准连续透明导电微网调制的VO2低发射率智能节能涂层的设计、构筑及其在建筑节能领域的应用研究

Vanadium dioxide (VO2) materials can intelligently modulate the light and heat throughout the buildings, and are among the most hot topic materials in building energy conservation fields. The process of compositing VO2 with transparent conductive low emissivity materials is considered to be the key point to improve the thermal insulation ability and to achieve high annual energy saving efficiency. However, investigations indicated that there are severe interactions for the emissivity and solar modulation efficiency, because of the strong absorption in near-infrared region for transparent conductive materials. . Based on the existing research results, the project proposed the solution of applying quasicontinous transparent conductive materials with sub-micrometer rang holes, which can achieve high visible and near-infrared transmittance as well as the low emissivity in long wavelength infrared region, to achieve the proper optical properties in broad band VIR-NIR-MIR regions. Based on theoretical simulation, both vanadium dioxide nanoparticles and one-dimensional copper and silver nanowire with high aspect ratios will be synthesized via solution-based process (e.g., hydrothermal and others), and after that, a low temperature based annealing process is to be developed and investigated. The influences of compositions, microstructures and their evolution on the optical and phase transition properties will be discussed. All these will provide great potentials for the development of novel high performance energy-efficient smart windows with low emissivity and high solar modulation efficiency.

二氧化钒（VO2）可依据环境温度智能调节建筑摄入的太阳辐射热，是当今建筑节能领域研究的热点材料之一。与中远红外光区低发射率性质的透明导电（TC）材料复合是提升热阻隔及全年节能效率的方向。但连续TC膜在近红外区的高吸收导致复合膜层在发射率与太阳热调节效率之间存在制约关系。. 本项目创新性提出构筑具有亚微米尺度微孔结构的准连续透明导电金属微网，利用微孔对小于其尺寸的短波长光子高透过以及金属导电网络对长波长光子的高反射性质，获得复合薄膜在可见-近红外-中远红外多波段光学性质的合理调控。在光学设计的基础上，采用水热等湿化学方法制备超细VO2粉体和高长径比一维Cu、Ag导电纳米线，探索经涂覆成膜和后续低温热处理获得不同复合薄膜的相关工艺；着重研究复合膜层的组分、微结构及其演化与多尺度光学、相变性质的关联机制，为兼具低发射率和智能调节效率的新型高效VO2智能窗开发奠定基础。

二氧化钒基智能温控涂层是当前建筑节能领域研究的热点体系，但其发射率过高影响了实际节能效果。本课题采用具有可见-近红外波段宽谱高透过以及中远红外光高反射特性的准连续金属纳米线微网结构与VO2材料复合，探索了兼具热致变色和低发射率性质的新型高效节能窗体系。主要成果包括：基于时域有限差分法等理论，研究了准连续金属网格体系中微结构与光的相互作用，发现Ag、Cu等材料的准连续网络结构与VO2智能窗在宽光谱范围内具有较优的光学性能匹配。在此基础上，通过醇热还原法制备了不同结构的银纳米线，发现减小Ag纳米线直径、提升长径比和优化填充状态等可实现样品在可见-近红外光区透过率及中远红外光区反射性质的提升。基于液相反应原理，成功开发出VO2纳米粒子的低温熔盐法合成工艺，揭示了制备温度、掺杂、籽晶诱导等对材料组成、结晶相转化及微观形貌等的影响规律，在380℃条件下成功获得了直径约40nm且分散性较好的VO2纳米粉体，为复合节能涂层的廉价低温制备及性能提升奠定了基础。在国际上率先开展了VO2涂层与Ag纳米线微网结构复合的相关工作，研究发现与直接镀制于VO2表面的AZO, Pt等连续膜层相比, 准连续Ag纳米线微网结构在降低发射率ɛ和保持VO2太阳热调节效率ΔTsol方面具有明显优势。对于镀制于石英玻璃上的单层VO2薄膜, 通过优化AgNWs的涂覆厚度, 可将发射率降低至0.21, 同时ΔTsol仍保持5.8%；而对于VO2-PU复合柔性涂层，镀制AgNWs结构后，其发射率可降低至0.23，同时ΔTsol仍保持12.1%，为目前低发射热致变色体系中报道的较优结果。在此基础上围绕涂层光学性质提升及抗氧化服役性能研究等开展了系统工作，为新型低发射热致变色节能涂层开发提供了研究依据。