Synthesis, electromagnetic reflection loss and oxidation resistance of pyrolytic carbon-Si3N4 ceramics with dense Si3N4 coating

Si3N4-coated porous pyrolytic carbon-Si3N4 ceramics (PyC-Si3N4/Si3N4) were fabricated by chemical vapour infiltration of PyC into porous Si3N4 ceramic and then chemical vapour deposition of Si3N4 coating on the surface of the obtained PyC-Si3N4. The PyC-Si3N4/Si3N4 with 3.1 vol.% PyC content possesses electromagnetic reflection loss as low as −11.5 dB. Due to the excellent sealing effect of dense Si3N4 coating, the PyC-Si3N4/Si3N4 possesses good oxidation resistance, which makes PyC-Si3N4/Si3N4 a good electromagnetic absorbing material that can be used at temperature as high as 1100 °C.