Synergistic Gradient Thermal and Bioinspired Optical Controls Enable High‐Performance Hierarchical Composites for Infrared Stealth in Extreme Environments

ABSTRACT The rapid advancement of infrared detection technologies creates an urgent demand for advanced stealth materials with promising applications in environmental monitoring, public safety, and aerospace. However, heat accumulation resulting from high‐temperature sources and parasitic solar irradiation, poses a significant risk of camouflage failure and thermal runaway. Herein, we propose a functionally graded composite material featuring a three‐layered architecture that achieves exceptional thermal radiation suppression through the synergistic optimization of spatially graded heat dissipation and selective surface optical properties. The base layer consists of low‐thermal‐conductivity aerogel, serving as the initial thermal barrier. The intermediate layer is a phase‐change composite material with high anisotropic thermal conductivity, which buffers thermal shock loads and achieves efficient lateral dissipation of heat flow. The top layer, inspired by beetle elytra, is a nano‐silver/porous polyethylene composite film demonstrating pronounced optical selectivity, combining high solar reflectivity with low infrared emissivity. After exposure to 100 mW cm −2 illumination and a 400°C heat source for 10 h, the detected surface temperature remained as low as 39.0°C, achieving a radiation suppression efficiency of 95.4%. This cascade strategy offers a promising solution for mitigating infrared exposure in high‐temperature and sunlight environments.