Physical ageing of silicate glasses at room temperature : The choice of quantitative characteristics of the process and the ranking of glasses by their tendency to ageing

• Published in: Glass physics and chemistry Vol. 27; no. 3; pp. 214 - 227
• Main Author: NEMILOV, S. V
• Format: Journal Article
• Language: English
• Published: Moscow Kluwer/Plenum 01-05-2001; New York, NY Nauka/Interperiodica; Springer Nature B.V
• Subjects: Age; Aging; Channels; Completeness; Glass; Mathematical models; Ranking; Silicates; Studies
• ISSN: 1087-6596; 1608-313X
• DOI: 10.1023/A:1011336216128

Practical aspects of the model proposed earlier that treats the ageing of glasses as a complex relaxation process developing through several independent channels are discussed. The experimentally obtained or estimated parameters characterizing five channels are considered. A simplified technique for calculating the index of glass ageing completeness over any period (up to 50 years) and the ageing rate at any age on the basis of the temperature corresponding to a viscosity of 10^sup 13.5^P is proposed. It is revealed that the proposed model possesses the following property: the completeness of ageing of glass at any age is determined by its ageing rate at an age of about one year. Forty two optical and other glasses are ranked in order of their tendency to ageing according to the above parameters. The ranking of the known thermometric glasses corresponds to the tendency of these glasses to ageing in thermometric practice. The data on the glass ageing, which were obtained from measurements of refractive indices and scale lengths, are compared. It is shown that artificial ageing can proceed in the course of fine annealing of optical glasses. Consideration is given to a number of conditions whose fulfillment in the experiments on the glass ageing can favor successful solution of the problem. It is demonstrated that there are parallels between the model interpretation of glass ageing and the modern description of ageing processes in biological populations.[PUBLICATION ABSTRACT]