Maxwell relaxation time for nonexponential α‐relaxation phenomena in glassy systems

2020 ◽  
Vol 103 (6) ◽  
pp. 3590-3599
Author(s):  
Karan Doss ◽  
Collin J. Wilkinson ◽  
Yongjian Yang ◽  
Kuo‐Hao Lee ◽  
Liping Huang ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Relaxation Phenomena ◽  
Glassy Systems ◽  
Maxwell Relaxation Time

Ultrasonic Absorption and Relaxation Phenomena in Molten Nitrate Mixtures

1986 ◽  
Vol 41 (3) ◽  
pp. 535-544 ◽  
Author(s):  
J. Richter ◽  
B. Fuchs
Keyword(s):  
Relaxation Time ◽  
Molten Salt ◽  
Structural Relaxation ◽  
Composition Range ◽  
Frequency Interval ◽  
Relaxation Phenomena ◽  
Ultrasonic Absorption ◽  
Volume Viscosity ◽  
Salt Mixtures ◽  
Total Composition

An optical device based on the Debye-Sears effect is developed to determine the ultrasonic absorption and velocity in molten alkali nitrate + silver nitrat mixtures. RbNO3 + AgNO3 and CsNO3 + AgNO3 are investigated in the total composition range between 480 K and 580 K within a frequency interval from 10 MHz to 35 MHz. In the concentration range of high ultrasonic absorption we find dispersion and a frequency dependent step in the absorption curve caused by relaxation. The relaxation time of the structural relaxation in the molten salt mixtures investigated here is in the order of 10-8 s.The volume viscosity, the adiabatic constant, and the compressibilities are calculated.

Maxwell relaxation time for argon and water

2019 ◽  
Vol 293 ◽  
pp. 111413 ◽  
Author(s):  
Nikolay P. Malomuzh ◽  
Konstantin S. Shakun
Keyword(s):  
Relaxation Time ◽  
Maxwell Relaxation Time

CHARACTERIZATION OF DOPED SILLENITES BY ELECTROOPTIC AND SPECTRAL METHODS

2001 ◽  
Vol 15 (17n19) ◽  
pp. 749-751
Author(s):  
A. ILINSKII ◽  
T. PRUTSKIJ ◽  
F. SILVA-ANDRADE ◽  
F. CHÁVEZ ◽  
E. SHADRIN ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Spectral Methods ◽  
Electrooptical Properties ◽  
Maxwell Relaxation Time

The main result of this paper was the high accurate characterization of the investigated samples. We were able to measure the Maxwell relaxation time for doped (Al, Cr, Mn, Ti, Nd) and undoped sillenite crystals was determined. The obtained values are as large as 103s. Also, the correlation between spectroscopic, electrical and electrooptical properties of doped sillenite crystals was established.

Low Temperature Relaxation Phenomena in Rubber-Like Polymers Subjected to Low Deformation

1972 ◽  
Vol 45 (1) ◽  
pp. 71-81
Author(s):  
G. M. Bartenev ◽  
A. M. Kucherskii
Keyword(s):  
Relaxation Time ◽  
Critical Stress ◽  
Glassy State ◽  
Strong Dependence ◽  
Relaxation Phenomena ◽  
3 Dimensional ◽  
Critical Stresses ◽  
New Process ◽  
Temperature Relaxation ◽  
Small Deformations

Abstract 1. A new relaxation process was discovered which explains the change, at critical tensile stresses (0.1–0.5 kg/cm2), in the elasticity of rubber-like polymers subjected to small deformations. This new process is characterized by relatively low activation energies (weak dependence of temperature on relaxation time) and kinetic units that are large (strong dependence of relaxation time on stress). The kinetic stress is a function of the temperature and for rubbery polymers it is reduced to zero, at 40° –60° C. 2. The mechanism of this phenomenon is elucidated by the existence of ordered, supermolecular microregions forming, with the free chains of 3-dimensional networks, supplementary bundles of non-chemical origin which disintegrate under, critical stresses. The activities observed are analogous to the processes of forced-elastic deformation in the same polymers in the glassy state. The critical stress is analogous to the limit of forced elasticity at low second order (glass) transition temperatures.

Viscoelastic Effects on Lubricant Depletion and Recovery Under Heat-Assisted Magnetic Recording (HAMR) Conditions

2016 ◽  
Author(s):  
Soroush Sarabi ◽  
David B. Bogy
Keyword(s):  
Relaxation Time ◽  
Magnetic Recording ◽  
Viscoelastic Behavior ◽  
Spot Size ◽  
Deborah Number ◽  
Lubrication Theory ◽  
Laser Spot ◽  
Laser Spot Size ◽  
Heat Assisted Magnetic Recording ◽  
Maxwell Relaxation Time

