Robust and thermostable silicon-based aerogels towards highly efficient thermal insulation and microwave absorption

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.