Linear and non-linear structural relaxation

Moynihan, Cornelius T.; Crichton, S.N.; Opalka, Susanne M.

doi:10.1016/0022-3093(91)90335-4

Cited by 129 publications

(90 citation statements)

References 24 publications

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“…A useful concept, commonly used to describe the glass transition, is that of fictive temperature (T f ; Tool 1946) in which the macroscopic property of a glass (e.g., volume V or enthalpy H) is described in terms of the temperature at which the glass would be in equilibrium. The fictive temperature is a convenient, conceptual term used to describe the relaxation of structure following a rapid change in temperature and reflects the kinetically impeded rearrangement of liquid structure (Moynihan et al 1991), which itself is described by the structural relaxation time, t.…”

Section: Introductionmentioning

confidence: 99%

Cooling rates of hyaloclastites: applications of relaxation geospeedometry to undersea volcanic deposits

Wilding¹,

Dingwell

Batiza

et al. 2000

Bull Volcanol

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Glass fragments from three different hyaloclastites have been used to evaluate the range of cooling rates experienced by undersea volcanic deposits. We found that the glass fragments retain structures with a range of apparent quench rates from 25 to 0.15 K min -1 . The most rapid cooling rates are interpreted to be those resulting from cooling of the lava near the water interface. Simple conductive cooling models produce a range of quench rates comparable to those of the more rapidly cooled samples. The very slow apparent quench rates are unlikely to result from simple linear cooling through the glass transition, because of the onset of crystallization; instead, they are indicators of a more complex thermal history that involves the annealing of glasses at temperatures within the glass transition interval for a dwell time sufficient to allow the relaxation of the glass to lower temperature structures. The thermal history recorded in these samples illustrates the complexity of eruptive processes and demonstrates that quench rates for natural glasses retain information relevant to more complex cooling models.

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Section: Introductionmentioning

confidence: 99%

Cooling rates of hyaloclastites: applications of relaxation geospeedometry to undersea volcanic deposits

Wilding¹,

Dingwell

Batiza

et al. 2000

Bull Volcanol

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“…In order to consolidate these identifications it is worthwhile to explore the dynamic heterogeneity in the series, intertwined with the temperature-frequency scaling that develops near the glass transition. As early as 1965 Adam and Gibbs 11) observed that as one approaches T g from above, the fast dynamics involving fewer atoms (Johari-Goldstein β-process 22) ) decouples from the slow α-relaxations that are characterized by cooperative motion of groups of 35-to-300 atoms. This diffusive dynamics becomes successively sluggish, as the temperature is decreased, eventually giving rise to a diverging timescale at the Vogel-Fulcher temperature T 0 .…”

Section: Resultsmentioning

confidence: 99%

“…Moreover, relatively scarce studies 10) relate these characteristics to appropriate physical parameters. The fact that temperature-scanning experiments are essentially of non-equilibrium kind 11) has to be taken into account while interpreting its thermogram. Examining glass transition at various heating rates, of materials covering a breadth of property-values is one way to explore these issues.…”

Section: Introductionmentioning

confidence: 99%

Thermo-Kinetic Anomalies across Rigidity Threshold in Ge<SUB>x</SUB>Se<SUB>1-x</SUB>

Awasthi

Sampath

2002

Mater. Trans.

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We have investigated the glass-transition kinetics of nine Ge x Se 1−x glasses by differential scanning calorimetry. Relation between the drive (heating-rate q) and response (heatflow shift ∆H at T g ) is seen to be strictly linear only for GeSe 4 , known to signify the bulk-rigidity threshold for this series. From an Arrhenius analysis the activation energies for glassy relaxation are estimated, and point to the existence of different thermokinetic phases below and above the threshold composition. Series behaviour of the kinetic activation is conciled to a concurring one seen in the size of cooperatively diffusing regions. The anomalies are attributed to structural crossovers with Ge doping; first from the parent uniform Se-chains to that of backbones out-branching at corner-shared Ge(Se 1/2 ) 4 tetrahedral clusters, and subsequently interconnecting by edge-shared configurations to realize a random pearl-necklace 3-D covalent network.

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“…[9] These approaches are based on some phenomenological assumptions: the linearization of the relaxation process using the reduced time concept, [7] an asymmetric distribution of relaxation times [discrete for KAHR, continuous (through the stretched exponential function) for TNM] to account for the non-exponential character of relaxation, the introduction of the fictive temperature [10] as structural parameter to account for non-linearity, and the generalization of the timetemperature superposition principle. Whilst each of the assumptions of the TNM model can be criticized, [11,12] this approach is generally able to reproduce the differential scanning calorimetry (DSC) scans recorded on heating the sample after annealing in the glass. On the other hand, clear discrepancies have been observed, notably for polymers, when several thermograms were considered for simultaneous fitting.…”

Section: Introductionmentioning

confidence: 99%

Enthalpy Relaxation of Polymers: On the Possible Role of Liquid‐Crystalline Order

Andreozzi

Autiero

Faetti

et al. 2008

Macromol. Rapid Commun.

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Isothermal physical ageing experiments were performed by differential scanning calorimetry to probe the enthalpy relaxation in a methacrylate copolymer carrying azobenzene mesogenic side groups. Further evidence of the ability of the configurational entropy model developed by Gomez Ribelles in describing the structural relaxation mechanism of polymers is provided. The trend of the equilibrium structural relaxation time was also determined as a function of the reduced temperature Tg/T. The comparison of the aging dynamics of the copolymer with those of previous analogous copolymers containing different amounts of azobenzene counits allowed us to highlight effects of the liquid‐crystalline nematic order on the properties of structural relaxation.magnified image

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Linear and non-linear structural relaxation

Cited by 129 publications

References 24 publications

Cooling rates of hyaloclastites: applications of relaxation geospeedometry to undersea volcanic deposits

Cooling rates of hyaloclastites: applications of relaxation geospeedometry to undersea volcanic deposits

Thermo-Kinetic Anomalies across Rigidity Threshold in Ge<SUB>x</SUB>Se<SUB>1-x</SUB>

Enthalpy Relaxation of Polymers: On the Possible Role of Liquid‐Crystalline Order

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