Flexible ZrO₂/ZrB₂/C nanofiber felt with enhanced microwave absorption and ultralow thermal conductivity

Carbon-based materials, renowned for their low density, adjustable electrical conductivity, superior corrosion resistance and mechanical properties, and have found extensive applications in the field of electromagnetic wave absorption (EMWA). Despite their merits, the current EMWA and thermal insulation capabilities are not fully optimized, thereby restricting their applications in the aerospace sector. Herein, we introduce a combinatory methodology employing electrospinning followed by pyrolysis to in-situ integrate ZrO₂ and ZrB₂ nanoparticles onto the surface of carbon nanofibers, culminating in a flexible ZrO₂/ZrB₂/C nanofiber felt. The integration of ZrO₂ and ZrB₂ nanoparticles significantly augments impedance matching and promotes multifaceted scattering and interfacial polarization. Consequently, the ZrO₂/ZrB₂/C nanofiber felt demonstrates a minimum reflection loss (RL_min) of −54 dB and the effective absorption bandwidth (EAB, RL ≤ −10 dB) is 3.1 GHz. Moreover, the three-dimensional porous architecture and the presence of multiple heterogeneous interfaces endow the ZrO₂/ZrB₂/C nanofiber felt with an ultralow thermal conductivity of 0.016 W·m⁻¹·K⁻¹ at 1100 ℃, underscoring its exceptional potential for infrared stealth. This work shows considerable guiding significance for the design of bi-functional EMWA materials with ultralow thermal conductivity in aerospace field.