Thin layer lightweight and ultrawhite hexagonal boron nitride nanoporous paints for daytime radiative cooling

• DOI: 10.1016/j.xcrp.2022.101058
• Publication Date: 2022-10-03T14:38:47Z
• Authors: Andrea Felicelli; Ioanna Katsamba; Fernando Barrios; Yun Zhang; Ziqi Guo; Joseph Peoples; George Chiu; Xiulin Ruan
• Keywords: Nanoporous; Radiative Cooling

Thin and lightweight radiative cooling paints are needed for many weight-sensitive applications. However, it is difficult to achieve high solar reflectance with thin layers. This work develops ultrawhite hBN-acrylic that of 97.9% sky window emissivity 0.83 only 150 μm thickness 0.029 g/cm2 weight, representing significant reductions from previous paints. The refractive index nanoplatelet morphology hBN enable a unique combination Mie scattering-like scattering coefficient Rayleigh strong backscattering, porosity 44.3% offers contrast between air; all contribute coating. Field tests show full daytime under direct sunlight, reaching 5–6°C below ambient temperature on average during daylight hours. Our paint demonstrates comparable performance recent best technologies, the thinness light weight reduce barriers toward practical