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/cm(3)), reasonable compressive strength (0.26-0.51 MPa), low thermal conductivity (0.103-0.212 W/m<middle dot>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.