Influence of rapid cooling on crystal nucleation in lysozyme crystallization solutions of low supersaturation

2021 ◽  
pp. 1-10
Author(s):  
Petya P. Elenska ◽  
Ivaylo L. Dimitrov
Keyword(s):  
Crystal Nucleation ◽  
Rapid Cooling

Computer Simulation of the Phase-change Cycle of GST-225

2008 ◽  
Vol 1072 ◽  
Author(s):  
Stephen Elliott ◽  
Jozsef Hegedus
Keyword(s):  
Phase Change ◽  
Homogeneous Nucleation ◽  
Amorphous State ◽  
Crystal Nucleation ◽  
Neutron Diffraction Data ◽  
Structural Units ◽  
Slow Cooling ◽  
Rapid Cooling ◽  
Rocksalt Structure ◽  
First Time

ABSTRACTWe have simulated for the first time, by ab initio molecular dynamics, the complete phase-transformation cycle (liquid-crystal, liquid-amorphous-crystal) of the phase-change (PC) memory material Ge2Sb2Te5 (GST-225). We have observed that rapid cooling of the simulated melt leads to an amorphous product, whereas slow cooling results in the metastable rocksalt crystal. Furthermore, crystallization to the same structure is observed to occur on annealing the quenched amorphous model to temperatures below the melting temperature. The RDF of the energy-relaxed amorphous GST-225 structure agrees very well with experimental neutron-diffraction data, reproducing the shortening of the Ge-Te bond length relative to that in the rocksalt crystal structure observed experimentally.We have observed crystal-nucleation events in the simulated liquid that have been identified as the creation of connected near-regular square fourfold rings, the basic structural units of the rocksalt structure. These crystal nuclei are invariably found to be quenched into the amorphous state on rapid cooling of the simulated melt. This observation therefore explains why GST materials crystallize so readily and why homogeneous nucleation is so facile.

Domain coarsening by grain boundary migration in ordered Ni4Mo

1986 ◽  
Vol 44 ◽  
pp. 560-561
Author(s):  
K. Vasudevan ◽  
H. P. Kao ◽  
C. R. Brooks ◽  
E. E. Stansbury
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Short Range ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
Rapid Cooling ◽  
Temperature Range ◽  
Fee Structure ◽  
Domain Coarsening ◽  
Boundary Reaction

The Ni4Mo alloy has a short-range ordered fee structure (α) above 868°C, but transforms below this temperature to an ordered bet structure (β) by rearrangement of atoms on the fee lattice. The disordered α, retained by rapid cooling, can be ordered by appropriate aging below 868°C. Initially, very fine β domains in six different but crystallographically related variants form and grow in size on further aging. However, in the temperature range 600-775°C, a coarsening reaction begins at the former α grain boundaries and the alloy also coarsens by this mechanism. The purpose of this paper is to report on TEM observations showing the characteristics of this grain boundary reaction.

scholarly journals Crystallization of Random Metallocene-Catalyzed Propylene-Based Copolymers with Ethylene and 1-Hexene on Rapid Cooling

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2091
Author(s):  
Daniela Mileva ◽  
Jingbo Wang ◽  
René Androsch ◽  
Katalee Jariyavidyanont ◽  
Markus Gahleitner ◽  
...  
Keyword(s):  
Mechanical Performance ◽  
Metallocene Catalyst ◽  
Nucleating Agent ◽  
Random Copolymers ◽  
Rapid Cooling ◽  
Significant Difference ◽  
Chip Calorimetry ◽  
High Cooling Rates ◽  
Fast Scanning Chip Calorimetry

Propylene-based random copolymers with either ethylene or 1-hexene as comonomer, produced using a metallocene catalyst, were studied regarding their crystallization behaviors, with a focus on rapid cooling. To get an impression of processing effects, fast scanning chip calorimetry (FSC) was used in addition to the characterization of the mechanical performance. When comparing the comonomer type and the relation to commercial grades based on Ziegler–Natta-type catalysts, both an interaction with the catalyst-related regio-defects and a significant difference between ethylene and 1-hexene was observed. A soluble-type nucleating agent was found to modify the behavior, but to an increasingly lesser degree at high cooling rates.

scholarly journals The exploration of the crystal nucleation parameters and physico-chemical analysis of a single crystal: 2-amino-4,6-dimethoxypyrimidinium hydrogen (2R,3R)-tartrate 2-amino-4,6-dimethoxypyrimidine

RSC Advances ◽  
2021 ◽  
Vol 11 (26) ◽  
pp. 15710-15721
Author(s):  
Paavai Era ◽  
RO. MU. Jauhar ◽  
V. Viswanathan ◽  
M. Madhangi ◽  
G. Vinitha ◽  
...  
Keyword(s):  
Chemical Analysis ◽  
Single Crystal ◽  
Chemical Properties ◽  
Crystal Nucleation ◽  
Nucleation Parameters ◽  
Physico Chemical

This paper discusses the structural orientations and the physico-chemical properties of a single crystal of 2-amino-4,6-dimethoxypyrimidinium hydrogen (2R,3R)-tartrate 2-amino-4,6-dimethoxypyrimidine (2ADT).

scholarly journals In-Situ High-Energy X-ray Diffraction Study of Austenite Decomposition During Rapid Cooling and Isothermal Holding in Two HSLA Steels

