Chemical synthesis and characterization of boron/boron nitride core-shell nanostructures

A moderate chemical method [i.e., the reaction of diborane (B₂H₆) and a mixture gas of ammonia and nitrogen (NH₃/N₂) over nanoscale iron boride at 1100°C] was developed to explore the boron nitride (BN) nanostructures. The products were well characterized by high-resolution electron microscopy and energy-dispersive x-ray spectroscopy. Two types of novel core-shell nanocapsules of amorphous boron core encapsulated in crystalline boron nitride shell were obtained. The first one looked like a peanut with an amorphous B core containing a trace of BN crystallites, a transition layer of BN nanofibers and amorphous B, and a thornlike shell of BN nanofibers. The second one looked like a perfect sphere consisting of a pure amorphous B core and a rather smooth crystalline BN shell. These results not only provided us a new chemical method for preparing BN nanostructures but also enriched the important BN nanostructures family. A growth mechanism is also briefly discussed.