Short-Cut BN Fiber-Toughened Wave-Transparent Si3N4 Ceramics Prepared by Vat Photopolymerization 3D Printing Process

Si 3 N 4 ceramics are widely applied in mechanical and electronic engineering fields owing to their superior high-temperature resistance, strength, and hardness. However, inherent brittleness and high dielectric constant limit their usage in high-temperature wave-transparent devices. To overcome this, BN fibers (BN f , the main component is hBN) with high aspect ratio and mechanical stability were, for the first time, directly incorporated into a Si 3 N 4 matrix via vat photopolymerization 3D printing process as toughening phases, designed to enhance stress transfer and suppress crack propagation. The effects of BN f content, sintering temperature, and holding time on microstructure and properties were systematically investigated. At an optimal condition (1800°C, 4 h, 4 vol% BN f ), the ceramic showed an open porosity of 28.79%, bending strength of 136 ± 9 MPa, fracture toughness of 2.92 MPa·m 1/2 , and dielectric constant of 4.28. This work provides methods and theoretical guidance for the design and manufacture of directly incorporated fiber-toughened high-temperature wave-transparent materials.