Nature of the Relaxation Processes in the Supercooled Liquid and Glassy States of Some Carbohydrates

1995 ◽  
Vol 99 (32) ◽  
pp. 12349-12354 ◽  
Author(s):  
Gangasharan ◽  
S. S. N. Murthy
Keyword(s):  
Supercooled Liquid ◽  
Relaxation Processes

scholarly journals Effects of Glass Transition and Structural Relaxation on Crystal Nucleation: Theoretical Description and Model Analysis

Entropy ◽  
2020 ◽  
Vol 22 (10) ◽  
pp. 1098 ◽  
Author(s):  
Jürn W. P. Schmelzer ◽  
Timur V. Tropin ◽  
Vladimir M. Fokin ◽  
Alexander S. Abyzov ◽  
Edgar D. Zanotto
Keyword(s):  
Surface Tension ◽  
Structural Relaxation ◽  
Driving Force ◽  
Cluster Formation ◽  
Supercooled Liquid ◽  
Crystal Nucleation ◽  
Metastable Equilibrium ◽  
Theoretical Treatment ◽  
Relaxation Processes ◽  
Thermodynamic Driving Force

In the application of classical nucleation theory (CNT) and all other theoretical models of crystallization of liquids and glasses it is always assumed that nucleation proceeds only after the supercooled liquid or the glass have completed structural relaxation processes towards the metastable equilibrium state. Only employing such an assumption, the thermodynamic driving force of crystallization and the surface tension can be determined in the way it is commonly performed. The present paper is devoted to the theoretical treatment of a different situation, when nucleation proceeds concomitantly with structural relaxation. To treat the nucleation kinetics theoretically for such cases, we need adequate expressions for the thermodynamic driving force and the surface tension accounting for the contributions caused by the deviation of the supercooled liquid from metastable equilibrium. In the present paper, such relations are derived. They are expressed via deviations of structural order parameters from their equilibrium values. Relaxation processes result in changes of the structural order parameters with time. As a consequence, the thermodynamic driving force and surface tension, and basic characteristics of crystal nucleation, such as the work of critical cluster formation and the steady-state nucleation rate, also become time-dependent. We show that this scenario may be realized in the vicinity and below the glass transition temperature, and it may occur only if diffusion (controlling nucleation) and viscosity (controlling the alpha-relaxation process) in the liquid decouple. Analytical estimates are illustrated and confirmed by numerical computations for a model system. The theory is successfully applied to the interpretation of experimental data. Several further consequences of this newly developed theoretical treatment are discussed in detail. In line with our previous investigations, we reconfirm that only when the characteristic times of structural relaxation are of similar order of magnitude or longer than the characteristic times of crystal nucleation, elastic stresses evolving in nucleation may significantly affect this process. Advancing the methods of theoretical analysis of elastic stress effects on nucleation, for the first time expressions are derived for the dependence of the surface tension of critical crystallites on elastic stresses. As the result, a comprehensive theoretical description of crystal nucleation accounting appropriately for the effects of deviations of the liquid from the metastable states and of relaxation on crystal nucleation of glass-forming liquids, including the effect of simultaneous stress evolution and stress relaxation on nucleation, is now available. As one of its applications, this theoretical treatment provides a new tool for the explanation of the low-temperature anomaly in nucleation in silicate and polymer glasses (the so-called “breakdown” of CNT at temperatures below the temperature of the maximum steady-state nucleation rate). We show that this anomaly results from much more complex features of crystal nucleation in glasses caused by deviations from metastable equilibrium (resulting in changes of the thermodynamic driving force, the surface tension, and the work of critical cluster formation, in the necessity to account of structural relaxation and stress effects) than assumed so far. If these effects are properly accounted for, then CNT appropriately describes both the initial, the intermediate, and the final states of crystal nucleation.

Formation and evolution characteristics of bcc phase during isothermal relaxation processes of supercooled liquid and amorphous metal Pb

2011 ◽  
Vol 21 (3) ◽  
pp. 588-597 ◽  
Author(s):  
Li-li ZHOU ◽  
Rang-su LIU ◽  
Ze-an TIAN ◽  
Hai-rong LIU ◽  
Zhao-yang HOU ◽  
...  
Keyword(s):  
Supercooled Liquid ◽  
Amorphous Metal ◽  
Relaxation Processes ◽  
Evolution Characteristics ◽  
Formation And Evolution ◽  
Bcc Phase

An interpretation of the bifurcation of orientational relaxation processes in a supercooled liquid

1990 ◽  
Vol 93 (12) ◽  
pp. 8991-9001 ◽  
Author(s):  
Biman Bagchi ◽  
Amalendu Chandra ◽  
Stuart A. Rice
Keyword(s):  
Supercooled Liquid ◽  
Relaxation Processes ◽  
Orientational Relaxation

Volume and Enthalpy Relaxation in Bulk Metallic Glasses

2007 ◽  
Vol 1048 ◽  
Author(s):  
Osami Haruyama
Keyword(s):  
Relaxation Process ◽  
Metallic Glasses ◽  
Onset Time ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Enthalpy Relaxation ◽  
Relaxation Processes ◽  
Liquid Region ◽  
Volume Relaxation ◽  
Exponential Relaxation

AbstractVolume and enthalpy relaxation processes in a sub-Tg region were investigated by density and enthalpy experiments for bulk Pd-P based and Zr-based metallic glasses. Most of glasses except for a Pd40Ni40P20 glass exhibited a single relaxation process for both volume and enthalpy relaxations and the relaxation process was well described by a stretched exponential relaxation function, Φ(t)=exp{-(t/τ)β}, with a Kohlrausch index β less than 1. The as-quenched sample was pre-annealed in a supercooled liquid region to homogenize the density fluctuation quenched in an as-quenched state. Then the retardation of onset time of relaxation appeared in case of volume relaxation. The proportionality between enthalpy change ΔH and volume change Δv during relaxation was good for Pd42.5Cu30Ni7.5P20 glass within experimental error.