Heat Assisted Magnetic Recording (HAMR) is a developing data-storage technology in which a laser delivery system is integrated to the conventional HDD air bearing slider that carries the read and write transducers. The laser beam heats a small spot of around 20nm size on the storage media up to few hundred degrees Celsius [1]. This heating causes several effects on the lubricant such as temperature gradient, thermocapillary shear stress, viscosity drop, and evaporation followed by its depletion. Conventionally [2–8], the disk lubricant is considered as a Newtonian viscous fluid that can be fully described by a viscosity parameter μ. However, in rapid heating and forcing conditions like HAMR, the time dependent nature of the lubricant becomes very important. Measurements [9] show that under some conditions the lubricant behaves like a Maxwell viscoelastic fluid that can be described by two parameters: viscosity μ and Maxwell relaxation time λ. Itoh et al. [10] show that the viscoelastic behavior becomes even more considerable in the case of sub-10nm material confinement. Both the Maxwell relaxation time and viscosity can be functions of temperature and lubricant thickness in case of ultra-thin film lubrication. Karis [9] measured Maxwell relaxation time as a function of temperature for a variety of lubricants, such as Z-dol and Z-tetraol. Fig. 1 shows the results of these measurements for both Z-dol and Z-tetraol. Maxwell relaxation time plays a vital role in determining the behavior of the material under thermal and mechanical loads. In order to have a proper understanding of the effect of Maxwell relaxation time, we non-dimensionalize this parameter by the timescale of the problem to introduce a non-dimensional Deborah number De = λU/L. So, De is a function of HAMR temperature T, disk speed U, laser spot size L, and lubricant type. For purely-viscous materials both the Maxwell relaxation time and De are zero and for purely-elastic materials, both are infinity. So in the case of viscoelasticity, if De ≪ 1 the viscosity mode is dominant, if De ≫ 1 the elasticity is dominant, and if De ≈ 1 the material behaves viscoelastically. Therefore, De is good measure for the viscoelastic behavior of the material. Some attempts have been made to fit the lubrication theory for viscoelastic materials using perturbation methods. However these methods require that the Deborah Number be small enough [11]. Fig. 2 shows the Deborah Number as a function of laser spot size for different lubricant temperatures. Accordingly, at the target of a HAMR laser spot size of L = 20nm, the Deborah number is very large and therefore, the material behaves less viscous and more elastic. Therefore, the traditional methods of lubrication theory cannot describe the lubricant’s behavior in this limit. Consequently, we developed anew direct Finite Element Method (FEM) approach to simulate the behavior of the linear viscoelastic Maxwell fluid lubricants under HAMR conditions.

scholarly journals Relationship between local structure and relaxation in out-of-equilibrium glassy systems

2016 ◽  
Vol 114 (2) ◽  
pp. 263-267 ◽  
Author(s):  
Samuel S. Schoenholz ◽  
Ekin D. Cubuk ◽  
Efthimios Kaxiras ◽  
Andrea J. Liu
Keyword(s):  
Relaxation Time ◽  
Glass Transition ◽  
External Perturbation ◽  
State Variables ◽  
History Dependence ◽  
Structure And Dynamics ◽  
Structure Changes ◽  
Glassy Systems ◽  
The Relationship ◽  
Usual State

The dynamical glass transition is typically taken to be the temperature at which a glassy liquid is no longer able to equilibrate on experimental timescales. Consequently, the physical properties of these systems just above or below the dynamical glass transition, such as viscosity, can change by many orders of magnitude over long periods of time following external perturbation. During this progress toward equilibrium, glassy systems exhibit a history dependence that has complicated their study. In previous work, we bridged the gap between structure and dynamics in glassy liquids above their dynamical glass transition temperatures by introducing a scalar field called “softness,” a quantity obtained using machine-learning methods. Softness is designed to capture the hidden patterns in relative particle positions that correlate strongly with dynamical rearrangements of particle positions. Here we show that the out-of-equilibrium behavior of a model glass-forming system can be understood in terms of softness. To do this we first demonstrate that the evolution of behavior following a temperature quench is a primarily structural phenomenon: The structure changes considerably, but the relationship between structure and dynamics remains invariant. We then show that the relaxation time can be robustly computed from structure as quantified by softness, with the same relation holding both in equilibrium and as the system ages. Together, these results show that the history dependence of the relaxation time in glasses requires knowledge only of the softness in addition to the usual state variables.

Viscoelasticity Associated with Molecular Alignment

1980 ◽  
Vol 35 (9) ◽  
pp. 915-919 ◽  
Author(s):  
S. Hess
Keyword(s):  
Relaxation Time ◽  
Time Scale ◽  
Viscoelastic Behavior ◽  
Present Theory ◽  
Molecular Alignment ◽  
Orientational Relaxation ◽  
Liquid Solutions ◽  
Relaxation Experiments ◽  
Aqueous Detergent ◽  
Maxwell Relaxation Time

Abstract Viscoelasticity as it becomes apparent through the oscillatory motion in flow relaxation experiments is studied theoretically for liquids and liquid solutions containing nonspherieal particles. The coupling between the viscous flow and the molecular alignment which underlies the flow birefringence gives rise to a viscoelastic behavior. The relevant time scale is determined by the orientational relaxation time rather than the (often much shorter) Maxwell relaxation time. The possible relevance of the present theory for the viscoelastic behavior of some dilute aqueous detergent solutions is discussed.

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