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The time evolution of the hydrogen absorption of melt-quenched Zr50Ni50 amorphous alloy ribbons was investigated for the as-quenched state and after a relaxation heat treatment. Hydriding was performed from the gas phase at 200 °C and 35 atm H2 gas pressure for charging times up to t = 48 h. The absorption process was monitored by measuring the mass increase, the thermoelectric power and the magnetization of the hydrided ribbons. For both the as-quenched and relaxed state, homogeneously hydrided ribbons could only be obtained at small ( H M ) and high ( H M ≈ 1 ) hydrogen contents. The maximum amount of absorbed hydrogen was found to be the same for both states; however, the hydrogen absorption process in the relaxed ribbons required considerably longer times than for the as-quenched state. As in our previous study of a Zr47.5Ni52.5 metallic glass, the magnetization measurements indicated also for the present alloy the occurrence of a phase separation process leading to the development of strongly magnetic nickel-rich clusters for long charging times.

The influence of hydrogen on some physical properties and on the micro-structure of a nearly equiatomic, melt-quenched NiZr amorphous alloy was investigated. Hydrogen absorption from the gas phase at 190 °C and 35–40 atm pressure was measured by weight as a function of the charging time. Considerable hydrogen absorption occurred only for charging times around 10 h and was completed within a few hours. The hydrogen content remained constant for a hydrogen-to-metal ratio of about one for prolonged charging. The room-temperature thermopower changed considerably upon hydriding and a local thermopower probe revealed that the activation time varies considerably along the ribbon length. It was found that, during further heat treatment in a hydrogen gas atmosphere after a hydrogen-to-metal ratio of approximately one was reached, the magnetic state of the amorphous NiZr samples changed progressively from paramagnetic to superparamagnetic. The density and size of the magnetic clusters, which were nickel-rich segregations induced by the hydriding process, were determined by magnetic and scanning transmission electron microscopic measurements. After desorbing hydrogen at elevated temperatures, magnetic measurements indicated the disappearance of the superparamagnetic clusters.

The proton rotating-frame spin lattice relaxation time T1r has been measured in (Ni0.5Zr0.5)0.95P0.05H0.54 and (Ni0.5Zr0.5)Po0.07H0.58 amorphous alloys in the temperature range 140–370 K. A single-exponential relaxation decay was obtained from 200 to 370 K only. The experimental data above 200 K were interpreted on the basis of a model involving diffusion of the hydrogen atoms. It is demonstrated that, by using a gaussian distribution of diffusion activation energies about a temperature independent mean energy E a = 0.32 eV atom−1 and a full width at half maximum ΔE = 0.07 eV, the temperature dependence of T1r can be well fitted in the 200–370 K range. These values are compared with relevant hydrogen diffusion data from the literature on other amorphous alloys

The thermoelectric power and resistance of (Zr48.5Ni51.5)99.3P0.7-H metallic glasses were measured. The thermoelectric power decreases from S ≈ 2 μV K−1 at zero hydrogen-to-metal ratio (HM = 0) to a negative value (S ≈ −2 μV K−1) at a hydrogen-to-metal ratio of 0.7 (HM = 0.7). These results show the high sensitivity of the thermoelectric power to hydrogen concentration and are consistent with the Mott model.