Characteristics of Co3O4 and cobalt nanostructured microspheres: Morphology, structure, reduction process, and magnetic properties

Nanostructured magnetic cobalt microspheres were synthesized using a two-stage method. First, nanostructured cobalt oxide Co3O4 microspheres were produced by ultrasonic spray pyrolysis at different temperatures from 800 to 1100C. Second, the nanostructured powders obtained were reduced to metal cobalt in an hydrogen atmosphere at different temperatures from 220 to 350C. In this study the evolution of the morphology from Co3O4 nanostructured microspheres to nanostructured Co, resulting from the Co3O4 reduction process, and the structure of metal cobalt, were investigated. It was found that the metal cobalt agglomerates have the same shape and mean diameter (similar to 1,5 mu m) as those of the cobalt oxide, Co3O4. The amount of Co microspheres with smaller diameters decreased with increasing reduction temperature. Also, the beta-Co content increased with increasing reduction temperature.