Interface Chemical Welding by Nanoparticles Endow Ceramic Aerogels with Broad‐Temperature Microwave Absorption and Thermal Insulation

Abstract Ceramic aerogels are promising lightweight microwave absorbing materials, but generally face challenges in achieving excellent mechanical properties and robust microwave absorption over a wide temperature range. Herein, an in situ “chemical welding” strategy is proposed, which uses Ti ₂ SnC‐derived TiO ₂ /SnO ₂ composite nanoparticles as “welding agents” to interconnect the SiC/SiO ₂ core‐shell nanofiber network. These nanoparticles construct robust chemical bonding between adjacent fibers to enhance the mechanical properties, achieving a 33% increase in compressive strength and an 88% reduction in plastic deformation after 150 compression cycles. Experimental and theoretical calculations reveal the fundamental differences between chemically‐bonded and physically‐contacted interfaces in regulating microwave absorption. Chemical interfaces exhibit significant advantages in strengthening built‐in electric field, promoting charge separation and carrier transport, and optimizing the temperature response of permittivity. The as‐prepared SiC/SiO ₂ @TiO ₂ /SnO ₂ aerogel with an ultrathin thickness of only 1.8 mm consistently maintains a reflection loss below −20 dB from 298 to 1073 K, outperforming previously reported ceramic aerogels. Additionally, the aerogel exhibits outstanding thermal insulation, showing great potential for infrared stealth. This chemical welding strategy is a general nanotechnology for developing high‐performance aerogels.