Quantitative understanding of the initial stage of liquid to crystalline or amorphous phase transitions

Abstract

<p>In 2005, Science magazine listed the “nature of a glassy substance” as one of the 125 most challenging scientific questions of the century. A quantitative understanding of the time-temperature transition (TTT) curve for critical nucleation of amorphous materials is crucial to answering this question. Despite extensive efforts over the past 70 years, a quantitative model for the TTT curve remains elusive due to a lack of understanding of physical properties such as the interfacial energy at the incubation time <i>t</i><sup>*</sup> for critical nucleation. In this study, a relationship between the critical nucleation viscosity and the interfacial energy as a function of <i>t</i><sup>*</sup> is established and a quantitative TTT model is developed. The model demonstrates excellent agreement with experimental TTT data for various amorphous materials. Most importantly, it allows the accurate and definitive determination of <i>T</i><sub>0</sub>, the true minimum crystallization temperature at the lower end-point of the TTT curve, as well as the temperature below which the amorphous liquid-to-solid state transition occurs. This offers an unambiguous answer to the nature of glassy substances: Above <i>T</i><sub>0</sub>, a liquid with constant amorphous structure relaxation; and below <i>T</i><sub>0</sub>, a solid with stable amorphous structure.</p>