2021 ◽  
Vol 52 (5) ◽  
pp. 1812-1825
Author(s):  
Sen Lin ◽  
Ulrika Borggren ◽  
Andreas Stark ◽  
Annika Borgenstam ◽  
Wangzhong Mu ◽  
...  
Keyword(s):  
Isothermal Holding ◽  
Weight Percent ◽  
High Energy ◽  
Decomposition Kinetics ◽  
Bainitic Transformation ◽  
Austenite Decomposition ◽  
X Ray Diffraction ◽  
Rapid Cooling ◽  
X Ray

AbstractIn-situ high-energy X-ray diffraction experiments with high temporal resolution during rapid cooling (280 °C s−1) and isothermal heat treatments (at 450 °C, 500 °C, and 550 °C for 30 minutes) were performed to study austenite decomposition in two commercial high-strength low-alloy steels. The rapid phase transformations occurring in these types of steels are investigated for the first time in-situ, aiding a detailed analysis of the austenite decomposition kinetics. For the low hardenability steel with main composition Fe-0.08C-1.7Mn-0.403Si-0.303Cr in weight percent, austenite decomposition to polygonal ferrite and bainite occurs already during the initial cooling. However, for the high hardenability steel with main composition Fe-0.08C-1.79Mn-0.182Si-0.757Cr-0.094Mo in weight percent, the austenite decomposition kinetics is retarded, chiefly by the Mo addition, and therefore mainly bainitic transformation occurs during isothermal holding; the bainitic transformation rate at the isothermal holding is clearly enhanced by lowered temperature from 550 °C to 500 °C and 450 °C. During prolonged isothermal holding, carbide formation leads to decreased austenite carbon content and promotes continued bainitic ferrite formation. Moreover, at prolonged isothermal holding at higher temperatures some degenerate pearlite form.

scholarly journals Factors affecting cholesterol monohydrate crystal nucleation time in model systems of supersaturated bile.

1985 ◽  
Vol 26 (9) ◽  
pp. 1102-1111 ◽  
Author(s):  
A Kibe ◽  
M A Dudley ◽  
Z Halpern ◽  
M P Lynn ◽  
A C Breuer ◽  
...  
Keyword(s):  
Model Systems ◽  
Crystal Nucleation ◽  
Nucleation Time ◽  
Factors Affecting ◽  
Cholesterol Monohydrate

scholarly journals Effect of C-S-H Nucleating Agent on Cement Hydration

2021 ◽  
Vol 11 (14) ◽  
pp. 6638
Author(s):  
Wenhao Zhao ◽  
Xuping Ji ◽  
Yaqing Jiang ◽  
Tinghong Pan
Keyword(s):  
Fractal Dimension ◽  
Cement Hydration ◽  
Nucleating Agent ◽  
Crystal Nucleation ◽  
Enhancement Effect ◽  
Hydration Products ◽  
Hydration Degree ◽  
Hydration Kinetics ◽  
Cement Mortars ◽  
Early Strength

This work aims to study the effect of a nucleating agent on cement hydration. Firstly, the C-S-H crystal nucleation early strength agent (CNA) is prepared. Then, the effects of CNA on cement hydration mechanism, early strength enhancement effect, C-S-H content, 28-days hydration degree and 28-days fractal dimension of hydration products are studied by hydration kinetics calculation, resistivity test, BET specific surface area test and quantitative analysis of backscattered electron (BSE) images, respectively. The results show that CNA significantly improves the hydration degree of cement mixture, which is better than triethanolamine (TEA). CNA shortens the beginning time of the induction period by 49.3 min and the end time of the cement hydration acceleration period by 105.1 min than the blank sample. CNA increases the fractal dimension of hydration products, while TEA decreases the fractal dimension. CNA significantly improves the early strength of cement mortars; the 1-day and 3-days strength of cement mortars with CNA are more than the 3-days and 7-days strength of the blank sample. These results will provide a reference for the practical application of the C-S-H nucleating agent.

Epitaxial Growth Following Crystal Nucleation in Laser-Quenched Si Films on SiO2

2015 ◽  
Vol 1770 ◽  
pp. 67-72
Author(s):  
Vernon K. Wong ◽  
A. M. Chitu ◽  
A. B. Limanov ◽  
James S. Im
Keyword(s):  
Epitaxial Growth ◽  
Growth Model ◽  
Crystal Nucleation ◽  
Key Factors ◽  
Complete Melting ◽  
Melting Regime ◽  
Direct Growth ◽  
Crystal Core ◽  
Excimer Laser Irradiation ◽  
Si Films

ABSTRACTWe have investigated the solidified microstructure of nucleation-generated grains obtained via complete melting of Si films on SiO2 at high nucleation temperatures. This was achieved using a high-temperature-capable hot stage in conjunction with excimer laser irradiation. As predicted by the direct-growth model that considers (1) the evolution in the temperature of the solidifying interface and (2) the subsequent modes of growth (consisting of amorphous, defective, and epitaxial) as key factors, we were able to observe the appearance of “normal” grains that possess a single-crystal core area. These grains, which are in contrast to previously reported flower-shaped grains that fully make up the microstructure of the solidified films obtained via irradiation at lower preheating temperatures (and amongst which these “normal” grains emerge), indicate that epitaxial growth of nucleated crystals must have taken place within the grains. We discuss the implications of our findings regarding (1) the validity of the direct-growth model, (2) the nature of the heterogeneous nucleation mechanism, and (3) the alternative explanations and assumptions that have been previously employed in order to explain the microstructure of Si films obtained via nucleation and growth within the complete melting regime.

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