Hydrogen-induced phase separation in amorphousCu0.5Ti0.5alloys. I. Room-temperature experiments

The influence of hydrogen on the structure of an amorphous ${\mathrm{Cu}}_{0.5}$ ${\mathrm{Ti}}_{0.5}$ alloy has been studied by means of x-ray and neutron scattering. These experiments include large-angle x-ray and neutron scattering and small-angle neutron scattering with hydrogen-deuterium substitution. The results indicate that large hydrogen contents (hydrogen-to-metal ratio of 0.84) induce a phase separation into Cu and ${\mathrm{TiH}}_{\mathrm{x}}$ regions on a scale of about 10–15 Å. Experiments on samples loaded with hydrogen by electrolysis or from the gas phase show that such a phase separation does not depend on the method of hydrogen loading. The results of a computer simulation with nearest-neighbor Cu-Ti permutations reproduce the main features of the diffraction data and confirm the large change of chemical ordering between Cu and Ti atoms upon hydrogen absorption.