Reversible and irreversible hydrogen absorption in Ni67 − xCuxZr33 glasses monitored by in situ resistivity measurements

The process of hydrogen absorption and desorption are investigated in Ni67 − xCuxZr33 glassy alloys by in situ resistivity measurements. The cyclic charging and discharging process has been monitored by conventional DC method using a computer-controlled system, exposing the samples to hydrogen of 6 MPa pressure at 293, 328 and 373 K, respectively. Normalized resistivities as a function of charging and discharging times are compared for the first and repeated cycles. Separate samples, taken from specific points of cycling, were investigated by transmission electron microscopy (TEM) measurements. Hydrogen content (H/M ratio) was determined by weight measurements, and checked by gas chromatography, which is combined with an appropriate vacuum extraction and heating technique of the samples. A gradual hydrogen-induced phase separation could be detected on the samples by scanning transmission electron microscopy (STEM) with increasing number of the cycling.