亚稳六方相三氧化钨的液相合成及其性能研究

发布时间：2018-04-12 19:35

本文选题：h-WO_3 + 分级结构　；参考：《湖南大学》2015年硕士论文

【摘要】：无机纳米材料的研究和应用对社会的发展意义重大,以三氧化钨(WO3)为基体的无机材料因其独特的结构和性能引起了广泛的关注和研究。本文主要采用条件温和,工艺简单的液相沉淀法,合成了一系列亚稳六方相三氧化钨纳米材料,并对其光致变色性能和光催化降解性能进行了探索研究,具体内容如下：1.在900C下,通过常压下简单的水溶液法成功合成出由一维纳米单元组装而成的类球状亚稳六方相WO3 (h-WO3)分级结构。合成过程中分别考察了酸量、反应时间、阳离子、表面活性剂、PVP用量及链长对样品的形貌及其相态的影响。结果表明：酸量对样品的最终相态起到了至关重要的作用,在溶液pH=1-1.5(即WO42-/H+的摩尔比为1：2～1：2.25)范围内可得到纯h-WO3样品。突破了h-WO3的合成需要高温高压这一难题,并对有机分子聚乙烯吡咯烷酮(PVP)的作用机理进行了深入探讨。在反应体系中,PVP分子在H+的进攻下,迅速质子化成为带正电的离子,PVP正离子与带负电的WO42-快速结合,在动力学驱动下快速形成亚稳相h-WO3晶核。作为软模板的PVP分子在溶液中发生卷曲,促使样品形成了类球状的h-WO3分级结构。对合成出的亚稳相h-WO3分级结构进行了光致变色性能测试,样品在可见光下展现了优异的可逆变色性能。此工作对温和条件下亚稳相材料的合成及应用提供了新思路。2.以钨酸钙、钨酸钡等为前驱体模板,用自牺牲模板法合成出球形亚稳h-WO3中空结构。通过调节溶液中盐酸的量、酸的加入方式、前驱体的晶化程度及种类等因素实现了对产物形貌及相态的可控合成。结果表明：前驱体模板的溶度积常数对模板形貌能否遗传具有至关重要的作用,控制模板的晶化程度及模板向产物的转变速度,能够获得形貌完整的中空结构WO3。对样品进行了可见光、紫外光的光致变色性能和催化降解有机物的性能考察,亚稳相h-WO3中空结构的光致变色性能和降解性能均优于正交相WO3 (o-WO3)中空结构。
[Abstract]:The research and application of inorganic nanomaterials are of great significance to the development of society. The inorganic materials based on tungsten trioxide (WO _ 3) have attracted wide attention due to their unique structure and properties.In this paper, a series of metastable hexagonal tungsten trioxide nanomaterials were synthesized by liquid phase precipitation with mild conditions and simple process. The photochromic properties and photocatalytic degradation properties of these nanomaterials were studied. The main contents are as follows: 1.At 900C, a spherical metastable hexagonal phase WO3 (h-WO3) structure was successfully synthesized by a simple aqueous solution method under atmospheric pressure.The effects of acid content, reaction time, cations, the amount of surfactant PVP and the chain length on the morphology and phase state of the samples were investigated.The results show that the acid content plays an important role in the final phase state of the sample. The pure h-WO3 sample can be obtained in the range of pH ~ (-1) ~ (1.5) (that is, the molar ratio of WO42-/H is 1: 2: 1: 2.25).This paper breaks through the difficult problem that the synthesis of h-WO3 needs high temperature and high pressure, and probes into the action mechanism of organic molecule polyvinylpyrrolidone (PVP).In the reaction system, under the attack of H, the protonation was rapidly formed into a positive ion, the positive ion of PVP and the negatively charged WO _ 42-, and the metastable h-WO3 crystal nucleus was rapidly formed under the driving of kinetics.The PVP molecule, as a soft template, curls in solution, which results in the formation of spherical h-WO3 classification structure.The photochromic properties of the synthesized metastable phase h-WO3 were tested. The samples showed excellent reversible chromotropic properties under visible light.This work provides a new idea for the synthesis and application of metastable phase materials under mild conditions.The spherical metastable h-WO3 hollow structure was synthesized by using calcium tungstate and barium tungstate as precursor templates.By adjusting the amount of hydrochloric acid in solution, the way of adding acid, the degree and type of crystallization of precursor, the controllable synthesis of product morphology and phase state was realized.The results show that the solubility product constant of the precursor template plays an important role in the inheritance of the template morphology. Controlling the crystallization degree of the template and the rate of transition from the template to the product, the hollow WO3 with complete morphology can be obtained.The photochromic and photochromic properties of the samples under UV light and catalytic degradation of organic compounds were investigated. The photochromic and degradable properties of the metastable h-WO3 hollow structure were superior to those of the orthotropic WO3 / WO _ 3 hollow structure.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ136.13;O643.36

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