Relaxation phenomena of ultrasonic waves on molten alkali silicates

Abstract

The temperature and the frequency dependencies of velocities and absorption coefficients of ultrasonic waves have been measured on molten alkali silicates (33(mol%)M 2O-67SiO 2 (M = Na and K)) using the pulse transmission technique. The velocities and the absorption coefficients have been determined by the Fourier transform of ultrasonic pulses. It has been found that the velocities, c, increases with decreasing temperature, while the absorption per wavelength, αγ, increases and then decreases with decreasing temperature. It has also been found that the c and αγ values are identical irrespective of frequencies above ca. 1 400 K for 33Na 2O·67SiO 2 and ca. 1 500 K for 33K 2O·67SiO 2, respectively, while dispersion, i.e., frequency dependency, appears below these temperatures. The dispersions of acoustic properties have been successfully interpreted using a structural relaxation model. © 2012 ISIJ.