INVITED PAPER Developments in the Ni–Nb–Zr amorphous alloy membranes A review S. Sarker 1 • D. Chandra 1 • M. Hirscher 2 • M. Dolan 3 • D. Isheim 4 • J. Wermer 5 • D. Viano 3 • M. Baricco 6 • T. J. Udovic 7 • D. Grant 8 • O. Palumbo 9 • A. Paolone 9 • R. Cantelli 10 Received: 5 November 2015 / Accepted: 20 January 2016 Ó Springer-Verlag Berlin Heidelberg 2016 Abstract Most of the global H 2 production is derived from hydrocarbon-based fuels, and efficient H 2 /CO 2 sepa- ration is necessary to deliver a high-purity H 2 product. Hydrogen-selective alloy membranes are emerging as a viable alternative to traditional pressure swing adsorption processes as a means for H 2 /CO 2 separation. These mem- branes can be formed from a wide range of alloys, and those based on Pd are the closest to commercial deploy- ment. The high cost of Pd (USD *31,000 kg -1 ) is driving the development of less-expensive alternatives, including inexpensive amorphous (Ni 60 Nb 40 ) 100-x Zr x alloys. Amor- phous alloy membranes can be fabricated directly from the molten state into continuous ribbons via melt spinning and depending on the composition can exhibit relatively high hydrogen permeability between 473 and 673 K. Here we review recent developments in these low-cost membrane materials, especially with respect to permeation behavior, electrical transport properties, and understanding of local atomic order. To further understand the nature of these solids, atom probe tomography has been performed, revealing amorphous Nb-rich and Zr-rich clusters embed- ded in majority Ni matrix whose compositions deviated from the nominal overall composition of the membrane. 1 Introduction The bulk of global H 2 production still originates from the conversion of hydrocarbon fuels such as coal, crude oil, natural gas, and biomass, and the co-production of CO 2 necessitates a H 2 /CO 2 separation process to deliver H 2 of the desired purity to downstream processes [1, 2]. Pressure swing adsorption (PSA) is a reliable, established technique for this separation, but is less than ideal from an efficiency and size perspective. Alloy membranes offer the advantage of compact size and continuous separation, but are cur- rently limited to small-scale, niche applications. For example, crystalline Pd and Pd–Ag (100–200 lm thick- ness) membranes have been employed for several decades to obtain ultrapure H 2 [3–9]. The reported hydrogen selectivity and permeability of these membranes vary widely, but H 2 flux values in excess of 1 mol m -2 s -1 have been reported [10]. A limitation of Pd-based membranes is the potential for hydride formation under certain operating conditions, and this can lead to eventual failure of the membrane because of increased brittleness. The greatest barrier to further deployment of Pd membrane technology & D. Chandra dchandra@unr.edu 1 Materials Science and Engineering, University of Nevada, MS 388, Reno, NV 89557, USA 2 Max-Planck-Institut fu ¨r Intelligente Systeme, Heisenbergstrasse 3, 70569 Stuttgart, Germany 3 CSIRO, QCAT, Energy, 1 Technology Court, Pullenvale, QLD 4069, Australia 4 Materials Science and Engineering, Northwestern University, 2220 N. Campus Dr., Evanston, IL 60208, USA 5 Los Alamos National Laboratory, Los Alamos, NM 875451, USA 6 Department of Chemistry and NIS, University of Turin, Via P. Giura, 9, 10125 Turin, Italy 7 National Institute of Standards and Technology, Gaithersburg, MD 20899, USA 8 University of Nottingham, University Park, Nottingham NG7 2RD, UK 9 CNR-ISC, U.O.S. La Sapienza, Piazzale A. Moro 5, 00185 Rome, Italy 10 University of Rome, La Sapienza, 00185 Roma, Italy 123 Appl. Phys. A (2016)122:168 DOI 10.1007/s00339-016-9650-5