THE OXIDATION OF AMORPHOUS ZR-BASE BINARY-ALLOYS IN AIR

The oxidation tendency of amorphous Zr65M35 (M = Fe, Co, Ni, Cu, Rh, P d or Au) binary alloys at 573 K in air was found to have a close relat ion with the atomic size of Zr and M elements. The amorphous Zr65M35 a lloys containing Au or Pd with atomic sizes larger than 0.135 nm have a very high oxidation tendency and the resulting oxidized structure co nsists of finely mixed phases consisting of ZrO2 + Au or ZrO2 + Pd. Th e oxidation of the other amorphous Zr-M alloys containing Fe, Co, Ni, Cu or Rh with atomic sizes smaller than 0.135 nm is very sluggish and the amorphous phase remains almost unchanged. The oxidation at room te mperature takes place only for M = Cu and Au and no distinct oxidation is recognized for the other M elements even after aging for several y ears. Furthermore, the oxidation tendency for the Au- or Cu-containing alloys has a strong compositional dependence and becomes significant with increasing M content. Production of finely mixed materials consis ting of ZrO2 + Au, ZrO2 + Cu or ZrO2 + Pd produced by oxidation is ver y attractive as a new synthesis method because of the achievement of u niform dispersion of ultrafine Au, Cu or Pd particles.