scholarly journals Non-Isothermal Crystallisation Kinetics of Polypropylene at High Cooling Rates and Comparison to the Continuous Two-Domain pvT Model

Polymers ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1515
Author(s):  
Jonathan Alms ◽  
Christian Hopmann ◽  
Jian Wang ◽  
Tobias Hohlweck
Keyword(s):  
Injection Moulding ◽  
Polymer Processing ◽  
Nucleation And Growth ◽  
Growth Theory ◽  
Crystallisation Kinetics ◽  
Cooling Rates ◽  
Dsc Measurements ◽  
Wide Range ◽  
High Cooling Rates ◽  
Kinetics Of

The modelling of the correlation between pressure, specific volume and temperature (pvT) of polymers is highly important for applications in the polymer processing of semi-crystalline thermoplastics, especially in injection moulding. In injection moulding, the polymer experiences a wide range of cooling rates, for example, 60 °C/min near the centre of the part and up to 3000 °C/min near the mould walls. The cooling rate has a high influence on the pvT behaviour, as was shown in the continuous two-domain pvT model (CTD). This work examined the Hoffman–Lauritzen nucleation and growth theory used in the modified Hammami model for extremely high cooling rates (up to 300,000 °C/min) by means of Flash differential scanning calorimeter (DSC) measurements. The results were compared to those of the empirical continuous two-domain pvT model. It is shown that the Hammami model is not suitable to predict the crystallisation kinetics of polypropylene at cooling rates above 600 °C/min, but that the continuous two-domain pvT model is well able to predict crystallisation temperatures at high cooling rates.

Solidification Modeling of Bulk Amorphous Alloys

2003 ◽  
Vol 806 ◽  
Author(s):  
Sang Bok Lee ◽  
Nack J. Kim
Keyword(s):  
Heterogeneous Nucleation ◽  
Amorphous Alloys ◽  
Nucleation Theory ◽  
Cooling Rates ◽  
Continuous Cooling ◽  
Wide Range ◽  
Temperature Transformation ◽  
Transformation Diagrams ◽  
Experimental Values ◽  
Kinetics Of

ABSTRACTClassical heterogeneous nucleation theory coupled with DTA data has been used to closely estimate the crystallization behavior of continuously cooled bulk metallic glass (BMG) alloys. Continuous cooling transformation and time temperature transformation diagrams of three BMG alloys, Zr41.2Ti13.8Cu12.5Ni10Be22.5, Cu47Ti33Zr11Ni6Si1Sn2 and Mg65Cu25Y10 alloys, have been calculated. The critical cooling rates Rc of three alloys were calculated to be 1.7 K/s, 242 K/s and 36 K/s for Zr41.2Ti13.8Cu12.5Ni10Be22.5, Cu47Ti33Zr11Ni6Si1Sn2 and of Mg65Cu25Y10 alloys, respectively, which match well with the experimental values. We conclude that heterogeneous nucleation is more favorable than homogeneous nucleation for the formation of crystals during cooling of BMG alloy liquids. Our approach can be applied to the analyses of crystallization kinetics of BMG alloys with a wide range of critical cooling rates during continuous cooling as well as isothermal annealing.

Kinetics and Mechanisms of Formation of Al-Ni Intermetallics

1986 ◽  
Vol 81 ◽  
Author(s):  
J. A. Patchett ◽  
G. J. Abbaschian
Keyword(s):  
Cooling Rate ◽  
Nucleation And Growth ◽  
Primary Phase ◽  
Peritectic Temperature ◽  
Cooling Rates ◽  
Fault Density ◽  
Metastable Extension ◽  
Mechanisms Of Formation ◽  
Free Growth ◽  
Kinetics Of

AbstractThe effects of cooling rate and composition on the nucleation and growth kinetics of NiAl, Ni2Al3, and NiAl3 intermetallics were studied for alloys containing 25 and 31.5 ht.% Ni. Fgr the former composition, the peritectic regction Ni Al + Liquid → NiAl3 was studied over cooling rates from 20 to 105 K/s. For the latter composhtion, the reaction NiAl + Liquid → Ni2Al3 was studied at cooling rates ranging form 10 to 600 K/sec. The amounis of constituent phases are shown to depend on the cooling rate, and for the peritectic phases, on the surface area of the primary phase. The nucleation of Ni2Al3 and NiAl3, and the ordering of the aluminum-rich NiAl were also examines uding trans ission electron microscopy. Cooling the NiAl + liquid below the peritectic temperature results in a metastable extension of NiAl with a high dislocation and stacking fault density, followed by the epitaxial nucleation and almost dislocation-free growth of Ni2Al3 In contrast, the nucleation of the NiAl3 on Ni2Al3 occurs directly witgoud the formationof an intermediate region.

Isothermal and non-isothermal crystallization kinetics and predictive modeling in the solidification of poly(cyclohexylene dimethylene cyclohexanedicarboxylate) melt

2016 ◽  
Vol 49 (2) ◽  
pp. 132-156 ◽  
Author(s):  
Ying-Guo Zhou ◽  
Wen-Bin Wu ◽  
Gui-Yun Lu ◽  
Jun Zou
Keyword(s):  
Activation Energy ◽  
Crystallization Kinetics ◽  
Isothermal Crystallization ◽  
Avrami Equation ◽  
Melt Crystallization ◽  
Crystallization Activation Energy ◽  
Cooling Rates ◽  
Isothermal Crystallization Kinetics ◽  
Wide Range ◽  
Kinetics Of

Isothermal and non-isothermal crystallization kinetics of polycyclohexylene dimethylene cyclohexanedicarboxylate (PCCE) were investigated via differential scanning calorimetry (DSC). Isothermal melt crystallization kinetics were analyzed using the traditional Avrami equation. Non-isothermal melt crystallization kinetics data obtained from DSC were analyzed using the extended Avrami relation and a combination of the Avrami equation and the Ozawa relationship. The glass transition temperature, equilibrium melting point, isothermal crystallization activation energy, and non-isothermal crystallization activation energy were determined. Furthermore, a predictive method based on the Nakamura model was proposed and was used to describe the non-isothermal crystallization kinetics based on the isothermal experimental data. The results suggested that the original Nakamura equation was not successful in describing the non-isothermal crystallization of PCCE over a wide range of cooling rates. It was found that the non-isothermal crystallization kinetics of PCCE, over a wide range of cooling rates, could best be described by modifying the differential Nakamura equation to include a varied Avrami index.

