Calculation of Temperature Dependences of the Viscosity and Volume Relaxation Time for Oxide Glass-Forming Melts from Chemical Composition and Dilatometric Glass Transition Temperature |
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Authors: | A I Priven |
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Affiliation: | (1) OOO Scite, Srednegavanskii pr. 1, St. Petersburg, 199106, Russia |
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Abstract: | The relaxation parameter K
sthat is equal to the ratio of the viscosity to the Kohlrausch volume relaxation time
s
is analyzed. It is shown that this parameter can be evaluated from the temperature T
13(corresponding to a viscosity of 1013P) and the glass transition temperature T
8
+determined from the dilatometric heating curve. The maximum error of the estimate with due regard for experimental errors is equal to ±(0.4–0.5)logK
sfor strong glasses and ±(0.6–0.8)logK
sfor fragile glasses, which, in both cases, corresponds to a change in the relaxation times with a change in the temperature by ±(8–10) K. It is revealed that the viscosity, the Kohlrausch volume relaxation time
s
, and the shear modulus Gof glass-forming materials in silicate, borate, and germanate systems satisfy the relationship log(
s
G/) 1. The procedure for calculating the temperature dependences of the viscosity and the relaxation times in the glass transition range from the chemical composition and the T
8
+temperature for glass-forming melts in the above systems is proposed. The root-mean-square deviations between the calculated and experimental temperatures T
11and T
13are equal to ±(6–8) K for all the studied (silicate, borate, germanate, and mixed) oxide glass-forming systems. The proposed relationships can be useful for evaluating the boundaries of the annealing range and changes in the properties and their temperature coefficients upon cooling of glass-forming melts. |
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Keywords: | |
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