Nanostructured Zirconia-Based Aerogels for High-Temperature Thermal Insulation

Zirconia-based aerogels are lightweight, porous materials made up of interconnected zirconia nanoparticles, forming continuous three-dimensional nanoporous networks. Their high melting point, low density, high porosity, and low thermal conductivity make them promising candidates for high-temperature thermal insulation and protection in extreme environments such as spacecraft thermal protection systems, high-speed aircraft, and high-temperature industrial equipment. However, their nanoscale frameworks become unstable at high temperatures. Processes such as nanoparticle sintering, grain coarsening, and temperature-driven phase changes can cause pore collapse, structural damage, and a reduced level of insulation. This Review evaluates zirconia-based aerogels from a failure-mechanism-guided, application-focused perspective. It highlights recent progress in fabrication techniques, nanoscale structural control, and thermal insulation performance with a focus on strategies that enhance phase stability and preserve nanopores. The text reviews strategies like heteroelement doping, structural control, surface and interface modifications, core–shell architectures, and fiber reinforcement, focusing on their impact on sintering resistance, phase evolution, mechanical properties, and heat transfer. It highlights challenges and future opportunities for developing thermally stable zirconia-based aerogels for extreme-environment thermal protection.