Ultralight ?-Si3N4w/SiC foam ceramics with superior microwave absorption performance in X- and Ku-bands

Three-dimensional (3D) interconnected hierarchical porous Si3N4w/SiC foam ceramics with high porosity (84.75%) were prepared using foam-gelcasting and an in-situ catalytic nitridation reaction. The effects of Si3N4 whisker content on the pore structures, mechanical properties, dielectric properties, and wave-absorbing properties of these foam ceramics were investigated, and the mechanisms governing pore formation, whisker growth, and wave absorption were thoroughly explored. The increase of Si3N4 whisker content reduced the dielectric loss but improved the absorption performance. The minimum reflection loss value of SC-1.5SN with a thickness of 3.9 mm was -66.49 dB at 9.6 GHz, and the effective absorption bandwidth can cover the entire X-band and Ku-band by adjusting the material thickness. The excellent absorption properties of porous Si3N4w/SiC foam ceramics can be attributed to the absorption loss and interference cancellation. These foam ceramics display great application potential in electromagnetic wave absorption.(c) 2023 Elsevier B.V. All rights reserved.