Anjali Talekar

Amorphous Alloy Membranes Prepared by Melt-Spin methods for Long-Term use in Hydrogen Separation Applications

Amorphous Ni-based alloy membranes show great promise as inexpensive, hydrogenselective membrane materials. In this study, we developed membranes based on nonprecious Ni-Nb-Zr alloys by adjusting the alloying content and using additives. Several studies on crystallization of the amorphous ribbons, in-situ x-ray diffraction, SEM and TEM, hydrogen permeation, hydrogen solubility, hydrogen deuterium exchange, and electrochemical studies were conducted. An important part of the study was to completely eliminate Palladium coatings of the NiNbZr alloys by hydrogen heattreatment. The amorphous alloy (Ni0.6Nb0.4)80Zr20 membrane appears to be the best with high hydrogen permeability and good thermal stability.

Effect of Gaseous Impurities on Long-Term Thermal Cycling and Aging Properties of Complex Hydrides for Hydrogen Storage

Hydrogen is one of the alternate fuels for vehicular applications where the exhaust is mainly water vapor when used with either fuel cells or internal combustion engines. In the transportation sector, a proton exchange membrane (PEM) fuel cell, that electrochemically combines inputs of pure hydrogen and oxygen (from air), may be used to directly generate electricity for an electric motor drive with water vapor and heat produced as byproducts. However, hydrogen fuel cell technologies must be competitive in this venue with the ubiquitous internal combustion engine using gasoline and diesel fuels, both of which offer an established production and distribution infrastructure as well as a familiar and commonly accepted form of high density and stable energy storage. The United States Department of Energy (DOE) is addressing the standards that a hydrogen fuel system would have to meet as part of their FreedomCAR initiative. Conventionally, hydrogen is compressed in high pressure cylinders with obvious safety issues. The authors believe that hydrogen may be stored in metal hydrides at low pressures. Hydrides may be classified as (a) classical hydrides (heavy hydrides with low wt.%H), and (b) complex hydrides (light weight hydrides with high H-wt.%). In this study, the focus was on practical aspects of complex hydrides related to refilling hydrogen in vehicles at hydrogen gas stations, where one expects ppm levels of impurities. These gaseous impurities affect the performance of the complex hydrides as a medium for storing hydrogen. The main focus of the project was to understand the effect of trace element gases, mixed with hydrogen, on the long-term cycling and aging properties of complex hydrides of Li3N-H2. Another secondary aspect was to test complex hydrides developed by MHCoE partners. In addition, they also conducted thermodynamic and crystallographic research of these hydrides to understand the reaction pathways.