This work investigated the response of Cu46Zr42Al7Y5 glass ribbons to both dynamic and static heating using differential scanning calorimeter （DSC）. The DSC curve manifests three exothermic responses to dynamic heat...This work investigated the response of Cu46Zr42Al7Y5 glass ribbons to both dynamic and static heating using differential scanning calorimeter （DSC）. The DSC curve manifests three exothermic responses to dynamic heating, among which the first and the third one are the signatures of the normal sub-Tg （Tg, glass transition temperature） relaxation and the crystallization process, respectively. The second one is attributed to a partial overlap between the endothermic response to the glass transition and the exothermic response to the formation of ordered clusters. The cluster ordering, which begins at the final stage of glass transition, has been verified by the differences in the activation energy of the sub-Tg relax- ation, the cluster ordering and primary crystallization for both the as-spun and annealed ribbons. The cluster ordering could be driven by the large difference between the Zr-Y mixing enthalpy and the Al-Y （or Cu-Y） mixing enthalpy. The findings contribute to distinguishing between phase separation and clusters motion scenarios.展开更多
When a liquid is supercooled,its structural equilibration timeτeqincreases sharply approaching the glass transition temperature Tg,below which it is kinetically arrested in the out of equilibrium glassy state.Upon an...When a liquid is supercooled,its structural equilibration timeτeqincreases sharply approaching the glass transition temperature Tg,below which it is kinetically arrested in the out of equilibrium glassy state.Upon annealing below Tg,such glassy state relaxes toward the equilibrium state.There is growing evidence that such relaxation process is quite complex,influenced by the complexity of the potential energy landscape.Here we report the observation of a hierarchical aging pathway in the process of the glass-to-supercooled liquid transition in various molecular glass forming systems.Differential scanning calorimetry reveals that the glassy state upon annealing below Tgfirstly enters a transient metastable supercooled liquid state with slightly higher enthalpies than that of the equilibrium supercooled liquid state when extrapolated to below Tg.This observation is also confirmed by structural measurements via Raman scattering.The dynamics of the transient metastable-to-stable supercooled liquid transition exhibits characteristics of thermodynamic transition at spinodal temperature Tspslightly above Tg,leading to anomalous behaviors such as the appearance of a transition-like behavior in the plot of fragility measurements.These observations imply that the free energy landscape of the supercooled liquid develops complexity with qualitative changes approaching Tgand could have strong influence on the process of the glass transition.展开更多
基金supported by the National Natural Science Foundation of China(5117109051571131)the Fundamental Research Funds of Shandong University(2014YQ008)
文摘This work investigated the response of Cu46Zr42Al7Y5 glass ribbons to both dynamic and static heating using differential scanning calorimeter （DSC）. The DSC curve manifests three exothermic responses to dynamic heating, among which the first and the third one are the signatures of the normal sub-Tg （Tg, glass transition temperature） relaxation and the crystallization process, respectively. The second one is attributed to a partial overlap between the endothermic response to the glass transition and the exothermic response to the formation of ordered clusters. The cluster ordering, which begins at the final stage of glass transition, has been verified by the differences in the activation energy of the sub-Tg relax- ation, the cluster ordering and primary crystallization for both the as-spun and annealed ribbons. The cluster ordering could be driven by the large difference between the Zr-Y mixing enthalpy and the Al-Y （or Cu-Y） mixing enthalpy. The findings contribute to distinguishing between phase separation and clusters motion scenarios.
基金supported by the National Basic Research Program of China (2015CB856801)
文摘When a liquid is supercooled,its structural equilibration timeτeqincreases sharply approaching the glass transition temperature Tg,below which it is kinetically arrested in the out of equilibrium glassy state.Upon annealing below Tg,such glassy state relaxes toward the equilibrium state.There is growing evidence that such relaxation process is quite complex,influenced by the complexity of the potential energy landscape.Here we report the observation of a hierarchical aging pathway in the process of the glass-to-supercooled liquid transition in various molecular glass forming systems.Differential scanning calorimetry reveals that the glassy state upon annealing below Tgfirstly enters a transient metastable supercooled liquid state with slightly higher enthalpies than that of the equilibrium supercooled liquid state when extrapolated to below Tg.This observation is also confirmed by structural measurements via Raman scattering.The dynamics of the transient metastable-to-stable supercooled liquid transition exhibits characteristics of thermodynamic transition at spinodal temperature Tspslightly above Tg,leading to anomalous behaviors such as the appearance of a transition-like behavior in the plot of fragility measurements.These observations imply that the free energy landscape of the supercooled liquid develops complexity with qualitative changes approaching Tgand could have strong influence on the process of the glass transition.
