Effect of surface and bulk properties on hydrogen absorption and desorption in NiZr metallic glasses

After previous examinations in the field of Ni-Zr based hydrogen absorbing glassy alloys, this paper details some surface and bulk processes, which have strong influence in H-charging and discharging properties. It is a usual problem with hydrogen storing materials that imperfect surface and bulk preparation (activation) hinders free movement of hydrogen, thus we can use only a small proportion of theoretical storing capacity. The surface oxide layer is usually a fundamental point: it is often impermeable for hydrogen. It is also true for Ni-Zr based glassy alloys, so the surface of samples has to be activated first by etching in an adequate acetic solution. Another restricting process is the diffusion of H-atoms in bulk metal. This problem is also examined and discussed together with some special measurements that made us able to study the above-mentioned effects easily.