Structural Relaxation in Vitreous Materials*

Moynihan, Cornelius T.; Macedo, P. B.; Montrose, C. J.; Gupta, Prabhat K.; Debolt, Mary Ann; Dill, J. F.; Dom, B. E.; Drake, P. W.; Easteal, Allan J.; Elterman, Paul B.; Moeller, Rolf; Sasabe, Hiroyuki; Wilder, J. A.

doi:10.1111/j.1749-6632.1976.tb39688.x

Cited by 831 publications

(528 citation statements)

References 27 publications

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“…Similar behaviour of the density fluctuations has been also reported in molecular dynamic simulations 39,40 and dielectric spectroscopy studies of polymeric glasses 41 . Differently from previous studies and from macroscopic measurements [4][5][6][7]15,29,[32][33][34][35] , we do not find any evidence of physical aging on our experimental time scale of about B4-6 h at any T, not even close to T g . While the absence of physical aging at very low temperatures has been already reported for polymeric glasses 42 , the observed stationary dynamics in the glass transition region is completely unexpected.…”

Section: Resultscontrasting

confidence: 99%

“…2a (coloured symbols), together with relaxation times extracted from loss shear modulus experiments in the supercooled liquid at equilibrium 44 (black symbols). Both sets of XPCS data show a marked departure from the supercooled liquid at temperatures, T 1 B742 K for NS4-G1 and T 2 B752 K for NS4-G2, consequence of their different thermal history 4,45 . Albeit the different isostructures, the two glasses display a similar weak T dependence, which can be described by an Arrhenius behaviour with an extremely low activation energy of…”

Section: Resultsmentioning

confidence: 96%

“…We show that contrary to the common idea of an almost arrested dynamics, structural glasses are able to relax and rearrange their structure on a length scale of a few Angstroms. On cooling the system in the glassy state, the structural relaxation time strongly departs from the supercooled liquid behaviour and displays a weak temperature dependence, with the absence of any detectable aging not even in the glass transition region, in disagreement with macroscopic studies and theoretical approaches [4][5][6][7]15,29,[32][33][34][35] . The relaxation time is found to be surprisingly fast, B100-1,000 s, even hundreds of degrees below T g , in contrasts with the general idea of an ultraslow dynamics in the deep glassy state.…”

mentioning

confidence: 77%

“…On approaching the glass transition temperature T g , the structural relaxation time t of a supercooled liquid rises dramatically in a narrow temperature range, until the liquid eventually becomes a glass at T g 3 . Very little structural changes accompany this process, which however leads to an extremely complex nonequilibrium state, featuring in irreversible processes like rejuvenation, memory and time asymmetry effects [4][5][6][7][8] . In addition, the response of the glass to a given perturbation, like a temperature change, strongly depends on the composition of the system and on its previous thermal history [4][5][6][7][8][9] .…”

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confidence: 99%

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Revealing the fast atomic motion of network glasses

Baldi²,

et al. 2014

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Still very little is known on the relaxation dynamics of glasses at the microscopic level due to the lack of experiments and theories. It is commonly believed that glasses are in a dynamical arrested state, with relaxation times too large to be observed on human time scales. Here we provide the experimental evidence that glasses display fast atomic rearrangements within a few minutes, even in the deep glassy state. Following the evolution of the structural relaxation in a sodium silicate glass, we find that this fast dynamics is accompanied by the absence of any detectable aging, suggesting a decoupling of the relaxation time and the viscosity in the glass. The relaxation time is strongly affected by the network structure with a marked increase at the mesoscopic scale associated with the ion-conducting pathways. Our results modify the conception of the glassy state and asks for a new microscopic theory.

