Anisotropic Radiative Cooling Dynamics Enabling Efficient Thermal Hazard Mitigation via Hierarchically Engineered Thermal Diodes

Radiative cooling coatings demonstrate broad applicability on equipment surfaces, spanning spacecraft to precision instruments, for sub-ambient cooling. However, unlike conventional equipment relies on solar reflection and infrared emission for cooling, the heat-generating equipment relies on coupled thermal conduction and radiative cooling, representing a distinct heat transfer paradigm. This study introduces an innovative fire-safe radiative cooling-enhanced anisotropic thermal rectification coating (TRC) by leveraging the thermal rectification effect. The rectification mechanism stems from engineered thermal conductivity gradients with temperature-dependent anisotropy, where asymmetric phonon transport in multilayer architectures enables unidirectional heat flux control. Through the rational coupling of radiative cooling emitters at the cold terminal with thermal diodes, the TRC achieves unidirectional heat transfer enhancement through conduction-radiation coupling, demonstrating a thermal rectification coefficient of 1.78 and 3.1–3.4 °C daytime temperature reduction below ambient. Crucially, under concurrent solar irradiation and simulated heat-generating equipment (50 °C), TRC attains 6.8 °C maximum cooling enhancement. Notably, the TRC integrates gas-phase and condensed-phase flame retardant mechanisms to effectively mitigate the risk of thermal runaway in heat-generating devices. This multifunctional integration advances radiative cooling technology toward practical implementation in thermal-critical infrastructure, including power electronics thermal management and smart building systems.