Influence of Oxidation on Surface Structure and Chemical Composition of Amorphous Ni₆₅Nb₃₅ Alloy

Variation of surface morphology and chemical composition of amorphous Ni₆₅Nb₃₅ alloy in the treatments under different conditions of surface oxidation have been investigated using Scanning Election Microscopy （SEM） and X-ray Photoelectron Spectroscopy （XPS）.The surface experienced a gentle oxidation at room temperature exhibited a pronounced niobium rich in respect to the bulk of the alloy, and the surface atomic ratio of Ni/Nb was 0.04, as calculated from the XPS data. An betment with 0.1 MPa oxygen at elevated temperature, however, gave rise to a dramatic reversion in the surface composition. After the exposure in oxygen at 673K, the surface appeared to be covered with metallic nickel and NiO,as evidenced by the results of XPS and the aloud ratio of surface Ni to Nb reached as high as 13.5. Different oxidation mechanisms concerning the alteration of the affinities of Ni and Nb to oxygen in the different temperature ranges have been suggestal.