Hollow SiC sphere–embedded mullite fibers for infrared shielding and electromagnetic wave absorption

Multifunctional materials offering high-temperature thermal insulation and electromagnetic wave (EMW) absorption have become a research focus in recent years. Mullite offers excellent thermal insulation; however, it exhibits high infrared transmittance and lacks EMW absorption capability. Silicon carbide (SiC) exhibits infrared-shielding and EMW absorption capabilities but suffers from insufficient stability under long-term high-temperature oxidative exposure. Here, this research designed and fabricated a composite structure by embedding hollow SiC spheres (HSSs) into mullite fibers, aiming to synergistically combine the advantages of both materials. Compared to pure mullite nanofibers, the composite with an HSS content of 30% exhibited 24.4% and 29.3% lower thermal conductivity values at 25 °C and 1000 °C, respectively. The infrared transmittance in the 2.5–8 μm wavelength range decreased from 90% to 32%. Furthermore, at a thickness of 2.0 mm, the composite achieved a minimum reflection loss of −45.37 dB and an effective absorption bandwidth of 4.32 GHz. These improvements originate from synergistic mechanisms enabled by the HSSs. The intrinsic infrared shielding and dielectric loss properties of SiC provide a fundamental performance baseline. Meanwhile, the hollow structure not only hinders solid-phase heat conduction but also enhances infrared attenuation via multiple reflection, scattering, and absorption. Moreover, the introduced heterogeneous interfaces promote interfacial polarization and multiple relaxation processes, which optimize impedance matching and loss capacity, leading to significantly enhanced EMW absorption performance. Overall, this research offers a new approach for designing materials with thermal protection and electromagnetic stealth performance.