Thesis (Ph. D. in Chemistry)--University of California, Berkeley, June 1958. / Includes bibliographical references (leaves 91-92).

The metal hydride used as hydrogen storage material has come into public notice. It is very important to understand the crystal structure and the permutation of hydrogen and the metal crystal structure of hydride for developing industrial hydrogen storage material. The tetrahedral formation of the atom intervals of titanium/zirconium alloys benefits the absorbing of hydrogen atoms. Especially under high temperature, the titanium/zirconium alloys have high affinity on hydrogen, and hydrogen atoms help to absorb within the titanium/zirconium alloys can spread and enter materials fast on the surface, this way will get uniform saturation solid solution. Therefore, we use hydrogen gas in the high-temperature gaseous phase to melt the titanium/zirconium alloys and observe the crystal structure and morphology of hydride precipitates with transmission electron microscopy. The research contents are as follows: (1) In Ti-H system, ageing of quenched specimens which contained the hydrides are found to have a face-centered tetragonal structure (£^-titanium hydride). Ageing of furnace-cooled specimens which contained the hydrides are found to have a face-centered cubic structure (£_-titanium hydride). (2) In Zr-H system, ageing of quenched specimens which contained the hydrides are found to have a face-centered tetragonal structure (£^-zirconium hydride). Ageing of furnace-cooled specimens which contained the grain-boundary hydrides are found to have a face-centered cubic structure (£_-zirconium hydride).

Abstract In order to make efficient hydrogen storage utilization as a fuel in fuel cell plant, there is need for its effective storage. Previous studies on hydrogen storage considered the hydrogen adsorption/ desorption in radial direction only which is one dimensional approach in this project, two dimensional computational model is implemented in CFD software to simulate the diffusion and heating of hydrogen in both radial and axial directions. The model consists of a system of partial differential equation (PDE) describing two-dimensional heat and mass transfer of hydrogen in porous matrix. Mathematical model was developed to simulate heat and mass transfer in a packed bed reactor with metal hydride as a material for hydrogen absorption and desorption. Importance of bed porosity radial distribution and correct equation for effective thermal conductivity is discussed.

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Zirconium alloys are susceptible to engineering problems associated with the uptake of hydrogen throughout their design lifetime in nuclear reactors. Understanding of hydrogen embrittlement associated with the precipitation of brittle hydride phases and a sub-critical crack growth mechanism known as Delayed Hydride Cracking (DHC) is required to provide the engineering justifications for safe reactor operation. The nature of bulk zirconium hydrides at low concentrations (< 100 wt. ppm) is subject to several contradictory descriptions in the literature associated with the stability and metastability of γ-phase zirconium hydride. Due to the differing volume expansions (12-17%) and crystallography between γ and δ hydride phases, it is suggested that the matrix yield strength may have an effect on the phase stability. The present work indicated that although yield strength can shift the phase stability, other factors such as microstructure and phase distribution can be as or more important. This suggests that small material differences are the reason for the literature discrepancies. DHC is characterised by the repeated precipitation, growth, fracture of brittle hydride phases and subsequent crack arrest in the ductile metal. DHC growth is associated primarily the ability of hydrogen to diffuse under a stress induced chemical potential towards a stress raiser. Knowledge of the factors controlling DHC are paramount in being able to appropriately describe DHC for engineering purposes. Most studies characterise DHC upon cooling to the test temperature. DHC upon heating has not been extensively studied and the mechanism by which it occurs is somewhat controversial in the literature. This work shows that previous thermo-mechanical processing of hydrided zirconium can have a significant effect on the dissolution behaviour of the bulk hydride upon heating. DHC tests with γ-quenched, furnace cooled-δ and reoriented bulk hydrides upon heating and DHC upon cooling suggest that the amount of hydrogen in solution is the primary factor controlling the occurrence of DHC and consistent with the postulation that the stress induced chemical potential is the driving force for DHC. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2012-01-24 06:14:14.152