Carbon aerogel (CA) has been generally regarded as a potential electromagnetic wave (EMW) absorber, but unsatisfactory microwave absorption, mechanical and anti-oxidation properties are still the primary challenges for its application. Herein, a novel C/SiOC composite aerogel (CSA) was successfully synthesized by a simple copolymerization of dual sols, ambient pressure drying and thermal treatment process for the first time. The morphology and performance of the as-prepared CSA could be tailored just by controlling the initial ratio of silane and phenolic resin (PR) to adjust the content of SiOC in CSA, whose density was in the range of 0.252 to 0.294 g·cm⁻³ with a low thermal conductivity from 0.061 to 0.067 W·m⁻¹·K⁻¹. Notably, the EMW absorption capacity of CSA was greatly enhanced with the increase of SiOC content, with the optimal reflection loss (RL) value of −67.85 dB and effective absorption bandwidth (EAB) of 6.88 GHz, which was dramatically improved than CA (–22.89 dB, 5.34 GHz) and mainly ascribed to the optimized impedance matching characteristics and strong attenuation capacity. Meanwhile, compared with CA (2.63 MPa) with a density of 0.248 g·cm⁻³, the mechanical properties of CSA (3.30–5.12 MPa) were also remarkably improved, and the maximum compression strength was nearly doubled. Furthermore, CSA obtained superior oxidation resistance than CA and exhibited excellent flame-retardant properties. All the results indicated that CSA could be considered as a highly promising candidate for applications in extreme environments due to its lightweight, high strength and outstanding microwave absorption capacity along with good oxidation resistance, superior thermal insulation performance and high flame retardancy.

碳气凝胶（CA）通常被认为是一种潜在的电磁波（EMW）吸收剂，但不理想的微波吸收、机械和抗氧化性能仍然是其应用面临的主要挑战。在此，首次通过双溶胶的简单共聚、常压干燥和热处理工艺成功合成了一种新型 C/SiOC 复合气凝胶 (CSA)。只需控制硅烷和酚醛树脂 (PR) 的初始比例，调节 CSA 中 SiOC 的含量，即可调整所制备的 CSA 的形貌和性能，其密度范围为 0.252 至 0.294 g·cm ^{- 3具有从 0.061 到 0.067 W·m −1} ·K ⁻¹的低导热性. 值得注意的是，CSA的EMW吸收能力随着SiOC含量的增加而大大增强，最佳反射损耗（RL）值为-67.85 dB，有效吸收带宽（EAB）为6.88 GHz，比CA有显着提高（- 22.89 dB，5.34 GHz），主要归功于优化的阻抗匹配特性和强大的衰减能力。同时，与密度为0.248 g·cm ^{−3的CA（2.63 MPa）相比}，CSA的力学性能（3.30-5.12 MPa）也得到了显着改善，最大抗压强度提高了近一倍。此外，CSA 获得了优于 CA 的抗氧化性并表现出优异的阻燃性能。所有结果表明，由于 CSA 具有重量轻、强度高、出色的微波吸收能力以及良好的抗氧化性、优异的隔热性能和高阻燃性，因此可被视为极端环境应用的极有前途的候选者。