Formation of nanosized particles encapsulated in boron nitride during low-temperature annealing of mechanochemically treated Fe–BN mixtures

Abstract

Electron microscopic investigations and X-ray studies of mechanically activated mixtures of iron and boron nitride provide evidence of the transformation of hexagonal boron nitride into the amorphous state, which is shows up as a halo with maximum at d=3.35 Å in the electron diffraction patterns. According to the obtained electron microscopic data, the particles of iron and boron nitride after mechanical activation form aggregates with a size of 300–1000 nm. The iron particles exhibit a rather broad size distribution (from 3–7 nm to 100 nm), while the minimal size of the boron nitride particles is several tens of nanometers. Annealing of iron samples with boron nitride after preliminary mechanical activation, at a temperature of 860 °C, caused the formation of nanosized encapsulated particles of iron boride Fe 2B. The surface of the Fe 2B nanoparticles were coated with a shell composed of hexagonal boron nitride, 5–15 nm thick. The size of the encapsulated particles varies within a rather broad range from 30 to 50 nm to several hundred nanometers.