Self-foaming fabrication of Cf/(HfZrTi)C porous ceramics with integrated thermal insulation, load-bearing and broadband microwave absorption

Aiming at the urgent demand for multifunctional materials integrating thermal protection, stealth performance and load-bearing capacity in the field of next-generation hypersonic aircraft, this study develops a facile, template-free self-expansion foaming route to fabricate carbon fiber-reinforced porous (Hf, Zr, Ti)C medium-entropy ceramics, denoted as C f /(Hf, Zr, Ti)C (HZT). The influence of carbon fiber content (0–10 wt%) on the microstructure, thermophysical properties, mechanical performance, and electromagnetic wave absorption characteristics is systematically investigated. The synergistic mechanism among lattice distortion-induced polarization enhancement, porous structure-mediated multiple scattering, and carbon fiber-constructed conductive networks is elucidated, which effectively breaks the inherent trade-off between thermal insulation, mechanical strength, and microwave absorption in conventional porous ultra-high temperature ceramics. The sample with 6 wt% carbon fiber (HZT-06) possesses a porosity of 70.2% and a low density of 0.67 g/cm 3 . It exhibits a room-temperature thermal conductivity of 0.253 W m −1  K −1 , exceptional broadband microwave absorption with a minimum reflection loss (RLmin) of −59.69 dB and an effective absorption bandwidth (EAB, RL ≤ −10 dB) of 6.32 GHz at a matching thickness of 2.3 mm, and a high compressive strength of 49.62 MPa. This work realizes the multifunctional integration of low thermal conductivity, high load-bearing capacity and strong broadband microwave absorption at room temperature, and provides promising design strategies and fundamental data support for the development of advanced multifunctional thermal protection materials for hypersonic vehicles.