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Numerical Model for Isothermal and Non-Isothermal Crystallization of Liquids and GlassesA new numerical model of isothermal and non-isothermal first order phase transformations, such as the crystallization of liquids and glasses, is presented. This model computes directly the volume fraction transformed, taking into account time-dependent nucleation rates and cluster-size-dependent growth velocities. The model is applied to the crystallization of lithium disilicate glass, using the appropriate kinetic and thermodynamic parameters. The model is used (1) to determine the validity of common methods for computing the volume fraction transformed as a function of time in isothermal experiments when a time-dependent nucleation rate is expected, (2) to simulate non-isothermal differential scanning calorimetry (DSC) studies of glass devitrification as a function of scan rate, and (3) to compute the effect of preannealing on the DSC peak parameters. A novel behavior of the nucleation rate with scan rate is predicted, arising because the relaxation of the cluster distribution cannot be described by a single relaxation time. Comparisons of the calculations with experimental data on this glass demonstrate the validity of the model.
Document ID
19970016855
Acquisition Source
Marshall Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Kelton, K. F.
(Washington Univ. Saint Louis, MO United States)
Date Acquired
August 17, 2013
Publication Date
June 16, 1993
Publication Information
Publication: Journal of Non-Crystalline Solids
Publisher: Elsevier Science Publishers
Issue: 163
ISSN: 0022-3093
Subject Category
Solid-State Physics
Report/Patent Number
NAS 1.26:203527
NASA-CR-203527
Accession Number
97N71553
Funding Number(s)
CONTRACT_GRANT: NAG8-873
Distribution Limits
Public
Copyright
Public Use Permitted.
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