Ammonium fluoride-activated synthesis of cubic δ-TaN nanoparticles at low temperatures

Cubic delta-tantalum nitride (δ-TaN) nanoparticles were selectively prepared using a K(2)TaF(7) + (5 + k) NaN(3) + kNH(4)F reactive mixture (k being the number of moles of NH(4)F) via a combustion process under a nitrogen pressure of 2.0 MPa. The combustion temperature, when plotted as a function of the number of moles of NH(4)F used, was in the range of 850°C to 1,170°C. X-ray diffraction patterns revealed the formation of cubic δ-TaN nanoparticles at 850°C to 950°C when NH(4)F is used in an amount of 2.0 mol (or greater) in the combustion experiment. Phase pure cubic δ-TaN synthesized at k = 4 exhibited a specific surface area of 30.59 m(2)/g and grain size of 5 to 10 nm, as estimated from the transmission electron microscopy micrograph. The role of NH(4)F in the formation process of δ-TaN is discussed with regard to a hypothetical reaction mechanism.