Oxygen-18 Diffusion in Surface Defects on MgO as Revealed by Proton Activation
A study of the effect of surface defects on the self-diffusion of oxygen in MgO is reported. The technique involves exchange with oxygen-18 enriched gas followed by proton bombardment to yield the radioisotope, fluorine-18. This may be treated as a normal radioactive tracer. The penetration distribution of the oxygen isotope is indicated by autoradiography. Preferential diffusion of oxygen down bicrystal grain boundaries is definitely proven. Dislocations introduced by cold-working are found to contribute to the overall rate of oxygen diffusion. Surface fractures are shown to be important channels for the rapid movement of oxygen. The implications of these findings are discussed.
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