Anisotropic thermally conductive coating with high reflectivity for radiative cooling and high-energy laser protection

Both radiative cooling coatings and laser protection coatings represent significant technical challenges. The former achieves passive cooling through thermal radiation, while the latter guards against high-energy laser damage with high reflectivity and thermal conductivity. Because they share commonalities in optical performance and physicochemical stability, their integration into a single dual-function coating is highly desirable for specific applications such as vehicles. Here, we developed a coating consisting of low-melting-point glass powders and hexagonal boron nitride nanosheets (BNNS) that features high solar reflectance, excellent long-wave infrared (LWIR) emission, and anisotropic thermal conductivity. The coating achieved an average solar reflectance of 97.6% (0.4−2 μm) and an average emissivity of 0.95 (8−13 μm), which consequently reduced the back-surface temperature of the substrate by 18.75 °C under daily sunlight irradiation. In addition, the thermal conductivity in the in-plane direction of the coating was 9.1 times that in the out-of-plane direction, leading to effective protection against high-energy laser irradiation at 1500 W/cm² for 10 s. Therefore, owing to this dual-functional performance, the coating has great application potential in both military and civilian fields.