TY - JOUR
T1 - Sub-Tg enthalpy relaxation in an extremely unstable oxide glass and its implication for structural heterogeneity
AU - Zhang, Yanfei
AU - Hu, L.N.
AU - Liu, S.J.
AU - Zhu, C.F.
AU - Yue, Yuanzheng
PY - 2013
Y1 - 2013
N2 - We study the sub-Tg relaxation in an extremely unstable glass former, i.e., 65SiO2-35Al2O3, and its relation to structural heterogeneity (e.g., structurally ordered domains in glass matrix). This is done by hyperquenching (~106 K/s) the liquid, then annealing the hyperquenched glass below Tg and subsequently scanning the annealed hyperquenched glass in a differential scanning calorimeter. The results show that structural ordering can take place even below Tg. An endothermic pre-peak is observed when the hyperquenched sample is annealed at 0.75Tg for sufficiently long time, which is, however, much weaker compared to that of stable glass formers subjected to same annealing conditions. We also investigate the effect of the sub-Tg annealing on crystallization above Tg. The results imply that some structurally ordered domains exist already in the liquid state. The ordered domains lower the activation energy for further structural ordering during the sub-Tg annealing, and thereby lowers the activation energy for crystal growth above Tg.
AB - We study the sub-Tg relaxation in an extremely unstable glass former, i.e., 65SiO2-35Al2O3, and its relation to structural heterogeneity (e.g., structurally ordered domains in glass matrix). This is done by hyperquenching (~106 K/s) the liquid, then annealing the hyperquenched glass below Tg and subsequently scanning the annealed hyperquenched glass in a differential scanning calorimeter. The results show that structural ordering can take place even below Tg. An endothermic pre-peak is observed when the hyperquenched sample is annealed at 0.75Tg for sufficiently long time, which is, however, much weaker compared to that of stable glass formers subjected to same annealing conditions. We also investigate the effect of the sub-Tg annealing on crystallization above Tg. The results imply that some structurally ordered domains exist already in the liquid state. The ordered domains lower the activation energy for further structural ordering during the sub-Tg annealing, and thereby lowers the activation energy for crystal growth above Tg.
U2 - 10.1016/j.jnoncrysol.2013.09.018
DO - 10.1016/j.jnoncrysol.2013.09.018
M3 - Journal article
SN - 0022-3093
VL - 381
SP - 23
EP - 28
JO - Journal of Non-Crystalline Solids
JF - Journal of Non-Crystalline Solids
ER -