【作者】 刘风娟；

【导师】 宁桂玲；

【作者基本信息】 大连理工大学 ， 化学工艺， 2009， 硕士

【摘要】 VO₂（M）和VO₂（R）在68℃附近发生可逆相变,相变过程中光学透过率会发生突变,使其在控温薄膜领域有很好的应用前景。将VO₂粉体分散于有机高分子材料中制备复合薄膜,可以克服无机薄膜耐水性差,易开裂等缺点。但是要将粉体实现应用还需解决如下问题:1、降低VO₂的相变温度,实现在室温下的相转变。如何实现在VO₂粉体制备时进行掺杂实现相变温度的降低,是待解决的问题。2、VO₂相变时会产生体积变化,在复合薄膜中将产生微应力,需减小粉体的尺寸来减小此应力,同时可保证薄膜有良好的透明性。NH₃气还原V₂O₅是一种简单易控的制备VO₂的方法,本论文在此基础上展开如下研究:1.确定了NH₃还原法制备VO₂的反应条件,由试验分析了不同还原时间和热处理条件对产物晶体结构的影响。2.在高温融熔水淬过程中加入掺杂剂进行掺杂,并结合还原反应制得掺杂VO₂。比较了钨酸、钨酸钠、钼酸铵作为掺杂剂对V₂O₅和VO₂晶体结构的影响。分析了掺杂元素对VO₂相变温度的降低效率。3.利用水热反应对钒氧化物进行形貌控制,结合氨气还原制备了具有一定形貌的微纳米VO₂。考察了水、乙醇、草酸对V₂O₅粉体价态和形貌的影响,并对得到的钒氧化物进行还原和热处理,制备了具有一定形貌的VO₂粉体。4.研究了水热条件下不同掺杂方式对VO₂粉体相变温度的影响。钨酸分别以溶胶凝胶法与直接加入法的方式进行反应,得到了不同的降温效率。更多还原

【Abstract】 VO₂（M） undergoes a reversible semiconductor-metal phase transition with VO₂（R） at about 68℃.The optical transmittance will change drastically during the phase transition procedure.So VO₂ has attracted much attention for its potentiality in the temperature control film.The compound film VO₂ particles suspended in the polymer has many advantages for the application.But the phase transition temperature（Tt） is a little higher for the use in the atmosphere.So it is important to synthesize the doped VO₂ particles to decreased the Tt.Also size of the particles should be controled to lessen the stress caused by the phase transition and to make the film transparent.Up to now,reduction of V₂O₅ in ammonia gas is an easy way to synthesize VO₂ particles.Based on these results,research was developed as followes:1.Reaction procedure was optimized to synthesize the VO₂ particles in the ammonia gas. Effect of the heat treatment on the crystal structureof the product was also analyzed.2.The sol-gel method was used to prepare the doped V₂O₅.By reduction in ammonia, the W-doped VO₂（M） was synthesized.Tungsten acid,Na₂WO₄·2H₂O and ammonium molybdate were added as the dopant respectively.Effect of the dopants on the crystal structure of V₂O₅ and VO₂ was investigated.DSC was used to analyze the change of Tt for the doped VO₂.3.Hydrothermal method was used to prepare the vanadium oxides with special morphologies.Reactions of water,ethanol and oxalic acid with V₂O₅ powders were conducted respectively under the hydrothermal condition.Reduction and the heat treatment turned the products to VO₂（M） with special size distrubution.4.Different methods were used to prepare the doped VO₂ with tungsten acid and oxalic acid as the reactants under the hydrothermal condition.When tungsten acid was added directly and via the sol-gel method respectively,different deduction efficiency was got.更多还原