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The properties of four hydride-forming materials have been investigated to determinetheir applicability for use in a process to separate hydrogen isotopes from inert gases. These materials are Zr0.8Ti0.2Ni, Zr0.65Ti0.35Co, NdCo3 and ErFe2. The properties investigated while surveying these materials include ease of activation, isotherm characteristics, kinetics, cycling stability and oxygen stability. The results of the survey indicate NdCo3 to be the hydride former of choice for use in the inert gas separation process. It is the most easily activated and has the most favorable isotherm characteristics (the largest usable capacity, flat plateaux, small hysteresis and negligible heel) as well as the fastest absorption kinetics of the materials tested. NdCo3 also has good cycling and oxygen stability. As with most intermetallic alloys, NdCo3 decrepitates into a fine powder after only a few sorption cycles in hydrogen and therefore must be consolidated in order to be used in the fixed bed absorber envisioned for the inert gas separation process. Consolidation was achieved through support of the NdCo3 in a sinter-bonded aluminum matrix. Stable compacts of NdCo3 have been made consisting of 40 wt.% Al in NdCo3 pellets, pressed at 186 MPa and sintered under vacuum for 2 h at 450°C. These compacts retained the full absorptive capacity of NdCo3 and remained 99 wt.% intact after 15 sorption cycles in hydrogen.
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