Abstract: Aerogel with good thermal insulation, high temperature resistance, microwave absorption, and excellent mechanical properties is highly desirable. However, it is difficult to balance mechanical and functional characteristics for traditional silicon-based aerogels. Herein, a novel silicon-based aerogels, composed of SiC skeleton and Si₃N₄ nanowires, were successfully fabricated by using a one-step precursor pyrolysis method. Uniformly distributed Si₃N₄ nanowires within the SiC ceramic skeleton and across the SiC skeleton/Si₃N₄ nanowire composite aerogel (SSA) surface create abundant micro-nano pores, thereby endowing the material with exceptional thermal insulation properties with a room-temperature thermal conductivity of 0.064 W/(m K). Furthermore, SSA possessed excellent thermal insulation performance under both a 650 °C alcohol lamp and a 1300 °C spray gun flame, preserving its structural integrity even when exposed to 1400 °C. Benefiting from the synergistic effect of SiC ceramic skeleton and Si₃N₄ nanowire, SSA has good mechanical performance with a compressive strength up to 17.47 MPa and exhibits effective microwave absorption performance with a strong reflection loss (-50.1 dB) and a wide effective absorption in the full X-Band of 8.2-12.4 GHz. This work provides a simpler and more efficient method and innovative idea for preparing multi-functional thermal insulation aerogel with excellent mechanical strength and superior microwave absorption property.

Key words: Aerogel, Thermal insulation, Mechanical properties, Microwave absorption, SiC skeleton, Si₃N₄ nanowires