Electromagnetic interference shielding and mechanical properties of Si^3N4-SiOC composites fabricated by 3D-printing combined with polymer infiltration and pyrolysis

Twinned silicon carbide (SiC) nanowires (NWs) reinforced Si3N4-SiOC composites were successfully fabricated through a joint process of three-dimensional printing (3DP), direct nitridation, and polymer infiltration and pyrolysis (PIP). 3DP and PIP were both addictive manufacturing processes, enabling the near net shape fabrication and microstructure designing of Si3N4-SiOC. With the increase of the PIP cycle number, the pores of Si3N4 were mostly filled with polymer-derived ceramics-silicon oxycarbide (containing SiC NWs and free carbons), which led to the increase of electrical conductivity of Si3N4-SiOC composites. With the increase of SiOC ceramics, the electromagnetic interference shielding effectiveness of Si3N4-SiOC composites increased from 2 dB to 35 dB, in which the absorption shielding effectiveness increased to 27 dB. The flexural strength of Si3N4-SiOC composites reached 63 MPa when the content of SiOC ceramics was 50.1 wt%. It is indicated that Si3N4-SiOC ceramics are a promising electromagnetic shielding and structural material.