Synergetic improvement of robustness-oxidation resistance integration with strong microwave absorption in Cf/HfB2-SiC(Hf, rGO) composite PDCs for hypersonic vehicle components

Abstract

High-temperature oxidation resistance and reliability are crucial for thermal protection system (TPS) materials of hypersonic vehicles. Furthermore, the swift development of aerospace industry pushes developments for multi-functional materials to achieve balanced integration in light weight, high strength, thermal insulation/isolation, and electromagnetic (EM) wave absorption. Herein, HfB₂-SiC(Hf_b, rGO) PDCs were fabricated by re-pyrolyzing ball-milling blends of Hf-modified fillers/precursors with 30 wt.% HfB₂. The products with promoted phase compatibility exhibit good mechanical performances, owing to Hf-containing structure like HfOSi. The best combination of fillers/precursors are chosen to construct C_f(x)/SiO₂-HfB₂-SiC(Hf_b, rGO) PDCs to further enhance load bearing capacity. By adjusting the initial C_f length to 2 mm, compressive strength and flexural strength of the material are increased to 264.44 MPa and 83.70 MPa respectively, owing to energy dissipation mechanism including crack deflection, fiber breakage, and fiber pull-out. Notably, the sample maintains stable structure and good mechanical performances after 60 min oxidation under 1300 °C butane torch flame, with hardness of 5.32 GPa and fracture toughness of 4.80 MPa⋅m^1/2. Formation of self-healing HfO₂(HfSiO₄)-SiO₂-B₂O₃ continuous layer timely seals the small cracks and pores left by oxidation of C_f, restrains catastrophic oxidation inside. More interestingly, HfB₂-SiC(Hf_b, rGO) PDCs doped by Co nanopowders exhibit excellent EM wave absorption capacity especially at the thickness of 1.5 mm with the maximum effective absorption bandwidth (EAB_max) of 4.04 GHz (13.04–17.44 GHz) and corresponding minimal reflection loss (RL_min) of −40.03 dB. This work provides a new idea to realize multi-functional application of materials with similar components for TPS in aerospace field.