Polymer-Derived Tantalum Carbide Ceramic Aerogel Monoliths for Ultrahigh-Temperature Thermal Insulation up to 2000 °C

Abstract Ceramic aerogels are ideal thermal insulating materials in the aerospace field because of their low density and low thermal conductivity but are plagued by the limited operating temperature due to the inherently poor high-temperature resistance. In this work, the tantalum carbide (TaC) ceramic aerogel monolith with outstanding ultrahigh temperature stability was successfully prepared through the polymer precursor conversion method combined with the sol–gel technique. Benefiting from the pyrolysis process of the polymer precursor aerogel, the TaC aerogel monoliths with the pearl necklace-like structure were obtained at a low temperature of 1500 °C. The as-prepared TaC aerogels exhibit a low density (0.46–0.63 g/cm3), high Brunauer–Emmett–Teller (BET) specific surface area (95.15–148.17 m2/g), low thermal conductivity (0.046–0.058 W·m–1·K–1), and a good compressive strength (0.043–0.297 MPa). Most importantly, after heat treatment up to 2000 °C under vacuum, the pearl necklace-like structure of the TaC aerogel is well preserved, and the thermal conductivity remains at a low level of 0.059 W·m–1·K–1, indicating the excellent ultrahigh-temperature stability of TaC aerogels. The excellent thermal insulating performance and ultrahigh-temperature stability make the TaC aerogel an attractive material for thermal insulation in extreme conditions.