氧钒(Ⅳ)碱式碳酸铵的热分析和纳米氧化钒的制备

The violet polycrystalline (NH₄)₅[(VO)₆(CO₃)₄(OH)₉]·10H₂O(NVCO) was simply synthesized by solution reaction using V₂O₅, HCl, N₂H₄·2HCl and NH₄HCO₃ as the starting materials. The results of TGA and DTA of NVCO under H₂(99.999%) atmosphere show that V₂O₃ forms at 620℃. The data of TG/DTG and DTA of NVCO under N₂(99.999%) atmosphere indicate that VO₂ forms at 367℃ and crystallizes at 390℃. In air atmosphere, the TG/DTG and DTA of NVCO show that V₂O₅ forms at 354℃, crystallizes at 366℃ and melts at 664℃. The three thermolysis processes of NVCO show that a large amount of H₂O, CO₂ and NH₃ gases fast releases during the thermolysis of NVCO, causing that the particles of the materials split and atomize strongly, thus to obtain V₂O₃, VO₂ and V₂O₅ nano-powders finally. According to the above of thermoanalytical results, V₂O₃, VO₂ and V₂O₅ powders were prepared respectively under H₂, N₂ and oxygen in a tube furnace. Chemical analysis and XRD ex-periments of the powders identify that pure V₂O₃ is obtained at 800℃ for 0.5h under H₂ atmosphere; crystalline VO₂ is obtained at 480℃ for 0.5h in N₂; amorphous VO₂ is obtained at 350℃ for 20min under N₂ atmosphere, this has been first reported to prepare amorphous VO₂ powder so far; pure V₂O₅ is obtained at 400℃ for 10min under oxygen. From the micrographs of the powders, the particle size of the V₂O₃, the crystalline VO₂ or the V₂O₅ powders is 35nm, 24nm or < 40nm, respectively. Above-mentioned results prove that NVCO is a good precursor for preparation of pure V₂O₃, VO₂ and V₂O₅ nano-powders under mild conditions.

Thermoanalysis of Ammonium Oxovanadium (Ⅳ) Carbonato Hydroxide and Preparation of Powders of Vanadium Oxides