A simple inorganic-solvent-thermal route to nanocrystalline niobium diboride

Nanocrystalline NbB2 has been prepared via a simple inorganic-solvent-thermal route by the reaction of metallic magnesium powders with niobium pentoxide and boric acid in an autoclave at 650 °C. X-ray powder diffraction pattern indicated that the product was hexagonal niobium diboride (NbB2), and the cell constant was a = 3.115 Å and c = 3.266 Å. Scanning electron microscopy image showed that it consisted of particles with an average size of about 30 nm. The product was also studied by BET and TGA. It had good thermal stability and oxidation resistance below 500 °C in air. The molten salt, a mixture of sodium chloride and magnesium chloride, acting as inorganic solvent during the reaction, maybe plays an important role in the formation of nanocrystalline niobium diboride with a narrow particle size distribution.