In situ observation of the martensitic transformation in (Mg,Y)-PSZ

1986 ◽  
Vol 44 ◽  
pp. 500-501
Author(s):  
R-R. Lee
Keyword(s):  
Martensitic Transformation ◽  
High Strength ◽  
Nucleation And Growth ◽  
In Situ Observation ◽  
Considerable Potential ◽  
Transmission Electron ◽  
Structural Applications ◽  
Applied Stresses ◽  
Kinetics Of

Partially-stabilized ZrO2 (PSZ) ceramics have considerable potential for advanced structural applications because of their high strength and toughness. These properties derive from small tetragonal ZrO2 (t-ZrO2) precipitates in a cubic (c) ZrO2 matrix, which transform martensitically to monoclinic (m) symmetry under applied stresses. The kinetics of the martensitic transformation is believed to be nucleation controlled and the nucleation is always stress induced. In situ observation of the martensitic transformation using transmission electron microscopy provides considerable information about the nucleation and growth aspects of the transformation.

Scintigraphic studies in rats. Kinetics of insulin analogues covering wide range of receptor affinities

Diabetes ◽  
1991 ◽  
Vol 40 (5) ◽  
pp. 628-632 ◽  
Author(s):  
I. Jensen ◽  
V. Kruse ◽  
U. D. Larsen
Keyword(s):  
Insulin Analogues ◽  
Wide Range ◽  
Kinetics Of

In situ quantification of crystallisation kinetics of plagioclase and clinopyroxene in basaltic magma: Implications for lava flow

2021 ◽  
Vol 568 ◽  
pp. 117016
Author(s):  
Nolwenn Le Gall ◽  
Fabio Arzilli ◽  
Giuseppe La Spina ◽  
Margherita Polacci ◽  
Biao Cai ◽  
...  
Keyword(s):  
Lava Flow ◽  
Basaltic Magma ◽  
Crystallisation Kinetics ◽  
Kinetics Of

Inhomogeneous Swelling Near Grain Boundaries in Irradiated Materials: Cavity Nucleation and Growth Saturation Effects

2000 ◽  
Vol 650 ◽  
Author(s):  
S. L. Dudarev
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Nucleation And Growth ◽  
Homogeneous Distribution ◽  
Rate Theory ◽  
Diffusional Growth ◽  
Standard Rate ◽  
Saturation Effects ◽  
Kinetics Of ◽  
Cascade Damage

ABSTRACTThe effect of inhomogeneous nucleation and growth of cavities near grain boundaries illustrates the failure of the standard rate theory to describe the kinetics of phase transformations in irradiated materials under cascade damage conditions. The enhanced swelling observed near grain boundaries is believed to result from the competition between the diffusional growth of cavities and their shrinkage due to the interaction with mobile interstitial clusters. Swelling rates associated with the two processes behave in a radically different way as a function of the size of growing cavities. For a spatially homogeneous distribution of cavities this gives rise to the saturation of swelling in the limit of large irradiation doses.We investigate the evolution of the population of cavities nucleating and growing near a planar grain boundary. We show that a cavity growing near the boundary is able to reach a size that is substantially larger than the size of a cavity growing in the interior region of the grain. For a planar grain boundary the magnitude of swelling at maximum is found to be up to eight times higher than the magnitude of swelling in the grain interior.

scholarly journals Combining experimental and simulation data of molecular processes via augmented Markov models

2017 ◽  
Vol 114 (31) ◽  
pp. 8265-8270 ◽  
Author(s):  
Simon Olsson ◽  
Hao Wu ◽  
Fabian Paul ◽  
Cecilia Clementi ◽  
Frank Noé
Keyword(s):  
Force Field ◽  
Structural Changes ◽  
Markov Models ◽  
Force Fields ◽  
Divide And Conquer ◽  
Simulation Data ◽  
Wide Range ◽  
Simulation And Experiment ◽  
Kinetics Of

Accurate mechanistic description of structural changes in biomolecules is an increasingly important topic in structural and chemical biology. Markov models have emerged as a powerful way to approximate the molecular kinetics of large biomolecules while keeping full structural resolution in a divide-and-conquer fashion. However, the accuracy of these models is limited by that of the force fields used to generate the underlying molecular dynamics (MD) simulation data. Whereas the quality of classical MD force fields has improved significantly in recent years, remaining errors in the Boltzmann weights are still on the order of a few kT, which may lead to significant discrepancies when comparing to experimentally measured rates or state populations. Here we take the view that simulations using a sufficiently good force-field sample conformations that are valid but have inaccurate weights, yet these weights may be made accurate by incorporating experimental data a posteriori. To do so, we propose augmented Markov models (AMMs), an approach that combines concepts from probability theory and information theory to consistently treat systematic force-field error and statistical errors in simulation and experiment. Our results demonstrate that AMMs can reconcile conflicting results for protein mechanisms obtained by different force fields and correct for a wide range of stationary and dynamical observables even when only equilibrium measurements are incorporated into the estimation process. This approach constitutes a unique avenue to combine experiment and computation into integrative models of biomolecular structure and dynamics.

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