTRecent experiments and calculations have shown that weak repulsive interactions between adsorbate atoms may shift nucleation kinetics from the well-known diffusion limit towards the attachment-limited case. The distinctions between diffusion- and attachment-limited kinetics are clarified, and the increased importance of the transient nucleation regime in the latter case is shown to be due to a combination of delayed nucleation and reduced capture. A time-dependent interpolation scheme between attachment- and diffusion-limited capture numbers is proposed, and tested against KMC simulations. Using this scheme to interpret recent STM results on Cu/Cu(111), bounds on the maximum adatom-adatom potential repulsive energy of 12±2 meV are deduced. Time-dependent effects also occur in the growth and ripening of strained Ge islands on Si(001), and the similarities and differences between these two systems are discussed.

Phase Selection in Undercooled Melts of Peritectic Cu-Ge Alloys

2010 ◽  
Vol 649 ◽  
pp. 47-52
Author(s):  
J.R. Gao ◽  
G. Luo ◽  
X.H. Luo
Keyword(s):  
Copper Substrate ◽  
Electromagnetic Levitation ◽  
Drop Tube ◽  
Undercooled Liquid ◽  
Nucleation Kinetics ◽  
Direct Crystallization ◽  
Phase Selection ◽  
Nucleation Barrier ◽  
Transient Nucleation ◽  
Undercooled Melts

Phase selection in undercooled melts of Cu-14.8Ge and Cu-18Ge compositions was investigated using the electromagnetic levitation technique in combination with substrate quenching and a drop tube. The results showed that the levitated and gas-cooled samples were all solidified into a microstructure consisting of primary -Cu plus peritectic -Cu5Ge. However, the samples quenched onto a copper substrate showed a segregation-free microstructure in the chilled zone, suggesting direct crystallization of the peritectic -Cu5Ge phase from a highly undercooled liquid. The Cu-18Ge samples quenched onto a glass substrate as well as those solidified in the drop tube also showed a segregation-free microstructure. An analysis of the nucleation kinetics revealed that the -Cu5Ge phase had a larger nucleation barrier than that of -Cu for all accessible undercoolings. It was suggested that phase selection in the undercooled Cu-Ge liquid might be controlled by transient nucleation kinetics.

scholarly journals Nucleation and particle growth with fluctuating rates at the intermediate stage of phase transitions in metastable systems

2014 ◽  
Vol 470 (2162) ◽  
pp. 20130647 ◽  
Author(s):  
D. V. Alexandrov ◽  
I. G. Nizovtseva
Keyword(s):  
Phase Transitions ◽  
Exact Analytical Solution ◽  
Particle Growth ◽  
Intermediate Stage ◽  
Solid Particles ◽  
Nucleation Kinetics ◽  
Differential Model ◽  
Transient Nucleation ◽  
Metastable Systems ◽  
Supersaturated Solutions

An exact analytical solution of an integro-differential model describing the transient nucleation of solid particles (nuclei) and their growth with fluctuating rates at the intermediate stage of bulk phase transitions in metastable systems is constructed. Two important cases of the Weber–Volmer–Frenkel–Zel'dovich and Mier nucleation kinetics are detailed for supercooled melts and supersaturated solutions.

AEM analysis of solidification catalysts in atomized Fe-Ni

1986 ◽  
Vol 44 ◽  
pp. 584-585
Author(s):  
Matthew R. Libera
Keyword(s):  
Powder Particle ◽  
Alloy Composition ◽  
Particle Diameter ◽  
Metastable Phases ◽  
Liquid Droplets ◽  
Nucleation Kinetics ◽  
Ni Alloys ◽  
Nonequilibrium Solidification

The liquid droplets produced by atomization processes are believed to undergo substantial supercooling during solidification, because the catalytic heterogeneities, for statistical reasons, tend to be isolated in the larger droplets. This supercooling can lead to the nucleation of metastable phases. As part of a study on the effect of liquid supercooling on nonequilibrium solidification, three binary Fe-Ni alloys have been produced by conventional argon atomization (Fe-20Ni, Fe-30Ni, and Fe-40Ni). The primary variables in these experiments are: i) the alloy composition; and ii) the powder particle diameter (inversely proportional to supercooling). Of particular interest in this system is the competitive nucleation kinetics between the stable fee and metastable bec phases. Bcc is expected to nucleate preferentially with decreasing %Ni and decreasing particle diameter.

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