Abstract
Sub-micrometric Co fibers were prepared via a modified polyol process at 90°C under an external magnetic field of about 550Oe, using ethelyne glycol as solvent and hydrazine as reducing agent. The structure, the size and the morphology of the as-elaborated products were highly controlled through properly monitoring the synthesis parameters (amount of NaOH added, the amount of the reducing agent, precursor’ concentration and precursors mixing protocol). The XRD characterization confirmed the formation of pure cobalt powders with either hexagonal compact (hcp) or face-centered-cubic (fcc) structure depending on the concentration of the metal precursor and sodium hydroxide. The scanning electron microscopy observations of the powders shows sub-micrometric fibers with about 0.4–0.6µm in diameter and a length that could reach 15µm. Fibers prepared at high reducing ratio were constituted of flower-like spheres that coalesce in the direction of the applied magnetic field. For their high contact surface, these fibers offer new opportunities for catalysis applications. The hysteresis loop measurements show an enhancement of the Hc of the as-obtained fibers compared to their bulk counterparts and permit to confirm the relationship between the structure and the magnetic properties of the materials.
•Template free synthesis of cobalt sub-micrometric fibers.•High control of the structure the structure, the size and the morphology of the products through properly monitoring the synthesis parameters.•cobalt sub-micrometric fibers with enhanced magnetic properties compared to bulk cobalt.