Relaxation Spectra and Relaxation Processes in Solid Polymers and Glasses

Hopkins, I. L.; Kurkjian, Charles R.

doi:10.1016/b978-0-12-395662-0.50012-6

Cited by 15 publications

(8 citation statements)

References 123 publications

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“…The theoretical stress relaxation spectra for ß-exponent law has an asymmetrical form (Hopkins & Kurkjian, 1965). For ß = 0.5 the analytical expression for the relaxation time spectrum is Thus the form and the position of relaxation spectra maximum obtained from experiments on haplogranite samples corresponds to the expression (20) except for the fluorine-bearing melt.…”

Section: Relaxation Spectrummentioning

confidence: 98%

Effect of boron, phosphorus and fluorine on shear stress relaxation in haplogranite melts

Bagdassarov¹,

Dingwell²,

Webb³

1993

ejm

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Shear stress relaxation in haplogranite melts has been investigated using torsional deformation. Sinusoidal shear strains of small amplitude (10 _3 -10~5) have been generated over 4 orders of magnitude of strain rate and a wide range of temperatures. The viscoelastic behavior of the investigated melts can be characterized in terms of the complex shear modulus, the complex shear viscosity, and the internal friction. With addition of B, P, F to a haplogranite melt, the relaxation spectrum becomes broader, skewing further towards shorter relaxation times. Thus, the solution of volatiles in highly polymerized melts leads to a broadening, in frequency-temperature space, of the viscoelastic region which separates liquid behavior from glassy behavior. The relaxation spectrum of pure haplogranite melt has an asymmetrical form which can be fitted by a stretched exponent with parameter ß ~0.5. The boron-containing melts are characterized by ß~0.4, the phosphorus-and fluorine-containing melts yield ß < 0.4.The unrelaxed shear modulus of the liquids obtained at high frequencies and low temperatures are in agreement with the results of new high-frequency (20 MHz) ultrasonic measurements performed at room temperature. The additions of boron, phosphorus, and fluorine all result in decreases in the unrelaxed shear modulus.The relaxed (or Newtonian) shear viscosity obtained from this study at low frequencies and high temperatures compares well with the data obtained by micropenetration viscometry on the same samples. The present low-temperature viscosity data together with high-temperature concentric cylinder viscometry measurements describe an Arrhenian relationship for all investigated compositions in the temperature range of 650-1650 °C. The activation energy of viscous flow decreases with B, P and F content. Key-words: haplogranite melt, shear viscosity, complex shear modulus, shear stress relaxation spectrum, internal friction. Introductionrelaxed loss modulus (Newtonian viscosity × strain rate) to the unrelaxed storage (elastic) modThe nature of viscous deformation in silicate ulus. Many aspects of transport in silicate melts, melts has emerged, in recent years, as a central including Si self diffusivity (Dingwell & Webb, theme, linking the macroscopic transport proper-1990), nonbridging oxygen lifetimes (Liu et ai, ties of silicate melts to the microscopic structure 1988; Farnan & Stebbins, 1990a, b), backreaction of such materials (Sato & Manghnani, 1985; Liu of hydrous species during quenching (Silver, et al. 9 1988; Rivers & Carmichael, 1987; Ding-1988) and the onset of non-Newtonian viscosity well & Webb, 1989McMillan et al, 1992; are usefully scaled by Stebbins et al., 1992). Our current knowledge of such an approximation. This modulus ratio and the spectrum of relaxation processes in silicate the corresponding mechanical model (the Maxmelts is, however, incomplete. We know for ex-well model) remain nevertheless an approximaample that the high-temperature relaxation mode tion of the more detailed picture ...

