Wenhu Hong,Shun Dong,Ping Hu,Xiaoguang Luo,Shanyi Du
Enhanced microwave absorption properties of porous PDC-SiC/Si 3 N 4 ceramics were successfully prepared through in situ growth of Si 3 N 4 nanowires (NWs) by the unidirectional freeze casting of Si 3 N 4 /camphene slurries with various polycarbosilane (PCS) contents at 1400 °C in N 2 . Si 3 N 4 NWs were in situ formed in the pore channels via a vapor-solid (VS) mechanism, the content of Si 3 N 4 NWs increased with increasing of PCS content, which tailored the microstructure and mechanical property of porous PDC-SiC/Si 3 N 4 ceramics. With the increase of PCS content, the minimum reflection coefficient (RC) of porous PDC-SiC/Si 3 N 4 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/Si 3 N 4 ceramics decorated with Si 3 N 4 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 Si 3 N 4 , in-situ formed PDC-SiC nanograins, nanosized carbon and Si 3 N 4 NWs phases. These findings provide significance guidance in the development of new broadband EM absorbing materials.
In this work, a novel carbon-enriched SiC by the polymer derived ceramic (PDC-SiC) route was manufactured. By varying the branched chain of the preceramic polymer, the structure and electromagnetic properties of the obtained PDC-SiC ceramics can be effectively altered through carbon enrichment. Specially, PDC-SiC ceramics obtained from branched polysilylacetylene (PSA) constitute a composite material that contains nano-sized SiC grains, carbon nanotubes (CNTs), and silicon carbide nanowires (SiC nw ). Such PDC-SiC ceramics possess a complex three-dimensional network of CNT S /SiC nw , leading to remarkable microwave absorption properties. Notably, the PDC-SiC ceramics processed from dimethyl-polysilylacetylene (D-PSA) achieved a minimum reflection loss (RL min ) of −55.0 dB at 14.4 GHz, and an effective absorption bandwidth (EAB) extends across 5.5 GHz, with a thickness of 2 mm.
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