Abstract:

This paper describes recent advances in the study of relaxation in hyperquenched glasses (HQGs), i.e., glasses far from equilibrium. The new approaches for determination of the fictive temperature and the cooling rate of the HQGsare introduced and two examples are presented. The hyperquenching-annealing-calorimetric scan (HAC) strategy is used to explore the energetic and structural heterogeneities in glasses. The occurrence of a pre-endotherm is observed when a properly annealed HQG undergoes a calorimetric upscan. The pre-endotherm is followed by an exotherm due to the release of the excess energy stored during hyperquenching, and subsequently by the endothermic glass transition. Several striking features of the pre-endotherm are demonstrated and compared with those of the glass transition. This comparison is crucial for understanding the non-linearity and nonexponentiality of the relaxation in glass. The data obtained from the HACexperiments on silicate glasses are used to clarify the glass transition of water. Fundamental differences in relaxation behavior between a strong and a fragile HQG are found and analyzed in terms of their structural and energetic origins.The strong impact of the annealing degree on the vibrational density of states of HQGs are exhibited and discussed in terms of microstructure.

Key words: glass; relaxation; hyperquenching; annealing; calorimetry; heat capacity; Boson peak