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Section: Relaxation Spectrummentioning

confidence: 98%

Effect of boron, phosphorus and fluorine on shear stress relaxation in haplogranite melts

Bagdassarov¹,

Dingwell²,

Webb³

1993

ejm

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“…First, the loss spectrum of strong glasses lacks a peak or a shoulder on the high frequency side. Second, the typical network structure relaxes around the temperature at which the frequencies of the spectroscopic measurements are utilized. , Therefore, to probe the secondary relaxation in strong glasses, a different method from those generally used in fragile liquids should be applied. In this work, we apply the hyperquenching−annealing−calorimetric scan (HAC) approach.…”

Section: Introductionmentioning

confidence: 99%

Secondary Relaxation Behavior in a Strong Glass

Yue

2008

J. Phys. Chem. B

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In the present paper we study the enthalpy relaxation behavior of the hyperquenched GeO(2) (HQGeO(2)) glass, one of the strongest glass systems. By applying the hyperquenching-annealing-calorimetry approach, we have found that unlike fragile glasses the strong HQGeO(2) glass relaxes in a manner that all the secondary relaxation units contribute to the primary relaxation. By analyzing dynamic properties of the secondary relaxation, we have identified two typical features of the Johari-Goldstein relaxation in the HQGeO(2) glass. First, the quantitative relationship observed here between E(beta) and T(g) agrees well with the empirical relation of the JG relaxation. Second, the characteristic relaxation time of the GeO(2) glass at T(g) is found to be about 10 s, larger than that of relatively fragile glasses. These results verify that the JG peak in strong glasses is hidden by the alpha peak in the dielectric loss curves.

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“…The consistent feature of our spectra is that the asymmetrical form extended intQ the range of short relax ation times. The theoretical stress relaxation spectrum for β exponent low has an asymmetrical form [Hopkins and Kurkjian, 1965]. For β -0.5 the analytical expression for the spectrum is…”

Section: Relaxation Spectrummentioning

confidence: 99%

Frequency dependent rheology of vesicular rhyolite

Bagdassarov¹,

Dingwell²

1993

J. Geophys. Res.

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Frequency dependent rheology of magmas may result from the presence of inclusions (bubbles, crystals) in the melt and/or from viscoelastic behavior of the melt itself. With the addition of deformable inclusions to a melt possessing viscoelastic properties one might expect changes in the relaxation spectrum of the shear stresses of the material (e.g., broadening of the relaxation spectrum) resulting from the viscously deformable geometry of the second phase. We have begun to investigate the effect of bubbles on the frequency dependent rheology of rhyolite melt. The present study deals with the rheology of bubble‐free and vesicular rhyolite melts containing spherical voids of 10 and 30 vol %. We used a sinusoidal torsion deformation device. Vesicular rhyolite melts were generated by the melting (at 1 bar) of an Armenian obsidian (Dry Fountain, Erevan, Armenia) and Little Glass Mountain obsidian (California). The real and imaginary parts of shear viscosity and shear modulus have been determined in a frequency range of 0.005–10 Hz and temperature range of 600°–900°C. The relaxed shear viscosities of samples obtained at low frequencies and high temperatures compare well with data previously obtained by parallel plate viscometry. The relaxed shear viscosity of vesicular rhyolites decreases progressively with increasing bubble content. The relaxation spectrum for rhyolite melt without bubbles has an asymmetric form and fits an extended exponent relaxation. The presence of deformable bubbles results in an imaginary component of the shear modulus that becomes more symmetrical and extends into the low‐frequency/high‐temperature range. The internal friction Q−1 is unaffected in the high‐frequency/low‐temperature range by the presence of bubbles and depends on the bubble content in the high‐temperature/low‐frequency range. The present work, in combination with the previous study of Stein and Spera (1992), illustrates that magma viscosity can either increase or decrease with bubble content, depending upon the rate of style of strain during magmatic flow.

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Relaxation Spectra and Relaxation Processes in Solid Polymers and Glasses

Cited by 15 publications

References 123 publications

Effect of boron, phosphorus and fluorine on shear stress relaxation in haplogranite melts

Effect of boron, phosphorus and fluorine on shear stress relaxation in haplogranite melts

Secondary Relaxation Behavior in a Strong Glass

Frequency dependent rheology of vesicular rhyolite

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