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Thermochromic Fenestration Elements Based on the Dispersion of Functionalized VO2 Nanocrystals within a Polyvinyl Butyral Laminate
ACS Engineering Au Pub Date : 2022-07-21 , DOI: 10.1021/acsengineeringau.2c00027
Nicholas I Cool 1, 2 , Carlos A Larriuz 1, 3 , Randall James 1 , Jaime R Ayala 1, 2 , Anita 1, 2 , Mohammed Al-Hashimi 4 , Sarbajit Banerjee 1, 2
Affiliation  

The energy required to heat, cool, and illuminate buildings continues to increase with growing urbanization, engendering a substantial global carbon footprint for the built environment. Passive modulation of the solar heat gain of buildings through the design of spectrally selective thermochromic fenestration elements holds promise for substantially alleviating energy consumed for climate control and lighting. The binary vanadium(IV) oxide VO2 manifests a robust metal─insulator transition that brings about a pronounced modulation of its near-infrared transmittance in response to thermal activation. As such, VO2 nanocrystals are potentially useful as the active elements of transparent thermochromic films and coatings. Practical applications in retrofitting existing buildings requires the design of workflows to embed thermochromic fillers within industrially viable resins. Here, we describe the dispersion of VO2 nanocrystals within a polyvinyl butyral laminate commonly used in the laminated glass industry as a result of its high optical clarity, toughness, ductility, and strong adhesion to glass. To form high-optical-clarity nanocomposite films, VO2 nanocrystals are encased in a silica shell and functionalized with 3-methacryloxypropyltrimethoxysilane, enabling excellent dispersion of the nanocrystals in PVB through the formation of siloxane linkages and miscibility of the methacrylate group with the random copolymer. Encapsulation, functionalization, and dispersion of the core─shell VO2@SiO2 nanocrystals mitigates both Mie scattering and light scattering from refractive index discontinuities. The nanocomposite laminates exhibit a 22.3% modulation of NIR transmittance with the functionalizing moiety engendering a 77% increase of visible light transmittance as compared to unfunctionalized core─shell particles. The functionalization scheme and workflow demonstrated, here, illustrates a viable approach for integrating thermochromic functionality within laminated glass used for retrofitting buildings.

中文翻译:

基于功能化 VO2 纳米晶体在聚乙烯醇缩丁醛层压板中的分散的热致变色开窗元件

随着城市化进程的加快,建筑物供暖、制冷和照明所需的能源不断增加,从而为建筑环境产生了大量的全球碳足迹。通过设计光谱选择性热致变色开窗元件来被动调节建筑物的太阳热增益,有望大幅减少气候控制和照明所消耗的能源。二元钒 (IV) 氧化物 VO 2表现出稳健的金属—绝缘体转变,可显着调节其近红外透射率以响应热激活。因此,VO 2纳米晶体可用作透明热致变色薄膜和涂层的活性元素。改造现有建筑的实际应用需要设计工作流程,将热致变色填料嵌入工业可行的树脂中。在这里,我们描述了 VO 2纳米晶体在夹层玻璃行业常用的聚乙烯醇缩丁醛层压板中的分散,因为它具有高光学透明度、韧性、延展性和对玻璃的强附着力。为了形成高光学透明度的纳米复合薄膜,VO 2纳米晶体包裹在二氧化硅壳中并用 3-甲基丙烯酰氧基丙基三甲氧基硅烷进行功能化,通过形成硅氧烷键以及甲基丙烯酸酯基团与无规共聚物的混溶性,使纳米晶体在 PVB 中具有出色的分散性。核壳的封装、功能化和分散 VO 2 @SiO 2纳米晶体减轻了折射率不连续性引起的 Mie 散射和光散射。与未功能化的核壳颗粒相比,纳米复合层压板显示出 22.3% 的 NIR 透射率调制,功能化部分使可见光透射率增加了 77%。此处展示的功能化方案和工作流程说明了一种将热致变色功能集成到用于改造建筑物的夹层玻璃中的可行方法。
更新日期:2022-07-21
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