A convenient route to bulk polycrystalline nanopowders of explosion phase boron nitride (e-BN) was carried out through magnesiothermic-reduction of boron oxide (B₂O₃) and ammonium chloride (NH₄Cl) catalyzed with anhydrous cobalt chloride (CoCl₂) at temperatures ranging from 650 to 800℃ in a sealed stainless steel autoclave. X-ray diffraction (XRD) indicates a cubic phase with lattice parameter a＝0.8304 nm. Fourier transform infrared spectroscopy (FTIR) shows characteristic absorption peaks at 500, 650, 797, 1085, 1374 and 1580 cm^－1. Scanning electron microscopy (SEM) reveals the polycrystallites having approximately uniform quasi-spherical morphology with average diameter of about 70 nm. Chemical reaction and catalytic formation mechanism of the product was also proposed.

Key words: explosion phase boron nitride, magnesiothermic reduction, synthesis, nanomaterial