Abstract
Amorphous (Ni0.6Nb0.4)1−xZrx membranes were investigated by means of X-ray diffraction, thermogravimetry, differential thermal analysis and tensile modulus measurements. Crystallization occurs only above 673 K, and even after hydrogenation the membranes retain their mainly amorphous nature. However, after exposure to gaseous hydrogen, the temperature dependence of the tensile modulus, M, displays large variations. The modulus of the hydrogen reacted membrane is higher with respect to the pristine samples in the temperature range between 298 K and 423 K. Moreover, a sharp drop in M is observed upon heating to approximately 473 K, well below the glass transition temperature of these glasses. We propose that the changes in the moduli as a function of temperature on the hydrogenated samples are due to the formation of nanocrystalline phases of Zr hydrides in (Ni0.6Nb0.4)1−xZrx-H membanes.
Highlights
Alloy membranes with hydrogen selective properties have broad technological applications in the field of hydrogen production and purification [1,2,3]
The embrittlement of the samples with or without hydrogen is heavily influenced by their elastic properties, in this paper we investigate the changes of the elastic modulus of (Ni0.6Nb0.4)1−xZrx membranes induced by thermal treatments and hydrogenation
It should be noted that the DSC or Differential thermal analysis (DTA) can detect first order phase transitions and measure latent heats of phase transitions, but are not well suited to detect phase transitions of the second or higher order; for these Dynamical Mechanical analysis (DMA) measurements are critical
Summary
Alloy membranes with hydrogen selective properties have broad technological applications in the field of hydrogen production and purification [1,2,3]. Thin, crystalline, Pd-based membranes are used for the purification of hydrogen due to their high permeability to hydrogen Pd75Ag25) and selectivity [4]. The operating temperatures of these membranes are higher than. K. Palladium, is an expensive and scarce element, inexpensive and abundantly available alloys are being investigated as a replacement. Amorphous alloy membranes show promising properties [5], such as excellent mechanical strength, high thermal stability and soft magnetic properties [6,7,8]. A promising class of amorphous alloy membranes are the Ni-Zr or Ni-Nb-Zr ones.
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