Construction of SiCnws/carbon foam composites with multiple loss mechanisms for excellent electromagnetic wave absorption

Composition optimization and delicate microstructure construction are considered to be critical factors to achieve outstanding electromagnetic (EM) wave absorption performance. SiC nanowires/carbon foam (SiCnws/CF) composites were prepared by the in-situ growth of SiCnws inside carbon foam pores using an internal growth method. After self-foaming of the silicon powder and mesophase pitch mixture, a carbonizing process was adopted subsequently to synthesis SiCnws/CF composites with excellent EM wave absorption performance. With increasing silicon content, the amount of SiCnws generated increases, the distribution of SiCnws becomes uniform, and the diameter decreases continuously. The prepared SiCnws were composed of β-SiC coated with an amorphous Si layer on the surface, which were conducive to the reception of EM wave and impedance matching to free space. Multiple loss mechanisms involving the dipole polarization generated by SiCnws, the interface polarization generated by multi heterogeneous interfaces and the conductive loss provided by CF, which caused high effective energy loss of incident EM wave, hence, improved the EM wave absorption performance significantly. After the addition of silicon, the SiCnws/CF composites obtained excellent impedance matching. When the silicon content was 15 wt %, the prepared SiCnws/CF composite showed the best wave absorption performance, the minimum reflection loss value of the 3.11 mm thick sample was − 55.27 dB, and the effective absorption bandwidth was 2.08 GHz, which provides a new method toward the high-performance EM wave absorbing materials with multiple loss mechanisms.