Fabrication of in-situ Ti-Cx-N1−x phase enhanced porous Si3N4 absorbing composites by gel casting

In view of the lack of a conformal, load-bearing, lightweight, and high-temperature resistant integrated microwave-absorbing composites for applications under extremely complex conditions, this study successfully applies gel casting craft to porous Si3N4 microwave-absorbing composites. The high-temperature decomposition reaction of Ti3SiC2 powder was utilized to generate uniform Ti-Cx-N1−x grains in situ and to enhance the mechanical and microwave-absorption properties of porous Ti-Cx-N1−x/Si3N4 composites. The bending strength, fracture toughness, density, maximum reflection loss value, absorption bandwidth and matched thickness in P-band of the composite with 30 wt% Ti3SiC2 addition were 164.87 ± 7.56 MPa, 2.61 ± 0.13 MPa·m1/2, 2.077 g/cm3, 32.42 dB, 1.74 GHz and 4.2 mm, respectively. The fracture toughness and bending strength of the composite were increased by 71.71% and 58.13%, respectively, compared with monolithic porous Si3N4. The electromagnetic wave loss mechanisms of the composites are proposed as a combination of conductivity loss, multiple reflections and scattering, interfacial polarization and defect polarization.