Bridged polysilsesquioxane‐derived SiOCN ceramic aerogels for microwave absorption

Abstract

AbstractThe development of high‐performance microwave absorption materials in harsh environment is highly desirable but challenging. Herein, lightweight silicon oxycarbonitride (SiOCN) ceramic aerogels were fabricated by the pyrolysis of bridged polysilsesquioxane aerogels, which was presynthesized by a sol–gel method followed by vacuum drying. The structural order and content of free carbon phase determined by pyrolysis temperature play a critical role in modulating the impedance matching and attenuation capacity. The as‐prepared SiOCN aerogel pyrolyzed at 1000°C achieves a minimal reflection loss of −64.2 dB at 8.96 GHz and a broad bandwidth of 5.4 GHz at a low thickness of 2.15 mm. The hierarchical pore structure, abundant heterogeneous amorphous SiOCN/free carbon interfaces, and conductive free carbon phase benefit the superior absorption performance by forming good impedance matching, multiple scattering, interface polarization, and conduction losses. This work provides an insight for the rational design of polymer‐derived ceramic aerogel‐based microwave absorption materials for potential application under extreme conditions such as high‐temperature and oxidation environments.