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首页> 外文期刊>Journal of Non-Crystalline Solids: A Journal Devoted to Oxide, Halide, Chalcogenide and Metallic Glasses, Amorphous Semiconductors, Non-Crystalline Films, Glass-Ceramics and Glassy Composites >Free volume factor in supercooled liquid dynamics
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Free volume factor in supercooled liquid dynamics

机译：过冷液体动力学中的自由体积因数

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摘要

The positronium (o-Ps) annihilation lifetime parameters, i.e., the mean o-Ps lifetime, tau(3), and the relative o-Ps intensity, I-3, were measured for a series of molecular and structurally simple polymer glass formers over wide temperature ranges by means of positron annihilation lifetime spectroscopy (PALS). In addition to the most pronounced effect defining the PALS glass temperature, T-g(PALS) further two groups of the characteristic bend temperatures in the liquid state, one at T-b1(lq) congruent to 1.15-1.4T(g)(PALS) and the other at T-b2(lq) congruent to 1.3-1.75T(g)(PALS) were found. These characteristic temperatures were compared with certain crossover temperatures from both empirical (T-g, T-m; T-B, T-A, T-coll ; T-M) and theoretical (T-cr) analyses of the thermodynamic and numerous dynamic data and their coincidences were discussed. Decrease in I-3-T plots for glycerol and cis- trans-1,4-polybutadiene can be related to the fast motions on the nanosecond time scale as detected by neutron scattering or dielectric spectroscopy. The corresponding free volume hole characteristics, i.e., the mean free volume hole size, R-h, and the free volume hole fraction, f(h), were determined by using a quantum-mechanical model of o-Ps in spherical hole or a model of volumetric and free volume hole properties, respectively. Consequently, the role of the free volume hole fraction from the PALS data in the dynamics of some supercooled liquids was established by analyses of various expressions containing the free volume fraction such as the Doolittle-type equation or the Macedo-Litovitz ansatz. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 49]
机译：测量了一系列分子和结构简单的聚合物玻璃成型体的正电子（o-Ps）lifetime灭寿命参数，即平均o-Ps寿命tau（3）和相对o-Ps强度I-3。正电子an没寿命谱（PALS）在很宽的温度范围内工作。除了最明显的影响定义PALS玻璃温度外，Tg（PALS）还具有两组液态的特征弯曲温度，一组在T-b1（lq）处等于1.15-1.4T（g）（PALS）发现另一个在T-b2（lq）处等于1.3-1.75T（g）（PALS）。从经验（T-g，T-m; T-B，T-A，T-coll; T-M）和理论（T-cr）对热力学和大量动态数据的分析以及它们的符合性进行了比较，将这些特征温度与某些交叉温度进行了比较。甘油和顺-反-1,4-聚丁二烯在I-3-T图中的减少可能与中子散射或介电光谱法检测到的纳秒级时速运动有关。相应的自由体积孔特性，即平均自由体积孔尺寸Rh和自由体积孔分数f（h），是通过使用球形孔中o-Ps的量子力学模型或体积和自由体积孔的特性。因此，通过分析包含自由体积分数的各种表达式（例如Doolittle型方程或Macedo-Litovitz ansatz），可以确定来自PALS数据的自由体积孔分数在某些过冷液体动力学中的作用。 （C）2002 Elsevier Science B.V.保留所有权利。 [参考：49]

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