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Section: Resultscontrasting

confidence: 99%

Section: Resultsmentioning

confidence: 96%

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confidence: 77%

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confidence: 99%

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Revealing the fast atomic motion of network glasses

Baldi²,

et al. 2014

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“…To further illustrate our point, the computations of the configurational specific heat are plotted on the Fig. 6 according to The qualitative comparisons with experiments is best done by computing the normalized configurational specific heat: 34,35 Fig. 7 shows the results of the computations of the normalized configurational heat capacity for two different protocols.…”

Section: Configurational Specific Heatmentioning

confidence: 99%

Affinity and its derivatives in the glass transition process

Garden

Guillou

Richard

et al. 2012

The Journal of Chemical Physics

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The thermodynamic treatment of the glass transition remains an issue of intense debate. When associated with the formalism of non-equilibrium thermodynamics, the lattice-hole theory of liquids can provide new insight in this direction, as has been shown by Schmelzer and Gutzow [J. Chem. Phys. 125, 184511 (2006) (2011)]. Here, we employ a similar approach. We include pressure as an additional variable, in order to account for the freezing-in of structural degrees of freedom upon pressure increase. Second, we demonstrate that important terms concerning first order derivatives of the affinity-driving-force with respect to temperature and pressure have been previously neglected. We show that these are of crucial importance in the approach. Macroscopic non-equilibrium thermodynamics is used to enlighten these contributions in the derivation of C p ,κ T , and α p . The coefficients are calculated as a function of pressure and temperature following different theoretical protocols, revealing classical aspects of vitrification and structural recovery processes. Finally, we demonstrate that a simple minimalist model such as the lattice-hole theory of liquids, when being associated with rigorous use of macroscopic non-equilibrium thermodynamics, is able to account for the primary features of the glass transition phenomenology. Notwithstanding its simplicity and its limits, this approach can be used as a very pedagogical tool to provide a physical understanding on the underlying thermodynamics which governs the glass transition process.

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Thermal incompatibility analysis of metal-ceramic systems based on flexural displacement data

Dehoff

Anusavice

Hojjatie

1998

J. Biomed. Mater. Res.

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The feasibility of simple tests or analytical methods for prediction of residual stress states in metal-ceramic (MC) prostheses has not been demonstrated. Biomaterial metal-ceramic strips have been proposed to provide sensitive measures of transient and residual stress states through the measurement of midpoint deflection after cooling from the ceramic sintering temperature. The objective of this study was to apply the elastic-viscoelastic analogy to calculate transient and residual midpoint deflections in MC biomaterial strips and to compare these values with deflections measured with a beam-bending viscometer (BBV). Calculations and measurements were made for five MC systems that were found from a clinical study to be "thermally compatible" systems. Metal strips, 64 mm in length, 3 mm wide, and either 0.5 mm, 1.0 mm, or 2.0 mm in thickness, were veneered with four 0.25-mm thick layers of opaque porcelain. Midpoint deflection of the MC strips (ceramic oriented in the posterior position) was measured during cooling from an initial temperature of 700 degrees C. In general, the directions of the measured residual deflections did not agree with the "textbook" convention that negative deflections are associated with positive thermal contraction mismatch (alpha(M) - alpha(c) > 0) regardless of metal thickness. For a metal thickness of 0.5 mm, the residual midpoint deflection for all thermal contraction mismatch cases, except one, was positive (upward deflection) whereas the residual midpoint deflections were all negative when the metal thickness was increased to 1 or 2 mm, independent of the thermal contraction mismatch. The best agreement between calculated and measured values of residual midpoint deflection (+16 microns vs. +14 +/- 2.3 microns, respectively was obtained for MC biomaterial strips with a Ni-Cr alloy (0.5 mm thick) while the largest difference (+346 microns vs. +61 +/- 43.8 microns) was obtained for MC bimaterial strips with a Au-Pd allow (0.5 mm thick). In all but one case, changes in deflection direction as a function of metal thickness were correctly predicted by the viscoelastic analysis. The results of this study indicate that a viscoelastic model is useful for estimating thermal compatibility conditions of MC systems.

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Structural Relaxation in Vitreous Materials*

Cited by 831 publications

References 27 publications

Revealing the fast atomic motion of network glasses

Revealing the fast atomic motion of network glasses

Affinity and its derivatives in the glass transition process

Thermal incompatibility analysis of metal-ceramic systems based on flexural displacement data

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