Temperature Dependence of the Elastic Modulus of (Ni_0.6Nb_0.4)_1−xZr_x Membranes: Effects of Thermal Treatments and Hydrogenation

Amorphous (Ni_0.6Nb_0.4)_1−xZr_x 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 (Ni_0.6Nb_0.4)_1−xZr_x-H membanes.