On the possibility of devitrification of ancient glass |
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Authors: | Erich Kny Gerhard Nauer |
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Institution: | Institute of Physical Chemistry, University of Vienna, A-1090 Vienna. Währingerstrasse 42, Austria |
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Abstract: | The question whether some crystallization will take place in old glass during long-time storage (up to 1000 years) at low temperatures well below Tg is considered theoretically. Evaluations for the systems Na2O · SiO2 and Li2O · 2SiO2 are carried out using the model of homogeneous and heterogeneous nucleation theory. For these systems a barely observable crystallized volume fraction will be reached at 300 K only after storage for astronomical periods (106 ? 1013 years), depending on the number of heterogeneities and the contact angle of heterogeneity. If the observed strong influence of H2O content in glass on crystallization is also taken into account, crystallization will not take place for at least 1000 years of storage at 300 K. This limiting value is close to archaeological periods and will therefore merit careful attention in further investigations. |
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