水解法制备M-VO_2纳米粉体

Synthesis of M-VO_2 Nanopowders by Hydrolysis Method

以VOSO_4和NH_4HCO_3为原料,采用水解沉淀法制备M-VO_2纳米粉体;借助TGA-DTA,XRD,IR和TEM等方法对VO_2形成机理进行了分析.结果表明:在226℃之前,VOSO_4的水解产物脱去物理吸附水,失重率达13.19%(质量分数),在226～415℃,脱去—OH基团,形成无定形VO_2;在DTA曲线上,375.7℃附近的放热峰为无定形VO_2向B-VO_2转变时的析晶峰;继续提高热处理温度和延长热处理时间,B-VO_2逐渐转变为M-VO_2.VO_2前躯体在氩气保护下500℃热处理3 h,即得到高纯度M-VO_2纳米粉体,其颗粒直径为25～80 nm,且大部分为单晶,相变温度为68℃.

Pure M-VO2 powder was synthesized by a hydrolysis method using VOSO4 and NH4 HCO3 as raw materials. X-ray diffraction（XRD）, infrared absorption spectrometry（IR）, transmission electron micros- copy（TEM）, differential thermal analysis（DTA） and thermogravimetric analysis（TGA） were employed to analyze the formation mechanism of the M-VO2 powder. The results indicate the hydrolysis precursor of vanadyl sulfate has a weight loss rate of 13.19% at lower than 226 °C due to the loss of physically adsorbed water. Amorphous VO2 forms between 226 °C and 415 °C due to dehydration of --OH groups. The exothermic peak at 375.7 °C is attributed to the crystallization of amorphous VO2. Pure VO2 powder was obtained by annealing precursor for 3 h at 500 °C in Ar atmosphere, the product is composed of M-VO2 particles with size ranging from 25 to 80 nm, and some particles are of single crystalline. The phase transition temperature of the powder is the same as the theoretical value of M-VO2.