Fabrication of alumina-coated cobalt microspheres

Cobalt metal or cobalt oxide microspheres could be used as radioactive tracers, for example in material dispersion experiments. For such applications each microsphere should ideally be enclosed in a strong, non-leachable shell made from a material which does not activate significantly when the microspheres are neutron-irradiated to produce cobalt-60. This Note reports on the development at Lucas Heights of alumina-coated cobalt metal microspheres, alumina having been chosen as a cheap, stable, sinterable coating material with no neutron activation problem. (J.R.)