Combination of direct ink writing and liquid phase sintering for the rapid fabrication of complex SiC ceramics with high strength

Significant challenges have limited the fabrication of complex SiC structures with high strengths for direct ink writing. Therefore, this study developed a novel SiC ink using Al 2 O 3 and Y 2 O 3 as sintering additives to prepare high-strength, complex SiC structures via a combination of direct ink writing and liquid-phase sintering. The effects of Al 2 O 3 + Y 2 O 3 addition on rheological behaviours of the SiC inks and the resultant microstructures and mechanical properties were systematically investigated. The results revealed that a 45.0 vol % SiC ink with 4.1 wt% Al 2 O 3 + Y 2 O 3 exhibited desirable rheological properties, including a low viscosity of 5.73 Pa s at 50 s −1 and shear yield stress of 325.23 Pa for depositing regulated and precise structures. Using this ink, various complex SiC ceramics were successfully fabricated, achieving a maximum densification of 89.5 ± 0.4 %, bending strength of 134.7 ± 8.3 MPa, and Vickers hardness of 15.66 ± 1.50 GPa after sintering at 1950 °C for 1 h. Conversely, the 45.0 vol% SiC ink with 7.4 wt% Al 2 O 3  + Y 2 O 3 caused nozzle blockages and produced irregularly layered structures with defects. This study offers a new method for the direct ink writing of complex, high-strength SiC ceramics, showing significant potential for applications in various fields.