Coupled Nucleation, Nanostructure Formation and Hydrogen Storage in Metallic Glasses and Quasicrystals

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TECHNICAL: Nucleation processes are more complex than often assumed, and proper account must be taken of the coupling between the stochastic fluxes of long-range diffusion and interfacial attachment. Recent studies, including those by PI indicate that order-parameter fluctuations such as those that underlie chemical, structural, and magnetic ordering can also couple with the order parameter fluctuations associated with nucleation. In addition to their basic interest, these results demonstrate that enhanced nanostructural refinement is possible by an improved understanding of this nucleation behavior. To better understand coupled process in nucleation and their potential for improved microstructure refinement, this project will determine the local atomic structure of select Ti/Zr-based, Co/Fe-based and Mg-based metallic glasses by wide and small angle x-ray diffraction; high resolution, energy filtered and fluctuation transmission electron microscopy; EXAFS; and atom probe measurements. This data will be correlated with glass formation and the crystallization kinetics, determined by differential scanning calorimetry and electrical resistivity measurements and by TEM based studies of time-dependent nucleation. Research will also continue to probe the influence of diffusion on nucleation behavior. The cycling characteristics and origin of the high-pressure plateau will be determined for bulk and nanostructured i(TiZrNi) to evaluate its potential usefulness as a hydrogen storage material. NON-TECHNICAL: The results from these studies will be of broad basic and technological interest including hydrogen storage, a deeper understanding of phase transitions and improved control over nanostructure production. The Ti/Zr quasicrystals could help facilitate the transition to a hydrogen-based transportation system. The research has a significant educational importance, providing training to graduate and undergraduate students, and experience to local high school students in the theoretical and experimental methods of materials science. PI and his graduate students will give presentations of research results to the students and teachers and work directly with the students to expose them to the possibilities for scientific careers.