Robert C. Bowman

A study of the properties and NMR spectra of amorphous and crystalline ZrPd hydrides

Abstract Results of a study of the hydrides of Zr65Pd35 and Zr67Pd33 metallic glasses are presented. It was found that these alloys absorb hydrogen at temperatures ranging from 150°C to 225°C to a final hydrogen concentration of Zr67Pd33H≈95. X-ray diffraction, density measurements, and measurements of electrical resistivity and superconducting transition temperature were carried out on these samples. Results of NMR studies of amorphous Zr67Pd33H≈95 alloys as well as the corresponding single-phase crystalline hydrides Zr2PdH1.94 and Zr2PdH2.90 are also reported. The amorphous hydrides exhibit enhanced hydrogen mobility, compared with the corresponding crystalline hydrides, as determined by motional line narrowing (T 2 ∗ measurements ) of the NMR spectra. The apparent activation energy for diffusion in the amorphous hydride was studied by both T 2 ∗ and T1π measurements over an extended temperature range and found to depend strongly on temperature. Proton Knight shift and spin-lattice relaxation time measurements suggest that the electronic density of states at EF is significantly lower in the amorphous hydride than in the corresponding crystalline hydride.

Roles of Hydrogen in Space Explorations

The various roles of hydrogen in space technology are identified and discussed. The preeminent position of hydrogen as rocket fuel in launch vehicles is explained and illustrated for the NASA Space Shuttle. The history of hydrogen in launching space vehicles is also briefly summarized. The cryogenic aspects of hydrogen for cooling instruments during flight missions are covered for several past and current systems. The technology of Nickel‐Hydrogen batteries is covered. The storage of cryogenic hydrogen to operate fuel cells and to provide potable water is described for the NASA Apollo and Shuttle Missions. Other less well‐known applications of hydrogen and metal hydrides such as gas gap heat switches, fueling hypersonic scramjet flights to Mach 10 speeds, in‐situ resource utilization on lunar or Martian surfaces, and providing ultrapure reference hydrogen to scientific instruments are also described. Finally, some possible future roles for hydrogen in space exploration are identified.

Magnetic Susceptibility and Proton NMR Study of TiCr1.8Hx

The electronic properties of the hexagonal (C-14) and cubic (C-15) allotropes of the TiCr1.8+0.1/H2 system have been examined via magnetic susceptibility and proton NMR studies. The results indicate an increase in N(EF), the electron density of states at the Fermi level, with increasing H/M for both allotropes; the trend extends into the α′-hydride phase. The results suggest a basis for thermodynamic anomalies reported for the solution of hydrogen in TiCr1.8.