Search

The reaction of hydrogen and deuterium with palladium has been investigated using pressure-composition-temperature (PCT) measurements at very low hydrogen and deuterium concentrations in palladium powder having a surface area of 1.03 m 2 g −1 to determine the nature of a surface “film” that affects the diffusional uptake of hydrogen by palladium. PCT isotherms measured on the palladium powder indicated the presence of a two-phase region having an equilibrium pressure of less than 0.5 Pa and a stoichiometry of approximately one monolayer at 299 K. At 421 K, the stoichiometry had decreased by half with a twofold increase in the equilibrium pressure. These isotherms are presented in terms of the experimental PCT curves and those calculated for the “surface hydride”. The equilibrium pressure for deuterium was lower than that for hydrogen for this “surface hydride”, having an Einstein temperature estimated to be 1600 K.

The radiation-induced conversion of para to orthohydrogen was investigated at pressures between 150 and 2200 psig (1 to 15 x 10/sup 6/ N/meter/ sup 2/) at three temperatures: 77 deg K (LN/sub 2/), 200 deg K (dry ice), and 300 deg K (ambient). Two radiation dose levels were studied: gamma rays only at 8 x 10/sup 6/ rads and a combination of 5 x 10/sup 14/ n/cm/sup 2/ E> 1 MeV, plus gamma rays at 8 x 10/sup 5/ rads. The conversion at LN/sub 2/ temperature was nearly zero in all cases. (auth)

Booth and Llewellyn determined the crystal structure of PETN in 1947. Their structure, refined by Trotter in 1963, agrees essentially with ours, which was constructed with new intensity data taken using a Picker FACS-I computer-controlled diffractometer. Our refinement located the hydrogen atoms with reasonably accuracy because our diffractometer is more sensitive than the film data of the earlier workers. A powder neutron diffraction pattern of deuterated PETN was taken on the diffractometer at the Omega West Reactor at the Los Alamos Scientific Laboratory. These intensity data were refined using the Rietveld Profile Analysis program as modified by R. Von Dreele of Arizona State University. We discuss possible explanations of systematic differences between the interatomic distances and angles determined by x-ray diffraction and those determined by neutron diffraction.