scholarly journals Multiple Pathways in NaCl Homogeneous Crystal Nucleation

2021 ◽  
Author(s):  
Aaron Finney ◽  
Matteo Salvalaglio
Keyword(s):  
Single Step ◽  
Crystal Nucleation ◽  
Crystalline Order ◽  
Homogeneous Crystal ◽  
Step Mechanism

NaCl crystal nucleation from metastable solutions has long been considered to occur according to a single-step mechanism where the growth in the size and crystalline order of the emerging nuclei...

The effect of decationation of hydroxylated HNaY zeolites on their interaction with ethylene and propylene. hydrogen complexes, oligomeration and isotope exchange

1980 ◽  
Vol 45 (11) ◽  
pp. 3101-3115 ◽  
Author(s):  
Ludmila Kubelková ◽  
Jana Nováková ◽  
Zdeněk Dolejšek ◽  
Pavel Jírů
Keyword(s):  
Isotope Exchange ◽  
Decisive Role ◽  
Single Step ◽  
Hydroxyl Groups ◽  
Isotope Exchange Reaction ◽  
Factors Affecting ◽  
Step Mechanism ◽  
Formed Hydrogen ◽  
Lower Basicity ◽  
Multiple Step

The effect of decationation on the interaction of propylene and ethylene with the hydroxylated forms of HNaY zeolites has been studied. The compounds formed in the zeolite cavities were studied using their infrared spectra, the composition of the gaseous phase was followed by mass spectrometry. The results showed that among factors affecting the interaction with propylene properties of hydroxyl groups play the decisive role. With the increasing decationation of the zeolite the strength of the OH bond in the hydrogen complex of the large-cavity hydroxyls with propylene decreased and the rate of propylene oligomeration at 310 K as well as the isotope exchange rate of propylene-d6 with the zeolite hydroxyls at 570 K increased. The propylene isotope exchange reaction proceeded by the multiple-step mechanism. In the case of ethylene only the physical sorption with a non-specific character was observed at 310 K. The adsorbed amount increased with the increasing content of Na+ ions in the zeolite (with the decreasing decationation). A part of the adsorbed molecules formed hydrogen complexes with hydroxyls of large cavities. The observed lower weakening of the OH bond was in agreement with the lower basicity of ethylene if compared with propylene. The isotope exchange of ethylene-d4 with the zeolite hydroxyls proceeded by a single-step mechanism, it had an autocatalytic character and its rate was 70 times lower than that of the isotope exchange of propylene-d6 with OH.

scholarly journals Molecular Dynamics Simulations of Crystal Nucleation near Interfaces in Incompatible Polymer Blends

Polymers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 347
Author(s):  
Wenlin Zhang ◽  
Lingyi Zou
Keyword(s):  
Molecular Dynamics ◽  
Polymer Blends ◽  
Md Simulations ◽  
Nucleation And Growth ◽  
Crystal Nucleation ◽  
Crystalline Order ◽  
Mobile Species ◽  
Deep Supercooling ◽  
Crystallizable Polymer ◽  
Dynamics Simulations

We apply molecular dynamics (MD) simulations to investigate crystal nucleation in incompatible polymer blends under deep supercooling conditions. Simulations of isothermal nucleation are performed for phase-separated blends with different degrees of incompatibility. In weakly segregated blends, slow and incompatible chains in crystallizable polymer domains can significantly hinder the crystal nucleation and growth. When a crystallizable polymer is blended with a more mobile species in interfacial regions, enhanced molecular mobility leads to the fast growth of crystalline order. However, the incubation time remains the same as that in pure samples. By inducing anisotropic alignment near the interfaces of strongly segregated blends, phase separation also promotes crystalline order to grow near interfaces between different polymer domains.

scholarly journals Numerical analysis of pulverized biomass combustion

2021 ◽  
Vol 321 ◽  
pp. 01001
Author(s):  
Cansu Deniz Canal ◽  
Erhan Böke ◽  
Ali Cemal Benim
Keyword(s):  
Gas Phase ◽  
Radiative Heat ◽  
Particle Dispersion ◽  
Single Step ◽  
Biomass Combustion ◽  
Phase Conversion ◽  
Two Phase ◽  
Dissipation Model ◽  
Turbulent Particle Dispersion ◽  
Step Mechanism

Combustion of pulverized biomass in a laboratory swirl burner is computationally investigated. The two-phase flow is modelled by an Eulerian-Lagrangian approach. The particle size distribution and turbulent particle dispersion are considered. The radiative heat transfer is modelled by the P1 method. For modelling turbulence, different RANS modelling approaches are applied. The pyrolysis of the solid fuel is modelled by a single step mechanism. For the combustion of the volatiles a two-step reaction mechanism is applied. The gas-phase conversion rate is modelled by the Eddy Dissipation Model, combined with kinetics control. The results are compared with measurements.

scholarly journals Impurities and Homogeneous Crystal Nucleation in Aqueous Solutions - An Overview

2019 ◽  
Vol 16 (3) ◽  
pp. 198-208
Author(s):  
C. K. Mahadevan
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Research Group ◽  
Present Author ◽  
Crystal Nucleation ◽  
Nucleation Process ◽  
Nucleation Parameters ◽  
The Past ◽  
Homogeneous Crystal ◽  
Made In

Nucleation process is the most important stage in the formation of a crystal and has attracted the attention of researchers due to its importance in many technological and biological contexts. As the presence of impurities affects the nucleation process significantly, several studies have been made in the past to understand it. In this article is presented an overview of various studies made to understand the effect of soluble impurities on the crystal nucleation parameters of certain important materials in aqueous solution focusing the results reported by the research group of the present author.

Thermodynamics and kinetics of homogeneous crystal nucleation studied by computer simulation

2000 ◽  
Vol 62 (22) ◽  
pp. 14690-14702 ◽  
Author(s):  
H. E. A. Huitema ◽  
J. P. van der Eerden ◽  
J. J. M. Janssen ◽  
H. Human
Keyword(s):  
Computer Simulation ◽  
Crystal Nucleation ◽  
Thermodynamics And Kinetics ◽  
Homogeneous Crystal ◽  
Kinetics Of

Heterogeneous and homogeneous crystal nucleation in colloidal hard-sphere like microgels at low metastabilities

Soft Matter ◽  
2011 ◽  
Vol 7 (23) ◽  
pp. 11267 ◽  
Author(s):  
Markus Franke ◽  
Achim Lederer ◽  
Hans Joachim Schöpe
Keyword(s):  
Hard Sphere ◽  
Crystal Nucleation ◽  
Homogeneous Crystal

Nucleation and Glass Formation

1985 ◽  
Vol 57 ◽  
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.

Homogeneous crystal nucleation in binary metallic melts

1983 ◽  
Vol 31 (12) ◽  
pp. 2021-2027 ◽  
Author(s):  
C.V. Thompson ◽  
F. Spaepen
Keyword(s):  
Crystal Nucleation ◽  
Homogeneous Crystal ◽  
Metallic Melts
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