Microstructures and magnetic properties of boron nitride- and carbon-coated iron nanoparticles synthesized by a solid phase reaction

A promising technique to synthesize iron nanoparticles with boron nitride (BN) and carbon (C) nanocoatings was developed. Mixtures of alpha-Fe2O3 and boron or carbon powders were employed as starting materials and were annealed at temperatures above 1273 K in a nitrogen atmosphere. Products were mainly composed of alpha-Fe and hexagonal BN or graphite carbon without hematite, which was confirmed by X-ray diffraction. High-resolution transmission electron microscope observation revealed that BN and C nanocapsules with iron nanoparticles of ca. 300 nm in diameter were formed, and they exhibited soft magnetic properties from magnetization measurements. In addition, multi-walled BN and C nanotubes with diameters of a few hundred nanometers were produced by the present method.