Microwave absorbing and mechanical properties of Si–O–C ceramics prepared via preceramic polymer pyrolysis

Abstract To align Si–O–C microwave‐absorbing materials with the trend of structural–functional integration, the Si–O–C ceramics were prepared with polysiloxanes and phenolic resins as raw materials and cross‐linking agents respectively via the polymer‐derived ceramics (PDCs) route. The effects of pyrolysis temperatures on the microstructure, microwave‐absorbing properties, and mechanical properties of the Si–O–C ceramics were investigated. The results show that the complex permittivity and tanδ increase with the increase of the pyrolysis temperature. When the pyrolysis temperature is above 1000°C, tanδ is higher than 0.8, which implies the impedance mismatch. The effective absorption bandwidth (EAB) of the Si–O–C ceramics with a thickness of 3.0 mm covers the whole X ‐band when the pyrolysis temperature is 950°C, and the minimum reflection loss is −17.3 dB at 10.3 GHz. The flexural strength increases and then decreases with the evolution of pyrolysis temperature. When the pyrolysis temperature is 950°C, the flexural strength reaches 37 MPa. Therefore, compared with other pyrolysis temperatures, Si–O–C ceramics have excellent wave‐absorbing and mechanical properties when the pyrolysis temperature is 950°C, which meets the requirement of structure–function integration of wave‐absorbing materials.