Glass formation, crystallization kinetics, and structural relaxation in fragile glass forming liquids
Abstract
This thesis deals with several key aspects of the subject of glass formation with special emphasis on the process of nucleation and growth of crystals from supercooled liquids, the avoidance of which is basic to vitrification. In an initial Chapter we review the field, laying out the basic ideas on time scale relationships, nucleation theory, glass transition and the classification of liquids and, finally, the relaxation processes which are internal to the liquid phase and which determine the details of the glass transition, and phenomena such as annealing and aging which are intimately related to it. Chapter two is devoted to the study of crystallization of liquids. It describes the basic techniques, developed in this laboratory, for the study of nucleation and growth, and applies it to several cases of special interest. This Chapter reports the first study of nucleation kinetics in the model ionic glass-forming system: Ca(NO$\sb3)\sb{2-}$ KNO$\sb3$ which has been used in so many basic studies of supercooled liquid dynamics in recent years. It includes studies of the glycerol-water system which is basic to cryobiology, the glass-forming fluoride system which is a model for this class of high transparency vitreous fiber optic materials and the AgI-Agoxysalt system which is a model for vitreous superionic solid electrolytes. The common features are compared with those of previously studied classic oxide glass systems. Chapter three describes several studies of relaxation processes in the glass themselves. These comprise of (1) enthalpy relaxation studies in a superionic glass system which shows several unusual features, in particular an extreme in nonexponentiality of relaxation; (2) a mechanical relaxation study which confirms the extreme nonexponentiality observed in this system and (3) an electrical relaxation study which shows that the anomalies observed in (1) and (2) do not apply to the mobile species of the system. Finally in Chapter four we describe some subsidiary studies of different systems of special interest, focussed on simple cases of glass-formation involving elemental and simple molecular liquids.
Degree
Ph.D.
Advisors
Angell, Purdue University.
Subject Area
Chemistry
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