15 October 2013 Characterization of structural relaxation in As2Se3 for analysis of lens shape change in glass press mold cooling and post-process annealing
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Proceedings Volume 8884, Optifab 2013; 888416 (2013) https://doi.org/10.1117/12.2029283
Event: SPIE Optifab, 2013, Rochester, New York, United States
Abstract
This study explores the structural relaxation behavior of As2Se3 by thermo mechanical analysis in order to characterize and eventually predict volume change in As2Se3 upon relaxation during cooling after precision glass molding (PGM) and annealing. A vertical beam of As2Se3 was placed in a thermo mechanical analyzer (TMA) and fully relaxed at a given temperature. The temperature was then quickly changed a given amount and the 1-D relaxation of the beam was measured until it reached equilibrium at the new temperature. The resultant curve was then fit with a Prony series which captured the relaxation data. The mathematical representation of the relaxation is then analyzed as a function of time, temperature, and quench rate and can be used to predict one dimensional (1-D) length change upon relaxation. A maximum of three terms is needed to describe the relaxation behavior and that number declines with an increase in temperature. This decay of the number of Prony terms needed to describe relaxation points to a structure that relaxes with less complexity as it approaches Tg. These trends can be converted to 3-D due to the amorphous and therefore typically isotropic nature of As2Se3 glass. This volume change information as a function of vital processing parameters can then be used to predict the change in shape of a work piece during cooling or post process annealing within a precision molding cycle. The mathematical representation of volume relaxation can then be applied to finite element models (FEM) of As2Se3 lenses or other optical elements.
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Erick Koontz, Erick Koontz, Peter Wachtel, Peter Wachtel, J. David Musgraves, J. David Musgraves, Kathleen Richardson, Kathleen Richardson, } "Characterization of structural relaxation in As2Se3 for analysis of lens shape change in glass press mold cooling and post-process annealing", Proc. SPIE 8884, Optifab 2013, 888416 (15 October 2013); doi: 10.1117/12.2029283; https://doi.org/10.1117/12.2029283
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