Abnormal relaxation kinetics in D-mannitol glass confined by nanoporous alumina
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ly 2020 Vol. 63 No. 7: 276113 https://doi.org/10.1007/s11433-020-1535-3
Abnormal relaxation kinetics in D-mannitol glass confined by nanoporous alumina YaRu Cao
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, LiJian Song , Ao Li , JunTao Huo , FuShan Li , Wei Xu 2,3* Jun-Qiang Wang
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College of Materials Science and Chemical Engineering, Ningbo University, Ningbo 315211, China; CAS Key Laboratory of Magnetic Materials and Devices, Zhejiang Province Key Laboratory of Magnetic Materials and Application 3
Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China; Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Science, Beijing 100049, China; 4 School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China Received January 1, 2020; accepted February 24, 2020; published online April 17, 2020
The relaxation kinetics and phase transformations of the confined D-mannitol (DM) in nanoporous alumina are studied in-situ using a high-precision nano-calorimeter. We find that the crystallization behavior can be suppressed when it is confined in nanopores smaller than 50 nm. The confined DM glass has a much smaller fragility (~76) than free DM glass (~125), confirming the enhanced glass-forming ability. It is intriguing that during isothermal annealing both the confined and free DM glasses relaxation kinetics experience two relaxation stages that have distinct activation energies. The relaxation activation energy of the confined glass is about 25%-29% smaller than the free glass, which is attributed to the reduced dimensionality. The abnormal kinetics observed in the confined DM glass open a new avenue for preparing stable glasses. D-mannitol glass, confinement, relaxation, crystallization PACS number(s): 61.43.Fs, 61.20.Lc, 64.70.Pf Citation:
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Y. R. Cao, L. J. Song, A. Li, J. T. Huo, F. S. Li, W. Xu, and J.-Q. Wang, Abnormal relaxation kinetics in D-mannitol glass confined by nanoporous alumina, Sci. China-Phys. Mech. Astron. 63, 276113 (2020), https://doi.org/10.1007/s11433-020-1535-3
Introduction
Owing to the nonequilibrium nature, glasses usually exhibit plenty of relaxations, and phase transformations [1,2]. In recent decades, the size-dependent kinetics of various glassy materials have attracted extensive research interests. For example, the surface atoms diffuse much faster compared to the inner bulk atoms [3-5]. The enhanced surface diffusion is attributed to the vanishing of intermolecular coupling in the surface [5]. Glasses confined in nanometer-scale can exhibit
*Corresponding authors (Jun-Qiang Wang, email: [email protected]; Wei Wu, email: [email protected])
abnormal crystallization and relaxation kinetics that are not observed in bulk systems [6-11]. For example, the nucleation kinetics of glassy isotactic polypropylene transform from heterogeneous to homogeneous along with the decrease of nanoconfinement size [9]. If the nanopore size is smaller than the critical nucleus siz
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