In situ growth of one-dimensional nanowires on porous PDC-SiC/Si₃N₄ ceramics with excellent microwave absorption properties

Enhanced microwave absorption properties of porous PDC-SiC/Si₃N₄ ceramics were successfully prepared through in situ growth of Si₃N₄ nanowires (NWs) by the unidirectional freeze casting of Si₃N₄/camphene slurries with various polycarbosilane (PCS) contents at 1400 °C in N₂. Si₃N₄ NWs were in situ formed in the pore channels via a vapor-solid (VS) mechanism, the content of Si₃N₄ NWs increased with increasing of PCS content, which tailored the microstructure and mechanical property of porous PDC-SiC/Si₃N₄ ceramics. With the increase of PCS content, the minimum reflection coefficient (RC) of porous PDC-SiC/Si₃N₄ ceramic decreased from −20.2 dB to −56.2 dB, and the effective absorption bandwidth (EAB) increased from 5.3 to 7 GHz, demonstrating that the porous PDC-SiC/Si₃N₄ ceramics decorated with Si₃N₄ NWs had a superior microwave-absorbing ability, which could be ascribed to the electronic dipole polarization and interfacial scattering enhanced by the various interfaces among Si₃N₄, in-situ formed PDC-SiC nanograins, nanosized carbon and Si₃N₄ NWs phases. These findings provide significance guidance in the development of new broadband EM absorbing materials.