INTERMEDIATE PHASES, REVERSIBILITY WINDOWS, STRESS-FREE AND NON-AGING NETWORKS, AND STRONG LIQUIDS

摘要

Network glasses usually display glass transitions that are hysteretic, i.e., a second scan across a glass transition endotherm usually does not replicate the first one. But in recent years, examination of glass transition endotherms of several inorganic systems [1-4] reveal a different pattern: one observes compositional windows across which glass transitions become almost completely non-hysteretic. Specifically, the non-reversing enthalpy (.Hnr) associated with the glass transition (Tg) accessed from modulated Differential Scanning Calorimetry is found to nearly vanish [1-4]. These compositional windows, also called reversibility windows, usually occur [5] in the 2.29 < r < 2.52 range, where r represents the mean coordination number, a measure of network connectivity