The depletion of the world’s petroleum reserves, the increasing tension in the Middle East, and the increased environmental impact of conventional combustion engine powered automobiles, are leading to renewed interest in the uses of hydrogen.  TiFe hydrides, for example, are already used as storage tanks for stationary nonpolluting hydrogen internal combustion engines and nickel metal-hydride batteries (primarily using LaNi₅ ) are commonly used in a wide range of applications, most notably as power sources for portable electronic devices.  Key requirements for a hydrogen storage material include: (a) the ability to load a significant amount of hydrogen; (b) the ability to get the hydrogen into and out of the metal at reasonable values of pressure and temperature and within a reasonable time; and (c) the ability to repeat this cycle many times without degradation of the intermetallic alloy.  All of these features have been demonstrated, at least to a limited extent, in the Ti/Zr quasicrystals.   Hydrogenation cycles in these quasicrystals, however, lead to the irreversible formation of a crystalline hydride phase, which degrades the mechanical integrity of the samples and decreases the hydrogenation properties.  Recent work has shown that the TiHfNi rational approximants store hydrogen to similar levels, but are more resistant to the hydride formation.

The table below demonstrates that based on storage capacity alone, the TiZrNi quasicrystals are equal or even superior to materials currently used.

Notable Accomplishments include

• First measurements of the equilibrium vapor pressure in TiZrNi quasicrystals and related phases and computation of site occupation densities for the quasicrystal and the 1/1 crystal approximant phases.
• Development of  a new technique for evaluating the significance of the hydrogen-hydrogen interaction, demonstrating that it is significant in these systems.
• First measurements of equilibrium vapor pressure in TiHfNi 3/2 rational approximant and related metallic glass.  Results indicate similar local atomic structures in the two phases, supporting widely held belief that the local order in glasses is icosahedral.
• Demonstration of decreased formation of crystal hydride in TiHfNi rational approximant.
• In collaboration with N. Adolphi and A. McDowell , NMR measurements of hydrogenated quasicrystal – in agreement with site distribution determined from structural modeling and equilibrium vapor pressure measurements.  Large changes of NMR relaxation time with small changes of hydrogen suggests rapid fluctuations in the density of states.
• In collaboration with U. Köster , first measurements of equilibrium hydrogen vapor pressure for Zr_69.5 Al_7.5Ni₁₁Cu₁₂ glasses that crystallize to quasicrystals of the same composition.  Results for the two phases are very similar again suggesting that like the TiHfNi alloys, the glass and quasicrystal have similar local atomic order.