کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
7901377 | 1510435 | 2015 | 8 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Revealing the rich dynamics of glass-forming systems by modification of composition and change of thermodynamic conditions
ترجمه فارسی عنوان
تشخیص پویایی غنی از سیستم های تشکیل شیشه با تغییر ترکیب و تغییر شرایط ترمودینامیکی
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کلمات کلیدی
انتقال شیشه، مخلوط دوتایی، فشار، آرامش ثانویه آرامش بین مولکولی،
موضوعات مرتبط
مهندسی و علوم پایه
مهندسی مواد
سرامیک و کامپوزیت
چکیده انگلیسی
Secondary relaxations have been classified into two types, depending on whether they are related to the structural α-relaxation in properties or not. Those secondary relaxations that are related to the α-relaxation may have fundamental importance, and are called the Johari-Goldstein (JG) β-relaxations. Two polar molecular glass-formers, one flexible and another rigid, dissolved in apolar host with higher glass transition temperature are studied by broadband dielectric spectroscopy at ambient and elevated pressure. The neat flexible glass-former diethylphthalate (DEP) has a resolved secondary relaxation which, unlike the α-relaxation, is insensitive to pressure and hence is not the JG β-relaxation. In the solution, the JG β-relaxation of DEP shows up in experiment and its relaxation time Ïβ is pressure and temperature dependent like Ïα. The result supports the universal presence of the JG β-relaxation in all glass-formers, and the separation between Ïα and Ïβ is determined by intermolecular interaction. The rigid glass-former is cyano-benzene (CNBz) and its secondary relaxation involves the entire molecule is necessarily the JG β-relaxation. The dielectric relaxation spectra obtained at a number of combinations of pressure and temperature at constant Ïα show not only unchanged is the frequency dispersion of the α-relaxation but also Ïβ. The remarkable results indicate that the JG β-relaxation bears a strong connection to the α-relaxation, and the two relaxations are inseparable when considering the dynamics of glass-forming systems. Experimentally, Ïα has been found to be a function of the product variables, T/Ïγ, where Ï is the density and γ is a material constant. From the \invariance of the ratio, Ïα/Ïβ, to change of thermodynamic conditions seen in our experiment as well in other systems, it follows that Ïβ is also a function of T/Ïγ, with the same γ at least approximately. Since the JG β-relaxation is the precursor of the α-relaxation, causality implies that the T/Ïγ-dependence originates from the JG β-relaxation and is passed on to the α-relaxation.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Non-Crystalline Solids - Volume 407, 1 January 2015, Pages 98-105
Journal: Journal of Non-Crystalline Solids - Volume 407, 1 January 2015, Pages 98-105
نویسندگان
M. Shahin Thayyil, K.L. Ngai, D. Prevosto, S. Capaccioli,