High-performance SiBCN ceramic aerogels with integrated thermal insulation and electromagnetic stealth enabled by divinylbenzene-regulated carbon structure

Developing lightweight materials that displayed excellent thermal stability, strong electromagnetic wave (EMW) absorption performance, and low thermal conductivity was essential to meet the integrated requirements of thermal protection and electromagnetic stealth in hypersonic vehicles. Among the promising candidates, polymer-derived SiBCN ceramic aerogels stood out owing to their low density, exceptional high-temperature stability, and tunable dielectric properties. However, their intrinsic dielectric loss capability remained insufficient, which limited their applications in the field of EMW absorption. To address this issue, a precursor molecular engineering strategy was employed to fabricate SiBCN ceramic aerogels with in-situ sp 2 hybridized carbon networks, wherein divinylbenzene (DVB) was introduced to regulate polyborosilazane (PSNB) at the molecular level. The results demonstrated that the cross-linking effect of DVB strengthened the aerogel skeleton, and the compressive strength of the SiBCN aerogel increased from 0.16 to 0.35 MPa. The well-dispersed carbon nanodomains introduced by DVB effectively optimized the balance between impedance matching and attenuation capability. The optimized SiBCN aerogel, prepared with a Si–H/C=C molar ratio of 1:2, achieved a minimum reflection loss (RL min ) of −53.4 dB and an effective absorption bandwidth (EAB) of 4.14 GHz, while maintaining a low thermal conductivity of 0.055 W m -1  K -1 and a low density of 0.12 g/cm 3 . The study provided an effective approach for the rational design of multifunctional and high-temperature-resistant integrated materials.