Structural relaxation in the glass: Evidence for a path dependence of the relaxation time

Simon, Sindee L.; Bernazzani, Paul

doi:10.1016/j.jnoncrysol.2006.01.151

Cited by 42 publications

(35 citation statements)

References 64 publications

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“…However, as shown in Table 3, the TNM model parameters obtained from fitting the three sets of data are quantitatively different, and for one data set, x decreases for the stacked ultrathin films, whereas for the other sets, it increases relative to the bulk value. In fact, the TNM model has documented shortcomings, including the inability to describe multiple data sets and to capture thermal history with one set of parameters, the lack of physical meaning of x, and a mutual dependence of b 24,47,48,[59][60][61] Nevertheless, the nonexponentiality parameter b for all three sets of data is lower for the stacked ultrathin films, which indicates that an increased distribution of relaxation times and a broadening of the glass transition is a distinct characteristic of nanoconfinement. Our stacked ultrathin film sample also shows a lower value of the fragility index (i.e., it is a stronger glass former as shown in Table 2) than the bulk despite its lower value of b (i.e., increased heterogeneity).…”

Section: Discussionmentioning

confidence: 99%

Structural relaxation of stacked ultrathin polystyrene films

Koh

Simon

2008

J Polym Sci B Polym Phys

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The T g depression and kinetic behavior of stacked polystyrene ultrathin films is investigated by differential scanning calorimetry (DSC) and compared with the behavior of bulk polystyrene. The fictive temperature (T f ) was measured as a function of cooling rate and as a function of aging time for aging temperatures below the nominal glass transition temperature (T g ). The stacked ultrathin films show enthalpy overshoots in DSC heating scans which are reduced in height but occur over a broader temperature range relative to the bulk response for a given change in fictive temperature. The cooling rate dependence of the limiting fictive temperature, T f 0 , is also found to be higher for the stacked ultrathin film samples; the result is that the magnitude of the T g depression between the ultrathin film sample and the bulk is inversely related to the cooling rate. We also find that the rate of physical aging of the stacked ultrathin films is comparable with the bulk when aging is performed at the same distance from T g ; however, when conducted at the same aging temperature, the ultrathin film samples show accelerated physical aging, that is, a shorter time is required to reach equilibrium for the thin films due to their depressed T g values. The smaller distance from T g also results in a reduced logarithmic aging rate for the thin films compared with the bulk, although this is not indicative of longer relaxation times. The DSC heating curves obtained as a function of cooling rate and aging history are modeled using the Tool-Narayanaswamy-Moynihan model of structural recovery; the stacked ultrathin film samples show lower b values than the bulk, consistent with a broader distribution of relaxation times.

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Section: Discussionmentioning

confidence: 99%

Structural relaxation of stacked ultrathin polystyrene films

Koh

Simon

2008

J Polym Sci B Polym Phys

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130

166

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“…This same Dylene 8 polystyrene has been used in a handful of studies in our laboratory, in the laboratory of Prof. D. J. Plazek, and in collaborative studies. [16][17][18][19][20] A custom-built piston-type pressurizable dilatometer was used for measurements reported in this study. In this instrument, the polystyrene sample is surrounded by $ 5 g of fluorinated synthetic oil (Krytox 1 GPL107 from DuPont TM ) as confining fluid.…”

Section: Methodsmentioning

confidence: 99%

Pressure relaxation of polystyrene and its comparison to the shear response

Meng

Simon

2007

J Polym Sci B Polym Phys

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Isothermal pressure relaxation as a function of temperature in two pressure ranges has been measured for polystyrene using a self-built pressurizable dilatometer. A master curve for pressure relaxation in each pressure regime is obtained based on the time-temperature superposition principle, and time-pressure superposition of the two master curves is found to be applicable when the master curves are referenced to their pressure-dependent T g . The pressure relaxation master curves, the shift factors, and retardation spectra obtained from these curves are compared with those obtained from shear creep compliance measurements for the same material. The shift factors for the bulk and shear responses have the same temperature dependence, and the retardation spectra overlap at short times. Our results suggest that the bulk and shear response have similar molecular origin, but that longtime chain mechanisms available to shear are lost in the bulk response.

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“…54 The TNM and similar phenomenological models have had broad success in describing many aspects of structural relaxation in amorphous materials, although their inadequacies have also been well documented. 40,41,51,[55][56][57][58] In the case of the XPCS experiments performed here, the failure of the TNM model is essentially due to the basic assumption that τ depends on the instantaneous state of the material via Tf. This is an over-simplification as it considers that a given glassy configuration can be defined by a single parameter like Tf or some macroscopic variable like specific volume or enthalpy and does not explicitly incorporate any microscopic details of the system under investigation.…”

Section: Resultsmentioning

confidence: 99%

Comparing the atomic and macroscopic aging dynamics in an amorphous and partially crystalline Zr₄₄Ti₁₁Ni₁₀Cu₁₀Be₂₅bulk metallic glass

et al. 2017

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2Several recent x-ray photon correlation spectroscopy works have reported an anomalous atomic dynamics in hyper-quenched metallic glasses. Here, we compare and contrast these microscopic dynamics with that found in a Zr44Ti11Ni10Cu10Be25 bulk metallic glass, prepared with a cooling rate some 6 orders of magnitude lower. In both cases, structural relaxation in the glass is governed by internal stresses, giving rise to highly compressed density correlation functions. Differently from the fast aging reported in previous studies, here the atomic dynamics displays a slow linear atomic-level aging, while not affecting the shape parameter.Traditional macroscopic phenomenological models fail to capture the temperature dependence of the microscopic structural relaxation time, suggesting a length scale dependence of the aging. Interestingly, the dynamics does not seem to be affected by the presence of a low percentage of frozen in nanocrystals and displays a temperature dependence similar to that observed in macroscopic viscosity measurements.3

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Structural relaxation in the glass: Evidence for a path dependence of the relaxation time

Cited by 42 publications

References 64 publications

Structural relaxation of stacked ultrathin polystyrene films

Structural relaxation of stacked ultrathin polystyrene films

Pressure relaxation of polystyrene and its comparison to the shear response

Comparing the atomic and macroscopic aging dynamics in an amorphous and partially crystalline Zr₄₄Ti₁₁Ni₁₀Cu₁₀Be₂₅bulk metallic glass

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Structural relaxation in the glass: Evidence for a path dependence of the relaxation time

Cited by 42 publications

References 64 publications

Structural relaxation of stacked ultrathin polystyrene films

Structural relaxation of stacked ultrathin polystyrene films

Pressure relaxation of polystyrene and its comparison to the shear response

Comparing the atomic and macroscopic aging dynamics in an amorphous and partially crystalline Zr44Ti11Ni10Cu10Be25bulk metallic glass

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Product

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About

Comparing the atomic and macroscopic aging dynamics in an amorphous and partially crystalline Zr₄₄Ti₁₁Ni₁₀Cu₁₀Be₂₅bulk metallic glass