Passive radiative cooling technology has been widely concerned due to its merits of energy free and zero pollution. However, most of the radiative cooling materials are highly susceptible to contamination from solid dirt and rainwater, which greatly weak their cooling effectiveness. Herein, a hydrophobic radiative cooling composite coating, composed of polyurethane/polydimethylsiloxane (PU/PDMS) and modified hollow glass microsphere (MHGM), was fabricated through in situ reinforcing and phase separation processes. By the synergistic effect of MHGM filler and the surrounded microporous PU/PDMS matrix, the PU7/PDMS3-MHGM coating possessed strong solar reflectance and thermal emittance in the atmospheric transparency window of 0.906 and 0.961, respectively, resulting in sub-ambient daytime cooling of 8.1 °C and nighttime cooling of 3.9 °C. In addition, the composite coating exhibited a higher water contact angle of 139°, the dust and muddy water are unable to stain on its surface during the rinsing process, showing self-cleaning effect. More encouragingly, the composite coating still remained above 93.8 % passive radiative cooling efficiency even if after 100 cycles muddy water rinsing, certainly, such self-cleaning provides assurance for the sustainable application of radiative cooling coatings.

中文翻译：

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具有自清洁和持久被动辐射冷却性能的改性空心玻璃微球原位增强聚氨酯/聚二甲基硅氧烷复合涂层

被动辐射冷却技术因其无能源、零污染的优点而受到广泛关注。然而，大多数辐射冷却材料极易受到固体污垢和雨水的污染，这大大削弱了其冷却效果。本文通过原位增强和相分离工艺制备了由聚氨酯/聚二甲基硅氧烷（PU/PDMS）和改性空心玻璃微球（MHGM）组成的疏水性辐射冷却复合涂层。通过 MHGM 填料和周围微孔 PU/PDMS 基体的协同作用，PU7/PDMS3-MHGM 涂层在大气透明窗口中具有很强的太阳反射率和热发射率，分别为 0.906 和 0.961，从而实现低于环境的白天冷却。 8.1 °C，夜间降温 3.9 °C。此外，复合涂层表现出较高的水接触角，达到139°，冲洗过程中灰尘和泥水无法沾染其表面，表现出自清洁作用。更令人鼓舞的是，即使经过100次泥水冲洗，复合涂层的被动辐射冷却效率仍保持在93.8%以上，当然，这种自清洁能力为辐射冷却涂层的可持续应用提供了保证。