C_sf/SiBCN Composites Prepared by DIW Combined With PIP Process: Effect of Carbon fiber Content on Mechanical Properties

Direct ink writing (DIW) combined with precursor infiltration and pyrolysis (PIP) method shows the obvious advantage for the fabrication of composites with complex geometries. In this work, the short carbon fiber reinforced silicoboron carbonitride (C_sf/SiBCN) composites were fabricated via DIW combined with the PIP method, and the effects of short carbon fiber content on the printability of slurry, the accuracy of the green bodies, as well as the microstructure and mechanical properties of the composites, were systematically investigated. The results indicate that the C_sf/MA-SiBCN slurry exhibits suitable viscosity (ranging from 10⁴ to 10⁷ Pa·s) and obvious shear-thinning behavior. Furthermore, the incorporation of short carbon fibers effectively mitigates the dimensional shrinkage of the printed C_sf/MA-SiBCN green bodies. Compared with SiBCN ceramics, the C_sf/SiBCN composites show better mechanical properties. With the increase of fiber content, the flexural strength and fracture toughness first increase and then decrease. The C_sf/SiBCN composites with 15 vol% short carbon fiber content exhibit the optimized flexural strength of 155.4 MPa and fracture toughness of 3.85 MPa·m^1/2, which are 52.5% and 133.3% higher than those of the SiBCN ceramics, respectively. This study provides a novel technical fabrication pathway for the low-shrinkage and complex shapes C_sf/SiBCN composites with satisfying mechanical properties.