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Abstract
Based on the concept of polymeric–polymorphous structure of glass and glass-forming liquid experimental data have been analyzed revealing the nature of glass aging. We show that the glass forming substance is a copolymer consisting of structural nano-fragments (polymorphoids) in different polymorphous modifications (PM) of the material having no translational symmetry (long-range order). The study revealed that the process and degree of glass aging influences the properties of glasses, including a change in enthalpy, manifested in the exothermic and endothermic effects observed in thermograms of differential scanning calorimetry of heated and cooled glasses. We have shown that the physicochemical essence of aging is the transformation of polymorphoids from high-temperature PM (HTPM) to low-temperature PM (LTPM) which results, under certain conditions, in LTPM crystallization.
Highlights
Based on the concept of polymeric−polymorphous structure of glass and glassforming liquid (Minaev, 1987) experimental data have been analyzed revealing the nature of glass aging
We show that the glass forming substance is a copolymer consisting of structural nano− fragments in different polymorphous modifications (PM) of the material having no translational symmetry
The study revealed that the process and degree of glass aging influences the properties of glasses, including a change in enthalpy, manifested in the exothermic and endothermic effects observed in thermograms of differential scanning calorimetry of heated and cooled glasses
Summary
Установлено, что физико−химической сущностью процесса старения стекла является процесс превращения полиморфоидов высокотемпературной ПМ (ВТПМ) в полиморфоиды низкотемпературной ПМ (НТПМ), заканчивающийся при определенных условиях кристаллизацией НТПМ. Сополимеризация полиморфоидов ВТПМ и НТПМ при охлаждении и релаксации расплава является основой процесса стеклования, препятствующей кристаллизации охлаждаемого расплава. Процесс релаксации ниже «Tg» (так будем обозначать далее современную Tg, или, точнее, Tw—rev) ассоциируется обычно с β−релаксацией, или вторичным стеклованием, при котором вязкость охлаждаемого вещества изменяется от ~1012,3 до ~1015—16 Па ⋅ с [20]
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