Template-free synthesis and characterization of dendritic cobalt microstructures by hydrazine reduction route

Novel three-dimensional (3D) cobalt dendritic microstructures with size ranging from 8 to 15 μm were successfully prepared under mild conditions. The synthetic process involves the chemical reduction of cobalt ions with hydrazine as reductant, and no surfactant or external magnetic force was employed. The cobalt dendrites were constructed by a main trunk and highly ordered branches distributed on both sides. The angles between the trunk and side branch are close to 60°, and the side branch can serve as the center for the further growth of smaller dendrites. The concentrations of initial cobalt salt and sodium hydroxide were found to be crucial to the formation of such dendrites. A possible growth process was proposed based on the controlled experiments. Compared to the bulk cobalt, the dendritic cobalt microstructures exhibited a decreased saturation magnetization value of 145 emu/g but an enhanced coercivity of 208 Oe due to their anisotropic dendritic structure.