Abstract A multilayer passive radiative selective cooling coating based on Al/SiO2/SiNx/SiO2/TiO2/SiO2 prepared by dc magnetron sputtering is presented. The design was first theoretically optimized using the optical constants, refractive index and extinction coefficient, of thin single layers. The spectral optical constants in the wavelength range from 0.3 to 27 µm were calculated from the transmittance and reflectance data of thin single layers deposited on silicon and glass substrates. The samples were characterized by Scanning Electron Microscopy, X-ray diffraction, Fourier-transform Infrared Spectroscopy and UV–VIS–NIR spectroscopy. It is shown that the TiO2 layer presents a partially rutile phase polycrystalline structure and a higher refractive index than amorphous SiO2 and SiNx layers in the spectral range from 0.3 to 2.5 μm. The cooling device was deposited on copper substrates and a thin low-density polyethylene foil with high transmittance in the 8 to 13 µm spectral range was used as convection cover material. The device is characterized by both low reflectance (high emittance) in the sky atmospheric window (wavelength range from 8 to 13 µm) and high hemispherical reflectance elsewhere, allowing for temperature drops of average 7.4 °C at night-time in winter, which corresponds to a net cooling power of ~43 W m−2. Further, a temperature drop of 2.5 °C was obtained during winter daytime.

中文翻译：

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直流磁控溅射制备基于Al/SiO2/SiNx/SiO2/TiO2/SiO2的多层被动辐射选择性冷却涂层

摘要 提出了一种基于Al/SiO2/SiNx/SiO2/TiO2/SiO2 的多层被动辐射选择性冷却涂层，采用直流磁控溅射法制备。该设计首先使用薄单层的光学常数、折射率和消光系数在理论上进行了优化。0.3 到 27 µm 波长范围内的光谱光学常数是根据沉积在硅和玻璃基板上的单层薄层的透射率和反射率数据计算得出的。通过扫描电子显微镜、X 射线衍射、傅里叶变换红外光谱和 UV-VIS-NIR 光谱对样品进行表征。结果表明，在 0.3 到 2.5 μm 的光谱范围内，TiO2 层呈现出部分金红石相多晶结构和比非晶 SiO2 和 SiNx 层更高的折射率。冷却装置沉积在铜基板上，并使用在 8 至 13 µm 光谱范围内具有高透射率的薄低密度聚乙烯箔作为对流覆盖材料。该设备的特点是天空大气窗口（波长范围为 8 至 13 µm）的低反射率（高发射率）和其他地方的高半球反射率，允许冬季夜间温度平均下降 7.4 °C，对应到约 43 W m-2 的净冷却功​​率。此外，冬季白天的温度下降了 2.5 °C。该设备的特点是天空大气窗口（波长范围为 8 至 13 µm）的低反射率（高发射率）和其他地方的高半球反射率，使得冬季夜间温度平均下降 7.4 °C，对应到约 43 W m-2 的净冷却功​​率。此外，冬季白天的温度下降了 2.5 °C。该设备的特点是天空大气窗口（波长范围为 8 至 13 µm）的低反射率（高发射率）和其他地方的高半球反射率，使得冬季夜间温度平均下降 7.4 °C，对应到约 43 W m-2 的净冷却功​​率。此外，冬季白天的温度下降了 2.5 °C。