Preparation of Cf/Si3N4 composites based on vat photopolymerization combined with precursor infiltration and pyrolysis

Abstract

The development of vat photopolymerization (VPP) 3D printing technology has created the conditions for the fabrication of complex structured Si₃N₄ ceramics. However, Si₃N₄ ceramics produced through VPP often lack sufficient mechanical properties, which limiting their applications. This study introduces short carbon fibers (C_f) into the VPP-Si₃N₄ ceramics, combined with the polymer infiltration and pyrolysis (PIP) process, to prepare C_f/Si₃N₄ composites. The effect of C_f content on slurry preparation, green part printing, and mechanical properties of the C_f/Si₃N₄ composites was systematically investigated. The results indicate that C_f significantly enhances the mechanical properties of C_f/Si₃N₄ composites. At 6 wt.% C_f content, the samples exhibit the highest strength and fracture toughness, reaching 183.2 MPa and 6.2 MPa·m^1/2, respectively, representing increases of 29.7% and 92.3% compared to samples without C_f. The improvement in mechanical properties is partly due to the ‘pinning effect’ of C_f, which enhances interlayer bonding strength in the printed green parts, positively impacting the overall mechanical properties of the composites. Additionally, inherent toughening mechanisms of C_f, such as fiber pull-out, crack deflection, and crack bridging, further enhance the composite's mechanical properties. This study confirms the feasibility of using C_f to enhance the mechanical properties of VPP-Si₃N₄ ceramic.