287954 Hydrogen Permeability, Thermal Stability and Mechanical Strength of Melt-Spun (Ni1-xNbx)80Zr20 (for x = 0.3 to 0.6) Amorphous Alloy Membranes

Tuesday, October 30, 2012: 4:05 PM
402 (Convention Center )
Dhanesh Chandra1, Sang-Mun Kim2, Wen-Ming Chien1, Narendra Kumar Pal2, Stephen N. Paglieri3, Michael D. Dolan4 and Ted Flanagan5, (1)Chemical and Materials Engineering, University of Nevada, Reno, Reno, NV, (2)University of Nevada, Reno, Reno, NV, (3)TDA Research, Inc., Wheat Ridge, CO, (4)Energy Technology, CSIRO, Pullenvale, Australia, (5)The University of Vermont

Amorphous Ni-based alloys are inexpensive hydrogen-selective membrane materials. One of the main barriers to the greater commercial use of these materials is their tendency to absorb hydrogen and embrittle, a process which decreases strength and causes membrane failure. The material also has a tendency to crystallize during a long-term operation at elevated temperatures,

a process which decreases both strength and hydrogen permeability. In this study, the hydrogen permeability and solubility of a series of (Ni1-xNbx)80Zr20(for x = 0.3 to 0.6) amorphous alloy membranes was studied. Amorphous membrane ribbons with thicknesses of 40-60 µm were fabricated by melt spinning and coated with a thin (500 nm) layer of Pd surface catalyst by magnetron sputtering.

The hydrogen permeation properties of the membranes were investigated over the 350-450°C temperature range at different hydrogen partial pressures. The effect of Ni concentration on the hydrogen permeability and the thermal stability was also investigated; the hydrogen permeability decreases with the addition of Ni.

The activation energy of crystallization and the crystallization mechanism for binary Ni-Zr alloys were determined using the Johnson-Mehl-Avrami (JMA) equation. The Kissinger and Ozawa methods were applied to the non-isothermal kinetics derived from the heating rate dependence of the crystallization temperature.

The glass transition and crystallization kinetics of melt-spun Ni60Nb20Zr20 amorphous alloy ribbons have been studied under non-isothermal and isothermal conditions using differential scanning calorimetry (DSC). The activation energies of crystallization, Ex, were determined to be 499.5 kJ/mol and 488.6 kJ/mol using the Kissinger and Ozawa equations, respectively. The Johnson–Mehl–Avrami equation has also been applied to the isothermal kinetics indicating a diffusion-controlled three-dimensional growth mechanism. In addition, the inter-metallic phases and morphology after membrane testing have been identified by X-ray diffraction (XRD) and scanning electron microscope (SEM).

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See more of this Session: Membranes for Hydrogen Purification II
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