Scalable, flame-resistant, superhydrophobic ceramic metafibers for sustainable all-day radiative cooling. (February 2023)

• Record Type: Journal Article
• Authors: Tsai, Meng-Ting; Chang, Sih-Wei; Chen, Yen-Jen; Chen, Hsuen-Li; Lan, Pin-Hui; Chen, Dai-chi; Ko, Fu-Hsiang; Lo, Yu-Chieh; Wang, Hsueh-Cheng; Wan, Dehui
• Is Part Of: Nano today. Volume 48(2023)
• Publication Date: 2023-02
• Subjects: Flame-resistance -- Self-cleaning -- Electrospinning -- Ceramic nanofibers -- Passive radiative cooling; Nanotechnology -- Periodicals; Nanosciences -- Périodiques; 620.505
• DOI: 10.1016/j.nantod.2022.101745
• Languages: English
• ISSNs: 1748-0132

Abstract

Abstract: Passive daytime radiative cooling (PDRC), as a strategy to dissipate heat through an atmospheric transparency window (ATW) to outer space without any extra energy consumption, has been recently considered as a novel approach for global net-zero emissions. However, limited to expensive manufacturing, poor thermal/chemical stability, or insufficient weather-resistance, the development of a PDRC building material for long-term outdoor usages still remains a challenge. Here, a scalable superhydrophobic silica metafibers (sh-SMF) was fabricated via an electrospinning process combined with the fluorosilane-modification on fiber surface. The optically engineered sh-SMF could attain an extremely high average reflectivity (∼97 %) with near-zero absorption in the solar spectral region, due to the multiple backscattering at the fiber/air interfaces. In addition, the sh-SMF possessed a high average emissivity (∼90 %) in ATW, originated from the strong phonon resonances of the abundant Si-O bonds. Thus, the optimal sh-SMF realized a sub-ambient cooling performance of 6 °C (4 °C in nighttime) and the maximum cooling power of 112 W/m 2 (87 W/m 2 in nighttime) under a solar irradiance of ∼790 W/m 2 . Besides, the temperature decline for the sh-SMF-covered building and vehicle models could also achieve 12.7 °C and 17 °C under sunlight, respectively. Noteworthily, the ceramic sh-SMF could withstand high temperatures over 1200 °C, which might effectively prolong the time for resident to evacuate from buildings in fireground situation. Moreover, the superhydrophobic surface (contact angle=155°) of sh-SMF demonstrated attractive self-cleaning and anti-mildew properties. Furthermore, the excellent weather resistance against acid rain and ultraviolet exposure endowed the sh-SMF with long-term cooling performance. Finally, the sh-SMF with above mentioned properties opens a path for future energy-efficient and sustainable architectural applications. Graphical Abstract: ga1 Highlights: Superhydrophobic silica metafibers (sh-SMFs), fabricated through electrospinning, serving as a scalable, flexible, and flame- and weather-resistant ceramic PDRC emitter. The optimal sh-SMFs operated with a near-zero value of P sun (<3 W/m 2 ), and a high value of P cooling (112 W/m 2 ) during the daytime, resulting from high solar reflectivity (97 %) and thermal emissivity (90 %). Maximum temperature decreases of sh-SMF–covered building and vehicle models of 12.7 and 17 °C, respectively, under sunlight. The sh-SMFs could withstand high temperatures (>1200 °C), making them especially suitable as a building material that could effectively prolong the time available for residents to evacuate buildings in the event of fire. The sh-SMFs display excellent self-cleaning, anti-mildew, and anti-acid abilities, combined with great UV-resistance, resulting in great weather-resistance for long-term outdoor applications.