Glass: Kohlrausch exponent, fragility, anharmonicity

Rault, J.

doi:10.1140/epje/i2012-12026-9

Cited by 14 publications

(6 citation statements)

References 106 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The function F ( t ) can be fitted with the Kohlrausch function (see e.g. ref ): where the KWW parameters β and τ K measure the width of the relaxation time distribution and the average time scale, respectively. The average correlation time τ c is defined as The β-dependent factor Γ(β –1 )/β is equal to one for β = 1 and increases when lowering β, e.g., up to 120 for β = 0.2.…”

Section: Dynamics Under Applied Straincontrasting

confidence: 90%

Acceleration and Homogenization of the Dynamics during Plastic Deformation

et al. 2017

View full text Add to dashboard Cite

A coarse-grained model has been proposed recently in order to describe plastic properties of glassy polymers with space resolution the scale ξ of dynamical heterogeneities. This model allows for describing plastic flow by assuming that the elastic energy stored at the scale of dynamical heterogeneities reduces by a similar amount the free energy barriers for αrelaxation. The aim of this article is to consider in more details the evolution of the distribution of relaxation times under plastic deformation. This is achieved by taking explicitly into account the so-called facilitation mechanism during plastic flow introduced by Merabia and Long [Eur.

show abstract

Section: Dynamics Under Applied Straincontrasting

confidence: 90%

Acceleration and Homogenization of the Dynamics during Plastic Deformation

et al. 2017

View full text Add to dashboard Cite

show abstract

“…One might expect that three processes could occur during annealing. The first is the structural relaxation [77,78], the second is the primary crystallization, and the third is the secondary crystallization [79]. For a couple of homopolymers, it was shown that nucleation and crystallization follow the structural relaxation during annealing below and in the glass transition region [42].…”

Section: Ta (°C)mentioning

confidence: 99%

Competition between Structural Relaxation and Crystallization in the Glass Transition Range of Random Copolymers

Schawe

Wrana

2020

Polymers

View full text Add to dashboard Cite

Structural relaxation in polymers occurs at temperatures in the glass transition range and below. At these temperatures, crystallization is controlled by diffusion and nucleation. A sequential occurrence of structural relaxation, nucleation, and crystallization was observed for several homopolymers during annealing in the range of the glass transition. It is known from the literature that all of these processes are strongly influenced by geometrical confinements. The focus of our work is copolymers, in which the confinements are caused by the random sequence of monomer units in the polymer chain. We characterize the influence of these confinements on structure formation and relaxation in the vicinity of the glass transition. The measurements were performed with a hydrogenated nitrile-butadiene copolymer (HNBR). The kinetics of the structural relaxation and the crystallization was measured using fast differential scanning calorimetry (FDSC). This technique was selected because of the high sensitivity, the fast cooling rates, and the high time resolution. Crystallization in HNBR causes a segregation of non-crystallizable segments in the macromolecule. This yields a reduction in mobility in the vicinity of the formed crystals and as a consequence an increased amount of so-called “rigid amorphous fraction” (RAF). The RAF can be interpreted as self-assembled confinements, which limit and control the crystallization. An analysis of the crystallization and the relaxation shows that the kinetic of both is identical. This means that the Kohlrausch exponent of relaxation and the Avrami exponent of crystallization are identical. Therefore, the crystallization is not controlled by nucleation but by diffusion and is terminated by the formation of RAF.

show abstract

“…In particular, a number of authors 128, 129 have suggested that the scale of collective motion in GF liquids, i.e., the number of particles in a cooperatively rearranging regions and the quantity we identify with L , should be inversely proportional to the stretching exponent β s describing the decay of the intermediate scattering function [ I ( q,t ) ≈ exp[-( t / τ) β s ]; [See Supplementary Material for definition of I ( q,t ) and some illustrative data] and other structural relaxation processes of GF materials. 130, 131 If this relation were true for our NPs, then it would link the variation of β s to the noise exponent α DWF and L .…”

Section: Model Relating Mobility Fluctuations To the Scale Of Collectmentioning

confidence: 99%

“…There also has been some speculation that collective motion has some relation to the stretched exponential relaxation of disordered condensed materials, and this interesting hypothesis can be examined in our NP interfacial dynamics simulations. In particular, a number of authors 128,129 have suggested that the scale of collective motion in GF liquids, i.e., the number of particles in a cooperatively rearranging regions and the quantity we identify with L, should be inversely proportional to the stretching exponent b s describing the decay of the intermediate scattering function [I(q,t) z exp[À(t/s) bs ]; [see ESI † for denition of I(q,t) and some illustrative data] and other structural relaxation processes of GF materials. 130,131 If this relationship were true for our NPs, then it would link the variation of b s to the noise exponent a DWF and L. To test this possibility, we determined I(q,t) for the NP interfacial dynamics and found the stretching exponent to be essentially unchanged (b s ¼ 0.36 AE 0.02) for the entire T range we investigated, a similar b s value being obtained in our previous simulations of Ni GBs.…”

Section: Model Relating Mobility Fluctuations To the Scale Of Collect...mentioning

confidence: 99%

Glassy interfacial dynamics of Ni nanoparticles: part I Colored noise, dynamic heterogeneity and collective atomic motion

Zhang

Douglas

2013

Soft Matter

View full text Add to dashboard Cite

Most condensed materials exhibit a significant fraction of atoms, molecules or particles that are strongly interacting with each other, while being configured geometrically at any instant of time in an ‘amorphous’ state having a relatively uniform density. Recently, both simulations and experiments have revealed that the dynamics of diverse condensed amorphous materials is generally characterized by significant heterogeneity in the local mobility and by progressively increasing collective motion upon cooling that takes the form of string-like collective particle rearrangements. The direct experimental observation of this type of collective motion, which has been directly linked to the growing relaxation times of glass-forming materials, and its quantification under different thermodynamic conditions, has so far been restricted to colloidal and driven granular fluids. The present work addresses the fundamental problem of how to determine the scale of this type of collective motion in materials composed of molecules or atoms. The basic premise of our work is that large scale dynamic particle clustering in amorphous materials must give rise to large fluctuations in particle mobility so that transport properties, especially those related to particle mobility, should naturally exhibit noise related to the cooperative motion scale. In our initial exploratory study seeking a relationship of this kind, we find 1/fα or ‘colored noise’, in both potential energy and particle displacements fluctuations of the atoms within the glassy interfacial layer of Ni nanoparticles (NPs). A direct relation between the particle displacement (mobility) noise exponent α and the average polymerization index of the string-like collective motion L is observed for a range of NP sizes, temperatures and for surface doping of the NPs with other metal atoms (Ag, Au, Pt) to change of fragility of the glassy interfacial layer at the surface of the Ni NPs. We also introduce a successful analytic model to understand this relationship between α and L

show abstract

Glass: Kohlrausch exponent, fragility, anharmonicity

Cited by 14 publications

References 106 publications

Acceleration and Homogenization of the Dynamics during Plastic Deformation

Acceleration and Homogenization of the Dynamics during Plastic Deformation

Competition between Structural Relaxation and Crystallization in the Glass Transition Range of Random Copolymers

Glassy interfacial dynamics of Ni nanoparticles: part I Colored noise, dynamic heterogeneity and collective atomic motion

Contact Info

Product

Resources

About