Journal ArticleDOI
On the Relative Roles of Free Volume and Activation Energy in the Viscosity of Liquids
P. B. Macedo,T. A. Litovitz +1 more
TLDR
In this article, the rate theory has been reformulated using the Cohen and Turnbull expression for the probability of finding a vacant site and yields an equation of the form η=A0exp[Ev*/RT+γV0/Vf].Abstract:
The rate‐theory approach of Eyring and the free‐volume theory of Cohen and Turnbull for liquid viscosities have been reconsidered. The rate theory has been reformulated using the Cohen and Turnbull expression for the probability of finding a vacant site and yields an equation of the form η=A0exp[Ev*/RT+γV0/Vf]. This result has been applied to many liquids ranging from fused silica to liquid argon and including polyatomic van der Waals as well as hydrogen‐bonded liquids.Consistent fits to both temperature and pressure dependence of viscosity were obtained. A significant conclusion is that the free volume of liquids is considerably higher than that suggested by the WLF and Cohen and Turnbull equations.read more
Citations
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Journal ArticleDOI
Characteristics and Significance of the Amorphous State in Pharmaceutical Systems
Bruno C. Hancock,George Zografi +1 more
TL;DR: The amorphous state is critical in determining the solid-state physical and chemical properties of many pharmaceutical dosage forms and some of the most common methods that can be used to measure them are described.
Journal ArticleDOI
Viscous Liquids and the Glass Transition: A Potential Energy Barrier Picture
TL;DR: In this article, a picture of the flow process in viscous liquids is proposed, in an attempt to answer certain questions about the molecular steps in flow either answered unsuccessfully or ignored by present theories.
Journal ArticleDOI
The elastic properties, elastic models and elastic perspectives of metallic glasses
TL;DR: In this article, a comprehensive review of the current state of the art of the study of elastic properties, the establishments of correlations between elastic moduli and properties/features, and the elastic models and elastic perspectives of metallic glasses is presented.
Journal ArticleDOI
Enthalpy relaxation and recovery in amorphous materials
TL;DR: The field of enthalpy relaxation is reviewed in this paper, where current phenomenologies for dealing with the non-linear and non-exponential character of relaxation are presented, and their successes and shortcomings are discussed.
Journal ArticleDOI
Liquid-glass transition, a free-volume approach
Morrel H. Cohen,Gary S. Grest +1 more
TL;DR: In this paper, a theory of the underlying metastable phase, the amorphous phase, is developed, which is useful for describing the behavior of the viscosity of dense liquids and glasses.
References
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Journal ArticleDOI
The Temperature Dependence of Relaxation Mechanisms in Amorphous Polymers and Other Glass-Forming Liquids
Journal ArticleDOI
Analysis of recent measurements of the viscosity of glasses
TL;DR: In this article, the authors compared the results given by English with those of Washburn, Shelton and Libman, indicating a discrepancy in the absolute values of log10 viscosity amounting to 0.6.
Journal ArticleDOI
Molecular Transport in Liquids and Glasses
Morrel H. Cohen,David Turnbull +1 more
TL;DR: In this paper, the authors derived a relation between the diffusion constant D in a liquid of hard spheres and the free volume vf, which is based on the concept that statistical redistribution of free volume occasionally opens up voids large enough for diffusive displacement.
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