Surface characteristic of Ni-based amorphous alloy membrane for hydrogen permeation

The production of high purity hydrogen gas is an important technical issue for future energy and environmental problem. The pure hydrogen is the ideal fuel in terms of fuel-cell performance. There have been many investigations on the hydrogen permeation of Pd-coated membrane of amorphous alloys. The purpose of this research is to characterize the surface such as roughness and morphology of surface layer of Ni-based amorphous alloy membrane by atomic force microscopy (AFM). The ribbon of Ni-Nb-Ta amorphous alloy was produced by a single-roller melt-spinning technique. The surface characteristic of the amorphous alloy membrane was discussed in view of the hydrogen permeation behavior. From the 3-dimensional AFM images, a lot of hole was observed on the surface of the amorphous alloy membrane produced in air atmosphere. But, a lot of protrusion were observed in the membrane produced in vacuum due to the selective growth on the high oxygen-affinity element of the amorphous alloy. The average roughness of the membrane produced in air atmosphere and vacuum was measured to be 0.359 and 0.263nm, respectively. Therefore, it was considered that it would be suitable to produce the amorphous alloy membrane in vacuum.