Ultrasmall Angle X-ray Scattering (USAXS), Wide Angle X-ray Scattering (WAXS), and Raman Studies on the Complex Metal Hydride NaAlH₄

This research seeks to understand the role of ScCl₃, ZrCl₄, and VCl₃ catalysts in NaAlH₄ by examining these hydrides at multiple length scales using an X-ray scattering instrument which is capable of simultaneously measuring scattering wave vector, Q, of 0.0001Å^-1 to 6.0 Å^-1. Isothermal studies were performed at 30^oC, 65^oC, 100^oC, 135^oC, and 170^oC. Results show an increased surface area as temperature increased for all doped samples (and milled). Pore size remains relatively constant with temperature. Doped samples show 70-80nm pore sizes while milled is smaller. At 135^oC, there is little change in surface area or radius of gyration (R_g) for all samples. The number of pores in the 50-70nm size range increases with both temperature (T) and time (t). Raman and WAXS data show no product phase and so the changes in pore structure are occuring before measurable hydrogen desorption occurs.