Abstract
Ni-Nb-Zr amorphous membranes, prepared by melt-spinning, show great potential for replacing crystalline Pd-based materials in the field of hydrogen purification to an ultrapure grade (>99.999%). In this study, we investigate the temperature evolution of the structure of an amorphous ribbon with the composition Ni32Nb28Zr30Cu10 (expressed in atom %) by means of XRD and DTA measurements. An abrupt structural expansion is induced between 240 and 300 °C by hydrogenation. This structural modification deeply modifies the hydrogen sorption properties of the membrane, which indeed shows a strong reduction of the hydrogen capacity above 270 °C.
Highlights
For purification of hydrogen to an ultrapure grade (>99.999%), crystalline Pd and Pd-Ag (100–200 μm thickness) membranes have been employed for several decades [1,2]
Reported that Ni-Zr-based alloys are stable and do not become brittle in the temperature range between 200 and 350 ◦ C while the hydrogen permeability of the Ni64 Zr36 sample is on the order of 10−9 mol·m−1 ·s−1 ·Pa−0.5 [14,15,16]
In the present work, we show that the two phases, at low and at high temperature, present different hydrogen sorption properties, with the lower temperature phase displaying a much higher value for the hydrogenation enthalpy
Summary
For purification of hydrogen to an ultrapure grade (>99.999%), crystalline Pd and Pd-Ag (100–200 μm thickness) membranes have been employed for several decades [1,2]. Amorphous alloys formed from a combination of Ni and one or more early transition metals show great potential for this application [12] Due their low cost and high selectivity, amorphous membranes have been largely investigated. Reported that Ni-Zr-based alloys are stable and do not become brittle in the temperature range between 200 and 350 ◦ C while the hydrogen permeability of the Ni64 Zr36 sample is on the order of 10−9 mol·m−1 ·s−1 ·Pa−0.5 [14,15,16]. 45 Zr50 is considered a key parameter for the potential use of these membranes; for alloy, the copper substitution increases the permeability significantly. In order to obtain materials with high permeability but low hydrogen embrittlement, knowledge. In correspondence with this structural modification, the hydrogen change and the membrane absorbs much hydrogen in the much high temperature regime thanhigh in the absorption properties change and the less membrane absorbs less hydrogen in the low temperature one. than in the low temperature one
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