scholarly journals Effects of Glass Transition and Structural Relaxation on Crystal Nucleation: Theoretical Description and Model Analysis

2020 ◽  
Author(s):  
Juern W. P. Schmelzer ◽  
Timur V. Tropin ◽  
Vladimir M. Fokin ◽  
Alexander S. Abyzov ◽  
Edgar D. Zanotto
Keyword(s):  
Surface Tension ◽  
Structural Relaxation ◽  
Driving Force ◽  
Cluster Formation ◽  
Supercooled Liquid ◽  
Crystal Nucleation ◽  
Metastable Equilibrium ◽  
Theoretical Treatment ◽  
Relaxation Processes ◽  
Thermodynamic Driving Force

In the application of classical nucleation theory (CNT) and all other theoretical models of crystallization of liquids and glasses it is always assumed that nucleation proceeds only after the supercooled liquid or the glass have completed structural relaxation processes towards the metastable equilibrium state. Only employing such assumption, the thermodynamic driving force of crystallization and the surface tension can be determined in the way it is commonly performed. The present paper is devoted to the theoretical treatment of a different situation when nucleation proceeds concomitantly with structural relaxation. To treat the nucleation kinetics theoretically for such cases, we need adequate expressions for the thermodynamic driving force and the surface tension accounting for the contributions caused by the deviation of the supercooled liquid from metastable equilibrium. In the present paper, such relations are derived. They are expressed via deviations of structural order parameters from their equilibrium values. Relaxation processes result in changes of the structural order parameters with time. As a consequence, the thermodynamic driving force and surface tension, and basic characteristics of crystal nucleation, such as the work of critical cluster formation and the steady-state nucleation rate, also become time-dependent. We show that this scenario may be realized in the vicinity and below the glass transition temperature, and it may occur only if diffusion (controlling nucleation) and viscosity (controlling the alpha-relaxation process) in the liquid decouple. Analytical estimates are illustrated and confirmed by numerical computations for a model system. The theory is successfully applied to the interpretation of experimental data. Several further consequences of this newly developed theoretical treatment are discussed in detail. In line with our previous investigations, we reconfirm that only when the characteristic times of structural relaxation are of similar order of magnitude or longer than the characteristic times of crystal nucleation, elastic stresses evolving in nucleation may significantly affect this process. Completing the analysis of elastic stress effects, for the first time expressions are derived for the dependence of the surface tension of critical crystallites on elastic stresses. As the result, a comprehensive theoretical description of crystal nucleation accounting appropriately for the effects of deviations of the liquid from the metastable states and of relaxation on crystal nucleation of glass-forming liquids, including the effect of simultaneous stress evolution and stress relaxation on nucleation, is now available. As one if its applications, this theoretical treatment provides a new tool for the explanation of the low-temperature anomaly in nucleation in silicate and polymer glasses (the so-called \breakdown" of CNT at temperatures below the temperature of the maximum steady-state nucleation rate). We show that this anomaly results from much more complex features of crystal nucleation in glasses caused by deviations from metastable equilibrium (resulting in changes of the thermodynamic driving force, the surface tension, and the work of critical cluster formation, in the necessity to account of structural relaxation and stress effects) than assumed so far.

Simulation Study of Dynamic Features during the Isothermal Relaxation Processes in Supercooled Liquid and Glassy Pb

2013 ◽  
Vol 873 ◽  
pp. 110-113
Author(s):  
Li Li Zhou ◽  
Xuan Zheng ◽  
Hui Luo
Keyword(s):  
Diffusion Constant ◽  
Mean Square Displacement ◽  
Supercooled Liquid ◽  
Experimental Result ◽  
Relaxation Processes ◽  
Mean Square ◽  
Dynamic Features ◽  
Structure Rearrangement ◽  
Non Gaussian ◽  
Dynamics Simulations

The molecular dynamics simulations on the isothermal relaxation properties of supercooled liquid and glassy Pb have been performed. The calculated diffusion constant of Pb is well agreed with the experimental result. Results indicate that the relaxations of supercooled and glassy Pb present more and more pronounced heterogeneity with decreasing temperature. The appearance of the second plateau of mean square displacement (MSD) and the non-zero plateau of Non-Gaussian parameter (NGP) is corresponding to the rest of structure rearrangement.

Dynamics of supercooled liquid and plastic crystalline ethanol: Dielectric relaxation and AC nanocalorimetry distinguish structural α- and Debye relaxation processes

2017 ◽  
Vol 147 (1) ◽  
pp. 014502 ◽  
Author(s):  
Y. Z. Chua ◽  
A. R. Young-Gonzales ◽  
R. Richert ◽  
M. D. Ediger ◽  
C. Schick
Keyword(s):  
Dielectric Relaxation ◽  
Supercooled Liquid ◽  
Relaxation Processes ◽  
Debye Relaxation

Hot Luminescence and Relaxation Processes in the Luminescence Centers of Crystals

1976 ◽  
Vol 120 (11) ◽  
pp. 502 ◽  
Author(s):  
K.K. Rebane ◽  
P.M. Saari
Keyword(s):  
Relaxation Processes ◽  
Luminescence Centers

Activation energy of relaxation processes in chalcogenide glasses

2013 ◽  
Vol 34 (0) ◽  
pp. 59-63
Author(s):  
А. А. Горват ◽  
В. М. Кришеник ◽  
А. Е. Кріштофорій ◽  
В. В. Мінькович ◽  
О. А. Молнар
Keyword(s):  
Activation Energy ◽  
Chalcogenide Glasses ◽  
Relaxation Processes
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