Identification of liquid mixtures for ultrasonic applications

Liquid mixtures and solutions are sought that exhibit improved properties for ultrasonic applications such as acoustic microscopy and stimulated Brillouin scattering. Both these applications require liquid media with low acoustic velocity and attenuation. A thermodynamic theory is used to predict the acoustic velocity of a mixture from the heat of mixing; consulting a table of heats of mixing then provides a way of identifying candidate liquid mixtures. Acoustic attenuation is not predicted and must be found experimentally. The method works well for liquid solutes, but is shown to be ineffective for solid solutes since the lattice energy of the solute dominates the heat of mixing. An optical heterodyne technique was used to measure the acoustic properties of candidate mixtures in the frequency range 0.2–1.2 GHz. New acoustic data are reported for these mixtures: aqueous cetyl pyridinium chloride (a detergent solid), aqueous ethylene carbonate, and ethyl acetate in carbon disulphide. No mixtures were found...