二氧化钒基核-壳纳米结构的制备及其性能调控

Research and development of intelligent windows is a strategic approach for increase energy saving performance of buildings, reducing green-gas emission and realizing sustainable development for our country. The novel thermochromic intelligent windows based on the principle of reversible metal-insulator phase transition of vanadium dioxide (VO2) can just meet the demands of our society. Compared with energy saving glass prepared by physical deposition method, VO2-based composite polymer film shows high potential commercial value and can embody high quality of VO2 nano-particles. Until now, studies mainly concentrate on the controllable synthesis of VO2 nanoparticles with high performance and solving the problems meeting in the earlier stage of industrial applications. However, from the view of industrial application there are several problems need to be solved imperatively, such as the poor chemical and thermal stability of VO2 and its unacceptable intrinsic color, difficult to disperse etc. In this proposal, we raise a routine to solve the mentioned problems via the formation of VO2-based core/shell nano-structures. The studies will focus on: (1)preparation of core/shell particles with thickness controllable single-layer or multi-layer trasnparent organic oxides shell(s) through facile soft chemical processes; (2)clarifying the formation mechanism of shell from solution and the following crystallization and growth process; (3)elucidating the structure of the interface between core and shell and optimizing the transmittance through the variation of the dimensional ratio between core and shell by optical simulation; (4)discovering new properties and phenomenon accompanying the formation of heterojunction between core and shell; (5) modification the color by the formation of tungsten bronze through intercalating H or Li to the lattice of WO3; (6)decreasing thermal conductivity by the formation of composition with a movable VO2 core; (7)dispersion of VO2 nano-powder and its related core/shell structures in water or organic solvents.

智能节能窗对提高我国建筑节能水平、实现可持续发展具有重要战略意义。基于二氧化钒相变的新型温控智能节能窗是适应我国国情的首选。与物理镀膜节能玻璃相比，利用二氧化钒纳米粒子优异光学性能的复合聚合物薄膜更具潜在应用价值。目前的研究主要集中于单相二氧化钒纳米粒子的可控制备与应用探索，但已发现单相二氧化钒纳米粒子存在化学及热稳定性差、呈色、不易分散等问题。本项目针对上述问题提出制备二氧化钒基核-壳纳米结构的解决方案。重点研究利用软化学法制备厚度均匀可控的透明氧化物单层及复层核-壳结构；解明壳层的形成机制及晶化与生长过程并实现低成本规模化制备；研究核-壳界面结构、通过光学模拟优化透过率与核粒径、壳层厚度及其配比关系；利用核、壳所形成的异质结结构探索新物性、新现象。研究内容还涵盖运用插层化学反应调节WO3壳层及复合体的顔色、形成具有可移动核的核-壳结构降低热导率及纳米粒子在水或有机体系中的分散、稳定性。

建筑能耗占我国社会总能耗的三分之一以上，智能节能窗对提高我国建筑节能水平具有重要意义。基于二氧化钒相变的新型温控智能节能窗是适应我国国情的首选。与物理镀膜节能玻璃相比，利用其纳米粒子优异光学性能的复合聚合物薄膜更具潜在实用价值。过去的研究主要集中于单纯二氧化钒纳米粒子的可控制备与应用探索，但已发现单纯二氧化钒纳米粒子存在化学及热稳定性差、呈色、不易分散等问题。.本项目针对上述问题提出制备二氧化钒基核-壳纳米结构的解决方案。主要研究内容包括：二氧化钒纳米颗粒制备、多种无机包覆（含C、SiO2、Al-O、ZnO及SnO2）及无机/有机复合包覆、新型钒青铜结构及电化学性能、VO2/有机系复合材料等。共发表论文27篇。.利用微乳液法制备小尺寸V1-xWxO2@SiO2，用其所制备的节能膜在透过率>45%时太阳能调节效率>14%；利用化学沉淀法制备V1-xWxO2前驱体并通过包覆SiO2及后续退火处理，减小晶体缺陷提高结晶性能，所制得的颗粒尺寸小于20nm且分布窄。用其所制备的节能膜性能优异（相变温度40.4℃，透过率>52%时太阳能调节效率>17%；相变温度25.2℃，透过率>50%时太阳能调节效率>14.7%），具有极高实用价值。此外，还利用水热辅助均匀沉淀法制备高性能VO2纳米颗粒并结合绿色化工的思想一步水热制备了VO2-BaSO4复合粉体。.通过实施多种无机及无机/有机复合包覆方案，提高了VO2节能膜的耐候稳定性，赋与材料新的性能并对其核壳结构的形成机理等展开了研究。高温高湿环境实验（60℃，90%RH）表明，利用未包覆的VO2做成的膜，其寿命通常在1~2天。通过Al-O包覆可使复合粉体制成的膜的寿命提高到20天，能过ZnO/聚合物复合包覆可进一步将节能膜的寿命提高到42天以上。通过包覆还进一步改善了粉体的分散性能及智能膜的热致相变特性。如用ZnO/聚合物复合包覆粉体制备的节能膜在透过率>50%时太阳能调节效率>19%。这些研究体现了极高的产业化价值。.VO2材料的智能调节性能只体现在近红外波段，因而不具有视觉表现能力。通过与有机热致变色系材料复合使复合体系的智能调节范围覆盖了太阳光谱的全波段，大幅提高了太阳能调节效率并赋予其可视化功能。