In situ growth of SiCnws in Sc(NO₃)₃ modified polysiloxane-derived SiOC ceramics for enhanced microwave absorbing performance

Oxide ceramic matrix composites (OCMC) have good high-temperature resistance, oxidation resistance, and mechanical properties. However, the microwave absorbing properties of OCMC areinsufficient due to the low dielectric and low loss characteristics of oxide ceramics, so it is urgent to develop a kind of the oxide ceramic matrix with adjustable microstructure and electromagnetic properties. PDC-SiOC ceramics are the optimal oxide ceramics whose component and microstructure can be adjusted by rare earth nitrate modified polysiloxane precursor. For Sc(NO₃)₃ modified PDC-SiOC ceramics, rare earth metals not only can react with siloxy groups to form silicates at high temperatures but also can catalyze the formation of SiCnws. Herein, rare earth nitrate modified polysiloxane precursor was pyrolyzed at 900°C, and then annealing at high temperature to form silicate and SiCnws. After annealing at 1400°C, a large amount SiCnws was in situ formed conductive network structure in SiOC ceramic, so the SiOC ceramic with SiCnws had great electromagnetic wave (EMW) absorbing properties, the maximum effective absorption bandwidth (EAB_max) and the minimum reflection coefficient (RC_min) at the thickness of 2.75 mm reach 4.0 GHz and −42.3 dB in X-band, respectively. By the double-layer impedance matching design, the EAB can be effectively improved, which provide a good way for the design and fabrication of OCMC with advanced (EMW) absorbing properties.