Preparation of Si3N4f/Si3N4 wave-transparent composites by vat photopolymerization combined with chemical vapor infiltration

The strategic combination of material selection, forming processes, and densification techniques is crucial for optimizing the performance of wave-transparent materials in extreme environments. This study is the first time to prepare Si3N4 f/Si3N4 wave-transparent composites using a combination of vat photopolymerization (VPP) 3D printing and chemical vapor infiltration (CVI) processes. The effects of Si3N4 f content on slurry preparation, green part printing, and final performance were systematically investigated. The addition of Si3N4 f significantly enhanced the toughness of Si3N4 ceramics. Apart from their inherent toughening mechanisms, the "chimeric pinning" effect of the fibers contributes to increased interlayer bonding strength, thereby favorably impacting the mechanical properties. Combining VPP 3D printing and CVI processes resulted in Si3N4 f/Si3N4 composites with a linear shrinkage rate within 1 %, essentially achieving near-net shaping. Additionally, the composites exhibited excellent mechanical and dielectric properties, with a flexural strength of 76.2 MPa, fracture toughness of 4.24 MPa & sdot;m1/2, a dielectric constant of 4, and a dielectric loss tangent of 0.01. This study leverages the high strength and toughness advantages of Si3N4 f and employs VPP 3D printing combined with CVI to achieve the objectives of lightweight, high transmittance, and near-net shaping. It provides theoretical support and experimental validation for designing and manufacturing wave-transparent materials.