氧钒(Ⅳ)碱式碳酸铵的氨解和纳米VN的制备

氮化钒(VN)具有十分高的热、化学稳定性和强的机械性能,用于切削工具和结构材料。VN作为催化剂,具有高催化活性、高选择性、良好的稳定性和抗中毒性能;其催化行为类似Pt、Pd和Rh,是这些稀贵金属的经济的代用物。细的球状

Ammonolysis of Ammonium Oxovanadium (Ⅳ) Carbonato Hydroxide and Preparation of Nano-VN Powder

A new route to synthesize pure VN nano-powder from the ammonolysis of the special precursor, (NH4)5(VO)6(CO3)4(OH)9]. 10H2O (NVCO) is described. The violet polycrystalline NVCO was simply synthesized by solution reaction using V2O5, HC1, N2H4,2HC1 and NH4HCO3 as the starting materials. The thermolysis process of the NVCO was investigated by TGA and DTA in a NH3 flow. The TG data indicated that the mass loss of the NVCO was about 58% before V2O3 forms at 630C and released fast large amount of H3O, CO2 and NH3 gases, causing that the particles of the NVCO and intermediates were split and atomized strongly during the ammonolysis, thus generating VN nanopowders. The effect of various ammonlysis conditions on nitridation rate of products was studied in detail under tube furnace condition. The result of elemental analysis identified that 95. 33% VN was obtained at 850C for 12h. The result of X-ray diffraction showed that the lattice parameter of the powder was a =0.4139(0) nm, according with a =0.413916(4) nm of ASTM. Scanning electron microscopic micrographs show that the particles of VN powder are quasi-spherical about 30nm in size with more homogeneous distribution. Advantage of this synthesis route is: (1) NVCO is easily synthesized; (2) the ammonolysis condition are milder; (3) it is not necessary to use very precise temperature-programmed reaction controls; (4) the particles of nano-VN powder are quasi-spherical and more homogeneous distribution.