Enhanced 3D printed alumina ceramic cores via impregnation

3D-printed alumina ceramic cores often face the problem of low flexural strength at its application temperature of 1500℃, and the requirements on porosity and strength limit its fabrication process. In this research, three types of solutions were employed to impregnate the ceramics to improve the strength of the 3D-printed alumina ceramic cores. The results showed that silica sol (SS), tetraethyl orthosilicate (TO), and 3-(Trimethoxysilyl)propyl methacrylate (PM) all could improve the (room temperature) flexural strength of the 3D printed ceramics effectively compared to the control sample (CS) without impregnation, and the SS solution could improve the high temperature flexural strength at 1500℃ greatly compared to other solutions. The improvement in strength was due to the introduction of Si, which formed a stable mullite phase during the sintering process. Computed tomography (CT) analysis showed there is no cracks formed in the ceramic cores impregnated with the SS solution, and they exhibited the overall best performance (21.2 ± 0.8 vol% open porosity, shrinkage of 3.2 ± 0.3% in the X direction, 3.4 ± 0.2% in the Y direction, 2.1 ± 0.4% in the Z direction, room temperature flexural strength of 85.7 ± 6.9 MPa, and 1500℃ flexural strength of 19.2 ± 1.1 MPa).