In-situ synthesis of hierarchically high porosity ZrB₂ ceramics from carbon aerogel template with excellent performance in thermal insulation and light absorption

This work introduces an innovative methodology combining the in-situ boron/carbon thermal reduction (BCTR) reaction and replication carbon aerogel template to synthesize hierarchically high porosity ZrB₂ ceramics. The meticulously designed ceramic liquid-phase precursor ensures higher solubility of solutes while reducing the temperature requisite for boron/carbon thermal reduction. An additional carbon source is incorporated in the precursor to ensure the uniformity of resulting ZrB₂ grains, concurrently maintaining ZrB₂ phase purity. The ultimate prepared ZrB₂ porous ceramics present a uniform microstructure, with grain sizes at the hundred-nanometer scale, and exhibit a hierarchical pore structure. The ZrB₂ porous ceramics exhibited high porosity (85.4–92.9%), low density (0.264–0.482 g/cm³), reasonable compressive strength (0.26–0.51 MPa), low thermal conductivity (0.103–0.212 W/m·K), and efficient light absorption in the range of 400–2000 nm (>94%). The fabricated ZrB₂ porous ceramics hold significant promise for applications in high-temperature insulation and light absorption within elevated-temperature environments.