Crystalline Pd/Pd-Ag membranes are widely used for hydrogen separation from CO2 and other gases in power generation applications. Hydrogen-selective alloy membranes are emerging as a viable alternative to traditional pressure swing absorption processes as a means for H2/CO2 separation. Inexpensive Ni-based amorphous alloys are being developed to replace these noble metal alloy membranes. We are studying amorphous ribbons of (Ni0.60Nb0.40)100-xZrx (x=0-30 at %) fabricated by melt-spinning method that exhibit relatively high permeabilities of hydrogen between 200-400oC, however, the mechanism of permeation and the nature of the local atomic order of the amorphous membranes are shown here). Atom probe tomography (APT) revealed Nb-rich (5-6 nm) and Zr-rich (~ 2 nm) clusters embedded in a Ni-rich matrix. Atom dynamics of amorphous membranes, determined by synchrotron x-ray photon correlation spectroscopy (XPCS) at ESRF, revealed a dramatic reversible acceleration of atomic motion under hydrogen atmosphere at low temperatures, suggesting hydrogen absorption and desorption are mainly from these icosahedra residing in the clusters. Neutron vibrational spectroscopy (NVS) results revealed hydrogen positions inside Zr4, Nb4 distorted tetrahedral sides. Nearest neighbor distance and short range order (~1.8 nm) in these amorphous alloys as determined by Neutron Total scattering (HIPD Our DFT simulation reveals the icosahedra structure and cluster information which match with APT and HIPD results. Hydrogen permeation, thermodynamics of hydrogenation, kinetics of crystallization, atomic dynamics studied by XPCS, inelastic neutron scattering, and atom tomography results are presented.

Amorphous alloy membranes for hydrogen separation from CO2 and other gases

255th National Meeting (2018)

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