不同整比性VO2纳米粉体的合成

以V₂O₅,HCl,N₂H₄·2HCl和NH₄HCO₃为原料合成了紫红色多晶(NH₄)₅[(VO)₆(CO₃)₄(OH)₉]·10H₂O(I),产率80％～95％.在N₂气流中对前体I进行了TG/DTG和DTA热分析.研究了前体I在N₂-空气气流中热解时氧分压(po₂)和反应温度对产物VO₂整比性的影响.结果表明,在500℃条件下,VO_x中的x值与po₂呈正比关系,在po₂=30.3Pa条件下,在450～520℃区间,产物为缺氧VO₂;在t<450℃和t>520℃时,产物为富氧VO₂.在合适的条件下,成功地合成了从VO_1.927到VO_2.080之间不同整比性的VO₂粉体.产物组成均匀,其XRD谱未观察到非VO₂的杂质峰.VO₂粉体颗粒的平均粒径为20nm,粒度分布均匀并呈球形.

Synthesis of Various Stoichiometry Nano-powder of VO2

The violet polycrystalline (NH₄)₅[(VO)₆(CO₂)₄(OH)₉]·10H₂O(Ⅰ) was synthesized by using V₂O₅, HCl, N₂H₄·2HCl and NH₄HCO₃as the starting materials. The yield was 80%-95%. The TG/DTG and DTA of Iwere studied in a flow of N₂. The effects of partial pressure of oxygen(po₂) in N₂-air flow and temperature of reaction on VO₂stoichiometry were investigated in the pyrolysis of Ⅰ in a silica tube. The results show that x value of VO_xis proportional to po₂at pyrolysis temperature of 500 ℃ At po₂= 30.3 Pa and in the temperature range from 450 to 520 ℃ the products are oxygen-deficient VO₂, and when the temperature is lower than 450℃ or higher than 520℃ the products are oxygen-rich VO₂In this paper, various stoichiometry VO₂powders from VO_1.927to VO_2.080were successfully synthesized by pyrolysizing the precursor. XRD patterns of VO₂show that none of the impurity peaks was observed. The SEM micrograph of sample indicates that as-prepared VO₂is spherical particles with mean size 20 nm and is homogeneous in distribution. Further experiments testify that the composition of nano-powders is homogeneous.