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Physical aging of heavy metal fluoride glasses—sub‐ T g enthalpy relaxation in a ZrF 4 ‐BaF 2 ‐LaF 3 ‐AlF 3 glass
Author(s) -
Moynihan C. T.,
Bruce A. J.,
Gavin D. L.,
Loehr S. R.,
Opalka S. M.,
Drexhage M. G.
Publication year - 1984
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760241407
Subject(s) - enthalpy , materials science , annealing (glass) , differential scanning calorimetry , relaxation (psychology) , thermodynamics , glass transition , calorimetry , fluoride , analytical chemistry (journal) , chemistry , metallurgy , composite material , inorganic chemistry , polymer , physics , chromatography , psychology , social psychology
The enthalpy changes during structural relaxation or physical aging of a 58ZrF 4 ‐33BaF 2 ‐5LaF 3 ‐4AlF 3 (ZBLA) glass during annealing well below the glass‐transition temperature have been studied using differential‐scanning calorimetry at several sub‐ T g temperatures. Substantial relaxation within the course of several hours was detected at temperatures as low as sixty degrees below T g (585K). The relaxation process is extremely nonlinear and self‐retarding. The time dependence of the enthalpy during the initial stages of annealing was modeled approximately using the Narayanaswamy‐Tool approach. The structural‐relaxation parameters obtained from this fit were used to predict rates of physical aging for rapidly cooled ZBLA glass at temperatures close to ambient.