Effect of Chemical Precipitation Process on Particle Size of VO₂ Precursor and Its Hydrothermal Crystallization

Nanopowders of VO₂ were prepared by chemical precipitation assisted with hydrothermal crystallization using vanadyl sulfate as the vanadium source and sodium hydroxide as the precipitant.The influences of vanadium concentration,pH value of precipitation,reaction temperature,reaction time,type and dosage of surfactants on the particle size of precursor during chemical precipitation were studied.The crystal form,morphology,the size distribution and phase-transition temperature of products were analyzed by X-ray diffraction,SEM,particle size analysis and thermal analysis,respectively.The results show that the precursor with a minimum size of 210 nm can be obtained at the concentration of vanadium of 0.1 mol/L,the precipitation pH of 3.7,the reaction temperature of 20 ℃ for 5 min and the dosage of CTAB of 0.1%.High purity and homogeneity of M-VO₂ with the average particle size of 205 nm and the phase transition temperature of 65.3 ℃ can be obtained by crystallization of the precursor at 260 ℃ for 4 h in deionized water.