Internal friction spectroscopy in Li20-2SiO2 partially crystallised glasses.

Müller, K. and Bagdassarov, N. S. and James, M. R. and Schmeling, H. and Deubener, J. (2003) Internal friction spectroscopy in Li20-2SiO2 partially crystallised glasses. Journal of Non-Crystalline Solids, 319 (1-2). pp. 44-56. ISSN 0022-3093

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Oscillatory torsion deformation experiments were performed on partially crystallised Li2O–2SiO2 glasses in the temperature range 350–480 °C and with frequencies between 20 and 0.002 Hz. The experiments were carried out in a torsion deformation apparatus exerting a small strain on cylindrical samples. Data obtained at varying temperatures and frequency were reduced to master plots using a normalised frequency. The frequency shift factor has been taken as a function of temperature in an Arrhenian form, yielding an activation energy of a background Q−1 close to the activation energy of oxygen defect diffusion (=120 kJ/mol). The master curves of real and imaginary components of shear modulus and internal friction indicate a stretched exponential shear stress relaxation with a an exponent of ≈0.45, characteristic of a broadened relaxation spectrum. The dynamic viscosity was estimated at temperatures of 470 and 480 °C. The extrapolation of dynamic viscosity to zero frequency allowed estimation of the relaxed shear viscosity. The presence of crystals increases the relaxed shear viscosity by ≈0.2log(Pa s)/10 vol.% of crystallinity. Dependence of the relative shear viscosity of partially crystallised lithium disilicate melts on crystal content is discussed.

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Journal Article
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Journal of Non-Crystalline Solids
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13 Jan 2009 10:27
Last Modified:
21 Nov 2022 18:46