engleski

Oxidation of molybdenum by low energy ion bombardment

We have studied the oxidation of pure molybdenum metal at room temperature (RT) by low-energy oxygen-ion bombardment, within an analytical ultrahigh vacuum chamber, using x-ray photoemission spectroscopy (XPS). In this paper, we provide a detailed characterization of pure Mo metal oxidation states and we compared it with the Mo oxidation in CoCrMo alloy. After thermal oxidation of pure metal at RT up to oxygen dose of 5000 L, the Mo 3d core-level photoemission spectra remained almost unchanged. This is in agreement with the previous studies of Mo oxidation that showed the thermal oxidation of Mo requires temperatures above 300°C. On the other hand, Mo oxidizes quite easily within the CoCrMo alloy by thermal oxidation. The XPS Mo 3d spectra recorded after the ion bombardment showed a complex structure consisting of molybdenum Mo4+, Mo5+ and Mo6+ oxidation states, proving that the ion bombardment is more efficient oxidation process for Mo than thermal oxidation. Our study showed that molybdenum oxidizes more efficiently in CoCrMo alloy compared to the pure Mo metal, which we attribute to the enhanced mobility and reactivity of oxygen atoms in alloy, compared to the pure Mo metal.

Molybdenum ; CoCrMo alloy ; ion-beam oxidation ; thermal oxidation ; x-ray photoelectron spectroscopy

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