Park Soojin, Choi Junyeol, Lee Jeongwoo, Seo Junyong, Lee Jaemin, Kim Jiheon, Hong Myounggi, Lee Donghyun, Park Jisoo, Park Jinwoo, Choi Wonjoon
School of Mechanical Engineering, Korea University, 145 Anam-Ro, Seongbuk-Gu, Seoul, 02841, Republic of Korea.
Energy Efficiency Research Division, Korea Institute of Energy Research, Daejeon, 34129, Republic of Korea.
Small. 2025 Feb;21(7):e2409873. doi: 10.1002/smll.202409873. Epub 2025 Jan 7.
Passive temperature controls like passive daytime radiative cooling (PDRC)-heating (PDRH), and thermal insulation are essential to meet the growing demand for energy-efficient thermal solutions. When combined with advanced functions like electromagnetic interference shielding, these technologies can significantly enhance scalability. However, existing approaches using single thin films or uniform porous materials face inherent limitations in optimizing versatile functions, while lightweight, insulating aerogels can extend their multifunctionality by manipulating pores and fillers. Herein, carbon black (CB)-containing cellulose acetate (CA)aerogels (CB/CA aerogel) featuring gradient pores and bilayer structures are devised to implement switchable PDRC-PDRH and broadband spectral emissivity from infrared to microwave, along with high thermal insulation and elasticity. Using stirring and freeze-drying methods, the CA aerogels show low thermal conductivity (≈0.034 W mK) and demonstrate broad-spectrum functionality, with over 95.7% solar reflectivity and 93% long-wavelength infrared (LWIR) emittance, achieving a 12.25 °C temperature reduction in outdoor conditions. Furthermore, the CB/CA aerogels enhance LWIR emittance to 98.7% and provide broadband spectral emissivity with 39.4% microwave absorption. This study offers a viable solution to simultaneously control radiative cooling and microwave absorption across a broad spectrum in porous media.
被动温度控制，如被动日间辐射冷却（PDRC）-加热（PDRH）和隔热，对于满足对节能热解决方案不断增长的需求至关重要。当与电磁干扰屏蔽等先进功能相结合时，这些技术可以显著提高可扩展性。然而，现有的使用单薄膜或均匀多孔材料的方法在优化多功能方面存在固有局限性，而轻质隔热气凝胶可以通过控制孔隙和填料来扩展其多功能性。在此，设计了具有梯度孔隙和双层结构的含炭黑（CB）的醋酸纤维素（CA）气凝胶（CB/CA气凝胶），以实现可切换的PDRC-PDRH以及从红外到微波的宽带光谱发射率，同时具有高隔热性和弹性。使用搅拌和冷冻干燥方法，CA气凝胶显示出低导热率（≈0.034W mK），并展示出广谱功能，具有超过95.7%的太阳反射率和93%的长波红外（LWIR）发射率，在户外条件下实现了12.25°C的降温。此外，CB/CA气凝胶将LWIR发射率提高到98.7%，并提供具有39.4%微波吸收的宽带光谱发射率。本研究为在多孔介质中同时控制宽光谱的辐射冷却和微波吸收提供了一种可行的解决方案。
