Novel pseudo-morphotactic synthesis and characterization of tungsten nitride nanoplates

A novel pseudo-morphotactic transformation route was developed to synthesize polycrystalline β-W2N nanoplates by thermally treating tungstate-based inorganic–organic hybrid nanobelts with a lamellar microstructure in an NH3 flow. The tungstate-based hybrid nanobelts were formed in a water-in-oil-microemulsion-like “commercial H2WO4 powders/n-octylamine/heptane” reaction system. The as-obtained hybrid nanobelts were thermally treated in an NH3 atmosphere at 650–800 °C for 2 h to form cubic β-W2N nanoplates. XRD, SEM, TEM, FT-IR and TG-DTA were used to characterize the precursors and their final products. The polycrystalline β-W2N nanoplates derived from hybrid nanobelts, with side lengths of several hundred nanometers, consist of small nanocrystals with an average grain size of 3.2 nm. The formation of β-W2N nanoplates involved two steps: decomposing tungstate-based hybrid nanobelts into WOy and W species and then nitridizing the active W-containing species to β-W2N nanocrystals in an NH3 flow. The platelike morphology of the β-W2N nanocrystals was inherited from the precursor of tungstate-based inorganic–organic hybrid nanobelts.