Cobalt Phases in Co-Cu Mechanical Alloy and Their Thermal Behavior by X-ray Absorption Spectroscopy

摘要

The distribution of the magnetic phase in a nonmagnetic metallic matrix accounted for unique magnetic properties of metallic alloys. Herein, the structural properties of Co-Cu mechanical alloys with different atomic cobalt to copper ratios were investigated by X-Ray Absorption Spectroscopy (XAS). The results from X-Ray Absorption Near Edge Structure (XANES) analysis probed at Co K-edge energy revealed three independent cobalt-containing phases in all alloys. The metallic Co was found to be a major component whereas CoO and Co3O4 co-existed as minor phases and progressively increased with the initial cobalt to copper ratio. In addition, thermal behavior and thermal stability of the cobalt- containing phases in the alloy were studied by time-resolved XAS. The results indicated two characteristic phase transition temperatures at 280 degrees C and 400 degrees C. The former involved the phase transition from metallic Co to CoO whereas the latter was associated with the formation of Co3O4 at the expense of Co and CoO. The metallic Co phase in the absence Cu matrix significantly showed a different phase transition profile, suggesting the lower thermal stability of the Co phase. The present techniques provided insights into the structural and thermal properties of the Co-Cu alloy and would be applicable for bimetallic system in general.