Hierarchical porous (Ta_0.2Nb_0.2Ti_0.2Zr_0.2Hf_0.2)C high-entropy ceramics prepared by a self-foaming method for thermal insulation

To meet the emerging demands for thermal protection materials for hypersonic aircraft, developing porous ultrahigh-temperature ceramics with both robust mechanical properties and superior thermal insulation performance is a critical challenge. Herein, we report novel porous (Ta_0.2Nb_0.2Ti_0.2Zr_0.2Hf_0.2)C high-entropy carbide (PHEC) ceramics fabricated by a self-foaming method using commercially available metal chloride and furfuryl alcohol (FA) as precursors. The PHEC ceramics are constructed of microspheres with a size of 2 µm, leading to a high porosity of 91.3% and an interconnected frame. These microspheres consist of high-entropy carbide grains (20 nm), resulting in abundant interfaces and nanosized pores in the PHEC ceramics. Due to its unique hierarchical structure, the prepared PHEC ceramics have outstanding compressive strength (28.1±2 MPa) and exceptionally low thermal conductivity (κ_T, 0.046 W·m⁻¹·K⁻¹) at room temperature. This makes it a promising thermal insulation materials for ultrahigh temperature applications. This work provides a cost-effective and facile strategy for producing porous ultrahigh-temperature ceramics.