Preparation, mechanical, dielectric and microwave absorption properties of hierarchical porous SiCnw-Si3N4 composite ceramics

Herein, hierarchical porous SiCnw-Si3N4 composite ceramics with good electromagnetic absorption properties were prepared. A porous Si3N4 matrix with different pore structures was first prepared by gelcasting-pressureless sintering (G-PLS) and gelcasting combined with particle stabilized foam-pressureless sintering (G-PSF-PLS). SiCnw was then introduced by catalytic chemical vapor deposition (CCVD). An increase in solid loading (25-40 vol%) decreased apparent porosity (47.7-41.3%) and improved flexural strength (142.19-240.36 MPa) and fracture toughness (2.25-3.68 MPa.m(1/2)). The addition of foam stabilizer propyl gallate (PG, 0.5-1.0 wt%) significantly increased apparent porosity (73.2-86.4%) and realized large-sized spherical pores, reducing flexural strength (58.23-38.56 MPa) and fracture toughness (0.75-0.41 MPa.m(1/2)). High apparent porosity and large-sized pores facilitated the introduction of SiCnw. The 25 vol% sample exhibited a reflection loss of - 14.67 dB with an effective absorption bandwidth of 3.47 GHz, suggesting a development potential in the electromagnetic wave absorption field.

Automated summary

Here, hierarchical porous SiCnw-Si3N4 composite ceramics with good electromagnetic absorption properties were prepared. The composition and structure of the materials were controlled by adjusting the pore structure and solid loading. The resulting samples exhibited high absorption capability and showed potential for development in the field of electromagnetic wave absorption.