On the use of relaxation times for comparing ultraviscous liquid dynamics
Abstract:
In studies of ultraviscous liquids and glasses, (i) the relaxation time and its temperature dependence are generally compared without regard to its asymmetric distribution and (ii) the calorimetric relaxation time at T(g,DSC), the onset temperature of the specific heat rise in a heating scan at 20 K/min, is arbitrarily chosen as 100 s and compared against the relaxation time determined by spectroscopy. We propose that the relaxation time and its derivatives should be compared in a fixed frame of reference, preferably by using its average value that takes into account the asymmetric distribution, and we show that the relaxation time at T(g,DSC) is a material characteristic. It varies with the extent of nonexponential and nonlinear relaxation and the activation energy.
More Related Videos
Related Concept Videos
Viscosity
Viscosity
The SI unit of viscosity is...
Viscosity of Fluid
Newtonian Fluid: Problem Solving
A velocity gradient forms within the fluid when a Newtonian fluid is placed between two parallel plates, with...
Atomic Nuclei: Types of Nuclear Relaxation
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers energy to a nearby...
Pressure Variation in a Fluid at Rest
When measuring pressure at two different levels within the fluid, the difference in pressure...


