| Popis: |
Ultrasonic velocity and absorption measurements have been carried out for several hydrate melt systems, including zinc nitrate, zinc chloride, and calcium nitrate, as functions of water content and temperature (extending into the supercooled region). Hypersonic velocity and absorption data have been obtained from Bril1ouin scattering measurements at 5145 A with an Argon ion laser and a piezoelectric scanning Fabry‐Perot interferometer. These data indicate a distribution of relaxation times for all of these hydrates rather than the single relaxation reported in some of the literature. Both the shear and volume viscosities relax. The Brillouin and ultrasonic data do not provide any evidence of temporal relaxation. In the calcium nitrate melts, replacement of protons by deuterium has virtually no effect on the ultrasonic or Brillouin scattering data, which indicate that the breaking of hydrogen bonds is not a critical factor. The viscoelastitc relaxation in these melts involves the disruption of relatively strong ion‐ion and ion‐water bonds and the reorientation of constituent anisotropic groups. Further information concerning reorientation effects has been obtained from the depolarized Rayleigh component. [Research supported by the Office of Naval Research, NSF, and NATO.] |
