Variations of Surface Morphology and Composition of Amorphous Ni-Zr Alloy under Drastic Oxidation Condition

The variations of surface morphology and chemical composition of Ni₂₄Zr₇₆ and Ni₃₆Zr₆₄ have been investigated before and after a drastic oxidation（in 5×10⁴Pa oxygen gas and heated up to 250℃～300℃）by XPS,UPS,ISS and SEM.XPS results show that the zirconium on both of the two amorphous alloy surfaces has been completely oxidized to ZrO₂. The oxidation of Ni in amorphous Ni₂₄Zr₇₆ alloy has not been observed,while a small amount of Ni has been oxidized to nickel oxides in Ni₃₆Zr₆₄ .A heavy Zrenrichment has been observed on the surface upon oxidation of the alloys.It is shown that both the formation of zirconium oxides and a movement of Ni atoms through Zratoms（but not ions） can be attributed to the surfce segration.It is also shown that there is a competition between the processes of Ni oxidation and Ni migration to the bulk.Heating the oxidized alloys to 500℃ can cause part of the oxides to dissociate,leaving oertain amounts of metal Zr or even Nion the surface.