Synthesis of Co nanocapsules coated with BN layers by annealing of KBH4 and [Co(NH3)6]Cl3

Cobalt (Co) nanocapsules coated with boron nitride (BN) layers were synthesized by annealing of ammine complex. KBH4 and [Co(NH3)6]Cl3 were used as starting materials, and annealed these powders at 500–1000 °C with flowing nitrogen gas. Formation of fcc-Co nanocapsules coated with BN layers was observed from X-ray diffraction patterns and high-resolution electron microscopy. Particle size of fcc-Co prepared at 1000 °C with flowing 100 sccm N2 gas was approximately 40 nm, and the values of saturation magnetization and coercivity were 74.5 emu/g and 88 Oe, respectively. Good oxidation- and wear-resistances were obtained by encapsulating Co nanoparticles with BN layers.