New approach for direct chemical synthesis of hexagonal Co nanoparticles

•We synthesized hexagonal cobalt nanoparticles by a new wet chemical method.•We considered the effects of different surfactants on particles magnetic properties.•The as-made Co nanoparticles had magnetic properties of 143 emu/g and 500 Oe.•After annealing magnetic properties of 160 emu/g and 540 Oe were obtained.

In this paper, we explore the possibility of producing hexagonal Cobalt nanoparticles, with high saturation magnetization by direct chemical synthesis. The nanoparticles were synthesized by reduction of anhydrous cobalt (II) chloride by NaBH4 in tetraglyme at temperatures in the range of 200–270 °C under a nitrogen–hydrogen atmosphere. The reactions were done at high temperatures to allow for the formation of as-made hexagonal cobalt. The size of the particles was controlled by the addition of different surfactants. The best magnetic properties so far were obtained on spherical hexagonal Co nanoparticles with an average size of 45 nm, a saturation magnetization of 143 emu/g and coercivity of 500 Oe. the saturation magnetization and coercivity were further improved by annealing the Co nanoparticles leading to saturation magnetization of 160 emu/g and coercivity of 540 Oe.