Facile Fabrication of Silicone Rubber/Hollow Microsphere/CNTs Foams for Efficient Electromagnetic Wave Absorption and Thermal Insulation

Considering the severity of electromagnetic pollution together with practical requirements in the real world, the development of versatile electromagnetic wave absorbers is imperative. Herein, phenyl silicone rubber/hollow microsphere/CNTs (SR/HM/CNTs) foams were successfully produced via a simple preparation process. Owing to the polarization mechanisms, leakage pathways, and 3D porous structure, SR/HM/CNT foams possess high dielectric loss capability for electromagnetic wave attenuation. Notably, the SR/HM/CNTs foam with 15 wt% filler content exhibits effective absorption across the entire X‐band (8.2–12.4 GHz) with a minimum reflection loss (RL min ) of −37.77 dB at 9.89 GHz. The mechanism of electromagnetic wave absorption shows that strong absorption performance stems from significant conductive loss, multiple attenuation pathways, and favorable impedance matching. Meanwhile, SR/HM/CNTs foams exhibit lightweight (0.301–0.356 g/cm 3 ) and possess low thermal conductivity (0.085–0.136 W·m −l ·K −l ) owing to their closed‐cell structure. The suppressed heat transfer confers infrared stealth, underscoring their potential in defense‐related uses. Overall, this work proposes an easily implemented strategy for constructing multifunctional, high‐performance microwave absorbers.