ULTRASONIC MEASUREMENTS AND COMPLEX ELASTIC-MODULI OF SILICATE GLASS MELTS IN THE VISCOELASTIC AND VISCOUS RANGE

The temperature- and frequency-dependence of the ultrasonic velocity and attenuation in glass melts is investigated up to a temperature of 1400 degrees C by means of an equipment for measuring the longitudinal and transversal ultrasonic waves. The range of dispersion and the attenuation maxima are determined at frequencies 0.5 to 4 MHz completely for the DGG standard glass I and for the glass melts (compositions in mol%): 74SiO(2), 16Na(2)O, 10CaO and 74SiO(2), 16K(2)O, 10CaO and partly for the glass melt 74SiO(2), 16Cs(2)O, 10CaO and for the B2O3 melt. The whole number of elastic constants follows from the ultrasonic velocities and from the density in the usual way. The properties of these glass melts art compared along the temperature and viscosity. The transition from the elastic solid to the viscous fluid can be characterized by the elastic moduli and interpreted as a viscoelastic response of an unrelaxed to a relaxed dynamic network which depolymerizes reversibly with increasing and polymerizes with decreasing temperature. The internal friction, Q(-1), characterizes the inelastic portion during the periodical stress of the ultrasonic waves. The activation energy of Q(-1), obtained via frequencies and temperature of the maxima of Q(-1), is nearly twice the amount of the viscosity activation energy in the same temperature region.