| Autor: |
Di Marzio EA; National Institute of Standards and Technology, Gaithersburg, MD 20899-0001., Yang AJ; Armstrong World Industries, 2500 Columbia Ave., Lancaster, PA 17603. |
| Jazyk: |
angličtina |
| Zdroj: |
Journal of research of the National Institute of Standards and Technology [J Res Natl Inst Stand Technol] 1997 Mar-Apr; Vol. 102 (2), pp. 135-157. |
| DOI: |
10.6028/jres.102.011 |
| Abstrakt: |
A kinetic theory of glasses is developed using equilibrium theory as a foundation. After establishing basic criteria for glass formation and the capability of the equilibrium entropy theory to describe the equilibrium aspects of glass formation, a minimal model for the glass kinetics is proposed. Our kinetic model is based on a trapping description of particle motion in which escapes from deep wells provide the rate-determining steps for motion. The formula derived for the zero frequency viscosity η (0, T ) is log η (0, T ) = B - AF ( T ) kT where F is the free energy and T the temperature. Contrast this to the Vogel-Fulcher law log η (0, T ) = B + A /( T - T c ). A notable feature of our description is that even though the location of the equilibrium second-order transition in temperature-pressure space is given by the break in the entropy or volume curves the viscosity and its derivative are continuous through the transition. The new expression for η (0, T ) has no singularity at a critical temperature T c as in the Vogel-Fulcher law and the behavior reduces to the Arrhenius form in the glass region. Our formula for η (0, T ) is discussed in the context of the concepts of strong and fragile glasses, and the experimentally observed connection of specific heat to relaxation response in a homologous series of polydimethylsiloxane is explained. The frequency and temperature dependencies of the complex viscosity η ( ω < T ), the diffusion coefficient D ( ω < T ), and the dielectric response ε ( ω < T ) are also obtained for our kinetic model and found to be consistent with stretched exponential behavior. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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