A resonant ultrasound spectroscopy study of novel materials: Nanocrystals, quasicrystals, and hydrogen-storage alloys

The experimental technique Resonant Ultrasound Spectroscopy (RUS) has been used to study the elastic properties and ultrasonic loss of several novel materials: a nanocrystalline form of palladium, a quasicrystal, a Laves-phase C15 cubic material that undergoes a Martensitic phase transition when cooled, and a random alloy. Resonant Ultrasound Spectroscopy (RUS) is an ideal technique for the determination of the elastic properties of these types of materials since RUS is non-destructive and can work with very small sample sizes.; Nanocrystalline materials have average grain sizes of 100 nm or less. The reduced grain size leads to physical properties that are different than the properties of the coarser grained forms of the same chemical composition. The elastic constants of nanocrystalline palladium (nc-Pd) and silicon-stabilized nanocrystalline palladium (nc-PdSi) were measured in the temperature range 4-300K.; Quasicrystals are materials with an aperiodic structure, but which display perfect long-range order. RUS was used to measure the elastic constants of an icosahedral Ti39.5Zr39.5Ni21 quasicrystal over the temperature range 3-292K.; Laves-phase alloys are the largest subgroup of the topologically close-packed materials, and are characterized by low densities and high melting points. The Laves-phase C15 (cubic) materials can absorb hydrogen. The temperature dependence of the elastic constants of polycrystalline ZrV2 was measured in the temperature range 100-300 K using the RUS technique.; Random alloys are metallic compounds which do not exhibit chemical ordering of their component atoms; any lattice position may be inhabited by any of the chemical species comprising the compound. The random alloy discussed in this study, Ta0.33V0.67, can absorb considerable amounts of hydrogen and the disordered nature of the local atomic environments leads to differences in the elastic properties. In this study, the temperature dependence and ultrasonic loss for a random alloy with the same chemical composition as the Laves-phase C15 TaV2 compound was measured in the temperature range 5-300 K using the RUS technique, and compared to an earlier study of TaV2.