| Abstract: 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. |
