High-strength and low-dielectric porous Si3N4 ceramics prepared by gelcasting using DMAA

Abstract Herein, porous Si3N4 ceramics embracing excellent mechanical and dielectric properties were achieved via gelcasting using N, N-dimethylacrylamide (DMAA) gel system while acting as pore-former. The increase of monomer content (8.0-23.0 wt%) led to an increase in porosity (39.53-43.60%) and pore connectivity, which accelerated vapor phase mass transport and promoted β-Si3N4 grain growth, thereby improving flexural strength (212.33-245.30 MPa) and fracture toughness (3.60-3.89 MPa·m1/2). Attributable to the pores introduced by increasing monomer content, the e′ and tanδ were significantly reduced with the values of 4.18-4.29 to 3.95-4.06 and 1.83-2.38×10-3 to 0.37-1.96×10-3, respectively, demonstrating excellent microwave-transparent properties. This work proved the great application potential of porous Si3N4 ceramics fabricated by gelcasting employing DMAA gel system in the field of microwave-transparent materials.