The thermal oxidation of ion-implanted zirconium

The thermal oxidation of polycrystalline zirconium implanted with 21 different ion species has been studied by using the nuclear reaction 16 O( d , p 1 ) 17 O. A very good agreement has been found between the oxidation kinetics of unimplanted zirconium as determined by the nuclear reaction and those previously measured gravimetrically. Oxidation kinetics show a time dependence which is cubic or parabolic depending upon the surface treatment before oxidation. Ion implantation produces significant changes in oxidation rate but the time dependence remains the same. A strong correlation has been found between the behaviour of ion implanted systems and that reported for binary alloys, confirming the hypothesis that the ionic size of the additive is the major parameter governing the influence upon the oxidation of zirconium. The implanted species which inhibit oxidation possess ionic radii lying between 80% and 100% of that of Zr 4+ . An explanation of their beneficial effect based on an increase of the plasticity of the growing oxide is presented.