Size and phase control of cobalt–carbide nanoparticles using OH− and Cl− anions in a polyol process

Abstract

Exchange coupled cobalt–carbide nanocomposites and single-phase Co2C nanoparticles were synthesized using the polyol process. Hydroxide and chloride anions were used to control carbide phase and particle shape. Synthesized CoxC nanocomposites exhibited average diameters around 300 nm. CoxC nanocomposites synthesized at 0.25 M [OH−] and [Cl−] formed clusters of capped nanorods, whereas synthesis at 0.37 M [OH−] and [Cl−] produced clusters of long blade-like particles. For single-phase Co2C, an [OH−] and [Cl−] of 0.71 M was used and produced clusters of ellipsoidal grains. The CoxC nanocomposites comprised of capped nanorods possessed a BHmax of 1.65 MGOe with a magnetic saturation and coercivity values of 38 emu/g and 2.4 kOe, respectively. Co2C possessed a saturation magnetization of 16 emu/g and coercivity of 1.3 kOe.