Hydrogen Phase Behavior in Thin-Film Metals

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

9982520 Heuser This program has been designed to provide a comprehensive set of experimental and simulation data of hydrogen in thin metal films. The program addresses all aspects of hydrogen phase behavior in thin film metals, building on recent investigations of hydrogen-metal systems. Neutron scattering techniques with superior sensitivity to hydrogen in metal lattices are employed to measure the pressure-composition-temperature or PCT behavior, elastic response, solute depth profile, and precipitation morphology in thin-film geometry. X-ray diffraction analysis is used to determine lattice strain and coherency loss. Transmission electron microscopy analysis characterizes dislocation substructure. Numerical simulations model lattice expansion, solute segregation, substrate-film interactions, and precipitation morphology. The systems chosen for this study include model metals, such as epitaxial Pd and Nb, and more application-specific systems, such as Pd alloys and rare earth depositions. The results are expected to lead to a more complete understanding of fundamental properties of hydrogen-metal systems. %%% Many hydrogen-related applications have been identified for thin metal films, including hydrogen sensors, battery electrodes, and switchable mirrors. The development of thin metal films for industrial applications has been a motivating factor in many recent investigations of hydrogen effects. Careful studies of the relationship between film PCT behavior, the elastic response, and the lattice strain state are needed to advance understanding of hydrogen-thin metal film systems. In addition, a measurement of hydride precipitation morphology in thin film geometry has never been made. This measurement will be made in single crystal (epitaxial) Pd films and compared to measurements of the hydride morphology in bulk single crystal Pd. ***