The internal friction of glasses

Isothermal mechanical relaxations in single and mixed alkali silicate glasses

“…7 shows that the ionic peak shifts to lower frequency (at fixed temperature) for the mixed alkali glasses. This fact was previously mentioned [4,5,8,[10][11][12].…”

“…The origin of a second peak observed at higher temperature is still debated: it appears only with the presence of non-bridging oxygen and of water. This peak is often called "nonbridging oxygen peak" (NBO peak) [2,[4][5][6][7]. Mixed alkali silicate glasses exhibit a very large internal friction peak [4,5,[8][9][10][11][12].…”

“…Some authors maintain that this peak takes the place of the ionic peak and others that it is superimposed to the peaks observed in the single silicate glasses. Another point of discussion concerns the results obtained for mixed alkali glass with a very low ratio of a second alkali ion [5,8,11]: a small relaxation peak is described by the authors as a mixed alkali peak but in fact this peak can correspond to the NBO peak. In order to clarify this situation, new internal friction experiments were performed using the isothermal mechanical spectroscopy technique allowing very accurate measurements, for four silicate glasses of (1-x)Na 2 O⋅xLi 2 O⋅3SiO 2 type with x = 0, 0.25, 0.5 and 0.75.…”

Internal friction spectroscopy in Li2O–2SiO2 partially crystallised glasses

“…Even a few ppm of dissolved water may affect the internal friction and shear viscosity of silicate glasses. In lithium disilicate glasses containing OH-species protons are attached to non-bridging oxygens and, therefore, affect the mechanical damping [5]. In previous studies on lithium silicates and other alkali silicates it was noticed that with the increase of the OH-species content the activation energy of the high temperature internal friction peak decreases and the peak shifts to lower temperature.…”

“…The long history of internal friction measurements in silicate glasses has demonstrated that they possess a distribution of relaxation times [4]. The internal friction peaks as a function of frequency are much broader than a Debye peak, which were associated with the longitudinal oscillations of bridging oxygen atoms, effects of alkali and non-bridging oxygen ions [5]. For example, in Li 2 O-2SiO 2 there is a low temperature, low frequency internal friction peak at approximately )20°C, which corresponds to alkali ion relaxation and has an activation energy 70-100 kJ/mol [5], and a high temperature peak at %250°C…”