Synthesis and anti-oxidation performance of nanoflake-decorated boron nitride hollow microspheres

Abstract In this study, a novel boron nitride composite structure composed of nanoflake-decorated hollow microspheres is demonstrated. A paste-like mixture is firstly prepared by mixing amorphous boron with ferric nitrate ethanol solution, followed by heating at 1300 °C in a flowing ammonia atmosphere for 5 h. Both the nanoflakes and microspheres are composed of crystalline hexagonal boron nitride. The hollow spheres have outer diameters of 0.8–3 μm with thickness of about 300 nm, while the nanoflakes have thicknesses of 2–7 nm and lengths of 10–100 nm. Heating temperature is found to be crucial for the formation of this composite structure. The growth process consists of a vapor–liquid–solid growth stage of smooth hollow microspheres at lower temperature and a vapor–solid growth stage of nanoflakes on the surface of the microspheres at higher temperature. The boron nitride composite structure exhibits excellent anti-oxidation performance up to 900 °C.